CN215893844U - Constant-temperature heating MEMS silicon piezoresistive pressure sensor - Google Patents

Abstract

The utility model provides a constant-temperature heating MEMS silicon piezoresistive pressure sensor, which provides a stable temperature field for an MEMS silicon piezoresistive chip by arranging a silicon substrate layer, a heating Pt resistance layer, a metal Al heat sink structure layer and a piezoresistive device layer, and isolates an MEMS sensitive element from an external temperature field by using a constant-temperature field system, thereby essentially solving the problem of overlarge temperature drift of the MEMS piezoresistive pressure sensor. The utility model can realize temperature isolation, enables the measurement of the sensor to be more accurate, can be suitable for scenes with larger temperature ranges, and reduces errors caused by temperature drift and the like.

Description

Constant-temperature heating MEMS silicon piezoresistive pressure sensor

Technical Field

The utility model belongs to the technical field of Micro Electro Mechanical Systems (MEMS), and particularly relates to a constant-temperature heating MEMS silicon piezoresistive pressure sensor.

Background

With the development of the micro-electromechanical technology, the MEMS silicon piezoresistive pressure sensor has more and more extensive stress in the fields of aerospace, medical treatment, consumer electronics and the like. Since the packaging structure of the MEMS pressure sensor is very sensitive to temperature thermal stress, when the ambient temperature changes, the output signal of the sensor changes with the temperature change, thereby generating a temperature drift phenomenon and finally causing performance degradation. The reason for this is that the packaging tube shell material of the MEMS pressure sensor is usually a ceramic or metal tube shell, which is not matched with the thermal expansion coefficient of the monocrystalline silicon of the MEMS device, and the temperature change of the environment can cause the thermal stress on the sensitive structure of the MEMS sensor to change dramatically, which finally shows that when the environment temperature changes, the output signal of the device can change with the temperature, and generate temperature drift. In order to improve the performance of MEMS silicon piezoresistive pressure sensors, methods for eliminating temperature drift must be studied. The traditional method for restraining temperature drift usually adopts an external circuit to perform hardware temperature compensation or adopts a DSP and algorithm combined software temperature compensation method, and the hardware temperature compensation usually has higher computational simulation difficulty and low precision because the temperature coefficients of components such as a compensation resistor and the like are unstable. Software temperature compensation is usually limited by the external environment temperature, and electronic components such as a DSP (digital signal processor) cannot normally work in the temperature environment above 125 ℃, so that the software compensation fails.

SUMMERY OF THE UTILITY MODEL

The utility model provides a constant temperature heating MEMS silicon piezoresistive pressure sensor aiming at the defects and requirements in the prior art, a stable temperature field is provided for an MEMS silicon piezoresistive chip by arranging a silicon substrate layer, a heating Pt resistance layer, a metal Al heat sink structure layer and a piezoresistive device layer, and an MEMS sensitive element is isolated from an external temperature field by using a constant temperature field system, so that the problem of overlarge temperature drift of the MEMS piezoresistive pressure sensor is essentially solved. The utility model can realize temperature isolation, enables the measurement of the sensor to be more accurate, can be suitable for scenes with larger temperature ranges, and reduces errors caused by temperature drift and the like.

The specific implementation content of the utility model is as follows:

the utility model provides a constant-temperature heating MEMS silicon piezoresistive pressure sensor, which comprises a silicon substrate layer, a heating Pt resistance layer, a metal Al heat sink structure layer and a piezoresistive device layer which are sequentially arranged from bottom to top;

a pressure sensing cavity is arranged at the bottom of the silicon substrate layer;

the Pt resistors which are uniformly distributed in a ring shape are arranged in the heating Pt resistor layer; cantilever beam structures for stress buffering are arranged on the silicon substrate layer, the heating Pt resistance layer and the metal Al heat sink structure layer around the outer sides of the Pt resistances which are uniformly distributed in an annular mode;

a plurality of through holes are formed in the metal Al heat sink structure layer and the piezoresistive device layer and are positioned at the upper ends of the Pt resistors which are uniformly distributed in an annular mode;

the piezoresistive device layer measures the change of resistance along with external pressure through piezoresistive effect, and is respectively connected with a heating positive electrode VCC + and a heating negative electrode VCC-of a Pt resistor on the heating Pt resistor layer through a through hole.

