Image sensors having multiple photoelectric conversion devices therein
Image sensors include a second photoelectric conversion device disposed in a lower portion of a substrate and a first photoelectric conversion device extending between the secondary photoelectric conversion device and a light receiving surface of the substrate. Electrical isolation between the first and second photoelectric conversion devices is provided by a photoelectron barrier, which may be an optically transparent electrically insulating material. MOS transistors may be utilized to transfer photoelectrons generated within the first and second photoelectric conversion devices to a floating diffusion region within the image sensor. These transistors may represent one example of means for transferring photoelectrons generated in the first and second photoelectric conversion devices to a floating diffusion region in the substrate, in response to first and second gating signals, respectively. The first and second gating signals may be active during non-overlapping time intervals.
1. An image sensor, comprising:
a second photoelectric conversion device disposed in a substrate;
a first photoelectric conversion device extending between said second photoelectric conversion device and a light receiving surface of the substrate;
a photoelectron barrier extending between said first and second photoelectric conversion devices;
means, electrically coupled to first and second cathodes of said first and second photoelectric conversion devices, for transferring photoelectrons generated in said first and second photoelectric conversion devices to a floating diffusion region in the substrate in response to first and second gating signals, respectively, which are active during non-overlapping time intervals; and
a reflection film on a surface of the substrate opposite the light receiving surface for reflecting incident light penetrating the second photoelectric conversion device to inside of the second photoelectric conversion device.
2. The image sensor of claim 1 , wherein said first and second photoelectric conversion devices comprise first and second PN rectifying junctions, respectively; and wherein the second PN rectifying junction is more lightly doped with P-type and N-type impurities relative to the first PN rectifying junction.
3. The image sensor of claim 2 , wherein said photoelectron barrier comprises an optically transparent electrically insulating material.
4. The image sensor of claim 1 , wherein said photoelectron barrier comprises a material selected from a group consisting of silicon dioxide, silicon nitride and silicon oxynitride.
5. The image sensor of claim 3 , wherein said photoelectron barrier forms a first interface with a P-type region in said first photoelectric conversion device and a second interface with a P-type region in said second photoelectric conversion device.
6. The image sensor of claim 1 , wherein said transferring means comprises first and second MOS transistors having respective source/drain regions that form non-rectifying junctions with the floating diffusion region; and wherein the first and second MOS transistors have gate electrodes that are responsive to the first and second gating signals, respectively.
7. An image sensor comprising:
a first photoelectric conversion element generating a first electrical signal in response to an incident light;
a photoelectron barrier at a lower part of the first photoelectric conversion element;
a second photoelectric conversion element, which is at a lower part of the photoelectron barrier, generating a second electrical signal in response to an incident light penetrating the photoelectron barrier; and
a reflection film at a lower part of the second photoelectric conversion element and reflecting an incident light penetrating the second photoelectric conversion element to inside of the second photoelectric conversion element, wherein the reflection film is at a surface of the substrate opposite the light receiving surface.
8. The image sensor of claim 7 , wherein the photoelectron barrier comprises a silicon oxide film (SiO2), a silicon nitride film (SiN) or a silicon oxynitride film (SiON).
9. The image sensor of claim 7 , further comprising a white filter at an upper part of the first photoelectric conversion element,
wherein the first photoelectric conversion element generates the first electrical signal in response to wavelengths in a blue region of the incident light,
wherein the second photoelectric conversion element generates the second electrical signal in response to wavelengths in a green region or in a blue region of an incident light penetrating the photoelectron barrier.
10. The image sensor of claim 7 , further comprising a magenta filter at an upper part of the first photoelectric conversion element,
wherein the first photoelectric conversion element generates the first electrical signal in response to wavelengths in a blue region of the incident light,
wherein the second photoelectric conversion element generates the second electrical signal in response to wavelengths in a red region of an incident light penetrating the photoelectron barrier.
11. The image sensor of claim 7 , further comprising a green filter at an upper part of the first photoelectric conversion element,
wherein the first photoelectric conversion element generates the first electrical signal in response to wavelengths in a green region of the incident light,
wherein the second photoelectric conversion element generates the second electrical signal in response to wavelengths in the green region of an incident light penetrating the photoelectron barrier.
12. An image sensor comprising:
a transparent electrode;
a first photoelectric conversion element for generating a first electrical signal in response to an incident light penetrating the transparent electrode;
a second photoelectric conversion element for generating a second electrical signal in response to the incident light penetrating the first photoelectric conversion element; and
a reflection film on a surface of the substrate opposite the light receiving surface for reflecting the incident light penetrating the second photoelectric conversion element to inside of the second photoelectric conversion element.
13. The image sensor of claim 12 , wherein a bias voltage is supplied to the transparent electrode.
14. The image sensor of claim 12 , wherein the image sensor is a backside illumination (BIS) CMOS image sensor.
15. An image processing apparatus comprising:
the image sensor of claim 7 ; and
a processor circuit configured to control operations of the image sensor.
16. The image processing apparatus of claim 15 , wherein the image sensor further comprises a reflection film which is at a lower part of the second photoelectric conversion element and reflects an incident light penetrating the second photoelectric conversion element to inside of the second photoelectric conversion element.
17. An image processing apparatus comprising:
the image sensor of claim 12 ; and
a processor circuit configured to control operations of the image sensor.