IMAGE SENSORS WITH HYBRID THREE-DIMENSIONAL IMAGING

• US 20180213205A1
• Filed: 01/20/2017
• Published: 07/26/2018
• Est. Priority Date: 01/20/2017
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: OH, Minseok
• Granted Patent: US 10,271,037 B2
• Time in Patent Office: Days
• CPC Class Codes: H01L 27/14621 Colour filter arrangements
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14634 Assemblies, i.e. Hybrid structures
• CPC Class Codes: H01L 27/14636 Interconnect structures
• CPC Class Codes: H01L 27/14645 Colour imagers
• CPC Class Codes: H01L 27/14649 Infrared imagers
• CPC Class Codes: H01L 27/14654 Blooming suppression
• CPC Class Codes: H04N 13/218 using spatial multiplexing
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths
• CPC Class Codes: H04N 25/133 including elements passing panchromatic light, e.g. filters passing white light
• CPC Class Codes: H04N 25/622 by controlling anti-blooming drains
• CPC Class Codes: H04N 25/704 Pixels specially adapted for focusing, e.g. phase difference pixel sets
• CPC Class Codes: H04N 25/778 comprising amplifiers shared between a plurality of pixels, i.e. at least one part of the amplifier must be on the sensor array itself
• CPC Class Codes: H04N 25/79 Arrangements of circuitry being divided between different or multiple substrates, chips or circuit boards, e.g. stacked image sensors

Abstract

Image sensors may include hybrid three-dimensional imaging pixel groups. The pixel groups may be capable of obtaining both phase detection information and time-of-flight information. A pixel group may have first and second photodiodes covered by a single microlens that are used to obtain phase detection information. The microlens may also cover a third photodiode that obtains time-of-flight information. The first and second photodiodes may be formed in a first substrate whereas the third photodiode may be formed in a second substrate. The first and second substrates may be connected by a metal interconnect layer.

Claims

1. An imaging system comprising an image sensor, the image sensor comprising:

a first substrate;

a second substrate;

an interconnect layer that couples the first substrate to the second substrate;

a first photodiode that is formed in the first substrate;

a second photodiode that is formed in the first substrate;

a third photodiode that is formed in the second substrate; and

a microlens that covers the first, second, and third photodiodes, wherein the first and second photodiodes are configured to obtain phase detection information and wherein the third photodiode is configured to obtain time-of-flight information.

2. The imaging system defined in claim 1, the image sensor further comprising:

a first floating diffusion region formed in the second substrate; and

a second floating diffusion region formed in the second substrate.

3. The imaging system defined in claim 2, the image sensor further comprising:

a first transfer transistor configured to transfer charge from the first photodiode to the first floating diffusion region;

a second transfer transistor configured to transfer charge from the second photodiode to the second floating diffusion region;

a third transfer transistor configured to transfer charge from the third photodiode to the first floating diffusion region; and

a fourth transfer transistor configured to transfer charge from the third photodiode to the second floating diffusion region.

4. The imaging system defined in claim 3, wherein the interconnect layer comprises a first interconnect formed between the first floating diffusion region and the first transfer transistor and wherein the interconnect layer comprises a second interconnect formed between the second floating diffusion region and the second transfer transistor.

5. The imaging system defined in claim 4, the image sensor further comprising:

a bias voltage supply terminal;

a first anti-blooming transistor that is interposed between the first photodiode and the bias voltage supply terminal; and

a second anti-blooming transistor that is coupled between the second photodiode and the bias voltage supply terminal.

6. The imaging system defined in claim 4, the image sensor further comprising:

a first reset transistor coupled between the first floating diffusion region and a first bias voltage supply terminal;

a second reset transistor coupled between the second floating diffusion region and a second bias voltage supply terminal;

a first source follower transistor coupled to the first floating diffusion region;

a first row select transistor coupled to the first source follower transistor;

a second source follower transistor coupled to the second floating diffusion region; and

a second row select transistor coupled to the second source follower transistor.

8. The imaging system defined in claim 1, further comprising:

a light source configured to emit light, wherein the third photodiode is configured to receive the light from the light source to obtain the time-of-flight information.

21. The imaging system defined in claim 1, further comprising:

a single color filter element that covers the first photodiode, the second photodiode, and the third photodiode.

22. The imaging system defined in claim 1, wherein the first photodiode, the second photodiode, and the third photodiode are the only photodiodes covered by the micro lens.

23. The imaging system defined in claim 2, the image sensor further comprising:

a first transfer transistor configured to transfer charge from the first photodiode to the first floating diffusion region; and

a second transfer transistor configured to transfer charge from the second photodiode to the second floating diffusion region.