In order to better implement the utility model, further, the silicon substrate layer comprises a first SOI wafer, and a first insulating layer is grown on the outer layer of the first SOI wafer through thermal oxidation;

etching a pressure sensing cavity on the bottom layer of the first SOI wafer;

the heating Pt resistance layer, the metal Al heat sink structure layer and the piezoresistive device layer are sequentially arranged on the first insulating layer;

the cantilever beam structure is arranged from the upper layer of the first SOI wafer to the metal Al heat sink structure layer.

In order to better implement the present invention, the heat-generating Pt resistor layer further includes a second insulating layer made of SiO filled between and laid on the Pt resistors₂。

In order to better implement the utility model, further, the metal Al heat sink structure layer comprises a metal Al layer sputtered on the second insulating layer, and a SiO layer is deposited on the metal Al layer₂As a third insulating layer;

the cantilever beam structure is a cantilever beam etched by a DRIE etching process from the upper layer of the first SOI wafer to the third insulating layer.

To better practice the utility model, further, the piezoresistive device layer comprises a bottom Si layer of a second SOI wafer connected to a third insulating layer by a Si-Si bonding process, piezoresistive strips etched on the bottom Si layer of the second SOI wafer, and a layer of SiO deposited on the piezoresistive strips₂As a fourth insulating layer, a lead port is etched at a position on the fourth insulating layer corresponding to the piezoresistor strip; a piezoresistor metal lead is arranged on the lead port;

the through hole is formed in the outer side of the lead port, penetrates downwards from the fourth insulating layer to the second insulating layer and exposes the heating positive electrode VCC + and the heating negative electrode VCC-of the Pt resistor.

In order to further realize the present invention, the first SOI wafer is an SOI wafer having a resistivity of 2 to 4 Ω · cm.

In order to realize the present invention, the second SOI wafer is an SOI wafer having a resistivity of 0.002 to 0.005 Ω · cm.

In order to better implement the utility model, further, the pressure sensing cavity is an inward concave trapezoid cavity with a narrow top and a wide bottom, and the angle of the side bevel of the trapezoid cavity is 54.74 °.

The utility model also provides a preparation method of the constant-temperature heating MEMS silicon piezoresistive pressure sensor, which is used for preparing the MEMS silicon piezoresistive pressure sensor and specifically comprises the following steps:

step (ii) of1: selecting a first SOI wafer with double-sided polishing, and growing a layer of SiO on the outer layer of the first SOI wafer by thermal oxidation₂As a first insulating layer; then etching the bottom of the first SOI wafer to form a pressure sensing cavity by a KOH or TMAH wet etching process; etching the cantilever beam structure from the upper layer of the first SOI wafer by a DRIE etching process;

step 2: manufacturing Pt resistors on the first insulating layer through an evaporation or sputtering process, wherein the Pt resistors are arranged in a ring shape and are uniformly distributed and are symmetrical on the first insulating layer; then depositing a layer of SiO between and on the Pt resistors by LPCVD process₂As a second insulating layer;

and step 3: sputtering a metal Al layer on the second insulating layer, and depositing a SiO layer on the metal Al layer by LPCVD process₂As a third insulating layer, the metal Al layer and the third insulating layer are jointly used as a metal Al heat sink structure layer; continuing to form a complete cantilever beam structure on the upper layer of the first SOI wafer by a DRIE etching process until the third insulating layer is formed;

and 4, step 4: selecting a second SOI wafer with two polished surfaces, and connecting the second SOI wafer with a third insulating layer through a Si-Si bonding process; then grinding and polishing the top silicon wafer of the second SOI wafer to only leave the bottom Si layer of the second SOI wafer as the base layer of the piezoresistive device layer; then etching on the bottom Si layer of the second SOI wafer through photoetching and dry etching to form a piezoresistor strip; depositing a layer of SiO on the varistor strips by means of an LPCVD process₂As a fourth insulating layer; etching a lead port at a position on the fourth insulating layer corresponding to the piezoresistor strip, and sputtering metal Al on the lead port to form a piezoresistor metal lead; and a through hole which exposes the heating positive electrode VCC + and the heating negative electrode VCC-of the Pt resistor is formed from the fourth insulating layer to the second insulating layer at the outer side of the lead wire port.

