Fast and accurate scatterometry metrology method for STI CMP step height process evaluation

At the 28nm node using 300mm wafers, oxide step height in STI CMP transient gate after-etch inspection (TG AEI) wafers is a critical parameter that affects device performance and should be monitored and controlled. For production process control of this kind of structure, a metrology tool must utilize a non-destructive measurement technique, and have high sensitivity, precision and throughput [1]. This paper discusses a scatterometry-based measurement method for monitoring critical dimension step height in STI CMP instead of traditional measurement methods such as atomic force microscopy (AFM). The scatterometry tool we used for our investigations was the KLA-Tencor SpectraShape 8810, which is the most recent model of the spectroscopic critical dimension (SCD) metrology tools that have been implemented in production for process control of TG AEI structures. AFM was used as a reference metrology technique to assess the accuracy performance of the SpectraShape8810. The first objective of this paper is to discuss the best azimuth angle and floating parameters for scatterometry measurement of the step height feature in TG AEI wafers. Second, this paper describes the tool matching performance of SpectraShape 8810 and correlation to AFM determined using a DOE of TG AEI wafers.