Method for evaluation of transition region of silicon epitaxial wafer

DETAILED DESCRIPTION In order to solve the problems based on the defects of the conventional methods, the present invention has as its object, the provision of a method for evaluating, in a short time and in a nondestructive way, an active impurity contained in a single crystal substrate intermixed at high concentrations into an epitaxial growth layer in the vicinity of the growth interface between the epitaxial growth layer and a single crystal substrate of epitaxial wafer, by thermal diffusion of the active impurity into the epitaxial growth layer and/or auto-doping.
This is done by measurement of the intensity of the interference fringe when employing a Michelson interferometer and thereby determining the extent of the transition region in thickness.
A more specific object of the invention is the evaluation of the transition region of a silicon epitaxial wafer having a vapor phase growth silicon single crystal layer formed on a silicon single crystal substrate which has a dopant concentration not less than 1.
times.
10.
sup.
18 atoms/cm.
sup.
3.
This can be achieved according to the present invention, by irradiating the surface of a sample of a silicon epitaxial wafer with infrared radiation the wafer having a vapor phase growth silicon single crystal layer formed on a silicon single crystal substrate and a dopant concentration not less than 1.
times.
10.
sup.
18 atoms/cm.
sup.
3, followed by measuring the intensity of interference fringe corresponding to plural optical path differences for light rays reflected by the surface of said wafer and (1) the growth interface between the vapor phase growth silicon single crystal layer and the silicon single crystal substrate and (2) the vicinity of said growth interface.
The method further comprises measurement of the intensity of the interference fringe employing a Michelson interferometer and infrared radiation as light for the measurement.
The waveform of the interferogram signal is obtained, and the extent of the transition region in the epitaxial wafer is determined from the characteristics of the waveform in the side burst region of the interferogram signal