WO2013040897A1

WO2013040897A1 - Wafer inspection method and wafer inspection apparatus

Info

Publication number: WO2013040897A1
Application number: PCT/CN2012/074237
Authority: WO
Inventors: 陈鲁
Original assignee: 中国科学院微电子研究所
Priority date: 2011-09-23
Filing date: 2012-04-18
Publication date: 2013-03-28
Also published as: CN103018258B; CN103018258A

Abstract

A wafer inspection method and a wafer inspection apparatus. The method comprises: allowing a grazing incidence of the two paths or more than two paths of coherent beams into a wafer-to-be-tested, forming on the wafer-to-be-tested a light spot having interference fringes; rotating and translating the wafer-to-be-tested, allowing the light spot having the interference fringes to scan the wafer-to-be-tested; particles on a surface of the wafer-to-be-tested scattering the interference fringes, forming a time-related scattered light signal; detecting and processing the scattered light signal, forming frequency-related inspection information, and allowing for acquisition from the inspection information, on the basis of a system-configured parameter and corresponding locations of the particles on the wafer-to-be-tested, of a characteristic frequency signal corresponding to the particle scattering, and for acquisition of distribution and size information of the particles on the wafer-to-be-tested on the basis of the inspection information. The wafer inspection method of the present invention has increased precision and increased throughput, while the wafer inspection apparatus is of reduced difficulty in design and of reduced costs.

Description

Wafer inspection method and wafer inspection device

This application is submitted to the China Patent Office on September 23, 2011, and the application number is 201110286906.0.

The title of the invention is the priority of the Chinese patent application, the disclosure of which is incorporated herein by reference.

Technical field

The present invention relates to the field of semiconductor technology, and in particular, to a wafer inspection method and a wafer inspection apparatus.

Background technique

In semiconductor processes, wafer surface cleanliness is one of the important factors affecting the reliability of semiconductor devices. How to remove contamination and foreign matter particles on the wafer surface has always been a research hotspot in the field of semiconductor technology, and how to detect the cleanliness of the wafer surface after cleaning has become a concern of semiconductor technicians.

The optical inspection method is one of the most commonly used wafer inspection methods because it has the advantage of not cleaning the surface cleanliness of the wafer and real-time detection. The optical detection method uses optical scattering intensity measurement techniques to detect the presence or absence of particles on the surface of the wafer, the spatial distribution of particles on the surface of the wafer, and the like.

Generally, in an optical detecting device, the detecting light emitted by the laser is grazing onto the wafer to be tested, and an elliptical spot is formed on the surface of the wafer, and the elliptical spot is scanned through the rotation and translation of the wafer chuck. The wafer wafer, the detection light is reflected on the surface of the wafer, and if the detection light is projected onto the particle, it is scattered by the particle, and the scattered light beam has a spatial solid angle different from the reflected light beam, and the scattered light is finally detected by the photodetector. Detecting to obtain particle information on the surface of the wafer. Specifically, the elliptical spot on the surface of the wafer is a small-sized spot, usually having a size of 3 μm×9 μm, 5 μm×15 μm, and the wafer. The diameter is 300 mm, so the elliptical spot, such as scanning the entire wafer, takes a long time to detect.

In order to reduce the detection time and increase the throughput of the detection, the prior art also improves the optical wafer inspection method. An optical wafer inspection apparatus is disclosed in US Pat. No. 7,347,752, the wafer inspection apparatus comprising: a light source for emitting detection light; and a beam splitting component for dividing the detection light into a plurality of a light beam, the plurality of light beams are incident on the wafer to be tested to form a plurality of light spots, and the particles located in the light spot scatter the plurality of light beams to form a plurality of scattered light beams carrying the particle information; a plurality of scattered light beams; a plurality of photodetectors for respectively detecting respective scattered light beams; and a processing unit that acquires particle information on the surface of the wafer based on the information of the scattered light beams detected by the plurality of photodetectors.

In the U.S. patent, since a plurality of beams of detection light are used, a plurality of small-sized spots are formed on the surface of the wafer, and each of the small-sized spots has an area of 3 μm×9 μm and 5 μm×15 μm. The small size spot can increase the detection area, which improves the detection efficiency and reduces the detection time. However, the technical solutions of the U.S. patent have many technical problems.

First, the detection accuracy rapidly decreases as the diameter of the particles decreases. The main reason is that the detection signal corresponding to the particles in the prior art is determined by the intensity of the light scattered by the particles as they pass through the spot. Since the intensity of the particle scattering has the following relationship:

T l + cos ² ^ , 2 r, _{4 /} /i ² — l, _{2 /} ii, ₆

¹ = ⁷ ο _ώ2

2R (丁 A ) (^ n― Τ) (-)

+ 2 2

The light intensity is proportional to the diameter of the particle 6th power, and inversely proportional to the fourth power of the detection light wavelength. Therefore, the detection signal for the particle having a diameter of 28 nm or less is weak, and the detection success rate is low. And if you only reduce the wavelength of the detection light (for example, using the deep ultraviolet band), it is not enough to make up for the diameter reduction of the particles. The signal is weakened. Therefore, there is no good technical solution for particle detection under the technology of 28 nm.

Secondly, in order to form a plurality of equally sized spots in the U.S. patent, a Diffractive Optical Element (DOE) must be used in the incident optical path, and the transmission efficiency of the DOE at the ultraviolet wavelength is between 60 and 70%. One-third of the light intensity will be lost. At the same time, DOE brings great complexity and difficulty to the design of the incident light path. The light intensity of each spot is also difficult to maintain, resulting in errors in detection accuracy. Moreover, in order to avoid detection errors, the scattered light intensity in one spot area cannot enter the collected photo-sensing channel of the adjacent spot, which requires that the acquisition optical system cannot be a relatively simple non-imaging system, but must have a high resolution imaging. system. The acquisition optical system must be a large numerical aperture (e.g., a numerical aperture of 0.94 or more). The large numerical aperture and high resolution feature clearly imposes high requirements on the optical portion of the inspection system and also increases production costs.

In addition, since each spot is 3 microns x 9 microns on the wafer, ie the spot size is 3 microns in diameter, at 355 nm, the numerical aperture of the incident light needs to be between 0.11 and 0.12, in numerical aperture. When the DOE is introduced at the same time, the volume of the incident light system will be relatively large, occupying a large space. Due to the limited space, the incident light system imposes a certain limit on the numerical aperture of the daylighting system, which prevents the daylighting system from approaching the surface of the wafer to be tested. While the intensity of the scattering of the particles is mainly concentrated in the solid angle direction close to the grazing angle of the wafer surface, the limited photon numerical aperture will reduce the signal intensity of the particle detection, thereby affecting the detection accuracy.

