Method for preparing optical waveguide substrate

• US 6,615,614 B1
• Filed: 07/06/2000
• Issued: 09/09/2003
• Est. Priority Date: 07/07/1999
• Status: Expired due to Fees

• Current Assignee: Shin-Etsu Chemical Company Limited
• Original Assignee: Shin-Etsu Chemical Company Limited
• Inventors: Makikawa, Shinji, Konishi, Shigeru, Ejima, Seiki
• Primary Examiner(s): HOFFMANN, JOHN M
• Application Number:
  US09/610,952
• Time in Patent Office: 1,160 Days
• Field of Search: 653/86, 654/29, 654/13, 654/30
• US Class Current: 65/386
• CPC Class Codes: G02B 2006/12038 Glass (SiO2 based materials)
• CPC Class Codes: G02B 2006/12061 Silicon
• CPC Class Codes: G02B 6/122 Basic optical elements, e.g. light-guiding paths
• CPC Class Codes: G02B 6/132 by deposition of thin films
• CPC Class Codes: G02B 6/136 by etching

Abstract

An optical waveguide substrate is prepared by forming grooves in a silicon substrate in accordance with the pattern of a desired waveguide device, thermally oxidizing the silicon substrate to form a peripheral quartz layer surrounding the grooves, burying in the grooves a doped quartz glass layer having a higher refractive index, abrading the surface of the resulting structure to be flat, and forming on the flat surface a glass layer having a lower refractive index. An optical waveguide substrate featuring no distortion of the core pattern, little warp, and a low loss can be produced in a simple manner.

Claims

1. A method for preparing an optical waveguide substrate, comprising the steps of:

forming concave grooves in one surface of a silicon substrate in accordance with the pattern of a desired waveguide device,

thermally oxidizing the silicon substrate to form a peripheral, quartz layer surrounding the grooves,

burying in the grooves a doped quartz glass layer having a higher refractive index than the peripheral quartz layer,

abrading the surface of the resulting structure to be a flat to define higher refractive index quartz glass layer segments in the grooves, and

forming on the flat surface a glass layer having a lower refractive index than the quartz glass layer, wherein light propagates through the higher refractive index quartz glass layer segments buried in the grooves.

2. The method of claim 1, wherein the concave grooves are formed by photolithography and etching.

3. The method of claim 2, wherein the etching is by dry etching.

4. The method of claim 2, wherein the finished optical waveguide substrate has higher refractive index quartz glass layer segments in the grooves which are spaced apart 20 μ

m or less.

5. The method of claim 1, wherein the thermal oxidizing of the silicon substrate is conducted in an atmosphere of steam, dry oxygen, halogen or nitrogen oxide.

6. The method of claim 5, wherein the atmosphere is a pressurized atmosphere.

7. The method of claim 1, wherein the doped quartz glass layer having a higher refractive index than the peripheral quartz layer is doped with GeO₂ or TiO₂.

8. The method of claim 1, wherein doped quartz glass layer having a higher refractive index than the peripheral quartz layer is formed by flame deposition.

9. The method of claim 1, wherein the glass layer having a lower refractive index than the quartz glass layer is formed on the flat surface to a thickness of about 20 μ

m.

10. The method of claim 1, wherein the glass layer having a lower refractive index than the quartz glass layer is formed on the flat surface by evaporation, ion plating or plasma chemical vapor deposition.

11. The method of claim 1, wherein the glass layer having a lower refractive index than the quartz glass layer is formed on the flat surface by flame deposition.

12. The method of claim 1, wherein the glass layer having a lower refractive index than the quartz glass layer contains B₂O₃ or P₂O₅ to give it the lower refractive index.

13. The method of claim 1, wherein the abrading is by conventional grinding machine, chemical mechanical polishing or by reactive ion etching.

14. The method of claim 1, wherein the abrading is by conventional grinding machine or chemical mechanical polishing.