3-D transformer for high-frequency applications

• US 7,283,029 B2
• Filed: 12/05/2005
• Issued: 10/16/2007
• Est. Priority Date: 12/08/2004
• Status: Expired due to Fees

• Current Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Original Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Inventors: Jeon, Jong-Hyeok, Mohammadi, Saeed, Katehi, Linda P. B., Weon, Dae-Hee
• Primary Examiner(s): MAI, ANH T
• Application Number:
  US11/294,721
• Publication Number:
  US 20060176136A1
• Time in Patent Office: 680 Days
• Field of Search: 336/200, 336/223, 336/232, 296/021
• 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 high-Q, three-dimensional microelectronic transformer with a primary coil and a secondary coil comprising:

providing a pre-processed semiconductor substrate;

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

depositing a layer of metal alloy on top of the sacrificial layer;

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

releasing the certain areas of metal alloy 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 metal alloy layers with neighboring end part of the finger-shaped extensions of the certain areas of metal alloy layers to form a three-dimensional structure as a microelectronic transformer with a primary coil and a secondary coil.

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 metal alloy layer; and

applying a metal etch process to remove the certain areas of metal alloy 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 metal layers comprise chromium and gold.

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

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

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

10. A high-Q, 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;

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, and

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 high-Q, three-dimensional microelectronic inductive device as in claim 10 where the metal fingers comprise chromium and gold.

12. A high-Q, three-dimensional microelectronic inductive device as in claim 10 where the coil-shaped device has a substantially circular cross-section.

13. A high-Q, three-dimensional microelectronic inductive device as in claim 10 where the coil-shaped device has a substantially oval-shaped cross-section.

14. A high-Q, three-dimensional microelectronic inductive device as in claim 10 where the number of metal fingers is greater than 1.

15. A high-Q, three-dimensional microelectronic inductive device as in claim 10 where the substrate comprises silicon.

16. A high-Q, three-dimensional microelectronic inductive device as in claim 10 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.

17. A high-Q, three-dimensional microelectronic inductive device as in claim 10 where the inductive device comprises an inductor with a number of turns comprising the inductor.

18. A high-Q, three-dimensional microelectronic inductive device as in claim 10 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.