Light irradiation type thermal processing apparatus

A thermal processing apparatus to heat a substrate by irradiating light to said substrate, comprising:

• a light source consisting of a plurality of flash lamps arranged in a plane;
• a hold element to hold a substrate at a location below said light source;
• and
• a diffusion plate that is disposed between said light source and a substrate held by said hold element such that they are substantially parallel with one another, said diffusion plate diffusing light emitted from each of said plurality of flash lamps and directing it to said substrate, wherein
• in said diffusion plate, the light transmittance of a lamp corresponding part located in a vertical immediate downward direction of each of said flash lamps is lower than the light transmittance of an inter-lamp corresponding part located between said lamp corresponding parts adjacent to each other.

A thermal processing apparatus to heat a substrate by irradiating light to said substrate;

• comprising:
• a light source comprising a plurality of flash lamps arranged in a plane;
• a hold element to hold a substrate at a location below said light source;
• and
• a diffusion plate that is disposed between said light source and a substrate held by said hold element such that they are substantially parallel to one another, said diffusion plate diffusing light emitted from each of said plurality of flash lamps and directing it to said substrate;
• wherein in said diffusion plate, the light transmittance of a center corresponding part located in a vertical immediate downward direction of an arrangement of said plurality of flash lamps is lower than the light transmittance of an end corresponding part located outside said center corresponding part.