CN105000529B - Pressure sensor chip based on MEMS (Micro Electro Mechanical System) technology and manufacturing method thereof - Google Patents

Abstract

The invention relates to a pressure sensor chip of various pressure forms based on MEMS (Micro Electro Mechanical System) technology and a manufacturing method thereof. In the manufacturing process of the pressure sensor chip, the product range is determined by means of a surface micromechanical machining process, and whether subsequent procedures are needed or not can be selected with the same surface process in order to manufacture pressure sensor chips of sealing gauge pressures, gauge pressures and absolute pressures respectively. For a large-range product, the chip size can be up to 0.6mm. A piezoresistor is a polysilicon resistor with low temperature drift and high temperature resistance. Mass blocks are designed on sensitive films, so that the phenomenon of release adhesion can be prevented, and meanwhile the overload capability of the pressure sensor can be enhanced. The mass blocks are positioned in the stress matching area of the piezoresistor, so that the sensitivity and linearity of the pressure sensor can be enhanced. The pressure sensor chip based on the MEMS technology related to the invention is simple in process, small in chip size, low in cost and high in production efficiency, temperature characteristic and static puncture resistance, and can be applied to various high temperature resistance fields.

Description

A pressure sensor chip based on MEMS technology and its preparation method

technical field

The invention relates to the fields of MEMS design and semiconductor processing, in particular to a multi-pressure form pressure sensor chip based on MEMS technology and a preparation method thereof.

Background technique

The "2014-2019 China Sensor Market In-Depth Survey and Investment Prospect Evaluation Consulting Report" released by China Industry Information Network pointed out that in recent years, the global sensor market has maintained rapid growth, and the growth rate in 2009 and 2010 reached more than 20%. Affected by the global economic downturn, the growth rate of the sensor market fell by 5% compared with 2010, and the market size was 82.8 billion US dollars. With the gradual recovery of the global market, the global sensor market reached USD 95.2 billion in 2012 and approximately USD 105.5 billion in 2013. In the future, as the economic environment continues to improve, the market demand for sensors will continue to increase. It is predicted that the global sensor market will maintain a growth rate of more than 20% in the next few years, and the market size will exceed 150 billion US dollars in 2015. At present, flow sensors, pressure sensors, and temperature sensors have the largest market size, among which pressure sensors account for about 18% of the market share.

Silicon piezoresistive pressure sensor is a kind of pressure sensor. At present, most silicon piezoresistive pressure sensors are prepared by MEMS body micromachining technology, that is, on the surface of silicon wafer through oxidation, photolithography, ion implantation and other planar IC processes. After the pressure-sensitive resistors and metal interconnection leads are produced, anisotropic wet etching is performed from the back of the silicon wafer. The thickness of the pressure-sensitive film is controlled by adjusting the etching rate and time. After the etching is completed, glass is used for bonding. supporting structure. The thickness uniformity of the pressure sensitive film of the pressure sensor prepared by the above process is poor, the chip volume is large, the yield is low, the performance is unstable, and the cost is high.

The pressure sensor involved in the present invention is prepared by surface micro-machining technology, which can avoid deep etching of bulk silicon and can prepare a sealed gauge pressure sensor chip. In addition, ICP and silicon-glass bonding technology can realize gauge pressure and insulation on the same design. The preparation of the pressure chip; the polysilicon deposited by LPCVD is used as the piezoresistor, which can increase the working temperature range. The technology of the pressure sensor involved in the present invention is simpler to implement, is beneficial to the integration of the sensor and the subsequent signal detection circuit, realizes electromechanical integration, and helps reduce the cost of the sensor.

Contents of the invention

The invention provides a multi-pressure form pressure sensor chip based on MEMS technology and a preparation method thereof. The same set of layouts can realize the preparation of three pressure forms of sealed gauge pressure, gauge pressure and absolute pressure at the same time; The film thickness matching and annealing treatment can reduce the residual stress of the pressure sensitive film; the quality block is prepared on the sensitive film to prevent the release adhesion phenomenon, and improve the overload capacity and linearity of the sensor; the polysilicon resistance is made on the top layer of silicon nitride of the composite film , Silicon nitride can play the role of shielding charged ions, and form an SOI structure, which improves the operating temperature range of the chip.

