CN104062464B - MEMS piezoresistive acceleration and pressure integrated sensor and manufacturing method thereof - Google Patents

Abstract

The present invention discloses a MEMS piezoresistive acceleration and pressure integrated sensor based on anodic bonding packaging and a manufacturing method thereof. The sensor integrates a piezoresistive acceleration sensor and a piezoresistive pressure sensor at the same time, and has a first bonding glass-silicon-second bonding glass sandwich structure. The MEMS piezoresistive acceleration and pressure integrated sensor of the present invention has a novel structure, light weight, small size, good stability, and strong anti-pollution ability. In addition, in the present invention, the same process is used on the same chip, and different designs are used to achieve the two capabilities of pressure measurement and acceleration measurement, and the process flow is simple. The sensor of the present invention has certain application prospects in the fields of aerospace, military, automobile, environmental monitoring, etc.

Description

A MEMS piezoresistive acceleration and pressure integrated sensor and manufacturing method

(1) Technical field

The invention relates to a piezoresistive acceleration and pressure integrated sensor in the field of MEMS (micro-electromechanical systems) sensors and a manufacturing method thereof, in particular to a MEMS piezoresistive acceleration and pressure integrated sensor based on anodic bonding packaging and a manufacturing method thereof.

(2) Background technology

With the advancement of micromachining technology and the application requirements of small intelligent sensor systems, the integration of multiple sensors on a single chip has become a development trend. In aerospace, military, automobile, environmental monitoring and other fields, parameters such as acceleration, pressure and temperature are often measured simultaneously. However, in these applications, due to the strict limitations of environmental adaptability, volume, cost, and functions, the sensors are required to be miniaturized, integrated, and multifunctional. Integrated sensors can integrate multiple different sensors on the same chip to detect different physical quantities at the same time, and are small in size and low in unit cost. s concern. However, compared with integrated circuits, the integration of sensors is more difficult. The reason is that the working principles and structural solutions of different sensors are very different. From the perspective of working principles, some sensors are based on the principle of resistance sensitivity, and some sensors are based on the principle of capacitance sensitivity. ; From the perspective of structural schemes, some require special structures such as thin films, while others require special sensitive materials. Therefore, it is necessary to study a set of specific process methods to integrate sensors with different principles and structures.

(3) Contents of the invention

The purpose of the present invention is to provide a MEMS piezoresistive acceleration and pressure integrated sensor based on anodic bonding packaging technology, surface micromachining, and bulk micromachining technology and its manufacturing method, so as to realize the direct integration of two sensors on a wafer manufacture.

To achieve the above object, the technical solution adopted in the present invention is:

A MEMS piezoresistive acceleration and pressure integrated sensor, the sensor integrates a piezoresistive acceleration sensor and a piezoresistive pressure sensor at the same time, and has a first bonded glass-silicon base-second bonded glass sandwich structure; A piezoresistive acceleration sensor cantilever beam and a piezoresistive pressure sensor diaphragm are formed inside the silicon base, and two piezoresistive areas are formed on the front of the silicon base, which are respectively the piezoresistive area and the piezoresistive area of the piezoresistive acceleration sensor. The piezoresistive area of the piezoresistive pressure sensor; the piezoresistive area of the piezoresistive acceleration sensor is located at the root of the upper surface of the cantilever beam of the piezoresistive acceleration sensor, and is injected with light boron to form 4 light boron diffusion piezoresistors, and the light boron diffusion Concentrated boron is injected into the inside of the piezoresistor to form a concentrated boron ohmic contact area; the piezoresistive area of the piezoresistive pressure sensor is located on the upper surface of the diaphragm of the piezoresistive pressure sensor, and light boron is also injected to form four light boron diffusion pressure sensors. resistance, and the inside of the light boron diffusion piezoresistor is injected with concentrated boron to form a concentrated boron ohmic contact region; above the two piezoresistive regions, a silicon dioxide layer is deposited, and a silicon nitride layer is deposited above the silicon dioxide layer. The silicon dioxide layer and the silicon nitride layer are used together as an insulating passivation layer, and the insulating passivation layer is provided with lead holes, and the two piezoresistive areas are connected by metal wires, and the piezoresistive area of the piezoresistive acceleration sensor The four light boron diffusion piezoresistors in the piezoresistive area of the piezoresistive pressure sensor also form a Wheatstone full bridge connection through metal wires; the insulation Amorphous silicon is deposited on the passivation layer, the amorphous silicon is anodically bonded to the first bonding glass, and, using the amorphous silicon as a step, the amorphous silicon is bonded to the first bonding glass Afterwards, a vacuum cavity is formed, which communicates with the piezoresistive acceleration sensor and the piezoresistive pressure sensor; the back side of the silicon base is anodically bonded to the second bonding glass, and the second bonding glass has air holes, and The air hole is located below the diaphragm of the piezoresistive pressure sensor; a concentrated boron wire is formed on the front of the silicon base, and a metal pin is connected above the concentrated boron wire, and the concentrated boron wire connects the working area of the sensor with the The metal pins are connected.

In the MEMS piezoresistive acceleration and pressure integrated sensor of the present invention, the silicon base is preferably an n-type (100) silicon wafer; the thickness of the amorphous silicon deposited above the insulating passivation layer is preferably 2-4 μm.

