US20070151845A1

US20070151845A1 - Apparatus for forming metal film

Info

Publication number: US20070151845A1
Application number: US11/430,948
Authority: US
Inventors: Chieh-Kai Chang; Chao-Kai Cheng; Ming-Huan Yang; Chung-Wei Wang; Fu-Kang Cheng; Tzyy-Jang Tseng; Chang-Ming Lee; Chih-Ming Chang; Cheng-Po Yu
Original assignee: Industrial Technology Research Institute ITRI; Unimicron Technology Corp
Current assignee: Industrial Technology Research Institute ITRI; Unimicron Technology Corp
Priority date: 2005-12-29
Filing date: 2006-05-10
Publication date: 2007-07-05
Also published as: TW200724726A; TWI314957B

Abstract

An apparatus for metal plating on a substrate with through-holes includes a chamber that the substrate is disposed inside the chamber to be divided into two sections. A pressure generator and a pressure controller are connected to this and correspond to two sides of the substrate respectively. The pressure generator is used for pumping a electrolyte flowed parallel to the surface of the substrate into the chamber. The pressure controller is used for channeling the electrolyte off the chamber and controlling the pressure differences between the two sides of the substrate. So that the electrolyte flowed parallel to the surface of the substrate is pumped by the pressure generator and it passes several through-holes to control the thickness of metal plating on the.substrate and inner walls of the through-holes.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No(s). 094147334 filed in Taiwan, R.O.C. on Dec. 29, 2005, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of Invention
The present invention relates to an apparatus for forming a metal film, in particular an apparatus for forming a metal film with a uniform thickness on the surface of a substrate and on the inner wall of a through-hole in the substrate.
2. Related Art
With the development of electronic devices, printed circuit boards (PCBs) have been gradually developed for high density packaging, such that the line width of a metal circuit formed on a surface has become smaller, and the aperture of a through-hole in the surface for a pin of an electronic element to pass through has been gradually reduced. Therefore, the thickness of the metal films formed on printed circuit boards must be highly uniform; and defects of the metal films must be minimized, so as to improve the ductility and tensile strength, and prevent printed circuit boards from being cracked and broken due to thinner circuits and insufficient strength.
Japanese Patent JP56-58999 provides an apparatus for washing a substrate on which a metal film is to be formed, while the substrate is conveyed between two tanks, such that the time consumed for washing the substrate is reduced. In US Patent U.S. Pat. No. 5,077,099, a periodic vibration source is provided for vibrating the substrate. The electrolyte is driven by vibration on the surface of a substrate and is circulated. The method controls the thickness of a metal film uniformly. In US Patent U.S. Pat. No. 5,077,099, only the thickness of the metal film on the surface of the substrate can be improved. But for the metal film on the inner wall of the through-holes in the substrate, the electrolyte cannot flow within the through-holes and even cannot wet the through-holes effectively. Moreover, as the dimension of through-hole reduces, the aspect ratio, the proportion between the axial length and the radial width increases. So that forming metal film within the through-holes become more difficult. Also the metal films formed on the inner walls of the through-holes are extremely poor, and affect the yield of printed circuit boards. Therefore, how to design a desirable metal film technology directed to through-holes with small apertures and high aspect ratios has become an important issue.