Summary of the invention

The technical problem to be solved by the present invention is to provide a wafer detecting method and a wafer detecting device to improve detection accuracy. In order to solve the above technical problem, the present invention provides a wafer inspection method, comprising: blasting two or more coherent beams onto a wafer to be tested, and forming a spot with interference fringes on the wafer to be tested; The wafer is rotated and translated to scan the spot with the interference fringes for the wafer to be tested; the particles located on the surface of the wafer to be tested scatter the interference fringes to form a time-dependent scattered light signal; The optical signal is processed to form frequency-dependent detection information, and based on the system setting parameter and the corresponding position of the particle on the wafer to be tested, the characteristic frequency signal corresponding to the particle scattering can be obtained from the detection information; Information, obtaining information on the distribution and/or size of particles on the wafer to be tested.

Optionally, the step of detecting the scattered light signal and processing to form frequency-dependent detection information comprises: forming the scattered light signal into a detection signal in a frequency domain by Fourier transform.

Optionally, the detecting the scattered light signal and processing to form frequency-dependent detection information, and obtaining a particle scattering device from the detection information based on a system setting parameter and a corresponding position of a particle on the wafer to be tested The step of corresponding characteristic frequency signals includes: performing matching calculation of the scattered light signals based on the mixing of the characteristic frequencies to obtain correlation between the scattered light signals and the characteristic frequency corresponding signals. The method comprises: providing a coherent light source; splitting the light emitted by the coherent light source to form two paths or circles.

Optionally, the coherent light source comprises a continuously output laser source or a quasi-continuous output laser source. The step of forming interference fringes on the wafer includes: projecting the two or more coherent beams onto the same position of the wafer to be tested to form completely overlapping spots to form interference fringes.

Optionally, the spot is a spot of a Gaussian light intensity distribution or a spot of a platform type light intensity distribution. Optionally, the light spot is an elliptical spot, and the long axis of the elliptical spot is in the range of 100 to 100 (H 敫 meters, and the short axis is in the range of 15 to 100 μm.

Optionally, the step of rotating and translating the wafer to be tested, so that the interference fringe scans the wafer to be tested comprises: rotating the wafer to be tested at a certain angular velocity, and simultaneously shifting the wafer to be tested in a radial direction, so that the spot is waiting Measuring the radial movement of the wafer, the moving step speed is a radial axis of the short-axis dimension of the spot along the radial direction of the wafer, or 1/2 of the short-axis dimension of the spot along the radial direction of the wafer. Or 1/3 of the short axis dimension of the spot along the radial direction of the wafer or 1/4 of the short axis dimension of the spot along the radial direction of the wafer.

Alternatively, the period of the interference fringes is obtained based on the wavelength of the coherent light beam and the angular velocity of the wafer rotation.

Optionally, the period of the interference fringes is in a range of 50 to 400 nm.

Optionally, the step of detecting the scattered light signal comprises: detecting the scattered light signal at a sampling frequency greater than or equal to 10 MHz.

Optionally, the step of acquiring the distribution information of the particles on the wafer to be tested based on the detection information comprises: obtaining the wafer to be tested based on the presence or absence of a signal corresponding to the characteristic frequency in the detection signal The presence or absence of particles at different locations.

Optionally, the step of acquiring the distribution information of the particles on the wafer to be tested based on the detection information comprises: acquiring a radial position of the particles on the wafer to be tested based on a characteristic frequency of the detection signal.

Optionally, the detection signal includes a signal corresponding to a characteristic frequency, and the detecting is based on the detecting Information, the step of acquiring the distribution information of the particles on the wafer to be tested includes: extracting a signal corresponding to the characteristic frequency in the detection signal, and then converting the extracted signal into a time domain to form a processed particle scattered light signal, The number of fringe periods of the scattered light signal in the time domain is processed, and the light intensity distribution of the spot is combined to obtain the radial position of the particles on the wafer to be tested.

Optionally, the detecting signal includes a signal corresponding to the characteristic frequency, and the step of acquiring the distribution information of the particles on the wafer to be tested based on the detecting information includes: extracting a signal corresponding to the characteristic frequency in the detection signal And then converting the extracted signal into a time-domain forming processed scattered light signal, and based on the moment when the processed scattered light signal appears, combined with the position information of the scanning spot at different times, acquiring the particle on the wafer to be tested Tangential position.

Optionally, the detecting signal includes a signal corresponding to the characteristic frequency, and the step of acquiring the size information of the particle on the wafer to be tested based on the detecting information includes: the step of: based on the detecting signal The strength of the signal corresponding to the characteristic frequency acquires the size or composition of the particles at different positions on the wafer to be tested.

Correspondingly, the present invention further provides a wafer detecting apparatus comprising: a light source for providing coherent light; a beam splitter for splitting the coherent light emitted by the light source to form two or more coherent beams; a translational rotating platform for carrying a wafer to be tested and for translating or rotating the wafer to be tested, the two or more coherent beams forming interference fringes on the wafer to be tested; Detecting scattered light to form a photodetector that scatters light signals, the scattered light being formed by scattering of particles located on the wafer to be tested through the interference fringes; for corresponding particles based on different positions on the wafer to be tested The characteristic frequency, the time-dependent scattered light signal detected by the photodetector is processed to form a frequency-dependent detection information converter; based on the detection information formed by the converter, obtaining the particle on the wafer to be tested Data processing unit for distribution and/or size information. Optionally, the converter performs Fourier transform on the time-dependent scattered light signal detected by the photodetector based on the characteristic frequency to form a detection signal in a frequency domain to obtain a particle on the wafer to be tested. Distribution information.

Optionally, the converter is configured to perform a matching calculation of the mixed frequency of the characteristic frequency on the scattered light signal, obtain a correlation between the scattered light signal and a signal corresponding to the characteristic frequency, to obtain a particle on the wafer to be tested. Distribution information.

Optionally, the data processing unit includes: a first processing unit, where the first processing unit is connected to the converter, configured to obtain, according to the presence or absence of a signal corresponding to the characteristic frequency in the detection signal, whether the wafer to be tested exists Particle information.

Optionally, the data processing unit further includes a second processing unit, the second processing unit is connected to the converter and the first processing unit, when the first processing unit obtains information about the presence of particles on the wafer to be tested And acquiring a radial position of the particle on the wafer to be tested based on a characteristic frequency of the detection signal.

Optionally, the data processing unit further includes a second processing unit, the second processing unit is connected to the converter and the first processing unit, when the first processing unit obtains information about the presence of particles on the wafer to be tested Extracting a signal corresponding to the characteristic frequency in the detection signal, and then converting the extracted signal into a time-domain forming processed scattered light signal, based on the number of fringe periods in the time domain of the processed scattered light signal, combined with the spot Light intensity distribution, obtaining the radial position of the particles on the wafer to be tested.

