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:
Nov. 16, 1999
Filed:
Oct. 31, 1997
Chung-Yuan Lee, Tao Yuan, TW;
Chun-Yen Chang, Hsinchu, TW;
Sun-Chieh Chien, Hsinchu, TW;
Chen-Chiu Hsu, Hsinchu, TW;
United Microelectronics Corp., Hsinchu, TW;
Abstract
A triple-well structure for semiconductor IC devices such as an SRAM IC device and a process for its fabrication, that allows for improved data storage stability as well as improved immunity capability against interference from device I/O bouncing and alpha particles. The triple-well structure includes at least one P-well in a P-type substrate, a number of N-wells, and a retrograde P-well formed within one of the N-wells. The process for fabricating the triple-well structure includes first implanting boron ions in the P-type substrate. A photomask is subsequently formed for the implantation of phosphorous ions in the region where a P-type MOS transistor is to be fabricated. A high temperature drive-in procedure is then employed to form a P-well and a number of N-wells. A selected area of one of the N-wells where an N-type MOS transistor is defined is then subjected to boron ion implantation, which is followed by an annealing procedure to form the retrograde P-well.