Color responsive imaging device employing wavelength dependent semiconductor optical absorption

• US 4,613,895 A
• Filed: 11/13/1978
• Issued: 09/23/1986
• Est. Priority Date: 03/24/1977
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Burkey, Bruce C., Spaulding, Richard A., VanHeyningen, Roger S., Wolf, Edward L.
• Primary Examiner(s): RICHARDSON, ROBERT
• Application Number:
  US05/959,830
• Time in Patent Office: 2,871 Days
• Field of Search: 358/41, 358/43, 358/44, 358/48, 358/213, 357/30, 357/24, 357/29
• US Class Current: 348/272
• CPC Class Codes: H01L 27/14621 Colour filter arrangements
• CPC Class Codes: H01L 27/148 Charge coupled imagers individual charge coupled devices H01L29/765
• CPC Class Codes: H01L 27/14868 CCD or CID colour imagers
• CPC Class Codes: H01L 29/1062 of charge coupled devices
• CPC Class Codes: H04N 23/84 for processing colour signals

Abstract

An image sensing element in a solid state imaging device is provided with a plurality of superposed channels disposed at respective distances from a light receiving surface of the device, each of such channels having a different characteristic spectral response due to the differential absorption of light by a semiconductor. By so disposing the channels, the device becomes a color imaging sensor having optimized resolution. The top channel, i.e. the channel nearest the surface of the device, may be either a "surface" channel or a "buried" channel, the lower channel(s) being buried channels. Depending upon the design of the element, either electrons or holes may be accumulated as photocharges in respective superposed channels. The color photocharges generated in respective channels of such an image sensing element are simultaneously moved in a plurality of superposed channels by a multiple superposed channel signal handling device such as a multiple channel charge coupled device (CCD), thus the solid state imaging device does not require special timing networks to correct for phase differences between color signals which result from a common point within an image.

Claims

1. In a solid state device of the type comprising a semiconductor material having a plurality of regions of alternating dopant types within the material, the device having a light receiving surface, a photosensitive element for simultaneously generating a plurality of photosignals, comprising:

a. first channel means for collecting a first photosignal generated, in response to light falling on said light receiving surface, in a first region extending to a first depth, with respect to said surface, within said semiconductor material, said first channel means having a predetermined spectral response; and

b. buried channel means, disposed beneath said first channel means, with respect to said surface, for collecting a second photosignal generated, in response to light falling on said surface, in a second region extending to a second depth greater than said first depth, said second channel means having a predetermined spectral response different from said spectral response of said first channel due to the differential absorption of light by the semiconductor material, said first and second photosignal generating regions being superposed within said element.

2. The invention claimed in claim 1 wherein said first channel means comprises a surface channel.

3. The invention claimed in claim 1 wherein said first and said second photosignals are comprised of carriers of opposite polarity types, and wherein said photosensitive element further comprises:

dual-action channel defining means for confining both of said polarity type carriers in their respective channels.

4. The invention claimed in claim 3 wherein said dual-action channel defining means, comprises:

a heavily doped channel stopping region disposed adjacent said channel means and a thick field oxide disposed over said channel stopping region and extending partially over said channel means, whereby, the channel potentials bend in one direction beneath said thick field oxide, and in the opposite direction beneath said channel stopping region, to thereby define potential wells for carriers of both polarity types.

5. A solid state color responsive imaging device, comprising:

a. a semiconductor substrate having a light receiving surface;

b. first photoresponsive means disposed at a first depth beneath said surface for generating a first photosignal in response to light of a first range of wavelengths impinging on said surfae; and

c. second photoresponsive means disposed directly beneath said first means at a second depth beneath said surface for generating a second photosignal in response to light, in a range of wavelengths narrower than said first range due to the differential absorption by said semiconductor, impinging on said surface,

thereby providing an imaging device having enhanced spatial resolution and high efficiency of utilization of incident light.