Compared with the prior art, the utility model has the following advantages and beneficial effects:

the utility model provides a constant-temperature heating MEMS silicon piezoresistive pressure sensor, which is characterized in that a heating Pt resistor is integrated in a sensor chip, and a temperature field of a sensitive part of an internal sensor is isolated from an external environment temperature field, so that an effective output signal of the sensor is kept constant, and the defect of overlarge temperature drift of the silicon piezoresistive pressure sensor is essentially overcome. Meanwhile, the process flow is communicated with the traditional MEMS process, and is compatible with the integrated circuit process and easy to integrate.

Drawings

FIG. 1 is a schematic perspective view of an upper layer of the present invention;

FIG. 2 is a schematic perspective view of the bottom surface of the present invention;

FIG. 3 is an exploded view of the present invention

FIG. 4 is a schematic transverse anatomy of a heat generating Pt resistive layer of the present invention;

FIG. 5 is a cross-sectional view of a first SOI wafer according to the present invention;

FIG. 6 is a cross-sectional view of a first insulator layer thermally grown on the first SOI wafer of FIG. 5 in accordance with the present invention;

FIG. 7 is a schematic cross-sectional view of the sputtered Pt resistor of FIG. 6 according to the present invention;

FIG. 8 is a schematic cross-sectional view of a portion of the cantilever structure etched on the basis of FIG. 7 according to the present invention;

FIG. 9 is a cross-sectional view of a second insulating layer formed on the substrate of FIG. 8 according to the present invention;

FIG. 10 is a cross-sectional view of a metal Al layer formed on the second insulating layer based on FIG. 9;

FIG. 11 is a schematic cross-sectional view illustrating a third insulating layer formed on the metallic Al layer based on FIG. 10 according to the present invention;

FIG. 12 is a schematic structural diagram of a second SOI wafer of the present invention;

FIG. 13 is a cross-sectional view of the present invention utilizing the second SOI wafer of FIG. 12 in connection with a Si-Si bonding process based on FIG. 11;

FIG. 14 is a schematic cross-sectional view of the top layer portion of a second SOI wafer after polishing in accordance with the present invention based on FIG. 13;

FIG. 15 is a schematic structural diagram of the present invention etching piezoresistor strips on the bottom Si layer of a second SOI wafer based on FIG. 14;

FIG. 16 is a cross-sectional view of the present invention based on FIG. 15, forming a fourth insulating layer on the bottom Si layer of the second SOI wafer and etching a lead-out opening in the fourth insulating layer;

FIG. 17 is a schematic cross-sectional view of the present invention etching a via hole based on FIG. 16;

FIG. 18 is a cross-sectional view of the metal lead of the piezoresistor formed by sputtering Al metal on the basis of FIG. 17;

FIG. 19 is a schematic cross-sectional view of the pressure sensing cavity etched into the back cavity of the silicon substrate layer and forming a pressure sensing membrane according to the present invention based on FIG. 18;

fig. 20 is a schematic diagram of the material of each layer of the structure shown in fig. 5-19.

Wherein: 1. the silicon substrate layer, 11, a first SOI wafer, 12, a first insulating layer, 13, a pressure sensing cavity, 2, a heating Pt resistance layer, 21, a second insulating layer, 22, a Pt resistance, 23, a heating positive electrode VCC +, 24, a heating negative electrode VCC-, 3, a metal Al heat sink structure layer, 31, a metal Al layer, 32, a third insulating layer, 4, a piezoresistive device layer, 41, a bottom Si layer of the second SOI wafer, 42, a piezoresistive strip, 43, a lead port, 44, a piezoresistive metal lead wire, 45, a fourth insulating layer, 5, a through hole, 6 and a cantilever beam structure.

