Temperature control for GaN based materials
A method of in-situ temperature measurement for a wafer treatment reactor such as a chemical vapor deposition reactor desirably includes the steps of heating the reactor until the reactor reaches a wafer treatment temperature and rotating a wafer support element within the reactor about a rotational axis. The method desirably further includes, while the wafer support element is rotating about the rotational axis, obtaining first operating temperature measurements using a first operating pyrometer that receives radiation from a first portion of the wafer support element, and obtaining first wafer temperature measurements using a wafer temperature measurement device that receives radiation from at least one wafer, the wafer temperature measurement device located at a first position.
1. An in-situ temperature measurement system for a wafer treatment reactor, the system comprising:
(a) a wafer support element having a rotational axis;
(b) a heating element for the wafer support element;
(c) a first operating pyrometer adapted to receive radiation from a first portion of the wafer support element at a first radial distance from the rotational axis; and
(d) a wafer temperature measurement device located at a first position, the wafer temperature measurement device in the first position being adapted to receive radiation from at least one wafer disposed on the wafer support element at the first radial distance from the rotational axis,
wherein the first operating pyrometer is sensitive to radiation in a first wavelength band, the wafer temperature measurement device is sensitive to radiation in a second wavelength band, and the at least one wafer is translucent or transparent to radiation in the first band and opaque to radiation in the second band.
2. The system as claimed in claim 1 , wherein the wafer temperature measurement device is a short wavelength pyrometer that is sensitive to light having wavelengths shorter than or equal to 400 nm.
3. The system as claimed in claim 1 , wherein the first wavelength band is in the infrared light spectrum, and the second wavelength band is in the ultraviolet light spectrum.
4. The system as claimed in claim 1 , wherein the first operating pyrometer and the wafer temperature measurement device are adapted to simultaneously take temperature measurements at the first radial distance from the rotational axis of the wafer support element.
5. The system as claimed in claim 1 , wherein the heating element is a multi-zone heating system for the wafer support element, a first zone of the heating system having a portion thereof located at the first radial distance from the rotational axis.
6. The system as claimed in claim 1 , further comprising a second operating pyrometer adapted to receive radiation from a second portion of the wafer support element at a second radial distance from the rotational axis,
wherein the temperature measurement device is adapted to be located at a second position, the wafer temperature measurement device in the second position being adapted to receive radiation from the at least one wafer at the second radial distance from the rotational axis.
7. The system as claimed in claim 6 , wherein the wafer temperature measurement device is engaged in a radially-extensive optical viewport, and wherein the wafer temperature measurement device is adapted to slide within the radially-extensive optical viewport between the first and second positions.
8. The system as claimed in claim 7 , further comprising a linear slide, wherein the wafer temperature measurement device is adapted to slide along the linear slide between the first and second positions.