METHODS FOR FORMING BACKSIDE ILLUMINATED IMAGE SENSORS WITH FRONT SIDE METAL REDISTRIBUTION LAYERS

• US 20120193741A1
• Filed: 05/20/2011
• Published: 08/02/2012
• Est. Priority Date: 01/31/2011
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Inventors: Borthakur, Swarnal, Hutto, Kevin W., Sulfridge, Marc, Perkins, Andrew
• Granted Patent: US 8,697,473 B2
• Time in Patent Office: Days
• US Class Current: 257/433
• CPC Class Codes: H01L 2224/13 of an individual bump connector
• CPC Class Codes: H01L 27/14618 Containers
• CPC Class Codes: H01L 27/14621 Colour filter arrangements
• CPC Class Codes: H01L 27/14636 Interconnect structures
• CPC Class Codes: H01L 27/1464 Back illuminated imager structures
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements
• CPC Class Codes: H01L 27/14687 Wafer level processing
• CPC Class Codes: H01L 31/0203 Containers; Encapsulations , e.g. encapsulation of photodiodesfor photovoltaic devices H01L31/048; for organic photosensitive devices H10K30/80
• CPC Class Codes: H01L 31/022408 for devices characterised by at least one potential jump barrier or surface barrier
• CPC Class Codes: H01L 31/20 such devices or parts thereof comprising amorphous semiconductor materials

Abstract

Methods for forming backside illuminated (BSI) image sensors having metal redistribution layers (RDL) and solder bumps for high performance connection to external circuitry are provided. In one embodiment, a BSI image sensor with RDL and solder bumps may be formed using a temporary carrier during manufacture that is removed prior to completion of the BSI image sensor. In another embodiment, a BSI image sensor with RDL and solder bumps may be formed using a permanent carrier during manufacture that partially remains in the completed BSI image sensor. A BSI image sensor may be formed before formation of a redistribution layer on the front side of the BSI image sensor. A redistribution layer may, alternatively, be formed on the front side of an image wafer before formation of BSI components such as microlenses and color filters on the back side of the image wafer.

Claims

1. An image sensor configured to capture image light, comprising:

a semiconductor substrate having opposing first and second sides, wherein the first side includes an array of photosensitive elements and associated control circuitry and wherein the second side includes an array of corresponding color filter elements, wherein the image light reaches the photosensitive elements by passing through the color filter elements on the second side;

bond pads on the first side of the semiconductor substrate;

at least one dielectric layer having openings; and

.

a patterned metallization layer that has portions in the openings and portions that form contacts with the bond pads.

2. The image sensor defined in claim 1, wherein the bond pads on the first side of the semiconductor substrate interconnect the patterned metallization layer to the control circuitry on the first side of the semiconductor substrate.

3. The image sensor defined in claim 2 further comprising a glass layer that is mounted over the second side.

4. The image sensor defined in claim 3 further comprising a patterned film having an opening in which the array of color filter elements is located, wherein the glass layer is attached to the patterned film.

5. The image sensor defined in claim 4 further comprising solder balls in contact with the metallization layer in the openings.

6. A method of forming an image sensor comprising:

attaching a permanent carrier and a semiconductor substrate;

forming through-silicon vias through the permanent carrier;

thinning the semiconductor substrate that is attached to the permanent carrier in which the through-silicon vias have been formed, wherein the thinned semiconductor substrate has opposing first and second sides, wherein the permanent carrier is attached to the first side; and

forming an array of photosensitive elements and associated control circuitry on the first side and forming an array of corresponding color filter elements on the second side, wherein image light reaches the photosensitive elements by passing through the color filter elements on the second side.

7. The method defined in claim 6 further comprising:

before forming the through-silicon vias through the permanent carrier, thinning the permanent carrier.

8. The method defined in claim 7, wherein forming the through silicon vias through the permanent carrier comprises:

forming a first dielectric layer on the permanent carrier;

forming at least one opening in the first dielectric layer and the permanent carrier, wherein the at least one opening has sidewalls;

forming a second dielectric layer on the sidewalls of the at least one opening; and

forming a metallization layer in the at least one opening, wherein the metallization layer contacts a conductive bond pad on a bottom surface of the opening, wherein the metallization layer covers the second dielectric layer on the sidewalls of the at least one opening, and wherein the metallization layer covers at least a portion of the first dielectric layer.

9. The method defined in claim 8, wherein forming the through silicon vias through the permanent carrier further comprises:

after forming the metallization layer in the at least one opening, forming a third dielectric layer in the at least one opening, wherein the third dielectric layer covers at least a portion of the metallization layer, wherein the third dielectric layer covers at least a second portion of the first dielectric layer not covered by the metallization layer, and wherein the third dielectric layer has openings.

10. The method defined in claim 9 further comprising:

before thinning the semiconductor substrate that is attached to the permanent carrier in which the through-silicon vias have been formed, attaching a temporary carrier to the third dielectric layer.

11. The method defined in claim 10 further comprising forming solder balls in the openings in the third dielectric layer, wherein the solder balls contact the metallization layer.

12. The method defined in claim 11 further comprising:

applying a dry film adhesive to the second side of the thinned semiconductor substrate on which the color filter elements have been formed;

removing a portion of the dry film adhesive;

attaching a cover layer to a remaining portion of the dry film adhesive; and

detaching the temporary carrier from the third dielectric layer.

13. A method of forming an image sensor comprising:

attaching a permanent carrier and a semiconductor substrate;

thinning the semiconductor substrate that is attached to the permanent carrier, wherein the thinned semiconductor substrate has opposing first and second sides, and wherein the permanent carrier is attached to the first side;

forming an array of photosensitive elements and associated control circuitry on the first side and forming an array of corresponding color filter elements on the second side, wherein image light reaches the photosensitive elements by passing through the color filter elements on the second side; and

forming through-silicon vias through the permanent carrier that has been attached to the semiconductor substrate.

14. The method defined in claim 13 further comprising:

after forming the array of corresponding color filter elements on the second side, forming an array of associated microlenses on the second side.

15. The method defined in claim 14 further comprising:

before forming the through silicon vias through the permanent carrier that has been attached to the semiconductor substrate, attaching a temporary carrier to the second side of the semiconductor substrate; and

thinning the permanent carrier that is attached to the semiconductor substrate.

16. The method defined in claim 15 further comprising:

forming a redistribution layer on the permanent carrier, wherein forming the redistribution layer comprises;

forming at least one dielectric layer on the permanent carrier;

forming openings in the at least one dielectric layer; and

forming a metallization layer over at least a portion of the at least one dielectric layer, wherein the metallization layer has at least a portion in the openings in the at least one dielectric layer.

17. The method defined in claim 16 further comprising:

detaching the temporary carrier from the semiconductor substrate that is attached to the permanent carrier on which the redistribution layer has been formed.

18. The method defined in claim 17 further comprising forming solder balls in the openings in the at least one dielectric layer.

19. The method defined in claim 14 further comprising:

before forming the through silicon vias through the permanent carrier that has been attached to the semiconductor substrate, attaching a cover layer to the second side of the semiconductor substrate; and

thinning the permanent carrier that is attached to the semiconductor substrate.

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

before forming solder balls on the first side, forming a redistribution layer on the permanent carrier, wherein forming the redistribution layer comprises;

forming at least one dielectric layer on the permanent carrier;

forming openings in the at least one dielectric layer; and

forming a metallization layer over at least a portion of the at least one dielectric layer, wherein the metallization layer has at least a portion in the openings in the at least one dielectric layer.

21. The method defined in claim 20 further comprising forming solder balls in the openings in the at least one dielectric layer.