Optionally, the data processing unit further includes a third processing unit, where the third processing unit is connected to the converter and the first processing unit, when the first processing unit obtains information about the presence of particles on the wafer to be tested Extracting a signal corresponding to the characteristic frequency in the detection signal, and then converting the extracted signal into a time-domain forming processed scattered light signal, based on the moment when the processed scattered light signal appears, combined with the position of the scanning spot at different times Information, obtaining the tangential position of the particles on the wafer to be tested. Optionally, the data processing unit further includes a fourth processing unit, where the fourth processing unit is connected to the converter and the first processing unit, when the first processing unit obtains information about the presence of particles on the wafer to be tested And acquiring a size or a component of a particle at a different position on the wafer to be tested based on a strength of a signal corresponding to the characteristic frequency in the detection signal.

Optionally, a spot adjustment assembly is disposed between the beam splitter and the translational rotation platform, the spot adjustment component for processing the coherent light beam provided by the light source to obtain a platform type spot or a Gaussian spot.

Optionally, the spot is an elliptical spot, and the long axis of the elliptical spot is in the range of ιοο~ιοο (the range of Η敫 meters, and the short axis is in the range of 15 to 100 μm.

Optionally, the photodetector is a high frequency photomultiplier tube.

Optionally, the sampling frequency of the high frequency photomultiplier tube and the data processing unit is greater than or equal to

10MHz.

Optionally, the period of the interference fringes is between 50 and 400 nm.

Compared with the prior art, the present invention has the following advantages:

1. Scanning the wafer to be tested by using a spot with interference fringes, and processing the scattered light signal scattered by the particles on the wafer to be processed based on the characteristic frequency to form frequency-dependent detection information, which can correspond to the characteristic frequency. The detection information is analyzed, and the noise corresponding to other frequencies is filtered, thereby improving the detection accuracy.

2. In an alternative method of the wafer inspection method, the long axis of the elliptical spot is in the range of 100 to 1000 micrometers, and the short axis is in the range of 15 to 100 micrometers, and the elliptical spot is large, which can be greatly Improve detection efficiency. On the other hand, the spot size is large, the numerical aperture of the incident optical path is small, and the space occupied by the incident optical path is small, so that the optical path with a larger numerical aperture can be used for the optical path of the acquisition, thereby increasing the scattered light collected by the collected optical path and increasing Detecting signals High detection accuracy.

3. The diffraction device is not required in the wafer inspection device, thus reducing the design difficulty of the incident optical system.

4. In the optional scheme of the wafer inspection device, the high-frequency photodetector is used for sampling and detection, and the scattered light signal detected by the photodetector at different times can be recorded in detail, thereby improving the detection precision.

5. Through the detection information in the frequency domain, wherein the frequency peak of the detection signal appearing near the characteristic frequency can further accurately obtain the precise radial position of the particle; by extracting the signal corresponding to the characteristic frequency in the detection signal, and then extracting The signal is converted to form a processed scattered light signal in the time domain to obtain an accurate tangential position of the particle. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic flow chart of an embodiment of a wafer detecting method according to the present invention; FIG. 2 is a schematic view showing a first embodiment of a wafer detecting method according to the present invention; 4 is a schematic view of a third embodiment of the wafer detecting method of the present invention; FIG. 5 is a schematic view showing an embodiment of the wafer detecting device of the present invention; FIG. It is a schematic diagram of an embodiment of a data processing unit in the wafer inspection apparatus shown in FIG.

detailed description

Numerous specific details are set forth in the description below in order to provide a thorough understanding of the invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar promotion without departing from the scope of the present invention, and thus the present invention is not limited by the specific implementations disclosed below. System.

The present invention is described in detail with reference to the accompanying drawings, which are illustrated by way of example only, and are not intended to limit the scope of the invention.

In order to solve the problems of the prior art, the present invention provides a wafer inspection method, including: forming two or more coherent light beams; and causing the two or more coherent light beams to be grazing onto the wafer to be tested Forming a spot with interference fringes on the wafer to be tested; rotating and translating the wafer to be tested, scanning the spot with the interference fringe for the wafer to be tested; and the particles located on the surface of the wafer to be tested cause the interference fringe to occur Scattering, forming a time-dependent scattered light signal; detecting and processing the scattered light signal to form frequency-dependent detection information, based on system setting parameters and corresponding positions of particles on the wafer to be tested, from the detection information Obtaining a characteristic frequency signal corresponding to particle scattering; and acquiring distribution information of particles on the wafer to be tested based on the detection information.

The invention scans the wafer to be tested by using interference fringes, and the scattered light signal scattered by the particles on the wafer to be processed is processed based on the characteristic frequency to form frequency-related detection information, so that the detection information corresponding to the characteristic frequency can be generated. The analysis is performed, and the noise corresponding to other frequencies is filtered, thereby improving the detection accuracy.

Referring to FIG. 1, a schematic flow chart of an embodiment of a wafer inspection method of the present invention is shown. The crystal circle detecting method generally includes the following steps:

Step S1, forming two or more coherent light beams;

Step S2, causing the two or more coherent beams to be grazing onto the wafer to be tested, and forming a spot with interference fringes on the wafer to be tested;

Step S3, the wafer to be tested is rotated and translated, so that the spot with interference fringes is scanned for the wafer to be tested;

Step S4, the particles located on the surface of the wafer to be tested scatter the interference fringes to form a time-dependent scattered light signal; Step S5, detecting the scattered light signal and performing processing to form frequency-related detection information, and based on the system setting parameter and the corresponding position of the particle on the wafer to be tested, the feature corresponding to the particle scattering can be obtained from the detection information. Frequency signal

Step S6: Acquire, according to the detection information, information about distribution and/or size of particles on the wafer to be tested.

The individual steps are described in detail below.

Step S1 is performed. The step S1 generally includes the following sub-steps: providing a coherent light source, wherein the coherent light source can emit light with better coherence. Specifically, the coherent light source includes a continuously output laser source or quasi-continuous The output laser source.

The light emitted by the light source is split to form two or more coherent light beams.

Step S2 is performed to immerse the two or more coherent beams into the wafer to be tested, and form a spot with interference fringes on the wafer to be tested. In order to more accurately detect the particles on the wafer to be tested, preferably, the two or more coherent beams are grazing onto the wafer to be tested to form a clear spot.

