CMOS imager having a JFET adapted to detect photons and produce an amplified electrical signal
AssigneeESS Technology, Inc.
InventorsLester J. Kozlowski, Frank Chang, Wu-Jing Ho
Life of this patent
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Abstract
A photodetector is formed in a CMOS circuit using a junction field-effect transistor (JFET). The JFET/CMOS photodetector can be used to create an active pixel sensor for a CMOS digital imager, performing both photodetection and electrical signal amplification, allowing higher fill factors than with conventional APS imagers. A standard CMOS fabrication process is augmented with a small number of steps to integrate the JFET within the pixel, allowing the use of conventional CMOS fabrication plants.
Claims9
A complementary metal oxide semiconductor (CMOS) device comprising:
- a silicon substrate;
- a junction field-effect transistor (JFET) formed on a surface of the silicon substrate, the JFET including a photo-absorbing layer formed on the surface of the silicon substrate;
- an overglass layer formed over the JFET adapted to admit photons to the photo-absorbing layer of the JFET;
- and
- a readout switch transistor formed to be coupled to a drain terminal of the JFET;
- wherein the JFET detects incident photons admitted through the overglass layer and produces an amplified electrical signal corresponding to the photons detected, and wherein a source terminal of the readout switch transistor is connected to a bus and a resistor, forming a source follower circuit.
A complementary metal oxide semiconductor (CMOS) active pixel sensor (APS) pixel supported on a substrate, the CMOS APS pixel comprising:
- a junction field-effect transistor (JFET) adapted to detect photons and produce an amplified electrical signal corresponding to the photons detected;
- and
- a readout switch transistor coupled to a drain terminal of the JFET;
- wherein a source terminal of the readout switch transistor is connected to a bus and a resistor, forming a source follower circuit.
A complementary metal oxide semiconductor (CMOS) active pixel sensor (APS) pixel supported on a substrate, the CMOS APS pixel comprising:
- a junction field-effect transistor (JFET) adapted to detect photons and produce an amplified electrical signal corresponding to the photons detected;
- a readout switch transistor coupled to a drain terminal of the JFET;
- a first resistor connected between a gate terminal of the JFET and a drain terminal of the readout switch transistor;
- a second resistor connected between a source terminal of the JFET and the drain terminal of the readout switch transistor, wherein the first and second resistors provide positive feedback and laser trimmability, and
- wherein a source terminal of the readout switch transistor is connected to a bus and a current source, forming a source follower.
A digital camera comprising:
- a complementary metal oxide semiconductor (CMOS) active pixel sensor (APS) imager providing image data, the imager comprising:
- an array of CMOS APS pixels comprising a plurality of junction field-effect transistors (JFETs) adapted for photodetection and electrical signal amplification;
- and
- a readout switch transistor coupled to a drain terminal of the JFET;
- wherein a source terminal of the readout switch transistor is connected to a bus and a resistor, forming a source follower circuit.
Dependencies are inferred from the claim text.