Substrate processing apparatus and substrate processing method

A substrate processing apparatus, comprising:

• a liquid processing unit configured to supply, onto a front surface of a substrate, individual multiple processing liquids including a first processing liquid and a second processing liquid different from the first processing liquid;
• and
• an exhaust unit configured to exhaust an exhaust gas exhausted from the liquid processing unit to an outside, the exhaust gas including a first exhaust gas exhausted from the liquid processing unit when the substrate is processed with the first processing liquid and a second exhaust gas exhausted from the liquid processing unit when the substrate is processed with the second processing liquid,
• wherein the exhaust unit includes:
• a main exhaust pipe configured to allow the exhaust gas to flow therein, the main exhaust pipe including a first portion located on an upstream side and a second portion located on a downstream side of the first portion;
• a first individual exhaust pipe configured to allow the first exhaust gas to flow therein;
• a second individual exhaust pipe configured to allow the second exhaust gas to flow therein;
• and
• a switching unit configured to selectively communicate the main exhaust pipe with one of the first individual exhaust pipe and the second individual exhaust pipe, and
• wherein the switching unit includes:
• a first switching mechanism provided between the first portion and the first individual exhaust pipe and configured to switch between a communication state where the first portion communicates with the first individual exhaust pipe when the first exhaust gas is exhausted from the liquid processing unit and a non-communication state where the first portion does not communicate with the first individual exhaust pipe when the exhaust gas other than the first exhaust gas is exhausted from the liquid processing unit;
• a second switching mechanism provided between the second portion and the second individual exhaust pipe and configured to switch between a communication state where the second portion communicates with the second individual exhaust pipe when the second exhaust gas is exhausted from the liquid processing unit and a non-communication state where the second portion does not communicate with the second individual exhaust pipe when the exhaust gas other than the second exhaust gas is exhausted from the liquid processing unit;
• a third switching mechanism provided between the first portion and the second portion of the main exhaust pipe and configured to switch between a closed state where a flow of the first exhaust gas to the second portion is blocked when the first exhaust gas is exhausted from the liquid processing unit and an open state where a flow of the exhaust gas other than the first exhaust gas to the second portion is allowed when the exhaust gas other than the first exhaust gas is exhausted from the liquid processing unit;
• an outside air introduction pipe connected to the second portion to allow outside air to be introduced into the second portion;
• and
• a fourth switching mechanism provided in the outside air introduction pipe and configured to switch between an open state where a flow of the outside air to the second portion is allowed when the first exhaust gas is exhausted from the liquid processing unit and a closed state where the flow of the outside air to the second portion is blocked when the exhaust gas other than the first exhaust gas is exhausted from the liquid processing unit.