# US 2014/0197511 A1 · Methods for forming backside illuminated image sensors with front side metal redistribution layers

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- Number: US 2014/0197511 A1
- Document ID: US20140197511A1
- Status: Published application
- Kind: A1
- Application number: 14/215,975
- Filed: 2014-03-17
- Published: 2014-07-17
- Earliest claimed: 2011-01-31
- Assignees: Aptina Imaging Corporation
- Applicants: Aptina Imaging Corporation
- Inventors: Swarnal Borthakur; Kevin W. Hutto; Andrew Perkins; Marc Sulfridge
- Web page: https://patentgrep.com/patent/US20140197511A1

## CPC

- H10F 39/026: {Wafer-level processing}
- H10F 39/024: {of coatings or optical elements}
- H10F 39/199: {Back-illuminated image sensors}
- H10F 39/8053: {Colour filters}
- H10F 39/811: {Interconnections}
- H10F 77/50: Encapsulations or containers (for photovoltaic modules H10F19/80)
- H10F 39/804: {Containers or encapsulations}
- H10F 77/206: {for devices having potential barriers}
- H10W 72/20: Bump connectors, e.g. solder bumps or copper pillars; Dummy bumps; Thermal bumps
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10

## 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

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 2)

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

### Claim 4 (depends on 3)

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.

### Claim 5 (depends on 4)

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

### Claim 6 (depends on 1)

The image sensor defined in claim 1 further comprising an array of micolenses formed over the array of color filter elements.

### Claim 7 (depends on 1)

The image sensor defined in claim 1 further comprising a light blocking layer formed on the second side of the semiconductor substrate adjacent to the array of color filter elements.

### Claim 8 (depends on 1)

The image sensor defined in claim 1 further comprising a permanent carrier mounted on the semiconductor substrate.

### Claim 9 (depends on 8)

The image sensor defined in claim 8 wherein the patterned metallization layer and the at least one dielectric layer form through-silicon vias in the permanent carrier.

### Claim 10 (depends on 9)

The image sensor defined in claim 9 wherein the through-silicon vias form contacts with the bond pads.

### Claim 11 (depends on 10)

The image sensor defined in claim 10, wherein the at least one dielectric layer forms sidewalls of the through-silicon vias.

### Claim 12

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.

### Claim 13 (depends on 6)

The method defined in claim 6 further comprising:
before forming the through-silicon vias through the permanent carrier, thinning the permanent carrier.

### Claim 14 (depends on 7)

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.

### Claim 15 (depends on 8)

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.

### Claim 16 (depends on 9)

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.

### Claim 17 (depends on 10)

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.

### Claim 18 (depends on 11)

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.

### Claim 19

A system, comprising:
a central processing unit;
memory;
input-output circuitry; and
an imaging device, wherein the imaging device comprises:
a semiconductor substrate comprising an array of photosensitive elements and an array of corresponding color filter elements;
bond pads that contact the semiconductor substrate;
a dielectric layer having openings; and
a patterned metallization layer that has portions in the openings and that contacts the bond pads.

### Claim 20 (depends on 19)

The system defined in claim 19, further comprising:
a patterned film having an opening in which the array of corresponding color filter elements is located; and
a glass layer that is mounted over the array of corresponding color filter elements and that is attached to the patterned film.