The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 07, 2001
Filed:
Feb. 01, 1999
Charles F. Drexel, Rancho Palos Verdes, CA (US);
Hamid Saghatchi, Orange, CA (US);
DXL USA Inc., Torrance, CA (US);
Abstract
An assembly for measuring the mass flow and flow rate of gases such as are used in semiconductor fabrication processes. The assembly includes an axial flow passage, viz., a capillary tube with a bore of about 0.050 inch diameter and a wall thickness of about 0.002 inch, having a downstream end connected to a diffuser section having an axially symmetric, diverging passage. Gas exiting the diffuser section has a low pressure drop because the gas has expanded at a low, controlled rate, converting velocity head into pressure head, and because the tube and diffuser section passage are in-line, eliminating right-angle turns. The assembly also includes two resistance thermometers, coils of iron-nickel alloy wire about 0.0004 inch in diameter, providing a differential temperature measurement with a time constant of less than 4 seconds. When incorporated into a mass flow controller admitting arsine gas from a storage container into a vacuum chamber, the assembly can maintain a flow rate of 5 sccm when the residual gas pressure in the container is as low as 5 Torr. The assembly can also be incorporated into a mass flowmeter.