Patent ID: 6153444
Filing Date: 2000-11-28
Classification: G01R,H01L

Abstract:
A method of simultaneously measuring a free carrier concentration and a depthwise position which has said free carrier concentration in a layer of a semiconductor, comprising the steps of:(a) irradiating said layer of said semiconductor with light having at least a frequency band which causes light absorption by said free carriers in said semiconductor;(b) optically measuring light reflected from said layer of said semiconductor; and(c) determining said carrier concentration and said depthwise position from the measurement in step (b),wherein in the steps (b) and (c) a reflection amplitude ration (tan .PSI.) and a phase (.DELTA.) of a complex amplitude reflectance ratio (.rho.) are measured at several points with a plurality of wavelength by ellipsometry, and;the free carrier concentration (N.sub.c), the thickness (d) and the damping constant (.lambda..sub.pl) are determined by a curve fitting method;the curve fitting method including:obtaining a complex amplitude reflectance ration (.rho.m) determined by the measured reflection amplitude ratio (tan .PSI.) and phase (.DELTA.);obtaining a complex amplitude reflectance ratio (.rho.c) determined by selecting appropriate values of the free carrier concentration (N.sub.c), a thickness (d) which represents the depthwise position and a damping and a damping constant (.lambda.pl);determining the residual sum of squares of each of the real part and the imaginary part of each of the complex amplitude reflectance ratios (.rho.m) and (.rho.c) as an error evaluation function, andconsidering the free carrier concentration (N.sub.c) the thickness (d) and the damping constant (.lambda.pl) when an error evaluated by the error evaluation function is lower than a permissible value as measurements.