Wax polishing process and polishing device for silicon wafer

Abstract

The invention relates to the technical field of silicon wafer processing, in particular to a silicon wafer wax polishing process and a silicon wafer wax polishing device.The silicon wafer wax polishing process comprises the following steps that S1, a polished wafer is placed on a wax polishing disk for wax surface mounting, the silicon wafer is continuously rotated for 1-60 s, and the back surface of the silicon wafer is coated with liquid wax under the action of centrifugal force; and S2, a physical and chemical dual-combined cleaning mode is adopted for cleaning, the polishing disc is cleaned through the combined action of a brush and a dewaxing cleaning agent firstly, then the polishing disc is put into a cleaning machine with an ultrasonic device for secondary cleaning, and the polishing disc is recycled after being cleaned. According to the silicon wafer wax polishing process and the polishing device, more uniform wax film thickness distribution is obtained by seeking the optimal rotating speed and continuous rotating time, and the silicon polished wafer is better in local flatness and higher in yield after chemical mechanical polishing. The polishing disc dewaxing cleaning method is improved, and the polishing disc dewaxing cleaning method can be used for better cleaning the polishing disc in a wax polishing process.

Description

Technical Field

[0001] The invention relates to the technical field of silicon wafer processing, in particular to a silicon wafer wax polishing process and a polishing device. Background Art

[0002] The current mainstream single-sided chemical mechanical polishing (CMP) method for silicon substrate materials in the world all uses a wax patch. Liquid wax is evenly applied to the back surface of the silicon wafer, then pasted on a very flat fixture and polished on a single-sided polishing machine. The uniformity of the wax film thickness between the silicon wafer and the fixture determines the numerical value of the local flatness (SBIR, SFQR) of the silicon substrate material after polishing. As the performance of global integrated circuit products becomes higher and higher, the physical line width inside them becomes smaller and smaller, and the semiconductor integrated circuit industry has higher and higher requirements for the local flatness of silicon substrate polishing sheets.

[0003] The surface polishing of silicon wafers can be divided into two processing forms according to the different forms of wafers: single-sided polishing of wafers without wax (commonly used for silicon wafers with a diameter less than 125mm) and single-sided polishing of wafers with wax (commonly used for silicon wafers with a diameter of 150mm to 200mm). However, for the polishing of relatively thin silicon wafers, due to the problems of glass fiber reinforced plastic strength and hole depth error of the polishing pad itself, sticky wax polishing is often used. Although sticky wax polishing can obtain extremely high geometric parameters, for polishing wafers with higher surface particle size requirements, especially for polishing wafers with surface particles less than 0.3μm, dewaxing and cleaning after polishing become the key technology.

[0004] In the prior art, after the silicon wafer is polished, since the polishing disk needs to be used for a long time, a lot of polishing wax will remain inside after use. Generally, it is manually cleaned by adding a cleaning agent. This method cannot better clean the polishing disk in the wax polishing process, and cannot ensure the thorough cleaning of the polishing disk. In addition, during long-term processing, residual wax will accumulate in the polishing disk, causing the residual wax to easily clog and contaminate. In addition, after the silicon wafer is processed, organic matter will cover part of the silicon wafer surface, making it difficult to remove the oxide film and related contamination; then the oxide film is dissolved, because the oxide layer is a "contamination trap", it will also introduce epitaxial defects; finally, contamination such as particles and metals are removed, and the silicon wafer surface is passivated at the same time. Summary of the invention

[0005] The purpose of the present invention is to provide a silicon wafer wax polishing process and a polishing device to solve the problem that a lot of polishing wax remains inside the polishing disk mentioned in the above background technology. Generally, it is manually cleaned by adding a cleaning agent. This method cannot better clean the polishing disk in the wax polishing process, and cannot ensure thorough cleaning of the polishing disk. In addition, during long-term processing, residual wax will accumulate in the polishing disk, causing the residual wax to easily clog and contaminate. In addition, after the silicon wafer is processed, organic matter will cover part of the silicon wafer surface, making it difficult to remove the oxide film and related contamination.

