Abstract
In order to measure the temperature of the silicon wafers in a diffusion furnace (which is usually used for semiconducter heating process such as oxidization, annealing and diffusion), we design a radiation thermometry suitable for this purpose. The feature of this thermometry is measuring the temperature of the wafers to be usually out of sight by an optical guide, which consists of two quartz prisms. The radiation from the objective wafer is measured by a pyrometer with measuring wavelength of 0.9μm. The reason why the wavelength is selected is that a silicon wafer is opaque at this wavelength. The emissivity of a silicon wafer at 0.9μm is measured, and it is confirmed that the emissivity dose not depend on temperature within the range of 600∼1, 000°C. It is also confirmed that the emissivity of a silicon wafer with a thin film of silicon oxide or silicon nitride can be calculated by considering the interference effect of multiple reflection inside the thin film.
The accuracy of the thermometry is examind by comparing the measured value of the pyrometer with that of the thermo-couple. The two measured values agree within the difference of ±2°C in steady state. But when wafers are inserting into or drawing out from the furnace, an error is caused by veiling glare at the optical guide and the wafer. The error is 10∼20°C when the wafer temperature is 250°C lower than that of the inside wall of the furnace, and is about 5°C when the wafer temperature is 150°C lower.
