阅读说明：本技术 一种mems压力传感器及其制备方法 (MEMS pressure sensor and preparation method thereof ) 是由 李维平 兰之康 张宇旸 于 2021-12-13 设计创作，主要内容包括：本发明提出一种MEMS压力传感器及其制备方法,包括：衬底,所述衬底包括第一表面及与所述第一表面相对的第二表面；第一压力敏感膜,间隔设置在所述衬底的第一表面上；真空腔,介于所述第一压力敏感膜与所述衬底的第一表面之间；凹槽,设置在所述衬底的第二表面上；第二压力敏感膜,介于所述衬底的第一表面与所述凹槽的底部之间；第一电极,设置在所述第一压力敏感膜的表面；第二电极,设置在所述凹槽的表面。解决现有MEMS压力传感器的电极引出及其引起的可靠性问题并提高传感器的灵敏度。(The invention provides an MEMS pressure sensor and a preparation method thereof, comprising the following steps: a substrate comprising a first surface and a second surface opposite the first surface; the first pressure sensitive film is arranged on the first surface of the substrate at intervals; a vacuum chamber between the first pressure sensitive membrane and the first surface of the substrate; a recess disposed on a second surface of the substrate; a second pressure sensitive membrane interposed between the first surface of the substrate and the bottom of the groove; a first electrode disposed on a surface of the first pressure-sensitive membrane; and the second electrode is arranged on the surface of the groove. The problems of electrode extraction and reliability caused by the electrode extraction of the existing MEMS pressure sensor are solved, and the sensitivity of the sensor is improved.)

1. A MEMS pressure sensor, comprising:

a substrate comprising a first surface and a second surface opposite the first surface;

the first pressure sensitive film is arranged on the first surface of the substrate at intervals;

a vacuum chamber between the first pressure sensitive membrane and the first surface of the substrate;

a recess disposed on a second surface of the substrate;

a second pressure sensitive membrane interposed between the first surface of the substrate and the bottom of the groove;

a first electrode disposed on a surface of the first pressure-sensitive membrane;

and the second electrode is arranged on the surface of the groove.

2. The MEMS pressure sensor of claim 1, wherein the pressure sensitive areas of the first and second pressure sensitive membranes correspond to the vacuum chamber area.

3. The MEMS pressure sensor of claim 1, wherein the first and second pressure sensitive membranes have a thickness of 3-20 μ ι η.

4. The MEMS pressure sensor of claim 1, wherein the vacuum cavity has a height of 0.5-5 μ ι η.

5. The MEMS pressure sensor of claim 1, further comprising an insulating layer interposed between the second electrode and the recess.

6. A preparation method of a MEMS pressure sensor is characterized by comprising the following steps:

selecting a substrate;

depositing a sacrificial layer on the first surface of the substrate;

preparing a first pressure sensitive film on the surface of the sacrificial layer;

etching the sacrificial layer below the pressure sensitive region of the first pressure sensitive membrane;

preparing a first electrode on the upper surface of the first pressure sensitive film;

forming a vacuum cavity below the pressure sensitive area of the first pressure sensitive membrane;

etching a second surface of the substrate opposite to the first surface to form a groove;

the bottom of the groove is provided with a second pressure sensitive film;

and preparing a second electrode on the surface of the groove.

7. The method as claimed in claim 6, wherein the pressure sensitive areas of the first and second pressure sensitive membranes correspond to the vacuum chamber area.

8. The method of claim 6, further comprising forming an insulating layer on a surface of the recess, the insulating layer being interposed between the second electrode and the recess.

9. The method of claim 6, wherein the thickness of the first pressure-sensitive membrane and the second pressure-sensitive membrane is 3-20 μm.

10. The method of claim 6, wherein the vacuum chamber has a height of 0.5-5 μm.

Technical Field

The invention relates to the technical field of micro-electro-mechanical systems (MEMS), in particular to an MEMS pressure sensor and a preparation method thereof.

