Sloped termination in molybdenum layers and method of fabricating

Patent metadata

Field	Value
Publication number	US-9660603-B2
Application number	US-201514682651-A
Country	US
Kind code	B2
Filing date	Apr 9, 2015
Priority date	Apr 9, 2015
Publication date	May 23, 2017
Grant date	May 23, 2017

Abstract

A method of fabricating a sloped termination of a molybdenum layer includes providing the molybdenum layer and applying a photo resist material to the molybdenum layer. The photo resist material is exposed under a defocus condition to generate a resist mask having an edge portion. The molybdenum layer is etched at least at the edge portion of the resist mask to result in a sloped termination of the molybdenum layer.

First claim

What is claimed is:

1. A method of fabricating a sloped termination of a molybdenum layer, the method comprising:
forming the molybdenum layer;
applying a photo resist material to the molybdenum layer;
exposing the photo resist material under a defocus condition to generate a resist mask having an edge portion, wherein the defocus condition is between +/−11um and +/−22 um;
etching the molybdenum layer at least at the edge portion of the resist mask to result in a sloped termination of the molybdenum layer.

2. The method of claim 1 , wherein forming the molybdenum layer comprises forming a molybdenum layer on an oxide layer.

3. The method of claim 1 , wherein the etching comprises exposing the molybdenum layer and the photo resist material to a gas comprising chlorine and oxygen.

4. The method of claim 3 , wherein the ratio of oxygen to chlorine is between 3:1 and 5:1.

5. The method of claim 3 , wherein the ratio of oxygen to chlorine is approximately 4:1.

6. The method of claim 1 , wherein the etching comprises applying a low transformer coupled plasma between 275 watts and 400 watts.

7. The method of claim 1 , wherein the etching comprises applying a low transformer coupled plasma at approximately 300 watts.

8. The method of claim 1 , wherein the etching comprises applying a bias RF of between −125 peak volts and −175 peak volts.

9. The method of claim 1 , wherein the etching comprises applying a bias RF of approximately −150 volts.

10. The method of claim 1 , wherein the defocus condition is approximately +/−17 um.

11. The method of claim 1 , wherein the etching material has a selectivity of molybdenum to aluminum nitride that is greater than 100:1.

12. The method of claim 1 , wherein the etching material has a selectivity of molybdenum to oxide that is greater than 100:1.

13. A method of fabricating a Bragg mirror having a sloped termination of a molybdenum layer, the method comprising:
forming the molybdenum layer on a seed layer;
applying a photo resist material to the molybdenum layer;
exposing the photo resist material under a defocus condition to generate a resist mask, an edge of the exposed photo resist material corresponding to a region of the molybdenum layer that is to become the sloped termination, wherein the defocus condition is between +/−11 um and +/−22 um;
etching the molybdenum layer with an etching material, wherein the etching material at least partially etches the photo resist material exposed under the defocused condition, the etching resulting in the sloped termination.

14. The method of claim 13 wherein the seed layer is a seed layer for aluminum nitride.

15. The method of claim 13 , wherein the seed layer is an oxide.

16. The method of claim 13 , wherein the etching comprises exposing the molybdenum layer and the photo resist material to a gas comprising oxygen and chlorine gas in a ration of oxygen to chlorine between 3:1 and 5:1.

17. The method of claim 13 , wherein the etching comprises applying a low transformer coupled plasma between 275 watts and 400 watts.

18. The method of claim 13 , wherein the etching comprises applying a bias RF of between −125 peak volts and −175 peak volts.

19. The method of claim 13 , wherein the etching material has a selectivity of molybdenum to aluminum nitride that is greater than 100:1 and a selectivity of molybdenum to oxide that is greater than 100:1.

20. A method of fabricating a sloped termination of a molybdenum layer, the method comprising:
providing the molybdenum layer;
applying a photo resist material to the molybdenum layer;
exposing the photo resist material under a defocus condition of between +/−11 um and +/−22 um to generate a resist mask, an edge of the exposed photo resist material corresponding to the sloped termination;
etching the molybdenum layer with an etching material, wherein the etching material having a selectivity of molybdenum to aluminum nitride that is greater than 100:1 and a selectivity of molybdenum to oxide that is greater than 100:1 that at least partially etches the photo resist material exposed under the defocused condition, the etching resulting in the sloped termination.

Assignees

• Texas Instruments Inc

Inventors

• Jiang Neng
• Stewart Elizabeth Costner
• Dellas Nicholas S

Classifications

• H03H3/02 Primary

  for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence) · CPC title

• H03H2003/025

  the resonators or networks comprising an acoustic mirror · CPC title