MIR-based in-situ measurement of Silicon crystal-melt interface

Abstract

The project explores the a proposed MIR-based measurement system for measuring the deflection of the interface between the crystal and melt during production of mono-crystalline Silicon in the Czochralski process. The absorption spectrum is modeled and the specific absorption for a select set of wavelengths is estimated for temperatures approching 1687K. It was estimated that the intrinsic absorption edge, corresponding to a photon wavelength of 1.107um had an absorption coefficient of 1.56e+4 cm-1, while a wavelength of 2.55um had an absorption of 13.76 cm-1. The optimum wavelength for transmittance through Silicon at 1687K was determined to be 2.16um for extrinsic material doped with 2.8e+16 cm-3 concentration of Boron. The measurement using a transmittance scan with a wavelength of 2.55um of a three samples yielded results with a maximum deviation of 8.8% from the true deflection. A ray tracing method based on reflecting the beam of the interface yielded a maximum error of 11.6% with a mean result deviating by 1.6%.