[0006] To achieve the above object, the present invention provides a silicon wafer wax polishing process, comprising the following steps:

[0007] S1. Place the polishing sheet on a waxed polishing disk for waxed wafer application. Rotate the silicon wafer continuously for 1-60 seconds. Liquid wax is coated on the back surface of the silicon wafer under the action of centrifugal force. Whether the wax film is uneven due to too low a rotation speed or part of the silicon wafer surface is not covered due to too high a rotation speed, micron-level undulating morphology will be formed on the polished surface of the silicon wafer after waxed polishing, which will hinder the device manufacturing in the subsequent process and reduce the yield of the device factory.

[0008] S2. Use a combination of physical and chemical cleaning methods to clean the polishing disc. First, clean the polishing disc with a brush and a wax remover, then put it into a cleaning machine with an ultrasonic device for secondary cleaning, and then recycle it after cleaning;

[0009] S3, by connecting a short reducing tube to the film loading stand, and then connecting the residual wax recovery bottle to the reducing tube, the discharged residual wax can be directly stored in the residual wax recovery bottle in a very short time; the problem of easy blockage and contamination caused by the long catheter when using drainage and diversion is solved;

[0010] S4. RCA cleaning and megasonic cleaning technology are used to clean the surface of the polished silicon wafer.

[0011] As a preferred embodiment of the present invention, in step S2, the residual wax is recovered by a dewaxing agent recovery tank, so that the dewaxing agent can be reused, thereby reducing costs.

[0012] As a preferred embodiment of the present invention, in step S2, the dewaxing cleaning agent is sprayed through the dewaxing agent adding tube, and the brush divides the residual wax marks into countless small wax strips when it passes over the surface of the polishing disk, thereby increasing the contact area between the residual wax and the chemical cleaning agent, making the chemical reaction between the dewaxing cleaning agent and the residual wax more thorough, and countless small wax strips are more easily shaken off by the ultrasonic wave in the subsequent cleaning machine.

[0013] As a preferred embodiment of the present invention, the RCA cleaning is a typical wet chemical cleaning method that is still the most commonly used. The RCA cleaning method relies on solvents, acids, surfactants and water to spray, clean, oxidize, etch and dissolve pollutants, organic matter and metal ion pollution on the surface of the wafer without destroying the surface features of the wafer. After each use of chemicals, it must be thoroughly cleaned in ultrapure water (UPW).

[0014] As a preferred embodiment of the present invention, the megasonic cleaning technology uses the piezoelectric effect combined with the cleaning liquid to remove submicron particles and pollutants from the substrate. Its working principle is to excite the piezoelectric ceramic crystal through high-frequency (700-1000kHz) alternating current to make it vibrate, and the vibration generates sound waves. This sound wave propagates through the cleaning liquid to form a controllable cavitation phenomenon. The cavitation phenomenon is caused by the change in pressure when the sound wave passes through the liquid. When the sound wave crosses through the surface of the object, the pollutant particles on the surface of the chip are removed.

[0015] The present invention also provides a silicon wafer wax polishing device, which is used for the silicon wafer wax polishing process, including a wafer loading seat, a polishing disc is installed on the top of the wafer loading seat, a polishing sheet is installed inside the polishing disc, a turntable is installed on the top of the polishing sheet, and a silicon wafer is installed on the bottom of the turntable. The turntable is driven by a motor to rotate, driving the silicon wafer to perform a polishing operation on the surface of the polishing sheet.

[0016] As a preferred embodiment of the present invention, a polishing agent adding tube is installed on the upper part of the polishing disc, a nozzle is installed at the end of the polishing agent adding tube, the outside of the polishing agent adding tube is connected to the polishing agent storage tank, and the polishing agent adding tube is a snake neck tube structure.

