Method of forming a photosensor comprising a plurality of trenches

• US 7,091,059 B2
• Filed: 06/21/2004
• Issued: 08/15/2006
• Est. Priority Date: 08/28/2000
• Status: Expired due to Term

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Micron Technology, Inc.
• Inventors: Rhodes, Howard E.
• Primary Examiner(s): Wilczewski, Mary
• Assistant Examiner(s): BARNES, SETH W
• Application Number:
  US10/871,018
• Publication Number:
  US 20040235216A1
• Time in Patent Office: 785 Days
• Field of Search: 438/48, 438/57, 438/59, 438/60, 438/73, 438/75, 438/80, 438390-392, 438/510, 438/514, 438/523
• US Class Current: 438/60
• CPC Class Codes: H01L 27/14601 Structural or functional details thereof
• CPC Class Codes: H01L 27/1463 Pixel isolation structures
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 27/14687 Wafer level processing
• CPC Class Codes: H01L 27/14689 MOS based technologies
• CPC Class Codes: H01L 31/035281 Shape of the body
• CPC Class Codes: H01L 31/03529 Shape of the potential jump barrier or surface barrier
• CPC Class Codes: H01L 31/103 the potential barrier being of the PN homojunction type
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

A method of forming a multiple-trench photosensor for use in a CMOS imager having an improved charge capacity. The multi-trench photosensor may be either a photogate or photodiode structure. The multi-trench photosensor provides the photosensitive element with an increased surface area compared to a flat photosensor occupying a comparable area on a substrate. The multi-trench photosensor also exhibits a higher charge capacity, improved dynamic range, and a better signal-to-noise ratio. Also disclosed are processes for forming the multi-trench photosensor.

Claims

1. A method of forming a photosensor, comprising the steps of:

providing a semiconductor substrate having a doped layer of a first conductivity type;

forming a doped region of a second conductivity type in the doped layer;

forming a plurality of trenches in said doped region so that the sides and bottom of each of said plurality of trenches are of the second conductivity type; and

forming an insulating layer on the sides and bottom of each of said plurality of trenches of the photosensor.

2. The method of claim 1, wherein the photosensor is a photodiode sensor.

3. The method of claim 1, further comprising forming a conductive layer on the sides and bottom of each of said plurality of trenches, and wherein the photosensor is a photogate sensor.

4. The method of claim 1, wherein the first conductivity type is p-type, and the second conductivity type is n-type.

5. The method of claim 1, wherein the step of forming a plurality of trenches comprises a reactive ion etching process.

6. The method of claim 1, wherein the of forming a doped region comprises ion implantation.

7. A method of forming a photosensor comprising:

forming a doped layer in a semiconductor substrate;

forming a plurality of trenches in said doped layer to define a photosensistive area of the photosensor, wherein each of said plurality of trenches further comprises a plurality of sidewalls and a bottom;

forming a doped region on the sidewalls and bottom of each of said plurality of trenches, wherein said doped region is opposite in conductivity type from said doped layer; and

forming an insulating layer on the sidewalls and bottom of each of said plurality of trenches.

8. The method of claim 7, further comprising forming a conductive layer over said insulating layer.

9. The method of claim 7, wherein said photosensor is a photodiode sensor.

10. The method of claim 7, wherein said photosensor is a photogate sensor.

11. A method of forming a single photosensor comprising:

providing a semiconductor substrate;

forming a doped region in said semiconductor substrate;

forming a photosensitive area comprising at least two trenches in said doped region, wherein each of said at least two trenches further comprises sidewalls and a bottom;

forming a dielectric layer over said sidewalls and bottom of each of said at least two trenches of the single photosensor.

12. The method of claim 11, further comprising forming a conductive layer over said dielectric layer.

13. The method of claim 11, wherein said single photosensor is a photodiode sensor.

14. The method of claim 11, wherein said single photosensor is a photogate sensor.