The effect of underlying oxide layer thickness on in- process monitoring for polycrystalline silicon deposition

Abstract

An in-process thickness monitoring system for polycrystalline silicon film growth using a helium-neon visible laser (wavelength λ = 6328 Å) is devised. Using this system, deposition can be terminated when the desired film thickness is obtained. It is found that if the thickness of an underlying oxide layer is less than about 1000 Å then the thickness of the layer can be exactly determined during deposition by measuring the first minimum point of an interference pattern. It is also found that when the thickness of the layer is increased to more than about 1000 Å the first minimum disappears. Using this method the range in which the thickness of the oxide layer can be determined is about 500–1000 Å.