# US 7,078,751 B2 · Solid-state imaging device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,078,751 B2 - Document ID: US7078751B2 - Status: Granted - Kind: B2 - Application number: 10/610,714 - Filed: 2003-06-30 - Published: 2004-01-08 - Granted: 2006-07-18 - Earliest claimed: 2002-07-02 - Assignees: Sharp Kabushiki Kaisha - Inventors: Takashi Watanabe - Web page: https://patentgrep.com/patent/US7078751B2 ## CPC - H10F 39/8057: {Optical shielding} - H10F 39/803: {Pixels having integrated switching, control, storage or amplification elements} - H10F 39/807: {Pixel isolation structures} - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION ## Abstract The sources or drains 14 of transistors and photodiodes 13, which constitute shaded pixels covered with a shading layer 16, are formed on a surface of a highly doped well 20 provided on a lowly doped substrate 11. Therefore, a potential barrier ΔV is formed extended from the lowly doped substrate 11 toward the highly doped well 20. Even if intense spot light is made incident on some of light-receiving pixels and part of light 17 reaches a neutral region of the lowly doped substrate 11, part of diffused charges 18 photoelectrically converted there cannot intrude into the highly doped well 20. Therefore, an output signal level of the shaded pixels does not change, and a black reference level can be maintained. ## Claims ### Claim 1 A solid-state imaging device in which a plurality of pixels each comprised of a photodiode and a transistor are arranged on a surface of a semiconductor substrate, said plurality of pixels including light-receiving pixels having light incident on the respective photodiodes thereof and shaded pixels having no light incident on the respective photodiodes thereof, and in which a black reference level is obtained on the basis of an output signal from said shaded pixels, wherein a lower side of each of the photodiodes of said shaded pixels facing the semiconductor substrate is covered with an impurity layer having a conductivity type identical to that of the semiconductor substrate and has a concentration higher than that of the semiconductor substrate, and a lower side of each of the photodiodes of said light-receiving pixels facing the semiconductor substrate is in direct contact with the semiconductor substrate. ### Claim 2 (depends on 1) The solid-state imaging device as claimed in claim 1, wherein a lower side of the transistor of each of the shaded pixels facing the semiconductor substrate is also covered with the impurity layer, and a lower side of the transistor of each of the light-receiving pixels facing the semiconductor substrate is covered with another impurity layer that is of a conductive type identical to that of the semiconductor substrate and has a concentration higher than that of the semiconductor substrate. ### Claim 3 (depends on 2) The solid-state imaging device as claimed in claim 2, wherein the impurity layer that covers the lower side of the shaded pixel has its whole area shaded by a shading layer and is separated from the impurity layer that covers the lower side of the transistor of the light-receiving pixels via a region of the semiconductor substrate. ### Claim 4 (depends on 3) The solid-state imaging device as claimed in claim 3, wherein the shading layer that shades the whole area of the impurity layer that covers the lower side of the shaded pixels is grounded. ### Claim 5 (depends on 1) The solid-state imaging device as claimed in claim 1, wherein the impurity layer that covers the lower side of the photodiodes of each of the shaded pixel is grounded. ### Claim 6 (depends on 1) The solid-state imaging device as claimed in claim 1, wherein the shaded pixels are arranged in a direction of column in the vicinity of either one or both of both ends in a direction of a row of the light-receiving pixels arranged in a matrix form. ### Claim 7 (depends on 1) The solid-state imaging device as claimed in claim 1, wherein the shaded pixels are arranged in a direction of a row in the vicinity of either one or both of both ends in a direction of column of the light-receiving pixels arranged in a matrix form. ### Claim 8 A solid-state imaging device in which a plurality of pixels each comprised of a photodiode and a transistor are arranged on a surface of a superficial portion of a semiconductor substrate, said plurality of pixels including light-receiving pixels where light is incident on the photodiode and shaded pixels where no light is incident on the photodiode, and a black reference level is obtained on the basis of an output signal from the shaded pixels, wherein at least a part of said superficial portion of the semiconductor substrate faces the photodiodes of the shaded pixels and serves as an impurity layer of a conductivity type identical to the conductivity type of the remainder of said superficial portion having a concentration higher than that of the remainder of said superficial portion, and a side of each of the photodiodes of each of the light-receiving pixels faces said remainder of said superficial portion of said substrate and is in direct contact with said remainder of said superficial portion of said substrate. ### Claim 9 (depends on 8) The solid-state imaging device as claimed in claim 8, wherein the superficial portion is constructed separately from a main body portion of the substrate on a surface side of the semiconductor substrate. ### Claim 10 (depends on 9) The solid-state imaging device as claimed in claim 9, wherein the surface portion is a well or an epitaxially grown layer formed on the surface side of the semiconductor substrate.