The working principle of the MEMS piezoresistive acceleration and pressure integrated sensor of the present invention is as follows: the MEMS piezoresistive acceleration of the present invention, the pressure integrated sensor is mainly based on the piezoresistive characteristics of monocrystalline silicon after injecting boron, and the piezoresistive acceleration sensor cantilever and piezoresistive After the light boron diffusion piezoresistor on the diaphragm of the type pressure sensor is subjected to force, the resistivity changes, and the electrical signal output proportional to the force change can be obtained through the Wheatstone full bridge, and the measured electrical signal output can be known by measuring the electrical signal output. The size of physical quantities (including acceleration and pressure). In the present invention, we inject boron into the n-type (100) crystal silicon chip to realize the p-type piezoresistive, and utilize the PN junction to realize the isolation of the piezoresistive. The resistance has different influences, in order to increase the sensitivity as much as possible, the arrangement mode of the light boron diffusion piezoresistor in the piezoresistive area of the piezoresistive acceleration sensor and the light boron diffusion piezoresistor in the piezoresistive area of the piezoresistive pressure sensor It is: longitudinally along the (1,1,0) crystal direction of the silicon base, and laterally along the (1,-1,0) crystal direction of the silicon base, the longitudinal piezoresistive coefficient and the transverse piezoresistive coefficient are 71.8, - 66.3.

In order to improve the sensitivity, the piezoresistive acceleration sensor of the present invention is preferably designed as a single cantilever beam, and the piezoresistive acceleration sensor piezoresistive area has 4 light boron diffusion piezoresistors, and 2 of them have a pressure on the bridge arm light boron diffusion. The resistance is symmetrically distributed in the stress concentration area at the root of the cantilever beam, and the other two light boron diffusion piezoresistors are symmetrically distributed in the zero stress area. Of course, different beam structures can also be used according to different sensitivity requirements, such as single-sided double-beam, double-sided double-beam, double-sided four-beam, four-side four-beam, four-side eight-beam, etc. In addition, the light-boron diffusion piezoresistors can also be distributed in different ways, and 4 light-boron diffusion piezoresistors (can be 4 or 8 in half) are connected by metal wires to form a Whiston full bridge. A connection mode of the metal pins of the piezoresistive acceleration sensor of the present invention is: the fourth pin is connected to the positive pole of the power supply, which is shared with the piezoresistive pressure sensor in the present invention, the fifth pin is connected to the negative output of the piezoresistive acceleration sensor, and the fourth pin is connected to the negative output of the piezoresistive acceleration sensor. The six pins are grounded, and the seventh pin is connected to the output of the piezoresistive acceleration sensor.

The piezoresistive pressure sensor of the present invention adopts a rectangular membrane design, and four light boron diffusion piezoresistors are arranged in parallel to make full use of the transverse piezoresistive effect. Such a piezoresistive pressure sensor has uniform distribution of bridge arm resistance, output linearity and The advantage of better consistency. Of course, according to different sensitivity requirements, the light boron diffusion piezoresistors can be distributed in different ways. Four light boron diffusion piezoresistors of the piezoresistive pressure sensor of the present invention are connected by metal wires to form a Whiston full bridge, and a connection mode of the metal pins of the piezoresistive pressure sensor is: the first pin is connected to the piezoresistive The output of the pressure sensor is positive, the second pin is grounded, the third pin is connected to the negative output of the piezoresistive pressure sensor, and the fourth pin is connected to the positive pole of the power supply, which shares the positive pole of the power supply with the piezoresistive acceleration sensor in the present invention.

The present invention also provides a manufacturing method of the MEMS piezoresistive acceleration and pressure integrated sensor, and the manufacturing method is carried out as follows:

a) Take a silicon wafer as the silicon base, polish and clean both sides, first deposit a layer of silicon dioxide on both sides, then deposit a layer of silicon nitride on both sides, and dry-etch silicon nitride and silicon dioxide to the silicon base on the front side top surface;

b) On the front side of the silicon base, a layer of silicon dioxide protective layer is grown by thermal oxygen, and the front photoresist is used as a mask to photoetch the piezoresistive area of the piezoresistive acceleration sensor and the piezoresistive area of the piezoresistive pressure sensor, and then respectively The two piezoresistive regions are injected with light boron to form a light boron diffusion piezoresistor and remove the photoresist;

c) The front photoresist is used as a mask to photoetch the concentrated boron wire area, and the boron-rich ohmic contact area is photo-etched in the light boron diffusion piezoresistive area, and then the concentrated boron is injected to form a silicon-based internal boron-concentrated wire, and in the light boron diffusion piezoresistive area. A boron-rich ohmic contact area is formed inside the boron diffusion piezoresistor, the photoresist is removed, and annealed;

d) Deposit a layer of silicon dioxide on both sides first, and then deposit a layer of silicon nitride on both sides, and the silicon dioxide layer and the silicon nitride layer on the front side together serve as an insulating passivation layer;

e) The front photoresist is used as a mask to photoetch the slice groove area, dry reactive ion etching (RIE) silicon nitride and silicon dioxide to the top surface of the silicon base, exposing the silicon base in the slice groove area;

f) A layer of amorphous silicon is deposited on the front side, and the amorphous silicon is in direct contact with the top surface of the silicon substrate in the slice groove area;

g) The front photoresist is used as a mask to photoetch the working area and the pattern of the metal pin area, RIE etches the amorphous silicon to the silicon nitride layer, and removes the photoresist;

h) The photoresist on the front side is used as a mask to photoetch the lead hole, and the dry RIE is used to etch silicon nitride and silicon dioxide to the top surface of the silicon base, and the photoresist is removed to form a lead hole;

