# US 12,224,368 B1 · Optoelectronic device including photodiode having buried layer with different thicknesses > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,224,368 B1 - Document ID: US12224368B1 - Status: Granted - Kind: B1 - Application number: 18/666,787 - Filed: 2024-05-16 - Granted: 2025-02-11 - Earliest claimed: 2024-05-16 - Assignees: Globalfoundries Singapore Pte. Ltd. - Applicants: GlobalFoundries Singapore Pte. Ltd. - Inventors: Francesco Gramuglia; Eng Huat Toh; Ping Zheng - Web page: https://patentgrep.com/patent/US12224368B1 ## CPC - H10F 30/225: the potential barrier working in avalanche mode, e.g. avalanche photodiodes - H10F 71/00: Manufacture or treatment of devices covered by this subclass (patterning processes to connect thin photovoltaic cells in integrated devices, or assemblies of multiple devices, having photovoltaic cells H10F19/33; manufacture or treatment of encapsulations or containers for integrated devices, or assemblies of multiple devices, having photovoltaic cells H10F19/80; manufacture or treatment of integrated devices, or assemblies of multiple devices, comprising at least one element in which radiation controls the flow of current H10F39/00) - H10F 71/121: {The active layers comprising only Group IV materials} - H10F 77/14: Shape of semiconductor bodies; Shapes, relative sizes or dispositions of semiconductor regions within semiconductor bodies - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION ## Abstract The present disclosure generally relates to semiconductor devices for use in optoelectronic/photonic applications and integrated circuit (IC) chips. More particularly, the present disclosure relates to devices containing photodiodes such as avalanche photodiodes (APDs) and single photon avalanche diodes (SPADs). The present disclosure may provide a device including a substrate, a first well of a first conductivity type in the substrate, a second well of a second conductivity type in the substrate, and a buried layer of the second conductivity type in the substrate. The buried layer may be below the first well and the second well. The buried layer may have a first section and a second section, in which the first section has a larger thickness than the second section. ## Claims ### Claim 1 A device comprising: a substrate; a first well of a first conductivity type in the substrate, the first well has a side boundary; a second well of a second conductivity type in the substrate, the second conductivity type is of an opposite conductivity type to the first conductivity type, the first well is concentric with and laterally surrounded by the second well; and a buried layer of the second conductivity type in the substrate, the buried layer is below the first well and the second well, the buried layer has a first section and a second section, the first section has a larger thickness than the second section, the first section is concentric with and laterally surrounded by the second section, wherein the first section of the buried layer is aligned vertically below and in direct contact with the first well, and wherein the first section of the buried layer has a side boundary, and the side boundary of the first section of the buried layer is coplanar with the side boundary of the first well. ### Claim 2 (depends on 1) The device of claim 1, wherein the first section of the buried layer has a bottom boundary, the second section of the buried layer has a bottom boundary, and the bottom boundary of the first section of the buried layer is lower than the bottom boundary of the second section of the buried layer. ### Claim 3 (depends on 2) The device of claim 2, wherein the second section of the buried layer is in direct contact with the second well. ### Claim 4 (depends on 2) The device of claim 2, wherein the first well has a top boundary, and the bottom boundary of the first section of the buried layer has the same area as the top boundary of the first well. ### Claim 5 (depends on 3) The device of claim 3, wherein the second well has a bottom boundary, the second section of the buried layer has a top boundary, and the top boundary of the second section of the buried layer directly contacts the bottom boundary of the second well. ### Claim 6 (depends on 3) The device of claim 3, wherein the second section of the buried layer has a side boundary, the second well has an outer side boundary, and the outer side boundary of the second well is coplanar with the side boundary of the second section of the buried layer. ### Claim 7 (depends on 6) The device of claim 6, wherein the second well has an inner side boundary, and the inner side boundary of the second well is laterally spaced apart from the side boundary of the first well. ### Claim 8 (depends on 3) The device of claim 3, further comprising a third well in the substrate, the third well having the same conductivity type as the first well, the third well laterally surrounds and is concentric with the second well and the first well. ### Claim 9 (depends on 8) The device of claim 8, further comprising a fourth well in the substrate, the fourth well having the same conductivity type as the first well, the fourth well is laterally surrounded by and in direct contact with the first well. ### Claim 10 (depends on 1) The device of claim 1, wherein the second section of the buried layer has a lower dopant concentration than the first section of the buried layer. ### Claim 11 A device comprising: a substrate; a first well of a first conductivity type in the substrate, the first well has a side boundary; a second well of a second conductivity type in the substrate, the second conductivity type is of an opposite conductivity type to the first conductivity type, the first well is concentric with and laterally surrounded by the second well; and a buried layer of the second conductivity type in the substrate, the buried layer is below the first well and the second well, the buried layer has a first section and a second section, the first section is concentric with and laterally surrounded by the second section, the second section of the buried layer has a lower dopant concentration than the first section of the buried layer, wherein the first section of the buried layer is aligned vertically below and in direct contact with the first well, and wherein the first section of the buried layer has a side boundary, and the side boundary of the first section of the buried layer is coplanar with the side boundary of the first well. ### Claim 12 (depends on 11) The device of claim 11, wherein the first section of the buried layer has a larger thickness than the second section of the buried layer. ### Claim 13 (depends on 12) The device of claim 12, wherein the first section of the buried layer has a bottom boundary, the second section of the buried layer has a bottom boundary, and the bottom boundary of the first section of the buried layer is lower than the bottom boundary of the second section of the buried layer. ### Claim 14 (depends on 12) The device of claim 12, wherein the second section of the buried layer has a side boundary, the second well has an outer side boundary and an inner side boundary, wherein the outer side boundary of the second well is coplanar with the side boundary of the second section of the buried layer, and wherein the inner side boundary of the second well is laterally spaced apart from the side boundary of the first well. ### Claim 15 (depends on 14) The device of claim 14, wherein the second well has a bottom boundary, the second section of the buried layer has a top boundary, and the top boundary of the second section of the buried layer directly contacts the bottom boundary of the second well. ### Claim 16 A method of forming a device, the method comprising: forming a first well of a first conductivity type in a substrate, the first well has a side boundary; forming a second well of a second conductivity type in the substrate, the second conductivity type is of an opposite conductivity type to the first conductivity type, the first well is formed to be concentric with and laterally surrounded by the second well; and forming a buried layer of the second conductivity type in the substrate, the buried layer is formed below the first well and the second well, the buried layer has a first section and a second section, the first section of the buried layer is formed with a larger thickness than the second section of the buried layer, the first section of the buried layer is formed to be concentric with and laterally surrounded by the second section of the buried layer, wherein the first section of the buried layer is formed to be aligned vertically below and in direct contact with the first well, and wherein the first section of the buried layer has a side boundary, and the side boundary of the first section of the buried layer is coplanar with the side boundary of the first well. ### Claim 17 (depends on 16) The method of claim 16, wherein the second section of the buried layer is formed with a lower dopant concentration than the first section of the buried layer. ### Claim 18 (depends on 16) The method of claim 16, wherein the first section of the buried layer and the first well are formed using the same patterned mask layer. ### Claim 19 (depends on 16) The method of claim 16, wherein the first section of the buried layer is formed using two doping processes.