SUMMARY OF THE INVENTION

In view of aforementioned problem, the object of the present invention is to provide an apparatus for forming a metal film to solve the problem that prior to when the metal film is formed on the substrate, the thickness of the metal films on the surface of a substrate and on inner walls of through-holes is non-uniform.
In order to achieve the aforementioned object, an apparatus for forming a metal film is provided to form the metal film on the substrate with at least one through-hole, and comprises a sealed chamber, a pressure generator, and a pressure controller. The substrate is disposed within the sealed chamber to divide the sealed chamber into a first section and a second section. The pressure generator and the pressure controller are connected to the sealed chamber and correspond to the first and second sections, respectively. The pressure generator is used to pump a electrolyte and enable it to flow in parallel with the surface of the substrate, and the pressure controller is used to derive the electrolyte and control the pressure difference between the two sides of the substrate. Thereby, the electrolyte is pumped by the pressure generator to flow into the sealed chamber, so as to flow in parallel with the surface of the substrate and to flow through the through-holes. Therefore, through the adjustment of the pressure controller, the thickness of the metal films formed respectively on the surface of the substrate and on the inner walls of the through-holes is controlled.
According to another embodiment of the present invention, the apparatus for forming a metal film further comprises an electrolyte stabilizing device for stirring the electrolyte flowing into the sealed chamber, so as to enable solute and solvent in the electrolyte to be fully mixed, such that the ingredients are more uniform.
According to another embodiment of the present invention, the apparatus for forming a metal film further comprises a temperature controller for controlling the temperature of the electrolyte flowing into the sealed chamber, so as to control the conditions for forming the metal film.
According to another embodiment of the present invention, the apparatus for forming a metal film further comprises a laminar flow stabilizing device for eliminating the boundary layer of the fluid flowing into the sealed chamber, such that the flow rate of the electrolyte on the surface of the substrate will become more uniform.
According to another embodiment of the present invention, the apparatus for forming a metal film further comprises a flow rate controlling element disposed in the sealed chamber. Through adjusting the space between the flow rate controlling element and the surface of the substrate, the flow rate of the fluid flowing on the surface of the substrate can be adjusted.
According to another embodiment of the present invention, the apparatus for forming a metal film further comprises an electric field controller with two electrodes. Two electrodes are immersed in the electrolyte in the sealed chamber and located on the two sides of the substrate, so as to generate an electric filed. Thus, the substrate is located in the electric field to strengthen the metal film forming effect.
Further scope of applicability of the present invention. will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
Both the foregoing general description about the present invention and the following detailed description about the embodiments are intended to demonstrate and explain the principles of the present invention, and to provide further explanation of the present invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given herein below for illustration only, and which thus is not limitative of the present invention, and wherein:
FIG. 1 shows an apparatus for forming metal film according to the present invention;
FIG. 2 is an exploded view of the apparatus for forming metal film according to a first embodiment of the present invention;
FIG. 3 is a schematic cross-sectional view depicted in FIG. 2;
FIG. 4 is a system block diagram depicted in FIG. 2;
FIG. 5 is a system block diagram of the apparatus for forming metal film according to a second embodiment of the present invention;
FIGS. 6 and 7 are system block diagrams of other implementation aspects according to the second embodiment of the present invention;
FIG. 8 is a system block diagram of the apparatus for forming metal film according to a third embodiment of the present invention; and
FIG. 9 is a system block diagram of the apparatus for forming metal film according to a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In order to make the objects, structures, features, and functions of the present invention more comprehensible, preferred embodiments accompanied with figures are described in detail below.
Please refer to FIG. 1 of an apparatus for forming a metal film according to the present invention. The apparatus for forming metal film comprises a frame 1, a delivery system 2, and a plurality of electrolyte tanks A, B, C, D, E, F, G, H, and I. The delivery system 2 is disposed above the frame 1 to move a substrate to be processed among each of the electrolyte tanks A, B, C, D, E, F, G, H, and I. Each of the electrolyte tanks A, B, C,.D, E, F, G, H, and I is used to conduct a surface treatment process and a metal film forming process, respectively. The surface treatment process is used to form a substrate film on the surface of the substrate, and after that, a catalyst is coated on the surface of the substrate in a specific pattern. Next, the metal film forming process is conducted to deposit the metal on the region coated with the catalyst, so as to form the metal film with a predetermined pattern. The apparatus for forming a metal film of the present invention can be applied in each of the electrolyte tanks to enable the plate solutions with different ingredients or the deionized water to flow on the surface of the substrate uniformly, so as to control the grown thickness of the metal film.
FIGS. 2, 3, and 4 show the apparatus for forming a metal film according to the first embodiment of the present invention. The apparatus for forming a metal film can be applied to any of the aforementioned electrolyte tanks. Each of the electrolyte tanks includes a sealed chamber 10, and the substrate 20 to be processed is disposed within the sealed chamber 10 and divides the sealed chamber 10 into a first section and a second section. Additionally, each substrate 20 is provided with a plurality of through-holes 21, such that the fluid may flow through the substrate 20 and circulate between two sides of the substrate 20.
