Accuracy of ellipsometric monitoring during growth of semiconductor nanostructures

Abstract

The determination accuracy of the parameters of multilayer structures during their in situ ellipsometric monitoring is analyzed. A qualitative criterion is proposed that makes it possible to evaluate the validity of replacement of the multilayer structure by a certain medium with effective optical constants. According to this criterion, this replacement is possible if the complex reflection coefficients R p, s of the structure satisfy the relation (R p /R s + cos2φ)/(R s + R p cos2φ) = 1, where φ is the angle of incidence of light. It is shown that, for structures consisting of layers with a high refractive index, this condition is implemented with a high accuracy. This proves that, upon the successive solution of the ellipsometry problem for layers of this structure, errors are not accumulated. In particular, this inference can be applied to structures based on a cadmium-mercury-tellurium ternary compound.