In-Situ, Contactless and Non-Destructive Measurement of the Temperature Variation Over the Surface of a Silicon Wafer
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
Temporal and spatial variations in the surface temperature of a semiconductor wafer (silicon (Si), in particular) can be measured to better than one degree Kelvin (1ŒK) by taking advantage of the fact that the reflectivity (R) of Si varies with temperature (T). Temperature resolution depends on precisely measuring a change in reflectivity. Changes in reflectivity can be measured to one part in 105 when modulation techniques are used to measure the difference in reflectivity between a (Si) wafer of interest and a reference wafer at some known temperature, such as room temperature. In the figure, a beam from a He-Ne laser (5-10 mW) 1 is modulated by an acousto-optic modulator 2. The beam is then split by a beam splitter 3 into a probe beam A and a reference B.