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In-Situ, Contactless and Non-Destructive Measurement of the Temperature Variation Over the Surface of a Silicon Wafer

IP.com Disclosure Number: IPCOM000059981D
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Guidotti, D: AUTHOR [+3]

Abstract

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.

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In-Situ, Contactless and Non-Destructive Measurement of the Temperature Variation Over the Surface of a Silicon Wafer

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 (1OEK) 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. The reference beam A is reflected by the beam splitter 3, while the probe beam B is reflected by a mirror 4. The reference beam A passes through variable attentuator 5 and chopper 6 incident upon reference wafer 8 at some known temperature (T). Probe beam B passes through chopper 6 into an oven to be reflected from a sample wafer 7. Upon reflection from the sample and reference wafers, the beam impinges a 50% beam splitter 13. Beams A and B are combined onto and detected by a DC coupled photodiode 9 to a lock-in amplifier 11 at frequency n. One-half of each beam is also directed to a second p...