Background

The pressure sensor is mainly used for measuring environmental pressure, has developed history for many years, is widely applied in the fields of national defense, military, industry, agriculture, medical treatment and the like, and is the most commonly used sensor at present. As an important branch of pressure sensors, MEMS capacitive pressure sensors have the advantages of small temperature drift and easy integration, and are therefore favored. The existing MEMS capacitive pressure sensor generally comprises a fixed electrode, a movable electrode and a cavity, wherein the fixed electrode is disposed in the cavity. Under the action of external pressure, the movable polar plate is bent, so that the distance between the movable polar plate and the fixed polar plate is changed, and the capacitance value is changed. The existing MEMS capacitive sensor is usually processed by a simple bulk process or a surface process. For the existing MEMS capacitive sensor, the fixed electrode is usually sealed in the cavity, and the electrode of the fixed electrode can be led out only by using a plurality of steps of punching, filling, grinding and polishing and the like, so that the preparation process is complex and the reliability is poor. In addition, the sensitivity of the existing MEMS capacitive pressure sensor needs to be further improved to meet the application requirements of more occasions.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problems, the invention provides an MEMS pressure sensor and a preparation method thereof, which are used for solving the problems of electrode extraction and reliability caused by the electrode extraction of the existing MEMS pressure sensor and improving the sensitivity of the sensor.

The technical scheme of the MEMS pressure sensor provided by the invention is as follows:

a MEMS pressure sensor, comprising:

a substrate comprising a first surface and a second surface opposite the first surface;

the first pressure sensitive film is arranged on the first surface of the substrate at intervals;

a vacuum chamber between the first pressure sensitive membrane and the first surface of the substrate;

a recess disposed on a second surface of the substrate;

a second pressure sensitive membrane interposed between the first surface of the substrate and the bottom of the groove;

a first electrode disposed on a surface of the first pressure-sensitive membrane;

and the second electrode is arranged on the surface of the groove.

Further, the pressure sensitive regions of the first and second pressure sensitive films correspond to the vacuum chamber region.

Further, the thickness of the first pressure sensitive film and the second pressure sensitive film is 3-20 μm.

Further, the height of the vacuum chamber is 0.5-5 μm.

Further, the device also comprises an insulating layer, wherein the insulating layer is arranged between the second electrode and the groove.

The invention also provides a preparation method of the MEMS pressure sensor, which comprises the following steps:

selecting a substrate;

depositing a sacrificial layer on the first surface of the substrate;

preparing a first pressure sensitive film on the surface of the sacrificial layer;

etching the sacrificial layer below the pressure sensitive region of the first pressure sensitive membrane;

preparing a first electrode on the upper surface of the first pressure sensitive film;

forming a vacuum cavity below the pressure sensitive area of the first pressure sensitive membrane;

etching a second surface of the substrate opposite to the first surface to form a groove;

the bottom of the groove is provided with a second pressure sensitive film;

and preparing a second electrode on the surface of the groove.

Further, the pressure sensitive regions of the first and second pressure sensitive films correspond to the vacuum chamber region.

Further, the method also comprises the step of preparing an insulating layer on the surface of the groove, wherein the insulating layer is arranged between the second electrode and the groove.

Further, the thickness of the first pressure sensitive film and the second pressure sensitive film is 3-20 μm.

Further, the height of the vacuum chamber is 0.5-5 μm.

Has the advantages that: compared with the prior art, the invention has the following advantages:

1. the two electrodes of the MEMS pressure sensor are both positioned on the outer surface of the substrate, and the problems of difficult electrode leading-out and reliability caused by the difficulty of sealing the fixed electrode in the cavity of the existing MEMS pressure sensor do not exist, so the sensor has the advantages of simple preparation process, low cost and high reliability.

2. Compared with the prior MEMS capacitive pressure sensor which only has one movable electrode, the sensor provided by the invention has two movable electrodes, and both the two electrodes can deform under the action of external pressure, so that the distance between the electrodes and the capacitance value change amount are larger under the same pressure action, and the sensor provided by the invention has higher sensitivity.

3. The MEMS pressure sensor can be prepared by adopting an MEMS processing technology with high precision, high consistency, large batch and low cost.

