A hybrid-type surface-temperature sensor that combines the advantages of contact and non-contact sensing methods has been developed and that offers a way to overcome the weak points of both methods. The hybrid-type surface-temperature sensor is composed of two main components: a metal film that makes contact with the object and an optical sensor that is used to detect the radiance of the rear surface of the metal film. Temperature measurement using this thermometer is possible with an uncertainty of 0.5 K after compensating for systematic errors in the temperature range from 900 to 1,000 K. The response time of our previous hybrid-type sensor is, however, as long as several tens of seconds because the measurement must be carried out under thermally steady-state conditions. In order to overcome this problem, a newly devised rapid-response hybrid-type surface-temperature sensor was developed and that can measure the temperature of an object within 1 s by utilizing its transient heat transfer response. Currently, the temperature of a silicon wafer can be measured with an uncertainty of 1.0 K in the temperature range from 900 to 1,000 K. This sensor is expected to provide a useful means to calibrate in situ temperature measurements in various processes, especially in the semiconductor industry. This article introduces the basic concept and presents experimental results and discussions.
Transmissivity of a silicon wafer strongly depends on temperature. Using this characteristic of the silicon wafer, we studied two non-contact methods of temperature measurement for silicon wafers in the temperature range from 300 K to 1000 K. The one is the use of temperature dependence of transmissivity, and the other is the use of optical absorption edge wavelength. Both methods are pursued from the view points of wavelength (900 1750 nm), polarization (p-and s-polarized) and direction (normal to 800) for specimens with different resistivity (0.01 Qcm -2700 Qcm). We obtained some promising knowledge for application to temperature measurement of silicon wafers. For example, for the former method, the use of longer wavelengths over 1500 nm is suitable in the high temperature range over 600 K, and the use of shorter wavelengths less than 1200 nm is appropriate in the low temperature range below 600 K. On the other hand, for the latter method using optical absorption edge wavelength is effective in the temperature range from room temperature to high temperature of 1000 K. In this paper, experimental results and discussions are quantitatively described and considered in detail.
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