Theoretical And Experimental Research On The Effect Of Process Parameters On The Lapping Process

Lapping is one of the most important procedures in semiconductor wafer’smanufacturing, which is used to remove subsurface damage caused by last machiningprocess and produce the required surface smoothness and flatness. However, due to thecomplexity of lapping process, there are significant improvements still to be made suchas material removal mechanism (MRR), process parameter control, and onlinemonitoring of lapping process, etc. With the development of computer technology, FiniteElement Method (FEM) simulation has become an effective way to understand andoptimize machining processes. In the present paper, the simulation analysis andexperimental method are combined to study the effect of abrasive particle’s kinematicalbehavior on the lapping process.Firstly, the present research status of material removal mechanism, contact theoryand acoustic emission testing technology of lapping process at home and abroad areintroduced systematically based on the research background and significance of lappingtechnology. On the basis of previous researches, theoretical derivation are carried out onthe basic theory of lapping processing such as the lapping force, MRR, stress distributionand the contact mechanics, etc.Secondly, a simplified two dimensional finite element model of lapping process isdeveloped using the implicit software MSC. Marc. The effect of different lapping processconditions on the movement type of individual particles and surface topography of theworkpiece during the lapping process are investigated by FEM simulation. Moreover, twodifferent contact patterns between the abrasive particle and workpiece, rolling contactpattern and sliding contact pattern are simulated. The force of abrasive particle, frictioncoefficient and stress distribution in workpiece of these two different contact pattern arecompared.At last, an online testing platform of lapping process is developed based on the lapping&polishing machine, which is mainly constituted by the lapping plate finishingunit, lapping fluid supply unit, detection unit, pressure adjusting unit and lappingprocessing unit these five parts. The working principles of each component unit areintroduced in detail. Based on the established testing platform, the lapping experimentalscheme is designed. The specific experimental procedures and matters needing attentionare also emphasized. Lapping experiments are carried out under different lappingconditions. The effect of different lapping process conditions on the MRR, surfacetopography of the workpiece and measured acoustic emission signals during the lappingprocess are investigated. The material removal process and mechanism of single-crystalsilicon during the lapping process are discussed.