A fluid feeding element 11 and a fluid deriving element 12 are further disposed within the sealed chamber 10. The fluid feeding element 11 is shaped as a frame. Also, a circulating pipe 111 is disposed within the fluid feeding element 11 and connected to a pressure generating apparatus 31 via a connecting tube, such that the electrolyte or the deionized water is fed into the circulating pipe 111 and flows into the sealed chamber 10 via the apertures 112 formed at the inner edge of the fluid feeding element 11. The fluid deriving element 12 is substantially the same as the fluid feeding element 11, shaped as a frame. Also, a circulating pipe 121 is disposed within the fluid deriving element 12, and a plurality of apertures 122 is formed in the inner edge and used for absorbing the electrolyte in the sealed chamber 10, and then deriving the electrolyte out of the sealed chamber 10 via a pressure controller 32 connected to the fluid deriving element 12. The fluid feeding element 11 and the fluid deriving element 12 are disposed in parallel with the two sides of the substrate 20, such that the pressure generator 31 and the pressure controller 32 are correspondingly connected to the first and second sections of the sealed chamber 10, respectively.
The fluid feeding element 11 and the fluid deriving element 12 are disposed at the two sides of the substrate 20 in parallel with each other, such that the direction of the apertures 112 and 122 in the inner edge is parallel to the surface of the substrate 20. Therefore, both the fluid fed into the sealed chamber 10 through the fluid feeding element land the fluid ,such as the electrolyte or the deionized water, drawn out by the fluid deriving element 12 flow in the direction parallel to the surface of the substrate 20 and flow through the through-holes 21 in the direction perpendicular to the substrate 20. The pressure generator 31 can be a fluid pump, and the pressure controller 32 can be a valve. The pressure difference between the two sides of the substrate 20 is controlled through adjusting the pressure generator 31 together with the pressure controller 32, so as to adjust the flow rate. Thus, the flow rate 41 of the fluid flowing in parallel with the surface of the substrate 20 is the same as that of the flow rate 42 of the fluid flowing through the through-holes 21. As such, the conditions for forming the metal film on the surface of the substrate 20 are similar to those for forming it on the inner walls of the through-holes 21, such that the growing rate of the metal film on the surface of the substrate 20 is the same as that of the metal film on the inner walls of the through-holes 21. Therefore, the thickness of the metal film is uniform and the electrical conductivity or the stress is relatively uniform, and no significant difference occurs. A predetermined pattern is formed on the surface of the substrate 20 via the catalyst. When the substrate 20 is immersed in the electrolyte, an ion or a proton exchange occurs between the ingredients of the electrolyte and the catalyst, such that the metal is precipitated and plated on the substrate to form a pattern.
Referring to FIG. 5, it shows the apparatus for forming a metal film according to the second embodiment of the present invention. As shown in FIG. 5, an electrolyte stabilizing device 51 is further disposed between the pressure generator 31 and the sealed chamber 10. The electrolyte stabilizing device 51 is used to stir the electrolyte, such that the solute and the solvent in the electrolyte are mixed more uniformly to further stabilize the quality of the electrolyte. For the embodiment, the electrolyte stabilizing device 51 is a stirring device, which stirs the electrolyte before it flows into the sealed chamber 10, so as to further stabilize the feature of the electrolyte.
Referring to FIGS. 6 and 7, the electrolyte stabilizing device can be a gas source 52, which feeds the gas into the electrolyte and stirs the electrolyte by tiny bubbles. The gas is fed into the electrolyte before it flows into the sealed chamber 10 and stabilizes the electrolyte in advance, as shown in FIG. 6. The gas source 52 also can be connected to the fluid feeding element 31, and then the gas is directly fed into the sealed chamber 10 to stir and stabilize the electrolyte in the sealed chamber 10, as shown in FIG. 7.
Please refer to FIG. 8 of a system block diagram of the apparatus for forming a metal film according to the third embodiment of the present invention. In order to control the condition of the electrolyte effectively, a temperature controller 53 and a laminar flow stabilizing device 54 are disposed between the pressure generator 31 and the pressure controller 32 in this embodiment, and the status of the fluid boundary layer of the electrolyte is changed before being fed into the sealed chamber 10 by the pressure generating apparatus 31, such that the flow rate of the electrolyte flowing in parallel with the surface of the substrate-20 is uniform and stable.
The temperature controller 53 includes a heater, used to control the temperature of the electrolyte. Thus, an optimal reaction temperature is achieved before the electrolyte flows into the sealed chamber 10, so as to enhance the rate for forming the metal film. The laminar flow stabilizing device 54 is consisted of a porous medium. Since the thickness of the boundary layer of the fluid is gradually increased due to the flowing of the electrolyte within the pipe, the flow rate of the electrolyte is not uniform when the electrolyte reaches the substrate 20. If the electrolyte flows through the laminar flow stabilizing device 54 before flowing into the sealed chamber 10, the laminar flow phenomenon is destroyed, and the boundary layer grows once again. Thus; when the electrolyte flows into the sealed chamber 10, the flow rate becomes more uniform, such that the growth rate and the thickness of the metal film will be relatively uniform.
Additionally, a flow rate controlling element 55 is further provided in this embodiment, which is a plate body moving relative to the substrate 20 to adjust the space W between the flow rate controlling element 55 and the substrate 20, the flow rate of the electrolyte flowing on the surface of the substrate 20 can be changed. Thus, the flow rate of the electrolyte can be further adjusted.
Please refer to FIG. 9 of a schematic view of the apparatus for forming a metal film according to the fourth embodiment of the present invention. In order to further control the metal film forming process and strengthen the metal film forming rate, an electric field controller 56 is disposed to generate an alternating current or a direct current. The electric field controller 56 has two electrodes 561 disposed within the sealed chamber 10, immersed in the electrolyte, and located on the two sides of the substrate 20 respectively. Through applying a direct current or an alternating current, the substrate 20 is disposed within an electric field to strengthen the metal film forming rate.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims

