Scanning Surface Photovoltage Microscopy (SSPVM) for Stress Analysis in Nanoscale CMOS Devices

Mechanical stress plays a pivotal role in nanoscale CMOS device performance, influencing carrier mobility and thereby altering electrical characteristics. While conventional techniques such as micro-Raman spectroscopy, nano-beam diffraction, and convergent beam electron diffraction are effective, they are limited by spatial resolution or lack in-situ measurement capability for production devices. This paper introduces Scanning Surface Photovoltage Microscopy (SSPVM), a novel high-resolution technique capable of mapping local mechanical stress in semiconductor devices. SSPVM uses modulated, p-polarized laser illumination from orthogonal directions beneath an AFM probe tip to detect stress-induced optical anisotropy via surface photovoltage differences (DSPV). The method was validated using indented silicon arrays and CMOS diode structures, demonstrating sensitivity to stress distribution with nanometer-scale resolution. While the current setup shows promise for SPV measurements, improvements are required for robust DSPV sensitivity. This technique offers a non-destructive, in-situ approach to evaluate stress in advanced semiconductor devices, addressing critical gaps in current stress measurement metrology.