WO2022247277A1

WO2022247277A1 - Mems differential pressure sensor and manufacturing method therefor

Info

Publication number: WO2022247277A1
Application number: PCT/CN2021/143207
Authority: WO
Inventors: 陈磊; 朱恩成; 张强; 闫文明
Original assignee: 歌尔微电子股份有限公司
Priority date: 2021-05-25
Filing date: 2021-12-30
Publication date: 2022-12-01
Also published as: CN113432778A; CN113432778B

Abstract

A MEMS differential pressure sensor and a manufacturing method therefor. The MEMS differential pressure sensor comprises: a base layer (1) having a cavity (5); a pressure sensitive film (4) erected above the cavity (5) of the base layer (1); and a protective housing (3) arranged on the side of the pressure sensitive film (4) that is away from the base layer (1). In a static state, a vertical distance between the pressure sensitive film (4) and the bottom of the cavity (5), and between the pressure sensitive film (4) and the protective housing (3) is less than the minimum overload deformation amount of the pressure sensitive film (4); and limiting structures, for limiting two sides of the pressure sensitive film (4), are respectively formed by the bottom of the cavity (5) and the protective housing (3). Bidirectional high-overload resistance of the MEMS differential pressure sensor can thus be achieved, and the sensor is stable in performance and small in size.

Description

MEMS differential pressure sensor and manufacturing method thereof

This application claims the priority of the patent application whose application number is 202110572090.1 and the application date is May 25, 2021, and the invention name is "MEMS differential pressure sensor and its manufacturing method".

technical field

The present application relates to the technical field of sensors, and more specifically, to a MEMS differential pressure sensor and a manufacturing method thereof.

Background technique

With the progress of society and the development of technology, in recent years, the volume of electronic products such as mobile phones and notebook computers has been continuously reduced, and people's requirements for the performance of these portable electronic products are also getting higher and higher. The size continues to decrease, and the performance and consistency continue to increase. MEMS (Micro-Electro-Mechanical-System, MEMS for short) process-integrated MEMS sensors have begun to be applied in batches to electronic products such as mobile phones and notebook computers. Their packaging volume is smaller than traditional sensors, so they are favored by most manufacturers.

At present, the manufacturing process of piezoresistive MEMS differential pressure chips on the market mostly adopts wet etching in chemical etching to form a cavity structure. However, the silicon cavity after wet etching will form due to the anisotropy of material corrosion. An inclination angle, in the case of meeting the requirements of the through hole, will lead to a larger overall size of this type of MEMS differential pressure chip; in addition, in the actual application process, such pressure sensors often have over-range or high overload situations, The pressure-sensitive membrane of most piezoresistive MEMS differential pressure chips will have cracks, membrane rupture and other failure problems.

It can be seen that the existing MEMS differential pressure sensor has problems such as large size and low overload resistance, resulting in unstable product performance and low reliability.

Contents of the invention

In view of the above problems, the purpose of this application is to provide a MEMS differential pressure sensor and its manufacturing method to solve the problems of unstable product performance and low reliability caused by the large size and poor overload resistance of existing sensors.

The MEMS differential pressure sensor provided by the application includes a base layer with a cavity, a pressure sensitive membrane erected on the cavity of the base layer, and a protective shell arranged on the side of the pressure sensitive membrane away from the base layer; wherein, at rest In this state, the vertical distances between the pressure-sensitive membrane and the bottom of the chamber and the protective shell are smaller than the minimum overload deformation of the pressure-sensitive membrane; The limiting structure of the limit.

In addition, an optional technical solution is that an upper through hole is provided on the protective shell, and a lower through hole penetrating through the base layer is provided at the bottom of the cavity; and the longitudinal section of the lower through hole is in a trapezoidal or trumpet-shaped structure; The opening size of the through hole on the side away from the pressure sensitive membrane is larger than the opening size of the lower through hole at the bottom of the cavity.

