IMAGING SYSTEMS WITH STACKED IMAGE SENSORS

• US 20150054962A1
• Filed: 08/15/2014
• Published: 02/26/2015
• Est. Priority Date: 08/23/2013
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Inventors: Borthakur, Swarnal, Boettiger, Ulrich, Velichko, Sergey
• Granted Patent: US 9,749,553 B2
• Time in Patent Office: Days
• US Class Current: 348/164
• CPC Class Codes: H01L 2224/32225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 27/14621 Colour filter arrangements
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14629 Reflectors
• CPC Class Codes: H01L 27/14634 Assemblies, i.e. Hybrid structures
• CPC Class Codes: H01L 27/14636 Interconnect structures
• CPC Class Codes: H01L 27/14647 Multicolour imagers having a stacked pixel-element structure, e.g. npn, npnpn or MQW elements
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths

Abstract

An imaging system may include a first image sensor die stacked on top of a second image sensor die. A pixel array may include first pixels having photodiodes in the first image sensor die and second pixels having photodiodes in the second image sensor die. The first pixels may be optimized to detect a first type of electromagnetic radiation (e.g., visible light), whereas the second pixels may be optimized to detect a second type of electromagnetic radiation (e.g., infrared light). Light guide channels may be formed in the first image sensor die to help guide incident light to the photodiodes in the second image sensor substrate. The first and second image sensor dies may be bonded at a wafer level. A first image sensor wafer may be a backside illumination image sensor wafer and a second image sensor wafer may be a front or backside illumination image sensor wafer.

Claims

1. An imaging system, comprising:

a first image sensor having a first plurality of photodiodes; and

a second image sensor having a second plurality of photodiodes, wherein the first image sensor is stacked on top of and bonded to the second image sensor.

2. The imaging system defined in claim 1 wherein the first image sensor is a backside illumination image sensor.

3. The imaging system defined in claim 2 wherein the second image sensor is a front side illumination image sensor and wherein the second image sensor comprises a graded epitaxial substrate.

4. The imaging system defined in claim 2 wherein the second image sensor is a backside illumination image sensor.

5. The imaging system defined in claim 1 wherein the first plurality of photodiodes are formed in a first semiconductor layer, wherein the second plurality of photodiodes are formed in a second semiconductor layer, and wherein the imaging system further comprises:

a microlens array formed over the first and second pluralities of photodiodes.

6. The imaging system defined in claim 5 further comprising a plurality of light guides in the first semiconductor layer, wherein the plurality of light guides are interposed between the microlens array and the second plurality of photodiodes, and wherein each of the light guides transmits light from a respective microlens in the microlens array to an associated photodiode in the second plurality of photodiodes.

7. The imaging system defined in claim 5 further comprising an array of filter elements interposed between the microlens array and the first semiconductor layer.

8. The imaging system defined in claim 7 wherein the array of filter elements comprises color filter elements formed over at least some of the first plurality of photodiodes and infrared filter elements formed over the second plurality of photodiodes, wherein the color filter elements transmit visible light, and wherein the infrared filter elements transmit infrared light.

9. The imaging system defined in claim 8 wherein the first image sensor comprises visible imaging pixels, wherein each of the visible imaging pixels includes one of the photodiodes in the first plurality of photodiodes, wherein the second image sensor comprises infrared imaging pixels, and wherein each of the infrared imaging pixels includes one of the photodiodes in the second plurality of photodiodes.

10. The imaging system defined in claim 9 wherein the photodiodes of the visible imaging pixels each have a first size, wherein the photodiodes of the infrared imaging pixels each have a second size, and wherein the second size is larger than the first size.

11. The imaging system defined in claim 8 wherein the first image sensor comprises visible imaging pixels and upper infrared imaging pixels, wherein each of the visible imaging pixels and the upper infrared imaging pixels includes one of the photodiodes in the first plurality of photodiodes, wherein the second image sensor comprises lower infrared imaging pixels, wherein each of the lower infrared imaging pixels includes one of the photodiodes in the second plurality of photodiodes, and wherein the upper infrared imaging pixels directly overlap the lower infrared imaging pixels.

12. The imaging system defined in claim 11 wherein the upper infrared imaging pixels include respective wide band infrared filters and wherein the lower infrared imaging pixels include respective narrow band infrared filters.

13. The imaging system defined in claim 7 wherein the first image sensor comprises first imaging pixels and second imaging pixels, wherein each of the first and second imaging pixels includes one of the photodiodes in the first plurality of photodiodes, wherein the second image sensor comprises third imaging pixels, wherein each of the third imaging pixels includes one of the photodiodes in the second plurality of photodiodes, wherein the second imaging pixels directly overlap the third imaging pixels, wherein the second imaging pixels include respective color filters, and wherein the third imaging pixels include respective infrared filters.

14. The imaging system defined in claim 1 further comprising:

a conductive via electrically coupled between the first image sensor and the second image sensor.

15. An imaging system, comprising:

a first image sensor wafer having a plurality of first image sensors; and

a second image sensor wafer having a plurality of second image sensors, wherein the first image sensor wafer is stacked on top of and bonded to the second image sensor wafer and wherein each of the first image sensors is aligned with and electrically coupled to an associated one of the second image sensors.

16. The imaging system defined in claim 15 wherein the first image sensors detect visible light and the second image sensors detect infrared light.

17. The imaging system defined in claim 15 wherein the first image sensors are backside illumination image sensors.

18. The imaging system defined in claim 15 wherein the first image sensor wafer comprises first photodiodes formed in a first silicon substrate, wherein the second image sensor wafer comprises second photodiodes formed in a second silicon substrate, and wherein the first photodiodes directly overlap the second photodiodes.

19. The imaging system defined in claim 15 wherein the first image sensor wafer comprises first photodiodes formed in a first silicon substrate, wherein the second image sensor wafer comprises second photodiodes formed in a second silicon substrate, and wherein the second photodiodes are larger than the first photodiodes.

20. An imaging system, comprising:

a pixel array having infrared imaging pixels and visible imaging pixels, wherein the visible imaging pixels each include a photodiode formed in a first semiconductor substrate, wherein the infrared imaging pixels each include a photodiode formed in a second semiconductor substrate, and wherein the first semiconductor substrate overlaps and is mounted to the second semiconductor substrate.

21. The imaging system defined in claim 20 wherein the infrared imaging pixels comprise infrared filter elements that block visible light and wherein the visible imaging pixels comprise color filter elements that pass visible light.

22. The imaging system defined in claim 20 wherein at least some of the infrared imaging pixels are interspersed among the visible imaging pixels.

23. The imaging system defined in claim 20 further comprising:

isolation structures in the first semiconductor substrate, wherein each of the isolation structures is interposed between one of the infrared imaging pixels and one of the visible imaging pixels.

24. The imaging system defined in claim 20 further comprising:

oxide isolation structures in the first semiconductor substrate, wherein each of the oxide isolation structures separates a group of the infrared imaging pixels from a group of the visible imaging pixels.

25. The imaging system defined in claim 20 further comprising:

a plurality of reflectors in the first semiconductor substrate, wherein each of the reflectors is located under a respective one of the visible pixels.

26. The imaging system defined in claim 25 wherein the visible imaging pixels include red, green, and blue imaging pixels and wherein the reflectors are located only under the red and green imaging pixels.

27. The imaging system defined in claim 26 wherein the blue imaging pixels directly overlap the infrared imaging pixels.