On-chip power inductor

• US 7,875,955 B1
• Filed: 03/05/2007
• Issued: 01/25/2011
• Est. Priority Date: 03/09/2006
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Lindorfer, Philipp, Johnson, Peter, Hopper, Peter J., Hwang, Kyuwoon
• Primary Examiner(s): Shingleton; Michael B
• Application Number:
  US11/713,921
• Time in Patent Office: 1,422 Days
• Field of Search: 257/531, 257/528, 257/516, 330/307, 336/200
• US Class Current: 257/531
• CPC Class Codes: H01F 17/0006 Printed inductances printed coils for dynamo-electric machines H02K3/26; printed circuits H05K
• CPC Class Codes: H01F 17/02 without magnetic core
• CPC Class Codes: H01L 23/5227 Inductive arrangements or effects of, or between, wiring layers other inductive arrangements H01L23/645
• 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

An on-chip inductor structure for a DC-DC power regulator circuit merges the switching transistor metallization with the inductor. Thick top level conductor metal that is used to strap the transistor array and to lower its on-state resistance is also used to extend the power inductor into the transistor array. Thus, the structure includes three basic components: a power inductor that spirals around the transistor array, the transistor array itself, and the transistor array metallization that is used to form a distributed inductance situated over the transistor array.

Claims

1. A power inductor structure that is formed on a semiconductor substrate as part of a semiconductor integrated circuit, the power inductor structure comprising:

a switching node;

at least one MOS transistor connected to the switching node;

a spiral power inductor connected to the switching node, the spiral power inductor including

(i) a conductive coil;

(ii) a bottom metal magnetic member formed over an upper surface of the semiconductor substrate, the bottom metal magnetic member including a plurality of spaced-apart bottom member segments, each bottom member segment having a first edge that is parallel to and spaced-apart from an edge of a first adjacent bottom member segment and a second edge that is parallel to the first edge and parallel to and spaced-apart from an edge of a second adjacent bottom member segment, the first and second edges being perpendicular to the direction of current flow through the conductive coil;

(iii) a top metal magnetic member formed over the bottom metal magnetic member, the top metal magnetic member including a plurality of spaced-apart top member segments, each top member segment having a first edge that is parallel to and spaced-apart from an edge of a first adjacent top member segment and a second edge that is parallel to the first edge and parallel to and spaced-apart from an edge of a second adjacent top member segment, the first and second edges being perpendicular to the direction of current flow through the conductive coil, the bottom metal magnetic member and the top metal magnetic member defining an inductor coil region therebetween, the conductive coil being disposed in the inductor coil region to be spaced-apart from the bottom metal magnetic member and the top metal magnetic member.

2. The power inductor structure of claim 1, wherein the top metal magnetic member and the bottom metal magnetic member surround the conductive coil and are separated from each other.

3. The power inductor structure of claim 1, wherein the at least one MOS transistor consists of a single MOS switching transistor connected between a positive power supply and the switching node.

4. The power inductor structure of claim 1, wherein the at least one MOS transistor comprises a first MOS switching transistor connected between a positive power supply and the switching node and a second MOS switching transistor connected between a negative power supply and the switching node.

5. The power inductor structure of claim 1, wherein both the bottom metal magnetic member and the top metal magnetic member comprise Permalloy.

6. The power inductor structure of claim 1, wherein both the bottom metal magnetic member and the top metal magnetic member comprise Permalloy having a Ni:

Fe ratio of about 20;

80 to 80;

20.

7. The power inductor structure of claim 6, wherein both the top and bottom metal magnetic members are about 0.5-1000 microns thick.

8. The power inductor structure as of claim 7, wherein the conductive coil comprises copper about 0.5-1000 microns thick.