Image sensor with photosensitive thin film transistors and dark current compensation
First Claim
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1. An image sensor for sensing received image, comprising:
- a substrate;
a photo TFT disposed on the substrate to generate a photocurrent responsive to the received image, the photo TFT including, a gate electrode, a source electrode coupled to the gate electrode, a drain electrode, and a semiconductor layer coupled to the source and drain electrodes; and
a reference TFT disposed on the substrate and coupled to the photo TFT, the reference TFT having dimensions substantially similar to the photo TFT and providing a compensating dark current, the reference TFT including, a gate electrode, a source electrode coupled to the gate electrode, a drain electrode, and a semiconductor layer coupled to the source and drain electrodes.
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Abstract
An image sensor array includes image sensors having photo TFTs to generate photocurrent in response to received images. The photo TFTs each have their respective gate electrodes shorted to source electrodes to increase generated photocurrent. Each photo TFT is coupled to a reference TFT to compensate for dark current in a corresponding photo TFT. Storage capacitors are coupled to each photo TFT and discharged upon generation of a photocurrent. Each storage capacitor is coupled to a readout TFT that passes a current from the storage capacitor to a data line. Data lines indicate location of the received image on the image sensor array.
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Citations
28 Claims
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1. An image sensor for sensing received image, comprising:
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a substrate;
a photo TFT disposed on the substrate to generate a photocurrent responsive to the received image, the photo TFT including, a gate electrode, a source electrode coupled to the gate electrode, a drain electrode, and a semiconductor layer coupled to the source and drain electrodes; and
a reference TFT disposed on the substrate and coupled to the photo TFT, the reference TFT having dimensions substantially similar to the photo TFT and providing a compensating dark current, the reference TFT including, a gate electrode, a source electrode coupled to the gate electrode, a drain electrode, and a semiconductor layer coupled to the source and drain electrodes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An image sensor for sensing a received image, comprising:
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a substrate;
a photo TFT disposed on the substrate to generate a photocurrent responsive to the received image, the photo TFT including, a gate electrode, a source electrode coupled to the gate electrode, a drain electrode, and a semiconductor layer coupled to the source and drain electrodes;
a storage capacitor disposed on the substrate and coupled to the source electrode and drain electrode of the photo TFT, the storage capacitor storing a charge generated by the photocurrent;
a readout TFT disposed on the substrate, including, a gate electrode coupled to a select line, a source electrode coupled to the drain electrode of the photo TFT, a drain electrode coupled to a data line, and a semiconductor layer coupled to the source and drain electrodes; and
a reference TFT disposed on the substrate and coupled to the photo TFT, the reference TFT having dimensions substantially similar to the photo TFT and providing a compensating dark current, the reference TFT including, a gate electrode, a source electrode coupled to the gate electrode, a drain electrode, and a semiconductor layer coupled to the source and drain electrodes. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. An image sensor for sensing a received image, comprising:
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a substrate;
a plurality of first bias lines disposed on the substrate;
a plurality of second bias lines disposed on the substrate;
a plurality of data lines disposed on the substrate;
a plurality of select lines disposed on the substrate;
a plurality of photo TFTs disposed on the substrate to generate a photocurrent responsive to the received image, each photo TFT including, a gate electrode coupled to a corresponding first bias line, a source electrode, a drain electrode, and a semiconductor layer coupled to the source and drain electrodes;
a plurality of storage capacitors disposed on the substrate, each storage capacitor coupled to the source electrode and drain electrode of a corresponding photo TFT, each storage capacitor storing a charge generated by a photocurrent;
a plurality of readout TFTs disposed on the substrate, each readout TFT coupled to a corresponding storage capacitor and including, a gate electrode coupled to a corresponding select line, a source electrode coupled to the drain electrode of a corresponding photo TFT and coupled to the storage capacitor, a drain electrode coupled to a corresponding data line, and a semiconductor layer coupled to the source and drain electrodes, wherein each readout TFT passes a current to a corresponding date line in response to the discharge of a corresponding storage capacitor; and
a plurality of reference TFTs disposed on the substrate, each reference TFT coupled to a corresponding photo TFT, each reference TFT having dimensions substantially similar to the corresponding photo TFT and providing a compensating dark current, each reference TFT including, a gate electrode, a source electrode coupled to the gate electrode and a corresponding second bias lines, a drain electrode coupled to a corresponding photo TFT, and a semiconductor layer coupled to the source and drain electrodes. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28)
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Specification
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Current AssigneeApple Inc.
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Original AssigneePlanar Systems Incorporated (Leyard Optoelectronic Co., Ltd.)
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Inventorsden Boer, Willem
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Primary Examiner(s)CHOWDHURY, TARIFUR RASHID
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Application NumberUS10/457,931Publication NumberTime in Patent Office554 DaysField of Search349/42, 349/48, 257/59, 257/72, 250/208.1, 345/55, 345/92US Class Current349/48CPC Class CodesH01L 27/14609 Pixel-elements with integra...H01L 27/14643 Photodiode arrays; MOS imagers
