US20030207651A1

US20030207651A1 - Polishing endpoint detecting method, device for detecting a polishing endpoint of a polishing process and chemical-mechanical polishing apparatus comprising the same

Info

Publication number: US20030207651A1
Application number: US10/389,911
Authority: US
Inventors: Seung-Kon Kim; Yong -Rim Ko
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2002-05-06
Filing date: 2003-03-18
Publication date: 2003-11-06
Also published as: KR20030086655A

Abstract

A polishing endpoint detecting device of a polishing apparatus detects a polishing endpoint of a polishing process by measuring light reflected from a surface of a semiconductor substrate being polished. The apparatus also includes a polishing pad and a rotary plate each of a light-transmitting material. The light is directed onto the surface of the semiconductor substrate through the polishing pad and the rotary plate and is scanned across the surface of the semiconductor substrate along a horizontal line which passes through the centers of the polishing pad and the semiconductor substrate. A light-measuring instrument measures a characteristic of the light reflected from the surface of the semiconductor substrate, and a processor detects the polishing endpoint by analyzing signals produced by the light measuring instrument.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a chemical-mechanical polishing process in which a film formed on a semiconductor substrate is planarized. More particularly, the present invention relates to a device using light for detecting an endpoint of the chemical-mechanical polishing process.

2. Description of the Related Art

Recently, in an effort to meet consumer demand, advances in technology for manufacturing semiconductor devices have been developed to enhance the integration density, reliability, and response speed, etc., of the devices. Generally, a semiconductor device is manufactured by forming a film on a semiconductor substrate, such as a silicon wafer, and patterning the film to form a pattern having a required electric property.

The pattern is formed by means of sequential or repeated unit processes including deposition, photolithography, etching, ion implantation, polishing, cleaning, and drying processes. Among these unit processes, polishing is key in attaining a high degree of integration, and structural and electrical reliability of the semiconductor device. In the chemical-mechanical polishing process, a film on a semiconductor substrate is mainly planarized by a chemical reaction between a slurry and the film formed on the semiconductor substrate and by mechanical friction between the film on the semiconductor substrate and a polishing pad of a chemical-mechanical polishing (CMP) apparatus.

In addition to the polishing pad, the CMP apparatus generally includes a rotating table atop which the polishing pad is attached, a polishing head for holding and rotating a semiconductor substrate, a slurry supplying device for supplying slurry between the polishing pad and the semiconductor substrate, and a pad conditioner for improving the surface condition of the polishing pad. The CMP apparatus further includes a polishing endpoint detecting device for determining the endpoint of the chemical-mechanical polishing process, i.e., the point at which the polishing process should be stopped.

The conventional polishing endpoint detecting device measures variables related to the surface condition of the semiconductor substrate, and detects the polishing endpoint when the variables change abruptly. For example, in the case in which an insulation film or a dielectric film on semiconductor substrate is polished in order to expose a metal layer formed beneath the insulation film or the dielectric film, the temperature of the semiconductor substrate, the coefficient of friction, or a characteristic of light reflected from the polished surface of the semiconductor substrate changes abruptly once the metal layer is exposed. The polishing endpoint detecting device is thus used to determine the polishing endpoint by detecting an abrupt change in these variables.

Polishing endpoint detecting devices are disclosed in U.S. Pat. No. 5,893,796 (issued to Birang et al.), U.S. Pat. No. 6,045,439 (issued to Birang et al.), and U.S. Pat. No. 6,280,290 (issued to Birang et al.). These polishing endpoint detecting devices include a platen having a hole, a polishing pad having a transparent window, and a laser interferometer for detecting the polishing endpoint. Also, a method for forming the transparent window is disclosed. Furthermore, U.S. Pat. No. 6,247,998 (issued to Wiswesser, et al.) discloses a CMP apparatus having a platen for supporting a polishing pad, a polishing head for holding a semiconductor substrate, a first optical system for directing a first light onto a surface of a semiconductor substrate and for measuring the light reflected from the semiconductor substrate in order to generate a first interference signal, and a second optical system for directing a second light onto the surface of the semiconductor substrate and for measuring the light reflected from the substrate in order to generate a second interference signal.

FIGS. 1 and 2 illustrate a

conventional CMP apparatus

100 having a polishing endpoint detecting device. Referring FIG. 1, the conventional CMP apparatus 100 includes a rotational table 110 to which a polishing pad 102 is attached, a polishing head 120, a pad conditioner 122 for improving the surface condition of the polishing pad 102, and a slurry supplying member 124 for supplying a slurry 124 a between a semiconductor substrate 10 and the polishing pad 102. The polishing head 120 holds the semiconductor substrate 10 so that a surface 10 a of the semiconductor substrate 10 to be polished faces the polishing pad 102. In addition, the polishing head 120 places the surface 10 a of the semiconductor substrate 10 to be polished in contact with the polishing pad 102.

The rotational table 110 has a rotary plate 112 to which the polishing pad 102 is attached, a base plate 116 coupled to a rotary shaft 126, and a sidewall 114 disposed between the rotary plate 112 and the base plate 116. The rotational table 110 thus has the overall shape of a disc, wherein the sidewall 114 extends along the outer peripheral edges of the rotary plate 112 and the base plate 1 1-6.

A polishing

endpoint detecting device

130 for detecting the polishing endpoint of the chemical-mechanical polishing process is installed in a space defined by the rotary plate 112, the side wall 114 and the base plate 116. The polishing endpoint detecting device 130 includes a light source 134 for generating a beam of light 132 a, a splitter 136 for directing the light 132 a generated by the light source 134 onto the surface 10 a of the semiconductor substrate 10 being polished, a light measuring instrument 138 for measuring a characteristic of the light 132 c reflected from the surface 10 a of the semiconductor substrate 10, and a processor 140 for detecting the polishing endpoint by analyzing the signals produced by the light measuring instrument 138.

