MEMS chip, measuring element and pressure sensor for measuring a pressure

Patent metadata

Field	Value
Publication number	US-9927316-B2
Application number	US-201415024482-A
Country	US
Kind code	B2
Filing date	Oct 2, 2014
Priority date	Oct 3, 2013
Publication date	Mar 27, 2018
Grant date	Mar 27, 2018

Abstract

A micro-electro-mechanical system (MEMS) chip for measuring a pressure in a pressure space includes a MEMS substrate having a measuring region, a contact-making region connected to the measuring region via lines and having contacts, and a bushing region disposed between the measuring region and the contact-making region. The MEMS substrate defines a cavity formed as a blind hole that defines an opening through one side of the MEMS substrate, the bottom of the blind hole forming a membrane. A measuring bridge includes piezoresistive elements disposed on that side of the membrane which faces away from the cavity's opening. A carrier substrate is disposed over the cavity's opening and bonded to the MEMS substrate in a two-dimensional manner to form a rod, with the result that the carrier substrate forms a bottom wall of the cavity spaced apart from the membrane.

First claim

The invention claimed is:

1. A micro-electro-mechanical system chip (MEMS chip) for measuring a pressure in a pressure space, comprising:
a MEMS substrate elongating along a longitudinal axis, wherein material removed from the MEMS substrate forms a blind hole with an open end and a bottom opposite the open end, wherein the bottom of the blind hole forms a membrane;
a carrier substrate elongating along the longitudinal axis and bonded to the MEMS substrate such that the open end of the blind hole faces the carrier substrate and the carrier substrate forms a bottom wall of a cavity defined between the membrane and the carrier substrate;
a measuring bridge that includes piezoresistive elements arranged on a side of the membrane which faces away from the open end of the blind hole; and
conductors connected to the piezoresistive elements and leading away therefrom along the longitudinal axis;
wherein in an operating state the piezoresistive elements on the side of the membrane which faces away from the open end of the blind hole are exposed to the pressure space such that fluctuations of pressure in the pressure space cause the piezoresistive elements to produce measured signals transmitted through the conductors.

2. The MEMS chip according to claim 1 , further comprising contacts disposed on the same surface of the MEMS chip that includes the membrane.

3. The MEMS chip according to claim 2 , wherein for differential pressure measurements the cavity is extended with formation of a channel, which extends into a region of the MEMS chip that supports the contacts and ends in an opening.

4. The MEMS chip according to claim 3 , wherein in the region in which the channel is formed, no bonding material is present between the MEMS substrate and the carrier substrate.

5. The MEMS chip according to claim 1 , wherein the thickness of the bottom wall of the cavity is greater than twice the thickness of the membrane.

6. The MEMS chip according to claim 2 , wherein the MEMS substrate is an SOI-substrate, and the carrier substrate is an Si-carrier substrate.

7. The MEMS chip according to claim 1 , wherein the cavity is extended with formation of a channel, which extends into a region of the MEMS chip that supports the contacts and there terminates in a further closed cavity.

8. The MEMS chip according to claim 7 , wherein a getter is arranged in the further closed cavity.

9. The MEMS chip according to claim 1 , wherein the blind hole has steep walls, and each of the steep walls stands essentially at a right angle to the membrane.

10. The MEMS chip according to claim 1 , wherein the membrane is bounded towards the blind hole by an oxide layer.

11. The MEMS chip according to claim 10 , wherein the piezoresistive elements are configured as resistances in the membrane adjacent to the oxide layer.

12. A measuring element comprising:
a MEMS chip according to claim 1 , and
a bushing, which is formed by a casting compound and a holding ring, the casting compound being disposed surrounding the bushing region of the MEMS chip, the holding ring enclosing the casting compound.

13. The measuring element according to claim 12 , wherein the casting compound is glass, solder, or an adhesive.

14. The measuring element according to claim 12 wherein a passivation layer surrounds the piezoresistive elements.

15. The measuring element according to claim 12 wherein the contacts are connected by clamping with a clamping contact.

16. The measuring element according to claim 12 , wherein the holding ring extends along the longitudinal axis and protrudes beyond the casting compound in the direction of the measuring region.