i) Deposit the metal wire layer on the front side, use the photoresist on the front side as a mask to photoetch the metal wire and pin pattern, corrode the metal in the area not covered by the photoresist, remove the photoresist, and perform alloying treatment to form metal wires and metal tubes foot;

j) The photoresist on the back side is used as a mask to etch the silicon window, and the silicon nitride and silicon dioxide are etched to the silicon base surface by RIE, the photoresist is removed, and the silicon nitride and silicon dioxide layer is used as a mask for wet etching The silicon base forms a piezoresistive acceleration sensor and a piezoresistive pressure sensor film;

k) Dry RIE etching of the remaining silicon nitride and silicon dioxide on the back to the silicon base surface, and performing silicon-glass anode bonding on the back;

l) The photoresist on the front side is used as a mask to photoetch the cantilever beam release pattern, and DRIE cuts through the silicon nitride, silicon dioxide, and silicon substrate to form the cantilever beam structure of the piezoresistive acceleration sensor, and removes the photoresist;

m) Anodic bonding of amorphous silicon-glass on the front side;

n) Scribing to realize the packaging of a single chip. Scribing is completed in two steps: the first scribing removes the glass above the metal pins; the second scribing removes the structure in the slicing slot, separates a single chip, and completes the package .

In step k) of the manufacturing method of the MEMS piezoresistive acceleration and pressure integrated sensor according to the present invention, the recommended process parameters for silicon-glass anodic bonding on the back are: voltage 300-500V, current 15-20mA, temperature 300-400 ℃, pressure 2000-3000N, time 5-10min.

In step m) of the manufacturing method of the MEMS piezoresistive acceleration and pressure integrated sensor described in the present invention, the process parameters recommended for front-side amorphous silicon-glass anodic bonding are: voltage 450-1000V, current 15-25mA, temperature 300 ～400℃, pressure 2000～3000N, time 15～25min.

The anodic bonding technology described in the present invention is a prior art, and this technology is well known to those skilled in the art. The performance of the silicon wafer is similar to that of the electrolyte, and when the temperature of the silicon wafer rises to 300 ° C ~ 400 ° C, the resistivity will drop to 0.1Ω·m due to intrinsic excitation, and the conductive particles (such as Na ⁺ ) in the glass are outside Under the action of an electric field, it drifts to the glass surface of the negative electrode, leaving a negative charge on the glass surface close to the silicon wafer. Due to the drift of Na ⁺ , the current flows in the circuit, and a layer of extremely thin width is formed on the glass surface close to the silicon wafer. A space charge region (or depletion layer) of about a few microns. Since the depletion layer is negatively charged and the silicon wafer is positively charged, there is a large electrostatic attraction between the silicon wafer and the glass, which makes the two closely contact, and physical and chemical reactions occur on the bonding surface to form a firm bond. Si-O covalent bonds firmly link the silicon-glass interface together. According to the above principle, the anode bonding technology is not suitable for the bonding of boron-implanted n-type silicon and glass. When the bonding current passes through the silicon-glass bonding surface during the bonding process, the bonding voltage of 500-1500V is easy to reverse the breakdown of the PN junction near the bonding surface, causing its leakage, destroying the circuit on the MEMS device, and affecting the device. performance. Aiming at the problems existing in the above-mentioned existing anodic bonding technology, the second bonding process of the present invention uses amorphous silicon as the conduction layer between the silicon base and the glass, so that the bonding current can be as far as possible along the silicon-amorphous The silicon-glass direction passes through, effectively avoiding the strong electric field of the PN junction, and finally realizes the anodic bonding of the upper layer of amorphous silicon and glass. Experiments have proved that this kind of amorphous silicon-glass anodic bonding can still ensure that it is close to the silicon-glass Bonding strength and airtightness of glass. The packaging of the MEMS piezoresistive acceleration and pressure integrated sensor based on the anodic bonding package needs to be anodically bonded twice. The first bonding is the back silicon-glass anode bonding, which is relatively easy to implement. Bonding is the anodic bonding of amorphous silicon and glass on the front side, which is relatively difficult, and the bonding voltage can be appropriately increased to increase the bonding time. In the present invention, there is another very big advantage of using amorphous silicon to bond with glass. The bonding method avoids the direct contact between glass and silicon, and eliminates the Na ⁺ plasma that may be generated on the bonding surface of glass and silicon. pollution.

In the MEMS piezoresistive acceleration and pressure integrated sensor structure of the present invention, in the front amorphous silicon-glass bonding process, amorphous silicon is used as a step to form a vacuum cavity to communicate with the piezoresistive acceleration sensor and the piezoresistive pressure sensor . Described amorphous silicon is used as a step, and the design method that two sensors share a vacuum cavity has two very significant advantages: (1) removes the bonding area between two sensors, reduces the MEMS of the present invention. The volume of the piezoresistive acceleration and pressure integrated sensor reduces the cost of a single chip; (2) The first bonding glass can be directly bonded without slotting. In the MEMS piezoresistive acceleration and pressure integrated sensor structure of the present invention, the thickness of the vacuum chamber directly depends on the thickness of the amorphous silicon deposition, because the amorphous silicon is deposited too thickly, its density and adhesion will be affected, and will Increase the difficulty of photolithography in the next step, so in order to avoid the direct bonding of glass and silicon nitride in the bonding process, while ensuring the good performance of amorphous silicon, experiments have proved that the thickness of amorphous silicon in the sensor of the present invention can be taken as 2 ~4μm.

