Storage pixel sensor and array with compression

• US 6,512,544 B1
• Filed: 06/17/1998
• Issued: 01/28/2003
• Est. Priority Date: 06/17/1998
• Status: Expired due to Term

• Current Assignee: Foveon, Inc. (Avis Budget Group Incorporated)
• Original Assignee: Foveon, Inc. (Avis Budget Group Incorporated)
• Inventors: Merrill, Richard B., Lyon, Richard F.
• Primary Examiner(s): Garber, Wendy R.
• Assistant Examiner(s): Villecco, John M.
• Application Number:
  US09/098,688
• Time in Patent Office: 1,686 Days
• Field of Search: 348/299, 348/297, 348/298, 348/304, 348/302, 348/314, 348/294, 257/204, 257/277, 257/291, 257/292, 250/208.1
• US Class Current: 348/302
• CPC Class Codes: H01L 27/1443 with at least one potential jump or surface barrier
• CPC Class Codes: H01L 27/14609 Pixel-elements with integrated switching, control, storage or amplification elements scanning details of imagers (circuitry of solid-state image sensors H04N25/00); circuitry of imagers H04N25/70
• CPC Class Codes: H04N 25/575 with a response composed of multiple slopes
• CPC Class Codes: H04N 25/59 by controlling the amount of charge storable in the pixel, e.g. modification of the charge conversion ratio of the floating node capacitance
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors
• CPC Class Codes: H04N 25/771 comprising storage means other than floating diffusion

Abstract

A storage pixel sensor disposed on a semiconductor substrate comprises a photosensor. At least one nonlinear capacitive element is coupled to the photosensor. At least one nonlinear capacitive element is arranged to have a compressive photocharge-to-voltage gain function. An amplifier has an input coupled to the nonlinear capacitor and an output. Other, non-capacitive elements may be employed to produce a compressive photo-charge-to-voltage gain having at least one breakpoint.

Claims

1. A pixel sensor disposed on a semiconductor substrate comprising:

a MOS capacitive element having a gate terminal coupled to a voltage source and a diffusion terminal;

a photodiode having a first terminal coupled to a first potential and a second terminal coupled to said diffusion terminal of said MOS capacitive element;

a semiconductor reset switch having a first terminal coupled to said second terminal of the photodiode and a second terminal coupled to a reset potential that reverse biases said photodiode;

a semiconductor transfer switch having a first terminal coupled to said second terminal of said photodiode and a second terminal;

a semiconductor amplifier having an input coupled to said second terminal of said semiconductor transfer switch and an output;

said semiconductor reset switch and said semiconductor transfer switch each having a control element coupled to a control circuit for selectively activating said semiconductor reset switch and said semiconductor transfer switch.

2. The storage pixel sensor of claim 1 wherein said voltage source is adjustable.

3. The storage pixel sensor of claim 1 further including:

a light shield disposed over portions of the semiconductor substrate comprising said second terminal of the semiconductor transfer switch and said input of said semiconductor amplifier to prevent substantially all photons from entering thereon; and

minority carrier rejection means for preventing substantially all minority carriers generated in the semiconductor substrate from entering said portions of said semiconductor substrate.

4. A storage pixel sensor disposed on a semiconductor substrate comprising:

a MOS capacitive storage element having a gate terminal coupled to a voltage source and a diffusion terminal;

a photodiode having a first terminal coupled to a first potential and a second terminal;

a semiconductor reset switch having a first terminal coupled to said second terminal of the photodiode and a second terminal coupled to a reset potential that reverse biases said photodiode;

a semiconductor transfer switch having a first terminal coupled to said second terminal of the photodiode and a second terminal coupled to said diffusion terminal of said MOS capacitive storage element;

a semiconductor amplifier having an input coupled to said diffusion terminal of said MOS capacitive storage element and an output;

said semiconductor reset switch and said semiconductor transfer switch each having a control element coupled to a control circuit for selectively activating said semiconductor reset switch and said semiconductor transfer switch.