Detailed Description

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and therefore should not be considered as a limitation to the scope of protection. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example 1:

the utility model provides a constant-temperature heating MEMS silicon piezoresistive pressure sensor, which comprises a silicon substrate layer 1, a heating Pt resistance layer 2, a metal Al heat sink structure layer 3 and a piezoresistive device layer 4 which are sequentially arranged from bottom to top, as shown in figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20;

a pressure sensing cavity 13 is arranged at the bottom of the silicon substrate layer 1;

a Pt resistor which is uniformly distributed in a ring shape is arranged in the heating Pt resistor layer 2; cantilever beam structures 6 for stress buffering are arranged on the silicon substrate layer 1, the heating Pt resistance layer 2 and the metal Al heat sink structure layer 3 around the outer sides of the Pt resistances 22 which are uniformly distributed in an annular mode;

a plurality of through holes 5 are arranged at the upper ends of the Pt resistors 22 which are uniformly distributed in a ring shape on the metal Al heat sink structure layer 3 and the piezoresistive device layer 4;

the piezoresistive device layer 4 measures the change of resistance along with the external pressure through piezoresistive effect, and is respectively connected with a heating positive electrode VCC +23 and a heating negative electrode VCC-24 of a Pt resistor 22 on the heating Pt resistor layer 2 through a through hole 5.

The silicon substrate layer 1 comprises a first SOI wafer 11, and a first insulating layer 12 is grown on the outer layer of the first SOI wafer 11 through thermal oxidation;

etching a pressure sensing cavity 13 on the bottom layer of the first SOI wafer 11; the first SOI wafer 11 is an SOI wafer with the resistivity of 2-4 omega cm;

the heating Pt resistance layer 2, the metal Al heat sink structure layer 3 and the piezoresistive device layer 4 are sequentially arranged on the first insulating layer 12;

the cantilever beam structure 6 is arranged from the upper layer of the first SOI wafer 11 to the metallic Al heat sink structure layer 3.

The heat-generating Pt resistor layer 2 further comprises a second insulating layer 21, wherein the second insulating layer 21 is made of SiO filled between the Pt resistors 22 and laid on the Pt resistors 22₂。

In order to better implement the present invention, further, the metallic Al heat sink structure layer 3 includes a metallic Al layer 31 sputtered on the second insulating layer 21, and a SiO layer is deposited on the metallic Al layer 31₂As the third insulating layer 32;

the cantilever structure 6 is a cantilever beam etched by a DRIE etching process from the upper layer of the first SOI wafer 11 to the third insulating layer 32.

The piezoresistive device layer 4 comprises a bottom Si layer 41 of a second SOI wafer connected to the third insulating layer 32 by a Si-Si bonding process, piezoresistive strips 42 etched on the bottom Si layer 41 of the second SOI wafer, and a layer of SiO deposited on the piezoresistive strips 42₂As a fourth insulating layer 45, lead ports 43 are etched on the fourth insulating layer 45 at positions corresponding to the varistor strips 42; a varistor metal lead 44 is provided on the lead port 43; the second SOI wafer is an SOI wafer with the resistivity of 0.002-0.005 omega-cm;

the through hole 5 is arranged outside the lead port 43 and penetrates downwards from the fourth insulating layer 45 to the second insulating layer 21, and the heating positive electrode VCC +23 and the heating negative electrode VCC-24 of the Pt resistor 22 are exposed.

The pressure sensing cavity 13 is a trapezoid cavity with a narrow upper part and a wide lower part and an inward concave part, and the angle of the side oblique angle of the trapezoid cavity is 54.74 degrees.