Furthermore, the

rotary plate

112 has a hole 112 a therethrough, and the polishing pad 102 has a transparent window 104 at a location corresponding to the hole 112 a. The light 132 b is directed by the splitter 136 onto the surface 10 a of the semiconductor substrate 10 being polished through the hole 112 a and the transparent window 104. The light 132 c reflected from the semiconductor substrate 10 passes back through the window 104 and hole 112 a to the light measuring instrument 138. The light measuring instrument 138 measures the interference of the light 132 c reflected from the semiconductor substrate 10 or the flux of the reflected light 132 c that is dependent on a reflection ratio of the semiconductor substrate 10.

However, a gap exists between the

surface

10 a of the semiconductor substrate 10 and the transparent window 104 of the polishing pad 102. The slurry 124 a supplied onto the polishing pad 102 and a by-product of the polishing process accumulate in this gap between the surface 10 a of the semiconductor substrate 10 and the transparent window 104. The accumulated slurry 124 a and by-product disperse the light directed onto the face 10 a of the semiconductor substrate 10 being polished. The amount of this dispersed light is proportional to the amounts of the slurry 124 a and the by-product that have accumulated between the surface 10 a of the semiconductor substrate 10 and the transparent window 104. The dispersed light affects the reading given by the light measuring instrument 138, whereby the polishing endpoint can not be properly determined.

Referring now to FIGS. 1 and 2, the

light

132 b applied to the surface 10 a of the semiconductor substrate 10 is focused on a predetermined portion 10 b of the semiconductor substrate 10. However, different portions of the semiconductor substrate 10 may be polished at different rates. Thus, when the polishing endpoint is established using measurements taken at only a portion 10 b of the semiconductor substrate 10, other portions of the semiconductor substrate 10 may be over- or under-polished.

Meanwhile, the

polishing pad

102 is attached to the rotary plate 112 using an adhesive. When the polishing pad 102 is replaced, the polishing pad 102 must be attached to the plate 112 so that the transparent window 104 of the polishing pad 102 is aligned exactly with the hole 112 a in the rotary plate 112. This alignment process requires a significant amount of time even when the polishing pad is replaced by a highly skilled technician. Accordingly, replacing the polishing pad 102 in a conventional CMP apparatus detracts significantly from the efficiency at which the chemical-mechanical polishing process can be carried out.

SUMMARY OF THE INVENTION

Objects of the present invention are to overcome above-mentioned problems of the prior art.

Thus, for instance, a first object of the present invention is to provide a polishing endpoint detecting device and a method of detecting a polishing endpoint which can be used to measure the amount by which the entire surface of a semiconductor substrate is polished.

Another object of the present invention is to provide a CMP apparatus having a polishing endpoint detecting apparatus which analyzes light reflected from the semiconductor substrate to detect a polishing endpoint, and in which the polishing pad thereof can be changed in a short amount of time.

According to one aspect of the present invention, a polishing endpoint detecting device comprises a light source for producing a beam of light, a light path changing means for scanning the light horizontally across the surface of the semiconductor substrate, and a light measuring instrument that measures a characteristic of the light reflected from the surface of the substrate. A processor detects a polishing endpoint by analyzing signals produced by the light measuring instrument.

According to another aspect of the present invention, a CMP apparatus comprises a rotational table including a rotary plate consisting of a light-transmitting material, a polishing pad attached to the rotary plate and also consisting of a light-transmitting material, a polishing head for holding a semiconductor substrate such that a surface of the semiconductor substrate to be polished faces the polishing pad and is pressed into contact with the polishing pad, and a polishing endpoint detecting device. The polishing endpoint detecting device includes a light source for producing a beam of light, a light measuring instrument for producing signals indicative of a characteristic of the light reflected from the surface, and a processor for detecting a polishing endpoint of the semiconductor substrate by analyzing the signals produced by the light measuring instrument. Also, as per above, the polishing endpoint detecting device preferably also includes a light path changing means for scanning the light horizontally across the surface of the semiconductor substrate along a line that passes through the center of rotation of the polishing pad.

The rotational table may also include a base plate disposed below the rotary plate and having a shape corresponding to that the rotary plate, a sidewall extending along and between the outer peripheral edges of the base plate and the rotary plate, and a rotary shaft connected to the base plate. In this case, the light source, the light measuring instrument and the light path changing means are disposed within the rotational table as supported by the base plate. The processor is connected to the light measuring instrument through the rotary shaft.

The light path changing means may comprise a reflective splitter, i.e., a mirror, for directing the light onto the surface of the substrate, and a driving means for rotating the splitter so that the light scans the surface. Alternatively, the light path changing means may comprise a supporting member that supports the light source and the light measuring instrument, and driving means for moving the supporting member reciprocally along a straight direction so that the light from the light source scans the surface of the substrate.

According to an aspect the present invention as described above, during the polishing process while the surface of the substrate is being pressed against the polishing pad and the polishing pad is being rotated relative to the surface of the substrate, the light path changing means changes scans the light emanating from the light source along a horizontal line across the surface of the semiconductor substrate. Preferably, this horizontal line passes through a center of rotation of the rotary plate and polishing pad and/or through the center of the surface of the substrate being polished. The light measuring instrument produces signals representative of a characteristic of the light reflecting from the surface of the substrate, and the processor detects a polishing endpoint by analyzing the signals produced from the light measuring instrument. Because the amount(s) by which the entire surface of the substrate is polished can be measured in this way, the semiconductor substrate can be prevented from being over-polished or under-polished.

