3-D transformer for high-frequency applications

• US 20060176136A1
• Filed: 12/05/2005
• Published: 08/10/2006
• Est. Priority Date: 12/08/2004
• Status: Active Grant

• Current Assignee: Purdue Research Foundation (Purdue University)
• Original Assignee: Purdue Research Foundation (Purdue University)
• Inventors: Katehi, Linda P.B., Jeon, Jong-Hyeok, Mohammadi, Saeed, Weon, Dae-Hee
• Granted Patent: US 7,283,029 B2
• Time in Patent Office: Days
• US Class Current: 336/200
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: H01F 17/0006 Printed inductances printed coils for dynamo-electric machines H02K3/26; printed circuits H05K
• CPC Class Codes: H01F 17/0033 with the coil helically wound around a magnetic core
• CPC Class Codes: H01F 17/02 without magnetic core
• CPC Class Codes: H01F 41/041 Printed circuit coils apparatus or processes for manufacturing printed circuits in general H05K3/00
• CPC Class Codes: H01F 5/00 Coils superconducting coils H01F6/06; fixed inductances of the signal type H01F17/00
• CPC Class Codes: Y10T 29/4902 Electromagnet, transformer or inductor

Abstract

A stressed metal technology may fabricate high-Q, three-dimensional microelectronic inductors and transformers. The fabrication method may allow the production of inductors and transformers on high-resistivity silicon substrate and with metal deposition of Au and Cr that is fully compatible with semiconductor fabrication technologies. The produced inductors and transformers exhibit Q factors>60 at frequencies of 3 to 7 GHz. High efficiency, high-Q transformers with coupling factors 0.6<k<0.9 may be created with very high self-resonance frequencies

Claims

1. A method of fabricating a three-dimensional microelectronic inductive device comprising:

providing a pre-processed semiconductor substrate;

depositing a photo-resist sacrificial layer on top of the semiconductor substrate;

depositing a bi-metal layer on top of the sacrificial layer;

patterning the metal layers by depositing a photo-resist mask layer on top of the bi-metal layer to define areas for removal of certain areas of the layer of the bi-metal layer to form a number of finger-shaped extensions;

releasing the certain areas of the bi-metal layer from the sacrificial layer and the substrate in order to allow the areas to bend upward from the semiconductor substrate; and

joining the end part of the finger-shaped extensions of the certain areas of the bi-metal layer with neighboring end part of the finger-shaped extensions of the certain areas of the bi-metal layer to form a three-dimensional structure.

2. A method according to claim 1 further comprising:

applying an etch process to remove the mask layer and the sacrificial layer, and the certain areas of the bi-metal layer; and

applying a metal etch process to remove the certain areas of the bi-metal layer.

3. A method according to claim 2 further comprising applying an electroplating process to the three-dimensional structure to improve the conductivity and stiffness of the structure.

4. A method according to claim 1 where the semiconductor substrate comprises silicon.

5. A method according to claim 1 where the substrate comprises a layered structure of a high resisitivity silicon base layer, a silicon dioxide layer on the base layer, a high dielectric constant dielectric material layer on the silicon dioxide layer, and a silicon dioxide layer on the dielectric material layer.

6. A method according to claim 1 where the three-dimensional structure comprises an inductor or transformer.

7. A method according to claim 1 where the metal layers comprise chromium and gold.

8. A method according to claim 1 where the three-dimensional structures are substantially circular shaped in cross-section.

9. A method according to claim 1 where the three-dimensional structures are substantially oval shaped in cross-section.

10. A method according to claim 1 where the depositing of the bi-metal layer is performed by an e-beam evaporation process.

19. A three-dimensional microelectronic inductive device as in claim 10 where the inductive device comprises a transformer with a primary coil, a secondary coil, and interconnects leading from the primary coil and the secondary coil.

11. A three-dimensional microelectronic inductive device for use in integrated circuit applications comprising:

a semiconductor substrate having a planar surface;

metal line interconnects running along the surface of the semiconductor substrate;

metal fingers each separated by a gap from each other formed on the substrate and connected to the metal line interconnects; and

where the fingers meeting neighboring fingers above the semiconductor substrate to form a coil-shaped device with a diameter and a central axis of the coil substantially parallel to a plane formed by the surface of the substrate.

12. A three-dimensional microelectronic inductive device as in claim 11 where the metal fingers comprise chromium and gold.

13. A three-dimensional microelectronic inductive device as in claim 11 where the coil-shaped device has a substantially circular cross-section.

14. A three-dimensional microelectronic inductive device as in claim 11 where the coil-shaped device has a substantially oval-shaped cross-section.

15. A three-dimensional microelectronic inductive device as in claim 11 where the number of metal fingers is greater than 1.

16. A three-dimensional microelectronic inductive device as in claim 11 where the substrate comprises silicon.

17. A three-dimensional microelectronic inductive device as in claim 11 where the substrate comprises a layered structure of a high resisitivity silicon base layer, a silicon dioxide layer on the base layer, a high dielectric constant dielectric material layer on the silicon dioxide layer, and a silicon dioxide layer on the dielectric material layer.

18. A three-dimensional microelectronic inductive device as in claim 11 where the inductive device comprises an inductor with a number of turns comprising the inductor.

20. A three-dimensional microelectronic inductive device as in claim 11 where the transformer is a 3:

4 ratio transformer, where the primary coil has 4 turns and the secondary coil has 3 turns or vice versa.