Patent ID: 7594517

Claim:
A gas supply facility for a chamber, wherein the gas supply facility comprises: (a) a chamber exhausted by a vacuum pump; (b) a first pressure type flow controller controlling a small flow rate corresponding to 10% of a maximum flow rate of the gas supply facility to the chamber; (b) a second pressure type flow controller controlling a large flow rate corresponding to 90% of the maximum flow rate of the gas supply facility to the chamber, wherein the second pressure type flow controller is connected in parallel with the first pressure type flow controller; (c) a third controller operably connected to control operation of the first pressure type flow controller and the second pressure type flow controller; wherein the first pressure type flow controller and the second pressure type flow controller each comprises i. an orifice; ii. a pressure detector provided on an upstream side of the orifice; iii. a control valve provided on an upstream side of the pressure detector; and iv. a computation control part that computes gas flow rate Qc of gas passing through the orifice using pressure P 1 detected by the pressure detector and using formula Qc=KP 1 , where K is constant, so that a difference Qy with a set flow rate Qs is outputted as a driving signal to the control valve so that a ratio P 1 /P 2 of pressure P 1 on the upstream side of the orifice and pressure P 2 on the downstream side of the orifice is maintained at approximately two or more, wherein accurate flow control over a wide flow rate range is achieved because the first pressure type flow controller controls the small flow rate gas flow rate range up to 10% of the maximum flow rate supplied to the chamber, while the second pressure type flow controller controls the large flow rate gas flow rate range of about 10-100% of the maximum flow rate supplied to the chamber; and wherein the third controller comprises i. an input setting part that sets the maximum flow rate of gas supplied to the chamber; and ii. a signal conversion part; wherein the first pressure type flow controller is initially operated to control small flow rate and when flow rate reaches 10% of the maximum flow rate the second pressure type flow controller is switched into operation, wherein first control signals for both the first pressure type flow controller and the second pressure type flow controller are provided by the signal conversion part thereby enabling accurate flow rate control over a wide flow rate range by remitting first control signals from the signal conversion part to the first pressure type flow controller and the second pressure type flow controller.