PRESSURE SENSOR HAVING GOLD-SILICON EUTECTIC CRYSTAL LAYER INTERPOSED BETWEEN CONTACT LAYER AND SILICON SUBSTRATE

Abstract

A pressure sensor includes a gold-silicon eutectic crystal layer interposed between the contact layer and the silicon substrate. Because the contact layer and the silicon substrate are electrically connected to each other by using a gold-silicon eutectic reaction at the time of bonding the silicon substrate and the glass substrate, a contact resistance between the contact layer and the silicon substrate can be stabilized, and a Q value of the sensor can be stabilized. In addition, since the contact layer and the silicon substrate are bonded to each other by the gold-silicon eutectic reaction, the bonding strength is sufficient.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating a configuration of a capacitive pressure sensor according to a first embodiment, where FIG. 1A is a plan view and FIG. 1B is a sectional view taken along Line Ib-Ib of FIG. 1A.

FIGS. 2A to 2C are sectional views illustrating a method of manufacturing a capacitive pressure sensor according to the first embodiment of the invention.

FIG. 3 is a schematic diagram illustrating a configuration of a capacitive pressure sensor according to a second embodiment of the invention.

FIGS. 4A to 4D are sectional views illustrating a method of manufacturing a capacitive pressure sensor according to the second embodiment of the invention.

FIG. 5 is a sectional view illustrating a known capacitive pressure sensor.

FIG. 6 is a schematic diagram showing a configuration of a capacitive pressure sensor, where FIG. 6A is a plan view and FIG. 6B is a sectional view taken along Line IVb-IVb of FIG. 6A according to a third embodiment of the invention.

FIG. 7A is a diagram illustrating a non-bonded area of a capacitive pressure sensor according to the third embodiment of the invention.

FIG. 7B is a diagram illustrating a relationship between a thickness of a contact layer and the non-bonded area.

FIGS. 8A to 8D are sectional views illustrating a method of manufacturing a capacitive pressure sensor according to the third embodiment of the invention.

Claims

1. A capacitive pressure sensor comprising: a glass substrate having a fixed electrode;a silicon substrate having a movable electrode;a bonded area between the glass substrate and the silicon substrate;an extraction electrode formation area on the glass substrate for the movable electrode;a contact layer extending from the bonded area to the extraction electrode formation area; anda gold-silicon eutectic crystal layer provided between the contact layer and the silicon substrate in the bonded area.

2. The capacitive pressure sensor according to claim 1, wherein the bonded area includes a recess portion and the contact layer is formed in the recess portion.

3. The capacitive pressure sensor according to claim 2, wherein a depth of the recess portion is set so that the glass substrate and the contact layer are flush with each other at the time of forming the contact layer in the recess portion.

4. The capacitive pressure sensor according to claim 1, wherein a gold layer is formed on the extraction electrode formation area of the contact layer in a state where the gold layer is separated from the gold-silicon eutectic crystal layer.

5. The capacitive pressure sensor according to claim 1, wherein a distance from an outer end portion of a non-bonded area which is formed in the bonded area to an end portion of a cavity is 150 μm or more and a height of the contact layer protruding from a surface of the glass substrate is 3000 Å or less.

6. The capacitive pressure sensor according to claim 5, wherein the bonded area has a recess portion and the contact layer is formed in the recess portion.

7. The capacitive pressure sensor according to claim 5, wherein an interface between the glass substrate and the silicon substrate has one of a Si—Si bond or a Si—O bond.

8. A method of forming a capacitive pressure sensor comprising the steps of: providing a glass substrate having a fixed electrode, and a silicon substrate having a movable electrode;bonding an area between the glass substrate and the silicon substrate;forming an extraction electrode area on the glass substrate for the movable electrode;forming a contact layer extending from the bonded area to the extraction electrode area; andproviding a gold-silicon eutectic crystal layer between the contact layer and the silicon substrate in the bonded area.

9. The method according to claim 8, including forming a recess portion in the bonded area and forming a contact layer in the recess portion.

10. The method according to claim 9, including setting a depth of the recess portion so that the glass substrate and the contact layer are flush with each other at the time of forming the contact layer.