In addition, the present invention does away with the need for a transparent window in the polishing pad because the rotary plate and polishing pad are made of light-transmitting materials. Therefore, the polishing pad can be changed in a relatively short amount of time. Furthermore, the polishing endpoint is detected with a high degree of reliability because little of the slurry or by-product of the polishing process accumulates between the polishing pad and the semiconductor substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments thereof made with reference to the accompanying drawings, of which: [0025]
FIG. 1 is a schematic cross-sectional view of a conventional CMP apparatus; [0026]
FIG. 2 is an enlarged plan view of the CMP apparatus shown in FIG. 1; [0027]
FIG. 3 is a schematic cross-sectional view of a CMP apparatus having a first embodiment of a polishing endpoint detecting device according to the present invention; [0028]
FIG. 4 is an enlarged plan view of the CMP apparatus shown in FIG. 3; [0029]
FIG. 5 is a detailed cross-sectional view of the splitter of the polishing endpoint detecting device of the apparatus shown in FIG. 3; [0030]
FIG. 6 is a side view of the splitter and the light measuring instrument of the polishing endpoint detecting device of the apparatus shown in FIG. 3; [0031]
FIG. 7 is a schematic cross-sectional view of a CMP apparatus having a second embodiment of a polishing endpoint detecting device according to the present invention; [0032]
FIG. 8 is a schematic cross-sectional view of a CMP apparatus having a third embodiment of a polishing endpoint detecting device according to the present invention; [0033]
FIG. 9 is a schematic cross-sectional view of a CMP apparatus having a fourth embodiment of a polishing endpoint detecting device according to the present invention; [0034]
FIG. 10 is a schematic cross-sectional view of a CMP apparatus having a fifth embodiment of a polishing endpoint detecting device according to the present invention; [0035]
FIG. 11 is a schematic cross-sectional view of another CMP apparatus comprising the first embodiment of the polishing endpoint detecting device according to the present invention; [0036]
FIG. 12 is an enlarged plan view showing the CMP apparatus shown in FIG. 11; [0037]
FIG. 13 is a schematic cross-sectional view of another CMP apparatus comprising the second embodiment of the polishing endpoint detecting device according to the present invention; and [0038]
FIG. 14 is a schematic cross-sectional view of another CMP apparatus comprising the third embodiment of the polishing endpoint detecting device according to of the present invention. [0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail hereinafter, with reference to the attached drawings. [0040]
FIGS. [0041] 3-6 illustrate a first embodiment of a CMP apparatus 200 according to the present invention. Referring first to FIG. 3, a polishing head 220 holds a semiconductor substrate 10 so that a surface 10 a of the semiconductor substrate 10 to be polished faces a polishing pad 202. The polishing head 220 also urges the semiconductor substrate 10 into contact with a polishing pad 202 during the polishing of the semiconductor substrate 10. More specifically, the polishing head 220 exerts suction on the backside of the semiconductor substrate 10 and moves up and down. In addition, the polishing head 220 rotates in a state in which the semiconductor substrate 10 contacts the polishing pad 202 in order to effect a uniform polishing of the semiconductor substrate 10. In this case, the polishing pad 202 is made of a light-transmitting (transparent) material such as polyurethane. In the figure, reference numeral 224 designates a slurry supplying member that dispenses slurry 224 a onto the polishing pad 202 and hence, between the pad 202 and the substrate 10. Reference numeral 222 designates a polishing pad surface conditioner.
A [0042] rotary plate 212 in the shape of a disc is made of a transparent material and in particular, a plastic such as an acrylic acid resin. The polishing pad 202 is adhered to an upper surface of the rotary plate 212. The rotary plate 212 is coupled to a rotary shaft 226 that rotates the rotary plate 212.
A polishing [0043] endpoint detecting device 230 for detecting the polishing endpoint is installed under the rotary plate 212. The polishing endpoint detecting device 230 includes a light source 234 for generating a beam of light 232 a, such as an infrared laser beam, a light path changing unit 240 for changing the path of the light 232 a emanating from the light source 234, a light measuring instrument 236 for measuring a characteristic of the light 232 c reflected from the surface 10 a of the semiconductor substrate 10 being polished, and a processor 250 for detecting the polishing endpoint by analyzing signals produced by the light measuring instrument 236.
The light [0044] path changing unit 240 includes a splitter 242, and a motor 244 for rotating the splitter 242 so that the light 232 b scans the surface 10 a of the semiconductor substrate 10 being polished. To this end, the splitter 242 and the motor 244 are coupled to each other by means of a timing belt 246 and a pair of driving pulleys 248 a and 248 b. In this embodiment, the motor 244 is a step motor by which the rotational angle of the output shaft thereof can be precisely controlled. A controller 252 connected to the motor 244 controls the angular velocity and angle of rotation of the motor 244.
Referring now to FIGS. 3, 4 and [0045] 5, the splitter 242 is rotated by the motor 244 to change the path of the light 232 b emanating from the light source 234 such that the light scans the surface 10 a of the semiconductor substrate 10 along a horizontal line 260 which passes through the center of the polishing pad 202. In FIGS. 4 and 5, arrows represent the direction along which the incident light 232 b scans the surface 10 a of the semiconductor substrate 10. In this case, the horizontal line 260 also passes through the center of the semiconductor substrate 10. The movement of the point of the incident light 232 b along the surface 10 a of the semiconductor substrate 10, and the rotation of semiconductor substrate 10 by the polishing head 220 thus allow the entire surface 10 a of the semiconductor substrate 10 to be analyzed.
As best shown in FIG. 5, the optical receptor of the [0046] light measuring instrument 236 has a surface area that is larger than the area (in the same plane) onto which the light 232 c can be reflected from the surface 10 a of the semiconductor substrate 10, given the entire range of incident angles possible with the splitter 242. In the first embodiment of the present invention, the light measuring instrument 236 can be movable in this plane along with the point of the scanned and reflected light 232 c even though the effective surface area of the light measuring instrument 236 is large enough to receive the light 232 c when the instrument is still.