Specifically, the technical scheme of the present invention is as follows:

A kind of pressure sensor chip based on MEMS technology, it is characterized in that: comprise multi-layer pressure-sensitive film, form the piezoresistor 11 above this multi-layer pressure-sensitive film, described piezoresistor 11 forms Wheatstone bridge structure; The mass block 6 below the multi-layer pressure sensitive film prevents adhesion and improves the overload capacity and linearity of the pressure sensor.

Further, the multi-layer pressure sensitive film includes a silicon nitride layer 5 , a polysilicon layer 8 , a silicon oxide layer 9 , and a silicon nitride insulating layer 10 .

Further, interconnection 12 formed on piezoresistor 11 is also included.

Further, a protective layer formed on the surface of the piezoresistor 11 is also included.

Further, it also includes a glass piece 14 bonded to the back of the substrate silicon wafer 1 .

The present invention also proposes a method for manufacturing a pressure sensor chip based on MEMS technology, comprising the following steps:

(1) etching a pressure reference cavity 2 on the substrate;

(2) depositing a sacrificial layer 3, the sacrificial layer 3 covering the pressure reference cavity 2;

(3) etching the half hole 4 on the sacrificial layer 3;

(4) Depositing a silicon nitride layer 5 on the sacrificial layer 3, the silicon nitride fills the half hole 4 on the sacrificial layer to form a mass 6;

(5) releasing the sacrificial layer 3;

(6) Deposit a polysilicon layer 8, a silicon oxide layer 9, and a silicon nitride insulating layer 10 on the silicon nitride layer 5 to form a multilayer pressure sensitive film;

(7) Deposit polysilicon film, doping with ion implantation, and etch piezoresistor 11 to form a Wheatstone bridge structure;

(8) The interconnection leads 12 are prepared.

Further, before step (1), it also includes the steps of determining the size of the chip and the pressure-sensitive membrane according to the range requirements of the pressure sensor, using finite element analysis software to determine the stress distribution of the multilayer composite membrane, and arranging the polycrystalline resistor and the position of the mass block.

Further, etching out the pressure reference chamber 2 includes oxidizing the P-type or N-type polished silicon wafer 1, photolithography and wet etching to form a shallow silicon cup with a depth of about 6-8um.

Further, the semi-holes 4 include a plurality, with a depth of 2-4 microns and a diameter of 1-2 microns.

Further, it also includes bonding a glass sheet 14 on the back of the substrate to form an absolute pressure sensor chip.

Description of drawings

Fig. 1 is a cross-sectional view of a multi-pressure form pressure sensor chip sealing gauge pressure based on MEMS technology related to one embodiment of the present invention;

Fig. 2 is a cross-sectional view of the gauge pressure of a multi-pressure form pressure sensor chip based on MEMS technology related to one embodiment of the present invention;

3 is an absolute pressure sectional view of a multi-pressure form pressure sensor chip based on MEMS technology related to one embodiment of the present invention;

FIG. 4 is a process flow chart of a MEMS-based multi-pressure form pressure sensor chip and its manufacturing method related to one embodiment of the present invention.

Among them: 1 is a P-type or N-type substrate silicon wafer, 2 is a shallow silicon cup, 3 is a PSG sacrificial layer, 4 is a half hole, 5 is a silicon nitride layer, 6 is a silicon nitride mass block, and 7 is a sacrificial layer Release through hole, 8 is polysilicon, 9 is thermal oxide layer, 10 is silicon nitride insulating layer, 11 is polycrystalline resistor, 12 is metal interconnection, 13 is gauge pressure chip pressure reference cavity, 14 is bonding glass sheet.

detailed description

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the specific implementation manners of the present invention will be described in detail below in conjunction with the accompanying drawings 1-4.

