# US 12,113,138 B2 · Semiconductor devices with single-photon avalanche diodes and light scattering structures > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,113,138 B2 - Document ID: US12113138B2 - Status: Granted - Kind: B2 - Application number: 18/194,714 - Filed: 2023-04-03 - Published: 2023-08-10 - Granted: 2024-10-08 - Earliest claimed: 2019-12-04 - Assignees: Semiconductor Components Industries, LLC - Applicants: Semiconductor Components Industries, LLC - Inventors: Swarnal Borthakur; Marc Allen Sulfridge; Andrew Eugene Perkins - Web page: https://patentgrep.com/patent/US12113138B2 ## CPC - H10F 77/959: {for devices working in avalanche mode} - G02B 3/06: with cylindrical or toric faces - H04N 25/773: comprising photon counting circuits, e.g. single photon detection [SPD] or single photon avalanche diodes [SPAD] - H10F 30/225: the potential barrier working in avalanche mode, e.g. avalanche photodiodes - H10F 39/024: {of coatings or optical elements} - H10F 39/18: Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors - H10F 39/184: {Infrared image sensors} - H10F 39/8023: {Disposition of the elements in pixels, e.g. smaller elements in the centre of the imager compared to larger elements at the periphery} - H10F 39/8053: {Colour filters} - H10F 39/8063: {Microlenses} - H10F 39/8067: {Reflectors} - H10F 39/807: {Pixel isolation structures} - H10F 77/413: {directly associated or integrated with the devices, e.g. back reflectors (directly associated or integrated with photovoltaic cells H10F77/42)} - H10F 77/45: Wavelength conversion means, e.g. by using luminescent material, fluorescent concentrators or up-conversion arrangements - H04N 25/63: applied to dark current - H10F 39/199: {Back-illuminated image sensors} - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract An imaging device may include single-photon avalanche diodes (SPADs). To improve the sensitivity and signal-to-noise ratio of the SPADs, light scattering structures may be formed in the semiconductor substrate to increase the path length of incident light through the semiconductor substrate. The light scattering structures may include a low-index material formed in trenches in the semiconductor substrate. One or more microlenses may focus light onto the semiconductor substrate. Areas of the semiconductor substrate that receive more light from the microlenses may have a higher density of light scattering structures to optimize light scattering while mitigating dark current. ## Claims ### Claim 1 A semiconductor device comprising: a substrate; a photosensitive area formed in the substrate; a microlens formed over the photosensitive area; and a plurality of light scattering structures in the substrate over the photosensitive area, wherein, in a first portion of the substrate, there is a first non-zero number of the light scattering structures per unit area, wherein, in a second portion of the substrate, there is a second non-zero number of the light scattering structures per the unit area, wherein the second non-zero number is greater than the first non-zero number, and wherein the second portion of the substrate forms a ring around the first portion of the substrate. ### Claim 2 A semiconductor device comprising: a substrate; a photosensitive area formed in the substrate; a microlens formed over the photosensitive area; and a plurality of light scattering structures in the substrate over the photosensitive area, wherein, in a first portion of the substrate, there is a first non-zero number of the light scattering structures per unit area, wherein, in a second portion of the substrate, there is a second non-zero number of the light scattering structures per the unit area, wherein the second non-zero number is greater than the first non-zero number, wherein the microlens has an outer periphery, and wherein the first and second portions of the substrate are both, in a direction parallel to a surface normal of the substrate, directly overlapped by an area defined by the outer periphery of the microlens. ### Claim 3 (depends on 1) The semiconductor device defined in claim 1, wherein the microlens is configured to focus a greater amount of light to the second portion of the substrate than the first portion of the substrate. ### Claim 4 (depends on 1) The semiconductor device defined in claim 1, wherein the microlens is a toroidal microlens. ### Claim 5 (depends on 4) The semiconductor device defined in claim 4, wherein the toroidal microlens has a central opening and wherein the semiconductor device includes an additional microlens that is formed in the central opening. ### Claim 6 (depends on 4) The semiconductor device defined in claim 4, wherein the toroidal microlens has a central opening, wherein the first portion of the substrate is overlapped by the central opening, and wherein the second portion of the substrate is not overlapped by the central opening. ### Claim 7 (depends on 1) The semiconductor device defined in claim 1, wherein each one of the plurality of light scattering structures comprises a trench in a surface of the substrate and material formed in the trench that has a lower refractive index than the substrate. ### Claim 8 (depends on 7) The semiconductor device defined in claim 7, wherein the material formed in the trench comprises a passivation layer and a buffer layer. ### Claim 9 (depends on 1) The semiconductor device defined in claim 1, wherein the plurality of light scattering structures comprises a first light scattering structure having a first width and a second light scattering structure having a second width that is different than the first width. ### Claim 10 (depends on 1) The semiconductor device defined in claim 1, wherein there is a gradual change in the number of the light scattering structures per the unit area between the first non-zero number and the second non-zero number. ### Claim 11 A semiconductor device comprising: a substrate; a photosensitive area formed in the substrate; a microlens formed over the photosensitive area; and a plurality of light scattering structures in the substrate over the photosensitive area, wherein, in a first portion of the substrate, there is a first non-zero number of the light scattering structures per unit area, wherein, in a second portion of the substrate, there is a second non-zero number of the light scattering structures per the unit area, wherein the second non-zero number is greater than the first non-zero number, and wherein the first portion of the substrate forms a ring around the second portion of the substrate. ### Claim 12 (depends on 11) The semiconductor device defined in claim 11, wherein the microlens is configured to focus a greater amount of light to the second portion of the substrate than the first portion of the substrate. ### Claim 13 (depends on 11) The semiconductor device defined in claim 11, wherein the microlens is a toroidal microlens. ### Claim 14 (depends on 13) The semiconductor device defined in claim 13, wherein the toroidal microlens has a central opening and wherein the semiconductor device includes an additional microlens that is formed in the central opening. ### Claim 15 (depends on 13) The semiconductor device defined in claim 13, wherein the toroidal microlens has a central opening, wherein the first portion of the substrate is overlapped by the central opening, and wherein the second portion of the substrate is not overlapped by the central opening. ### Claim 16 (depends on 11) The semiconductor device defined in claim 11, wherein each one of the plurality of light scattering structures comprises a trench in a surface of the substrate and material formed in the trench that has a lower refractive index than the substrate. ### Claim 17 (depends on 16) The semiconductor device defined in claim 16, wherein the material formed in the trench comprises a passivation layer and a buffer layer. ### Claim 18 (depends on 11) The semiconductor device defined in claim 11, wherein the plurality of light scattering structures comprises a first light scattering structure having a first width and a second light scattering structure having a second width that is different than the first width. ### Claim 19 (depends on 11) The semiconductor device defined in claim 11, wherein there is a gradual change in the number of the light scattering structures per the unit area between the first non-zero number and the second non-zero number.