In-situ spatially resolved plasma monitoring by using optical emission spectroscopy

A plasma chamber, comprising:

• a chamber body defining a substrate processing region therein, the chamber body having a sidewall;
• a viewing window disposed in the sidewall;
• a plasma monitoring device coupled to the viewing window, the plasma monitoring device comprising:
• an objective lens;
• an aperture member having a pinhole, wherein the aperture member is movable relative to the objective lens by a first actuator;
• and
• a first diaphragm disposed in a light path between the chamber body and the objective lens, the first diaphragm having a first adjustable aperture;
• and
• a pivoting actuator pivotally moving the plasma monitoring device about a central axis direction vertically passing through the chamber body.

A method for monitoring a plasma in a process chamber, comprising:

• coupling a plasma monitoring device to a viewing window disposed in a sidewall of the process chamber, wherein the plasma monitoring device comprising:
• an objective lens;
• and
• an aperture member having a pinhole;
• moving pivotally the plasma monitoring device about a central axis direction vertically passing through the process chamber and moving the aperture member with respect to the objective lens to change a focal point in the plasma and allow light emitted from the focal point to travel through the objective lens and impinge onto the pinhole;
• and
• analyzing characteristics of the light passing through the pinhole by an optical emission spectrometer.