Method of selective etching using etch stop layer

• US 20060066932A1
• Filed: 03/25/2005
• Published: 03/30/2006
• Est. Priority Date: 09/27/2004
• Status: Abandoned Application

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Inventors: Chui, Clarence, Kothari, Manish, Tung, Ming-Hau, Gally, Brian
• Application Number:
  US11/090,773
• Publication Number:
  US 20060066932A1
• Time in Patent Office: Days
• US Class Current: 359/247
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81C 1/00793 Avoid contamination, e.g. absorption of impurities or oxidation
• CPC Class Codes: B81C 1/00801 Avoid alteration of functional structures by etching, e.g. using a passivation layer or an etch stop layer B81C1/00595, B81C1/00468 take precedence
• CPC Class Codes: B81C 2201/014 by depositing an etch stop layer, e.g. silicon nitride, silicon oxide, metal
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26

Abstract

The fabrication of a MEMS device such as an interferometric modulator is improved by employing an etch stop layer between a sacrificial layer and a mirror layer. The etch stop may reduce undesirable over-etching of the sacrificial layer and the mirror layer. The etch stop layer may also serve as a barrier layer, buffer layer, and/or template layer.

Claims

1. An unreleased interferometric modulator comprising:

a sacrificial layer;

a metal mirror layer over the sacrificial layer; and

a thin uniform layer between the sacrificial layer and the metal mirror layer.

2. The unreleased interferometric modulator of claim 1 in which the sacrificial layer comprises a material selected from the group consisting of amorphous silicon, germanium and molybdenum.

3. The unreleased interferometric modulator of claim 2 in which the thin uniform layer comprises an etch stop layer.

4. The unreleased interferometric modulator of claim 3 in which the etch stop layer comprises a material selected from the group consisting of a silicon oxide, amorphous silicon, a silicon nitride, germanium, titanium, and tungsten.

5. The unreleased interferometric modulator of claim 3 in which the sacrificial layer comprises a material selected from the group consisting of germanium and molybdenum.

6. The unreleased interferometric modulator of claim 3 in which the sacrificial layer comprises amorphous silicon and the thin uniform layer comprises a material selected from the group consisting of titanium and tungsten.

7. The unreleased interferometric modulator of claim 2 in which the thin uniform layer comprises a diffusion barrier layer that slows diffusion of metal from the metal mirror layer into the sacrificial layer.

8. The unreleased interferometric modulator of claim 7 in which the diffusion barrier layer comprises a material selected from the group consisting of a silicon oxide, a silicon nitride, titanium, and tungsten.

9. The unreleased interferometric modulator of claim 2 in which the thin uniform layer comprises a buffer layer that substantially prevents a crystallographic orientation of the sacrificial layer from producing a corresponding crystallographic orientation of the metal mirror layer.

10. The unreleased interferometric modulator of claim 9 in which the buffer layer comprises a material selected from the group consisting of a silicon oxide and a silicon nitride.

11. The unreleased interferometric modulator of claim 2 in which the thin uniform layer comprises a template layer having a crystalline orientation that is substantially similar to a crystallographic orientation of the metal mirror layer.

12. The unreleased interferometric modulator of claim 11 in which the template layer comprises a material selected from the group consisting of titanium and tungsten.

13. The unreleased interferometric modulator of claim 1 in which the metal mirror layer comprises aluminum.

14. The unreleased interferometric modulator of claim 13 in which the metal mirror layer comprises an aluminum alloy selected from the group consisting of Al—

Si, Al—

Cu, Al—

Ti, and Al—

Nd.

15. The unreleased interferometric modulator of claim 1 in which the thin uniform layer has a thickness in the range of about 100 Å

to about 700 Å

.

16. A method of making an interferometric modulator, comprising:

depositing a sacrificial layer over a first mirror layer;

depositing an etch stop layer over the sacrificial layer;

depositing a second mirror layer over the etch stop layer; and

removing the sacrificial layer to expose a portion of the etch stop layer underlying the second mirror layer.

17. The method of claim 16 further comprising selectively removing the portion of the etch stop layer underlying the second mirror layer.

18. The method of claim 17 in which selectively removing the portion of the etch stop layer underlying the second mirror layer comprising etching the portion of the etch stop layer using an etchant that removes the portion of the etch stop layer at a rate that is at least about 10 times faster than a rate at which the etchant removes the second mirror layer.

19. The method of claim 16 in which removing the sacrificial layer comprises etching the sacrificial layer using an etchant that removes the sacrificial layer at a rate that is at least about 10 times faster than a rate at which the etchant removes the etch stop layer.

20. The method of claim 19 in which the etchant comprises XeF₂.

21. The method of claim 16 in which the sacrificial layer comprises a material selected from the group consisting of amorphous silicon, germanium and molybdenum.

22. The method of claim 16 in which the etch stop layer comprises a material selected from the group consisting of a silicon oxide, amorphous silicon, a silicon nitride, germanium, titanium, and tungsten.

23. A method of making an interferometric modulator, comprising:

depositing a sacrificial layer over a first mirror layer;

depositing an etch stop layer over the sacrificial layer;

depositing a second mirror layer over the etch stop layer; and

removing a portion of the second mirror layer to expose the etch stop layer, thereby forming an exposed portion of the etch stop layer and an unexposed portion of the etch stop layer, the unexposed portion of the etch stop layer underlying a remaining portion of the second mirror layer.

24. The method of claim 23 further comprising removing the exposed portion of the etch stop layer.

25. The method of claim 24 further comprising selectively removing the sacrificial layer to expose the portion of the etch stop layer underlying the remaining portion of the second mirror layer.

26. The method of claim 25 further comprising selectively removing the etch stop layer underlying the remaining portion of the second mirror layer.

27. An interferometric modulator made by the method of claim 26.

28. The method of claim 23 in which removing the portion of the second mirror layer to expose the etch stop layer comprises etching the second mirror layer using an etchant that removes the second mirror layer at a rate that is at least about 10 times faster than a rate at which the etchant removes the etch stop layer.

29. The method of claim 28 in which the etchant comprises an aqueous acid.

30. The method of claim 23 in which the sacrificial layer comprises a material selected from the group consisting of amorphous silicon, germanium and molybdenum.

31. The method of claim 30 in which the etch stop layer comprises a material selected from the group consisting of a silicon oxide, amorphous silicon, a silicon nitride, germanium, titanium, and tungsten.

32. An unreleased interferometric modulator made by the method of claim 23.

33. A method of making an interferometric modulator, comprising:

depositing a sacrificial layer over a first mirror layer, the sacrificial layer comprising a material selected from the group consisting of amorphous silicon, germanium and molybdenum;

depositing a thin uniform layer over the sacrificial layer, the thin uniform layer having a thickness in the range of about 100 Å

to about 700 Å

, the thin uniform layer comprising a material selected from the group consisting of a silicon oxide, amorphous silicon, a silicon nitride, germanium, titanium, and tungsten;

depositing a second mirror layer over the thin uniform layer, the second mirror layer comprising a metal selected from the group consisting of Al, Al—

Si, Al—

Cu, Al—

Ti, and Al—

Nd;

removing a portion of the second mirror layer to expose the thin uniform layer, thereby forming an exposed portion of the thin uniform layer and an unexposed portion of the thin uniform layer, the unexposed portion of the thin uniform layer underlying a remaining portion of the second mirror layer; and

removing the sacrificial layer to expose the previously unexposed portion of the thin uniform layer underlying the remaining portion of the second mirror layer.