Diffraction Originated Local Heating of Nanometer Scale Device Patterns in Lamp-Based Rapid Thermal Annealing

Abstract

The process results on blanket Si and patterned Si wafers are often very different. Process variations in conventional lamp- based rapid thermal processing (RTP) systems due to pattern size, density and structure dependence under nearly identical process conditions are well known as the pattern effect , but without identifying the root cause. As device dimensions shrink, pattern-induced variability of process results increases which significantly affects the process window, device yield and manufacturability. Understanding the underlying physical causes of the pattern effect is very important to systematically improve device performance, yields and manufacturability. In this paper, the impact of device pattern size and density on process variations in RTP steps was analyzed. According to the analysis, diffraction of light from the periodicity of the nanometer scale device features can result in significant local heating near the critical depths for junctions and contacts.