THIN FILM STRUCTURES WITH NEGATIVE INDUCTANCE AND METHODS FOR FABRICATING INDUCTORS COMPRISING THE SAME

• US 20090261936A1
• Filed: 04/21/2009
• Published: 10/22/2009
• Est. Priority Date: 04/21/2008
• Status: Active Grant

• Current Assignee: University of Dayton
• Original Assignee: University of Dayton
• Inventors: Sarangan, Andrew, Widjaja, Agus
• Granted Patent: US 7,956,715 B2
• Time in Patent Office: Days
• US Class Current: 336/200
• CPC Class Codes: H01F 17/0006 Printed inductances printed coils for dynamo-electric machines H02K3/26; printed circuits H05K
• CPC Class Codes: H01F 2017/0086 on semiconductor substrate

Abstract

An inductor structure comprising a substrate and a planar conductor structure on a surface of the substrate, and methods for fabricating an inductor structure. The planar conductor structure may comprise a vertical stack of three or more multilayer films. Each multilayer film may comprise a first layer of a first metal, defining a first vertical thickness, and a second layer of a second metal, defining a second vertical thickness. The metals and thicknesses are chosen such that the inductor exhibits a negative electrical self-inductance when an electrical signal is transmitted from a first contact point to a second contact point.

Claims

1. An inductor comprising a substrate and a planar conductor structure on a surface of the substrate, the planar conductor structure defining a total thickness and comprising

a vertical stack of three or more multilayer films, each multilayer film comprising

a first layer of a first metal, the first layer defining a first vertical thickness, the first metal defining a first composition, the first composition being substantially the same in all multilayer films of the vertical stack;

and

a second layer of a second metal, the second layer covering the first layer and defining a second vertical thickness, the second metal defining a second composition not equal to the first composition, the second composition being substantially the same in all multilayer films of the vertical stack, the ratio of the first vertical thickness to the second vertical thickness being substantially the same in all multilayer films of the vertical stack;

a first contact point; and

a second contact point, wherein the number of multilayers, the first composition, the first vertical thickness, the second composition, and the second vertical thickness all are chosen such that the inductor exhibits a negative electrical self-inductance when an electric signal is transmitted from the first contact point to the second contact point.

2. The inductor of claim 1, wherein the electric signal comprises an alternating electric current with a frequency of up to 10 GHz.

3. The inductor of claim 2, wherein the alternating current has a frequency of up to 10 MHz.

4. The inductor of claim 1, wherein the planar conductor structure is a series of successive spirals defining a number of turns, a track width, a spacing, an inner radius, and a shape, the shape being selected from the group consisting of a triangle, a square, a rectangle, a higher-order polygon, an ellipse, and a circle.

5. The inductor of claim 4, wherein the number of turns is 1 to 20, the track width is 0.1 μ

m to 200 μ

m, the spacing is 0.1 μ

m to 200 μ

m, and the inner radius is 0.2 μ

m to 400 μ

m.

6. The inductor of claim 1, wherein the first vertical thickness is substantially the same in all multilayer films of the vertical stack.

7. The inductor of claim 6, wherein the planar conductor structure comprises at least ten multilayer films and the total thickness is 0.1 μ

m to 5 μ

m.

8. The inductor of claim 7, wherein the planar conductor structure comprises at least thirty multilayer films.

9. The inductor of claim 1, wherein the first metal is aluminum and the second metal is copper.

10. The inductor of claim 9, wherein the planar conductor structure comprises at least ten multilayer films, the total thickness is 0.1 μ

m to 5 μ

m, and the ratio of the first vertical thickness to the second vertical thickness is about 2.

11. The inductor of claim 1, wherein the first metal is aluminum and the second metal is silver.

12. The inductor of claim 9, wherein the total thickness is 0.1 μ

m to 5 μ

m, and the ratio of the first vertical thickness to the second vertical thickness is about 2.

13. The inductor of claim 1, wherein each multilayer film further comprises a third layer of a third metal, the third layer covering the second layer and defining a third vertical thickness, the third metal defining a third composition not equal to either one of the first composition or the second composition, the third composition being substantially the same in all multilayer films of the vertical stack, the ratio of the second vertical thickness to the third vertical thickness being substantially the same in all multilayer films of the vertical stack, wherein the first composition, the first vertical thickness, the second composition, the second vertical thickness, the third composition, and the third vertical thickness all are chosen such that the inductor exhibits a negative electrical self-inductance when an electric signal is transmitted from the first contact to the second contact.

14. The inductor of claim 13, wherein the first metal is aluminum, the second metal is copper, and the third metal is nickel.

15. The inductor of claim 14, wherein the total thickness is about 1 μ

m, the planar conductor structure comprises at least ten multilayer films, the ratio of the first thickness to the second thickness is about 1, and the ratio of the second thickness to the third thickness is about 0.24.

20. A microelectronic device comprising at least one inductor according to claim 1.

16. A method for fabricating an inductor, the method comprising:

(a) providing a substrate;

(b) providing an insulating layer on a top surface of the substrate;

(c) depositing a lift-off resist on the insulating layer;

(d) soft-baking the substrate, the insulating layer, and the lift-off resist;

(e) coating a photoresist onto the lift-off resist;

(f) soft-baking the substrate, the insulating layer, the lift-off resist, and the photoresist;

(g) exposing the photoresist to ultraviolet light through an inductor pattern;

(h) developing the photoresist and the lift-off resist;

(i) forming a first multilayer film by depositing a first layer of a first metal until the first layer defines a first predetermined thickness, and depositing on the first layer a second layer of second metal until the second layer defines a second predetermined thickness, the second metal having a composition different from that of the first metal, and the metals and thicknesses being chosen such that the inductor will exhibit negative electrical self-inductance when an electric signal is transmitted through the inductor;

(j) forming two or more additional multilayer films on the first multilayer film or on the most recently-formed additional multilayer film by repeating step (i) N times (N≧

2) with the same metals used in the first multilayer film to result in a vertical stack of N+1 multilayer films; and

(k) removing any remaining photoresist and lift-off resist.

17. The method of claim 16, wherein the layers of metal are deposited by sputtering.

18. The method of claim 17, wherein the first metal is aluminum, the second metal is copper, and step (i) is repeated at least 9 times to form a vertical stack of 10 multilayers.

19. The method of claim 16, wherein step (i) further comprises sputtering on the second layer a third layer of a third metal until the third layer defines a third predetermined thickness, the third metal having a composition different from those of the first metal and the second metal.