What is the difference between one-color and two-color pyrometry?
One of the main features of the In-Situ 4000 Process Monitor is the ability to properly measure the temperature of wafers with growing dielectric films. Other pyrometers cannot do this. There are two basic types of pyrometers available: single color and two color. Single Color Pyrometry: Single color simply measures the intensity of emitted radiation in a given wavelength band. That intensity is mathematically converted to temperature based on Planck’s law. The law however requires 2 unknown parameters: the “geometry factor” and the surface emissivity at that wavelength. The “geometry factor” is a measure of how much light is collected by the optics, how big an area on the wafer is measured, and how sensitive the sensing electronics is in converting the radiation to a voltage. Typical pyrometer manufacturers will calibrate the “geometry factor” against a “black body” which is at a known temperature. Black bodies have an emissivity of 1.0. A cavity or oven will approach an ideal black b
