Autofocus for high power laser diode based annealing system

Abstract

Apparatus for thermally processing a substrate includes a source of laser radiation comprising a plurality diode lasers arranged along a slow axis, optics directing the laser radiation from the source to the substrate, and an array of photodetectors arranged along a fast axis perpendicular to the slow axis and receiving portions of the laser radiation reflected from the substrate through the optics.

1 . Apparatus for thermally processing a substrate, comprising:
 a source of laser radiation comprising a plurality of diode lasers arranged along a slow axis;   optics directing said laser radiation from said source to said substrate as a line beam having a long dimension along a slow axis and a short dimension along a fast axis, and scanning apparatus for scanning said line beam along said fast axis relative to said substrate; and   an array of photodetectors arranged along said fast axis and receiving portions of said laser radiation reflected from said substrate through said optics.   
   
   
       2 . The apparatus of  claim 1  wherein said plurality of diode lasers comprises parallel rows of diode lasers along said slow axis. 
   
   
       3 . The apparatus of  claim 1 , further comprising:
 a translation mechanism for varying a distance between (a) said substrate and (b) said optics; and   a controller receiving an output of said array of photodetectors and controlling said translation mechanism in response to said output to focus said laser radiation on said substrate.   
   
   
       4 . The apparatus of  claim 1 , further comprising a single-axis light pipe arranged between said source and said substrate for homogenizing said beam along said slow axis. 
   
   
       5 . Apparatus for thermally processing a substrate, comprising:
 a source of laser radiation directed toward said substrate, said source comprising a plurality of lasers arranged along one or more rows parallel to said slow axis;   optics directing said laser radiation from said source to said substrate as a line beam having a long dimension along a slow axis and a short dimension along a fast axis, and scanning apparatus for scanning said line beam along said fast axis relative to said substrate; and   an array of photodetectors arranged along said fast axis and receiving portions of said laser radiation reflected from said substrate through said optics.   
   
   
       6 . The apparatus of  claim 5  wherein said plurality of diode lasers comprises parallel rows of diode lasers along said slow axis. 
   
   
       7 . The apparatus of  claim 5 , further comprising:
 a focus mechanism for varying a distance between (a) said substrate and (b) said optics; and   a focus controller receiving an output of said array of photodetectors and controlling said translation mechanism in response to said output.   
   
   
       8 . The apparatus of  claim 5 , further comprising a single-axis light pipe arranged between said source and said substrate for homogenizing said beam along said slow axis. 
   
   
       9 . The apparatus of  claim 7  wherein said output of said array of photodetectors comprises a fast axis profile of light distribution. 
   
   
       10 . The apparatus of  claim 9  wherein said controller is adapted to respond to said fast axis profile to control said focus mechanism so as to maintain an aperture size indicated by said fast axis profile at or near an aperture size corresponding to said plurality of lasers. 
   
   
       11 . The apparatus of  claim 9  wherein said controller is adapted to compare said fast axis profile with predetermined fast axis profile models, and cause said focus mechanism to either increase of decrease said distance in response to said comparison.