# US 7,608,870 B2 · Isolation trench geometry for image sensors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,608,870 B2 - Document ID: US7608870B2 - Status: Granted - Kind: B2 - Application number: 11/478,563 - Filed: 2006-06-30 - Published: 2007-02-15 - Granted: 2009-10-27 - Earliest claimed: 2004-06-22 - Assignees: Aptina Imaging Corporation - Inventors: Bryan G. Cole; Howard E. Rhodes - Web page: https://patentgrep.com/patent/US7608870B2 ## CPC - H10F 39/18: Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors - H10F 39/014: {of CMOS image sensors} - H10F 39/807: {Pixel isolation structures} - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION ## Abstract A pixel cell including a substrate having a top surface. A photo-conversion device is at a surface of the substrate and a trench is in the substrate adjacent the photo-conversion device. The trench has sidewalls and a bottom. At least one sidewall is angled less than approximately 85 degrees from the plane of the top surface of the substrate. ## Claims ### Claim 1 A pixel comprising: a photoconversion device formed in a substrate; a well having a first conductivity type formed adjacent to said photoconversion device for isolating said pixel from an adjacent pixel; and an isolation region formed at least partially within said well, said isolation region comprising: a first sidewall having a first angle measured from a plane of a top surface of said substrate; and a second sidewall having a second angle less than approximately 85 degrees measured from said plane of said top surface of said substrate, said second sidewall being closer to said photoconversion device than said first sidewall, wherein said first angle is different from said second angle. ### Claim 2 (depends on 1) The pixel according to claim 1, wherein said first angle is within a range of approximately 85 degrees to approximately 90 degrees. ### Claim 3 (depends on 1) The pixel according to claim 1, wherein said second angle is within a range of approximately 15 degrees to approximately 70 degrees. ### Claim 4 (depends on 1) The pixel according to claim 1, wherein said second angle is within a range of approximately 60 degrees to approximately 70 degrees. ### Claim 5 (depends on 1) The pixel according to claim 1, wherein said photoconversion device is a pinned photodiode, said pinned photodiode having a first region of said first conductivity type formed over a second region of a second conductivity type. ### Claim 6 (depends on 1) The pixel according to claim 1, further comprising a material liner formed within said isolation region. ### Claim 7 (depends on 6) The pixel according to claim 6, wherein said material liner is a nitride liner. ### Claim 8 (depends on 6) The pixel according to claim 6, wherein said material liner is an oxide liner. ### Claim 9 A pixel comprising: a photoconversion device formed in a substrate; a well having a first conductivity type formed adjacent to said photoconversion device for isolating said pixel from an adjacent pixel; a first sidewall formed within said well having a first sidewall angle measured from a plane of a top surface of said substrate; a second sidewall formed within said well having a second sidewall angle measured from said plane of said top surface of said substrate, wherein said second sidewall angle is different from said first sidewall angle, and wherein at least one of said first and second sidewall angles is less than 85 degrees; and an isolation layer formed at least partially along at least one of said first and second sidewalls. ### Claim 10 (depends on 9) The pixel according to claim 9, wherein said first and second sidewalls have a vertical depth within a range of approximately 500 Å to approximately 5000 Å. ### Claim 11 (depends on 10) The pixel according to claim 10, wherein said vertical depth of said first and second sidewalls is within a range of approximately 1000 Å to approximately 3000 Å. ### Claim 12 (depends on 9) The pixel according to claim 9, wherein at least one of said first and second sidewall angles is within a range of approximately 15 degrees to approximately 70 degrees. ### Claim 13 (depends on 12) The pixel according to claim 12, wherein at least one of said first and second sidewall angles is within a range of approximately 60 degrees to approximately 70 degrees. ### Claim 14 (depends on 9) The pixel according to claim 9, wherein said first conductivity type is p-type. ### Claim 15 (depends on 9) The pixel according to claim 9, said isolation layer comprising a nitride. ### Claim 16 (depends on 9) The pixel according to claim 9, said isolation layer comprising an oxide. ### Claim 17 (depends on 9) The pixel according to claim 9, said isolation layer comprising a dielectric material. ### Claim 18 (depends on 9) The pixel according to claim 9, wherein said first angle is within a range of approximately 85 degrees to approximately 90 degrees. ### Claim 19 (depends on 18) The pixel according to claim 18, wherein said second angle is within a range of approximately 15 degrees to approximately 70 degrees. ### Claim 20 (depends on 18) The pixel according to claim 18, wherein said second angle is within a range of approximately 60 degrees to approximately 70 degrees. ### Claim 21 A pixel array comprising: a substrate; a plurality of photoconversion devices formed in said substrate; at least one well having a first conductivity type formed adjacent to a respective at least one of said photoconversion devices; and a trench formed within said well comprising: a first sidewall having a first sidewall angle measured from a plane of a top surface of said substrate; and a second sidewall having a second sidewall angle measured from said plane of said top surface of said substrate, wherein said second sidewall angle is different from said first sidewall angle, and wherein at least one of said first and second sidewall angles is less than 85 degrees. ### Claim 22 (depends on 21) The pixel array according to claim 21, further comprising: an isolation layer formed at least partially along at least one of said first and second sidewalls of said trench. ### Claim 23 (depends on 22) The pixel according to claim 22, said isolation layer comprising a nitride. ### Claim 24 (depends on 22) The pixel according to claim 22, said isolation layer comprising an oxide. ### Claim 25 (depends on 22) The pixel according to claim 22, said isolation layer comprising a dielectric material. ### Claim 26 (depends on 21) The pixel according to claim 21, wherein said first angle is within a range of approximately 85 degrees to approximately 90 degrees. ### Claim 27 (depends on 26) The pixel according to claim 26, wherein said second angle is within the range of approximately 15 degrees to approximately 70 degrees. ### Claim 28 (depends on 26) The pixel according to claim 26, wherein said second angle is within the range of approximately 60 degrees to approximately 70 degrees.