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1. (WO1998049729) IMPROVED SOLID STATE IMAGE SENSOR

Pub. No.:    WO/1998/049729    International Application No.:    PCT/GB1998/001214
Publication Date: Fri Nov 06 00:59:59 CET 1998 International Filing Date: Sat Apr 25 01:59:59 CEST 1998
IPC: H01L 21/76
H01L 27/146
H01L 27/148
Applicants: VLSI VISION LIMITED
HURWITZ, Jonathan, Ephriam, David
DENYER, Peter, Brian
Inventors: HURWITZ, Jonathan, Ephriam, David
DENYER, Peter, Brian
Title: IMPROVED SOLID STATE IMAGE SENSOR
Abstract:
A solid state image sensor comprises a number of photosensitive pixels. The photosensitive area of each pixel has one or more edge portions defined by isolation (31) separating the active area of the semiconductor substrate from other active areas thereof and the doping density of the impurity at the edge portion(s) of the photosensitive area is substantially restricted. A preferred embodiment is a CMOS photodiode sensor in which each pixel thereof includes a photodiode (20) formed by two N-type layers (33, 34) in a P-type substrate. The lower N-type layer (33) is more heavily doped than the upper layer (34) and the edges of the lower layer (33) are set back from the edges of the upper layer (34). A method of reducing dark-current leakage is also claimed involving the use of two or more different masks in the impurity doping process during manufacture of a solid state image sensor.