Example 1

The present invention proposes a sealed gauge pressure MEMS pressure sensor chip, referring to Fig. 1, comprising a P-type or N-type substrate silicon chip 1, a shallow silicon cup 2 formed on the substrate silicon chip 1, the depth of the shallow silicon cup 2 6-8 microns, a sacrificial layer 3, such as a PSG sacrificial layer, is deposited in the shallow silicon cup 2, and a pressure reference chamber is formed after the sacrificial layer 3 is released. The pressure sensor chip includes a pressure-sensitive membrane formed by a 4-layer composite membrane. The composite membrane includes a silicon nitride membrane 5, a polysilicon membrane 8, a thermal oxide membrane 9, and a silicon nitride insulating layer 10. When the pressure-sensitive membrane faces a shallow silicon cup On the side, a plurality of mass blocks 6 are formed; the design of the mass blocks 6 is beneficial to prevent the phenomenon of release adhesion, and the mass blocks are located in the stress matching area of the piezoresistor, which can improve the sensitivity and linearity of the pressure sensor; the silicon nitride insulation on the top layer of the composite film A polysilicon resistance layer is prepared on the layer 10, and a polysilicon varistor 11 is formed by ion implantation and etching to form a Wheatstone bridge structure. Varistors are distributed in the symmetrical area of tensile stress and compressive stress on the pressure-sensitive film; polysilicon resistors are made on the top layer of silicon nitride of the composite film, and silicon nitride can shield charged ions and form an SOI structure, improving the The operating temperature range of the chip. It also includes ion implantation to form an ohmic contact boron-concentrated region, and deposits metal interconnection wires 12 . It also includes a passivation protection layer formed on the surface of the polysilicon varistor 11 .

Example 2

The present invention proposes a gauge pressure MEMS pressure sensor chip. Referring to FIG. 2, the same structure and components as those in Embodiment 1 will not be repeated. Referring to the cavity 13, a gauge pressure sensor chip is prepared, wherein: silicon nitride 4 is an ICP etch barrier layer, which realizes self-stopping of corrosion.

Example 3

The present invention proposes an absolute pressure MEMS vacuum pressure sensor chip, as shown in Figure 3, on the basis of the gauge pressure chip, a silicon-glass bonding process is performed, and the glass 14 is bonded to the substrate silicon wafer 1 to form an absolute pressure vacuum pressure reference cavity 13. The preparation of the absolute pressure sensor chip can be completed. The same structures and components as those in Embodiments 1 and 2 will not be repeated.

Example 4

For the MEMS pressure sensor chip of Embodiment 1-3, the present embodiment provides its preparation method, referring to Figure 4, the multi-pressure form pressure sensor chip based on the MEMS process proposed by the present invention and its preparation method include the following steps:

(1) Determine the size of the chip and pressure-sensitive membrane according to the range requirements of the pressure sensor, use finite element analysis software to determine the stress distribution of the multilayer composite membrane, and arrange polycrystalline resistors and mass blocks;

(2) P-type or N-type polished silicon wafer 1 is oxidized, and a shallow silicon cup 2 with a depth of about 6-8um is formed by photolithography and wet etching, which is used as a pressure reference cavity for the pressure sensor;

(3) Deposit a PSG sacrificial layer 3, the sacrificial layer covers the shallow silicon cup 2, and is about 1um thicker than the shallow silicon cup;

(4) half-hole 4 is etched on the sacrificial layer 3; the etching depth of the half-hole is 2-4 microns, and the aperture is 1-2 microns;

(5) PECVD silicon nitride layer 5 on the sacrificial layer, silicon nitride fills the half hole 4 of the sacrificial layer to form a mass 6, and etches silicon nitride to form a release through hole 7; wherein the etching method is, for example, dry method Etching, the pore size is about 3-4 microns;

(6) The sacrificial layer 3 is released by wet method or dry method HF, and the sealed reference cavity 2 of the pressure sensor is released;