The present invention is a MEMS piezoresistive acceleration and pressure integrated sensor packaged by anodic bonding. The sensor integrates a piezoresistive acceleration sensor and a piezoresistive pressure sensor at the same time. It is recommended to use an n-type (100) silicon wafer as the silicon base. Surface micromachining technology and bulk micromachining technology to manufacture cantilever beams and diaphragms with light boron diffusion piezoresistors as piezoresistive acceleration sensors and piezoresistive pressure sensor structures, and use secondary anode bonding technology for wafer-level packaging , where the first anodic bonding uses silicon-glass anodic bonding, and the second anodic bonding uses the amorphous silicon layer as an intermediate layer to share the bonding current, protect the sensor PN junction, and realize amorphous silicon-glass anodic bonding . The MEMS piezoresistive acceleration and pressure integrated sensor of the invention has the advantages of novel structure, light weight, small volume, good stability and strong anti-pollution ability. In addition, in the present invention, the same process is used on the same chip, and different designs are used to realize the two capabilities of pressure measurement and acceleration measurement. The process flow is simple, and the package using amorphous silicon-glass anode bonding technology solves the -During the glass anodic bonding process, it is easy to break down the PN junction on the silicon surface and easily generate ion pollution. The sensor of the invention has certain application prospects in the fields of aerospace, military affairs, automobiles, environment monitoring and the like.

(4) Description of drawings

Fig. 1 is the sectional structure schematic diagram of MEMS piezoresistive acceleration of the present invention, pressure integrated sensor;

Fig. 2 is the top view of the MEMS piezoresistive acceleration and pressure integrated sensor of the present invention;

Figures 3 to 16 are schematic cross-sectional views of the manufacturing process of the MEMS piezoresistive acceleration and pressure integrated sensor of the present invention:

Figure 3 is a schematic diagram of first depositing a silicon dioxide layer and a silicon nitride layer on both sides of a silicon base, and then dry etching silicon nitride and silicon dioxide from the front to the top surface of the silicon base;

Fig. 4 is the schematic diagram of the light boron diffusion piezoresistor forming the piezoresistive area of the piezoresistive acceleration sensor and the light boron diffusion piezoresistor of the piezoresistive pressure sensor piezoresistive area;

5 is a schematic diagram of forming a boron-concentrated wire and a boron-concentrated ohmic contact region;

Figure 6 is a schematic diagram of depositing a silicon dioxide layer and a silicon nitride layer on both sides to form an insulating passivation layer;

Fig. 7 is a schematic diagram of etching out the slice groove area;

FIG. 8 is a schematic diagram of depositing amorphous silicon on the front side;

FIG. 9 is a schematic diagram of etching amorphous silicon to form the working area of the sensor and the pattern of the metal pin area;

10 is a schematic diagram of forming a lead hole;

11 is a schematic diagram of forming metal wires and metal pins;

12 is a schematic diagram of forming a piezoresistive acceleration sensor and a piezoresistive pressure sensor film;

Figure 13 is a schematic diagram of silicon-glass anodic bonding on the back;

14 is a schematic diagram of a cantilever beam structure forming a piezoresistive acceleration sensor;

Fig. 15 is a schematic diagram of front-side amorphous silicon-glass anodic bonding;

Figure 16 is a schematic diagram of dicing to complete the package;

In Figures 1 to 16: 1-silicon dioxide layer in the front insulating protection layer, 1'-the second silicon dioxide layer on the back side, 2-silicon nitride layer in the front insulating protection layer, 2'-the second silicon dioxide layer on the back side Silicon nitride layer, 3-metal wire, 4-first bonding glass, 5-amorphous silicon, 6-metal pin, 7-silicon base, 8-concentrated boron wire, 9-piezoresistive pressure sensor Boron diffusion piezoresistive, 10-piezoresistive pressure sensor light boron diffusion piezoresistive inner concentrated boron ohmic contact area, 11-lean boron diffusion piezoresistive of piezoresistive acceleration sensor, 12-piezoresistive acceleration sensor light boron diffusion pressure Concentrated boron ohmic contact area inside the resistor, 13 - piezoresistive acceleration sensor cantilever beam, 14 - vacuum cavity, 15 - vent hole, 16 - piezoresistive pressure sensor diaphragm, 17 - second bonding glass, 18 - The first silicon dioxide layer on the front side (etched later), 18'-the first silicon dioxide layer on the back side, 19-the first silicon nitride layer on the front side (etched later), 19'-the first silicon nitride layer on the back side layer, 20-slicing slots, and 8a-8g in Figure 2 represent the first to seventh pins in turn;

Fig. 17 is a pin connection mode of the MEMS piezoresistive acceleration and pressure integrated sensor of the present invention;

Pin definition in Figure 17: ① - The first pin is connected to the positive output of the piezoresistive pressure sensor, ② - The second pin is grounded, ③ - The third pin is connected to the negative output of the piezoresistive pressure sensor, ④ - The fourth pin The pin is connected to the positive pole of the power supply, ⑤-the fifth pin is connected to the negative output of the piezoresistive acceleration sensor, ⑥-the sixth pin is grounded, ⑦-the seventh pin is connected to the positive output of the piezoresistive acceleration sensor.

(5) Specific implementation methods

The present invention will be further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited thereto.

