Image sensor structures for fingerprint sensing

• US 10,147,757 B2
• Filed: 03/31/2016
• Issued: 12/04/2018
• Est. Priority Date: 02/02/2015
• Status: Active Grant

• Current Assignee: Beijing Jiiov Technology Company Limited, Knowroads, LLC
• Original Assignee: Synaptics Incorporated
• Inventors: Lee, Young Seen, Wickboldt, Paul, Smith, Patrick, Gove, Robert John, Goodelle, Jason
• Primary Examiner(s): SANDVIK, BENJAMIN P
• Application Number:
  US15/087,481
• Publication Number:
  US 20160254312A1
• Time in Patent Office: 978 Days
• Field of Search: None
• CPC Class Codes: G02B 27/30 Collimators
• CPC Class Codes: G02B 5/201 in the form of arrays
• CPC Class Codes: G02B 6/08 with fibre bundle in form of plate
• CPC Class Codes: G06V 40/1318 using electro-optical elements or layers, e.g. electroluminescent sensing
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H01L 27/14632 Wafer-level processed 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 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

Abstract

Methods and systems for integrating image sensor structures with collimator filters, including manufacturing methods and associated structures for forming collimator filters at the wafer level for integration with image sensor semiconductor wafers. Methods of making an optical biometric sensor include forming a collimator filter layer on an image sensor wafer, wherein a plurality of light collimating apertures in the collimator filter layer are aligned with a plurality of light sensing elements in the image sensor wafer, and after forming the collimator filter layer on the image sensor wafer, singulating the image sensor wafer into a plurality of individual optical sensors.

Claims

1. A method of making an optical biometric sensor, comprising:

forming a collimator filter layer on an image sensor wafer, wherein a plurality of light collimating apertures in the collimator filter layer are aligned with a plurality of light sensing elements in the image sensor wafer; and

after forming the collimator filter layer on the image sensor wafer, singulating the image sensor wafer into a plurality of individual optical sensors,

wherein the forming the collimator filter layer includes forming the plurality of light collimating apertures and routing circuitry for light sensing elements of the image sensor wafer in one or more redistribution layers disposed on a front side of the image sensor wafer, and

wherein the forming the plurality of light collimating apertures includes coating a light absorbing material on sidewalls of the light collimating apertures in the one or more redistribution layers.

2. A method of making an optical biometric sensor, comprising:

forming a collimator filter layer on an image sensor wafer, wherein a plurality of light collimating apertures in the collimator filter layer are aligned with a plurality of light sensing elements in the image sensor wafer; and

after forming the collimator filter layer on the image sensor wafer, singulating the image sensor wafer into a plurality of individual optical sensors,

wherein the forming the collimator filter layer on the image sensor wafer comprises;

forming a collimator filter wafer having the plurality of light collimating apertures; and

attaching the collimator filter wafer to the image sensor wafer.

3. The method of claim 2, wherein the forming the collimator filter wafer comprises:

providing a wafer substrate having a back side and a polished front side opposite the back side, the wafer substrate having an initial thickness;

forming a patterned mask layer on the polished front side, the patterned mask layer having a plurality of exposure holes exposing the front side of the wafer substrate;

thinning the wafer substrate, from the back side, to a target thickness less than the initial thickness; and

etching the front side of the wafer substrate to form the plurality of light collimating apertures corresponding to the plurality of exposure holes in the patterned mask layer, each of the plurality of light collimating apertures extending entirely through the target thickness of the wafer substrate.

4. The method of claim 3, further including creating fiducial alignment marks on the front side of the wafer substrate during the etching the front side of the wafer substrate or during the forming the patterned mask layer.

5. The method of claim 3, wherein the forming the patterned mask layer includes forming a masking material layer on the polished front side and patterning the masking material layer to form the patterned mask layer having the plurality of exposure holes.

6. The method of claim 2, wherein the forming the collimator filter wafer includes forming a plurality of scribe line pairs, each scribe line pair defining a removal region therebetween in the collimator filter wafer, wherein the image sensor wafer includes a bond pad pair under the removal region of the collimator filter wafer.

