Substrate heaters are central to the wafer processing and are a critical component of any semiconductor deposition system. The deposition of oxygen-containing and corrosive materials, along with exposure to high temperatures in many types of deposition systems such as MBE, MOCVD, PVD, CVD, requires a much more robust heater. The range of the substrate temperatures and size determines the type of substrate heater to be used. Typically, such heaters are expensive and prone to failure in the corrosive environments encountered in the deposition chamber’s vacuum processing. Current state of the art for internally heated substrate heaters enables temperature ranges from room temperature to 1500°C. Some material systems require even higher substrate temperatures. This is done with lamps, coiled resistive wires, commercial heaters (such as silicon carbide, pyrolytic boron nitride, or pyrolytic graphite), and patterned metal heaters of various designs. All of these heaters are exposed to the deposition process and experience a short lifetime due to corrosives such as oxygen.
The present invention consists of a high temperature welded enclosure to protect and contain a resistive wire heater capable of 1200°C for wafer processing. The use of a high nickel-based alloy (such as Haynes 214) is used in the construction of a TIG-welded assembly. The welded assembly internally contains a Nichrome coil heater electrically insulated with ceramics. The substrate heater is mounted on an internal flange for positioning and for the input of power and a thermocouple. Most importantly, the enclosed resistive heater is helium-charged to one atmosphere for thermal conductivity to an external surface that is in contact with the wafer and process environment. This allows for helium purging or cooling to quickly reduce the substrate temperature for a given process.
- Lower cost, higher reliability, capable of high temperature substrate heating in high concentrations of oxygen and/or corrosives.
- Rapid substrate cooling in vacuum.
- For large substrates of 6″ and larger, multiple resistance wire heaters are used to provide the proper temperature gradient from center to edge of the substrate or multiple smaller substrates.
- Thermal control can utilize power as well as helium to control the separate heated zones, isolated internally within the enclosure.