In addition, an optional technical solution is that when the pressure sensitive membrane is deformed to contact with the bottom of the cavity, the deformation of the pressure sensitive membrane is smaller than the minimum overload deformation of the pressure sensitive membrane.

In addition, an optional technical solution is that, in the direction perpendicular to the pressure-sensitive membrane, the arrangement positions of the upper through holes and the central position of the pressure-sensitive membrane are alternately distributed.

In addition, an optional technical solution is that when the pressure sensitive membrane is deformed to contact with the protective shell, the deformation of the pressure sensitive membrane is smaller than the minimum overload deformation of the pressure sensitive membrane.

In addition, an optional technical solution is that, in the direction perpendicular to the pressure sensitive membrane, the positions of the lower through holes and the upper through holes are distributed alternately.

In addition, an optional technical solution is that the pressure-sensitive film includes an insulating layer, a silicon film disposed on the insulating layer, and at least one strain resistance disposed on the silicon film and an electrical connection structure connected to the strain resistance; The structure includes a heavily doped region connected with the strain resistance and a welding pad arranged on the heavily doped region.

In addition, an optional technical solution is that the opening position of the upper through hole corresponds to the setting position of the pad; the pad is packaged and wired through the upper through hole.

According to another aspect of the present application, a method for manufacturing a MEMS differential pressure sensor is provided, including: disposing an insulating layer on the silicon film to form a pressure sensitive film; bonding the insulating layer side of the pressure sensitive film to a silicon substrate with a cavity above; bond the protective shell formed by the etching process on the silicon film side of the pressure sensitive film; chemically etch the silicon substrate to form a bottom cavity on the silicon substrate; dry etch the bottom cavity to form A via hole that communicates with the cavity.

In addition, an optional technical solution is, before chemically etching the silicon substrate, further comprising: performing electrochemical deposition on the silicon substrate to form a hard mask attached to the bottom of the silicon substrate.

Utilizing the above-mentioned MEMS differential pressure sensor and its manufacturing method, in a static state, the vertical distances between the pressure-sensitive membrane and the bottom of the cavity and between the protective shell are smaller than the minimum overload deformation of the pressure-sensitive membrane, and the pressure-sensitive membrane can pass through the cavity The bottom of the bottom and the protective shell respectively form a limit structure to limit the two sides of the pressure sensitive membrane, which can effectively protect the pressure sensitive membrane and prevent the occurrence of high overload; The body conduction through hole can reduce the occupied size of the lower through hole, which is beneficial to the development of miniaturization of the sensor.

In order to achieve the above and related objects, one or more aspects of the present application include features that will be described in detail later. The following description and accompanying drawings detail certain exemplary aspects of the present application. These aspects are indicative, however, of but a few of the various ways in which the principles of the present application may be employed. Furthermore, this application is intended to cover all such aspects and their equivalents.

Description of drawings

By referring to the following descriptions in conjunction with the accompanying drawings, and with a more comprehensive understanding of the application, other objectives and results of the application will become clearer and easier to understand. In the attached picture:

1 is a schematic diagram of the overall structure of a MEMS differential pressure sensor according to an embodiment of the present application;

Fig. 2 is the flow chart of the manufacturing method of MEMS differential pressure sensor according to the embodiment of the application;

3 is a schematic diagram of a specific structure of a MEMS differential pressure sensor according to an embodiment of the present application;

Fig. 4 is a specific structural schematic diagram II of a MEMS differential pressure sensor according to an embodiment of the present application;

FIG. 5 is a schematic diagram of a specific structure of a MEMS differential pressure sensor according to an embodiment of the present application.

6 is a schematic diagram 4 of a specific structure of a MEMS differential pressure sensor according to an embodiment of the present application;

FIG. 7 is a fifth schematic structural diagram of a MEMS differential pressure sensor according to an embodiment of the present application.

The reference signs include: base layer 1, lower through hole 2, protective shell 3, upper through hole 31, pressure sensitive film 4, silicon film 41, insulating layer 42, cavity 5, pad 6, heavily doped region 7. Strain resistors 8 , bottom cavities 9 , and hard masks 10 .

