High Q quartz-based MEMS resonators and method of fabricating same

Patent metadata

Field	Value
Publication number	US-10141906-B1
Application number	US-201615149026-A
Country	US
Kind code	B1
Filing date	May 6, 2016
Priority date	Jun 15, 2010
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

A method of fabricating a resonator includes providing a first quartz substrate, forming a metallic etch stop on a first surface of the first quartz substrate; attaching, using a temporary adhesive, the first surface of the first quartz substrate to a second quartz substrate, etching an opening for a via in a second surface of the first quartz substrate to the metallic etch stop, forming a metal electrode on the second surface of the first quartz substrate, the metal electrode penetrating the via in the first quartz substrate to make ohmic contact with the metallic etch stop, bonding the metal electrode formed on the second surface of the first quartz substrate to a pad formed on a host substrate; and dissolving the temporary adhesive to release the second quartz substrate from the first quartz substrate, wherein the first quartz substrate and the host substrate each comprise crystalline quartz.

First claim

What is claimed is:

1. A method of fabricating a resonator comprising:
providing a first quartz substrate;
forming a metallic etch stop on a portion of a first surface of the first quartz substrate;
attaching, using a temporary adhesive, the first surface of the first quartz substrate and the metallic etch stop formed thereon to a second quartz substrate;
applying a dry etch mask on a second surface of the first quartz substrate, the dry etch mask including a first opening;
etching, using a dry etchant, through the first opening to thereby etch a via through the first quartz substrate to the metallic etch stop;
forming a metal electrode on the second surface of the first quartz substrate, the metal electrode penetrating the via in the first quartz substrate to make ohmic contact with the metallic etch stop;
bonding the metal electrode formed on the second surface of the first quartz substrate to a pad formed on a host substrate, wherein the first quartz substrate is not in direct contact with the host substrate;
dissolving the temporary adhesive to release the second quartz substrate from the first surface of the first quartz substrate and the metallic etch stop; and
attaching a cap to the host substrate;
wherein the first quartz substrate comprises crystalline quartz which has a first orientation of the crystalline quartz;
wherein the second quartz substrate comprises crystalline quartz which has a second orientation which is the same as the first orientation;
wherein the host substrate comprises crystalline quartz which has a third orientation which is the same as the first orientation;
wherein the cap comprises crystalline quartz which has a fourth orientation which is the same as the first orientation;
wherein the first quartz substrate and the second quartz substrate when attached are aligned so that the first orientation of the first quartz substrate is aligned with the second orientation of the second quartz substrate; and
wherein the first quartz substrate, the host substrate and the cap when attached are aligned so that the first orientation of the first quartz substrate is aligned with the third orientation of the host substrate and aligned with the fourth orientation of the cap.

2. The method of claim 1 wherein the cap comprises a cavity, wherein the cavity is facing the host substrate such that a chamber is produced, wherein the first quartz substrate is enclosed within the chamber.

3. The method of claim 1 :
wherein the metallic etch stop forms an electrode on the first surface of the first quartz substrate; and
wherein the electrode comprises layers of Cr and Au with the Cr layer is disposed closer to the first quartz substrate.

4. The method of claim 1 wherein the step of directing a dry etchant further comprises defining a perimeter shape of the first quartz substrate.

5. The method of claim 4 , wherein the dry etchant comprises a fluorine-based plasma.

6. The method of claim 1 :
wherein a plurality of resonators are formed simultaneously from a single first quartz substrate, the first quartz substrate having a plurality of metallic etch stops, each the etch stop being each formed on a portion of the first surface of the first quartz substrate, the portion aligning with each one of the resonators for each one of the metallic etch stops.

7. The method of claim 1 :
wherein a second metallic electrode is formed on a second surface of the first quartz substrate opposing the metallic etch stop formed on the first surface of the first quartz substrate, the second metallic electrode and the first mentioned metallic electrode being electrically isolated and physically spaced from each other.

8. The method of claim 1 :
wherein prior to the step of forming a metallic etch stop, the method further comprises etching a first mesa on the first surface of the first quartz substrate.

9. The method of claim 8 :
wherein prior to the step of dry etching a via through the first quartz substrate to the etch stop, the method further comprises etching a second mesa in the second surface of the first quartz substrate; and
wherein the first mesa is directly across the quartz wafer from the second mesa.

10. The method of claim 1 wherein the etch stop comprises layers of Cr and Au with the Cr layer disposed closer to the first quartz substrate.

11. The method of claim 2 :
wherein the host substrate comprises a capping seal ring comprising a first metal stack selected from the group consisting of Cr/Pt/Au and Cr/Pt/Au/In; and
wherein the cap comprises a second metal stack comprising Cr/Pt/Au/In, wherein the first metal stack is bonded to the second metal stack.

12. An apparatus, comprising:
a host substrate comprising a first bond pad and a second bond pad;
a quartz resonator comprising a first quartz substrate having a first side and a second side opposite the first side, a via, a first electrode, a second electrode and a third electrode, wherein the first electrode is on the first side and electrically connected to the via, wherein the second electrode is on the second side and is in electrical contact with the via and the first electrode, wherein the second electrode is in physical and electrical contact with the first bond pad, and wherein the third electrode is on the second side and is in physical and electrical contact with the second bond pad;
a first mesa located on the first side and a second mesa located on said second side; and
a cap attached to the host substrate;
wherein the first quartz substrate is not in direct contact with the host substrate;
wherein the first quartz substrate comprises crystalline quartz which has a first orientation of the crystalline quartz;
wherein the host substrate comprises crystalline quartz which has a second orientation which is the same as the first orientation;
wherein the cap comprises crystalline quartz which has a third orientation which is the same as the first orientation; and
wherein the first quartz substrate, the host substrate and the cap are aligned so that the first orientation of the first quartz substrate is aligned with the second orientation of the host substrate and aligned with the third orientation of the cap.

13. The apparatus of claim 12 wherein the cap comprises a cavity, wherein the cavity is facing the host substrate such that the quartz resonator is enclosed within the chamber.

14. The apparatus of claim 13 , wherein said wafer includes a capping seal ring comprising a first metal stack selected from the group consisting of Cr/Pt/Au and Cr/Pt/Au/In, wherein said cap comprises a second metal stack comprising Cr/Pt/Au/In, wherein said first metal stack is bonded to said second metal stack.

15. An apparatus, comprising:
a quartz resonator body comprising a first side, a second side and a via;
a quartz application-specific integrated circuit (ASIC) wafer comprising an electrically conductive first bond pad and an electrically conductive second bond pad;
a quartz cap;
a first mesa defined by a first groove in said first side;
a second mesa defined by a second groove in said second side;
a first electrode overlapping said via and filling a portion of said first groove on said first side;
a contiguous metal portion on said second side and extending into said via such that said contiguous metal portion makes electrical contact with said first electrode;
a second electrode on said second side, wherein said contiguous metal portion is connected to said first electrically conductive bond pad and wherein said second electrode is connected to said second electrically conductive bond pad; and
wherein said quart

Assignees

• Hrl Lab Llc
• Hrl Lab Llc

Inventors

• Chang David T
• Stratton Frederic P
• Nguyen Hung
• Kubena Randall L

Classifications

• H03H2003/027

  the resonators or networks being of the microelectro-mechanical [MEMS] type · CPC title

• H03H9/19

  consisting of quartz · CPC title

• H03H2009/155

  using MEMS techniques · CPC title

• H03H3/02 Primary

  for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence) · CPC title

• H03H3/0072

  of microelectro-mechanical resonators or networks (micromembranes or microbeams B81B2203/01; manufacture of microstructural devices in general B81C) · CPC title