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:
Dec. 29, 1992
Filed:
Jun. 28, 1991
Ching-Tai S Wang, Worcester, MA (US);
Gregory J Grula, Charlton, MA (US);
Digital Equipment Corporation, Maynard, MA (US);
Abstract
A method of planarizing the surface of a silicon wafer of the type employing trench isolation is disclosed where the trenches and active areas of wafer surface may be of varying widths. The trenches and active areas are covered with a conformal coating of silicon oxide, and, according to one embodiment, this coating is subjected to an etch to leave sidewall spacers of oxide at the sidewalls of the trenches, then a second conformal coating of oxide is applied. A first layer of photoresist is applied to the face and patterned to leave photoresist only in the wider trenches. According to another embodiment the remaining photoresist of the first layer is reflowed by a heat treatment to account for any misalignment or the like. A second layer of photoresist is applied, then etched back to the conformal coating on the active areas, leaving some resist in narrow trenches. A third layer of photoresist is applied and then the three layers of photoresist plus oxide are simultaneously etched back to the level of the tops of the active areas, leaving a substantially planar surface where there is a minimum of variation in height in the various areas of differing trench and active area widths.