In the meantime, the [0047] light source 234 and the light measuring instrument 236 are connected to the processor 250 that controls the generation of the light and analyzes the signals output by the light measuring instrument 236 to detect the polishing endpoint. In this case, the processor 250 can detect the polishing endpoint by analyzing the intensity (flux) of the light 232 c reflected from the surface 10 a of the semiconductor substrate 10. For example, the CMP process may be used to planarize an insulation film formed over a metal film on the semiconductor substrate 10. In this case, when the metal film is exposed during the polishing of the insulation film, the intensity of the reflected light 232 c measured by the light measuring instrument 236 abruptly changes because the reflection ratio of the metal film (ratio of reflected light to absorbed light) is different from that of the insulation film. The processor 250 perceives the time at which the intensity of the reflected light 232 c abruptly changes as the polishing endpoint of the chemical-mechanical polishing process. On the other hand, the processor 250 can detect the polishing endpoint from the interference pattern of the reflected light 232 c. In this case, the reflected light 232 c includes (first) light reflected from the insulation film and (second) light reflected from the metal film. The processor 250 detects the polishing endpoint based on the phase difference between the first reflected light and the second reflected light.
Furthermore, the [0048] processor 250 determines the amount of polishing that has been carried out on respective portions of the semiconductor substrate 10 by correlating the signals provided by the light measuring instrument 236 with information concerning the angular velocity and relative rotational position of the splitter 242. A display 254 connected to the processor 250 shows these results of the analysis of the signals provided by the light measuring instrument 236. Although not shown in FIGS. 3, 4 and 5, the controller 252 not only controls the splitter 242 but also the angular velocity of the rotary plate 212, the angular velocity of the polishing head 220, and the pressure created between the semiconductor substrate 10 and the polishing pad 202. In addition, the controller 252 controls the flow rate of the slurry 224 a issuing from the slurry supplying member 224 and the operation of the pad conditioner 222 for improving the surface condition of the polishing pad 202.
Furthermore, if the [0049] light measuring instrument 236 were positioned directly under the splitter 242, the light 232 c reflected from the semiconductor substrate 10 would impinge the splitter 242. To prevent such problems, as shown in FIG. 6, the plane of the reflecting surface of the splitter 242 subtends a predetermined angle with respect to the horizontal, and the light measuring instrument 236 is spaced laterally from the splitter 242 by a corresponding amount.
According to the first embodiment of the present invention, light [0050] 232 b is directed onto the surface 10 a of the semiconductor substrate 10 through the transparent rotary plate 212 and polishing pad 202. The light 232 b is also scanned across the surface 10 a of the semiconductor substrate 10 by the splitter 242. The light 232 b scanning the surface 10 a of the semiconductor substrate 10 is reflected from the surface 10 a onto the light measuring instrument 236. Therefore, all portions of the surface 10 a of the semiconductor substrate 10 being polished can be analyzed to prevent them from being over-polished or under-polished. Also, the amount that any portion of the semiconductor substrate 10 has been polished can be determined regardless of the rotational speed of the rotary plate 212 and polishing pad 202 because the plate 212 and the polishing pad 202 are made of light-transmitting materials. Furthermore, the amount of slurry 224 a or by-product that accumulates between the surface 10 a of the semiconductor substrate 10 and the polishing pad 202 is relatively low because there is no gap therebetween corresponding to the gap that exists between a substrate and the transparent window of the conventional polishing pad. Hence, the polishing endpoint detection process is more reliable than in the prior art. Still further, very little time is required for changing the polishing pad 202 because the rotary plate 212 and the polishing pad 202 are both made entirely of light-transmitting material, i.e., do not have to be rotationally aligned relative to one another.
FIG. 7 is shows a [0051] CMP apparatus 300 having another polishing endpoint detecting device 330 according to the present invention. The CMP apparatus 300 also includes a rotary plate 312 of a transparent material such as an acrylic acid resin, and a polishing pad 302 of a light-transmitting material attached to the rotary plate 312. The polishing endpoint detecting device includes a light source 334 and a light measuring instrument 336 disposed under the rotary plate 312. The light source 334 directs a beam of light 332 a onto a surface 10 a of a semiconductor substrate 10 being polished. The light 232 a impinges the surface 10 a at a predetermined incident angle after the light 332 a has passed through the plate 312 and the polishing pad 302. The light measuring instrument 336 measures a characteristic of the light 332 b reflected from the surface 10 a of the semiconductor substrate 10.
A [0052] scanning mechanism 340 supports the light source 334 and the light measuring instrument 336. The scanning mechanism 340 is also operative to scan the incident light 332 a over the surface 10 a of the semiconductor substrate 10 along a horizontal line passing through the center of the polishing pad 302. The scanning mechanism 340 includes a supporting member 342 for supporting the light source 334 and the light measuring instrument 336, and a pneumatic cylinder 344 for reciprocally moving the supporting member 342 in a straight line. When the pneumatic cylinder 344 moves the supporting member 342, the point where the light 332 a from the light source 334 impinges the surface 10 a of the semiconductor substrate 10 moves along the aforementioned horizontal line passing through the center of the polishing pad 312.
A [0053] processor 350 is connected to the light source 334 and the light measuring instrument 336, and a controller 352 is connected to the pneumatic cylinder 344. Although a pneumatic cylinder 344 is shown in FIG. 7 as the means for reciprocally moving the supporting member 342, other linear reciprocal driving mechanisms can be employed. Also, although the controller 352 and the pneumatic cylinder 344 are shown as being directly connected, the controller 352 can further include a direction control valve for controlling the flow of compressed air to and from the cylinder 344 and a flow rate control valve for controlling the flow rate of the compressed air. Otherwise, the functions of the processor 350, the controller 352 and the display 354 are identical to those of the first embodiment.