7. (canceled)

9. An image sensor comprising:

a first photodiode;

a second photodiode;

a third photodiode;

a microlens that covers the first, second, and third photodiodes;

a first floating diffusion region;

a second floating diffusion region;

a first transfer transistor configured to transfer charge from the first photodiode to the first floating diffusion region;

a second transfer transistor configured to transfer charge from the second photodiode to the second floating diffusion region;

a third transfer transistor configured to transfer charge from the third photodiode to the first floating diffusion region; and

a fourth transfer transistor configured to transfer charge from the third photodiode to the second floating diffusion region.

10. The image sensor defined in claim 9, further comprising:

a first reset transistor coupled between the first floating diffusion region and a first bias voltage supply terminal; and

a second reset transistor coupled between the second floating diffusion region and a second bias voltage supply terminal.

11. The image sensor defined in claim 10, further comprising:

a first source follower transistor coupled to the first floating diffusion region;

a first row select transistor coupled to the first source follower transistor;

a second source follower transistor coupled to the second floating diffusion region; and

a second row select transistor coupled to the second source follower transistor.

12. The image sensor defined in claim 11, wherein the first photodiode, the second photodiode, the first transfer transistor, and the second transfer transistor are formed in a first substrate, wherein the first floating diffusion region, the second floating diffusion region, the first source follower transistor, and the second source follower transistor are formed in a second substrate, wherein the first and second substrates are connected by a metal interconnect layer, wherein the metal interconnect layer comprises a first metal interconnect layer interposed between the first transfer transistor and the first floating diffusion region, and wherein the metal interconnect layer comprises a second metal interconnect layer interposed between the second transfer transistor and the second floating diffusion region.

14. The image sensor defined in claim 9, wherein the third photodiode is configured to obtain time-of-flight information.

15. The image sensor defined in claim 14, wherein the third photodiode is formed below the first and second photodiodes and wherein the first and second photodiodes are configured to obtain phase detection information.

13. (canceled)

16. A method of operating an image sensor, wherein the image sensor comprises a first substrate that includes first and second photodiodes and a second substrate that includes a third photodiode, a first floating diffusion region, and a second floating diffusion region, and wherein a single microlens covers the first, second, and third photodiodes, the method comprising:

using the first and second photodiodes, obtaining phase detection information; and

while obtaining the phase detection information using the first and second photodiodes, obtaining time-of-flight information using the third photodiode.

17. The method defined in claim 16, wherein the image sensor further comprises first and second anti-blooming transistors configured to couple the first and second photodiodes to a bias voltage, a first transfer transistor configured to transfer charge from the first photodiode to the first floating diffusion region, a second transfer transistor configured to transfer charge from the second photodiode to the second floating diffusion region, a third transfer transistor configured to transfer charge from the third photodiode to the first floating diffusion region, a fourth transfer transistor configured to transfer charge from the third photodiode to the second floating diffusion region, a first reset transistor coupled to the first floating diffusion region, and a second reset transistor coupled to the second floating diffusion region, the method further comprising:

before obtaining the phase detection information and before obtaining the time-of-flight information, asserting the first and second anti-blooming transistors;

asserting the first and second reset transistors to reset the first and second floating diffusion regions; and

while asserting the first and second reset transistors, asserting the third and fourth transfer transistors to reset the third photodiode.

18. The method defined in claim 17, further comprising:

after resetting the third photodiode, deasserting the first and second reset transistors to begin an integration time for the third photodiode;

during the integration time for the third photodiode, alternately asserting the third transfer transistor and the fourth transfer transistor; and

at the end of the integration time for the third photodiode, sampling a first voltage level of the first floating diffusion region and a first voltage level of the second floating diffusion region.

19. The method defined in claim 18, further comprising:

during the integration time for the third photodiode, deasserting the first and second anti-blooming transistors to begin an integration time for the first and second photodiodes;

at the end of the integration time for the first and second photodiodes, asserting the first and second transfer transistors;

after asserting the first and second transfer transistors, sampling a second voltage level of the first floating diffusion region and a second voltage level of the second floating diffusion region;

after sampling the first voltage level of the first floating diffusion region and the first voltage level of the second floating diffusion region and before asserting the first and second transfer transistors, asserting the first and second reset transistors; and

after asserting the first and second reset transistors, sampling a reset voltage level of the first floating diffusion region and sampling a reset voltage level of the second floating diffusion region, wherein the reset voltage levels of the first and second floating diffusion regions are subtracted from the first voltage levels of the first and second floating diffusion regions to obtain the time-of-flight information, and wherein the reset voltage levels of the first and second floating diffusion regions are subtracted from the second voltage levels of the first and second floating diffusion regions to obtain the phase detection information.

20. (canceled)