Improvement of optical method of oxygen-in-silicon characterization and design consideration on measuring setup for detailed nondestructive mapping of interstitial oxygen

摘要

Under the today's tendency of progressive growth of integration level and diminishing of the basic element size of microelectronic devices, the significance of control of spatial distribution of defect-inducing impurities during device processing treatments increases. One of the most important impurities for silicon microelectronics is oxygen, which already presents in the initial Czochralski-grown silicon. Existing standard optical methods of measuring interstitial O-in-Si content based on analysis of silicon wafer's transmission spectra on the IR optical band of ～ 9 μm doesn't provide the desired degree of spatial resolution. The purpose of this work is to modify measuring method in such a way to make it possible for one to obtain, in relatively fast manner, oxygen distribution "map" over the wafer's area, with spatial resolution up to 30..50μm. The work describes the approach to measuring setup construction, which provides oxygen distribution control in silicon wafers containing O in concentration lying between 10~(17)...3*10~(18) cm~3 with the accuracy of 5% and with the above localization degree. Different realizations of the optical source, projection optics, detector and signal processing system are discussed, and the best choice is grounded. Presented are the technical estimations showing the evidence for the measuring setup to provide the desired features when tunable laser diode is used as a light source along with the special parabolic collimator, cylindrical projection optics and commercially available time-delay-and-integration CMT LWIR detectors.