17. A micro-electro-mechanical system chip (MEMS chip) for measuring a pressure in a pressure space, comprising:
a MEMS substrate,
a carrier substrate bonded to the MEMS substrate in a two-dimensional manner along their longitudinal axis in the form of a rod,
a measuring region with electromechanical measuring means,
a contact-making region with contacts connected via conductors with the measuring region,
wherein in an operating state the measuring region can be exposed to the pressure space, and measured signals can be taken off the electromechanical measuring means, and the measuring region and the contact-making region are spaced apart from one another in the direction of the longitudinal axis by a bushing region,
wherein the MEMS substrate has a blind hole with an open end and a bottom opposite the open end, the bottom of the blind hole forming a membrane in the MEMS substrate, and the membrane is bounded towards the blind hole by an oxide layer, and
a measuring bridge comprising piezoresistive elements is arranged on a side of this membrane which faces away from the open end of the blind hole, and the piezoresistive elements are configured as resistances in the membrane adjacent to the oxide layer,
wherein the MEMS substrate is bonded to the carrier substrate with the open end of the blind hole facing the carrier substrate, such that the carrier substrate forms a bottom wall of a cavity formed in the MEMS chip under the membrane, and
wherein the resistances are embedded in a silicon layer, which is arranged outside the blind hole adjacent to the oxide layer, wherein in each case an oxide layer insulates the resistance from the silicon layer.

18. A measuring element comprising:
a MEMS substrate,
a carrier substrate, wherein the MEMS substrate and the carrier substrate are bonded to one another in a two-dimensional manner along their longitudinal axis in the form of a rod,
a measuring region with electromechanical measuring means,
a contact-making region with contacts connected via conductors with the measuring region,
wherein in an operating state the measuring region can be exposed to the pressure space, and measured signals can be taken off the electromechanical measuring means, and the measuring region and the contact-making region are spaced apart from one another in the direction of the longitudinal axis by a bushing region,
wherein the MEMS substrate has a blind hole with an open end and a bottom opposite the open end, the bottom of which blind hole forms a membrane in the MEMS substrate, and
a measuring bridge comprising piezoresistive elements is arranged on a side of this membrane which faces away from the open end of the blind hole,
wherein the MEMS substrate is bonded to the carrier substrate with the open end of the blind hole facing the carrier substrate, such that the carrier substrate forms a bottom wall of a cavity formed under the membrane, and
a bushing, which is formed by a casting compound and a holding ring, the casting compound being disposed surrounding the bushing region of the MEMS substrate, the holding ring enclosing the casting compound,
wherein the measuring region and the contact-making region protrude from different sides of the holding ring.

19. A pressure sensor comprising:
a MEMS substrate,
a carrier substrate, wherein the MEMS substrate and the carrier substrate are bonded to one another in a two-dimensional manner along their longitudinal axis in the form of a rod,
a measuring region with electromechanical measuring means,
a contact-making region with contacts connected via conductors with the measuring region,
wherein in an operating state the measuring region can be exposed to the pressure space, and measured signals can be taken off the electromechanical measuring means, and the measuring region and the contact-making region are spaced apart from one another in the direction of the lo

Assignees

• Kistler Holding Ag
• Fraunhofer Ges Zur Foerderung Der Angewandten Forschunt E V

Inventors

• Kuehne Stephane
• Cavalloni Claudio
• Goehlich Andreas

Classifications

• G01L19/147 Primary

  Details about the mounting of the sensor to support or covering means · CPC title

• G01L9/005

  Non square semiconductive diaphragm · CPC title

• G01L9/0005

  using variations in capacitance (G01L9/0072 takes precedence) · CPC title

• G01L9/0045

  Diaphragm associated with a buried cavity · CPC title

• G01L19/0627 Primary

  Protection against aggressive medium in general · CPC title