For example, the clear-cut spot may be a spot of a Gaussian intensity distribution or a spot of a platform-type light intensity distribution. Here, in the spot of the platform-type light intensity distribution, the internal light intensity is consistent, and the external light intensity is very Weak, can be ignored. Specifically, the spot of the Gaussian light intensity distribution can be formed by laser projection onto the wafer. The spot of the platform type light intensity distribution can be obtained by filtering the light beam by an aspherical lens focusing or a gradual pupil.

The coherent light beam is projected onto the wafer to be tested by grazing incidence, and a spot having interference fringes is formed. The two or more coherent beams completely overlap the spots on the wafer to be tested, and interference occurs at the positions of the overlapping spots to form interference fringes.

Specifically, the phase angle between the coherent beams may be 180 degrees, that is, the coherent beams may be projected on the wafer to be tested in opposite directions, and the phase angle between the coherent beams may be smaller than 90 degrees, that is to say, the coherent light beam is incident at a certain angle from the same direction, which is not limited in the present invention.

The angle between the two or more coherent beams and the wafer to be tested can adjust the intensity and period of the interference fringes. Specifically, the light intensity I of the interference fringes is:

I = 2I _X (l + cos(—— sin θ)

λ

The period d of the pattern is:

Where is the angle between the coherent beam and the normal to the wafer to be tested (here the angle between the two coherent beams and the wafer to be tested is the same). :^ is the intensity of the two coherent beams (where the intensity of the two coherent beams is the same), X is the distance between the source and the spot of the coherent beam, and λ is the wavelength of the coherent beam.

Specifically, if the incident angle of the coherent light beam is 80 degrees and the wavelength is 355 nm, the period of the interference fringe formed is 180 nm. For technical generations below 28 nm, the particle diameter on the wafer to be tested is much smaller than the 180 nm. It should be noted that the present invention does not limit the period of the interference fringe. Generally, the period of the interference fringe is in the range of 50 to 400 nm based on the commonly used wavelength and the angle of the incident angle.

Specifically, the coherent light beam is projected onto the wafer to be tested in a grazing incidence manner. Preferably, the incident angle on the wafer to be tested is 70. Left and right, an elliptical spot is formed on the surface of the wafer to be tested, and the ratio of the long and short axes of the elliptical spot is 3:1. The long axis of the elliptical spot may be in the range of 100 to 1000 microns by the adjustment of the spot adjustment component, and the short axis of the elliptical spot may be in the range of 15 to 100 microns.

The spot formed by the embodiment has a large spot size, and the detection efficiency can be greatly improved. On the other hand, the spot size is large, the numerical aperture of the incident optical path is small, and the space occupied by the incident optical path is small, so that the optical path with a larger numerical aperture can be used for the optical path of the acquisition, thereby increasing the scattered light collected by the collected optical path and increasing The detection signal improves the detection accuracy.

Step S3 is performed, and the spot is not moved, and the spot to be tested is rotated and translated to make the spot be treated. A spiral scan is performed on the wafer to complete the inspection of the entire wafer to be tested.

For example, the wafer to be tested is rotated at a certain angular velocity (for example, 30 rpm to 1000 rpm) from the center of the circle, and is simultaneously stepwise translated along the radial direction of the wafer to be tested, and 360-degree rotation is performed at each step position. The spot completes the scan of the wafer to be tested.

It should be noted that, in order to perform relatively accurate and detailed detection of the wafer to be tested, the wafer to be tested is radially translated in a small step, specifically, the moving step speed is one rotation per revolution. Moving the short axis dimension of the spot along the radial direction of the wafer, or 1/2 of the short axis dimension of the spot along the radial direction of the wafer, or 1/3 of the short axis dimension of the spot along the radial direction of the wafer or The spot is 1/4 of the minor axis dimension along the radial direction of the wafer.

It should be noted that before the wafer inspection, the coherent light beam of the interference appropriate wavelength is selected for optical detection in combination with the rotational angular velocity of the wafer.

In step S4, during the rotation and translation of the wafer to be tested, if there are particles on the wafer to be tested, the particles will pass through the spot, and specifically, the particles sequentially scatter through the interference fringes in the spot to form scattered light.

Step S5 is performed to detect and process the scattered light signal to form frequency-dependent detection information, and based on the system setting parameter and the corresponding position of the particle on the wafer to be tested, the particle scattering corresponding to the detection information can be obtained. Characteristic frequency signal.

Specifically, the scattered light is collected and detected by a photodetector at a certain frequency to form a time-dependent scattered light signal. In order to improve the measurement accuracy, preferably, the photodetector is a high frequency photomultiplier tube.

Specifically, the frequency of the photomultiplier tube sampling is greater than or equal to 10 MHz. Preferably, the sampling frequency of the photomultiplier tube is greater than or equal to 100 MHz, and sampling and detecting by a high-frequency photodetector can be recorded in detail. The scattered light signal detected by the photodetector at different times, and then High detection accuracy.

The scattered light signal detected by the photodetector at different times is recorded throughout the period in which the spot is scanned for the wafer to be tested. Since the position of the wafer to be tested for rotation and translation is related to the time, correspondingly, the scattered light signals at different times are recorded, and the scattered light signals corresponding to different positions of the wafer to be tested can be obtained.

Specifically, the time-dependent scattered light signal data described herein refers to the intensity (e.g., light intensity) of the scattered light signal, the time at which the scattered light signal appears, the time during which the scattered light signal lasts, and the like. It should be noted that since the diameter of the short axis of the spot (15~100 microns) is only about 1/1500 of the radius of the wafer (100 ~ 150 mm), the spot on the wafer to be tested can be seen as a point. And the moving line can be approximated as a linear motion when the particles pass through the spot, so as to accurately calculate the trajectory of the particles in the spot.

Taking the spot of the platform-type light intensity distribution as an example, the particles do not have a coherent light beam to illuminate the particles before entering the spot, and the scattered light signal is zero. When the particles enter the spot, the coherent beam will scatter on the particles, and the scattered light signal is S. Since the interference fringes in the plate type spot change periodically, the scattered light signal S also changes periodically. However, when the particles leave the spot, the scattered light signal is again zero.

It should be noted that the light spot may also be a Gaussian light spot distributed according to a Gaussian intensity, which is not limited in the present invention.

In practical applications, the scattered light can be collected using a high frequency photomultiplier tube to form a time-dependent scattered light signal.

Assuming that the particles pass through the spot, due to the formation of periodically varying interference fringes in the spot, the spot will pass through the interference fringes to form a scattered light signal having a certain frequency. Specifically, the distance between the spot and the center of the wafer to be tested is d mm, and the angular velocity of the wafer to be tested is (degrees per second), and the scattered light signal The frequency of the number is:

2 2πά

- ^J —x ,

360 χ ₀

Among them, χ. It is the period of interference fringes.

