High-K/metal gate technology, introduced by Intel, to replace the conventional oxide gate dielectric and polysilicon gate has truly revolutionized transistor technology more than any other change over the last 40 years. First introduced at the 45nm node, this complex process has now been adopted for advanced nodes. The capability of picosecond ultrasonic measurements (PULSETM) for in-line monitoring of High-K/metal gate structures was evaluated and the benefits of this technology for measuring various structures including SRAM, pad array, and line array key with excellent correlation to cross sectional TEM was demonstrated. We have shown that, only a direct measurement of SRAM structures can represent true variations of the metal gate height due to CMP process and is strongly affected by the design and layout of pattern, including pattern density, dummy design, and spacing. The small spot, non-contact, non-destructive nature of this technology allows for in-line measurements directly on these structures with excellent repeatability at a very high throughput.
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 . 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.