Microelectromechanical systems having trench isolated contacts, and methods for fabricating same

• US 20040245586A1
• Filed: 06/04/2003
• Published: 12/09/2004
• Est. Priority Date: 06/04/2003
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Partridge, Aaron, Lutz, Markus, Kronmueller, Silvia
• Granted Patent: US 6,936,491 B2
• Time in Patent Office: Days
• US Class Current: 257/414
• CPC Class Codes: B81B 2207/015 the micromechanical device and the control or processing electronics being integrated on the same substrate
• CPC Class Codes: B81B 2207/095 through the lid
• CPC Class Codes: B81C 1/00301 Connecting electric signal lines from the MEMS device with external electrical signal lines, e.g. through vias
• CPC Class Codes: B81C 2201/0176 Chemical vapour Deposition
• CPC Class Codes: B81C 2203/0136 Growing or depositing of a covering layer

Abstract

There are many inventions described and illustrated herein. In one aspect, the present invention is directed to a MEMS device, and technique of fabricating or manufacturing a MEMS device, having mechanical structures encapsulated in a chamber prior to final packaging and a contact area disposed at least partially outside the chamber. The contact area is electrically isolated from nearby electrically conducting regions by way of dielectric isolation trench that is disposed around the contact area. The material that encapsulates the mechanical structures, when deposited, includes one or more of the following attributes: low tensile stress, good step coverage, maintains its integrity when subjected to subsequent processing, does not significantly and/or adversely impact the performance characteristics of the mechanical structures in the chamber (if coated with the material during deposition), and/or facilitates integration with high-performance integrated circuits. In one embodiment, the material that encapsulates the mechanical structures is, for example, silicon (polycrystalline, amorphous or porous, whether doped or undoped), silicon carbide, silicon-germanium, germanium, or gallium-arsenide.

Claims

1. A method of sealing a chamber of an electromechanical device having a mechanical structure and a contact portion overlying a substrate, wherein the mechanical structure is in the chamber, the method comprising:

depositing a sacrificial layer over at least a portion of the mechanical structure;

depositing a first encapsulation layer over the sacrificial layer;

forming at least one vent through the first encapsulation layer to allow removal of at least a portion of the sacrificial layer;

removing at least a portion of the sacrificial layer to form the chamber;

depositing a second encapsulation layer over or in the vent to seal the chamber wherein the second encapsulation layer is a semiconductor material;

forming a trench around the contact portion wherein the contact portion is disposed outside the chamber; and

depositing an insulating material in the trench to electrically isolate the contact.

2. The method of claim 1 wherein the semiconductor material is comprised of polycrystalline silicon, amorphous silicon, silicon carbide, silicon/germanium, germanium, or gallium arsenide.

3. The method of claim 2 wherein the first encapsulation layer is comprised of a polycrystalline silicon, amorphous silicon, germanium, silicon/germanium or gallium arsenide.

4. The method of claim 1 wherein the trench surrounds the contact to electrically isolate the contact.

5. The method of claim 1 further including depositing a semiconductor material in the trench after depositing the insulating material.

6. The method of claim 1 further including planarizing an exposed surface of the trench.

7. The method of claim 1 wherein the insulating material is silicon dioxide or silicon nitride.

8. The method of claim 1 further including:

depositing an insulating layer on at least a portion of the trench;

depositing an highly conductive material on the contact and over the insulating layer to provide electrical connection to the contact.

16. The method of claim 1 further including:

depositing an insulating layer on at least a portion of the trench;

depositing an highly conductive material on the contact and over the insulating layer to provide electrical connection to the contact.

9. A method of manufacturing an electromechanical device having a mechanical structure that resides in a chamber and wherein the electromechanical device further includes a contact, the method comprising:

depositing a first encapsulation layer over the mechanical structure wherein the first encapsulation layer is a semiconductor material;

forming at least one vent in the first encapsulation layer;

forming the chamber;

depositing a second encapsulation layer over or in the vent to seal the chamber wherein the second encapsulation layer is a semiconductor material;

forming a trench around at least a portion of the contact wherein the contact and the trench as disposed outside the chamber; and

depositing a first material in the trench to electrically isolate the contact.

10. The method of claim 9 wherein the first encapsulation layer is comprised of polycrystalline silicon, amorphous silicon, silicon carbide, silicon/germanium, germanium, or gallium arsenide.

11. The method of claim 9 wherein the first material is silicon dioxide or silicon nitride.

12. The method of claim 9 wherein the second encapsulation layer is comprised of polycrystalline silicon, porous polycrystalline silicon, amorphous silicon, silicon carbide, silicon/germanium, germanium, or gallium arsenide.

13. The method of claim 9 wherein the trench surrounds the contact to electrically isolate the contact.

14. The method of claim 9 further including depositing a semiconductor material in the trench after depositing the first material and wherein the first material is disposed on the outer surfaces of the trench.

15. The method of claim 14 further including planarizing an exposed surface of the trench.

17. An electromechanical device comprising:

a chamber including a first encapsulation layer;

a mechanical structure, wherein at least a portion of the mechanical structure is disposed in the chamber;

a second encapsulation layer comprised of a semiconductor material, deposited over or in the vent, to thereby seal the chamber;

a contact;

a trench, disposed around at least a portion of the contact wherein the contact and the trench as disposed outside the chamber and wherein the trench includes a first material disposed therein to electrically isolate the contact.

18. The electromechanical device of claim 17 wherein the second encapsulation layer is comprised of polycrystalline silicon, porous polycrystalline silicon, amorphous silicon, silicon carbide, silicon/germanium, germanium, or gallium arsenide.

19. The electromechanical device of claim 18 wherein the first encapsulation layer is comprised of polycrystalline silicon, porous polycrystalline silicon, amorphous silicon, germanium, silicon/germanium, gallium arsenide, silicon nitride or silicon carbide.

20. The electromechanical device of claim 17 wherein the first material is an insulating material is disposed on at least the outer surfaces of the trench.

21. The electromechanical device of claim 20 wherein the trench includes a second material in a central portion of the trench and wherein the second material is a semiconductor material.

22. The electromechanical device of claim 20 wherein the trench is disposed on an etch stop region.

23. The electromechanical device of claim 20 wherein the etch stop region is a silicon nitride or silicon dioxide.

24. The electromechanical device of claim 20 wherein the first material is a silicon nitride or silicon dioxide.

25. The electromechanical device of claim 20 wherein the trench surrounds the contact.