As shown in Figure 1, the MEMS piezoresistive acceleration and pressure integrated sensor adopts the first bonded glass-silicon base-second bonded glass sandwich structure, and the MEMS piezoresistive acceleration and pressure integrated The sensor mainly includes: a silicon base (7), a piezoresistive acceleration sensor cantilever beam (13) for measuring uniaxial acceleration, a piezoresistive pressure sensor diaphragm (16) for measuring pressure, and a boron-concentrated wire (8) , a metal pin (6), a second bonding glass (17) that is anode-bonded with the silicon base, and a first bonding glass (4) that is anode-bonded with the amorphous silicon (5).

Wherein, the upper surface root of the piezoresistive acceleration sensor cantilever beam (13) for measuring uniaxial acceleration is injected with light boron as the light boron diffusion piezoresistor (11) of the piezoresistive acceleration sensor, and in the piezoresistive Concentrated boron is injected inside the piezoresistive light boron diffuser of the acceleration sensor to form a concentrated boron ohmic contact area (12), and a silicon dioxide layer (1) and a silicon nitride layer (2) are deposited above the piezoresistive area of the piezoresistive acceleration sensor as insulation The passivation layer has lead holes on the insulating passivation layer and uses metal wires (3) to communicate with the piezoresistive area of the piezoresistive acceleration and pressure sensors; the piezoresistive area of the piezoresistive acceleration sensor contains 4 thin boron diffused piezoresistors , two pairs of bridge arm light boron diffusion piezoresistors are symmetrically distributed in the stress concentration area at the root of the cantilever beam, and the other two pairs of bridge arm light boron diffusion piezoresistors are symmetrically distributed in the zero stress area, and are formed by metal wires (3) Whiston full-bridge connection, when there is an acceleration perpendicular to the surface of the device, the cantilever beam of the piezoresistive acceleration sensor bends, and the piezoresistivity at the root of the cantilever beam on the upper surface of the piezoresistive acceleration sensor is subjected to force, and the resistivity changes , as shown in Figure 2, the piezoresistance at the root of the cantilever beam of the piezoresistive acceleration sensor is located on the opposite bridge of the Wheatstone full bridge, and the electrical signal output proportional to the force change can be obtained through the Wheatstone full bridge. By measuring the electrical signal The output can know the magnitude of the acceleration. The design of the Whiston full bridge improves the sensitivity of the piezoresistive acceleration sensor in the present invention and can ensure good linearity.

The piezoresistive pressure sensor diaphragm (16) can be used to measure fluid pressure (including pressure, water pressure), and the upper surface of the piezoresistive pressure sensor diaphragm (16) is injected with dilute boron as the dilute boron of the piezoresistive pressure sensor. Boron diffusion piezoresistor (9), piezoresistive pressure sensor light boron diffusion piezoresistor is injected with concentrated boron to form a concentrated boron ohmic contact area (10), silicon dioxide layer is deposited above the piezoresistive area of piezoresistive pressure sensor (1 ) and the silicon nitride layer (2) are used as an insulating passivation layer, and a lead hole is opened on the insulating passivation layer and a metal wire (3) is used to communicate with the piezoresistive area of the piezoresistive acceleration and pressure sensor; the piezoresistive pressure sensor The piezoresistive area also includes 4 thin boron diffused piezoresistors, which are connected by a Wheatstone full bridge through metal wires (3). The piezoresistive on the diaphragm is affected by the force, and the resistivity changes. As shown in Figure 2, the two piezoresistive strips in the middle of the upper surface of the diaphragm of the piezoresistive pressure sensor and the two piezoresistive strips on the outside are respectively located at the Wheatstone full bridge. For the opposite bridge, the electrical signal output proportional to the force change can be obtained through the Wheatstone full bridge, and the measured pressure can be known by measuring the electrical signal output. The design of using the Wheatstone full bridge improves the sensitivity of the piezoresistive pressure sensor part in the present invention and can ensure good linearity.

Chip packaging adopts secondary anode bonding technology. The first anodic bonding is the anodic bonding of the second bonding glass (17) with vent holes (15) on the back of the chip and the silicon-based silicon-glass; the second anodic bonding uses an amorphous silicon layer as an intermediate layer Make the bonding current not pass through the PN junction, protect the PN junction of the sensor, and realize the anodic bonding between the front amorphous silicon (5) and the first bonding glass (4), and the second anodic bonding does not use silicon-glass bonding The reason is that there is a PN junction on the silicon-glass anode bonding surface, and the strong voltage during bonding is easy to break down the PN junction and destroy the electrical performance of the circuit.

In order to avoid the unevenness of the bonding surface between the amorphous silicon (5) and the first bonding glass (4) and ensure the airtightness of the package, the integrated sensor for acceleration and pressure does not use metal wires to connect the working area of the chip with the Metal pins (6), but use concentrated boron wires (8) as internal wires to connect the working area of the sensor with the metal pins.

