Solid-state image sensor, production method for solid-state image sensor, and camera using solid-state image sensor

• US 7,227,206 B2
• Filed: 05/11/2004
• Issued: 06/05/2007
• Est. Priority Date: 05/15/2003
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Watanabe, Takanori
• Primary Examiner(s): Pert; Evan
• Assistant Examiner(s): MANDALA, VICTOR A
• Application Number:
  US10/842,443
• Publication Number:
  US 20050006676A1
• Time in Patent Office: 1,120 Days
• Field of Search: 257/290, 257/291, 257/292, 257/E27.133, 438/48
• US Class Current: 257/292
• CPC Class Codes: H01L 27/14609 Pixel-elements with integrated switching, control, storage or amplification elements scanning details of imagers (circuitry of solid-state image sensors H04N25/00); circuitry of imagers H04N25/70
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers

Abstract

A solid-state image sensor includes, in each pixel, a p-type well provided on a semiconductor substrate, a photodiode provided in the p-type well, a transfer gate for transferring photocharges accumulated in the photodiode, and an n-type diffusion region for receiving the transferred photocharges. The photodiode includes a first n-type accumulation region, and a second n-type accumulation region having a concentration higher than that of the first accumulation region and provided at a position deeper than the first accumulation region. The first accumulation region extends toward an end of the transfer gate, and the second accumulation region is separate from the transfer gate.

Claims

1. A solid state image sensor comprising in each pixel:

a semiconductor region of a first conductive type provided on a semiconductor substrate;

a photodiode provided in the semiconductor region;

a transfer gate for transferring photocharges accumulated in the photodiode; and

a diffusion region for receiving the transferred photocharges,

wherein the photodiode includes a first accumulation region composed of a semiconductor of a second conductive type and a second accumulation region provided in contact with the first accumulation region, at a position deeper in a depth direction than the first accumulation region, and composed of a semiconductor of the second conductive type, and

wherein the first accumulation region comprises a portion extending toward an end of the transfer gate, and the second accumulation region extends along the first accumulation region, except for the portion extending toward the end of the transfer gate, in a direction transverse to the depth direction,

wherein the semiconductor region serves as a first semiconductor region, and a second semiconductor region of the first conductive type is provided on a front side of the photodiode and in contact with the first accumulation region, and

wherein the following condition is satisfied;

Rp2≦

Xj

where Rp2 represents the mean range of ion implantation for the first accumulation region, and Xj represents the depth of the junction between the first accumulation region and the second semiconductor region.

2. A solid-state image sensor according to claim 1, wherein the following condition is satisfied:

Rp2≦

Xj<

Rp1

where Rp1 represents the mean range of ion implantation for the second accumulation region.

3. A solid state image sensor comprising in each pixel:

a semiconductor region of a first conductive type provided on a semiconductor substrate;

a photodiode provided in the semiconductor region;

a transfer gate for transferring photocharges accumulated in the photodiode; and

a diffusion region for receiving the transferred photocharges,

wherein the photodiode includes a first accumulation region composed of a semiconductor of a second conductive type and a second accumulation region provided in contact with the first accumulation region, at a position deeper in a depth direction than the first accumulation region, and composed of a semiconductor of the second conductive type, and

wherein the first accumulation region comprises a portion extending toward an end of the transfer gate, and the second accumulation region extends along the first accumulation region, except for the portion extending toward the end of the transfer gate, in a direction transverse to the depth direction,

wherein the impurity concentration of the second accumulation region differs from that of the first accumulation region.

4. A solid-state image sensor according to claim 3, wherein the impurity concentration of the second accumulation region is greater than that of the first accumulation region.

5. A solid-state image sensor according to claim 3, wherein the impurity concentration of the second accumulation region is 2 to 10 times that of the first accumulation region.

6. A solid-state image sensor comprising a plurality of pixels, each pixel comprising:

a photoelectric conversion element having a first semiconductor region of a first conductive type arranged in a semiconductor substrate, and a second semiconductor region of a second conductive type for accumulating carriers generated by photoelectric conversion;

a transfer gate for transferring the carriers accumulated in the second semiconductor region; and

a diffusion region for receiving the carriers transferred by said transfer gate,

wherein the second semiconductor region comprises a first accumulation region and a second accumulation region arranged deeper in a depth direction than the first accumulation region, at least a part of the first accumulation region being arranged under said transfer gate, and

wherein the impurity concentration of the second accumulation region is greater than that of the first accumulation region.

7. A camera comprising the solid-state image sensor according to claim 6.