The study of high-sensitive and accurate metrology method by using CD-SEM

Abstract

The earliest semiconductor device manufacturing employed optical microscopes for measurement and control of manufacturing process. The introduction of Critical Dimension Scanning Electron Microscope (CD-SEM) in 1984 provided a tremendous increase in capability for process monitoring and has been the standard for in-line metrology for over 25 years. The advantages of CD-SEM are highly accurate and stable measurement reproducibility at very specific locations throughout the device. The evolution of CD-SEM in Metrology has included improved resolution, development of advanced measurement and pattern recognition algorithms, all required by performance improvement demands from the market. Current conventional metrology using in-line CD-SEM involves measuring about ten points per wafer (one or more points per one chip). At a magnification of over x150k (Field of View is about 1μm²). In contrast, the area of measurement pattern on chip is much larger than the area of CD-SEM measurement (mm² : (on chip) versus μm² : (CDSEM measurement)). This would mean that the result of CD-SEM measurement is influenced by local pattern variation. The very stringent requirements placed on in-line Metrology for the last couple of technology nodes has produced an additional metrology methodology, beyond the CD-SEM, that involves large area measurements with very high precision for the most critical levels. We will refer to this methodology as "Macro Area Measurements". We reported the applicability of using a CD-SEM Macro Area Measurements methodology in SPIE2011 (797124). In the results, we were able to validate a new methodology that we called "Macro Area Measurement" which is demonstrated to successfully detect small process variations with the same throughput and reduced damage to the pattern. This time, we investigated the additional applicability of using a CD-SEM Macro Area Measurement methodology in this paper. The areas investigated focused on the following points: 1) Measurement repeatability related to CD-SEM measurement 2) Optimization of the measurement parameters using new function 3) Verification of Macro Area Measurement with a leading -edge device In the results, we are able to validate "Macro Area Measurements methodology which is demonstrated to successfully detect further small process variations with the almost same throughput and reduced damage to pattern.