According to the second embodiment of the present invention, the light [0054] 332 a directed onto the surface 10 a of the semiconductor substrate 10 being polished scans the surface 10 a of the semiconductor substrate 10 in accordance with the extension and retraction of the pneumatic cylinder 334. The light 332 b reflected from the surface 10 a of the semiconductor substrate 10 is measured by the light measuring instrument 336. Therefore, all of the polished portions of the surface 10 a of the semiconductor substrate 10 can be analyzed. Such an analysis can be used to prevent the over-polishing or the under-polishing of the surface 10 a. Also, the amounts by which all of the portions of the semiconductor substrate 10 have been polished can be measured regardless of the angular velocity of the rotary plate 312 and the polishing pad 302 because the plate 312 and the polishing pad 302 each comprise light-transmitting material.
FIG. 8 shows a [0055] CMP apparatus 400 having a third embodiment of a polishing endpoint detecting device 430 according to the present invention. Referring to FIG. 8, a polishing pad 402 of a light-transmitting material (same as first embodiment) is attached to a transparent rotary plate 412. A light source 434, a splitter 436 and a light measuring instrument 438 are disposed under the rotary plate 412. The light source 434 emits a beam of light 432 a, and the splitter 436 changes the path of the emitted light 432 a so that the light 432 a is directed onto the surface 10 a of the semiconductor substrate 10 being polished. The light measuring instrument 438 measures a characteristic of the light 432 c reflected from the surface 10 a of the semiconductor substrate 10.
A light [0056] path changing device 440 is operative to scan the light 432 b from the splitter 436 across the surface 10 a of the semiconductor substrate 10 along a horizontal line 260 (see FIG. 4) passing through the center of the polishing pad 402. The light path changing device 440 includes a supporting member 442 supporting the light source 434, the splitter 436 and the light measuring instrument 438, and a pneumatic cylinder 444 for reciprocally moving the supporting member 442 in a straight line. The pneumatic cylinder 444 moves the supporting member 442 so that the point of light 432 b impinging on the surface 10 a of the semiconductor substrate 10 moves along a horizontal line passing through the center of the polishing pad 402 and the center of the semiconductor substrate 10. A processor 450 is connected to the light source 434 and the light measuring instrument 438, and a controller 452 is connected to the pneumatic cylinder 444.
Although a [0057] pneumatic cylinder 444 is shown in FIG. 8 as the means for reciprocally moving the supporting member 442, other linear reciprocal driving mechanisms can be employed. Also, although the controller 452 and the pneumatic cylinder 444 are shown as being directly connected, the controller 452 can further include a direction control valve for controlling the flow of compressed air to and from the cylinder 444 and a flow rate control valve for controlling the flow rate of the compressed air. The processor 450 detects a polishing endpoint by analyzing the signals produced by the light measuring instrument 438, and the controller 452 controls the operation of the pneumatic cylinder 444. Otherwise, the functions of the processor 450, the controller 452 and a display 454 are identical to those of the first embodiment.
FIG. 9 shows a [0058] CMP apparatus 500 having a fourth embodiment of a polishing endpoint detecting device 530 according to the present invention. Referring to FIG. 9, a polishing pad 502 of a light-transmitting material is attached to a transparent rotary plate 512. A light source 534, a splitter 536 and a light measuring instrument 538 are disposed under the rotary plate 512 and polishing pad 502. The light source 534 emits a beam of light 532 a. The light 532 a from the light source 534 passes through the rotary plate 512 and the polishing pad 502 and impinges on the surface 10 a of the semiconductor substrate 10 at a predetermined angle of incidence. The light 532 b reflecting from the surface 10 a impinges on the splitter 536, whereby the light 532 b reflected from the surface 10 a of the semiconductor substrate 10 being polished is directed onto the light measuring instrument 538. The light measuring instrument 538 measures a characteristic of the light 532 c reflecting from the splitter 536.
The polishing [0059] endpoint detecting device 530 also comprises a light path changing device 540 including a supporting member 542 supporting the light source 534, the splitter 536, and the light measuring instrument 538, and a pneumatic cylinder 544 connected to the supporting member 542. Also, the polishing endpoint detecting device 530 includes a processor 550 for detecting a polishing endpoint by analyzing the signals produced by the light measuring instrument 538, a controller 552 for controlling the operation of the pneumatic cylinder 544, and a display 554. The light path changing device 540, the processor 550, the controller 552 and the display 554 are similar to those of the third embodiment of FIG. 8 and as such, a detailed description thereof will be omitted.
FIG. 10 illustrates a [0060] CMP apparatus 600 having a fifth embodiment of a polishing endpoint detecting device 630 according to the present invention. Referring to FIG. 10, a polishing pad 602 of a light-transmitting material is attached to a transparent rotary plate 612. A light source 634, a splitter 636 (of a half-mirror type) and a light measuring instrument 638 are disposed under the plate 612 and polishing pad 602.
The [0061] splitter 636 is positioned over the light source 634 as oriented with a predetermined angle of inclination. The light source 634 emits a beam of light 632 a vertically towards the surface 10 a of the semiconductor substrate 10 being polished. The splitter 636 transmits a portion of 632 b of the light 632 a from the light source 634, and reflects the remainder 632 c of the light 632 a. The light 632 b passing through the splitter 636 impinges on the surface 10 a of the semiconductor substrate 10. A portion 632 e of the light 632 d reflected from the surface 10 a of the semiconductor substrate 10 is reflected by the splitter 636, and the rest 632 f of the light 632 d passes through the splitter 636. A characteristic of the light 632 e reflected from the surface 10 a of the semiconductor substrate 10 and reflected by the splitter 636 is measured by the light measuring instrument 638.