The working principle is as follows: the metal Pt 22 is used as a constant temperature heating structure of the sensor, and the metal lead is lapped through the through hole 5. A metal Al layer 31 is sputtered on the constant-temperature heating structure to serve as a heat sink structure, and the temperature field of the whole constant-temperature heating structure is uniformly distributed. And releasing the cantilever beam structure as a stress buffering component when the sensor is heated by a deep silicon etching process. Two pairs of piezoresistor strips 42 are arranged and connected through a piezoresistor metal lead 44 to form a Wheatstone bridge circuit, constant direct-current voltage is accessed through a heating positive electrode VCC +23 and a heating negative electrode VCC-24 to cause the Pt resistor 22 to generate heat energy, and then the heated temperature field of the whole sensor is constant, so that the output voltage of the sensor cannot be subjected to error change caused by temperature change.

Example 2:

the embodiment also provides a method for manufacturing a constant temperature heating MEMS silicon piezoresistive pressure sensor, which is used for manufacturing the above MEMS silicon piezoresistive pressure sensor, and as shown in fig. 1, fig. 2, fig. 3, fig. 4, fig. 5, fig. 6, fig. 7, fig. 8, fig. 9, fig. 10, fig. 11, fig. 12, fig. 13, fig. 14, fig. 15, fig. 16, fig. 17, fig. 18, fig. 19, and fig. 20, the method specifically includes the following steps:

step 1: selecting a first SOI wafer 11 with double-sided polishing, and growing a layer of SiO on the outer layer of the first SOI wafer 11 by thermal oxidation₂As the first insulating layer 13; then, etching the bottom of the first SOI wafer 11 to form a pressure sensing cavity 13 by a KOH or TMAH wet etching process; etching the cantilever beam structure 6 from the upper layer of the first SOI wafer 11 by a DRIE etching process;

step 2: manufacturing Pt resistors 22 on the first insulating layer 13 through an evaporation or sputtering process, wherein the Pt resistors 22 are arranged in a ring shape and are uniformly distributed and are symmetrical on the first insulating layer 13; then a layer of SiO is deposited between the Pt resistors 22 and on the Pt resistors 22 by means of an LPCVD process₂As the second insulating layer 21;

and step 3: sputtering a metallic Al layer 31 on the second insulating layer 21 and depositing a SiO layer on the metallic Al layer 31 by LPCVD process₂As a third insulating layer 32, the metal Al layer 31 and the third insulating layer 32 are used together as the metal Al heat sink structure layer 3; continuing to form a complete cantilever beam structure 6 on the upper layer of the first SOI wafer 11 until the third insulating layer 32 by the DRIE etching process;

and 4, step 4: selecting a second SOI wafer with two polished sides, and bonding the second SOI wafer with Si-SiA bonding process is connected to the third insulating layer 32; then, grinding and polishing the top silicon wafer of the second SOI wafer to only leave the bottom Si layer 41 of the second SOI wafer as the base layer of the piezoresistive device layer 4; then etching on the bottom Si layer 41 of the second SOI wafer through photoetching and dry etching to form a piezoresistor strip 42; depositing a layer of SiO on the varistor strips 42 by means of an LPCVD process₂As the fourth insulating layer 45; etching a lead hole 43 on the fourth insulating layer 45 at a position corresponding to the piezoresistor strip 42, and sputtering metal Al on the lead hole 43 to form a piezoresistor metal lead 44; and a through hole 5 exposing the heat generation positive electrode VCC +23 and the heat generation negative electrode VCC-24 of the Pt resistor 22 is formed from the fourth insulating layer 45 to the second insulating layer 21 through outside the lead port 43.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications and equivalent variations of the above embodiments according to the technical spirit of the present invention are included in the scope of the present invention.