The same reference numerals indicate similar or corresponding features or functions throughout the drawings.

Detailed ways

In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It is evident, however, that these embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing one or more embodiments.

In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " Back", "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom", "Inner", "Outer", "Clockwise", "Counterclockwise", "Axial", The orientation or positional relationship indicated by "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the application and simplifying the description, rather than indicating or implying the referred device or element Must be in a particular orientation, constructed, and operate in a particular orientation, and thus should not be construed as limiting of the application.

In order to describe the MEMS differential pressure sensor of the present application and its manufacturing method in detail, specific embodiments of the present application will be described in detail below in conjunction with the accompanying drawings.

FIG. 1 shows a schematic structure of a MEMS differential pressure sensor according to an embodiment of the present application.

As shown in Figure 1, the MEMS differential pressure sensor according to the embodiment of the present application includes a base layer 1 with a cavity 5, a pressure sensitive membrane 4 arranged on the base layer 1 and erected on the cavity 5, and a The protective shell 3 on the side where the pressure-sensitive film 4 is far away from the base layer 1; wherein, in a static state or when the pressure-sensitive film is not subjected to external force, a certain distance is maintained between the protective shell 3 and the pressure-sensitive film 4, and the pressure-sensitive The vertical distances between the membrane 4 and the bottom of the cavity 5 and the protective shell 3 are smaller than the minimum overload deformation of the pressure sensitive membrane 4, and the pressure sensitive membrane 4 is formed through the bottom of the cavity 5 and the protective shell 3 respectively. The position-limiting structure on both sides of the pressure-sensitive membrane 4 can be limited by the cavity 5 and the protective shell 3 when the pressure-sensitive membrane 4 is deformed by an external force, so as to prevent the pressure-sensitive membrane 4 from breaking and failing.

Wherein, in order to form an air pressure difference on both sides of the pressure sensitive membrane 4, an upper through hole 31 needs to be set on the protective case 3, and a lower through hole 2 penetrating through the base layer 1 is set at the bottom of the cavity 5; and, the lower through hole 2. On the longitudinal section perpendicular to the pressure sensitive membrane 4, it has a trapezoidal, trumpet-shaped or funnel-shaped structure, and the opening size of the lower through hole 2 on the side away from the pressure sensitive membrane 4 is larger than that of the lower through hole 2 in the cavity 5 The opening size of the bottom, the two sides of the pressure sensitive membrane 4 contact the outside world through the upper through hole 31 and the lower through hole 2, and detect the air pressure difference on both sides, so as to achieve the detection effect of the MEMS differential pressure sensor.

In a specific embodiment of the present application, when the pressure-sensitive membrane 4 is in a static state, the vertical distance between the upper side of the pressure-sensitive membrane 4 and the protective case 3 can be set as the minimum overload deformation of the pressure-sensitive membrane 4 range, and then when the pressure sensitive membrane 4 is deformed to contact with the inner side of the protective shell 3, the deformation of the pressure sensitive membrane 4 is less than the minimum overload deformation of the pressure sensitive membrane 4, preventing excessive deformation of the pressure sensitive membrane 4, and Limit protection on one side.

Correspondingly, when the pressure sensitive membrane 4 is in a static state, the vertical distance between the underside of the pressure sensitive membrane 4 and the bottom of the cavity 5 can be set within the minimum overload deformation range of the pressure sensitive membrane 4, and then when the pressure When the sensitive membrane 4 is deformed to be in contact with the bottom of the cavity 5, the deformation of the pressure sensitive membrane 4 is less than the minimum overload deformation of the pressure sensitive membrane 4, preventing excessive deformation of the pressure sensitive membrane 4, and protecting the other side. Limit protection.

