Semiconductor-based spiral capacitor

• US 6,661,079 B1
• Filed: 02/20/2002
• Issued: 12/09/2003
• Est. Priority Date: 02/20/2002
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Bikulcius, Simon
• Primary Examiner(s): Nguyen, Cuong
• Application Number:
  US10/078,844
• Time in Patent Office: 657 Days
• Field of Search: 257/530-535, 257/295-310, 438/253-254, 438/957
• US Class Current: 257/532
• CPC Class Codes: H01L 23/5223 Capacitor integral with wiring layers
• CPC Class Codes: H01L 27/0805 Capacitors only
• CPC Class Codes: H01L 28/60 Electrodes
• 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

Abstract

Increased capacitance per unit of area with reduced series resistance and inductance is provided by a semiconductor-based capacitor with a spiral shape. The capacitor utilizes a plurality of patterned metal layers that each have a first trace with a spiral shape and a second trace with a spiral shape. The second trace is formed between the loops of the first trace, and around the first trace.

Claims

1. A capacitor formed on a semiconductor material of a first conductivity type, the capacitor including:

a first layer of isolation material formed on the semiconductor material;

a first metal trace formed on the first layer of isolation material, the first metal trace having a first center point, a first end point, and a spiral shape with loops that extends away from the first center point to the first end point; and

a second metal trace formed on the first layer of isolation material, the second metal trace having a second center point, a second end point, and a spiral shape with loops that extends away from the second center point to the second end point, the second metal trace being formed between the loops of the first metal trace, and around the first metal trace.

2. The capacitor of claim 1 wherein the second metal trace lies adjacent to the first center point.

3. The capacitor of claim 2 wherein the second center point is formed within a first half loop of the first metal trace from the first center point.

4. The capacitor of claim 1 and further comprising:

a second layer of isolation material formed on the layer of isolation material, the first metal trace, and the second metal trace;

a third metal trace formed on the second layer of isolation material, the third metal trace having a third center point, a third end point, and a spiral shape with loops that extends away from the third center point to the third end point; and

a fourth metal trace formed on the second layer of isolation material, the fourth metal trace having a fourth center point, a fourth end point, and a spiral shape that extends away from the fourth center point to the fourth end point, the fourth trace being formed between the loops of the third metal trace, and around the third metal trace.

5. The capacitor of claim 4 wherein the second metal trace lies adjacent to the first center point, and the fourth metal trace lies adjacent to the third center point.

6. The capacitor of claim 5 wherein the fourth center point is formed within a first half loop of the third trace from the fourth center point.

7. The capacitor of claim 4 and further comprising:

a plurality of first vias formed in the second layer of isolation material to make an electrical connection with the first trace and the third trace; and

a plurality of second vias formed in the second layer of isolation material to make an electrical connection with the second trace and the fourth trace.

8. The capacitor of claim 7 wherein the third trace is formed to be vertically over the first trace.

9. The capacitor of claim 8 wherein the fourth trace is formed to be vertically over the second trace.

10. The capacitor of claim 4 wherein the third trace is formed to be vertically over the first trace.

11. The capacitor of claim 10 wherein the fourth trace is formed to be vertically over the second trace.

12. The capacitor of claim 1 and further comprising a well of a second conductivity type formed in the semiconductor material, the first metal trace and the second metal trace being formed over the well.

13. The capacitor of claim 12 and further comprising:

a second layer of isolation material formed on the first layer of isolation material, the first metal trace, and the second metal trace;

a third metal trace formed on the second layer of isolation material, the third metal trace having a third center point, a third end point, and a spiral shape with loops that extends away from the third center point to the third end point; and

a fourth metal trace formed on the second layer of isolation material, the fourth metal trace having a fourth center point, a fourth end point, and a spiral shape that extends away from the fourth center point to the fourth end point, the fourth center point being formed between the loops of the third metal trace, and around the third metal trace.

14. A capacitor formed on a semiconductor material of a first conductivity type, the capacitor including:

a plurality of layers of isolation material formed over the semiconductor material, a first layer of isolation material being formed on the semiconductor material, other than the first layer of isolation material, each layer of isolation material being formed on a preceding layer of isolation material;

a plurality of spaced apart metal layers corresponding to the plurality of layers of isolation material, each metal layer being formed on a corresponding layer of isolation material and having a first metal trace and a second metal trace,

the first metal trace having a first center point, a first end point, and a spiral shape with loops that extends away from the first center point to the first end point; and

the second metal trace having a second center point, a second end point, and a spiral shape that extends away from the second center point to the second end point, the second metal trace being formed between the loops of the first metal trace, and around the first metal trace; and

a plurality of vias formed in the second and greater layers of isolation material, the vias making electrical connections between each vertically adjacent first metal trace, and each vertically adjacent second metal trace.

15. The capacitor of claim 14 wherein the second metal trace lies adjacent to the first center point.

16. The capacitor of claim 14 and further comprising a well of a second conductivity type formed in the semiconductor material, a first metal layer of the plurality of metal layers is formed over the well.

17. The capacitor of claim 14 wherein the first traces in the metal layers are formed vertically over each other.

18. The capacitor of claim 17 wherein the second traces in the metal layers are formed vertically over each other.

19. The capacitor of claim 14 and further comprising:

a plurality of first bridges formed on a top layer of isolation material over loops of a first metal trace of a top layer of capacitor metal;

a plurality of first bridge vias that make an electrical connection with the first bridges and loops of the first metal trace of the top layer of capacitor metal;

a plurality of second bridges formed on the top layer of isolation material over loops of a second metal trace of the top layer of capacitor metal; and

a plurality of second bridge vias that make an electrical connection with the second bridges and loops of the second metal trace of the top layer of capacitor metal.

20. The capacitor of claim 18 wherein

the first traces in the metal layers are formed vertically over each other;

and

the second traces in the metal layers are formed vertically over each other.