As shown in Figures 3 to 16, the manufacturing process of the MEMS piezoresistive acceleration and pressure integrated sensor of the present invention includes the following steps:

a) As shown in Figure 3: Take a silicon wafer as the silicon substrate (7), polish both sides, clean, first thermally oxidize silicon dioxide (18) and (18') with a thickness of 1 μm on both sides, and then use a low-pressure chemical vapor phase Deposit (LPCVD) silicon nitride (19) and (19') with a thickness of 0.1 μm on both sides, and dry-etch silicon nitride (19) and silicon dioxide (18) on the front side to the top surface of the silicon base (7), Simultaneously, a mask layer for etching silicon on the back side is formed; the silicon base is an n-type (100) silicon wafer;

b) As shown in Figure 4: a thin protective layer of silicon dioxide is grown on the front side of the silicon base (7) by thermal oxygen (to make the implanted ions deviate from the angle of incidence to a certain extent, so as to avoid the ions being just located in the gaps between the atoms of the silicon base and implanted along a certain crystal direction so that no collision occurs), the front photoresist is used as a mask to photoetch the piezoresistive area of the piezoresistive acceleration sensor and the piezoresistive area of the piezoresistive pressure sensor, and then respectively in the two Inject light boron into the piezoresistive area to form the light boron diffusion piezoresistor (11) of the piezoresistive acceleration sensor and the light boron diffusion piezoresistor (9) of the piezoresistive pressure sensor, and remove the photoresist;

c) As shown in Figure 5: the front photoresist is used as a mask to photoetch the concentrated boron wire area, and the light boron diffusion piezoresistive (11) area of the piezoresistive acceleration sensor and the light boron diffusion of the piezoresistive pressure sensor The piezoresistive (9) area is respectively photo-etched with concentrated boron ohmic contact areas, and then injected with concentrated boron to form a silicon-based inner concentrated boron wire (8), and to form a piezoresistive acceleration sensor with a boron-rich boron ohmic contact inside the piezoresistive light boron diffusion Area (12) and the concentrated boron ohmic contact area (10) inside the light boron diffusion piezoresistive piezoresistive pressure sensor, remove the photoresist, and anneal;

d) As shown in Figure 6: first LPCVD double-sided deposition of 0.2 μm thick silicon dioxide (1), (1'), and then LPCVD double-sided deposition of 0.2 μm thick silicon nitride (2), (2'), The silicon dioxide layer (1) and the silicon nitride layer (2) together serve as an insulating passivation layer;

e) As shown in Figure 7: the front photoresist is used as a mask to photoetch the slice groove area, dry RIE etching silicon nitride (2), silicon dioxide (1) to the top surface of the silicon base (7), Exposing the silicon base (7) in the slice groove area;

f) As shown in Figure 8: a layer of amorphous silicon (5) with a thickness of 3 μm is deposited on the front side by plasma-enhanced chemical vapor deposition (PECVD), and the amorphous silicon (5) and the silicon base (7 ) in direct contact with the top surface;

g) As shown in Figure 9: the front photoresist is used as a mask to photoetch the working area and the pattern of the metal pin (6), RIE etches the amorphous silicon (5) to the silicon nitride layer (2), and removes the photoresist Engraving;

h) As shown in Figure 10: the front photoresist is used as a mask to photoetch the lead hole, dry RIE etching silicon nitride (2), silicon dioxide (1) to the top surface of the silicon base (7), and removing the photoresist Resist to form lead holes;

i) As shown in Figure 11: Magnetron sputtering a layer of 1 μm aluminum on the front side, using the photoresist on the front side as a mask to photoetch metal wires (3) and metal pins (6) patterns, and corroding the areas not covered by photoresist Aluminum, removing photoresist, alloying treatment, forming aluminum wires and aluminum pins;

j) As shown in Figure 12: the photoresist on the back is used as a mask to etch silicon windows, and RIE etches silicon nitride (2'), (19'), silicon dioxide (1'), (18') To the bottom surface of the silicon base (7), remove the photoresist, silicon nitride (2'), (19'), and the silicon dioxide layer (1'), (18') together make a mask and wet etch the silicon base (7 ) forming a piezoresistive acceleration sensor and a piezoresistive pressure sensor film;

k) As shown in Figure 13: dry RIE etching the remaining silicon nitride (2'), (19') on the back, silicon dioxide (1'), (18') to the bottom surface of the silicon base (7), the back Perform silicon-glass anodic bonding;

l) As shown in Figure 14: the front photoresist is used as a mask to photoetch the cantilever beam release pattern, and deep reactive ion etching (DRIE) is used to etch through silicon nitride (2), silicon dioxide (1), silicon base ( 7) forming the cantilever beam structure (13) of the piezoresistive acceleration sensor, and removing the photoresist;

m) As shown in Figure 15: A-Si-Glass anode bonding is performed on the front side;

n) As shown in Figure 16: scribing to realize the packaging of a single chip, the scribing is completed in two steps: the first scribing removes the glass (4) above the metal pin (6); the second scribing removes Fragmentation structure in the groove, separate individual chips, and complete packaging.

Further, the MEMS piezoresistive acceleration and pressure integrated sensor manufactured according to the process flow, the thickness of the cantilever beam of the piezoresistive acceleration sensor and the diaphragm of the piezoresistive pressure sensor are the same, in order to obtain the different thicknesses of the two, adjust the pressure Sensitivity of resistive acceleration and piezoresistive pressure sensors, silicon etching on the back side in the process step (j) can be completed twice, as shown in Figure 12, according to the difference in sensitivity of piezoresistive acceleration and piezoresistive pressure sensors Requirements, the thickness of the cantilever beam of the piezoresistive acceleration sensor in this embodiment is 12 μm, and the thickness of the diaphragm of the piezoresistive pressure sensor is 30 μm. Etching together, the specific process is: use the photoresist on the back as a mask to open the etching window on the back of the piezoresistive pressure sensor, RIE etches away silicon nitride and silicon dioxide to the silicon base surface, silicon nitride and silicon dioxide layer as a mask, 40% KOH solution wet etches the silicon base, and the etching depth is controlled at 18 μm to form a difference in the etching depth of the back cavity of the two sensors, and then the photoresist is used as a mask to open the etching window on the back of the piezoresistive acceleration sensor , RIE to etch away silicon nitride and silicon dioxide to the silicon base surface, wet etch the silicon base with 40% KOH solution until the desired piezoresistive acceleration sensor cantilever beam and piezoresistive pressure sensor diaphragm are etched twice After corrosion, cantilever beams of piezoresistive acceleration sensors and diaphragm structures of piezoresistive pressure sensors with different thicknesses are formed.

