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:
Feb. 03, 2004
Filed:
Jun. 27, 2002
Howard E. Rhodes, Boise, ID (US);
Mark Durcan, Boise, ID (US);
Micron Technology, Inc., Boise, ID (US);
Abstract
A retrograde and periphery well structure for a CMOS imager is disclosed which improves the quantum efficiency and signal-to-noise ratio of the photosensing portion imager. The retrograde well comprises a doped region with a vertically graded dopant concentration that is lowest at the substrate surface, and highest at the bottom of the well. A single retrograde well may have a single pixel sensor cell, multiple pixel sensor cells, or even an entire array of pixel sensor cells formed therein. The highly concentrated region at the bottom of the retrograde well repels signal carriers from the photosensor so that they are not lost to the substrate, and prevents noise carriers from the substrate from diffusing up into the photosensor. The periphery well contains peripheral logic circuitry for the imager. By providing retrograde and peripheral wells, circuitry in each can be optimized. Also disclosed are methods for forming the retrograde and peripheral well.