Full Structure Transistor Process Monitoring of Boron and Germanium in PFET EPI Using in-line XPS

Authored by: Jusang Lee, Ganesh Subramanian, Manasa Medikonda, Hossam Lazkani, Judson Holt, Churamani Gaire, Paul Isbester, Mark Klare | SPIE 2019, February 1, 2019

The epitaxial growth of source/drain structures demands a process with tight control of boron and germanium
composition to ensure consistent device performance. However, in-line monitoring of the epitaxial composition in
FINFET structures has been one of the most difficult challenges for both process development and manufacturing.
Traditional in-line monitoring schemes have relied heavily on critical dimension (CD) measurements, with no
composition information. Instead, composition information was provided by offline analysis techniques such as
secondary ion mass spectrometry (SIMS), which is destructive and does not measure the composition directly on the
FinFET device structure. In this paper, we present results from in-line X-Ray Photoelectron Spectroscopy (XPS)
measurements on FinFET structures. This technique is not only sensitive to individual element abundance but also gives
information related to the local chemical environment. For this application we monitored silicon, germanium, and boron
concentrations in SiGeB EPI source/drain 3D structure without interference from other structural features in the logic
device. The in-line XPS measurement of PFET EPI boron and germanium performed in this way on the full structure
transistor has been demonstrated to correlate with CMOS device performance, thus significantly reducing time to detect
epitaxial composition drift or excursion.
Keywords: In-line XPS, metrology, boron, process monitoring, Epi, germanium, SiGe, FinFETs.