Photodiode sensor and photosensor for use in an imaging device

• US 7,279,766 B2
• Filed: 12/02/2004
• Issued: 10/09/2007
• 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): RICHARDS, NORMAN DREW
• Application Number:
  US11/001,293
• Publication Number:
  US 20050093038A1
• Time in Patent Office: 1,041 Days
• Field of Search: 257/443, 257/461
• US Class Current: 257/461
• 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 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 photodiode sensor for use in an imaging device, said photodiode sensor comprising:

a doped layer of a first conductivity type formed in a substrate;

a plurality of trenches formed in said doped layer, each of said plurality of trenches having a plurality of sidewalls and a bottom, each of said plurality of trenches having a depth within the range of approximately 0.05 to 10 μ

m; and

a doped region of a second conductivity type formed at the sidewalls and bottom of each of said plurality of trenches, said doped layer, plurality of trenches and doped region forming said photodiode sensor.

2. The photodiode sensor of claim 1, wherein the first conductivity type is p-type and the second conductivity type is n-type.

3. The photodiode sensor of claim 1, wherein the doped region is formed by multiple angled ion implantations.

4. The photodiode sensor of claim 3, wherein the multiple angled ion implantations are four orthogonal angled implants at a dose of 1×

10¹² to 1×

10¹⁶ ions/cm² through a patterned resist, and wherein the angle of implantation for each angled implant is greater than θ

c, where tan θ

c=[(t+d)/(w)], where t is the thickness of the resist, d is the depth of said plurality of trenches, and w is the width of said plurality of trenches.

5. The photodiode sensor of claim 4, wherein the dose of each implant is 1×

10¹³ to 1×

10¹⁵ ions/cm².

6. The photodiode sensor of claim 4, wherein the dose of each implant is 5×

10¹³ ions/cm².

7. The photodiode sensor of claim 1, wherein said plurality of trenches comprises two trenches.

8. An imaging device comprising:

a photosensor comprising;

a doped layer of a first conductivity type formed in a substrate;

a plurality of trenches formed in said doped layer, each of said plurality of trenches having a plurality of sidewalls and a bottom; and

a doped region of a second conductivity type formed at the sidewalls and bottom of each of said plurality of trenches, said doped layer. plurality of trenches and doped region forming said photosensor; and

an insulating layer formed over the sidewalls and bottom of each of said plurality of trenches.