# US 11,079,270 B2 · Optical sensor and apparatus comprising an optical sensor having a photodetector and a semiconductor guard ring are dimensioned so that a fill factor of each pixel is less than or equal to 50% > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,079,270 B2 - Document ID: US11079270B2 - Status: Granted - Kind: B2 - Application number: 16/740,676 - Filed: 2020-01-13 - Published: 2020-07-16 - Granted: 2021-08-03 - Earliest claimed: 2019-01-16 - Assignees: STMicroelectronics (Research & Development) Limited; STMicroelectronics (Grenoble 2) SAS - Applicants: STMicroelectronics (Research & Development) Limited; STMicroelectronics (Grenoble 2) SAS - Inventors: Jeffrey M. Raynor; Sophie Taupin; Jean-Jacques Rouger; Pascal Mellot - Web page: https://patentgrep.com/patent/US11079270B2 ## CPC - G01J 1/0214: {Constructional arrangements for removing stray light} - G01J 1/4204: {with determination of ambient light (solar light G01J2001/4266)} - G01J 1/44: Electric circuits {(for command of an exposure part G03B7/02)} - G01J 3/0262: {Constructional arrangements for removing stray light} - H04N 25/57: Control of the dynamic range - H04N 25/77: Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components - H04N 25/772: comprising A/D, V/T, V/F, I/T or I/F converters - H04N 25/773: comprising photon counting circuits, e.g. single photon detection [SPD] or single photon avalanche diodes [SPAD] - H10F 39/103: {the at least one element covered by H10F30/00 having potential barriers, e.g. integrated devices comprising photodiodes or phototransistors} - H10F 39/107: {having multiple elements covered by H10F30/00 in a repetitive configuration, e.g. radiation detectors comprising photodiode arrays} - H10F 77/953: {for devices having potential barriers} - H10W 42/00: Arrangements for protection of devices (arrangements for thermal protection H10W40/00) - G01J 2001/446: {Photodiode} - G01J 2001/448: {Array [CCD]} - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION - H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10 ## Abstract An optical sensor includes pixels. Each pixel has a photodetector and a semiconductor guard ring around the photodetector. The photodetector and the semiconductor guard ring are dimensioned so that a fill factor of the pixel is less than or equal to 50%. ## Claims ### Claim 1 An optical sensor comprising a plurality of pixels arranged in an array with a pitch, wherein each pixel comprises: a photodetector and a semiconductor guard ring around the photodetector; wherein the photodetector and the semiconductor guard ring are dimensioned so that a fill factor of the pixel defined by a ratio of an area of the photodetector to an area defined by the pitch for the plurality of pixels is less than or equal to 50%. ### Claim 2 (depends on 1) The optical sensor according to claim 1, wherein the photodetector and the semiconductor guard ring are dimensioned so that the fill factor of the pixel is greater than or equal to 33%. ### Claim 3 (depends on 1) The optical sensor according to claim 1, wherein the plurality of pixels are part of a one dimensional array of pixels aligned along a first direction and wherein a width of the semiconductor guard ring along the first direction is greater than a width of the semiconductor guard ring along a second direction perpendicular to the first direction. ### Claim 4 (depends on 1) The optical sensor according to claim 1, wherein the plurality of pixels are part of a two dimensional array of pixels aligned along a first direction and a second direction perpendicular to the first direction and wherein a width of the semiconductor guard ring along the first direction is equal to a width of the semiconductor guard ring along the second direction. ### Claim 5 (depends on 1) The optical sensor according to claim 1, wherein the optical sensor is an ambient light sensor. ### Claim 6 (depends on 1) The optical sensor according to claim 1, further comprising, for each pixel, a readout circuit configured to determine an ambient light level based on a voltage across the photodetector. ### Claim 7 (depends on 6) The optical sensor according to claim 6, wherein the readout circuit is configured to determine the ambient light level based on a number of times the voltage across the photodetector is reset to a predetermined reverse bias voltage over an exposure time. ### Claim 8 (depends on 7) The optical sensor according to claim 7, wherein the readout circuit is configured to repeat the following steps over the exposure time: connect the photodetector to a reverse bias voltage supply so that a voltage across the photodetector is reset to the predetermined reverse bias voltage; and disconnect the photodetector from the reverse bias voltage supply so that the voltage across the photodetector decreases upon photons being absorbed and carriers generated thereby being collected. ### Claim 9 (depends on 8) The optical sensor according to claim 8, wherein the readout circuit is configured to: reset a fine value at the beginning of the exposure time; and increment the fine value at a periodicity less than a periodicity at which a coarse value is incremented. ### Claim 10 (depends on 9) The optical sensor according to claim 9, wherein the readout circuit is configured to combine the coarse value and the fine value at the end of the exposure time to determine the ambient light level. ### Claim 11 (depends on 7) The optical sensor according to claim 7, wherein the readout circuit is configured to determine the ambient light level based on the voltage across the photodetector at the end of the exposure time. ### Claim 12 (depends on 11) The optical sensor according to claim 11, wherein the readout circuit is configured to repeat the following steps over the exposure time: connect the photodetector to a reverse bias voltage supply so that a voltage across the photodetector is reset to the predetermined reverse bias voltage; and disconnect the photodetector from the reverse bias voltage supply so that the voltage across the photodetector decreases upon photons being absorbed and carriers generated thereby being collected. ### Claim 13 (depends on 12) The optical sensor according to claim 12, wherein the readout circuit is configured to: reset a fine value at the beginning of the exposure time; and increment the fine value at a periodicity less than a periodicity at which a coarse value is incremented. ### Claim 14 (depends on 13) The optical sensor according to claim 13, wherein the readout circuit is configured to combine the coarse value and the fine value at the end of the exposure time to determine the ambient light level. ### Claim 15 (depends on 1) The optical sensor according to claim 1, wherein each pixel comprises a band pass filter arranged over the photodetector. ### Claim 16 (depends on 15) The optical sensor according to claim 15, wherein the band pass filter is arranged over the semiconductor guard ring. ### Claim 17 (depends on 1) The optical sensor according to claim 1, wherein each pixel comprises an optically reflective coating arranged over the semiconductor guard ring. ### Claim 18 (depends on 1) The optical sensor according to claim 1, wherein the optical sensor is a component of an apparatus selected from the group consisting of: a mobile phone, a tablet computer, a laptop computer, a desktop computer, a video game console, a smart card reader, a video camera, a television, a vehicle. ### Claim 19 (depends on 1) The optical sensor according to claim 1, further comprising, for each pixel, a readout circuit comprising: a reset transistor having a conduction terminal coupled to the photodetector; a source-follower transistor having a control terminal coupled to the photodetector and a conduction terminal generating an output voltage corresponding to a voltage across the photodetector; a comparator having a first input configured to receive the output voltage and a second input configured to receive a reference voltage, said comparator generating a signal configured to control operation of the reset transistor so as to reset the photodetector. ### Claim 20 (depends on 19) The optical sensor according to claim 19, further comprising a counting circuit configured to count the signal generated by the comparator.