Since the angular velocity and the period of the interference fringe are system setting values, if there is a particle located at a distance d from the center of the wafer to be tested, a scattered light signal of a frequency is formed. Here will

360 χ ₀

The frequency is the characteristic frequency corresponding to the particles at different positions (here, the position mainly refers to the radial direction of the wafer to be tested).

Specifically, when. It is 180 nm, is 100 degrees per second, and when d is 200 mm, the characteristic frequency of the scattered light signal formed by particle scattering is 1.938 MHz.

Based on the characteristic that the scattered light signal has a characteristic frequency, the actual scattered light signal collected by the high-frequency photomultiplier tube is converted into the frequency domain based on the characteristic frequency to form frequency-dependent detection information. Since the signal corresponding to the characteristic frequency is stronger after the characteristic frequency is converted to the frequency domain, and the signal corresponding to the other frequency is very weak, it can help to filter out noise (for example, a noise signal formed on the rough surface of the wafer to be tested, photoelectric The sensor's own noise signal, etc., and the analysis of the signal related to the characteristic frequency can obtain more accurate analysis results.

Specifically, the scattered light signal may be Fourier transformed based on a characteristic frequency corresponding to particles at different positions on the wafer to be tested to form a detection signal in the frequency domain. However, the present invention is not limited thereto, and the correlation between the scattered optical signal and the characteristic frequency corresponding signal may be obtained by performing matching calculation of the scattered optical signal based on the mixing of the characteristic frequencies, so as to be related to the characteristic frequency. The signal is analyzed.

The following is an example in which a Fourier transform is used to form a detection signal in the frequency domain. Specifically, photomultiplier The scattered light signal detected by the tube is a signal in the time domain (the abscissa is time), and after the Fourier transform is performed on the scattered light signal, a detection signal in the frequency domain (the abscissa is the frequency) is formed.

Step S6 is performed to acquire distribution information of the particles on the wafer to be tested based on the detection signal. Specifically, the distribution information of the particles herein includes: the presence or absence of particles on the wafer to be tested, the position of the particles, the size of the particles, the composition of the particles, and the like.

Based on the presence or absence of a signal corresponding to the characteristic frequency in the detection signal, it is possible to obtain the presence or absence of particles in the spot range. Specifically, the spot is located at a position dl from the center of the wafer to be tested, and a signal of a frequency of ^x^^ is not detected in the detected signal, indicating a distance from the wafer to be tested.

The 360 x ₀ heart does not have particles at the dl position. If the signal of the ^ frequency is measured in the detection signal,

360 x ₀ indicates that there is a particle at the dl position from the center of the wafer to be tested.

In addition, since the characteristic frequency is proportional to the distance between the particles and the center of the wafer to be tested, the radial position of the particles on the wafer to be tested can be obtained based on the difference in the characteristic frequency of the detection signal, for example, the detection signal includes ^x^"frequency signal in radial direction at a distance dl from the center of the wafer to be tested

There are particles at the position of 360 x ₀ ; if the detection signal includes the signal of the frequency, at the distance from the wafer to be tested

The 360 x ₀ has a particle at a radial position of d2.

In the above embodiment, the spot is regarded as a point on the wafer to be tested, and based on the difference in the characteristic frequency, the distance of the particles in the spot from the center of the wafer to be tested is obtained, thereby obtaining the radial position of the particles. Specifically, after determining the presence of particles on the wafer to be tested, the detection signal is processed, only the signal corresponding to the characteristic frequency is extracted, and the extracted signal is converted, and converted into a processed scattering in the time domain. Optical signal. Since only the signal corresponding to the characteristic frequency is extracted, the signal corresponding to the noise Filtering is performed, and the processed scattered light signal can be analyzed to obtain more accurate detection results.

Since the present embodiment converts the scattered optical signal into the frequency domain to form a detection signal by Fourier transform in step S5, correspondingly, the inverse Fourier transform is used when converting the extracted signal. The extracted signal is converted from the frequency domain to the time domain to form a processed scattered light signal. Referring to Figures 2 through 4, an embodiment of processing the backscattered light signal in step S6 of Figure 1 is shown, respectively. It should be noted that the normally processed scattered light signal includes thousands of cycles, and here, in order to make the attached figure clearer, only a few cycles are exemplified.

As shown in Fig. 2, before the time, the particles 101 have not passed through the spot 102, and the intensity of the scattered light signal 103 is zero. At time t!, the particle 101 starts to enter the spot 102 and moves along the center position of the spot 102, thereby forming a scattered light signal 103 of a certain light intensity, and for the wafer to be tested of the technology below 28 nm, on the wafer to be tested The particle diameter is much smaller than the period of the interference fringe (for example, 180 nm). When the particles pass through the interference fringes between the light and dark phases, the scattered light signal 103 is also periodically changed. As shown in FIG. 2, the scattered light signal 103 is shown. Including five cycles, until time t ₂ , after the particles 101 leave the spot 102, the scattered light signal is zero and there is no change.

As shown in Fig. 3, unlike the embodiment shown in Fig. 2, although the particles 201 also enter the spot 202 at the moment, the particles 201 move along the edge position of the spot 202, so that the trajectory of the spot 202 through which the particles 201 pass. It is relatively short, and accordingly, the number of interference fringes passed is small, and thus the scattered light signal 203 is also periodically changed, but the scattered light signal 203 is shown to include only three periods, until the time t ₂ , the particles After leaving the spot 202, the scattered light signal 203 is zero and there is no change.

It can be seen that the processed scattered light signal 203 corresponding to the particles 201 at different radial positions within the spot 202 has a different number of cycles, and the radial distribution of the particles in the spot 202 can be obtained based on the number of cycles. As shown in FIG. 4, the difference from the embodiment shown in FIG. 2 is that the first particles 3011 and the second particles 3012 pass through the spot 302, t! moment, the first particles 3011 start to enter the spot 302, and t2 is the second time. 3012 particles entered spot 302, t ₃ start time of the first particles away from spot 3011 302, t ₄ time starts to leave the second spot 302 3012 particles. Between the times t ₂ and t ₃ , since the first particles 3011 and the second particles 3012 are relatively close, and the wafer to be tested is rotated at a certain speed, the first particles 3011 and the second particles detected by the photomultiplier tube are caused. The corresponding scattered light signals 303 of 3012 overlap each other. Therefore, the minimum value of the periodic scattered light signal 303 between t2 and t3 is not zero. The scattered light signal 303 between t2 and t3 in this embodiment is more than the number of cycles of the scattered light signal 203 shown in FIG.

