Surface Measurement of GLSI Wafer with Copper Interconnects after CMP

Abstract

Chemical mechanical polishing (CMP) is the best global planarization technology of GLSI process. After CMP process, there may appear large roughness, micro scratch, dishing pit, erosion pit, with-in-wafer-non-uniformity (WIWNU), organic contamination, particles and metal ions pollution on wafer with copper interconnects. Surface measurement of CMP process on the wafer mainly involves the test of roughness, defects and the contaminations. Atomic force profiler (AFP) combined with the resolution of the AFM and long-range-scan ability of the steps instrument (100 mm), is suitable for CMP process which needs to measure both the planarization of long-range scanning and tungsten plug and copper interconnects with high resolution imaging. Optical detection technology combined with the advantages of dark and bright view detection is suitable for detection of particles, crystal originated pits (COP), defects, etc. The time-of-flight static secondary ion mass spectrometry (TOF-SIMS) and total reflection X-ray fluorescence (TXRF) are applicable to detect metal ions. The selection and use of advanced data analysis theory and method can help to improve the speed of analysis and to find the main factors of influence surface quality. Pareto diagram analysis is very beneficial for study polishing effects and the main reason of the surface state for Cu-CMP wafer. Nine sampling method and five sampling method fit to analysis the uniform surface distribution, on the contrast isometric sampling can reflect the distribution of the surface state along the radius difference.