Method for making large scale multilayer dielectric diffraction gratings on thick substrates using reactive ion etching

• US 20050231806A1
• Filed: 03/17/2005
• Published: 10/20/2005
• Est. Priority Date: 03/17/2004
• Status: Active Grant

• Current Assignee: General Atomics, Inc.
• Original Assignee: General Atomics, Inc.
• Inventors: Perry, Michael Dale, Barton, Ian Michael
• Granted Patent: US 7,256,938 B2
• Time in Patent Office: Days
• US Class Current: 359/566
• CPC Class Codes: G02B 5/1857 using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams

Abstract

Methods of fabricating large size, high performance multilayer diffraction gratings having a thick substrate that take advantage of reactive ion etching during the fabrication process are provided herein. In one implementation, a method of making a multilayer diffraction grating comprises the steps of: providing a substrate having a thickness of at least 2.0 cm; applying a dielectric structure having a plurality of layers on the semiconductor substrate; depositing a photoresist; exposing the photoresist to a grating pattern; developing the photoresist to produce the grating pattern in the photoresist; and reactive ion etching to transfer the grating pattern to the dielectric structure. In preferred form, the substrate material of the grating is selected to have low electrical resistivity and high thermal conductivity.

Claims

1. A method of making a multilayer diffraction grating comprising:

providing a substrate having a thickness of at least 2.0 cm;

applying a dielectric structure having a plurality of layers on the semiconductor substrate;

depositing a photoresist;

exposing the photoresist to a grating pattern;

developing the photoresist to produce the grating pattern in the photoresist; and

reactive ion etching to transfer the grating pattern to the dielectric structure.

2. The method of claim 1 wherein the substrate comprises a semi-metallic material.

3. The method of claim 2 wherein the semi-metallic material comprises a semiconductor material.

4. The method of claim 2 wherein the semiconductor material comprises boron doped silicon.

5. The method of claim 1 wherein the substrate comprises a material having an electrical resistivity of less than 0.2 Ohm/cm and a thermal conductivity of at least 100 W/m-K.

6. The method of claim 5 wherein the material has an electrical resistivity of less than 0.05 Ohm/cm.

7. The method of claim 1 wherein the substrate comprises a composite substrate including a conductive portion and an insulating portion.

8. The method of claim 1 further comprising forming the substrate by:

providing a conductive substrate;

applying an insulating material to the conductive substrate.

9. The method of claim 1 wherein the substrate has a thickness of at least 2.5 cm.

10. The method of claim 1 wherein the substrate has a width substantially perpendicular to the thickness of at least 12 cm.

11. The method of claim 1 further comprising:

selecting a material for the substrate based on the performance of the material as the substrate when used with reactive ion etching.

12. The method of claim 1 further comprising:

depositing an absorptive coating onto the dielectric structure;

wherein the depositing the photoresist step comprises depositing the photoresist onto the absorptive coating.

13. A multilayer diffraction grating comprising:

a substrate having a thickness of at least 2.0 cm;

a dielectric structure including a plurality of layers formed on the semiconductor layer; and

a grating pattern formed in a surface of the dielectric structure using reactive ion etching.

14. The grating of claim 13 wherein the substrate comprises a semi-metallic material.

15. The grating of claim 14 wherein the semi-metallic material comprises a semiconductor material.

16. The grating of claim 15 wherein the semiconductor material comprises boron doped silicon.

17. The grating of claim 13 wherein the substrate comprises a material having an electrical resistivity of less than 0.2 Ohm/cm and a thermal conductivity of at least 100 W/m-K.

18. The grating of claim 17 wherein the material has an electrical resistivity of less than 0.05 Ohm/cm.

19. The grating of claim 13 wherein the substrate comprises a composite substrate including a conductive portion and an insulating portion.

20. The grating of claim 13 wherein the substrate has a thickness of at least 2.5 cm.

21. The grating of claim 13 wherein the substrate has a width substantially perpendicular to the thickness of at least 12 cm.