The polishing [0062] endpoint detecting device 630 also comprises a light path changing device 640 including a supporting member 642 supporting the light source 634, the splitter 636, and the light measuring instrument 638, and a pneumatic cylinder 644 connected to the supporting member 642. Also, the polishing endpoint detecting device 630 includes a processor 650 for detecting a polishing endpoint by analyzing the signals produced by the light measuring instrument 638, a controller 652 for controlling the operation of the pneumatic cylinder 644, and a display 654. The light path changing device 640, the processor 650, the controller 652 and the display 654 are similar to those of the third embodiment of FIG. 8 and as such, a detailed description thereof will be omitted.
FIG. 11 illustrates another embodiment of a [0063] CMP apparatus 700 having a polishing endpoint detecting device 730 corresponding to that of the first embodiment. Referring FIG. 11, the CMP apparatus 700 includes a rotational table 710 to which a polishing pad 702 of a light-transmitting material is attached. The polishing endpoint detecting device 730 is disposed within the rotational table 710. A polishing head 720 holds the semiconductor substrate 10 opposite the polishing pad 702 and presses the surface 10 a of the semiconductor substrate 10 into contact with the polishing pad 702 during the polishing process. The CMP apparatus also includes a pad conditioner 722 for improving the surface condition of the polishing pad 702, and a slurry supplying member 724 for supplying slurry 724 a onto the polishing pad 702.
The rotational table [0064] 710 includes a rotary plate 712 of a light-transmitting material to which the polishing pad 702 is attached, a base plate 716 spaced a predetermined distance from the rotary plate 712 and coupled to a rotary shaft 726 that provides the rotational drive force for the rotational table 710, and a sidewall 714 extending along and between the outer peripheral edges of the base plate 716 and the rotary plate 712. The rotational table 710 thus has the overall shape of a disc, and defines an inner space 718 delimited by the rotary plate 712, the sidewall 714, and the base plate 716.
The polishing [0065] endpoint detecting device 730 is disposed in the inner space 718 of the rotary table 710 as mounted on the base plate 716. The polishing endpoint detecting device 730 includes a light source 734 for producing a beam of light, a splitter 742 for changing the path of the light so that the light emanating from the light source 734 is directed onto the surface 10 a of the semiconductor substrate 10, a light measuring instrument 736 for measuring a characteristic of the light reflected from the surface 10 a of the semiconductor substrate 10, and a motor 744 for rotating the splitter 742 so that the light applied to the surface 10 a of the semiconductor substrate 10 by the splitter 742 scans the surface 10 a along a horizontal line 760 (see FIG. 12) that passes through the center of the polishing pad 702.
A [0066] processor 750 and a controller 752 are disposed outside the rotary table 720. The processor 750 detects a polishing endpoint by analyzing the signals produced by the light measuring instrument 736, and the controller 752 controls the angular velocity and relative rotational position of the output shaft of the motor 744. The processor 750 and the controller 752 are connected to the light source 734, the light measuring instrument 736 and the motor 744 through rotary shaft 726. A display 754 is connected to the processor 750. In addition, although not shown, a linear reciprocal drive mechanism and supporting member can be disposed on the base plate 716 in order to move the light measuring instrument along a straight line.
In addition, a [0067] light sensor 756 having a light emitting portion and a light receiving portion cooperates with a peripheral portion of the rotational table 710 in order to effect a sampling of the signals produced by the light measuring instrument 736 which rotates together with the rotational table 710. The peripheral portion of the rotational table 710 with which the light sensor 756 cooperates is disposed opposite the polishing endpoint detecting device 730 with respect to the center of rotation of table 710. The light sensor 756 is connected to the controller 752 coupled to the processor 750. When the peripheral portion of the table 710 blocks the transmission of light from the light emitting portion to the light receiving portion of the light sensor 756, the processor 750 samples the signals produced by the light measuring instrument 736.
As shown in FIG. 12, the light applied to the [0068] surface 10 of the semiconductor substrate 10 scans the surface 10 a of the semiconductor substrate 10 along a horizontal line 760 passing through the centers of the polishing pad 702 and the semiconductor substrate 10. At that time, the point 10 c on the surface 10 a of the semiconductor substrate 10, impinged by the light coming from the splitter 742 moves by regular intervals along the horizontal line 760. Such interval is determined by the rotational speed of the motor 744, and is related to the rotational speed of the rotational table 710. The rotational speeds of the motor 744 and the table 710 can be set according to the parameters of the polishing process.
The amount by which the [0069] semiconductor substrate 10 is polished is thus measured with respect to the entire surface 10 a of the semiconductor substrate 10, and the processor 750 detects the polishing endpoint based on this amount. Therefore, the over-polishing or under-polishing of the semiconductor substrate 10 can be prevented. Also, because the rotary plate 712 and the polishing pad 702 each comprise light-transmitting material, very little time is required for changing the polishing pad 702.
FIG. 13 illustrates a [0070] CMP apparatus 800 having a polishing endpoint detecting device 830 corresponding to the second embodiment of the present invention. Referring FIG. 13, the CMP apparatus 800 includes a rotational table 810 to which a polishing pad 802 of a light-transmitting material is attached, a polishing endpoint detecting device 830 installed in the rotational table 810, a polishing head 820 for holding a semiconductor substrate 10 to be polished so that a surface 10 a of the semiconductor substrate 10 faces and is pressed into contact with the polishing pad 802, a pad conditioner 822 for improving a surface condition of the polishing pad 802, and a slurry supplying member 824 for supplying slurry 824 a onto the polishing pad 802.
The rotational table [0071] 810 has a rotary plate 812 of a light-transmitting material to which the polishing pad 802 is attached, a base plate 816 coupled to a rotary drive shaft 826, and a sidewall 814 extending along and between the outer peripheral edges of the base plate 816 and the rotary plate 812. The polishing table 810 thus has the overall shape of a disc, and an inner space 818 delimited by the rotary plate 812, the sidewall 814 and the base plate 816.
