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:
Jun. 26, 2001
Filed:
Dec. 08, 1998
Leping Li, Poughkeepsie, NY (US);
James Albert Gilhooly, Saint Albans, VT (US);
Clifford Owen Morgan, Burlington, VT (US);
Cong Wei, Poughkeepsie, NY (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
A method and apparatus are described for detecting an endpoint of a film removal process in which a target film overlying a stopping film is removed. A chemical reaction product is generated from at least one of the target film and the stopping film; this chemical reaction product is converted to a separate product. The separate product is exposed to ionizing radiation. The ionization current generated by the radiation is monitored as the target film is removed. A change in the ionization current corresponds to a change in concentration of the separate product, thereby indicating the endpoint of the film removal process. In the particular case of removal of a silicon dioxide film overlying a silicon nitride film by chemical-mechanical polishing, the reaction product is ammonia extracted from the polishing slurry. The ammonia is converted to ammonium chloride by a reaction with hydrogen chloride vapor. As the ammonium chloride, entrained in a carrier gas, is pumped through a detection unit, a change in the concentration thereof is detected by monitoring a change in the ionization current generated by a source of alpha particles.