[0017] As a preferred embodiment of the present invention, it also includes a cleaning tank, a cleaning disc is arranged on the upper part of the cleaning tank, a brush is installed on the bottom of the cleaning disc, the cleaning disc is supported by a bracket, a motor is installed in the middle of the top of the cleaning disc, the motor drives the cleaning disc to rotate, and a screw rod assembly is vertically installed on the bracket, and the screw rod assembly drives the cleaning disc to rise and fall.

[0018] As a preferred embodiment of the present invention, a dewaxing agent adding pipe is installed on one side of the upper part of the cleaning tank, a nozzle is installed on the upper end of the dewaxing agent adding pipe, and a dewaxing agent storage tank is connected to the lower end. The dewaxing agent adding pipe is a snake neck tube structure.

[0019] As a preferred solution of the present invention, a residual wax recovery bottle is arranged inside the film loading seat, the top of the residual wax recovery bottle is connected to a reducing tube, and the top end of the reducing tube is connected to the polishing disk.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. In the silicon wafer wax polishing process and polishing device, by seeking the best rotation speed and continuous rotation time, a more uniform wax film thickness distribution is obtained, and after chemical mechanical polishing, the local flatness of the silicon polishing wafer is better and the yield rate is higher.

[0022] 2. In the silicon wafer wax polishing process and polishing device, the polishing disc dewaxing and cleaning method is improved, which can be used to better clean the polishing disc in the wax polishing process.

[0023] 3. In the silicon wafer wax polishing process and polishing device, the common wax drainage and residual wax clogging and contamination problems are solved by recycling the residual wax.

[0024] 4. The silicon wafer has a wax polishing process and polishing device, and RCA cleaning and megasonic cleaning technology are used to clean the surface of the polished silicon wafer to ensure the cleanliness of the silicon wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is one of the partial structural schematic diagrams of the present invention;

[0026] Figure 2 This is the second schematic diagram of the partial structure of the present invention;

[0027] Figure 3 It is a schematic diagram of the internal structure of the film loading stand in the present invention.

[0028] The meaning of each number in the figure is:

[0029] 1. Film loading stand; 11. Reducer; 12. Residual wax recovery bottle; 2. Polishing disc; 3. Polishing disc; 4. Turntable; 5. Silicon wafer; 6. Polishing agent adding tube; 7. Cleaning tank; 8. Cleaning disc; 81. Brush; 9. Bracket; 10. Dewaxing agent adding tube; 11. Dewaxing agent storage tank. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] The present invention provides a silicon wafer wax polishing process and a polishing device, such as Figure 1-Figure 3 As shown, the following steps are included:

[0033] S1. Place the polishing sheet on a waxed polishing disk for waxed wafer application. Rotate the silicon wafer continuously for 1-60 seconds. Liquid wax is coated on the back surface of the silicon wafer under the action of centrifugal force. Whether the wax film is uneven due to too low a rotation speed or part of the silicon wafer surface is not covered due to too high a rotation speed, micron-level undulating morphology will be formed on the polished surface of the silicon wafer after waxed polishing, which will hinder the device manufacturing in the subsequent process and reduce the yield of the device factory.

[0034] S2. The polishing disc is first cleaned by a combination of physical and chemical cleaning methods. The polishing disc is then cleaned by a brush and a wax removal detergent. The polishing disc is then placed in a cleaning machine with an ultrasonic device for secondary cleaning. The polishing disc is then recycled after cleaning. The ultrasonic device removes the residual wax on the surface of the polishing disc placed in the cleaning machine through ultrasonic vibration. The polishing disc is fully cleaned by a combination of physical and chemical cleaning methods.

[0035] S3, by connecting a short reducing tube to the film loading stand, and then connecting the residual wax recovery bottle to the reducing tube, the discharged residual wax can be directly stored in the residual wax recovery bottle in a very short time; the problem of easy blockage and contamination caused by the long catheter when using drainage and diversion is solved;

[0036] S4. RCA cleaning and megasonic cleaning technology are used to clean the surface of the polished silicon wafer.