Drawings

FIG. 1 is a schematic cross-sectional view of a MEMS pressure sensor in accordance with an embodiment of the present invention;

fig. 2-8 are schematic views of a process for manufacturing a MEMS pressure sensor according to an embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, it will be appreciated by those of ordinary skill in the art that numerous technical details are set forth in order to provide a better understanding of the present application in various embodiments of the present invention. However, the technical solution claimed in the present application can be implemented without these technical details and various changes and modifications based on the following embodiments. The following embodiments are divided for convenience of description, and should not constitute any limitation to the specific implementation manner of the present invention, and the embodiments may be mutually incorporated and referred to without contradiction.

Example 1

The present embodiment provides a MEMS pressure sensor, as shown in fig. 1, including:

a substrate 2; the substrate 2 may be a substrate commonly used in the semiconductor field, such as single crystal silicon or glass, with a thickness of 200-2000 μm.

The substrate 2 includes a first surface and a second surface opposite to the first surface.

A first pressure sensitive film 1 arranged on a first surface of the substrate 2 at intervals; the spacing arrangement of the present embodiment is, for example, a spacing space formed by the first pressure-sensitive membrane 1 and the substrate 2 after etching through the support layer 9.

The support layer 9 may be a layer separately provided, or may be formed integrally with the first pressure-sensitive membrane 1.

The material of the first pressure sensitive membrane 1 and the support layer 9 may be the same, for example both being polysilicon.

And an etching hole 10 provided on the first pressure-sensitive film 1 and penetrating the first pressure-sensitive film 1 in the thickness direction.

A vacuum chamber 3 disposed between the first pressure-sensitive film 1 and the first surface of the substrate 2; the vacuum chamber 3 is formed by, for example, removing the sacrificial layer 11 thereunder by etching the etching hole 10 in the first pressure-sensitive film 1 and then closing the etching hole 10.

A groove 8 disposed on the second surface of the substrate 2; the recess 8 is formed, for example, by bulk processing, photolithography, and etching of the second surface of the substrate 2 to a predetermined depth.

A second pressure sensitive membrane 5 interposed between the first surface of the substrate and the bottom of the groove; i.e. the second pressure sensitive membrane 5 is the remaining part of the groove bottom substrate 2 after etching the substrate 2 to form the groove 8.

The first electrode 4 is arranged on the surface of the first pressure sensitive film, the first electrode 4 is formed by sputtering a layer of Al with the thickness of 3 microns on the upper surface of the first pressure sensitive film 1 by magnetron sputtering, for example, in a vacuum environment, and meanwhile, the Al layer can also seal a sacrificial layer corrosion hole 10 on the first pressure sensitive film 1;

a second electrode 7 arranged on the surface of the groove; the second electrode 7 may be prepared using the same process as the first electrode 4.

Further, if the substrate is monocrystalline silicon, for the purpose of electrical isolation between the second electrode 7 and the substrate 2, an insulating layer 6 disposed on the second surface of the substrate 2 is further included, the insulating layer 6 covers the groove 8, and the material of the insulating layer 6 is at least one of silicon dioxide or silicon nitride; the thickness is 100-1000 nm.

Further, the first pressure sensitive film 1 is disposed in a central region of the first surface of the substrate 2, and the pressure sensitive region of the first pressure sensitive film 1 and the pressure sensitive region of the second pressure sensitive film correspond to the vacuum chamber region.

Furthermore, the first pressure sensitive film 1 is prepared by adopting a surface process, the second pressure sensitive film 5 is formed by etching the substrate 2 by adopting a bulk process, and the thicknesses of the first pressure sensitive film 1 and the second pressure sensitive film 5 are 3-20 μm; the height of the vacuum chamber 3 is 0.5-5 μm. In this way, the pressure-sensitive membrane is ensured to have good mechanical strength, and the distance between the first electrode 4 and the second electrode 7 is ensured to be small enough, which is beneficial to improving the capacitance value and the sensitivity of the MEMS pressure sensor.

Furthermore, the material of the first electrode 4 and the second electrode 7 is metal, preferably at least one of Al, Ti, Au, Cu and Pt, and the thickness is 50-500 nm.

