Precise thermal processing apparatus

Abstract

Disclosed is apparatus for subjecting a workpiece to a controlled temperature comprising a light-weight muffle of high diffusivity material having an interior high emissivity surface, an air cooled envelope surrounding the muffle having an infrared reflective interior surface, and a housing which maintains a vacuum in the space outside of the muffle. Heaters and temperature sensors are spaced about the muffle. The heaters are controlled by an electronic feedback control system which actuates the heaters in response to signals received from the temperature sensors. The apparatus is ideally suited for use in the controlled diffusion processing techniques employed in the fabrication of electronic devices because it applies on the order of 90% of the generated heat to the workpiece, can be rapidly heated up and cooled, and can maintain a selected temperature within narrow limits.

Dependencies are inferred from the claim text.