LOW-COST PASSIVE OPTICAL WAVEGUIDE USING SI SUBSTRATE

• US 20120138568A1
• Filed: 12/07/2010
• Published: 06/07/2012
• Est. Priority Date: 12/07/2010
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Na, Yun-Chung N.
• Granted Patent: US 8,437,585 B2
• Time in Patent Office: Days
• US Class Current: 216/24
• CPC Class Codes: G02B 2006/12061 Silicon
• CPC Class Codes: G02B 6/12002 Three-dimensional structures
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: G02B 6/13 Integrated optical circuits characterised by the manufacturing method
• CPC Class Codes: G02B 6/136 by etching

Abstract

A passive optical waveguide is solely built on a Si substrate while still maintaining high optical quality. Two side-by-side diamond shaped cavities may be etched into the Si wafer and oxide grown on the inner walls of the cavities until the oxide meets at opposing inner vertices of the diamond shaped cavities. An optical waveguide is formed by the inverted, generally triangular cross-sectional, portion of silicon remaining between the top surface of the wafer and the opposing inner vertices.

Claims

1. An apparatus, comprising:

a silicon wafer having a top surface, a cross-section of the silicon wafer comprising;

two generally diamond shaped trenches;

an oxide layer in the two generally diamond shaped trenches, the oxide layer converging at inner vertices of the diamond shaped trenches;

a waveguide comprising an inverted generally triangular section of silicon between the top surface of the silicon wafer and the inner vertices of the diamond shaped trenches.

2. The apparatus as recited in claim 1 wherein the top surface of the silicon wafer comprises a (100) crystal orientation.

3. The apparatus as recited in claim 1 wherein inner walls of the diamond shaped trenches comprise a (111) crystal orientation.

4. The apparatus as recited in claim 1 wherein the inner walls of the diamond shaped trenches comprise a ˜

54.7°

angle with respect to normal.

5. The apparatus as recited in claim 1 further comprising an optical device on the top surface over the waveguide.

6. The apparatus as recited in claim 5 wherein the optical device is a laser.

7. The apparatus as recited in claim 5 wherein the optical device is a photodiode.

8. The apparatus as recited in claim 5 wherein the optical device is an electroabsorption modulator

9. A method, comprising:

etching two vertical trenches side-by-side into a top surface of a silicon wafer;

etching the two vertical trenches to create two side-by-side diamond shaped cavities; and

growing oxide on inner walls of the two side-by-side diamond shaped cavities until the oxide meets at opposing inner vertices of the diamond shaped cavities,

wherein an optical waveguide is formed by an inverted generally triangular shaped cross-sectional portion of silicon remaining between the top surface of the wafer and the opposing inner vertices.

10. The method as recited in claim 9, wherein the etching two vertical trenches is accomplished by dry etching.

11. The method as recited in claim 9 wherein the etching the two vertical trenches to create two side-by-side diamond shaped cavities is accomplished by wet etching.

12. The method as recited in claim 11 wherein the wet etching is accomplished by one of KOH (potassium hydroxide), EDP (ethylene diamene pyrocatechol), TMAH (tetramethyl ammonium hydroxide), or NH₄OH (ammonium hydroxide).

13. The method as recited in claim 9 further comprising:

filling the diamond shaped cavities with oxide.

14. The method as recited in claim 9, further comprising:

providing an optical or optoelectronic device over the waveguide.

15. A system, comprising:

a silicon wafer having a top surface, a cross-section of the silicon wafer comprising;

two generally diamond shaped trenches;

an oxide layer in the two generally diamond shaped trenches, the oxide layer converging at inner vertices of the diamond shaped trenches;

a waveguide comprising an inverted generally triangular section of silicon between the top surface of the silicon wafer and the inner vertices of the diamond shaped trenches; and

an optical or optoelectronic device over the waveguide.

16. The system as recited in claim 15 wherein the device comprises a laser.

17. The system as recited in claim 15 wherein the device comprises a photodetector.

18. The system as recited in claim 15 wherein the device comprises an electroabsorption modulator.