Active pixel sensors with substantially planarized color filtering elements

• US 5,990,506 A
• Filed: 03/20/1997
• Issued: 11/23/1999
• Est. Priority Date: 03/20/1996
• Status: Expired due to Term

• Current Assignee: National Aeronautics and Space Administration (Government of the United States of America)
• Original Assignee: California Institute of Technology
• Inventors: Fossum, Eric R., Kemeny, Sabrina E.
• Primary Examiner(s): Abraham, Fetsum
• Application Number:
  US08/821,157
• Time in Patent Office: 978 Days
• Field of Search: 257/222, 257/225, 257/226, 257/227, 257/228, 257/232, 257/233, 257/234, 257/290-293, 257/239 W, 257/294, 349/78-80, 349/97, 349/104-109, 250/14, 250/27, 250/357, 250/365
• US Class Current: 257/294
• CPC Class Codes: G11C 19/282 with charge storage in a depletion layer, i.e. charge coupled devices [CCD]
• CPC Class Codes: H01L 27/14621 Colour filter arrangements
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14645 Colour imagers
• CPC Class Codes: H01L 27/14843 Interline transfer
• CPC Class Codes: H01L 27/14868 CCD or CID colour imagers
• CPC Class Codes: H01L 27/14887 Blooming suppression
• CPC Class Codes: H01L 31/02162 for filtering or shielding light, e.g. multicolour filters for photodetectors
• CPC Class Codes: H01L 31/0232 Optical elements or arrangements associated with the device H01L31/0236 takes precedence; for photovoltaic cells H01L31/054; for photovoltaic modules H02S40/20
• CPC Class Codes: H04N 25/616 involving a correlated sampling function, e.g. correlated double sampling [CDS] or triple sampling
• CPC Class Codes: H04N 25/77 Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components

Abstract

A semiconductor imaging system preferably having an active pixel sensor array compatible with a CMOS fabrication process. Color-filtering elements such as polymer filters and wavelength-converting phosphors can be integrated with the image sensor.

Claims

1. An integrated semiconductor imaging device, comprising:

a sensor array having a plurality of pixel circuits disposed relative to one another on a semiconductor substrate, each of said pixel circuits including an optical sensor to receive light and an electronic element having at least one active transistor to convert said light into an electrical signal, wherein said pixel circuits are operable to generate an indicia indicative of an input scene;

a first color filtering layer formed on said sensor array to cover a first portion of said sensor array and configured to transmit light in at least a first selected spectral bandwidth and absorb light that is substantially outside said first selected bandwidth, said optical sensor in each of said pixel circuits in said first portion being responsive in said first selected spectral bandwidth; and

a first transparent layer, formed on said sensor array and displaced relative to said first color filtering layer to cover a remaining portion of said sensor array that is not covered by said first color filtering layer, said first transparent layer and said first color filtering layer being substantially of a same thickness and forming a first planarized layer which has a substantially flat upper surface on said first sensor array to cover said pixel circuits.

2. A device as in claim 1, further comprising:

a second color filtering layer formed over said first planarized layer and disposed relative to said first color filtering layer to cover a second portion of said sensor array, said second color filtering layer operating to transmit light in at least a second selected spectral bandwidth and absorb light that is substantially outside said second selected bandwidth, said optical sensor in each of said pixel circuits in said second portion being responsive in said second selected spectral bandwidth;

a second transparent layer, formed over said first planarized layer, displaced relative to said second color filtering layer to cover a remaining portion of said first planarized layer that is not covered by said second color filtering layer, said second transparent layer and said second color filtering layer being substantially of a same thickness and forming a second planarized layer over said first planarized layer;

a third color filtering layer formed over said second planarized layer and disposed relative to said first and second color filtering layers to cover a third portion of said sensor array, said third color filtering layer operating to transmit light at least in a third selected spectral bandwidth and absorb light that is substantially outside said third selected bandwidth, said optical sensor in each of said pixel circuits in said third portion being responsive in said third selected spectral bandwidth; and

a third transparent layer, formed over said second planarized layer and displaced relative to said third color filtering layer to cover a remaining portion of said second planarized layer that is not covered by said third color filtering layer, said third transparent layer and said third color filtering layer being substantially of a same thickness and forming a third planarized layer over said second planarized layer, whereby each optical sensor in each of said pixel circuits receives a light beam that only transmits through one of said first, second and third color filtering layers.

3. A device as in claim 2, wherein said first color filtering layer has a first spatial pattern, said second color filtering layer has a second spatial pattern, and said third color filtering layer has a third spatial pattern.

4. A device as in claim 3, wherein said first, second, and third spatial patterns are arranged with respect to one another so that one of said pixels receiving light filtered by one of said three color filtering layers has two neighboring pixels each receiving light filtered by one of other two of said three color filtering layers.

5. A device as in claim 2, wherein at least one of said first, second, and third color filtering layers is made of a polymeric material.

6. A device as in claim 2, wherein at least one of said first, second, and third transparent layers is made of a polymeric material.

7. A device as in claim 2, further comprising a light coupling array of microlenses formed on said third planarized layer, each microlens in said light coupling array being positioned over a pixel circuit of said sensor array so that light received by said optical sensor passes through one of said microlenses and one of said color filtering layers.

