Patent ID: 8642136

Claim:
A method of processing a substrate disposed on a lower electrode adapted to generate plasma of a gas by applying AC power between the lower electrode and an upper electrode in a processing chamber that is capable of being depressurized, the method comprising: depositing a thin film on the substrate while depressurizing an inside of the processing chamber and introducing the gas into the chamber; transmitting irradiating light, while depositing the thin film, toward the inside of the processing chamber through a monitoring window installed at the processing chamber; monitoring a reflection light intensity of reflection light received through the monitoring window; measuring a temporal gradient in the reflection light intensity during the deposition; calculating a termination time of the deposition of the thin film based on a measurement value of the temporal gradient; and terminating the deposition of the thin film by setting the termination time as an end point of the deposition of the thin film, wherein the deposition comprises accumulating a deposit on a resist pattern which masks an etching target film formed on the substrate, and wherein the calculating the termination time is based on a correlation between the temporal gradient in the reflection light intensity and a variation in a critical dimension of a structure formed by etching the etching target film.