| US 7,557,397 B2 | ||
| Pixel with asymmetric transfer gate channel doping | ||
| Chintamani P. Palsule, Fort Collins, Colo. (US); Changhoon Choi, Palo Alto, Calif. (US); Fredrick P. LaMaster, Fort Collins, Colo. (US); John H. Stanback, Fort Collins, Colo. (US); Thomas E. Dungan, Fort Collins, Colo. (US); Thomas Joy, San Jose, Calif. (US); and Homayoon Haddad, Beaverton, Oreg. (US) | ||
| Assigned to Aptina Imaging Corporation, Grand Cayman (Cayman Islands) | ||
| Filed on Feb. 16, 2007, as Appl. No. 11/707,848. | ||
| Application 11/707848 is a continuation in part of application No. 11/144304, filed on Jun. 03, 2005, granted, now 7,115,924. | ||
| Application 11/144304 is a continuation of application No. 11/323693, filed on Dec. 30, 2005. | ||
| Prior Publication US 2007/0262355 A1, Nov. 15, 2007 | ||
| Int. Cl. H01L 31/06 (2006.01); H01L 21/00 (2006.01) | ||
| U.S. Cl. 257—292 [257/233; 257/291; 257/404; 257/431; 257/655; 438/286] | 14 Claims |

| 1. A pixel, comprising:
a substrate of a first conductivity type and having a surface;
a photodetector of a second conductivity type that is opposite the first conductivity type;
a floating diffusion region of the second conductivity type;
a transfer region between the photodetector and the floating diffusion;
a gate positioned above the transfer region and partially overlapping the photodetector;
a pinning layer of the first conductivity type extending at least across the photodetector from the gate;
a channel implant of the first conductivity type; and
a counter doping implant of the second conductivity type positioned below the channel implant, the channel implant and the
counter doping implant each extending from between a midpoint of the transfer gate and the floating diffusion to at least
across the photodetector, wherein the channel implant has a dopant concentration such that a dopant concentration of the transfer
region is greater proximate to the photodetector than the floating diffusion, and wherein the counter doping implant has a
dopant concentration which at least compensates for a doping of the substrate in an area of the transfer region below the
channel implant such that a fully-buried channel is formed in the transfer region between the photodetector and floating diffusion
when the transfer gate is energized.
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