Method of welding thermocouples to silicon wafers for temperature monitoring in rapid thermal processing

Abstract

Disclosed is a method of welding a temperature-sensing thermocouple to a silicon wafer for sensing the temperature of the wafer during rapid thermal processing using TIG welding and/or electron-beam welding. In one embodiment, a ball of silicon is formed on the bead at one end of a thermocouple by placing the thermocouple on a silicon chip and then melting the silicon chip with a TIG welder. The ball and thermocouple are then placed on the surface of a silicon wafer and the ball and surface are then melted whereby the ball of silicon flows into the silicon wafer. In placing the thermocouple on an edge portion of a silicon wafer, the wafer is supported on a tantalum plate with the edge portion of the wafer extending beyond the plate. A molybdenum sheet is positioned on the top surface of the wafer with the edge portion of the wafer exposed. A TIG arc is established with the molybdenum layer and then the arc is moved to the edge portion of the wafer for melting the silicon. In attaching the thermocouple on the silicon wafer other than on an edge portion, electron-beam welding is employed. An electron beam at low power is focused on the ball of silicon, and then the power of the electron beam is increased while the beam is pulsed so that the ball and adjacent silicon wafer are melted.

Dependencies are inferred from the claim text.