Design And Implementation Of Wafer Thin Film Stress Measurement System

For a long time,my country has lagged behind the world's leading level in the field of chip manufacturing and measurement.Wafer film stress measurement system is used to measure the coating quality of wafer surface,which plays a vital role in the chip manufacturing process.my country's demand for wafer thin film stress measurement systems basically depends on imports.There are two problems in the actual use process:First,the equipment debugging and use procedures of the measurement system are too cumbersome,which affects production efficiency.Second,the accuracy of the measurement results is low,and the measurement repeatability cannot be guaranteed.Most importantly,in today's international technological competition,the import of the measurement system has become more and more difficult,which is obviously not conducive to the development of my country's chip manufacturing industry.In order to solve the above problems,based on the needs of related high-tech enterprises,this paper designs and implements a wafer thin film stress measurement system based on laser measurement technology.The main contributions and innovations of this paper are as follows:(1)The stable control of the motion motor of the wafer thin film stress measurement system is realized.Aiming at the vibration problem of the motion motor of the measurement system,a motor adaptive and stable motion control system based on vector control technology is designed and implemented,which effectively reduces the impact of vibration and unstable running speed on the measurement results during the start and stop of the motion motor.(2)The high-precision sampling of the photoelectric position-sensitive detector in the wafer thin film stress measurement system is realized.According to the laser measurement principle and calculation formula of wafer thin film stress,the peripheral high-precision op amp and analog-to-digital conversion circuit of the photoelectric position sensitive detector are deduced and designed.The output of the circuit is directly input to the calculation relationship of the laser measurement,which not only simplifies the calculation process of the wafer film stress,but also ensures the accuracy of the data collected by the detector.(3)The automatic compensation of the wafer film stress measurement system error is realized.A fitting coefficient error compensation algorithm is proposed to improve the accuracy and repeatability of the measurement results,aiming at the structural errors of the system equipment,the precision errors of the measuring elements,the errors of the measuring optical path lengths and the errors caused by environmental factors.At the same time,the error compensation automatic correction function is designed and realized,which greatly reduces the debugging complexity of the error compensation coefficient and greatly improves the work efficiency.The visualization of the coating features on the wafer surface of the wafer thin film stress measurement system is realized.This paper designs and realizes the visualization of wafer surface measurement data,and proposes the calculation relationship of wafer surface curvature and the change relationship curve of the position offset of the laser reflection point measured on the photoelectric position sensitive detector.In the measurement data curve graph on the visual interface,the coating characteristics of the wafer surface can be directly reflected,which makes the measurement results of the wafer thin film stress more realistic.