1. An apparatus for forming a metal film on a substrate with at least one through-hole, comprising:

a sealed chamber, wherein the substrate is disposed within said sealed chamber and divide said sealed chamber into a first section and a second section;

a pressure generator, correspondingly connected to the first section of said sealed chamber, for pumping electrolyte to flow in parallel with the surface of the substrate; and

a pressure controller, correspondingly connected to the second section of said sealed chamber, for deriving the electrolyte and controlling the pressure difference between two sides of the substrate;

wherein the electrolyte is pumped by said pressure generator into said sealed chamber, flowing in the direction parallel to the surface of the substrate and flowing through the through-holes in the direction perpendicular to the substrate, and the thickness of the metal film grown in parallel with the surfaces of the substrate and the through-hole are uniformly formed.

2. The apparatus for forming a metal film as claimed in claim 1, further comprising a electrolyte stabilizing device disposed between the substrate and said pressure generator, for stirring the electrolyte and stabilizing the quality of the electrolyte.

3. The apparatus for forming a metal film as claimed in claim 2, wherein said electrolyte stabilizing device is a gas source for feeding a gas, so as to stir the electrolyte.

4. The apparatus for forming a metal film as claimed in claim 2, wherein said electrolyte stabilizing device is a stirring device.

5. The apparatus for forming a metal film as claimed in claim 1, further comprising a laminar flow stabilizing device disposed between said pressure generator and said sealed chamber, for changing the state of the fluid boundary layer of the electrolyte, such that the flow rate of the electrolyte flowing in parallel with the substrate is uniform and stable.

6. The apparatus for forming a metal film as claimed in claim 5, wherein said laminar flow stabilizing device is a porous medium.

7. The apparatus for forming a metal film as claimed in claim 1, further comprising an electric field controller with two electrodes, wherein the two electrodes are immersed in the electrolyte and disposed on the two sides of the substrate respectively, so as to generate an electric field.

8. The apparatus for forming a metal film as claimed in claim 7, wherein a direct current is applied between the two electrodes.

9. The apparatus for forming a metal film as claimed in claim 7, wherein an alternating current is applied between the two electrodes.

10. The apparatus for forming a metal film as claimed in claim 1, further comprising a temperature controller for controlling the temperature of the electrolyte.

11. The apparatus for forming a metal film as claimed in claim 1, further comprising a flow rate controller disposed within said sealed chamber, wherein said flow rate controller moves relative to the substrate to adjust the space there-between, so as to control the flow rate of the electrolyte when flowing in parallel with the surface of the substrate.

12. The apparatus for forming a metal film as claimed in claim 1, wherein said pressure generator is a liquid pump.

13. The apparatus for forming a metal film as claimed in claim 1, further comprising a fluid feeding element disposed within said sealed chamber and connected to said pressure generator, and located on one side of the substrate, for guiding the electrolyte to be flowed in parallel with the surface of the substrate.

14. The apparatus for forming a metal film as claimed in claim 13, wherein said fluid feeding element is shaped as a frame, with a circulating pipe disposed therein, and with a plurality of through holes located at an inner edge of the circulating pipe.

15. The apparatus for forming a metal film as claimed in claim 1, wherein the substrate has a pattern formed with a catalyst, when the substrate is immersed in the electrolyte, an ion or a proton exchange is conducted between the electrolyte and the catalyst, forming the metal film with the pattern.

16. The apparatus for forming a metal film as claimed in claim 1, further comprising a fluid deriving element disposed within said sealed chamber and connected to said pressure generation device, and located on one side of the substrate, for guiding the electrolyte to be flowed in parallel with the surface of the substrate.

17. The apparatus for forming a metal film as claimed in claim 16, wherein said fluid deriving element is shaped as a frame, with a circulating pipe disposed therein, and with a plurality of through holes located at an inner edge of the circulating pipe.