The Application Study Of Selective Epitaxy Growth On Lithography Overlay

Semiconductor integrated circuit chip is nucleus device of electronic product.With the more requirements for electronic product's performance and volume,more satisfaction for semiconductor chip needs to be achieved.In order to improve Semiconductor technology,it not only needs to restrict and improve the process flow,but also make wafer substrate preparation better.Only in this way the expected performance will be realized.Epitaxy technology,a kind of substrate preparation technology,has been growing up in recent 20 years.It can not only provide pure monocrystalline silicon layer,but also dope precisely according to the technological requirements,and improve the performance.Introducing epitaxy technology will increase the cost,but compared with its major advantage and merit,cost increasing is negligible.However,epitaxy technology will lead to the inevitable defect of pattern shift.Due to anisotropy of crystallography,epitaxial layer growth will cause the deviation of substrate pattern,and pattern overlay symbol will move accordingly,which may lead to the deviation of following lithography overlay process between pattern mask center and actual mask center,resulting in the deviation of actual circuit location from designed process flow location,so that it may affect the performance of semiconductor integrated circuit.The thicker epitaxial layer is,the more pattern shifts.How to control and resolve those demerits will be the key points to improve the semiconductor integrate circuit.According to experimental research,Selective Epitaxy process was introduced to solve the problem which makes following lithography overlay location difficult due to pattern shift.And multiple experiments were done to check the influence of reaction temperature,pressure intensity and gas flow rate on the growth rate of Selective Epitaxy.Finally critical point of growth rate was determined.Within the critical point,only non-mark pattern area will grow Epitaxy layer and overlay pattern area will not grow Epitaxy layer during the whole Epitaxy process,so that non-deviation of overlay could be realized.In that way following lithography overlay center will be still within substrate symbol center to ensure correct process design location in following circuit processing,and the function and yield rate of products will be improved.