It can be seen that the processed signals corresponding to the different tangential positions of the spot 202 have different starting moments, and the distribution of the multi-particles located in the spot 303 can be measured based on the difference of the starting time. High precision.

Specifically, due to the angular velocity of the wafer to be tested and the distance from the center of the wafer to be tested, it can be known that the tangential position of the particles on the wafer to be tested can be obtained based on the time at which the processed scattered light signal appears. Assuming that the angular velocity of the wafer to be tested is ^ and the distance from the center of the wafer to be tested is d, the circumferential distance between the first particle 3011 and the starting timing position is .d^, and the first particle 3011 and the second particle 3012 are The circumferential distance is cH t to obtain a tangential position of the particles on the wafer to be tested.

Since the intensity of the scattered light signal is proportional to the size of the particle, the size of the particle in the spot range can be obtained based on the intensity of the processed scattered light signal.

In addition, since the material of the particles on the wafer to be tested is usually silicon dioxide, organic matter, silicon, or metal, particles of different materials have different scattering rates for the coherent light beam, and the scattered light signals of silicon dioxide and silicon (metal) have The difference in the order of magnitude, therefore, can also distinguish the different light intensities of the detection signals, and obtain the materials of the corresponding particles based on the ranges of different light intensities.

It should be noted that when analyzing the size of the particles, it is necessary to compare the particles based on the same material. Correspondingly, the present invention further provides a detecting device for a wafer to be tested. Referring to FIG. 5 and FIG. 6 respectively, a side view and a partial top view of an embodiment of the wafer detecting device to be tested according to the present invention are shown. The wafer detecting device to be tested includes: a light source 10, a beam splitter 9, a translation rotating platform 2, a photodetector 6, a converter 7, and a data processing unit 8. among them,

Light source 10, a light source for providing coherent light, which may be a continuously outputting laser source or a quasi-continuous output laser source in order to provide better coherent light. In this embodiment, the light source 10 is typically a laser, such as a short wavelength solid state laser having a wavelength of 355 nm. The light source 10 can also be other parallel collimated light sources, which are not limited in the present invention.

The beam splitter 9 is configured to split the coherent light emitted by the light source 10 to form two or more coherent light beams. In this embodiment, the beam splitter 9 splits the light emitted by the light source 10 into two paths. Coherent beam.

Preferably, in order to form a clear-cut spot, the present invention also provides a spot adjusting component 3 between the beam splitter 9 and the translational rotating platform 2, and the two coherent beams split by the beam splitter 9 are adjusted to form a platform. In the present embodiment, the spot adjusting component 3 may be a composite lens, an aspherical lens, or a binary optical lens, which is not limited in the present invention. Specifically, the spot adjusting component 3 adjusts the coherent light beams by using different lenses to form mutually overlapping spots on the wafer 1 to be tested.

The translation rotary platform 2 is configured to carry the wafer 1 to be tested, and the coherent light beam is projected onto the wafer 1 to be tested to form a light spot, and the light spot may be a spot of a platform-type light intensity distribution or a light spot of a Gaussian light intensity distribution. This is not a limitation.

Specifically, the coherent light beam is projected onto the wafer 1 to be tested at a grazing incidence of an incident angle of 70 degrees, and the two coherent light beams form a completely overlapping elliptical spot on the wafer 1 to be tested, the elliptical spot being interference fringes. Spot. Specifically, the elliptical spot has a major axis in the range of 100 to 1000 micrometers and a minor axis in the range of 15 to 100 micrometers. The period of the interference fringes is between 50 and 400 nm, far Greater than the diameter of the particles.

Thereby, the particles can form a periodically varying scattered light signal when passing through the light-dark interphase interference fringes. Particles 5 located in the spot range scatter the interference fringes to form scattered light. The translational rotating platform 2 rotates and translates the wafer 1 to be tested on the translational rotating platform 2 by rotating, translating, etc., thereby enabling the interference fringes to scan the entire surface of the wafer 1 to be tested.

Preferably, in order to improve the measurement accuracy, it is necessary to reduce the stepping of the translational rotary table 2. Specifically, the wafer to be tested is rotated at a certain angular velocity (for example, 30 rpm to 100 rpm), and the wafer to be tested is translated in the radial direction to move the spot along the radial direction of the wafer to be tested, and the moving step speed is per rotation. Radially moving the short-axis dimension of the spot along the radial direction of the wafer, or 1/2 of the short-axis dimension of the spot along the radial direction of the wafer, or 1 of the short-axis dimension of the spot along the radial direction of the wafer /3 or 1/4 of the short axis dimension of the spot along the radial direction of the wafer. .

In order to make the spatial layout of the wafer detecting device to be tested in the present invention more compact, in the embodiment, the direction of the scattered light is changed by the retroreflective component 4, so that the scattered light is reflected to the detecting surface of the photodetector 6 located above the translational rotating platform 2. However, the present invention is not limited thereto, and other lighting components may be used according to design requirements to reflect scattered light onto the detecting surface of the photodetector 6.

Photodetector 6 is used to detect scattered light at a certain frequency to form a time-dependent scattered light signal. The time-dependent scattered light signals described herein include the intensity of the scattered light signal (e.g., light intensity), the time at which the scattered light signal occurs, the time at which the scattered light signal lasts, and the like.

In order to obtain a time-dependent scattered light signal, preferably, the present invention employs a high frequency (reaction time between 0.1 ns and 10 ns) photodetector 6 (for example, a photomultiplier tube), specifically, the photodetector The sampling frequency of 6 is greater than or equal to 10 MHz. Preferably, the sampling frequency of the photodetector 6 is greater than or equal to 100 MHz. The high-frequency photodetector 6 detects the scattered light at a relatively high frequency, and obtains time information in which the scattered light signal is more detailed.

a converter 7 for using a characteristic frequency corresponding to particles at different positions on the wafer 1 to be tested The time-dependent scattered light signal detected by the photodetector 6 is processed to form frequency-dependent detection information.

Specifically, the converter 7 can perform Fourier transform on the time-dependent scattered light signal detected by the photodetector 6 based on the characteristic frequency corresponding to the particles at different positions on the wafer 1 to be tested, and form a frequency domain. The detection signal is used to obtain the distribution information of the particles on the wafer 1 to be tested. The converter 7 can also be configured to perform a matching calculation of the mixed frequency of the characteristic frequency on the scattered light signal, and obtain a correlation between the scattered light signal and the characteristic frequency corresponding signal to obtain the particle 5 in the wafer to be tested 1 Distribution information on.