[0037] In this embodiment, in step S2, the residual wax is recovered through the wax remover recovery tank, so that the wax remover can be reused, reducing costs.

[0038] Specifically, in step S2, the dewaxing detergent is sprayed through the dewaxing agent adding tube, and the brush divides the residual wax marks into countless small wax strips when it passes over the surface of the polishing disk, thereby increasing the contact area between the residual wax and the chemical cleaning agent, making the chemical reaction between the dewaxing detergent and the residual wax more thorough, and countless small wax strips are more easily shaken off by the ultrasonic wave in the cleaning machine afterwards.

[0039] Furthermore, RCA cleaning is a typical and still the most commonly used wet chemical cleaning method. The RCA cleaning method relies on solvents, acids, surfactants and water to spray, clean, oxidize, etch and dissolve surface pollutants, organic matter and metal ion pollution on the wafer without destroying the surface features of the wafer. After each use of chemicals, it must be thoroughly cleaned in ultrapure water (UPW).

[0040] Furthermore, megasonic cleaning technology uses the piezoelectric effect combined with cleaning fluid to remove submicron particles and contaminants from the substrate. Its working principle is to stimulate the piezoelectric ceramic crystal through high-frequency (700-1000kHz) alternating current to make it vibrate, and the vibration generates sound waves. This sound wave propagates through the cleaning fluid to form a controllable cavitation phenomenon. The cavitation phenomenon is caused by the change in pressure when the sound wave passes through the liquid. When the sound wave crosses the surface of the object, the contaminant particles on the surface of the chip are removed.

[0041] Example 2

[0042] The present invention also provides a silicon wafer wax polishing device, which is used in a silicon wafer wax polishing process, such as Figure 1-Figure 3 As shown, it includes a wafer loading seat 1, a polishing disc 2 is installed on the top of the wafer loading seat 1, a polishing sheet 3 is installed inside the polishing disc 2, a turntable 4 is installed on the upper part of the polishing sheet 3, a silicon wafer 5 is installed on the bottom of the turntable, and the turntable 4 is driven by a motor to rotate, driving the silicon wafer 5 to perform a polishing operation on the surface of the polishing sheet 3.

[0043] Furthermore, a polishing agent adding tube 6 is installed on the upper part of the polishing disc 2, and a nozzle is installed at the end of the polishing agent adding tube 6. The outside of the polishing agent adding tube 6 is connected to the polishing agent storage tank. The polishing agent adding tube 6 is a snake-neck tube structure. Polishing agent is added to the inside of the polishing disc 2 through the polishing agent adding tube 6 to improve the polishing effect.

[0044] Furthermore, it also includes a cleaning tank 7, a cleaning disc 8 is arranged on the upper part of the cleaning tank 7, a brush 81 is installed on the bottom of the cleaning disc 8, the cleaning disc 8 is supported by a bracket 9, a motor is installed in the middle of the top of the cleaning disc 8, the motor drives the cleaning disc 8 to rotate, and a screw assembly is vertically installed on the bracket 9, the screw assembly drives the cleaning disc 8 to rise and fall, by placing the used polishing disc 2 into the cleaning disc 8, and then controlling the screw assembly to drive the cleaning disc 8 to descend, and then the cleaning disc 8 is driven to rotate by the motor, and then the brush 81 is driven to rotate, so that the inside of the cleaning disc 8 is cleaned.

[0045] Furthermore, a dewaxing agent adding pipe 10 is installed on one side of the upper part of the cleaning tank 7, a nozzle is installed on the upper end of the dewaxing agent adding pipe 10, and the lower end is connected to the dewaxing agent storage tank 11. The dewaxing agent adding pipe 10 is a snake-neck tube structure, and the dewaxing agent is added to the cleaning tray 8 through the dewaxing agent adding pipe 10.

[0046] Furthermore, a residual wax recovery bottle 12 is provided inside the film loading seat 1, and a reducing tube 11 is connected to the top of the residual wax recovery bottle 12, and the top end of the reducing tube 11 is connected to the polishing disc 2 for rapid recovery of residual wax.