In order to prevent the adverse effect caused by airflow hedging on the pressure sensitive membrane 4, in the MEMS differential pressure sensor of the present application, in the direction perpendicular to the pressure sensitive membrane 4, the position of the upper through hole 31 and the center position of the pressure sensitive membrane 4 can be set to interleave with each other. Or, the position of the upper through hole 31 and the position of the upper through hole 31 can be arranged to be alternately distributed, and the lower through hole 2 can be arranged below the center position of the pressure sensitive membrane 4, and can also be aligned with the center of the pressure sensitive membrane 4. The positions are staggered to ensure that the depth of the cavity 5 and the height of the protective shell 3 can protect both sides of the pressure sensitive membrane 4 from overload and deformation.

In addition, the size of the lower through hole 2 can be adjusted according to the overall structure or requirements of the product. If the lower through hole 2 is too small, the airflow is difficult to pass through, which will easily affect the detection accuracy of the MEMS differential pressure sensor. If the size of the lower through hole 2 is too large, Then when it is arranged below the central position of the pressure sensitive membrane 4, the downward deformation of the pressure sensitive membrane 4 will avoid in the lower through hole 2, and then it will not be able to form an effective limiting structure through the bottom of the cavity 5. Therefore, the setting position and size of the lower through hole 2 can be adjusted, and is not limited to the specific structure shown in the drawings.

It should be noted that, in the process of forming the lower through hole 2, in order to prevent problems such as the large opening size of the lower through hole 2 caused by traditional wet etching, which is not conducive to the development of product miniaturization, in this application, In a specific embodiment, firstly, a combination of wet and dry etching can be used to form a bottom cavity on the base layer 1 by wet etching, and the bottom cavity can be controlled by controlling the etching speed and time, etc. area, and then form the lower through-hole 2 connected to the cavity 5 in the bottom cavity by dry etching, which can reduce the space occupied by the lower through-hole 2 on the base layer 1, thereby reducing the overall product size. size effect.

In a specific embodiment of the present application, the pressure-sensitive film 4 may include an insulating layer, a silicon film disposed on the insulating layer, and at least one strain resistance 8 disposed on the silicon film and an electrical connection connected to the strain resistance 8. Connection structure; wherein, the electrical connection structure includes a heavily doped region 7 connected to the strain resistance 8 and a pad 6 arranged on the heavily doped region 7, and the MEMS differential pressure sensor is connected to an external circuit through the pad 6 to achieve The role of transmitting signals.

It can be seen that in order to ensure that the position of the pad 6 is convenient for later packaging and wiring, the opening position of the upper through hole 31 can be set to correspond to the position of the pad 6, so that the pad 6 can be facilitated while conducting the airflow. The encapsulation and wire bonding operation is performed through the upper through hole 31 . In addition, the setting size of the upper through hole 31 can also be set and adjusted according to specific product requirements and overall size.

Corresponding to the above-mentioned MEMS differential pressure sensor, the present application also provides a manufacturing method of the MEMS differential pressure sensor. Specifically, FIG. 2 shows a schematic flowchart of a method for manufacturing a MEMS differential pressure sensor according to an embodiment of the present application.

As shown in Figure 2, the manufacturing method of the MEMS differential pressure sensor of the embodiment of the present application includes:

S110: disposing an insulating layer on the silicon film to form a pressure sensitive film;

S120: bonding the insulating layer side of the pressure sensitive film on the silicon substrate with a cavity;

S130: bonding the protective shell formed by the etching process on the silicon membrane side of the pressure sensitive membrane;

S140: performing chemical etching on the silicon substrate to form a bottom cavity on the silicon substrate;

S150: performing dry etching on the cavity at the bottom to form a through hole connected to the cavity.

As an example, the above manufacturing method will be described in detail below in conjunction with specific drawings.

First, as shown in the partial schematic structure in the manufacturing process of the MEMS differential pressure sensor according to the embodiment of the invention in Fig. 3, a silicon substrate (or base layer 1, the same below) with a cavity 5 and a pressure sensitive film, and bond the pressure-sensitive film on the silicon substrate to form the structure shown in Figure 2. In this process, the cavity 5 on the silicon substrate can be formed by a conventional etching process, and the pressure-sensitive film can be formed by setting an insulating layer 42 on the basis of the silicon film 41. In the bonding process, the insulating layer of the pressure-sensitive film Layer 42 is bonded to the silicon substrate on one side.

