SOI polysilicon trench refill perimeter oxide anchor scheme

• US 20040048410A1
• Filed: 09/09/2002
• Published: 03/11/2004
• Est. Priority Date: 09/09/2002
• Status: Active Grant

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: OʼBrien, Gary J., Monk, David J.
• Granted Patent: US 6,913,941 B2
• Time in Patent Office: Days
• US Class Current: 438/52
• CPC Class Codes: B81B 2203/0118 Cantilevers
• CPC Class Codes: B81B 2203/0307 Anchors
• CPC Class Codes: B81B 2203/033 Trenches
• CPC Class Codes: B81C 1/00039 Anchors

Abstract

A method for creating a MEMS structure is provided. In accordance with the method, a substrate (53) is provided having a sacrificial layer (55) disposed thereon and having a layer of silicon (57) disposed over the sacrificial layer. A first trench (59) is created which extends through the silica layer and the sacrificial layer and which separates the sacrificial layer into a first region (61) enclosed by the first trench and a second region (63) exterior to the first trench. A first material (65) is deposited into the first trench such that the first material fills the first trench to a depth at least equal to the thickness of the sacrificial layer. A second trench (71) is created exterior to the first trench which extends through at least the silicon layer and exposes at least a portion of the second region of the sacrificial layer. The second region of the sacrificial layer is contacted, by way of the second trench, with a chemical etching solution adapted to etch the sacrificial layer, said etching solution being selective to the first material.

Claims

1. A method for creating a MEMS structure, comprising the steps of:

providing a substrate having a sacrificial layer disposed thereon and having a semiconductor layer disposed over the sacrificial layer;

creating a first trench which extends through the semiconductor silicon layer and the sacrificial layer and which separates the sacrificial layer into a first region enclosed by the first trench and a second region exterior to the first trench;

depositing a first material into the first trench such that the first material covers the portion of the sacrificial layer exposed by the first trench;

creating a second trench exterior to the first trench which extends through at least the semiconductor layer and exposes at least a portion of the second region of the sacrificial layer; and

contacting the second region of the sacrificial layer, by way of the second trench, with a chemical etching solution adapted to etch the sacrificial layer, said etching solution being selective to the first material.

2. The method of claim 1, wherein the first material is polysilicon.

3. The method of claim 1, wherein the first material is silicon nitride.

4. The method of claim 1, wherein the first material is deposited into the first trench such that it fills the first trench.

5. The method of claim 1, wherein the first material is deposited such that it fills the first trench and extends beyond the first trench.

6. The method of claim 5, further comprising the step of forming a bond pad over the first material.

7. The method of claim 1, wherein the first trench is lined with the first material, and wherein the first trench is further filled with a second material.

8. The method of claim 7, wherein the first material is silicon nitride and wherein the second material is polysilicon.

9. The method of claim 1, wherein the sacrificial layer comprises silicon dioxide.

10. The method of claim 1, wherein the step of contacting the second region of the sacrificial layer with the chemical etching solution releases a portion of the semiconductor layer so as to form a cantilever in a MEMS structure.

11. The method of claim 1, wherein both the substrate and the semiconductor layer comprise silicon, and wherein the sacrificial layer comprises silicon dioxide.

12. A method for creating a MEMS structure, comprising the steps of:

providing a silicon substrate;

creating a first trench in the substrate which encloses a first region of the substrate;

depositing a first material into the first trench so as to separate the first region of the substrate from the portion of the substrate exterior to the first trench, said first material being selected from the group consisting of polysilicon and silicon nitride;

creating a second trench in the substrate which is exterior to the first trench; and

disposing an etchant in the second trench which etches the substrate and which is selective to the first material.

13. The method of claim 12, wherein the first material is deposited and patterned such that it is disposed in and extends beyond the first trench.

14. The method of claim 12, wherein the etchant is selected from the group consisting of TMAH and EDP.

15. The method of claim 12, wherein the step of disposing the etchant in the second trench releases a portion of the substrate so as to form a cantilever in a MEMS structure.

16. A MEMS structure, comprising:

a cantilevered portion; and

an anchor portion comprising at least one nitride post.

17. The MEMS device of claim 16, wherein the anchor portion includes first and second nitride posts, and wherein the posts are spaced about 2 to about 4 microns apart.

18. The MEMS device of claim 17, wherein each of the posts is essentially cubic.

19. The MEMS device of claim 16, wherein the cantilevered portion comprises silicon.

20. A method for creating a MEMS structure, comprising the steps of:

providing a silicon substrate having a layer of silicon dioxide disposed thereon and having a layer of silicon disposed on the layer of silicon dioxide;

creating at least one aperture which extends through the layer of silicon and the layer of silicon dioxide;

depositing a first material comprising nitride in the at least one aperture, thereby defining an anchor portion;

depositing a second material over the first material so as to define a cantilevered portion; and

etching the silicon oxide with a chemical etching solution which is selective to the first material.

21. The method of claim 20, wherein the first material is deposited by LPCVD.

22. The method of claim 20, wherein the chemical etching solution comprises HF.

23. The method of claim 20, wherein the silicon oxide is etched until the cantilevered portion is released.

24. A MEMS structure, comprising:

a silicon substrate having a layer of silicon dioxide disposed thereon and having a layer of silicon disposed on the layer of silicon dioxide;

a first trench which extends through the layer of silicon and the layer of silicon dioxide and which separates the layer of silicon dioxide into a first region enclosed by the first trench and a second region exterior to the first trench; and

a first material disposed within the first trench, said first material being selected from the group consisting of polysilicon and silicon nitride.

25. The MEMS structure of claim 24, further comprising a second trench exterior to the first trench which extends through at least the silicon layer.

26. The MEMS structure of claim 25, further comprising a third trench disposed between said first and second trench, and wherein said third trench extends through the layer of silicon and encloses at least a portion of the layer of silicon dioxide.

27. The MEMS structure of claim 26, further comprising a fourth trench disposed between said first and third trench, and wherein said fourth trench extends through the layer of silicon and encloses at least a portion of the layer of silicon dioxide.

28. The MEMS structure of claim 25, wherein at least a portion of the second region of the layer of silicon dioxide is exposed by way of said second trench.

29. The MEMS structure of claim 24, wherein the first trench is essentially orthogonal to a major surface of the layer of silicon and encloses at least a first portion of the major surface, and wherein the first material extends beyond the first trench.

30. The MEMS structure of claim 24, further comprising a second material disposed within said first trench, said second material being selected from the group consisting of polysilicon and silicon nitride, and wherein the first and second materials are diverse.

31. A MEMS structure, comprising:

a silicon substrate;

a first trench which extends into the substrate and which encloses at least a portion thereof; and

a first material disposed within the first trench, said first material being selected from the group consisting of polysilicon and silicon nitride.

32. The MEMS structure of claim 31, further comprising a second trench exterior to the first trench which extends into the silicon substrate, and wherein the first material disposed within the first trench is exposed by way of the second trench.

33. The MEMS structure of claim 32, wherein a portion of the substrate bounded by the first and second trenches includes a cantilever in a MEMS structure.

34. The MEMS structure of claim 31, wherein the first trench is essentially orthogonal to a major surface of the substrate and encloses at least a first portion of the substrate, and wherein the first material extends beyond the first trench.