Heat treatment method and heat treatment apparatus of light irradiation type

A heat treatment apparatus for irradiating a substrate with light to heat the substrate, the heat treatment apparatus comprising:

• an indexer unit exposed to the air atmosphere;
• a cooling chamber connected to said indexer unit via a first gate valve, for cooling a substrate;
• a transfer chamber connected to said cooling chamber via a second gate valve;
• a treatment chamber connected to said transfer chamber for applying heating treatment to a substrate;
• a gas supply unit that supplies nitrogen gas to said cooling chamber at a first supply flow rate or a second supply flow rate larger than said first supply flow rate;
• an exhaust unit that exhausts an atmosphere from said cooling chamber at a first exhaust flow rate or a second exhaust flow rate larger than said first exhaust flow rate;
• and
• a controller for controlling a supply flow rate by said gas supply unit and an exhaust flow rate by said exhaust unit,
• wherein an untreated substrate is transferred from said indexer unit to said treatment chamber via said cooling chamber and said transfer chamber in this order,
• a treated substrate subjected to heating treatment in said treatment chamber is transferred from said treatment chamber to said indexer unit via said transfer chamber and said cooling chamber in this order, and
• said controller is configured to control said gas supply unit and said exhaust unit so as to supply nitrogen gas to said cooling chamber at said second supply flow rate and to perform exhausting from said cooling chamber at said second exhaust flow rate, respectively, for at least a predetermined time after said untreated substrate is transferred to said cooling chamber.