Pressure flow and concentration control of oxygen/ozone gas mixtures

• US 5,904,170 A
• Filed: 05/14/1997
• Issued: 05/18/1999
• Est. Priority Date: 05/14/1997
• Status: Expired due to Term

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Harvey, Keith, Silvestre, Irwin, Truong, Quoc
• Primary Examiner(s): Ferensic, Denise L.
• Assistant Examiner(s): FARID, RAMYAR M
• Application Number:
  US08/856,499
• Time in Patent Office: 734 Days
• Field of Search: 73/23.2, 422/186.14, 422/186.07, 422/186.08, 422/186.12, 137/487.5, 137/9
• US Class Current: 137/9
• CPC Class Codes: G05D 11/08 by sensing concentration of mixture, e.g. measuring pH value
• CPC Class Codes: G05D 27/02 characterised by the use of electric means
• CPC Class Codes: Y10T 137/0363 For producing proportionate flow
• CPC Class Codes: Y10T 137/7761 Electrically actuated valve

Abstract

A system for controlling pressure flow and concentration Of O₃ /O₂ positions a thermal MFC upstream from an ozone generator to avoid the adverse effects of ozone on the thermal MFC. A flow restrictor diverts a precise amount of flow to an ozone monitor so that the flow to a CVD chamber is precisely controlled. In other embodiments a full-flow ozone monitor and non-thermal MFC are utilized.

Claims

1. A method for protecting a thermal mass flow controller in an ozone delivery system for supplying a precise mass flow of ozone to a gas input port of a chambers said method comprising:

providing a flow path extending from a source of Oxygen to the chamber;

providing a thermal-type mass flow controller (MFC) in said flow path, said mass flow controller having an MFC input port for receiving a flow of oxygen from the source of oxygen and an MFC output port for providing a controlled output mass flow of oxygen having a mass-flow magnitude, with the mass flow controller for adjusting the mass-flow magnitude of the controlled mass flow at the MFC output port to a desired value;

providing an ozone generator in said flow path, said ozone generator having a gas input port coupled to the MFC output port for receiving a mass flow of oxygen having a mass-flow magnitude equal to the desired value and a gas output port for providing a mass flow of a mixture of ozone and oxygen having a mass-flow magnitude at the desired value, with the ozone generator for converting a portion of the mass flow of oxygen received at the gas input port into ozone;

providing a back-pressure regulator in said flow path, said back-pressure regulator coupling the gas output port of said ozone generator to the gas input port of the chamber, with said back-pressure regulator for maintaining a desired pressure at the gas output port of said ozone generator;

providing an always open bypass flow line connected to said flow path between said back-pressure regulator and said gas output port of said ozone generator;

providing a low flow ozone monitor in said bypass flow line, said low flow ozone monitor having a gas monitor input port for receiving a low mass flow of the oxygen/ozone mixture, for indicating the ozone percentage of said mixture, with the low mass flow received by said low flow ozone monitor being dumped from the ozone delivery system; and

providing a calibrated, fixed flow restrictor in said bypass flow line said fixed flow restrictor coupled between said flow path and said gas monitor input port of said low flow ozone monitor, for diverting a precise monitoring mass flow of the mixture output by said ozone generator to said low flow ozone monitor, with the monitoring mass flow having a mass-flow magnitude determined by the pressure maintained by the back-pressure regulator, and where the mass flow of the mixture provided to the gas input port of said chamber is equal to the difference of the desired value of the mass-flow magnitude of the controlled mass flow output by the thermal MFC and the mass-flow magnitude of the monitoring mass flow diverted to the low flow ozone monitor.