Since the characteristic frequency of the scattered light signal of the particle at a position different from the center of the circle is known, the signal corresponding to the characteristic frequency can be extracted and analyzed in the detection signal in the frequency domain, and the noise signal corresponding to the other frequency is filtered out. (For example, a noise signal formed by a rough surface of the wafer 1 to be tested, a noise signal of the photosensor itself, etc.), thereby improving detection accuracy.

The wafer detecting device to be tested according to the present invention further comprises a data processing unit 8. Referring to FIG. 7, a schematic diagram of an embodiment of the data processing unit in the wafer detecting device to be tested shown in FIG. 5 is shown. The data processing unit 8 is connected to the converter 7 and the translational rotation platform 2 for obtaining the crystal to be measured according to the detection signal obtained by the converter 7 and simultaneously combining the translation and rotation information of the wafer 1 to be tested on the translational rotating platform 2. The position of the surface 1 of the circle 1 is obtained, thereby obtaining the distribution of the particles 5 on the surface of the wafer 1 to be tested.

Specifically, the data processing unit 8 includes a first processing unit 81, a second processing unit 82, a third processing unit 83, and a fourth processing unit 84, where

The first processing unit 81 is connected to the converter 7 for obtaining information on whether or not particles are present on the wafer 1 to be tested according to the presence or absence of a signal corresponding to the characteristic frequency among the detection signals obtained by the converter 7.

The second processing unit 82 is connected to the converter 7 and the first processing unit 81, and when the first processing unit 81 obtains the information of the particles on the wafer 1 to be tested, extracts the detection signal corresponding to the characteristic frequency. a signal, which is then converted into a time-domain to form a processed scattered light signal, After the processing, the number of fringe periods of the scattered light signal in the time domain is combined with the light intensity distribution of the spot to obtain the radial position of the particles 5 on the wafer 1 to be tested.

The third processing unit 83 is connected to the converter 7 and the first processing unit 81. When the first processing unit 81 obtains the information of the particles on the wafer 1 to be tested, the signal corresponding to the characteristic frequency in the detection signal is extracted. And then converting the extracted signal into a time-domain forming processed scattered light signal, and based on the moment when the processed scattered light signal appears, combined with the position information of the scanning spot at different times, acquiring the particle 5 on the wafer 1 to be tested Tangential position.

The fourth processing unit 84 is connected to the converter 7 and the first processing unit 81. When the first processing unit 81 obtains the information of the particles on the wafer 1 to be tested, it is based on the detection signal corresponding to the characteristic frequency. The strength of the signal, the size or composition of the particles at different positions on the wafer to be tested, and the size or composition of the particles 5 at different positions on the wafer 1 to be tested.

In order to improve the detection accuracy, preferably, the sampling frequency of the data processing unit 8 is greater than or equal to 10 MHz.

It should be noted that, in the foregoing embodiment, only some functions of the data processing unit 8 are disclosed, but the present invention is not limited thereto, and those skilled in the art may also modify, replace, and modify the above embodiments.

In addition, one skilled in the art can select one or more of the first processing unit 81, the second processing unit 82, the third processing unit 83, and the fourth processing unit 84 in the data processing unit shown in FIG. 7 according to their own needs. The data processing unit is composed of the present invention, and the present invention does not limit this.

In the wafer detecting device to be tested provided by the present invention, in addition, in the direction of detecting the optical path, the imaging system is not required to collect the scattered light, and the detecting optical path system is compressed, and the cost is also reduced.

Further, in the wafer detecting device to be tested of the present invention, it is not necessary to use the diffractive optical device, thereby reducing the design difficulty of the incident optical system and reducing the cost.

On the other hand, the spot formed by the invention is large, and the detection throughput is improved, which can greatly improve the inspection. Measuring efficiency, in addition, the spot size is large, the numerical aperture of the incident optical path is small, and the space occupied by the incident optical path is small, so that the optical path of the collecting optical path can adopt an optical system with a large numerical aperture, thereby increasing the scattered light collected by the collecting optical path, thereby increasing The large detection signal improves the detection accuracy.

Although the invention has been disclosed above in the preferred embodiments, the invention is not limited thereto. Any changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be determined by the scope defined by the claims.

Claims

Rights request

A wafer inspection method, comprising:

Having two or more coherent beams grazing onto the wafer to be tested, and forming a spot with interference fringes on the wafer to be tested;

The wafer to be tested is rotated and translated to scan the wafer with interference fringes for the wafer to be tested; the particles located on the surface of the wafer to be tested scatter the interference fringes to form a time-dependent scattered light signal;

Detecting and processing the scattered light signal to form frequency-dependent detection information, and based on the system setting parameter and the corresponding position of the particle on the wafer to be tested, the characteristic frequency signal corresponding to the particle scattering can be obtained from the detection information;

Based on the detection information, information on the distribution and/or size of the particles on the wafer to be tested is obtained.

2. The wafer inspection method according to claim 1, wherein the detecting the scattered light signal and performing processing to form frequency-related detection information comprises: performing the Fourier transform to The scattered light signal forms a detection signal in the frequency domain.

3. The wafer inspection method according to claim 1, wherein said detecting said scattered light signal and processing comprises forming frequency-dependent detection information based on system setting parameters and particles on a wafer to be tested. Correspondingly, the step of obtaining the characteristic frequency signal corresponding to the particle scattering from the detection information comprises: performing matching calculation of the scattered light signal based on the mixing of the characteristic frequency, and obtaining the scattered light signal corresponding to the characteristic frequency Signal correlation.

4. The wafer inspection method according to claim 1, wherein the step of grazing the two or more coherent beams onto the wafer to be tested comprises:

Providing a coherent light source; Splitting light emitted by the coherent light source to form two or more coherent beams;

The wafer detecting method according to claim 4, wherein the coherent light source comprises a laser light source that is continuously outputted or a laser light source that is quasi-continuously output.

The wafer detecting method according to claim 1, wherein the two or more coherent beams are grazing onto the wafer to be tested, and interference fringes are formed on the wafer to be tested. The steps include:

The two or more coherent beams are projected to the same position of the wafer to be tested to form completely overlapping spots to form interference fringes.

The wafer detecting method according to claim 6, wherein the spot is a spot of Gaussian intensity distribution or a spot of a platform type light intensity distribution.

The wafer detecting method according to claim 7, wherein the spot is an elliptical spot, the long axis of the elliptical spot is in the range of 100 to 1000 micrometers, and the short axis is 15 to 100 micrometers. In the range.

9. The wafer inspection method according to claim 6, wherein the step of rotating and translating the wafer to be tested, and causing the interference fringe to scan the wafer to be tested comprises: rotating the wafer to be tested at a certain angular velocity, Simultaneously, the wafer to be tested is translated in the radial direction to move the spot along the radial direction of the wafer to be tested, and the moving step speed is a short axis dimension of the spot along the radial direction of the wafer, or the said 1/2 of the minor axis dimension of the spot along the radial direction of the wafer, or 1/3 of the minor axis dimension of the spot along the radial direction of the wafer or 1/4 of the minor axis dimension of the spot along the radial direction of the wafer.

