Light irradiation type thermal process apparatus using a gas ring

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

• a chamber having a cylindrical side wall;
• a holding unit for holding said substrate in said chamber;
• a light irradiation unit irradiating said substrate with light;
• an annular gas ring attached to said side wall and directing processing gas supplied from outside said chamber into said chamber;
• and
• a cooling mechanism cooling said side wall, wherein
• said gas ring includes an annular upper ring and an annular lower ring,
• a gap between said upper ring and said lower ring provides a flow path for said processing gas,
• said lower ring has a cylindrical inner wall surface having a smaller diameter than said side wall,
• said inner wall surface of said lower ring is exposed to the thermal processing space in said chamber so that radiant heat from said substrate is transmitted, and
• heat capacity of said lower ring and thermal conductivity from said lower ring to said side wall have values not causing discoloration of said inner wall surface of said lower ring through light irradiation by said light irradiation unit.