8. An imaging system capable of color filtering, comprising:

a plurality of semiconductor substrates separated from one another;

a plurality of sensor arrays respectively formed on said substrates and each having a plurality of pixel circuits, each pixel circuit in each sensor array including an optical sensor to receive light and an electronic element having at least one active transistor to convert said light into an electrical signal, said sensor arrays disposed relative to one another to receive an input image and operable to respectively generate indicia of different colors of the input image; and

an electronic controller, coupled to said sensor arrays to correlate said indicia of different colors from said sensor arrays to compose a final image of said input image.

9. A device as in claim 8, wherein each of said sensor arrays comprises a light coupling array of microlenses formed over said pixel circuits, each microlens in said light coupling array being positioned over a pixel circuit of said first sensor array to couple light to said optical sensor in said pixel circuit.

10. A system as in claim 8, wherein said plurality of sensor arrays include:

a first sensor array having a first color filtering layer formed to cover respective pixel circuits, operating to transmit light in a first selected spectral bandwidth and absorb light that is substantially outside said first selected bandwidth, said first sensor array producing a first image representing said input image in said first selected bandwidth;

a second sensor array having a second color filtering layer formed to cover respective pixel circuits, operating to transmit light in a second selected spectral bandwidth different from said first selected bandwidth and absorb light that is substantially outside said second selected bandwidth, said second sensor array producing a second image representing said input image in said second selected bandwidth; and

a third sensor array having a third color filtering layer formed to cover respective pixel circuits, operating to transmit light in a third selected spectral bandwidth different from said first and second selected bandwidths and absorb light that is substantially outside said third selected bandwidth, said third sensor array producing a third image representing said input image in said third selected bandwidth, wherein said electronic controller correlates said first, second, and third images to form said final image with colors based on said first, second, and third selected bandwidths.

11. A system as in claim 10, wherein at least one of said first, second, and third color filtering layers is made of a polymeric material.

12. An integrated imaging sensor, comprising:

an active pixel sensor array, having a plurality of active pixels responsive to photons in a first spectral range, each of said active pixels having at least one active transistor and operating to covert said photons into an electrical signal; and

a phosphor layer formed on top of said sensor array, operable to convert radiation in a second spectral range into said first spectral range, said second spectral range being out of said first spectral range, whereby said integrated imaging sensor is operable to detect a signal in said second spectral range.

13. A sensor as in claim 12, wherein said first spectral range is within a range in which a silicon-based photosensor is responsive.

14. A sensor as in claim 12, wherein said second spectral range is within ultraviolet range or in X-ray range.

15. An integrated semiconductor imaging device, comprising:

a sensor array having a plurality of active pixel circuits disposed relative to one another on a semiconductor substrate, each of said active pixel circuits including an optical sensor to receive light and at least one active transistor to convert said light into an electrical signal, wherein said pixel circuits are operable to generate an indicia indicative of an input scene; and

a substantially planarized color filtering layer formed on said sensor array to cover said active pixel circuits and configured to effect color filtering and color separation on said input scene, said color filtering layer formed of an array of color filtering regions which are arranged relative to one another in said color filtering layer and have an one-to-one correspondence to said active pixel circuits, wherein said color filtering regions include at least three different types corresponding to three different transmitted colors.

16. Device as in claim 15, further comprising a light coupling array of microlenses formed over said color filtering layer, each microlens in said light coupling array being positioned over an active pixel circuit of said first sensor array to couple light to said optical sensor in said active pixel circuit through said color filtering layer.

17. A method for constructing and operating an integrated semiconductor imaging device, comprising:

forming a plurality of pixel circuits disposed relative to one another on a semiconductor substrate to provide a sensor array, each of said pixel circuits including an optical sensor to receive light and an electronic element having at least one active transistor to convert said light into an electrical signal, wherein said pixel circuits are operable to generate an indicia indicative cf an input scene; and

separating frequency components in said input scene into three different frequency ranges by using first, second and third color filtering layers sequentially formed on said sensor array, wherein each of said color filtering layers includes a plurality of color filtering regions covering selected pixel circuits of said sensor array and a plurality of transparent regions disposed relative to said color filtering regions to form a planarized layer and to cover pixel circuits that are not covered by said color filtering regions, and color filtering regions in one layer being of a same type that is different from color filtering regions of another layer.

18. A method as in claim 17, further comprising forming a microlens array over said third color filtering layer to couple said input scene to said pixel circuits through said third, second and first color filtering layers.

19. A method for constructing and operating an integrated semiconductor imaging device, comprising:

forming a plurality of pixel circuits disposed relative to one another on a semiconductor substrate to provide a sensor array, each of said pixel circuits including an optical sensor to receive light and an electronic element having at least one active transistor to convert said light into an electrical signal, wherein said pixel circuits are operable to generate an indicia indicative of an input scene;

separating frequency components in said input scene into three different frequency ranges by using a substantially planarized color filtering layer formed on said sensor array to cover said pixel circuits, said color filtering layer formed of an array of color filtering regions which are arranged relative to one another in said color filtering layer and have an one-to-one correspondence to said pixel circuits, wherein said color filtering regions include at least three different types corresponding to said three different frequency ranges; and

forming a microlens array over said third color filtering layer to couple said input scene to said pixel circuits through said third, second and first color filtering layers.