Application of Laser Beams to Nondestructive Measurement of Residual Stress in Semiconductor Devices.

Abstract

Effective methods of applying laser beams to measure residual stress in semiconductor devices are briefly presented. Surface curvature measurement of a film-deposited substrate is known to be effective for measuring internal stress of thin films. Oblique Incidence Ellipsometry using a rotating analyzer can detect residual stress in polymer and glass films. Since polarization of an incident beam varies with the internal stress of the film, residual stress in the film can be measured by detecting the phase shift of the transmitted or reflected beam. The minimum resolution of this stress measurement using this method is about 10 kPa. Microscopic Raman spectroscopy is useful for measuring residual stress in semiconductor substrates such as silicon and gallium-arsenide. The peak position of the Raman spectrum shifts linearly with an applied uni-axial stress, and the stress sensitivity of this method is about 250 MPa/cm-1. Thus residual stress in the semiconductor substrates can be determined by detecting the shift in the spectrum. The minimum laser beam spot size obtained in this report was about 0.4 μm when a ultraviolet laser beam with 300-nm wavelength was used.