CMOS image sensor array with black pixel using negative-tone resist support layer

• US 7,172,922 B2
• Filed: 08/19/2002
• Issued: 02/06/2007
• Est. Priority Date: 08/19/2002
• Status: Active Grant

• Current Assignee: Alidouble Inc.
• Original Assignee: Tower Semiconductor Limited
• Inventors: Benjamin, Almog, Wolf, Hanan, Shevartzberg, Eyal
• Primary Examiner(s): Kebede, Brook
• Application Number:
  US10/223,914
• Publication Number:
  US 20040032518A1
• Time in Patent Office: 1,632 Days
• Field of Search: 438/48, 438/57, 438/59, 438/60, 438/69, 438/73, 438/75, 257/E31.075, 257/E31.081, 257/E31.084, 257/E27.153, 257/E27.154, 257/E27.159, 257/E27.163
• US Class Current: 438/75
• CPC Class Codes: H01L 27/14623 Optical shielding
• CPC Class Codes: H01L 27/14632 Wafer-level processed structures
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 27/14687 Wafer level processing

Abstract

A “black” pixel for measuring dark current is produced using carbon-based or pigment-based black photosensitive resist deposited on a support layer that is formed using negative-tone photosensitive resist, both being formed over the light sensitive portion of the black pixel. After an array of pixels is fabricated, a negative-tone resist layer is deposited on the upper insulator formed over the pixels, and a region of the negative-tone resist located over the black pixel is exposed using a first mask. A carbon-based resist layer is deposited on the negative-tone resist layer, and a region of the carbon-based resist located over the black pixel is exposed using a second mask. The negative-tone and carbon-based resists are then developed to remove portions of the layers not located over the black pixel.

Claims

1. A method of producing image sensors comprising the steps of:

producing a plurality of pixels on a substrate including a first pixel located adjacent to a second pixel, each of the pixels including a light-sensitive region;

forming a non-carbon-based photosensitive resist support layer over the first and second pixels;

forming a carbon-based photosensitive resist layer on the support layer; and

removing portions of the support layer and the carbon-based photosensitive resist layer that are located over the second pixel such that a first portion of the support layer is positioned over the first pixel, and a second portion of the carbon-based photosensitive resist layer is positioned on the first portion.

2. The method according to claim 1,

wherein forming the support layer comprises depositing a negative-tone photosensitive resist layer over the first and second pixels, and then exposing the first portion of the negative-tone photosensitive resist layer through a first mask,

wherein forming the carbon-based photosensitive resist layer comprises exposing the second portion of the carbon-based photosensitive resist layer through a second mask, and

wherein removing portions of the support layer and the carbon-based photosensitive resist layer comprises developing unexposed portions of the negative-tone photosensitive resist layer and the carbon-based photosensitive resist layer, and then rinsing away the developed portions of the negative-tone photosensitive resist layer and the carbon-based photosensitive resist layer.

3. The method according to claim 2,

wherein exposing the first portion of the negative-tone photosensitive resist layer and exposing the second portion of the carbon-based photosensitive resist layer comprise utilizing a light source having an I-line wavelength or a G-line wavelength.

4. The method according to claim 3,

wherein exposing the first portion of the negative-tone photosensitive resist layer comprises applying an exposure dose of 150–

700 mJ/cm², and

wherein exposing the first portion of the negative-tone photosensitive resist layer comprises applying an exposure dose of 500–

1200 mJ/cm².

5. The method according to claim 2,

wherein depositing a negative-tone photosensitive resist layer comprises depositing a transparent photosensitive resist layer.

6. The method according to claim 1,

wherein forming the support layer comprises depositing a negative-tone photosensitive resist layer over the first and second pixels, and then exposing the first portion of the negative-tone photosensitive resist layer through a mask,

wherein forming the carbon-based photosensitive resist layer comprises exposing the second portion of the carbon-based photosensitive resist layer through the mask, and

wherein removing portions of the support layer and the carbon-based photosensitive resist layer comprises developing unexposed portions of the negative-tone photosensitive resist layer and the carbon-based photosensitive resist layer, and then rinsing away the developed portions of the negative-tone photosensitive resist layer and the carbon-based photosensitive resist layer.

7. The method according to claim 6,

wherein exposing the first portion of the negative-tone photosensitive resist layer and the second portion of the carbon-based photosensitive resist layer comprises utilizing a light source having an I-line wavelength or a G-line wavelength.

8. The method according to claim 7,

wherein exposing the first portion of the negative-tone photosensitive resist layer comprises applying an exposure dose of 150–

700 mJ/cm², and exposing the first portion of the negative-tone photosensitive resist layer comprises applying an exposure dose of 500–

1200 mJ/cm².

9. The method according to claim 7,

wherein depositing a negative-tone photosensitive resist layer comprises depositing a transparent photosensitive resist layer.

10. The method according to claim 1, further comprising forming a color filter layer before the support layer.

11. A method for producing an image sensor comprising:

producing a plurality of pixels on a substrate including a first pixel located adjacent to a second pixel, each of the pixels including a light-sensitive region;

forming a negative-tone photosensitive resist layer over the first and second pixels;

forming a black photosensitive resist layer on the negative-tone photosensitive resist layer; and

removing portions of the negative-tone photosensitive resist layer and the black photosensitive resist layer that are located over the second pixel such that a support portion of the negative-tone photosensitive resist layer is positioned over the first pixel, and a light blocking portion of the black photosensitive resist layer is formed on the support portion.

12. The method according to claim 11,

wherein forming the negative-tone photosensitive resist layer comprises exposing the support portion of the negative-tone photosensitive resist layer through a mask,

wherein forming the black photosensitive resist layer comprises depositing a carbon-based photosensitive resist layer on the negative-tone photosensitive resist layer, and exposing the light blocking portion of the carbon-based photosensitive resist layer through the mask, and

wherein removing portions of the negative-tone photosensitive resist layer and the carbon-based photosensitive resist layer comprises developing unexposed portions of the negative-tone photosensitive resist layer and the carbon-based photosensitive resist layer, and then rinsing away the developed portions of the negative-tone photosensitive resist layer and the carbon-based photosensitive resist layer.

13. The method according to claim 12,

wherein exposing the support portion of the negative-tone photosensitive resist layer and exposing the light blocking portion of the carbon-based photosensitive resist layer comprise utilizing a light source having an I-line wavelength or a G-line wavelength.

14. The method according to claim 13,

wherein exposing the support portion of the negative-tone photosensitive resist layer comprises applying an exposure dose of 150–

700 mJ/cm², and

wherein exposing the light blocking portion of the negative-tone photosensitive resist layer comprises applying an exposure dose of 500–

1200mJ/cm².

15. The method according to claim 12,

wherein depositing a negative-tone photosensitive resist layer comprises depositing a transparent photosensitive resist layer.

16. The method according to claim 11,

wherein forming the negative-tone photosensitive resist layer comprises exposing the support portion of the negative-tone photosensitive resist layer through a mask,

wherein forming the black photosensitive resist layer comprises depositing a pigment-based photosensitive resist layer on the negative-tone photosensitive resist layer, and exposing the light blocking portion of the pigment-based photosensitive resist layer through the mask, and

wherein removing portions of the negative-tone photosensitive resist layer and the pigment-based photosensitive resist layer comprises developing unexposed portions of the negative-tone photosensitive resist layer and the pigment-based photosensitive resist layer, and then rinsing away the developed portions of the negative-tone photosensitive resist layer and the pigment-based photosensitive resist layer.