(7) LPCVD polysilicon 8, thermal oxidation to generate silicon oxide 9, and then deposit a silicon nitride insulating layer 10 by PECVD process to form a sensitive film of the pressure sensor, seal the release through hole 7 to form a pressure reference chamber, and heat it at 1000-1100 ° C Annealing releases film stress; wherein the thickness ratio of the first silicon nitride film 5, the polysilicon film 8, the silicon oxide film 9, and the second silicon nitride film 10 is 1-2:0.5-1.5:4-8:1-2 , preferably 1.5:1:6:1.5; the thickness is determined by the range of the pressure sensor chip;

(8) LPCVD polysilicon thin film, doping by ion implantation, etching the piezoresistor 11 to form a Wheatstone bridge structure;

(9) Ion implantation forms an ohmic contact boron-concentrated region, deposits metal interconnection leads 12, and completes the preparation of a sealed gauge pressure sensor chip after testing and cutting.

For gauge pressure sensor chips, the following steps are also included:

Through the ICP deep etching process, the first silicon nitride film 5 is an ICP etching barrier layer, which realizes self-stopping of etching, and forms a pressure reference chamber 13 of a gauge pressure chip.

For the absolute pressure vacuum pressure sensor chip, further include the following steps:

The silicon-glass bonding process is carried out on the basis of the gauge pressure chip, and the glass sheet 14 is bonded to the substrate silicon chip 1 to form an absolute pressure vacuum pressure reference cavity, which can complete the preparation of the absolute pressure sensor chip.

It should be noted that the above embodiments are preferred embodiments, and the involved modules are not necessarily required by this application. Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other.

The application has been described in detail above, and specific examples have been used in this paper to illustrate the principles and implementation methods of the application. The descriptions of the above embodiments are only used to help understand the method and core idea of the application; meanwhile, for this field Those of ordinary skill in the art, based on the idea of this application, will have changes in the specific implementation and scope of application. In summary, the content of this specification should not be construed as limiting the application.

Claims (5)

1. a kind of pressure sensor chip manufacture method based on mems technique, comprises the following steps:

(1) corrode on substrate and pressure reference chamber (2)；

(2) deposit sacrifice layer (3), described sacrifice layer (3) covers described pressure reference chamber (2)；

(3) in sacrifice layer (3) upper etching half bore (4)；

(4) in sacrifice layer (3) upper deposition the first silicon nitride layer (5), described first silicon nitride layer fills up half bore on sacrifice layer (4), To form mass (6)；

(5) releasing sacrificial layer (3)；

(6) in the first silicon nitride layer (5) upper deposit polycrystalline silicon layer (8), silicon oxide layer (9), the second silicon nitride layer (10), to constitute Multilayer pressure sensitive membrane；

(7) deposited polycrystalline silicon thin film, ion implantation doping, and etch varistor (11), form wheatstone bridge configuration；

(8) prepare interconnecting line (12).

2. a kind of pressure sensor chip manufacture method based on mems technique according to claim 1 it is characterised in that: Before step (1), also include determining chip and pressure sensitive film size, using finite element according to pressure transducer range requirement Analysis software determines the stress distribution of multilayer complex films, the step of arrangement polycrystalline resistor and mass position.

3. a kind of pressure sensor chip manufacture method based on mems technique according to claim 1 it is characterised in that: Described corrosion pressure reference chamber (2) and includes p-type or N-shaped polished silicon slice (1) are aoxidized, photoetching wet etching goes out 6- The shallow silicon cup of 8um depth.

4. a kind of pressure sensor chip manufacture method based on mems technique according to claim 1 it is characterised in that: Described half bore (4) inclusion is multiple, has depth, the aperture of 1-2 micron of 2-4 micron.

5. a kind of pressure sensor chip manufacture method based on mems technique according to claim 1 it is characterised in that: It is additionally included in substrate back bonding sheet glass (14), to form absolute pressure pressure sensor chip.