High temperature flexural mode piezoelectric dynamic pressure sensor

Patent metadata

Field	Value
Publication number	US-9835511-B2
Application number	US-201514707485-A
Country	US
Kind code	B2
Filing date	May 8, 2015
Priority date	May 8, 2015
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

A method for forming a pressure sensor includes forming a base of a sapphire material, the base including a cavity formed therein; forming a sapphire membrane on top of the base and over the cavity; forming a lower electrode on top of the membrane; forming a piezoelectric material layer on an upper surface of the lower electrode, the piezoelectric material layer being formed of aluminum nitride (AIN); and forming at least one upper electrode on an upper surface of the piezoelectric material layer.

First claim

The invention claimed is:

1. A method for forming a flexural mode pressure sensor comprising:
forming a lower substrate having a cavity formed therein;
forming a sapphire membrane on top of the lower substrate and over the cavity to form a base;
forming a lower electrode on top of the membrane;
forming a piezoelectric material layer on an upper surface of the lower electrode, the piezoelectric material layer being formed of aluminum nitride (AIN);
forming at least one upper electrode on an upper surface of the piezoelectric material layer; and
direct bonding the membrane to the lower substrate at a temperature greater than 900° C.;
wherein the lower substrate has a particular orientation;
wherein forming the sapphire membrane includes disposing the membrane over the cavity in the same orientation as the lower substrate; and
wherein forming the lower electrode includes depositing a layer of platinum at a temperature greater than 500° C.

2. The method of claim 1 , wherein the membrane is formed as a sapphire wafer that is polished to a thickness of between 20 um and 200 um.

3. The method of claim 1 , wherein the platinum is deposited in a predominant <111> orientation.

4. The method of claim 1 , wherein forming the piezoelectric material layer includes depositing an A 1 N film on the lower electrode at a temperature greater than 300° C.

5. The method of claim 4 , wherein the AIN film is deposited with a C-plane orientation.

6. The method of claim 1 , further comprising:
depositing a dielectric layer on the piezoelectric film layer; and
forming patterns in the dielectric layer to create contact locations on the piezoelectric material layer for the at least one upper electrode.

7. A dynamic pressure sensor comprising:
a base including a lower substrate with a cavity formed therein and a sapphire membrane disposed over the cavity;
a lower electrode layer on top of the sapphire membrane;
a piezoelectric material layer on an upper surface of the lower electrode, the piezoelectric material layer being formed of aluminum nitride (AIN); and
one upper electrode layer on an upper surface of the piezoelectric material layer;
wherein the lower electrode layer is formed of platinum deposited in a predominant <111> orientation;
wherein the membrane is formed of the same material as the lower substrate.

8. The sensor of claim 7 , wherein the membrane is formed as a sapphire wafer that is polished to a thickness of between 50 um and 125 um.

9. The sensor of claim 7 , wherein the membrane is oriented such that it exhibits the same orientation as the lower substrate.

10. The sensor of claim 7 , wherein the upper electrode is formed of platinum.

Assignees

• Rosemount Aerospace Inc

Inventors

• Zhang Weibin
• Fink Anita
• Childress Kimiko
• Eriksen Odd Harald Steen

Classifications

• H01L41/337

  Electricity · mapped topic

• G01L9/08

  by making use of piezoelectric devices {, i.e. electric circuits therefor} · CPC title

• H01L41/332

  Electricity · mapped topic

• H01L41/187

  Electricity · mapped topic

• G01L9/008 Primary

  using piezoelectric devices (piezoelectric resonators G01L9/0022; surface acoustic waves G01L9/0025) · CPC title