The polishing [0072] endpoint detecting device 830 is installed in the inner space 818 of the rotational table 810 as supported by the base plate 816. The polishing endpoint detecting device 830 includes a light source 834 for producing a beam of light, a light measuring instrument 836 for measuring a characteristic of the light reflected from the surface 10 a of the semiconductor substrate 10, a supporting member 842 for supporting the light source 834 and the light measuring instrument 836, and a pneumatic cylinder 844 coupled to the supporting member 842. The pneumatic cylinder 844 reciprocally moves the supporting member 842 in a straight line so that the light emanating from the light source 834 scans the surface 10 a of the semiconductor substrate 10 along a horizontal line which passes through the center of the polishing pad 802.
A [0073] processor 850 for detecting a polishing endpoint by analyzing the signals from the light measuring instrument 836, and a controller 852 for controlling the operation of the pneumatic cylinder 844, are disposed outside the rotational table 810. The processor 850 and the controller 852 are connected to the light source 834, the light measuring instrument 836 and the pneumatic cylinder 844 through the rotary shaft 826. In addition, though not shown, a guide can be disposed on the base plate 816 to guide the supporting member 842 for movement along a straight line.
A [0074] light sensor 856 cooperates with a peripheral portion of the rotational table 810 to effect the sampling of the signals produced by the light measuring instrument 836, and a display 854 showing the results of the analysis of these signals is connected to the processor 850. Further detailed descriptions of these elements will be omitted because these elements are similar to those already described in connection with the polishing endpoint detection device 330 shown in FIG. 7 and the CMP apparatus 700 shown in FIGS. 11 and 12.
FIG. 14 illustrates a [0075] CMP apparatus 900 having a polishing endpoint detecting device 930 corresponding to that of the third embodiment of the present invention. Referring FIG. 14, the CMP apparatus 900 has a rotational table 910 to which a polishing pad 902 of a light-transmitting material is attached, a polishing endpoint detecting device 930 installed in the rotational table 910, a polishing head 920 holding a semiconductor substrate 10 to be polished so that a surface 10 a of the semiconductor substrate 10 is disposed opposite and is pressed into contact with the polishing pad 902 during a polishing process, a pad conditioner 922 for improving a surface condition of the polishing pad 902, and a slurry supplying member 924 for supplying a slurry 924 a onto the polishing pad 902.
The rotational table [0076] 910 includes a rotary plate 912 of a light-transmitting material to which the polishing pad 902 is attached, a base plate 916 coupled to a rotary shaft 926, and a sidewall 914 extending along and between the outer peripheral edges of the base plate 916 and the rotary plate 912. The rotational table 910 thus has the overall shape of a disc, and an inner space 918 delimited by the rotary plate 912, the sidewall 914 and the base plate 916.
The polishing [0077] endpoint detecting device 930 is installed in the inner space 918 of the rotational table 910 as supported by the base plate 916. The polishing endpoint detecting device 930 includes a light source 934 for producing a beam of light, a splitter 936 for changing the path of the light so that the light emanating from the light source 934 is directed onto the surface 10 a of the semiconductor substrate 10, a light measuring instrument 938 for measuring a characteristic of the light reflected from the surface 10 a of the semiconductor substrate 10, a supporting member 942 supporting the light source 934, the splitter 936, and the light measuring instrument 938, and a pneumatic cylinder 944 coupled to the supporting member 942. The pneumatic cylinder 944 moves the supporting member 942 reciprocally in a straight line so that the light scans the surface 10 a of the semiconductor substrate 10 along a horizontal line that passes through the center of the polishing pad 902.
A [0078] processor 950 and a controller 952 are disposed outside the rotational table 910. The processor 950 detects a polishing endpoint by analyzing the signals produced by the light measuring instrument 938, and the controller 952 controls the operation of the pneumatic cylinder 944. The processor 950 and the controller 952 are connected to the light source 934, the light measuring instrument 938 and the pneumatic cylinder 944 through the rotary shaft 926. In addition, although not shown, a guide can be disposed on the base plate 916 to guide the supporting member 942 for movement along a straight line.
A [0079] light sensor 956 cooperates with a peripheral portion of the rotational table 910 to effect a sampling of the signals produced by the light measuring instrument 938, and a display 954 showing the result of the analysis of these signals is connected to the processor 950. A further detailed description of these elements will be omitted because these elements are similar to those of the polishing endpoint detecting device 430 shown in FIG. 8 and the CMP apparatus 700 shown in FIG. 11 and FIG. 12.
According to the present invention, light from a light source is applied onto a surface of a semiconductor substrate through a rotary plate to which a transparent polishing pad is attached. The light applied onto the surface of the semiconductor substrate is scanned across the surface of the semiconductor substrate along a horizontal line passing through the centers of the polishing pad and the semiconductor substrate. A light measuring instrument measures a characteristic of the light reflected from the surface of the semiconductor substrate. A processor detects a polishing endpoint by analyzing signals produced by the light measuring instrument as representative of a characteristic of the light reflected from the surface of the semiconductor substrate. [0080]
Therefore, the amount that the entire surface of the semiconductor substrate has been polished can be measured, whereby the polishing endpoint detected can prevent the over-polishing or under-polishing of the semiconductor substrate. Also, little slurry or by-product of the polishing process accumulates between the surface of the semiconductor substrate and the polishing pad. Accordingly, the polishing endpoint is detected with a high degree of reliability. [0081]
Furthermore, because the polishing pad and the rotary plate are of light-transmitting materials, they do not have to be aligned in a circumferential direction. Therefore, very little time is required for changing the polishing pad, whereby the downtime of the CMP apparatus is kept to a minimum and the productivity of the CMP process is enhanced. [0082]
Finally, although the present invention has been described above with reference to the preferred embodiments thereof, it is evident that many modifications and variations thereof will be apparent to those having ordinary skill in the art. Accordingly, all such modifications and variations are seen to be within the true spirit and scope of the invention as defined by appended claims. [0083]

