Patent ID: 7650776

Claim:
A substrate processing apparatus for processing a substrate with a process gas, comprising: a processing chamber for holding a substrate therein; a process gas supply part for supplying a process gas together with a carrier gas into said processing chamber; an extraction part for extracting part of gas inside said processing chamber as a sample gas; a diluent gas supply part for supplying a diluent gas to dilute a sample gas; a dilution part for diluting a sample gas by mixing the sample gas extracted by said extraction part with a diluent gas supplied by said diluent gas supply part; a concentration meter for measuring the concentration of a process gas contained in the sample gas diluted by said dilution part; a first flowmeter for measuring the amount of flow of the sample gas before being diluted, which flows in a pipe from said extraction part to said dilution part or the amount of flow of the sample gas after being diluted, which flows in a pipe from said dilution part; a second flowmeter for measuring the amount of flow of the diluent gas flowing in a pipe from said diluent gas supply part to said dilution part; and a calculation part for calculating the concentration of the process gas contained in the sample gas before being diluted, on the basis of respective measured values of said concentration meter, said first flowmeter and said second flowmeter.