An apparatus for the non-contact, in-situ temperature measurement of a substrate during chemical vapor deposition (CVD) of a material film on the substrate in a CVD reactor vessel that contains a plasma media, the apparatus comprising:
- a light comparison device;
- a light source that provides magnitude modulated UV light having a plurality of separated spectral components with wavelengths corresponding to different temperature dependencies of absorptance in the material film, the separated spectral components being within transparency spectral windows off the plasma media contained in the reactor vessel;
- an optical system that directs a first portion of the magnitude modulated light at the material film, directs a second portion of the magnitude modulated light at the light comparison device, and directs light reflected from the material film at the light comparison device, and
- wherein the light comparison device compares the second portion of the magnitude modulated light and the light reflected from the material film to determine a temperature at the material film;
- and
- a temperature control system that utilizes the determined temperature to control the temperature of the substrate.