Claims (8)

1. A constant-temperature heating MEMS silicon piezoresistive pressure sensor is characterized by comprising a silicon substrate layer (1), a heating Pt resistance layer (2), a metal Al heat sink structure layer (3) and a piezoresistive device layer (4) which are sequentially arranged from bottom to top;

a pressure sensing cavity (13) is arranged at the bottom of the silicon substrate layer (1);

the heating Pt resistor layer (2) is internally provided with Pt resistors which are uniformly distributed in an annular shape; cantilever beam structures (6) for stress buffering are arranged on the silicon substrate layer (1), the heating Pt resistor layer (2) and the metal Al heat sink structure layer (3) around the outer sides of the Pt resistors (22) which are uniformly distributed in an annular mode;

a plurality of through holes (5) are formed in the metal Al heat sink structure layer (3) and the piezoresistive device layer (4) and are positioned at the upper ends of the Pt resistors (22) which are uniformly distributed in a ring shape;

the piezoresistive device layer (4) measures the change of resistance along with external pressure through piezoresistive effect, and is respectively connected with a heating positive electrode VCC + (23) and a heating negative electrode VCC- (24) of a Pt resistor (22) on the heating Pt resistor layer (2) through a through hole (5).

2. A thermostatically heated MEMS silicon piezoresistive pressure sensor as claimed in claim 1, characterized in that said silicon substrate layer (1) comprises a first SOI wafer (11), a first insulating layer (12) being grown thermally and oxidatively on the outer layer of said first SOI wafer (11);

etching a pressure sensing cavity (13) on the bottom layer of the first SOI wafer (11);

the heating Pt resistance layer (2), the metal Al heat sink structure layer (3) and the piezoresistive device layer (4) are sequentially arranged on the first insulating layer (12);

the cantilever beam structure (6) is arranged from the upper layer of the first SOI wafer (11) to the metal Al heat sink structure layer (3).

3. A thermostatically heated MEMS silicon piezoresistive pressure sensor as claimed in claim 2, characterized in that the heat generating Pt resistive layer (2) further comprises a second insulating layer (21), the second insulating layer (21) being SiO filled between the Pt resistors (22) and laid on the Pt resistors (22)₂。

4. A thermostatically heating MEMS silicon piezoresistive pressure sensor as claimed in claim 3, characterised in that said metallic Al heat sink structure layer (3) comprises a metallic Al layer (31) sputtered on the second insulating layer (21), on top of which metallic Al layer (31) is deposited a layer of SiO (SiO) on top of which layer (31)₂As a third insulating layer (32);

the cantilever beam structure (6) is a cantilever beam etched by a DRIE etching process from the upper layer of the first SOI wafer (11) to the third insulating layer (32).

5. A thermostatically heated MEMS silicon piezoresistive pressure sensor according to claim 4, characterized in that the piezoresistive device layer (4) comprises the bottom Si of a second SOI wafer connected to a third insulating layer (32) by a Si-Si bonding processA layer (41) having piezoresistive strips (42) etched on the bottom Si layer (41) of the second SOI wafer, and a layer of SiO deposited on the piezoresistive strips (42)₂As a fourth insulating layer (45), a lead opening (43) is etched on the fourth insulating layer (45) at a position corresponding to the piezoresistor strip (42); a metal lead (44) of the piezoresistor is arranged on the lead opening (43);

the through hole (5) is formed in the outer side of the lead port (43) and penetrates downwards from the fourth insulating layer (45) to the second insulating layer (21) and exposes the heating positive electrode VCC + (23) and the heating negative electrode VCC- (24) of the Pt resistor (22).

6. A constant temperature heating MEMS silicon piezoresistive pressure sensor according to claim 2, wherein the first SOI wafer (11) is an SOI wafer with a resistivity of 2-4 Ω -cm.

7. A constant temperature heating MEMS silicon piezoresistive pressure sensor according to claim 5, wherein said second SOI wafer is an SOI wafer with resistivity of 0.002-0.005 Ω -cm.

8. A constant temperature heating MEMS silicon piezoresistive pressure sensor as claimed in claim 1, 2, 3, 4, 5, 6 or 7, wherein the pressure sensing cavity (13) is a trapezoidal cavity with narrow top and wide bottom, and the angle of the side bevel of the trapezoidal cavity is 54.74 °.

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