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:
Mar. 09, 1999
Filed:
Apr. 29, 1997
John H Keller, Newburgh, NY (US);
Princeton University, Princeton, NJ (US);
Abstract
Uniformity of plasma density and potential are increased by reducing plasma confinement through use of a non-uniform, graded magnetic field by asymmetric energization of electromagnets with a waveform including harmonics of a fundamental frequency. The magnetic field strength or intensity decreases in the direction of ExB drift of energetic electrons within the plasma which tends to cause additional ionization in the plasma and a gradient of plasma density and potential. Thus, increase in ionization due to ExB drift is balanced by reduction of plasma confinement. Uniformity of average exposure to the plasma is further increased by rotation of the magnetic field. Uniformity of plasma potential or wafer bias is further improved by modulation of the radio frequency (RF) power used to form the plasma in synchronism with decreases in the magnetic field during switching for magnetic field rotation.