Methods and apparatus for measuring temperatures at high potential

Abstract

A thermocouple is provided which measures the temperatures of structures at high RF potential, such as an RF electrode within a plasma CVD or plasma etch reactor. The thermocouple includes an outer conductive sheath that connects to the RF electrode at a first location, and a wire pair, connected to a second location of the RF electrode, that is used to sense the RF electrode temperature. The sheath--or a conductive member connected in circuit with the sheath--is wound into a coil to form an inductor with an impedance much greater than the impedance of the RF electrode. A large capacitor grounds the coil so that the thermocouple wires, extending through the sheath, and through and out of the coil, are available for diagnostic purposes. While RF current flows through the sheath, the wires experience the same magnetic field generated by the inductive coil, substantially grounding the thermocouple. Preferably, signal conditioning electronics remove any remaining DC bias voltages. In the case of a reactor for plasma CVD or etch, the thermocouple can be enclosed within a vacuum-sealed RF feedthrough that conducts the RF energy to the electrode.

Dependencies are inferred from the claim text.