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US 11,698,296 B2Granted
Light sensor using pixel optical diffraction gratings having different pitches
AssigneesSTMicroelectronics (Crolles 2) SAS, STMicroelectronics S.r.l.
InventorsStephane Monfray, Olivier Le Neel, Frederic Boeuf
Life of this patent
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Abstract
A light sensor includes a semiconductor substrate supporting a number of pixels. Each pixel includes a photoconversion zone extending in the substrate between a front face and a back face of the substrate. An optical diffraction grating is arranged over the back face of the substrate at a position facing the photoconversion zone of the pixel. For at least two different pixels of the light sensor, the optical diffraction gratings have different pitches. Additionally, the optical grating of each pixel is surrounded by an opaque wall configured to absorb at operating wavelengths of the sensor.
Claims18
A light sensor, comprising:
- a semiconductor substrate;
- and
- a plurality of pixels, wherein each pixel comprises:
- a photoconversion zone extending in the semiconductor substrate between a front face and a back face of the semiconductor substrate;
- an optical diffraction grating positioned over the back face of the semiconductor substrate and facing the photoconversion zone of the pixel;
- and
- a wall configured to be absorbent at operating wavelengths of the sensor, said wall positioned to laterally surround the optical diffraction grating of the pixel and extend heightwise from the back face of the semiconductor substrate at least up to a level of the optical diffraction grating of the pixel;
- wherein the optical diffraction grating of one pixel of said plurality of pixels and the optical diffraction grating of another pixel of said plurality of pixels have different pitches.
5 more elements
A light sensor, comprising:
- a semiconductor substrate;
- and
- a plurality of pixels, wherein each pixel comprises:
- a photoconversion zone extending in the semiconductor substrate between a front face and a back face of the semiconductor substrate;
- an optical diffraction grating positioned over the back face of the semiconductor substrate and facing the photoconversion zone of the pixel;
- and
- a device configured to prevent a zero order propagation of the light transmitted by the optical diffraction grating of the pixel from reaching the photoconversion zone of the pixel;
- wherein the optical diffraction grating of one pixel of said plurality of pixels and the optical diffraction grating of another pixel of said plurality of pixels have different pitches.
5 more elements
A method for manufacturing a sensor, comprising:
- depositing a layer of a material transparent at operating wavelengths of the sensor on a back face of a semiconductor substrate provided with photoconversion zones extending in the semiconductor substrate between a front face and the back face of the semiconductor substrate;
- depositing a layer of a first material on the layer of the transparent material;
- etching openings through the layer of first material so as to define an optical diffraction grating therein positioned above each photoconversion zone;
- depositing a layer of a second material that covers the first and is in contact with the first material;
- wherein said first material is one of:
- opaque at said operating wavelengths or has an optical index at said operating wavelengths that is at least one and a half times greater than an optical index of the second material;
- wherein the optical diffraction grating for two different photoconversion zones have different pitches;
- etching trenches extending through both the layer of the second material and the layer of transparent material to reach said back face, wherein the trenches have a shape that laterally surrounds each optical diffraction grating;
- and
- filling said trenches with a material that is absorbent at said operating wavelengths.
7 more elements
A method for analysis of light sensed by a sensor, comprising:
- receiving light to be analyzed by a plurality of pixels of the sensor, wherein each pixel has an optical diffraction grating over a photoconversion zone, and wherein the optical diffraction grating of one pixel of said plurality of pixels and the optical diffraction grating of another pixel of said plurality of pixels have different pitches;
- generating by each pixel of the sensor an output value of the pixel representative of the quantity of light to be analyzed that is received by the pixel;
- performing a calibration step wherein the sensor is illuminated successively with light of different types and the sensor stores, for each of the lights of different types, a map of the output values of the pixels;
- and
- determining a type of said received light to be analyzed by comparing the maps stored by the sensor during the calibration step to a map of the output values of the pixels generated when the sensor is illuminated with the light to be analyzed.
2 more elements
Dependencies are inferred from the claim text.