Remote Non-Contact High-Temperature Measurement for MOCVD Processing

摘要

Temperature sensitive reactions, used in metalorganic chemical vapor deposition(MOCVD) for producing semiconductor and optoelectronic devices, cannot be accurately controlled with existing temperature sensing techniques. Remote thermal monitoring and thermometry is needed to support development of expert MOCVD systems and new processes, such as rapid temperature ramping. Phase I research evaluated noninvasive surface sensing methods in the 600 to 1200 C range. Two wireless configurations, based on remote detection of gamma rays from trace radionuclides, were found to be feasible. Thermal monitoring can be based on vaporization of a nuclide source following chemical decomposition. The compound must reliably decompose at a temperature above the nuclide's melting point. An alternative approach can be based on a positron source placed behind the wafer. Many positrons annihilate in the wafer and some escape to annihilate in another surface near the wafer. The proportion between the two was demonstrated to be temperature dependent, presumably due to changes in attenuation (density of material) and electrical properties (conductivity, work function). Thus, this method promises a reliable thermometer scale.