Study On Control Method And System Of Grinding Force Of Self-rotating Precision Grinding Process

There exists a higher demand on grinding technology as wafer's size is increasing. Currently, advanced grinding technologies and equipments for wafer are monopolized by developed countries and multinationals, and this has severely restricts the development of China's semiconductor manufacturing. Domestic scholars carry out some relatively detailed researches on processing technology of lager wafer, which mainly focus on the aspect of mechanism of removing grinding while little on controlling grinding force.Grinding force is an important factor in the process of grinding, and its magnitude will directly influence the surface quality of wafer, so it's necessary to conduct a real-time control on grinding force. Firstly, this paper analyzes the factors influence grinding force, and the main ones are the down feed rate of the grinding wheel, the rotational speed of the grinding wheel, the rotational speed of the wafer and the grain size of the grinding wheel. Then it proposes an idea of controlling grinding force by regulating the down feed rate of the grinding wheel that affects grinding force greatly. With the characteristic of wafer self-rotating grinding, pros and cons of commonly-used methods are analyzed and compared. After that it selects out the appropriate methods and works out the grinding control strategy offers in phases, meanwhile the overall program of grinding control system has been designed. On the basis of those, with the function desire of the control system, analyze, design and choose models of every part of the system. A close-loop simulation was made by putting the open-loop transfer function and the controller together. At last, the software of the control system has been programmed in LabVIEW environment, and a grinding force control method verifying system is used to inspect the practicability of the system. The main researches and achievements are the follows:(1)Grinding force can be controlled by adjusting the down feed rate of the grinding wheel, and the surface quality of the wafer will be improved.(2)According to the demand of the grinding force control, the system was designed, modeled and got the open-loop transfer function of the system.(3)The ordinary control methods were compared, and the Fuzzy-PID method was chosen to make a closed-cycle simulation. The result shows that performance can meet the system's needs.(4)The software was compiled by the use of LabVIEW, which realizes the grinding force collection and display, and the control of the down feed rate of the grinding wheel.(5)The hardware was built, and verified the effectiveness of the grinding force control system.