7. The method of claim 6, wherein the singulating the image sensor wafer further comprises removing each removal region in the collimator filter wafer between each scribe line pair by half-cut dicing or by etching to thereby expose each bond pad pair in the image sensor wafer.

8. The method of claim 2,

wherein the forming the collimator filter wafer comprises:

attaching a back side of a wafer substrate to a support structure, the wafer substrate having the back side and a front side opposite the back side, the wafer substrate having an initial thickness;

thinning the wafer substrate, from the front side, to a target thickness less than the initial thickness;

forming a patterned mask layer on the front side, the mask layer having a plurality of exposure holes through which the front side is exposed; and

etching the front side to form the plurality of light collimating apertures through the plurality of exposure holes, each of the plurality of light collimating apertures extending entirely through the target thickness of the wafer substrate; and

wherein the attaching the collimator filter wafer to the image sensor wafer includes;

attaching the front side of the etched wafer substrate to the image sensor wafer; and

removing the support structure from the wafer substrate.

9. The method of claim 8, wherein the removing the support structure occurs after the attaching.

10. The method of claim 8, further including dicing the etched wafer before attaching the front side of the etched wafer substrate to the image sensor wafer and before removing the support structure.

11. The method of claim 8, further including dicing the wafer substrate during the etching the front side.

12. A method of making an optical biometric sensor, comprising:

forming a collimator filter layer on an image sensor wafer, wherein a plurality of light collimating apertures in the collimator filter layer are aligned with a plurality of light sensing elements in the image sensor wafer; and

after forming the collimator filter layer on the image sensor wafer, singulating the image sensor wafer into a plurality of individual optical sensors,

wherein the forming the collimator filter layer on the image sensor wafer comprises;

providing a wafer substrate having a back side and a polished front side opposite the back side, the wafer substrate having an initial thickness;

forming a patterned mask layer on the polished front side, the patterned mask layer having a plurality of exposure holes through which the front side is exposed;

etching the front side to form a plurality of vias through the exposure holes, each of the plurality of vias being free of conductive material and extending partially into the wafer substrate to a target depth less than the initial thickness;

attaching the front side of the etched wafer substrate to the image sensor wafer; and

thinning the etched wafer substrate, from the back side, to a target thickness, to expose the plurality of vias, wherein the exposed plurality of vias correspond to the plurality of light collimating apertures.

13. A method of making an optical biometric sensor, comprising:

forming a collimator filter layer on an image sensor wafer, wherein a plurality of light collimating apertures in the collimator filter layer are aligned with a plurality of light sensing elements in the image sensor wafer; and

after forming the collimator filter layer on the image sensor wafer, singulating the image sensor wafer into a plurality of individual optical sensors,

wherein the forming the collimator filter layer comprises forming the plurality of light collimating apertures into a back side of the image sensor wafer, wherein a front side of the image sensor wafer includes one or more redistribution layers.

14. The method of claim 13 wherein the forming the plurality of light collimating apertures includes etching selected portions of the back side of the image sensor wafer.

15. An optical sensor wafer having a plurality of optical sensor devices for biometric sensing, comprising:

an image sensor wafer comprising an array of light sensing devices; and

a collimator filter layer disposed on the image sensor wafer, the collimator filter layer comprising an array of light collimating filter elements, wherein the array of light collimating filter elements is aligned with the array of light sensing devices, wherein the collimator filter layer comprises a plurality of scribe line pairs, each scribe line pair defining a removal region therebetween in the collimator filter wafer, wherein the image sensor wafer includes a bond pad pair under the removal region of the collimator filter wafer for each of the plurality of optical sensor devices.

16. The optical sensor wafer of claim 15, wherein each light collimating filter element includes a plurality of light collimating apertures, and each light sensing device includes a corresponding plurality of light sensing elements.

17. The optical sensor wafer of claim 16,

wherein each light collimating filter element includes a light blocking portion disposed between the plurality of light collimating apertures;

wherein each light sensing device comprises a plurality of optical sensing elements disposed under the corresponding plurality of light collimating apertures and non-sensing circuitry disposed under the corresponding light blocking portion.