Litho Polyimide Layer Resist Reduction And CD Uniformity Research

The semiconductor manufacturing technology has developed for more than fifty years since the first transistor, and now it is still have strong trend situation and continued to follow Moore’s law that the number of transistors on a chip will double about every 18 months. The Semiconductor manufacturing industry will be one of major industries in China in 21st century.Lithography plays an important role in whole semiconductor process. Litho process usually refers to get photolithography masking graphics accurately copy to the photo resist layer above the material. In the integrated circuit manufacturing process need to pass multi lithography, so Litho quality is the key factor of integrated circuit performance, production rate and reliability. Precise control of the thickness CD and overlay is the key to the quality of litho. Based on polyimide resist reduction (for cost down), this thesis introduces method of how to control polyimide layer thickness, CD and overlay parameter, defects reduction and the CD uniformity improvement.On the other hand, with the development of semiconductor production, silicon wafer size becomes bigger and bigger. To guarantee the litho CD uniformity and keep high line yield within the whole wafer, research on the litho uniformity is very important. Because of polyimide’s high viscosity and negative light resistance properties, the line width uniformity and wafer to wafer difference is hard to control. The author also did some research on the exposure and development process to improve the final litho uniformity. This research is mainly based on TEL TRACK (Act-8) development/coating machine and NIKON stepper. Experiments are done on the coater and development process of polyimide layer to find out the best method and parameters to improve resist thickness and CD uniformity.This paper introduces litho technology principle, and then introduces the basic knowledge and technologies of the litho process in IC manufacturing. Secondly, the author detailed discusses the basic principle and systematic control of CD and overlay in litho process, as well as the CD control parameter optimization and improvements on the litho CD uniformity and differences between wafers.