HIGH-TEMPERATURE PROCESS IMPROVEMENTS USING HELIUM UNDER REGULATED PRESSURE
A method for minimizing unwanted ancillary reactions in a vacuum furnace used to process a material, such as growing a crystal. The process is conducted in a furnace chamber environment in which helium is admitted to the furnace chamber at a flow rate to flush out impurities and at a predetermined pressure to achieve thermal stability in a heat zone, to minimize heat flow variations and to minimize temperature gradients in the heat zone. During cooldown helium pressure is used to reduce thermal gradients in order to increase cooldown rates.
1 - 23 . (canceled)
24 . A furnace for producing a crystalline material comprising:
a heat zone;
a vacuum pump assembly connected to the furnace that maintains a vacuum in the heat zone;
at least one heater surrounding the heat zone that provides heat to the heat zone;
a non-reactive gas system connected to the furnace that supplies at least one non-reactive gas into the heat zone; and
a non-reactive gas regulating system connected to the furnace and to the vacuum pump assembly that establishes and maintains a flow rate and a pressure of the non-reactive gas in the heat zone,
25 . The furnace of claim 24 , further comprising a heat exchanger.
26 . The furnace of claim 24 , wherein the non-reactive gas system supplies the non- reactive gas to the heat zone from beneath the furnace.
27 . The furnace of claim 24 , wherein the non-reactive gas system comprises a supply tank, a flow controller, and a flow monitor.
28 . The furnace of claim 24 , wherein the non-reactive gas regulating system comprises a pressure regulator and a pressure monitor.
29 . The furnace of claim 28 , wherein the pressure controller is a proportional valve.
30 - 34 . (canceled)