Claims

What is claimed is:

1. A polishing endpoint detecting device for use in detecting a polishing endpoint of a process of polishing a surface of a substrate, comprising:

a light source for producing a beam of light to be provided onto a surface of the substrate being polished by a polishing pad that is transparent with respect to the beam of light;

light path changing means for changing a path of the beam of light so that the beam of light scans the surface of the substrate along a horizontal line across the surface of the substrate;

a light measuring instrument operative to produce signals representative of a characteristic of a light reflected from the surface of the substrate and to output the signals; and

a processor connected to the light measuring instrument so as to receive the signals produced by the light measuring instrument and configured to analyze the signals to detect a polishing endpoint of the polishing process.

2. The polishing endpoint detecting device of claim 1, wherein the horizontal line passes through a center of the polishing pad.

3. The polishing endpoint detecting device of claim 1, wherein the light path changing means comprises a reflective splitter, and driving means for rotating the splitter.

4. The polishing endpoint detecting device of claim 1, wherein the light path changing means comprises a supporting member supporting the light source and the light measuring instrument, and driving means for moving the supporting member reciprocally along a straight line.

5. The polishing endpoint detecting device of claim 4, wherein the light path changing means further comprises a reflective splitter oriented to direct the beam of light produced by the light source onto the surface of the substrate.

6. The polishing endpoint detecting device of claim 4, wherein the light path changing means further comprises a reflective splitter oriented to direct the light reflected from the scanned surface of the substrate to the light measuring instrument.

7. The polishing endpoint detecting device of claim 6, wherein the splitter is partially transmitting with respect to the beam of light produced by the light source, and is disposed above the light source so that some of the light produced by the light source directs onto the surface of the substrate through the splitter.

8. A chemical-mechanical polishing apparatus comprising:

a light source that produces a beam of light;

a rotational table rotatable about a central axis of rotation, the rotational table including a rotary plate including a first material that is transparent with respect to the light produced by the light source, and a polishing pad including a second material that is transparent with respect to the light produced by the light source, the polishing pad being attached to the rotary plate;

a polishing head disposed above the polishing pad for holding a substrate such that a surface of the substrate faces the polishing pad and is pressed into contact with the polishing pad, and rotating the substrate while the surface of the substrate is in contact with the polishing pad;

light path changing means for changing a path of the beam of light so that the beam of light scans the surface of the substrate along a horizontal line across the surface of the substrate held against the polishing pad by the polishing head through the rotary plate and the polishing pad;

a light measuring instrument operative to produce signals representative of a characteristic of a light reflected from the surface of the substrate; and

9. The chemical-mechanical polishing apparatus of claim 8, wherein the rotational table further includes a rotary shaft having a central longitudinal axis corresponding to the axis of rotation, a base plate mounted to the rotary shaft, and a sidewall extending between and along outer peripheral edges of the rotary plate and the base plate, wherein the rotational table has an inner space delimited by the base plate, the sidewall and the rotary plate, and wherein the light source, the light path changing means and the light measuring instrument are disposed in the inner space as supported by the base plate.

10. The polishing endpoint detecting device of claim 9, wherein the light path changing means comprises a reflective splitter, and driving means for rotating the splitter.

11. The polishing endpoint detecting device of claim 8, wherein the light path changing means comprises a reflective splitter, and driving means for rotating the splitter.

12. The polishing endpoint detecting device of claim 8, wherein the light path changing means comprises a supporting member supporting the light source and the light measuring instrument, and driving means for moving the supporting member reciprocally along a straight line.

13. The polishing endpoint detecting device of claim 12, wherein the light path changing means further comprises a reflective splitter that reflects the beam of light.

14. The polishing endpoint detecting device of claim 12, wherein the splitter is partially transmitting with respect to the beam of light produced by the light source, and is disposed above the light source so that some of the light produced by the light source directs onto the surface of the substrate through the splitter.

15. The polishing endpoint detecting device of claim 9, wherein the light path changing means comprises a supporting member supporting the light source and the light measuring instrument, and driving means for moving the supporting member reciprocally along a straight line.

16. The polishing endpoint detecting device of claim 8, wherein the horizontal line passes through a center of the polishing pad.

17. The chemical-mechanical polishing apparatus of claim 8, wherein the first material includes an acrylic acid resin.

18. The chemical-mechanical polishing apparatus of claim 8, wherein the second material includes polyurethane.

19. The chemical-mechanical polishing apparatus of claim 8, further comprising a display for showing an analysis result of the processor.

20. The chemical-mechanical polishing apparatus of claim 8, further comprising a slurry supply member disposed above the polishing pad for supplying a slurry onto the polishing pad.