Further, in order to ensure the quality of the two anodic bonding, through multiple tests, the present invention provides the optimal bonding parameters of the MEMS piezoresistive acceleration and pressure integrated sensor, as shown in Tables 1 and 2.

Table 1 Parameters of the first anodic bonding (silicon-glass)

Table 2 Parameters of the second anodic bonding (amorphous silicon-glass)

Further, in addition to the single-sided single cantilever structure shown in Figure 2, the cantilever beam of the piezoresistive acceleration sensor in the present invention can also use single-sided double cantilever beams, bilateral double-beams, and double-sided cantilever beams according to different sensitivity and resonance frequency requirements. For structures such as four beams, four beams on four sides, and eight beams on four sides, the light boron diffusion piezoresistor can also be distributed in other positions. The piezoresistive pressure sensor part of the present invention is designed with a rectangular membrane, and four thin boron diffusion piezoresistors are arranged in parallel to make full use of the transverse piezoresistive effect. Such a piezoresistive pressure sensor has uniform distribution of bridge arm resistance and linear output The advantages of better accuracy and consistency, of course, according to different sensitivity needs, the light boron diffusion piezoresistor can adopt different distribution methods.

It should be noted that the present invention does not limit the parameters of the cantilever beam structure size, diaphragm thickness, piezoresistive number, piezoresistive size and arrangement distribution of the sensor part, nor does it limit the process parameters of the manufacturing process of the present invention, and This embodiment is only illustrative and does not limit the present invention in any way.

Claims (10)

