Polishing cloth process optimization method based on differential finishing

Abstract

The invention relates to the technical field of semiconductor manufacturing and precision machining, in particular to a process optimization method based on differential finishing of polishing cloth, and aims to improve finishing flatness and disc type precision of the polishing cloth so as to improve product machining quality. Acquiring current thickness data of upper and lower disc polishing cloth; according to the current thickness data of the upper and lower disc polishing cloth, finishing programs suitable for the upper and lower disc polishing cloth are respectively formulated by combining the factory disc type of the double-sided polishing machine; according to the formulated finishing procedure, finishing the lower disc polishing cloth firstly, and then finishing the upper disc polishing cloth; and after finishing is completed, a certain number of polishing dummy wafers are machined to confirm the finishing effect, machining parameters are adjusted according to the dummy wafer thickness morphology graph, after the finishing effect is confirmed to be qualified, a trial machining stage is started, and after a preset number of polishing products are machined, the machining level of positive wafer specification products is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing and precision processing, and particularly relates to a polishing cloth differential trimming process optimization method, aiming to improve the trimming flatness and disc type precision of the polishing cloth, thereby improving the product processing quality. BACKGROUND

[0002] In the double-sided polishing process, the trimming of new polishing cloth is a key factor determining the subsequent silicon wafer processing level. The traditional trimming method has the following outstanding problems in actual application: first, when the upper and lower polishing cloths are trimmed synchronously, the matching deviation of the upper and lower discs is easily caused due to mechanical transmission error, thereby causing uneven silicon wafer surface removal rate. Secondly, the existing trimming process parameters are often set based on experience, without fully combining the reference disc type data when the equipment is shipped and the real-time monitoring results of the polishing cloth thickness, so that the trimming precision is difficult to meet the high-precision processing demand. For example, when the polishing cloth compression rebound characteristics or local wear difference is not considered, the trimmed disc surface may still have micro undulations. More notably, the industry generally lacks a systematic trimming effect verification mechanism, and usually only judges the trimming quality through simple trial polishing observation, which makes the product pass rate significantly reduced at the initial stage of formal processing, not only causing cost increase, but also seriously affecting production efficiency. In view of these problems, it is urgent to develop a trimming method based on thickness measurement data. SUMMARY

[0003] The present application provides a polishing cloth differential trimming process optimization method, which solves the above problems through step-by-step measurement, differential trimming and effect verification.

[0004] The technical solution of the present application is: a polishing cloth differential trimming process optimization method, comprising the following steps: First step, measuring the cloth thickness before trimming: measuring the thickness of the upper and lower disc polishing cloths to obtain the current thickness data of the upper and lower disc polishing cloths; Second step, developing a trimming program: developing a trimming program suitable for the upper and lower disc polishing cloths according to the current thickness data of the upper and lower disc polishing cloths and the disc type of the double-sided polishing machine shipped; Third step, trimming the lower disc first and then the upper disc: trimming the lower disc polishing cloth first and then the upper disc polishing cloth according to the developed trimming program; Fourth step, processing dummy wafers: after trimming, a certain number of dummy wafers are processed to confirm the trimming effect, the processing parameters are adjusted according to the dummy wafer thickness topography, and after confirming that the trimming effect is qualified, the trial processing stage is entered, and after processing a preset amount of products, the processing level of the finished product is reached.

[0005] As an optimization, in the first step, a thickness gauge is used for measurement to ensure data accuracy.

[0006] As preferred, in the second step, the trimming procedure is calculated according to the thickness difference of the upper and lower polishing cloth combined with the factory disc type, and different trimming methods are set according to the comprehensive disc type, including different rotating speed and pressure.

[0007] As preferred, in the fourth step, the flatness and disc type of the polishing cloth after trimming are verified by processing dummy pieces to ensure the product quality of subsequent formal processing.

[0008] As preferred, in the fourth step, the pre-set amount of polishing products in the trial processing stage are used to further stabilize the surface state of the polishing cloth and improve the processing level of the polishing cloth.

[0009] As preferred, in the first step, the cloth thickness is measured at four directions: 0°, 90°, 180° and 270°, and the inner, middle and outer sides of the polishing cloth are measured at each direction, that is, a single polishing cloth is measured at 12 points, each point is measured three times, the average value is taken and the abnormal value is removed, and the outer point needs to be taken at a certain distance from the edge; after measuring the upper and lower discs, the average value of the inner four directions of the polishing cloth of each disc of the upper disc and the lower disc is taken, and the middle and outer sides are the same.

