SHIELDING FOR INTEGRATED CAPACITORS

• US 20100127347A1
• Filed: 11/21/2008
• Published: 05/27/2010
• Est. Priority Date: 11/21/2008
• Status: Active Grant

• Current Assignee: Xilinx, Inc. (Advanced Micro Devices, Inc.)
• Original Assignee: Xilinx, Inc. (Advanced Micro Devices, Inc.)
• Inventors: Quinn, Patrick J.
• Granted Patent: US 7,994,609 B2
• Time in Patent Office: Days
• US Class Current: 257/532
• CPC Class Codes: H01L 23/5223 Capacitor integral with wiring layers
• CPC Class Codes: H01L 23/5225 Shielding layers formed together with wiring layers
• CPC Class Codes: H01L 27/0805 Capacitors only
• CPC Class Codes: H01L 28/82 with an enlarged surface, e.g. formed by texturisation
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/3011 Impedance

Abstract

A capacitor in an integrated circuit (“IC”) includes a core capacitor portion having first conductive elements electrically connected to and forming a part of a first node of the capacitor formed in a first layer and second conductive elements electrically connected to and forming a part of a second node of the capacitor formed in the first layer. The first and second conductive elements alternate in the first conductive layer. Third conductive elements electrically connected to and forming a part of the first node are formed in a second layer adjacent to the first layer. The capacitor also includes a shield capacitor portion having fourth conductive elements formed in at least first, second, third, and fourth layers. The shield capacitor portion is electrically connected to and forms a part of the second node of the capacitor and surrounds the first and third conductive elements.

Claims

1. A capacitor in an integrated circuit (“

IC”

) comprising;

a core capacitor portion having a first plurality of conductive elements electrically connected to and forming a first part of a first node of the capacitor formed in a first conductive layer of the IC and a second plurality of conductive elements electrically connected to and forming a first part of a second node of the capacitor formed in the first conductive layer, the first plurality of conductive elements alternating with the second plurality of conductive elements in the first conductive layer, and a third plurality of conductive elements electrically connected to and forming a second part of the first node formed in a second conductive layer adjacent to the first conductive layer, at least portions of some of the second plurality of conductive elements overlying and vertically coupling to at least portions of some of the third plurality of conductive elements; and

a shield capacitor portion having a fourth plurality of conductive elements formed in at least the first conductive layer of the IC, the second conductive layer of the IC, a third conductive layer of the IC, and a fourth conductive layer of the IC, the first conductive layer and the second conductive layer each being between the third conductive layer and the fourth conductive layer, the shield capacitor portion being electrically connected to and forming a second part of the second node of the capacitor and surrounding the first plurality of conductive elements and the third plurality of conductive elements.

2. The capacitor of claim 1 wherein the third conductive layer is a metal layer of the IC and the fourth conductive layer is a poly layer of the IC, the shield capacitor portion including a first node shield plate formed in the metal layer from a plurality of metal stripes and a second node shield plate formed in the poly layer.

3. The capacitor of claim 1 wherein the shield capacitor portion includes a first node shield plate formed in the third conductive layer and a second node shield plate formed in the fourth conductive layer and further comprising a first conductive curtain extending from the first node shield plate to the second node shield plate and a second conductive curtain extending from the first node shield plate to the second node shield plate.

4. The capacitor of claim 1 wherein the capacitor is a switching capacitor, the first node is a top node of the switching capacitor and the second node is a bottom node of the switching capacitor.

5. The capacitor of claim 1 further comprising

a reference shield electrically connected to a reference node of the IC, the shield capacitor portion being disposed between the reference shield and the core capacitor portion.

6. The capacitor of claim 5 wherein the reference shield includes a substrate portion of a substrate of the IC, a first conductive curtain extending from the substrate portion, and a second conductive curtain extending from the substrate portion.

7. The capacitor of claim 6 wherein the substrate portion comprises an N-well of the substrate of the IC.

8. The capacitor of claim 6 further comprising a reference shield plate extending from the first conductive curtain to the second conductive curtain in a metal layer of the IC.

9. The capacitor of claim 5 wherein the reference node is a V_DD node.

10. The capacitor of claim 5 wherein the reference node is an analog ground node.

11. The capacitor of claim 1 wherein the first plurality of conductive elements comprises a first plurality of conductive strips extending along a first direction, the second plurality of conductive elements comprises a second plurality of conductive strips extending along the first direction, and the third plurality of conductive elements comprises a third plurality of conductive strips extending along a second direction orthogonal to the first direction.

12. The capacitor of claim 11 wherein each of the conductive elements in the third plurality of conductive elements is adjacent to a conductive element electrically connected to and forming a third part of the first node.

13. The capacitor of claim 12 further comprising a fourth plurality of conductive elements formed in a fifth conductive layer of the IC disposed between the fourth conductive layer and the second conductive layer and electrically connected to and forming a fourth part of the first node, the fourth plurality of conductive elements extending along the first direction, and

a fifth plurality of conductive elements electrically connected to and forming a third part of the second node formed in the fifth conductive layer extending along the first direction alternating with the fourth plurality of conductive elements in the fifth conductive layer.

14. The capacitor of claim 1 wherein the first plurality of conductive elements comprises a first plurality of conductive strips extending along a first direction, the second plurality of conductive elements comprises a second plurality of conductive strips extending along the first direction, and the third plurality of conductive elements comprises a third plurality of conductive strips extending along the first direction.

15. The capacitor of claim 14 further comprising a fourth plurality of conductive strips electrically connected to and forming a third part of the second node extending along the first direction and alternating with the third plurality of conductive strips in the second conductive layer.

16. The capacitor of claim 15 wherein each of the fourth plurality of conductive elements is vertically proximate to a conductive element electrically connected to and forming a third part of the first node.

17. The capacitor of claim 1 wherein the first conductive layer is a metal layer of the IC, the first plurality of conductive elements comprises a first plurality of metal filaments extending along a first direction, and the third plurality of conductive elements comprises a second plurality of metal filaments extending along a second direction orthogonal to the first direction.

18. The capacitor of claim 1 wherein the first conductive layer is a first metal layer and the fourth conductive layer is a second metal layer of the IC above the first metal layer, the shield capacitor portion including a first node shield plate formed in the second metal layer from a plurality of metal stripes having a first width, the first plurality of conductive elements comprising a plurality of metal filaments having a second width less than the first width.

19. A capacitor in an integrated circuit (“

IC”

) comprising;

a first plate formed in a first conductive layer of the IC;

a second plate formed in a substrate of the IC;

a gate dielectric layer disposed between the first plate and the second plate;

a shield plate formed in a second conductive layer of the IC having a perimeter electrically connected the second plate so as to form an electrical shield around the first plate.

20. The capacitor of claim 19 wherein the first conductive layer is a first poly layer, the substrate comprises silicon and second plate is formed in an N-well of the substrate and the shield plate is formed in a second poly layer of the IC.