The wafer detecting method according to claim 1, wherein the step of grazing two or more coherent beams onto the wafer to be tested comprises: selecting interference by combining wafer angular velocity

The wafer detecting method according to claim 10, wherein the period of the interference fringe is

In the range of 50~400nm.

The wafer detecting method according to claim 1, wherein the detecting the scattered light signal comprises: detecting the scattered light signal at a sampling frequency greater than or equal to 10 MHz.

The wafer detecting method according to claim 2, wherein the step of acquiring the distribution information of the particles on the wafer to be tested based on the detection information comprises the steps of: based on the The presence or absence of a signal corresponding to the characteristic frequency acquires the presence or absence of particles at different positions on the wafer to be tested.

The wafer detecting method according to claim 13, wherein the step of acquiring distribution information of particles on the wafer to be tested based on the detection information comprises: a characteristic frequency appearing based on the detection signal Obtain the radial position of the particles on the wafer to be tested.

The wafer detection method according to claim 13, wherein the detection signal includes a signal corresponding to a characteristic frequency, and the obtaining, according to the detection information, information about distribution of particles on a wafer to be tested The step of: extracting a signal corresponding to the characteristic frequency in the detection signal, and then converting the extracted signal to a processed particle scattered light signal in the time domain, based on the number of fringe periods in the time domain of the processed scattered light signal Combining the light intensity distribution of the spot to obtain the radial position of the particles on the wafer to be tested.

The wafer detection method according to claim 13, wherein the detection signal includes a signal corresponding to a characteristic frequency, and the obtaining, according to the detection information, information about distribution of particles on a wafer to be tested The step of: extracting a signal corresponding to the characteristic frequency in the detection signal, and then converting the extracted signal into a time domain to form a processed scattered light signal, based on the processed scattered light At the moment when the signal appears, combined with the position information of the scanning spot at different times, the tangential position of the particles on the wafer to be tested is obtained.

The wafer detection method according to claim 13, wherein the detection signal includes a signal corresponding to a characteristic frequency, and the obtaining, based on the detection information, size information of a particle on a wafer to be tested The step of including the step of: acquiring the size or composition of the particles at different positions on the wafer to be tested based on the strength of the signal corresponding to the characteristic frequency in the detection signal.

18. A wafer inspection apparatus, comprising:

a light source for providing coherent light;

a beam splitter for splitting coherent light from a light source to form two or more coherent beams;

a translational rotating platform for carrying a wafer to be tested and for translating or rotating the wafer to be tested, the two or more coherent beams forming a spot with interference fringes on the wafer to be tested; a photodetector for detecting scattered light at a certain frequency to form a scattered light signal, wherein the scattered light is formed by scattering of particles located on the wafer to be tested through the interference fringes;

A converter for processing a time-dependent scattered light signal detected by the photodetector to form a frequency-dependent detection information based on a characteristic frequency corresponding to the particles at different positions on the wafer to be tested;

A data processing unit that obtains distribution and/or size information of the particles on the wafer to be tested based on the detection information formed by the converter.

The wafer inspection apparatus according to claim 18, wherein the converter performs Fourier transform on the time-dependent scattered light signal detected by the photodetector based on the characteristic frequency to form a frequency The detection signal in the domain to obtain the distribution information of the particles on the wafer to be tested. The wafer detecting device according to claim 18, wherein the converter is configured to perform a matching calculation of the mixed frequency of the characteristic frequency on the scattered light signal, and obtain a correlation between a scattered light signal and a characteristic frequency corresponding signal. Sex, to obtain the distribution information of the particles on the wafer to be tested.

The wafer inspection apparatus according to claim 19, wherein the data processing unit comprises: a first processing unit, the first processing unit is coupled to the converter, and configured to correspond to the characteristic frequency according to the detection signal The presence or absence of the signal obtains information on whether or not particles are present on the wafer to be tested.

The wafer inspection apparatus according to claim 21, wherein said data processing unit further comprises a second processing unit, said second processing unit being coupled to said converter and said first processing unit, in said first processing When the unit obtains the information of the particles present on the wafer to be tested, the radial position of the particles on the wafer to be tested is obtained based on the characteristic frequency of the detection signal.

The wafer inspection apparatus according to claim 21, wherein said data processing unit further comprises a second processing unit, said second processing unit being coupled to said converter and said first processing unit, in said first processing When the unit obtains the information of the particles present on the wafer to be tested, extracts a signal corresponding to the characteristic frequency in the detection signal, and then converts the extracted signal into a time domain to form a processed scattered light signal, based on the processed scattered light signal. The number of fringe periods in the time domain, combined with the light intensity distribution of the spot, obtains the radial position of the particles on the wafer to be tested.

The wafer inspection apparatus according to claim 21, wherein said data processing unit further comprises a third processing unit, said third processing unit being coupled to said converter and said first processing unit, in said first processing When the unit obtains the information of the particles present on the wafer to be tested, extracts a signal corresponding to the characteristic frequency in the detection signal, and then converts the extracted signal into a time domain to form a processed scattered light signal, based on the processed scattered light signal. At the moment of occurrence, combined with the position information of the scanning spot at different times, the tangential position of the particles on the wafer to be tested is obtained. The wafer inspection apparatus according to claim 21, wherein said data processing unit further comprises a fourth processing unit, said fourth processing unit being coupled to said converter and said first processing unit, in said first processing When the unit obtains the information of the particles present on the wafer to be tested, based on the strength of the signal corresponding to the characteristic frequency in the detection signal, the size or composition of the particles at different positions on the wafer to be tested is obtained.

A wafer inspection apparatus according to claim 18, further comprising a spot adjustment assembly between the beam splitter and the translational rotation stage, the spot adjustment component for processing the coherent light beam provided by the light source Platform type spot or Gaussian spot.

The wafer inspection apparatus according to claim 18, wherein said spot is an elliptical spot, said elliptical spot having a major axis in the range of 100 to 1000 μm and a minor axis in the range of 15 to 100 μm. Inside.

The wafer inspection apparatus according to claim 18, wherein said photodetector is a high frequency photomultiplier tube.

The wafer inspection apparatus according to claim 28, wherein the sampling frequency of the high frequency photomultiplier tube and the data processing unit is greater than or equal to 10 MHz.

The wafer inspection apparatus according to claim 18, wherein the period of the interference fringes is between 50 and 400 nm.