CN113029265A - Vacuum heat-insulation MEMS flow sensor and manufacturing method thereof - Google Patents
Vacuum heat-insulation MEMS flow sensor and manufacturing method thereof Download PDFInfo
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- G—PHYSICS
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- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
- G01F1/6845—Micromachined devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
- G01F1/688—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element
- G01F1/6888—Thermoelectric elements, e.g. thermocouples, thermopiles
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
- G01F1/688—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element
- G01F1/69—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element of resistive type
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Abstract
The invention discloses a vacuum heat-insulating MEMS flow sensor and a manufacturing method thereof, wherein the flow sensor comprises: a substrate provided with a vacuum sealed heat-insulating cavity; the first dielectric layer is formed on the upper surface of the substrate; the heating element, the temperature sensing element and the metal electrode are formed on the upper surface of the first medium layer, wherein the temperature sensing element is symmetrically distributed on two sides of the heating element, and the heating element and the temperature sensing element are locally positioned above the heat insulation cavity; and the second dielectric layer covers the heating element, the temperature sensing element, the metal electrode and the through hole, and a contact hole is partially etched. The MEMS flow sensor forms the vacuum closed heat insulation cavity by utilizing the 'shape-preserving effect' of the low-pressure chemical vapor deposition method, on one hand, the heat insulation performance of the heat insulation cavity can be improved, on the other hand, the convection heat loss between the measured fluid and the heat insulation cavity can be reduced, so that the power consumption of a device is favorably reduced, the temperature difference between an upstream temperature sensing element and a downstream temperature sensing element is increased, and the sensitivity of the device is effectively improved.
Description
Technical Field
The invention belongs to the technical field of flow measurement, and particularly relates to a vacuum heat-insulating MEMS flow sensor and a manufacturing method thereof.
Background
Flow measurement is a fundamental requirement for industrial production and scientific research. The flow sensors are widely available, and among them, the thermal differential flow sensors manufactured based on the MEMS technology are widely used because of their advantages of simple structure, small size, high precision, fast response, low power consumption, etc. The MEMS thermal differential temperature type flow sensor chip mainly comprises three elements integrated on the same substrate: a centrally located heating element and temperature sensing elements (typically thermopiles) symmetrically distributed upstream and downstream of the heating element. The heating element provides certain power to enable the surface temperature of the chip to be higher than the ambient temperature, when no gas flows, the surface temperature of the chip is normally distributed by taking the heating element as the center, and the upstream temperature sensing element and the downstream temperature sensing element have the same electric signal; when gas flows, the temperature distribution on the surface of the chip is deviated by the heat transferred by gas molecules, the electric signals of the upstream and downstream temperature sensing elements are different, and the flow can be calculated by utilizing the difference.
For the important indexes of the flow sensor, the power consumption and the sensitivity are three main technical schemes: the suspended membrane structure with low thermal conductivity is adopted to reduce the heat loss of the substrate; a thermoelectric material with a higher seebeck coefficient is adopted; the logarithm of the thermoelectric stack is increased by adopting larger chip area or a denser arrangement mode. However, with the increasing popularization and penetration of applications, the requirements for power consumption and sensitivity of the flow sensor are further increased.
Disclosure of Invention
In order to solve the technical problems, the invention provides a vacuum heat-insulation MEMS flow sensor and a manufacturing method thereof, and the purposes of reducing heat loss and reducing the power consumption of a device are achieved by forming a vacuum closed heat-insulation cavity, and meanwhile, the temperature difference between an upstream temperature sensing element and a downstream temperature sensing element is increased, and the sensitivity of the device is effectively improved.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a vacuum insulated MEMS flow sensor, comprising:
the heat insulation device comprises a substrate and a heat insulation layer, wherein the substrate is provided with a heat insulation cavity which is formed by inwards recessing the upper surface of the substrate; a sacrificial layer is deposited on the upper surface of the substrate, and the heat insulation cavity is arranged in the sacrificial layer and is formed by inwards recessing the upper surface of the sacrificial layer; the sacrificial layer is made of one of silicon oxide, silicon nitride, polycrystalline silicon and amorphous silicon;
the first dielectric layer is formed on the upper surface of the substrate, and a plurality of through holes which are uniformly distributed are formed on the first dielectric layer through local etching;
the heating element is formed on the upper surface of the first medium layer and is locally positioned above the heat insulation cavity; the heating element is made of one of P-type polycrystalline silicon, N-type polycrystalline silicon and metal;
the temperature sensing elements are formed on the upper surface of the first medium layer, symmetrically distributed on two sides of the heating element and locally positioned above the heat insulation cavity;
the metal electrode is formed on the upper surface of the first dielectric layer;
and the second dielectric layer covers the heating element, the temperature sensing element, the metal element and the through hole, enables the heat insulation cavity to form a vacuum closed state, and forms a contact hole exposing part of the metal electrode on the second dielectric layer through local etching.
In the above scheme, the substrate is a semiconductor substrate, and includes one of a silicon substrate, a germanium substrate, an SOI substrate, and a GeOI substrate.
