CD control enhancement by laser bandwidth stabilization for advanced lithography application

Abstract

Control of circuit CD in a photolithographic process has become increasingly important, particularly for those advanced nodes below 45nm because it influences device performances greatly. The variation of circuit CD depends on many factors, for example, CD uniformity on reticles, focus, lens aberrations, partial coherence, photoresist performance and LASER spectral bandwidth. In this paper, we focus on LASER spectral bandwidth effects to reduce circuit CD variation. High-volume products of a leading technology node are examined and a novel LASER control function: Gas Lifetime eXtenstion (GLX) is implemented to obtain stable LASER bandwidth. The LASER bandwidth variation was stabilized by changing laser F2 gas concentration through advanced control algorithm and signal process techniques. Product photo-pattern CD variation and device electrical performances will be examined to confirm the benefits of the LASER bandwidth stabilization.