Semiconductor transformers

• US 8,049,301 B2
• Filed: 09/21/2007
• Issued: 11/01/2011
• Est. Priority Date: 09/21/2006
• Status: Active Grant

• Current Assignee: City University of Hong Kong
• Original Assignee: City University of Hong Kong
• Inventors: Hui, Shu Yuen Ron
• Primary Examiner(s): Pham; Long
• Application Number:
  US12/441,777
• Publication Number:
  US 20100078761A1
• Time in Patent Office: 1,502 Days
• Field of Search: 257/531, 257/528, 361/35
• US Class Current: 257/531
• CPC Class Codes: H01F 19/00 Fixed transformers or mutual inductances of the signal type H01F36/00 takes precedence
• CPC Class Codes: H01F 2017/0086 on semiconductor substrate inductors for integrated circuits H01L28/10
• CPC Class Codes: H01F 2027/2819 Planar transformers with printed windings, e.g. surrounded by two cores and to be mounted on printed circuit
• CPC Class Codes: H01F 27/2804 Printed windings
• CPC Class Codes: H01L 27/0688 Integrated circuits having a three-dimensional layout

Abstract

A planar transformer structure, which can be constructed in an integrated semiconductor circuit without using traditional metallic windings. To avoid large thermal expansion of metallic spiral windings and associated mechanical stress on a metal-semiconductor interface, it is suggested that highly doped semiconductor materials with or without silicides and salicides can be used to form windings or conducting paths because their thermal expansion coefficients are similar to that of semiconductor material. The planar semiconductor transformer may find application for low-power and signal transfer that needs electrical isolation.

Claims

1. A transformer wherein the primary and secondary windings comprise highly doped conducting paths of a semiconductor material.

2. A transformer as claimed in claim 1 wherein the primary and secondary windings include silicides.

3. A transformer as claimed in claim 1 wherein the primary and secondary windings include salicides.

4. A transformer as claimed in claim 1 wherein the primary and secondary windings are formed as highly doped conducting paths on opposed sides of an insulating substrate.

5. A transformer as claimed in claim 4 wherein the insulating substrate is silicon dioxide and the conducting paths are highly doped silicon.

6. A transformer as claimed in claim 1 wherein the primary winding is formed in a silicon-on-insulator layer.

7. A transformer as claimed in claim 1 wherein the secondary winding is formed in a silicon-on-insulator layer.

8. A transformer as claimed in claim 1 wherein the primary winding is formed in a first silicon-on-insulator layer, the secondary winding is formed in a second silicon-on-insulator layer, and wherein the first and second silicon-on-insulator layers are bonded together.