Then, as shown in the partial schematic structure in the manufacturing process of the MEMS differential pressure sensor according to the embodiment of the invention in FIG. The heavily doped region 7 is further formed with a pad 6 structure on the heavily doped region 7 through a metal deposition process, and the pad 6 and the heavily doped region 7 form an electrical connection structure. In this process, the lightly doped region and the heavily doped region 7 can be provided in multiple places, and are not limited to the two specific structures shown in FIG. 3 .

Secondly, a protective shell can be set on the silicon membrane, and the vertical distance between the inner side of the protective shell and the pressure-sensitive membrane is guaranteed to be within the minimum overload deformation range of the pressure-sensitive membrane, and then the protective shell plays the role of overload limit protection . In this process, the protective shell can be made of silicon material, which is etched into a cover-like structure through wet or dry etching process in advance, and then the surrounding side walls of the protective shell are directly bonded to the silicon film or silicon film through the bonding process. The base is combined.

Again, as shown in the partial schematic structure in the manufacturing process of the MEMS differential pressure sensor according to the embodiment of the invention in FIG. The bottom cavity 9 is not connected to the cavity 8 on the upper side of the silicon substrate. In this process, the size of the bottom cavity 9 can be controlled by controlling parameters such as the rate and time of chemical etching. In addition, since the chemical etching requires relatively low precision, a wet etching process can be used.

Then, as shown in FIG. 6 according to the partial schematic structure in the manufacturing process of the MEMS differential pressure sensor according to the embodiment of the invention, on the basis of the structure in FIG. The lower through hole 2 that is connected to the cavity, at this time, due to the dry etching, it can be etched until it is connected to the cavity without enlarging the maximum opening size of the lower through hole 2, which can be applied In the structure of differential pressure sensor with small overall size.

During this process, the insulating layer on the underside of the silicon film acts as an etch stop, preventing damage to the scale above it. Wherein, the insulating layer may use materials such as silicon oxide.

Finally, as shown in Figure 7 according to the partial schematic structure of the MEMS differential pressure sensor in the manufacturing process of the embodiment of the invention, the upper through hole 31 is formed on the protective shell 3 through a dry etching process such as RIE, so that the pressure sensitive film The pad area is exposed, which is convenient for subsequent packaging and wiring.

It should be noted that, in the manufacturing method of the MEMS differential pressure sensor of the present application, before chemically etching the silicon substrate, it also includes: electrochemically depositing the silicon substrate to form a hard mask attached to the bottom of the silicon substrate 10, and then chemically etch the hard mask 10 and the silicon substrate to form a bottom cavity. Wherein, the hard mask 10 can be made of silicon oxide, silicon nitride and other materials.

In addition, the step of forming the upper through hole on the protective shell can also directly form the upper through hole on the protective shell while forming the protective shell, but in this case, the position of the pad needs to be determined in advance, if the position of the pad The change is small, and the upper through-hole structure can be directly formed while the protective shell is formed according to experience, and there is no need to etch the upper through-hole after the lower through-hole is formed.

In the same way, the steps of installing the protective case on the silicon film and the step of etching the through hole on the silicon substrate can be processed separately regardless of the front and rear. The protective case can be installed first, or the through hole can be etched first and then the protective film can be installed. Shell, etc., are not particularly limited to the above steps.

In addition, for the embodiment of the manufacturing method of the MEMS differential pressure sensor of the present application, reference may be made to the description in the embodiment of the MEMS differential pressure sensor device. The bottom of the body achieves the effect of bidirectional anti-high overload, and can be applied to sensors with small size requirements.

