Measuring the Thickness of Oxide on Polysilicon using Ultraviolet Ellipsometry

Abstract

The thickness of silicon dioxide on polycrystalline silicon is measured using ultraviolet (UV) ellipsometry (with a quartz halogen light source with wavelength 4050 Å). The UV allows the problem to be treated as a single film on a bulk material, and hence greatly simplifies the calculation. Two applications of oxide growth on polycrystalline silicon as sacrificial and nonsacrificial etch masking layers are used to illustrate the method. Initial oxide thickness and oxide losses after relevant post‐processing were measured for 1.8, 4, and 8 kÅ of boron doped polysilicon. Although the effect of reactive ion etching (RIE) damage on ellipsometric parameters has been reported previously for single crystal silicon, we report the first optical evidence of RIE damage to polycrystalline silicon.