Multi-trench region for accumulation of photo-generated charge in a CMOS imager

• US 20040235216A1
• Filed: 06/21/2004
• Published: 11/25/2004
• Est. Priority Date: 08/28/2000
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Micron Technology, Inc.
• Inventors: Rhodes, Howard E.
• Granted Patent: US 7,091,059 B2
• Time in Patent Office: Days
• 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 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

1-105. -105. (Cancelled)

106. 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.

107. The method of claim 106, wherein the photosensor is a photodiode sensor.

108. The method of claim 106, 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.

109. The method of claim 106, wherein the first conductivity type is p-type, and the second conductivity type is n-type.

110. The method of claim 106, wherein the step of forming a plurality of trenches comprises a reactive ion etching process.

111. The method of claim 106, wherein the doping step comprises ion implantation.

112-116. -116. (Cancelled)