METHOD AND APPARATUS FOR BACKSIDE ILLUMINATED IMAGE SENSORS USING CAPACITIVELY COUPLED READOUT INTEGRATED CIRCUITS
First Claim
1. An active pixel image sensor (APS) configured to sense a photon received by a pixel surface, the APS comprising:
- a first integrated circuit (IC) layer having a first back surface coupled to the pixel surface for receiving the photon, a first front surface having a first plate, and an analog device formed between the first back and front surfaces, the analog device coupled to the pixel surface and the first plate; and
a second IC layer formed underneath the first IC layer, the second IC layer having second front and back surfaces and a digital device formed between the second front and back surfaces, the second front surface having a second plate configured to be capacitively coupled to the first plate of the first IC layer, the digital device coupled to the second plate of the second front surface.
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Accused Products
Abstract
The images sensor includes a readout circuit capacitatively coupled to a memory circuit. The readout circuit includes: (i) a photon detector to receive a plurality of photons and to provide a charge signal corresponding to the received photons, (ii) a resettable integrator that is reset multiple times over a single exposure time and provides an analog representation of the incident photons during the last integration cycle, and (iii) a comparator that monitors the integrator output and generates a reset pulse when the integrator reaches a built-in threshold value. The memory circuit includes: (i) a receiver circuit that detects the output of the digital driver in the front-end readout circuit via capacitive coupling and generates a digital voltage pulse for each received signal, and (ii) a digital counting memory to count the received pulses to provide a coarse digital representation of how many times the integrator is reset.
65 Citations
26 Claims
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1. An active pixel image sensor (APS) configured to sense a photon received by a pixel surface, the APS comprising:
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a first integrated circuit (IC) layer having a first back surface coupled to the pixel surface for receiving the photon, a first front surface having a first plate, and an analog device formed between the first back and front surfaces, the analog device coupled to the pixel surface and the first plate; and a second IC layer formed underneath the first IC layer, the second IC layer having second front and back surfaces and a digital device formed between the second front and back surfaces, the second front surface having a second plate configured to be capacitively coupled to the first plate of the first IC layer, the digital device coupled to the second plate of the second front surface. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An active pixel image sensor (APS) configured to sense a photon received by a pixel surface, the APS comprising:
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a first layer having; an integrator coupled to the pixel surface and configured to generate a cumulative signal based on the photon for a predefined exposure time and generate an integrator output signal based on the cumulative signal, a comparator coupled to the integrator and configured to generate a comparator output signal when the cumulative signal reaches a predefined threshold level, and a first plate coupled to the comparator and configured to receive the comparator output signal; and a second layer formed underneath the first layer, the second layer having; a second plate configured to establish a capacitive coupling with the first plate and to sense and receive the comparator output signal via the capacitive coupling, and a receiver coupled to the second plate and configured to generate a digital pulse based on the received comparator output signal. - View Dependent Claims (12, 13, 14)
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15. A method for sensing a photon received by a pixel, comprising the steps of:
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converting, using a first layer device, the received photon to a charge; generating, using the first layer device, a fine quantized analog output signal based on the charge; and generating, using a second layer device formed beneath the first layer device, a coarse quantized digital output signal based on the charge. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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22. A method for sensing one or more photons received by a pixel, comprising the steps of:
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generating, using an integrator, a cumulative signal based on the one or more received photons; generating, using a comparator, a comparator output signal when the cumulative signal reaches a predefined threshold; and generating, using a receiver, a digital pulse based on the comparator output signal. - View Dependent Claims (23, 24, 25, 26)
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Specification