[0010] As preferred, the factory disc type is the disc type measurement deviation of the inner, middle and outer sides of the upper and lower discs at the factory.

[0011] As preferred, the comprehensive disc type is that the measurement results of the inner, middle and outer sides of each disc are added to the measurement deviation of the corresponding position of the factory disc type, and the values of the inner, middle and outer sides obtained after calculation are the comprehensive disc type of the disc.

[0012] As preferred, in the third step, the trimming method is that the comprehensive disc type of each disc is divided into at least two types: inner high and outer low, and inner low and outer high, and the corresponding trimming procedure is formulated according to the disc type.

[0013] The beneficial effects of the present application are: by systematically improving the trimming process, the polishing quality and production efficiency are significantly improved. In the specific implementation process, first, the cloth thickness data is accurately measured and analyzed, and a differentiated trimming scheme is formulated according to the measured results, so as to realize accurate control of the trimming parameters, thereby effectively reducing the unnecessary trimming times and dummy piece processing times, and reducing the processing cost. The upper and lower discs are independently trimmed, the optimal trimming path and pressure parameters are designed according to the different disc type characteristics of the upper and lower discs, and the best working state of the two discs is ensured. The present application is especially suitable for the precision polishing field of semiconductor wafers, optical glass and other strict surface flatness requirements, and can meet the dual requirements of processing efficiency and surface quality in the current precision manufacturing industry. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is the point position diagram of measuring cloth thickness in the embodiment of the application.

[0015] Figure 2 is the classification diagram of comprehensive disc type in the embodiment of the application. DETAILED DESCRIPTION

[0016] The technical scheme of the application is further specifically described below through examples.

[0017] The embodiment provides a differential finishing polishing cloth process optimization method, which comprises the following operation steps: First step: measuring cloth thickness before finishing, respectively measuring the thickness of the upper disc and lower disc polishing cloth, and obtaining the current thickness data of the upper disc and lower disc polishing cloth. Specifically, a high-precision thickness gauge is used to measure the thickness of the upper disc and lower disc polishing cloth, so as to ensure data accuracy. As shown in the figure, the measurement positions include 0°, 90°, 180° and 270°, and there are three points of inner side, middle and outer side in each direction. There are 12 points in the four directions of each disc, and the average value is taken by measuring each point for three times and eliminating abnormal values. When measuring, the outer side point is 3-4 polishing cloth grids away from the edge, and the example is shown in Table 1. Figure 1 Table 1: Thickness measurement value example 1 The thickness average values of the four directions of the inner side, middle and outer side of the upper disc and lower disc are calculated, and the example is shown in Table 2.

[0018] Table 2: Thickness calculation value example 1 outer middle inner upper disc 825 826 835 lower disc 824 824 825 Second step: making a finishing program, according to the current thickness data (final average value) of the upper and lower disc polishing cloth measured in the first step, combining the disc type of the double-sided polishing machine (the disc type measurement deviation amount of the inner side, middle and outer side of the upper disc and lower disc when leaving the factory, and the example is shown in Table 3), and respectively making a finishing program suitable for the upper and lower disc polishing cloth. Specifically, the measured thickness and the factory disc type deviation amount (provided by the manufacturer) are superimposed to obtain the inner side, middle and outer side three point values (superimposed values), which are used as the comprehensive disc type of the upper and lower disc, and the example is shown in Table 4. As shown in the figure, the comprehensive disc type is classified, and the upper disc is classified into "inner high and outer low" (corresponding to the upper disc finishing 1 in Figure 2 Figure 2 or "inner low and outer high" (corresponding to the upper disc finishing 2 in Figure 2 ), matching different rotating speeds and other finishing parameters, and specifying the corresponding finishing program, and the lower disc is the same.

[0019] Table 3: Disc type example 1 outer middle inner upper disc 1 3 -1 lower disc -1 -8 -13 Table 4: Comprehensive disc type example 1 ​​ outer middle inner upper disc 826 829 834 lower disc outer middle inner upper disc lower disc 823 816 812 Third step: first fix the lower disc, then fix the upper disc, according to the prepared trimming procedure, four trimming grinding wheels are downward, first polish the lower disc, then four trimming grinding wheels are upward, polish the upper disc. The order of first fixing the lower disc and then fixing the upper disc optimizes the trimming stability and reduces the matching deviation caused by synchronous trimming of the upper and lower discs.