1. A MEMS piezoresistive acceleration and pressure integrated sensor is characterized in that the sensor integrates a piezoresistive acceleration sensor and a piezoresistive pressure sensor simultaneously, and has a first bonding glass-silicon base-second bond The silicon base has a piezoresistive acceleration sensor cantilever beam and a piezoresistive pressure sensor diaphragm formed inside the silicon base. The piezoresistive area and the piezoresistive area of the piezoresistive pressure sensor; the piezoresistive area of the piezoresistive acceleration sensor is located at the root of the upper surface of the cantilever beam of the piezoresistive acceleration sensor, and is injected with light boron to form 4 light boron diffusion piezoresistors At the same time, the inside of the light boron diffusion piezoresistor is injected with concentrated boron to form a concentrated boron ohmic contact area; the piezoresistive area of the piezoresistive pressure sensor is located on the upper surface of the diaphragm of the piezoresistive pressure sensor, and is also injected with light boron to form 4 The light boron diffusion piezoresistor is rooted, and the inside of the light boron diffusion piezoresistor is injected with concentrated boron to form a concentrated boron ohmic contact area; a silicon dioxide layer is deposited above the two piezoresistive regions, and a silicon dioxide layer is deposited on the silicon dioxide layer. The silicon nitride layer, the silicon dioxide layer and the silicon nitride layer together serve as an insulating passivation layer, and the insulating passivation layer has a lead hole, and the two piezoresistive regions are connected by metal wires, and the piezoresistive The 4 light boron diffused piezoresistors in the piezoresistive area of the acceleration sensor are connected through metal wires to form a Wheatstone full bridge connection, and the 4 light boron diffused piezoresistors in the piezoresistive area of the piezoresistive pressure sensor also form a Wheatstone full bridge through metal wires connection; amorphous silicon is deposited above the insulating passivation layer, the amorphous silicon is anodically bonded to the first bonding glass, and, using the amorphous silicon as a step, the amorphous silicon and the first After the bonding glass is bonded, a vacuum cavity is formed, which communicates with the piezoresistive acceleration sensor and the piezoresistive pressure sensor; the back side of the silicon substrate is anodically bonded to the second bonding glass, and the second bonding glass ribbon There is a vent hole, and the vent hole is located under the diaphragm of the piezoresistive pressure sensor; the front side of the silicon base is also formed with a concentrated boron wire, and a metal pin is connected to the top of the concentrated boron wire, and the concentrated boron wire Connect the sensor working area to the metal pin. 2. MEMS piezoresistive acceleration as claimed in claim 1, pressure integrated sensor, it is characterized in that the light boron diffusion piezoresistivity of described piezoresistive acceleration sensor piezoresistive area and the light boron diffusion piezoresistive of piezoresistive pressure sensor piezoresistive area The arrangement of the boron diffusion piezoresistor is: vertically along the (1,1,0) crystal direction of the silicon base, and horizontally along the (1,-1,0) crystal direction of the silicon base, the vertical piezoresistive coefficient, the lateral The piezoresistive coefficients are 71.8 and -66.3, respectively. 3. MEMS piezoresistive acceleration as claimed in claim 1, pressure integrated sensor, it is characterized in that described piezoresistive acceleration sensor is a single cantilever beam design, the light boron diffusion piezoresistive in piezoresistive area of piezoresistive acceleration sensor There are 4 poles, of which 2 are symmetrically distributed in the stress concentration area at the root of the cantilever with light boron diffusion piezoresistors on the bridge arm, and the other 2 light boron diffusion piezoresistors are symmetrically distributed in the zero stress area. 4. The MEMS piezoresistive acceleration and pressure integrated sensor as claimed in claim 1, characterized in that the piezoresistive pressure sensor adopts a rectangular membrane design, and 4 thin boron diffusers in the piezoresistive area of the piezoresistive pressure sensor The piezoresistors are arranged in parallel. 5. The MEMS piezoresistive acceleration and pressure integrated sensor according to claim 1, characterized in that there are 7 metal pins, the first pin is connected to the positive output of the piezoresistive pressure sensor, and the second pin is grounded , The third pin is connected to the negative output of the piezoresistive pressure sensor, the fourth pin is connected to the positive pole of the power supply, the fifth pin is connected to the negative output of the piezoresistive acceleration sensor, the sixth pin is grounded, and the seventh pin is connected to the piezoresistive acceleration The sensor output is positive, and the piezoresistive pressure sensor and the piezoresistive acceleration sensor share the positive pole of the power supply. 6. The MEMS piezoresistive acceleration and pressure integrated sensor according to any one of claims 1 to 5, characterized in that the silicon substrate is an n-type (100) silicon wafer. 7. The MEMS piezoresistive acceleration and pressure integrated sensor according to any one of claims 1-5, characterized in that the thickness of the amorphous silicon deposited above the insulating passivation layer is 2-4 μm. 8. MEMS piezoresistive acceleration as claimed in claim 1, the manufacturing method of pressure integrated sensor is characterized in that described manufacturing method is carried out as follows: a) Take a silicon wafer as the silicon base, polish and clean both sides, first deposit a layer of silicon dioxide on both sides, then deposit a layer of silicon nitride on both sides, and dry-etch silicon nitride and silicon dioxide to the silicon base on the front side top surface; b) On the front side of the silicon base, a layer of silicon dioxide protective layer is grown by thermal oxygen, and the front photoresist is used as a mask to photoetch the piezoresistive area of the piezoresistive acceleration sensor and the piezoresistive area of the piezoresistive pressure sensor, and then respectively The two piezoresistive regions are injected with light boron to form a light boron diffusion piezoresistor and remove the photoresist; c) The front photoresist is used as a mask to photoetch the concentrated boron wire area, and the boron-rich ohmic contact area is photo-etched in the light boron diffusion piezoresistive area, and then the concentrated boron is injected to form a silicon-based internal boron-concentrated wire, and in the light boron diffusion piezoresistive area. A boron-rich ohmic contact area is formed inside the boron diffusion piezoresistor, the photoresist is removed, and annealed; d) Deposit a layer of silicon dioxide on both sides first, and then deposit a layer of silicon nitride on both sides, and the silicon dioxide layer and the silicon nitride layer on the front side together serve as an insulating passivation layer; e) The front photoresist is used as a mask to photoetch the slice groove area, and the silicon nitride and silicon dioxide are etched to the top surface of the silicon base by dry RIE to expose the silicon base in the slice groove area; f) A layer of amorphous silicon is deposited on the front side, and the amorphous silicon is in direct contact with the top surface of the silicon substrate in the slice groove area; g) The front photoresist is used as a mask to photoetch the working area and the pattern of the metal pin area, RIE etches the amorphous silicon to the silicon nitride layer, and removes the photoresist; h) The photoresist on the front side is used as a mask to photoetch the lead hole, and the dry RIE is used to etch silicon nitride and silicon dioxide to the top surface of the silicon base, and the photoresist is removed to form a lead hole; i) Deposit the metal wire layer on the front side, use the photoresist on the front side as a mask to photoetch the metal wire and pin pattern, corrode the metal in the area not covered by the photoresist, remove the photoresist, and perform alloying treatment to form metal wires and metal tubes foot; j) The photoresist on the back side is used as a mask to etch the silicon window, and the silicon nitride and silicon dioxide are etched to the silicon base surface by RIE, the photoresist is removed, and the silicon nitride and silicon dioxide layer is used as a mask for wet etching The silicon base forms a piezoresistive acceleration sensor and a piezoresistive pressure sensor film; k) Dry RIE etching of the remaining silicon nitride and silicon dioxide on the back to the silicon base surface, and performing silicon-glass anode bonding on the back; l) The photoresist on the front side is used as a mask to photoetch the cantilever beam release pattern, and DRIE cuts through the silicon nitride, silicon dioxide, and silicon substrate to form the cantilever beam structure of the piezoresistive acceleration sensor, and removes the photoresist; m) Anodic bonding of amorphous silicon-glass on the front side; n) Scribing to realize the packaging of a single chip. Scribing is completed in two steps: the first scribing removes the glass above the metal pins; the second scribing removes the structure in the slicing slot, separates a single chip, and completes the package . 9. MEMS piezoresistive acceleration as claimed in claim 8, the manufacturing method of pressure integrated sensor is characterized in that in the step k), the technological parameter that carries out silicon-glass anodic bonding is: voltage 300～500V, electric current 15～ 20mA, temperature 300-400°C, pressure 2000-3000N, time 5-10min. 10. The manufacturing method of MEMS piezoresistive acceleration and pressure integrated sensor as claimed in claim 8, characterized in that in the step m), the process parameters for performing amorphous silicon-glass anodic bonding on the front side are: voltage 450～1000V, current 15～25mA, temperature 300～400℃, pressure 2000～3000N, time 15～25min.