Structural Design And Key Technology Study On Single-sided Polishing Machine

Single-sided polishing machine is an important equipment for processing laser crystal,sapphire substrate,silicon wafer and other substrates.The surface shape accuracy of polishing pad is an important parameter affecting the processing quality of single-sided polishing machine.The in-situ measurement and conditioning technology of polishing pad surface shape is an important method to improve the surface shape accuracy of polishing pad.There are some problems in the existing measurement and conditioning technology of polishing pad surface shape,such as dependence on off-line measurement,large measuring equipment,small measuring range,dependence on experience,low accuracy and efficiency of conditioning.In view of the above problems,considering the requirements of high quality and high efficiency polishing of substrates,the structure design of single-sided polishing machine is carried out,and the in-situ measurement and conditioning technology of polishing pad surface shape is studied.The details are as follows:(1)In order to satisfy the requirements of polishing process for 150 mm-diameter substrates and the function of in-situ measurement and conditioning of polishing pad surface shape,the overall design proposal of the single-sided polishing machine is proposed,which includes the overall structure,working flow and design parameters.Based on the working principle and structure characteristics of the polishing machine,in-situ measurement and conditioning technology of polishing pad surface shape is proposed;(2)In order to achieve high-precision measurement of the polishing pad surface shape,it is confirmed that the measurement error mainly comes from the parallelism error between the guide rail and the reference plane and the straightness error of the guide rail.An error correction strategy based on the adjusting sheet and Z-direction compensation is proposed.In order to achieve the deterministic conditioning of polishing pad surface shape,a theoretical model of in-situ conditioning of polishing pad surface shape is established,and the numerical simulation of the material removal distribution of the polishing pad is carried out.The simulation results show that: in the conditioning area,the removal amount first increases and then decreases along the radial direction of the polishing pad,and the removal amount increases with the increase of the speed ratio of the conditioning disc to the polishing pad,and the removal amount decreases with the increase of the center distance between the conditioning disc and the polishing pad;(3)According to the overall design proposal,the structure design of single-sided polishing machine is carried out,and the key structure is analyzed by finite element method.The results of static analysis show that the z-direction position of the measuring and conditioning unit at different radial positions will change by 1.40 μm under the influence of gravity,accounting for 14% of the measurement error.The results of modal analysis show that the lowest frequency of the first 6 modes is 149.48 Hz,which is higher than the frequency of each motor,so resonance is difficult to happen;(4)In the radial range of 300 mm,the parallelism error is corrected from 44 μm to 16 μm by inserting adjusting sheet,and then the straightness error is corrected from 23 μm to 6 μm by Z-direction compensation.Finally,the in-situ measurement accuracy of the polishing pad surface shape reaches 10 μm,which is consistent with the design parameter.The results of the surface profile measurement of the same part in CMM and in-situ measuring equipment are compared.The maximum measurement error is 6 μm,which verifies the measurement accuracy of the in-situ measuring equipment.And the conditioning experiment results of polishing pad surface shape show that the maximum deviation between the actual removal and the theoretical removal is 22.5%.Based on the above research,the structure design of single-sided polishing machine for150 mm-diameter substrate is completed,and the function of in-situ measurement and conditioning for polishing pad surface shape is realized.It is of great significance to the development of substrate polishing technology.