[0020] Fourth step: process dummy pieces, after trimming, process 1-2 polishing dummy pieces to confirm the processing data, verify the flatness and disc type of the polishing cloth after trimming, and ensure the quality of the subsequent formal processing products. According to the dummy piece thickness topography, adjust the processing parameters, and after confirming that the trimming effect is qualified, enter the trial processing stage. Normally, about 20 polishing products in the trial processing stage can reach the processing level of the regular piece specification products. The about 20 polishing products in the trial processing stage are used to further stabilize the surface state of the polishing cloth and improve the polishing cloth processing level.

[0021] The embodiment significantly improves the polishing cloth trimming precision and product yield through accurate thickness measurement, comprehensive disc type calculation, step-by-step trimming and effect verification, and is suitable for the field of precise processing of semiconductor wafers and the like.

[0022] The above only describes specific embodiments of the present application, but the structural characteristics of the present application are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present application are covered by the patent scope of the present application.

Claims

1. A method for optimizing the polishing cloth process based on differentiated finishing, characterized in that, The method comprises the following steps: First step, measure the thickness of the polishing cloth before repair: measure the thickness of the upper and lower polishing cloth to obtain the current thickness data of the upper and lower polishing cloth; Second step, develop a repair program: according to the current thickness data of the upper and lower polishing cloth, combine the polishing machine factory disc type, and develop a repair program suitable for the upper and lower polishing cloth respectively; Third step, repair the lower disc first and then the upper disc: according to the developed repair program, repair the lower polishing cloth first, and then repair the upper polishing cloth; Fourth step, process dummy pieces: after repair, process a certain number of dummy pieces to confirm the repair effect, adjust the processing parameters according to the dummy piece thickness profile, and confirm that the repair effect is qualified, then enter the trial processing stage, and process a certain amount of polishing products to reach the processing level of the standard product.

2. The method of claim 1, wherein the method is based on a differential modification polishing cloth process optimization. In the first step, a thickness gauge is used for measurement to ensure data accuracy.

3. The method of claim 1, wherein the method is based on a differential modification polishing cloth process optimization. In the second step, the repair program is calculated according to the thickness difference of the upper and lower polishing cloth combined with the factory disc type to obtain the comprehensive disc type, and different upper and lower repair methods are set according to the comprehensive disc type, including different rotating speed and pressure.

4. The method of claim 1, wherein the method is based on a differential modification polishing cloth process optimization. In the fourth step, the flatness and disc type of the polishing cloth after repair are verified by processing dummy pieces to ensure the quality of the subsequent formal processing products.

5. The method of claim 1, wherein the method is based on a differential modification polishing cloth process optimization. In the fourth step, the preset amount of polishing products in the trial processing stage is used to further stabilize the surface state of the polishing cloth and improve the processing level of the polishing cloth.

6. The method of claim 3, wherein the method is based on a differential modification polishing cloth process optimization. In the first step, the cloth thickness is measured at four positions: 0°, 90°, 180° and 270°, and the inner side, middle and outer side of the polishing cloth are measured at each position, i.e. a single polishing cloth is measured at 12 points, each point is measured three times, the average value is taken and the abnormal value is removed, and the outer side point needs to be taken at a certain distance from the edge; after measuring the upper and lower discs, the average value of the inner side, middle and outer side of each disc is taken, and the same is true for the middle and outer side.

7. The method of claim 6, wherein the method is based on a differential modification polishing cloth process optimization. The factory disc type is the disc type measurement deviation of the inner side, middle and outer side of the upper and lower discs when leaving the factory.

8. The method of claim 7, wherein the method is based on a differential modification polishing cloth process optimization. The comprehensive disc type is: the cloth thickness measurement results of the inner side, middle and outer side of each disc are added to the measurement offset of the corresponding position of the factory disc type, and the three point values obtained after calculation are the comprehensive disc type of the disc.

9. The method of claim 8, wherein the method is based on a differential modification polishing cloth process optimization. In the third step, the repair method is: the comprehensive disc type of each disc is divided into at least two types: inner high and outer low, and inner low and outer high, and the corresponding repair program is developed according to the disc type.

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