Gas control system for chemical vapor deposition system

In a gas system for use in a chemical vapor deposition process, the combination comprising a pair of controlled sources of gases to be mixed and introduced in the heated zone of a process tube within a diffusion furnace, one of said gas sources being controlled by a mass flow controller and the other source having a mass flow meter which provides an error signal when the flow through said meter departs from a preselected setpoint flow, said sources being connected to a mixing manifold downstream of said controller and said meter, a plurality of gas injectors for delivering said mixed gases to contiguous areas lengthwise in the heated zone of said process tube, said injectors being connected to said mixing manifold with mass flow controllers for controlling the flow of mixed gases to each of said injectors, one of said injector mass flow controllers being a master controller regulating said gas mixture flow to a preselected level, the others of said injector mass flow controllers being slaved to said master controller and having controls to provide in said slaved controllers flows of selected percentage of the flow through said master controller, said error signal being applied to regulate the total flow of mixed gas through said slaved controllers to cause said flow through said meter to conform to said setpoint value.

A gas flow control system for use in the processing of semiconductor materials in a low temperature, low pressure process in which a mixture of pyrophoric gases and oxygen are separately injected into the heated zone of a process tube of a diffusion furnace comprising a sealed process tube having means for evacuating gases contained therein and for heating wafers contained in a proces zone, first gas injection means including a plurality of gas injectors extending into said process tube, said injectors having exit orifices spaced lengthwise of said process zone, second gas injection means disposed in said process tube in spaced relation from said first gas injection means and coextensive therewith, individual mass flow controllers connected to control the gas flow to each of said injectors of said first gas injection means, a gas mixing manifold having means for supplying a gas mixture to said individual mass flow controllers, two separate sources of pyrophoric gas connected to deliver gas to said manifold, a mass flow controller to establish a selected rate of flow of one of said pyrophoric gases, the flow rate of the other of said pyrophoric gases being regulated by the mass flow controllers which regulate the individual injector flows.