Light irradiation type heat treatment apparatus

Abstract

A light diffusion plate made of quartz and provided with a plurality of recessed spherical surfaces is placed on an upper chamber window so as to be in opposed relation to a central portion of a semiconductor wafer. Flashes of light emitted from flash lamps and passing by the side of the light diffusion plate impinge upon a peripheral portion of the semiconductor wafer. On the other hand, flashes of light emitted from the flash lamps and entering the light diffusion plate are diverged by the recessed spherical surfaces. Part of the light entering the light diffusion plate is diffused toward the peripheral portion of the semiconductor wafer. As a result, this increases the amount of light impinging upon the peripheral portion of the semiconductor wafer, and decreases the amount of light impinging upon the central portion of the semiconductor wafer. Thus, the in-plane uniformity of an illuminance distribution on the semiconductor wafer is increased.

What is claimed is: 
     
         1 . A heat treatment apparatus for heating a substrate by irradiating the substrate with light, comprising:
 a chamber for receiving a substrate therein;   a holder for holding said substrate in said chamber;   a light irradiation part provided on one side of said chamber and for irradiating said substrate held by said holder with light; and   a light diffusion plate provided between said holder and said light irradiation part and having a size smaller than that of said substrate as seen in plan view, said light diffusion plate being disposed so that the central axis of said light diffusion plate coincides with the central axis of said substrate held by said holder, said light diffusion plate being provided with a plurality of recessed curved surfaces.   
     
     
         2 . The heat treatment apparatus according to  claim 1 , wherein
 said curved surfaces are spherical surfaces.   
     
     
         3 . The heat treatment apparatus according to  claim 2 , wherein
 said spherical surfaces have a radius of curvature increasing from the center of said light diffusion plate toward a peripheral portion thereof.   
     
     
         4 . A heat treatment apparatus for heating a substrate by irradiating the substrate with light, comprising:
 a chamber for receiving a substrate therein;   a holder for holding said substrate in said chamber;   a light irradiation part provided on one side of said chamber and for irradiating said substrate held by said holder with light; and   a light diffusion plate provided between said holder and said light irradiation part and having a size smaller than that of said substrate as seen in plan view, said light diffusion plate being disposed so that the central axis of said light diffusion plate coincides with the central axis of said substrate held by said holder, said light diffusion plate being provided with a plurality of protruding curved surfaces.   
     
     
         5 . The heat treatment apparatus according to  claim 4 , wherein
 said curved surfaces are spherical surfaces.   
     
     
         6 . The heat treatment apparatus according to  claim 1 , wherein
 said light irradiation part includes a plurality of flash lamps arranged in a plane.