| 摘要 |
PURPOSE:To hold impurity density in a furace to a constant, and to enhance reproducibility and stability of layer resistance of an impurity diffusion region by a method wherein the absolute pressure of a chamber is measured, and feed back control is applied to the gas flow rate. CONSTITUTION:A signal outputted from a barometer 8 provided in the neighborhood of the throat of a diffusion furnace is fed to a gas dilution device 7 through a pressure controller 9, and the flow rate set value of a mass flow controller in the device 7 is changed. In the pressure controller 9, to fix impurity density inside of a furnace core tube in relation to internal pressure of the furnace core tube holding the total flow rate inside of the furnace core tube to a constant, the device is so contructed as to enable to output a flow rate command to both of a mass flow for impurity gas control and a mass flow for carrier gas control taking in signals of two kinds in regard to the flow rates of carrier gas and impurity gas. When the change of pressure is detected by the barometer 8, both of the impurity gas flow rate and the carrier gas flow rate are controlled to fix impurity density. |
