Monolithic fabrication of thermally isolated microelectromechanical system (mems) devices

Patent metadata

Field	Value
Publication number	US-2016340174-A1
Application number	US-201514806201-A
Country	US
Kind code	A1
Filing date	Jul 22, 2015
Priority date	May 22, 2015
Publication date	Nov 24, 2016
Grant date	—

Abstract

A method for fabricating a thermally isolated microelectromechanical system (MEMS) structure is provided. The method includes processing a first wafer of a first material with a glass wafer to form a composite substrate including at least one sacrificial structure of the first material and glass; forming a MEMS device in a second material; forming at least one temperature sensing element on at least one of: the composite substrate; and the MEMS device; and etching away the at least one sacrificial structure of the first material in the composite substrate to form at least one thermally isolating glass flexure. The MEMS device is thermally isolated on a thermal isolation stage by the at least one thermally isolating glass flexure. The at least one temperature sensing element in on a respective at least one of: the thermal isolation stage; and the MEMS device.

First claim

What is claimed is:

1 . A method for fabricating a thermally isolated microelectromechanical system (MEMS) structure, the method comprising:
processing a first wafer of a first material with a glass wafer to form a composite substrate including at least one sacrificial structure of the first material and glass; forming a MEMS device in a second material; forming at least one temperature sensing element on at least one of: the composite substrate; and the MEMS device; and etching away the at least one sacrificial structure of the first material in the composite substrate to form at least one thermally isolating glass flexure, wherein the MEMS device is thermally isolated on a thermal isolation stage by the at least one thermally isolating glass flexure, and wherein the at least one temperature sensing element in on a respective at least one of: the thermal isolation stage; and the MEMS device.

2 . The method of claim 1 , wherein processing the first wafer of the first material with the glass wafer to form the composite substrate comprises:
etching a layer of the first material to form the at least one sacrificial structure, the at least one sacrificial structure defining a mold for the at least one thermally isolating glass flexure and the thermal isolation stage; bonding the at least one sacrificial structure of the first material to the glass wafer in an atmosphere that is less than an external ambient atmosphere; heating the glass wafer beyond the glass softening temperature to form a modified-glass wafer in which the at least one sacrificial structure of the first material is embedded in glass; polishing a first surface of the modified-glass wafer; and polishing a second surface of the modified-glass wafer.

3 . The method of claim 2 , wherein the glass wafer is a first glass wafer, and the composite substrate is a first composite substrate, the method further comprising:
processing a third wafer of a third material with a second glass wafer to form a second composite substrate including at least one sacrificial structure of the third material and glass; and bonding the second composite substrate to one of: a second wafer that includes the MEMS device; and the first composite substrate.

4 . The method of claim 3 , wherein the thermal isolation stage is a first thermal isolation stage, wherein the modified-glass wafer is a first modified-glass wafer, and wherein processing the third wafer of the third material with the second glass wafer to form the second composite substrate including at least one sacrificial structure of the third material and glass comprises:
etching a layer of the third material to form the at least one sacrificial structure, the at least one sacrificial structure defining a mold for at least one thermally isolating glass flexure and a second thermal isolation stage for the MEMS device; bonding the at least one sacrificial structure of the third material to the second glass wafer in an atmosphere that is less than an external ambient atmosphere; heating the second glass wafer beyond the glass softening temperature to form a second modified-glass wafer in which the at least one sacrificial structure of the third material is embedded in glass; polishing a first surface of the second modified-glass wafer; and polishing a second surface of the second modified-glass wafer.

5 . The method of claim 1 , wherein forming the MEMS device in the second material comprises:
depositing a layer of the second material on the composite substrate; and patterning and etching the layer of the second material.

6 . The method of claim 1 , wherein forming the MEMS device in the second material comprises:
processing a second wafer in the second material to form the MEMS device on the second wafer; and bonding the second wafer to the composite substrate.

7 . The method of claim 1 , further comprising:
depositing at least one electrically-conductive layer on the polished first surface of the composite substrate; and patterning and etching the at least one electrically-conductive layer to form at least one of: circuits; circuit components; conductive interconnects; bond pads; electrodes; resistors for heating; and resistors for temperature read-out.

8 . The method of claim 1 , further comprising:
forming at least one temperature controlling element on at least one of: the composite substrate; and the MEMS device, wherein upon etching away the at least one sacrificial structure of the first material in the composite substrate, the at least one temperature controlling element is on a respective at least one of: the thermal isolation stage; and the MEMS device.

9 . The method of claim 1 , wherein forming the at least one temperature sensing element on at least one of: the composite substrate; and the MEMS device comprises:
patterning at least one resistive element on a polished first surface of the composite substrate, wherein, upon etching away the at least one sacrificial structure of the first material in the composite substrate, the at least one temperature sensing element is on the thermal isolation stage.

10 . A method for fabricating a thermally isolated microelectromechanical system (MEMS) structure, the method comprising:
forming a composite substrate containing at least one embedded sacrificial structure by:
etching a layer of a first material to form the at least one sacrificial structure, the at least one sacrificial structure defining a mold for at least one thermally isolating glass flexure and a thermal isolation stage for a MEMS device;
bonding the layer of the first material to a glass wafer in an atmosphere that is less than an external ambient atmosphere;
heating the glass wafer beyond the glass softening temperature to form a modified-glass wafer in which the at least one sacrificial structure is embedded in glass;
polishing a first surface of the modified-glass wafer; and
polishing a second surface of the modified-glass wafer;
forming a MEMS device in a second material; forming at least one temperature sensing element on at least one of: the composite substrate; and the MEMS device; and etching away the at least one sacrificial structure of the first material in the composite substrate to form the at least one thermally isolating glass flexure and the thermal isolation stage, wherein the MEMS device is thermally isolated on the thermal isolation stage.

11 . The method of claim 10 , wherein forming the MEMS device in the second material comprises:
depositing a layer of the second material on the composite substrate; and patterning and etching the layer of the second material.

12 . The method of claim 10 , wherein forming the MEMS device in the second material comprises:
processing a second wafer in the second material to form the MEMS device, the method further comprising: forming raised areas on the polished first surface of the composite substrate; and bonding the second wafer to the raised areas of composite substrate.

13 . The method of claim 12 , wherein the composite substrate is a first composite substrate, the method further comprising:
processing a third wafer of a third material to form a second composite substrate including at least one sacrificial structure of the third material and glass; and bonding the processed third wafer to the second wafer including the MEMS device.

14 . The method of claim 13 , wherein the mold is a first mold, the glass wafer is a first glass wafer, the modified-glass wafer is a first modified-glass wafer, and the thermal isolation stage is a first thermal isolation stage, and wherein processing the

Assignees

• Honeywell Int Inc

Inventors

• Reinke John R
• Lodden Grant H

Classifications

• B81B7/0087 Primary

  On-device systems and sensors for controlling, regulating or monitoring · CPC title

• H02N1/00

  Electrostatic generators or motors using a solid moving electrostatic charge carrier · CPC title

• B81B2201/0228

  Inertial sensors · CPC title

• B81C1/0069 Primary

  Thermal properties, e.g. improve thermal insulation · CPC title

• B81B7/0019 Primary

  Protection against thermal alteration or destruction (B81B7/0083 takes precedence) · CPC title