# US 9,437,645 B1 · Composite grid structure to reduce cross talk in back side illumination image sensors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,437,645 B1 - Document ID: US9437645B1 - Status: Granted - Kind: B1 - Application number: 14/663,918 - Filed: 2015-03-20 - Published: 2016-09-22 - Granted: 2016-09-06 - Earliest claimed: 2015-03-20 - Assignees: Taiwan Semiconductor Manufacturing Company, Ltd. - Applicants: Taiwan Semiconductor Manufacturing Co., Ltd. - Inventors: Keng-Yu Chou; Chun-Hao Chuang; Chien-Hsien Tseng; Shyh-Fann Ting; Wei-Chieh Chiang; Yuichiro Yamashita - Web page: https://patentgrep.com/patent/US9437645B1 ## CPC - H10F 39/182: {Colour image sensors} - H10F 39/024: {of coatings or optical elements} - H10F 39/026: {Wafer-level processing} - H10F 39/199: {Back-illuminated image sensors} - H10F 39/8053: {Colour filters} - H10F 39/8063: {Microlenses} - H10F 39/8067: {Reflectors} - 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 semiconductor structure for back side illumination (BSI) pixel sensors is provided. Photodiodes are arranged within a semiconductor substrate. A composite grid includes a metal grid and a low refractive index (low-n) grid. The metal grid includes first openings overlying the semiconductor substrate and corresponding to ones of the photodiodes. The low-n grid includes second openings overlying the semiconductor substrate and corresponding to ones of the photodiodes. Color filters are arranged in the first and second openings of the corresponding photodiodes and have a refractive index greater than a refractive index of the low-n grid. Upper surfaces of the color filters are offset relative to an upper surface of the composite grid. A method for manufacturing the BSI pixel sensors is also provided. ## Claims ### Claim 1 A semiconductor structure for back side illumination (BSI) pixel sensors, the semiconductor structure comprising: photodiodes arranged within a semiconductor substrate; a composite grid including: a metal grid including first openings overlying the semiconductor substrate and corresponding to the photodiodes; and a low refractive index (low-n) grid including second openings overlying the semiconductor substrate and corresponding to the photodiodes; and color filters arranged in the first and second openings and having a refractive index greater than a refractive index of the low-n grid, wherein upper surfaces of the color filters are offset relative to an upper surface of the composite grid. ### Claim 2 (depends on 1) The semiconductor structure according to claim 1, wherein the upper surfaces of the color filters overhang the upper surface of the composite grid. ### Claim 3 (depends on 1) The semiconductor structure according to claim 1, wherein the upper surfaces of the color filters are recessed relative to the upper surface of the composite grid. ### Claim 4 (depends on 1) The semiconductor structure according to claim 1, further including: an integrated circuit comprising the semiconductor substrate and a back-end-of-line (BEOL) metallization stack underlying the semiconductor substrate. ### Claim 5 (depends on 1) The semiconductor structure according to claim 1, wherein the metal grid and the low-n grid share a layout, and wherein the low-n grid overlies the metal grid. ### Claim 6 (depends on 1) The semiconductor structure according to claim 1, wherein the first openings, the second openings, and the photodiodes share a footprint, and wherein the first and second openings are centered on centers of the corresponding photodiodes. ### Claim 7 (depends on 1) The semiconductor structure according to claim 1, wherein the first openings and the second openings are laterally offset from the photodiodes, so that the metal grid and the low-n grid partially mask the photodiodes. ### Claim 8 (depends on 1) The semiconductor structure according to claim 1, wherein the metal grid and the low-n grid share a layout, and wherein the low-n grid is laterally offset from the metal grid so sidewalls of the metal and low-n grids abut. ### Claim 9 (depends on 1) The semiconductor structure according to claim 1, wherein one of the color filters partially fills the first and second openings corresponding to a first one of the photodiodes, and partially fills the first and second openings corresponding to a second one of the photodiodes that neighbors the first one of the photodiodes. ### Claim 10 A semiconductor structure for back side illumination (BSI) pixel sensors, the semiconductor structure comprising: a semiconductor substrate arranged over a back-end-of-line (BEOL) metallization stack and accommodating photodiodes; a composite grid arranged over the semiconductor substrate and comprising a dielectric grid and a conductive grid, wherein the dielectric and conductive grids border and collectively define openings overlying corresponding ones of the photodiodes; and color filters arranged in the openings and having top surfaces that are vertically offset from a top surface of the composite grid. ### Claim 11 (depends on 10) The semiconductor structure according to claim 10, wherein the dielectric grid has a low refractive index relative to the color filters. ### Claim 12 (depends on 10) The semiconductor structure according to claim 10, wherein the conductive and dielectric grids have a same layout and are arranged such that sidewalls of the conductive grid are aligned with sidewalls of the dielectric grid, and wherein a bottom surface of the dielectric grid is arranged over a top surface of the conductive grid. ### Claim 13 (depends on 12) The semiconductor structure according to claim 12, wherein one of the color filters has a top surface elevated relative to the top surface of the composite grid, and wherein the one of the color filters further overhangs the top surface of the composite grid on opposite sides of a corresponding one of the openings. ### Claim 14 (depends on 12) The semiconductor structure according to claim 12, wherein one of the color filters has a top surface recessed below the top surface of the composite grid. ### Claim 15 (depends on 12) The semiconductor structure according to claim 12, wherein one of the color filters has a top surface elevated relative to the top surface of the composite grid, and wherein the one of the color filters straddles a segment of the composite grid that separates neighboring ones of the openings. ### Claim 16 (depends on 10) The semiconductor structure according to claim 10, wherein the conductive grid is arranged laterally adjacent to the dielectric grid, and wherein the openings individually have a stepped profile and are asymmetric about vertical axes arranged respectively at width-wise centers of the openings. ### Claim 17 (depends on 16) The semiconductor structure according to claim 16, wherein one of the color filters has a top surface elevated relative to the top surface of the composite grid, and wherein the one of the color filters further overhangs the top surface of the composite grid on opposite sides of a corresponding one of the openings. ### Claim 18 (depends on 16) The semiconductor structure according to claim 16, wherein one of the color filters has a top surface recessed below the top surface of the composite grid. ### Claim 19 (depends on 10) The semiconductor structure according to claim 10, wherein the composite grid further comprises a hard mask grid overlying the dielectric grid and defining the top surface of the composite grid, and wherein the dielectric, conductive, and hard mask grids collectively define the openings. ### Claim 20 A semiconductor structure for back side illumination (BSI) pixel sensors, the semiconductor structure comprising: a semiconductor substrate arranged over a back-end-of-line (BEOL) metallization stack and accommodating photodiodes; a composite grid arranged over the semiconductor substrate and comprising a dielectric grid, a conductive grid, and a hard mask grid, wherein the hard mask grid is arranged over the dielectric grid and has sidewalls aligned with sidewalls of the dielectric grid, and wherein the dielectric, conductive, and hard mask grids collectively define openings overlapping corresponding ones of the photodiodes; a dielectric layer conformally lining the composite grid; and color filters arranged in the openings and having top surfaces vertically offset from a top surface of the composite grid by more than a thickness of the dielectric layer.