Method and device for determining defects within a crystallographic substrate

A method for determining defects within a crystallographic substrate comprising the steps of:

• radiating a crystallographic semiconductor substrate with beams of monochromatic radiation having different photon energies to produce a respective plurality of reciprocal photovoltages;
• detecting said plurality of photovoltages as a function of respective plurality of reciprocal absorption coefficients;
• mapping a set of observed points corresponding to said plurality of photovoltages as a function of respective said plurality of absorption coefficients;
• computing a least square correlation factor between said set of observed points and a sloped line, comprising:
• obtaining a set of expected points along said sloped line for each of said plurality of photovoltages;
• calculating a plurality of differences between each said expected point and corresponding said observed point, dividing each said difference by a scaling factor to obtain a scaled difference less than one, squaring each said scaled difference to obtain a scaled squared difference, and adding said scaled squared difference for each of said plurality of differences to obtain a squared sum totaling less than one;
• taking the square root of said squared sum to obtain a residual least square correlation factor;
• subtracting said residual least square correlation factor from one to produce said least square correlation factor;
• and
• ascertaining the presence of defects within said semiconductor substrate based upon the magnitude of said least square correlation factor being less than a pre-determined amount.

A device for determining defects within a semiconductor substrate comprising:

• a light source adapted to produce a plurality of light beams at dissimilar wavelengths;
• a housing connected to said light source and capable of movement across an upper surface of a semiconductor substrate, said housing is adapted to receive a fiber optic cable containing said plurality of light beams and further adapted to house a photodetector for producing a respective plurality of reciprocal photovoltages responsive to said light beams directed upon said upper surface;
• a lock-in amplifier connected to said housing and said light source for locking in said photovoltages with phase of respective light beam wavelengths;
• a data processor connected to said lock-in amplifier for (i) compiling a set of expected points upon a straight line, (ii) mapping a set of observed points corresponding to said plurality of photovoltages, (iii) computing a least square correlation factor between said set of observed points and respective said set of expected points, and (iv) ascertaining the presence of defects within said semiconductor substrate based upon the magnitude of said least square correlation factor being less than a pre-determined amount.