Utilize above-mentioned MEMS differential pressure sensor and manufacturing method thereof according to the present application, set the vertical distance between the pressure-sensitive membrane and the bottom of the cavity and between it and the protective shell to be less than the minimum overload deformation of the pressure-sensitive membrane, can The bottom of the cavity and the protective shell respectively form a limiting structure for limiting the two sides of the pressure-sensitive membrane, thereby effectively preventing the failure caused by the transitional deformation of the pressure-sensitive membrane; in addition, dry etching is used to form a The through hole connected to the cavity can reduce the occupied size of the lower through hole, and can be applied to sensors with small size requirements, and the performance of the sensor is reliable and stable.

The MEMS differential pressure sensor and its manufacturing method according to the present application are described above by way of example with reference to the accompanying drawings. However, those skilled in the art should understand that various improvements can be made to the above-mentioned MEMS differential pressure sensor and its manufacturing method proposed in this application without departing from the contents of this application. Therefore, the protection scope of this application should be determined by the contents of the appended claims.

Claims

A MEMS differential pressure sensor, characterized in that it includes a base layer with a cavity, a pressure sensitive membrane erected on the cavity of the base layer, and is arranged on the side of the pressure sensitive membrane away from the base layer protective shell; among them,

In a static state, the vertical distances between the pressure sensitive membrane and the bottom of the cavity and the protective shell are smaller than the minimum overload deformation of the pressure sensitive membrane;

The bottom of the cavity and the protective shell respectively form a limiting structure for limiting the two sides of the pressure sensitive membrane.
MEMS differential pressure sensor as claimed in claim 1, is characterized in that,

An upper through hole is provided on the protective shell, and a lower through hole penetrating through the base layer is provided at the bottom of the cavity; and,

The longitudinal section of the lower through hole is trapezoidal or trumpet-shaped;

The opening size of the lower through hole on the side away from the pressure sensitive membrane is larger than the opening size of the lower through hole at the bottom of the cavity.
MEMS differential pressure sensor as claimed in claim 1, is characterized in that,

When the pressure sensitive membrane is deformed to be in contact with the bottom of the cavity, the deformation amount of the pressure sensitive membrane is smaller than the minimum overload deformation amount of the pressure sensitive membrane.
MEMS differential pressure sensor as claimed in claim 2, is characterized in that,

In a direction perpendicular to the pressure sensitive membrane, the positions of the upper through holes and the central position of the pressure sensitive membrane are distributed alternately.
MEMS differential pressure sensor as claimed in claim 1, is characterized in that,

When the pressure sensitive membrane is deformed to be in contact with the protective shell, the deformation amount of the pressure sensitive membrane is smaller than the minimum overload deformation amount of the pressure sensitive membrane.
MEMS differential pressure sensor as claimed in claim 2, is characterized in that,

In a direction perpendicular to the pressure sensitive membrane, the positions of the lower through holes and the upper through holes are distributed alternately.
MEMS differential pressure sensor as claimed in claim 2, is characterized in that,

The pressure-sensitive film includes an insulating layer, a silicon film disposed on the insulating layer, and at least one strain resistance disposed on the silicon film and an electrical connection structure conducting with the strain resistance;

The electrical connection structure includes a heavily doped region connected to the strain resistance and a pad disposed on the heavily doped region.
MEMS differential pressure sensor as claimed in claim 7, is characterized in that,

The opening position of the upper through hole corresponds to the setting position of the pad;

The bonding pad is packaged and wired through the upper through hole.
A method for manufacturing a MEMS differential pressure sensor, characterized in that it comprises:

An insulating layer is set on the silicon film to form a pressure-sensitive film;

bonding the insulating layer side of the pressure sensitive film on the silicon substrate having a cavity;

bonding a protective shell formed by an etching process on the silicon membrane side of the pressure sensitive membrane;

chemically etching the silicon substrate to form a bottom cavity on the silicon substrate;

Dry etching is performed on the cavity at the bottom to form a through hole that communicates with the cavity.
The manufacturing method of MEMS differential pressure sensor as claimed in claim 9, is characterized in that, before carrying out chemical etching to described silicon base, also comprises:

Electrochemical deposition is performed on the silicon substrate to form a hard mask attached to the bottom of the silicon substrate.