A small notch or foot existing at the bottom of a polysilicon gate is a common issue for etching processes. The small notch or foot could have a major impact on the length of the polysilicon gate, and the performance of the device would then be impacted significantly, especially for cutting-edge devices. This paper demonstrates the capability of a spectroscopic ellipsometry based profile technology, SpectraCD, as a new metrology tool to monitor polysilicon gate process at 130 nm and 90 nm nodes. Firstly, the capability of SpectraCD as a metrology technology was studied, including dynamic precision and CD correlation. Dynamic precision in the range of 0.1~0.4 nm was demonstrated repeatedly in this study. CD correlation with CDSEM also showed a very linear result. R-squared values of ~0.99 are presented. Secondly, by comparison with images from cross-sectional SEM (XSEM) and TEM (XTEM), it has been proved in this study that SpectraCD can consistently flag different profile excursions of polysilicon gate, e.g., small notching, footing, or undercut. The size of the footing or notch reported by SpectraCD shows a linear correlation with the size extracted from XTEM images, which demonstrates quantitatively SpectraCD capability for detecting profile excursions. Finally, linear correlation between the bottom CD from SpectraCD and the gate lengths determined from electrical test (Lcap) will be presented.
Faster time to results is becoming more and more critical for chip makers to build up the production monitoring capability on advanced process development. Especially for SiGe's process, which uses SEG
process by adding germanium. SiGe products provide higher frequency and lower power dissipation than traditional Si based products due to lower energy band-gap. SiGe process can be integrated to current
semiconductor process easily with lower cost comparing to GaAs process. The combination of HBT and CMOS is excellent on wireless and optical fiber communication application. This application introduce a SiGe's in-line measurement method by using spectroscopy ellipsometer, which offers a non-destructive and ultra fast measurements than typical metrology tools, such like RBS, XRD or SIMS, on both box profile and gradient profile of varied Ge concentration of the films.
By characterizing the different RI interval of the dispersion curves of SiGe-films, single or multi layers, through spectroscopy ellipsometer, we may estimate the film thickness and the peak concentration of germanium. A correlation of this in-line method with off-line method, such as XRD or SIMS, is provided through different RI-intervals of SiGe films as a comparison.
The content of this paper offered experimental measurements data, which is not only on monitor wafers but also on production wafers including different box and gradient profiles of Ge concentration of the SiGe films via spectroscopy ellipsometer.The optical method is highly reducing the fabrication costs and accelerating production yields.