6. A solid state color responsive imaging device, comprising:

a. a semiconductor substrate having a light receiving surface;

b. first photoresponsive means disposed at a first depth beneath said surface for generating a first photosignal in response to light of a first range of wavelengths impinging on said surface;

c. second photoresponsive means disposed directly beneath said first means at a second depth beneath said surface for generating a second photosignal in response to light, of a second range of wavelengths different from said first range, impinging on said surface, and

d. charge coupled device means for moving said first and second photosignals simultaneously within said device at said respective depths, whereby phase differences between respective color signals arising from respective photoresponsive means beneath a common point on said surface of said device are obviated.

7. In a solid state color imaging array, an image element comprising

a semiconductor substrate having a light receiving surface and a plurality of superposed light responsive channels for generating a corresponding plurality of photosignals, said channels being disposed at different distances from said light receiving surface such that respective channels receive different wavelengths of light due to the differential absorption of light by the semiconductor material, whereby a plurality of color signals are generated by one image element when exposed to a plurality of wavelengths of light, thereby enhancing the spatial resolution of the imaging array and affording efficient utilization of the light energy incident on the image element.

8. A solid state color imaging device comprising:

a. a semiconductor substrate having a light receiving surface and a plurality of superposed light-responsive channels for generating a corresponding plurality of photosignals, said channels being disposed at different distances from said light receiving surface such that respective channels receive different wavelengths of light due to the differential absorption of light by the semiconductor material, whereby a plurality of photosignals representing different colors are generated in said channels when said device is exposed to a plurality of wavelengths of light; and

b. charge coupled device means for moving said plurality of color signals simultaneously within said imaging device, whereby phase differences between respective color signals arising from a common point within an image are obviated.

9. A solid state imaging device comprising:

a. a chip of semiconductor material comprising at least six layers of alternately different dopant types;

b. means for scavenging mobile majority charge carriers from said first, third and fifth layers to form respective buried charge transporting channels in those layers;

c. nonconductive transparent means covering the surface of the said first layer; and

d. transparent electrode means on said transparent nonconductive means.

10. The device of claim 9 wherein the thicknesses of said layers are such that, in response to incident white light falling on the electrode means on the device, substantially no blue light penetrates to said third layer and substantially no green light penetrates to said fifth layer.

11. The device of claim 9 wherein said chip is comprised of silicon, and said first layer is less than about 0.7 μ

m in thickness.

12. The device of claim 9 wherein said chip is comprised of silicon and the combined thickness of said first, second and third layers is less than about 2.6 μ

m, and the combined thickness of said first, second, third and fourth layers is greater than 2.6 μ

m.

13. The devide of claim 9 wherein said chip is comprised of silicon, said first layer is less than about 0.7 μ

m in thickness, and the combined thickness of the first, second and third layers is less than about 2.6 μ

m, and the combined thickness of said first, second, third and fourth layers is greater than 2.6 μ

m.

14. An image sensor device comprising:

a. a wafer of silicon;

b. a transparent oxide of silicon on said wafer;

c. a plurality of rows of transparent electrode means on said oxide,

said wafer having at least six contiguous layers, each being doped with impurity atoms, and each being doped with a type impurity different than any of its contiguous layers, said layers being disposed so that said oxide is contiguous with said first layer; and

d. respective ohmic row contacts to the first, third and fifth layers for removing mobile majority carriers from those layers.

15. The image sensor device of claim 14 wherein the layers of the device are such that first, second and third colors are absorbed within the combination of said first and second layers, said second and third colors are absorbed within the combination of said second, third and fourth layers, and said third color is absorbed within the combination of said fourth, fifth and sixth layers.

16. The sensor device of claim 14 wherein the first layer is less than about 0.7 μ

m in thickness.

17. The device of claim 14 wherein the combined thickness of said first, second and third layers is less than about 2.6 μ

m, and the combined thickness of said first, second, third and fourth layers is greater than 2.6 μ

m.

18. The sensor of claim 14 wherein:

a. the first layer is less than about 0.7 μ

m in thickness;

b. the combined thickness of said first, second and third layers is less than about 2.6 μ

m; and

c. the combined thickness of said first, second, third and fourth layers is greater than 2.6 μ

m.