5. The storage pixel sensor of claim 4 wherein said voltage source is adjustable.

6. The storage pixel sensor of claim 4 further including:

a light shield disposed over portions of the semiconductor substrate comprising said second terminal of the semiconductor transfer switch, said diffusion terminal of said MOS capacitive storage element and said input of said semiconductor amplifier to prevent substantially all photons from entering thereon; and

minority carrier rejection means for preventing substantially all minority carriers generated in the semiconductor substrate from entering said portions of said semiconductor substrate.

7. A pixel sensor comprising:

a photosensor;

at least one nonlinear capacitor element coupled to said photosensor;

at least one nonlinear circuit element arranged to yield a compressive photocharge-to-voltage gain function coupled to said photosensor; and

an amplifier having an input, said input coupled to said nonlinear capacitor element and to said at least one nonlinear circuit element, said amplifier also having an output.

8. The pixel sensor of claim 7 wherein said photosensor is a photodiode.

9. The pixel sensor of claim 7 wherein said at least one nonlinear capacitive storage element comprises a MOS capacitor including a first plate formed from a channel region in a semiconductor substrate coupled to said photosensor and a second plate formed from a gate coupled to a voltage source.

10. The pixel sensor of claim 7 wherein the compressive photocharge-to-voltage function is a single-break function.

11. The pixel sensor of claim 7 wherein the compressive photocharge-to-voltage function is a multiple-break function.

12. The pixel sensor of claim 11 wherein the compressive photocharge-to-voltage function is a double break function.

13. The pixel sensor of claim 7 wherein said nonlinear circuit element comprises an adjustable barrier.

14. A pixel sensor, formed on a semiconductor substrate, comprising:

a photosensor, said photosensor comprises a photodiode having a first terminal and a second terminal;

a nonlinear capacitive element arranged to have a compressive photocharge-to-voltage gain coupled to said photosensor, said nonlinear capacitive element comprises a MOS capacitor having a gate plate coupled to a voltage and a diffusion terminal coupled to the second terminal of said photodiode;

a semiconductor reset switch having a first terminal coupled to said photosensor and a second terminal coupled to a reset potential, said first terminal of said semiconductor reset switch is coupled to said second terminal of the photodiode and said second terminal of said semiconductor reset switch is coupled to a reset potential that reverse biases said photodiode;

a semiconductor amplifier having an input coupled to said photosensor and an output;

said semiconductor reset switch having a control element coupled to a control circuit for selectively activating said semiconductor reset switch.

15. The photosensor of claim 14 wherein said semiconductor reset switch and said amplifier each comprise a MOS transistor.

16. A pixel sensor comprising:

a photosensor;

at least one nonlinear capacitor element coupled to said photosensor;

an amplifier having an input, said input coupled to said nonlinear capacitor element, said amplifier also having an output, said amplifier comprises a MOS transistor having a gate and wherein said at least one nonlinear capacitor element comprises gate capacitance of said MOS transistor; and

at least one nonlinear circuit element arranged to yield a compressive photocharge-to-voltage gain function coupled to said photosensor.

17. The pixel sensor of claim 16 wherein said at least one nonlinear circuit element comprises said MOS transistor coupled as a source follower having a drain coupled to a source of pulsed potential.

18. A pixel sensor comprising:

a photosensor;

at least one nonlinear circuit element arranged to yield a compressive photocharge-to-voltage gain function coupled to said photosensor;

an amplifier having an input, said input coupled to at least one nonlinear capacitor element and to said at least one nonlinear circuit element, said amplifier also having an output;

a first one of said at least one nonlinear circuit elements comprises said amplifier implemented as a MOS transistor coupled as a source follower having a drain coupled to a source of pulsed potential; and

a second one of said at least one nonlinear circuit elements comprises an adjustable barrier.