Semiconductor wafer temperature measurement system and method

DETAILED DESCRIPTION Other objects and advantages will be obvious, and will in part appear hereinafter and will be accomplished by the present invention which provides a method and apparatus for measuring the temperature of a semiconductor wafer.
One embodiment of the present invention discloses a temperature measurement system which comprises a light source, possibly a laser, a photodetector, a fixed mirror, and a beam splitter.
The components are configured such that light from the light source travels through the beam splitter and subsequently reflects off the mirror and the wafer and is received by the photodetector.
Changes in the intensity of the light received by the photodetector correspond to changes in the temperature of the wafer by exploiting the properties of thermal expansion of the semiconductor material.
By measuring the absolute temperature at one point in time, the absolute temperature of the wafer may be determined based on the changes in wafer temperature.
Alternate embodiments and methods of use are also disclosed.
An advantage of the invention is that the technique is non-contacting with respect to the wafer and therefore device contamination problems are avoided.
The present invention is also useful at all temperatures.
Another advantage is that the technique of the present invention depends on a bulk property, namely thermal expansion, of the material and therefore variations such as doping or emissivity do not perturb the results.