Electrically modulatable extended light source and a measurement device for characterizing a semiconductor including one such source

Abstract

A light source for injecting excess carriers into a semiconductor wafer, fully illuminating a surface of the wafer. The source includes at least one set of point sources which are spaced apart at regular intervals along the X and Y axes, such that the source emits a monochromatic beam of a size that is at least equal to that of the semiconductor wafer surface to be illuminated. Each of the point sources is sinusoidally modulated by a common electrical modulator, the distance between two point sources and the distance between the source and the semiconductor wafer surface to be illuminated being selected such that the monochromatic light beam uniformly illuminates the surface.

1 . A measurement device comprising a light source for determining a volume lifetime τb and a rate of recombination S of a semiconductor wafer, the device further comprising:
 an electrical modulator having an output to energize the light source and a reference signal output of identical frequency to a modulation frequency f of said light source, 
 a probe source, to create a wave field, the waves emitted irradiating a nonilluminated surface of said semiconductor wafer , 
 a waveguide or an antenna configured to channel the waves emitted onto the nonilluminated surface of said semiconductor wafer and the waves reflected to a wave detector, said waveguide or said antenna associated with said wave detector being configured to pick up the signal produced by the waves reflected from said semiconductor wafer thus excited, 
 a control unit receiving the reference signal coming from one of the two outputs of the electrical modulator and the reflected wave signal at the output of said detector, and measuring a shift Δφ between the light source and the reflected waves, 
 a processing unit receiving the shift Δφ measured by said control unit to extract at least two parameters of said semiconductor wafer, namely, the lifetime of the minority carriers τb and the rate of surface recombination S. 
 
     
     
         2 . The measurement device per  claim 1 , wherein said light source emits a light beam at a power sufficient for an injection of free carriers at least greater than 10-5 times the doping of said semiconductor wafer of said semiconductor wafer. 
     
     
         3 . The device per  claim 1 , wherein said probe source is a microwave source, working in the X band, to create a microwave field, the microwaves emitted irradiating the nonilluminated surface of said semiconductor wafer. 
     
     
         4 . The device per  claim 1 , wherein said probe wave source is a radio-frequency source, working in a radio frequency spectrum between the VHF band and the X band, the waves emitted irradiating the nonilluminated surface of said semiconductor wafer.