The working principle of the MEMS pressure sensor provided by the invention is as follows:

the first electrode 4 and the second electrode 7 form two electrodes of the MEMS pressure sensor, and both the two electrodes are movable electrodes, that is, under the action of external pressure, both the first electrode 4 and the second electrode 7 can be bent. Specifically, under the action of external pressure, the first pressure-sensitive membrane 1 bends downward and drives the first electrode 4 to also bend downward, and the second pressure-sensitive membrane 5 bends upward and drives the second electrode 7 to also bend upward, so that the distance between the two electrodes changes, and further the capacitance value changes, and the larger the external pressure is, the larger the bending degree of the first pressure-sensitive membrane 1 and the second pressure-sensitive membrane 5 is, the larger the corresponding capacitance value is, so that a pressure signal is converted into an electric signal, and the pressure measurement is realized.

Example 2

Referring to fig. 2 to 8, the present embodiment proposes a method for manufacturing the MEMS pressure sensor proposed in embodiment 1, wherein a support layer is integrally formed with a first pressure-sensitive membrane 1. The method comprises the following steps:

selecting a substrate 2; selecting an N-type (100) silicon wafer with the thickness of 500 mu m as a substrate 2;

depositing a sacrificial layer on the first surface of the substrate; as shown in FIG. 2, first, a surface process was used to prepare SiO with a thickness of about 3 μm on the front surface of a silicon wafer by PECVD (Plasma Enhanced Chemical Vapor Deposition) and photolithography₂A sacrificial layer.

Preparing a first pressure sensitive film on the surface of the sacrificial layer; as shown in fig. 3, a support layer 9 is formed by preparing polysilicon of about 3 μm thickness on the front surface of the silicon wafer by LPCVD (Low Pressure Chemical Vapor Deposition).

Etching the sacrificial layer below the pressure sensitive region of the first pressure sensitive membrane; as shown in fig. 4, Etching holes 10 are formed by Etching the polysilicon on the front surface of the silicon wafer by photolithography and RIE (Reactive Ion Etching), and then Etching the sacrificial layer to obtain a polysilicon first pressure sensitive film 1 with a thickness of 3 μm.

Preparing a first electrode on the upper surface of the first pressure sensitive film 1;

forming a vacuum cavity below the pressure sensitive area of the first pressure sensitive membrane 1; as shown in fig. 5, a layer of Al with a thickness of about 3 μm is sputtered on the upper surface of the first pressure-sensitive film 1 as the first electrode 4 by magnetron sputtering in a vacuum environment, and the sacrificial layer etching hole 10 on the first pressure-sensitive film 1 is sealed at the same time, so that the vacuum chamber 3 is obtained.

Etching a second surface of the substrate opposite to the first surface to form a groove; as shown in fig. 6, a recess 8 is obtained by using a bulk process and etching the back surface of the silicon wafer by photolithography and a KOH wet process. Wherein the substrate membrane between the bottom area of the recess and the first surface of the substrate acts as a second pressure sensitive membrane 5.

As shown in FIG. 7, in order to electrically isolate the substrate 2, a layer of SiO with a thickness of about 500nm is deposited on the lower surface of the substrate 2 by PECVD₂As the insulating layer 6.

And preparing a second electrode on the surface of the groove. As shown in fig. 8, Al with a thickness of 100nm was prepared on the lower surface of the insulating layer 6 by magnetron sputtering, the second electrode 7 was formed, and the preparation of the device was completed.

Has the advantages that: compared with the prior art, the invention has the following advantages:

1. the two electrodes of the MEMS pressure sensor are both positioned on the outer surface of the substrate, and the problems of difficult electrode leading-out and reliability caused by the difficulty of sealing the fixed electrode in the cavity of the existing MEMS pressure sensor do not exist, so the sensor has the advantages of simple preparation process, low cost and high reliability.

2. Compared with the prior MEMS capacitive pressure sensor which only has one movable electrode, the sensor provided by the invention has two movable electrodes, and both the two electrodes can deform under the action of external pressure, so that the distance between the electrodes and the capacitance value change amount are larger under the same pressure action, and the sensor provided by the invention has higher sensitivity.

3. The MEMS pressure sensor can be prepared by adopting an MEMS processing technology with high precision, high consistency, large batch and low cost.

The above description is only a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above embodiment, but equivalent modifications or changes made by those skilled in the art according to the present disclosure should be included in the scope of the present invention as set forth in the appended claims.