19. In combination:

an imaging device comprising;

A.

a. a chip of silicon having at least six layers, each layer being doped with impurity atoms, and each being doped with an impurity type different than a layer contiguous therewith;

b. a transparent oxide of silicon covering the first of said layers;

c. transparent electrode means covering said oxide;

the first layer being less than 0.7 μ

m in thickness, the combined thickness of said first, second and third layers being less than 2.6 μ

m, and the combined thickness of said first, second, third and fourth layers being greater than about 2.6 μ

m;

d. first, second and third ohmic contacts respectively to said first, third and fifth layers; and

B.

a. means coupled to said first and second ohmic contacts for algegraically combining signals appearing at those contacts; and

b. means coupled to the said second and third ohmic contacts for algebraically combining signals appearing at those contacts.

20. A buried channel charge coupled imaging device comprising:

a. first, second, third, fourth, fifth and sixth silicon layers which are respectively doped alternately with different type impurity atoms;

b. a transparent nonconductive coating over the first of said layers;

c. a row of transparent electrodes over said nonconductive coating;

the first layer being less than about 0.7 μ

m in thickness;

the combined thickness of said first, second and third layers being less than 2.6 μ

m; and

the combined thickness of said first, second, third and fourth layers being greater than 2.6 μ

m;

the first, third and fifth layers, respectively fanning out to either side of and beyond said row of electrodes, and

d. ohmic contacts respectively to the fanned out portions of the first, third and fifth layers.

21. A multi-spectral charge coupled device for generating a plurality of signals representative of the spectral content of impinging photons comprising:

a plurality of adjacent semiconductor layers arranged to generate a hole and an electron for each of said impinging photons;

first and second collector means arranged to collect said generated holes or electrons and respectively generate first and second signals representative of said collected holes or electrons;

said semiconductor layers having a predetermined optical absorption coefficient and said first and second collector means arranged such that said first and second signals are indicative of the spectral content of the impinging photons.

22. A multi-spectral charge coupled device as recited in claim 21, wherein

said plurality of semiconductor layers comprise multiple buried layer including a plurality of layers for generating holes, and

a plurality of layers for generating electrons interleaved with said plurality of layers for generating holes.

24. A device in accordance with claims 21 and 23, wherein the ratio of the output signals from said first and second collector means are representative of the wavelength of said impinging photons.

25. A device in accordance with claim 24, wherein said device is arranged to contain a plurality of regions in a plane parallel to said surface of said device, and wherein the wavelength of said impinging photons is determined by the relationship between the output signals of adjacent regions.

26. A device in accordance with claims 21 or 23, wherein said device is arranged to contain a plurality of regions in a plane parallel to said surface of said device, and wherein the wavelength of said impinging photons is determined by the relationship between the output signals of adjacent regions.

23. A multi-spectral charge coupled device for generating a plurality of signals representative of the spectral content of a stream of photons impinging on the surface of said device comprising:

a plurality of adjacent semiconductor layers arranged to generate a hole-electron pair for each photon of said photon stream, said hole-electron pair generated at a mean depth from the surface of said device which is a function of the wavelength of said respective photon;

first and second collector means arranged to collect said generated holes or electrons, said first and second collector means arranged at different depths from the surface of said device whereby the efficiency of collection of said holes or electrons are respectively different functions of the depth from the surface of said device at which said holes and electrons are generated; and

output means, operatively connected to said first and second collector means for providing output signals representative of said collected holes or electrons whereby said signals are indicative of the spectral content of said impinging stream of photons.

27. In a multi-spectral charge coupled device for generating a plurality of signals representative of the spectral content of impinging photons and comprising a plurality of adjacent semiconductor layers arranged to generate hole-electron pairs for each photon of a photon stream impinging upon the surface of said device, the improvement comprising first and second collector means for collecting said holes or said electrons;

further comprising output means operatively connected to said first and second collector means for producing signals representative of said collected holes or electrons, whereby the ratio of said output signals representative of said collected holes or electrons is representative of the wavelength of said impinging photons.