CMOS imager with selectively silicided gates

• US 7,348,613 B2
• Filed: 03/14/2005
• Issued: 03/25/2008
• Est. Priority Date: 08/16/1999
• Status: Expired due to Fees

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Rhodes, Howard E.
• Primary Examiner(s): QUACH, TUAN N
• Application Number:
  US11/078,709
• Publication Number:
  US 20060022233A1
• Time in Patent Office: 1,107 Days
• Field of Search: 257/292, 257/294, 257/382, 257/E27.131, 257/E27.132
• US Class Current: 257/292
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• 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 27/1462 Coatings
• CPC Class Codes: H01L 27/14623 Optical shielding
• 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

Abstract

The invention also relates to an apparatus and method for selectively providing a silicide coating over the transistor gates of a CMOS imager to improve the speed of the transistor gates. The method further includes an apparatus and method for forming a self aligned photo shield over the CMOS imager.

Claims

1. An imager comprising:

a substrate doped to a first conductivity type;

at least one pixel cell comprising;

a photocollection region within said substrate, wherein said photocollection region is doped to a second conductivity type and comprises a photogate;

at least one transistor gate over said substrate; and

an opaque conductive material over said substrate, said opaque conductive material only partially covering said transistor gate and said photogate; and

a signal processing circuit on said substrate, wherein said circuit is connectable to said at least one pixel cell.

2. The imager according to claim 1, wherein said opaque conductive material is an opaque conductive silicide.

3. The imager according to claim 2, wherein said opaque conductive silicide is one of a tungsten silicide, a titanium silicide, a cobalt silicide, and a molybdenum silicide.

4. The imager according to claim 1, wherein said opaque conductive material is an opaque conductive barrier metal.

5. The imager according to claim 4, wherein said opaque conductive barrier metal is one of TiN/W layer, WNx/W layer, and WNx.

6. The imager according to claim 1, wherein said transistor gate is part of a transistor which is one or more of a reset transistor, a row select transistor, source follower transistor or a transfer transistor.

7. The imager according to claim 6, wherein said transistor gate is part of a transistor which is a reset transistor, said imager further comprising a transfer transistor which includes an opaque conductive material deposited over the gate region of said transfer transistor.

8. The imager according to claim 1, wherein said imager further includes a thin ring of opaque conductive material formed over the outer periphery of said photogate.

9. A processing system comprising:

a processor; and

an imaging device coupled to said processor and including;

a substrate doped to a first conductivity type;

at least one pixel cell comprising;

a photocollection region within said substrate, wherein said photocollection region is doped to a second conductivity type and comprises a photogate;

at least one transistor gate over said substrate; and

an opaque conductive material over said substrate, said opaque conductive material only partially covering said transistor gate and said photogate; and

a signal processing circuit on said substrate, wherein said circuit is connectable to said at least one pixel cell.

10. The system according to claim 9, wherein said opaque conductive material is an opaque conductive silicide.

11. The system according to claim 9, wherein said opaque conductive material is an opaque conductive barrier metal.

12. The system according to claim 9, wherein said transistor gate is part of a transistor which is one or more of a reset transistor, a row select transistor, source follower transistor, amplifier transistor or a transfer transistor.

13. The system according to claim 9, wherein said imager further includes a thin ring of opaque conductive material formed over the outer periphery of said photogate.