[0047] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A silicon wafer wax polishing process, characterized in that: The steps include: S1. Place the polishing sheet on a waxed polishing disc to perform waxed wafer application. Rotate the silicon wafer continuously for 1-60 seconds. Liquid wax is coated on the back surface of the silicon wafer under the action of centrifugal force. S2. Use a combination of physical and chemical cleaning methods to clean the polishing disc. First, clean the polishing disc with a brush and a wax remover, then put it into a cleaning machine with an ultrasonic device for secondary cleaning, and then recycle it after cleaning; S3, by connecting a short reducing tube to the film loading stand, and then connecting the residual wax recovery bottle to the reducing tube, the discharged residual wax can be directly stored in the residual wax recovery bottle in a very short time; S4. RCA cleaning and megasonic cleaning technology are used to clean the surface of the polished silicon wafer.

2. The silicon wafer wax polishing process according to claim 1, characterized in that: In step S2, the residual wax is recovered by a dewaxing agent recovery tank.

3. The process for polishing a silicon wafer with wax according to claim 1, characterized in that: In step S2, the wax remover is sprayed through the wax remover adding tube, and the brush divides the residual wax marks into countless small wax strips when it passes over the surface of the polishing disc.

4. The process for polishing a silicon wafer with wax according to claim 1, characterized in that: The RCA cleaning relies on solvents, acids, surfactants and water to spray, clean, oxidize, etch and dissolve wafer surface contaminants, organic matter and metal ion contamination without destroying the surface features of the wafer.

5. The process for polishing a silicon wafer with wax according to claim 1, characterized in that: The megasonic cleaning technology uses the piezoelectric effect in combination with a cleaning fluid to remove submicron particles and contaminants from a substrate.

6. A silicon wafer wax polishing device, used in the silicon wafer wax polishing process according to any one of claims 1 to 5, characterized in that: The invention comprises a wafer loading seat (1), a polishing disc (2) is installed on the top of the wafer loading seat (1), a polishing sheet (3) is installed inside the polishing disc (2), a turntable (4) is installed on the top of the polishing sheet (3), a silicon wafer (5) is installed on the bottom of the turntable, and the turntable (4) is driven by a motor to rotate, thereby driving the silicon wafer (5) to perform a polishing operation on the surface of the polishing sheet.

7. The silicon wafer wax polishing device according to claim 6, characterized in that: A polishing agent adding pipe (6) is installed on the upper part of the polishing disc (2), a nozzle is installed at the end of the polishing agent adding pipe (6), the outside of the polishing agent adding pipe (6) is connected to the polishing agent storage tank, and the polishing agent adding pipe (6) is a snake neck pipe structure.

8. The silicon wafer wax polishing device according to claim 6, characterized in that: The invention also comprises a cleaning tank (7), wherein a cleaning disc (8) is arranged at the upper part of the cleaning tank (7), a brush (81) is installed at the bottom of the cleaning disc (8), the cleaning disc (8) is supported by a bracket (9), a motor is installed in the middle of the top of the cleaning disc (8), the motor drives the cleaning disc (8) to rotate, and a screw rod assembly is vertically installed on the bracket (9), and the screw rod assembly drives the cleaning disc (8) to be raised and lowered.

9. The silicon wafer wax polishing device according to claim 8, characterized in that: A dewaxing agent adding pipe (10) is installed on one side of the upper part of the cleaning tank (7), a nozzle is installed at the upper end of the dewaxing agent adding pipe (10), and a dewaxing agent storage tank (11) is connected to the lower end of the dewaxing agent adding pipe (10), and the dewaxing agent adding pipe (10) is a snake neck pipe structure.

10. The silicon wafer wax polishing device according to claim 6, characterized in that: A residual wax recovery bottle (12) is arranged inside the film loading seat (1), the top of the residual wax recovery bottle (12) is connected to a reducer (11), and the top end of the reducer (11) is connected to the polishing disc (2).

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