In the scheme, a sacrificial layer is deposited on the upper surface of the substrate, and the heat insulation cavity is arranged in the sacrificial layer and is formed by inwards recessing the upper surface of the sacrificial layer; the sacrificial layer is made of one of silicon oxide, silicon nitride, polycrystalline silicon and amorphous silicon.
In the above scheme, the material of the first dielectric layer is one or a combination of two of silicon oxide and silicon nitride.
In the above scheme, the material of the heating element is one of P-type polysilicon, N-type polysilicon, and metal.
In the above scheme, the temperature sensing element is a thermistor or a thermopile; the material of the thermistor is metal with positive/negative temperature coefficients, and the material of the thermopile is a combination of P-type polycrystalline silicon/N-type polycrystalline silicon, or a combination of P-type polycrystalline silicon/metal, or a combination of N-type polycrystalline silicon/metal.
In the above scheme, the metal electrode is made of one or a combination of titanium, tungsten, chromium, platinum, aluminum and gold.
In the above scheme, the shape of the through hole includes one of a circle, a rectangle and a cross.
In the above scheme, the second dielectric layer is made of silicon oxide or silicon nitride formed by a low-pressure chemical vapor deposition method.
The invention also provides a manufacturing method of the vacuum heat-insulation MEMS flow sensor, which comprises the following steps:
s1, providing a substrate, and forming a first dielectric layer on the substrate;
s2, forming a heating element, a temperature sensing element and a metal electrode on the first medium layer;
s3, locally etching the first dielectric layer to form through holes which are uniformly distributed;
s4, releasing the substrate through the through hole to form a heat insulation cavity;
s5, forming a second medium layer by adopting a low-pressure chemical vapor deposition method, covering the heating element, the temperature sensing element, the metal electrode and the through hole, and enabling the heat insulation cavity to form a vacuum closed state;
and S6, locally etching the second dielectric layer to form a contact hole, and exposing a part of the metal electrode.
Through the technical scheme, the vacuum heat-insulating MEMS flow sensor and the manufacturing method thereof provided by the invention have the following beneficial effects:
1. the thermal temperature difference type flow sensor manufactured based on the MEMS technology has the advantages of small volume, quick response, low power consumption, high stability and the like, and is simple in preparation process, strong in controllability and compatible with the existing mature micro-processing technology.
2. Compared with the common heat insulation cavity in the existing flow sensor, the vacuum sealed heat insulation cavity is formed based on the 'shape-preserving effect' in the low-pressure chemical vapor deposition method, the heat loss of the heating element can be effectively reduced, and then a larger temperature difference is generated between the upstream temperature sensing element and the downstream temperature sensing element, and the reasons include two aspects: firstly, the reduction of the gas density reduces the collision probability of gas molecules, and the heat transferred by the collision of the gas molecules is also reduced, namely, the heat insulation performance of the heat insulation cavity is further improved; secondly, the through hole is closed, so that the heat convection between the measured fluid and the heat insulation cavity can be avoided, and the heat convection loss is greatly reduced. Therefore, the MEMS flow sensor with the vacuum sealed heat insulation cavity can effectively reduce power consumption and improve sensitivity.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below.
FIG. 1a is a schematic cross-sectional view of a low pressure CVD deposition process for depositing a material with an excessive via width without "conformal effect";
FIG. 1b is a schematic cross-sectional view of a "conformal effect" occurring when a low pressure chemical vapor deposition process is applied to deposit a material with a suitable via width;
FIG. 2 is a schematic flow chart of a vacuum-insulated MEMS flow sensor chip and a method for fabricating the same according to an embodiment of the present invention;
FIG. 3 is a schematic cross-sectional view of the structure obtained in step S1 of the method disclosed in the present invention;
FIG. 4 is a schematic cross-sectional view of the structure obtained in step S2 of the method disclosed in the present invention;
FIG. 5 is a schematic cross-sectional view of the structure obtained in step S3 of the method disclosed in the present invention;
FIG. 6 is a schematic cross-sectional view of the structure obtained in step S4 of the method disclosed in the present invention;
FIG. 7 is a schematic cross-sectional view of the structure obtained in step S5 of the method disclosed in the present invention;
FIG. 8 is a schematic cross-sectional view of the structure obtained in step S6 of the disclosed manufacturing method according to one embodiment of the present invention;
FIG. 9 is a schematic cross-sectional view of the structure obtained in step S6 of the second embodiment of the present invention;
fig. 10 is a schematic cross-sectional view of the structure obtained in step S6 in the method disclosed in the third embodiment of the present invention.
In the figure, 10, a substrate; 20. a first dielectric layer; 31. a heating element; 32. a temperature sensing element; 33. a metal electrode; 40. a through hole; 50. a second dielectric layer; 60. a contact hole; 90. a sacrificial layer; 100. a thermally insulated cavity.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
The invention provides a vacuum heat-insulating MEMS flow sensor, which comprises:
a substrate 10 provided with a heat insulating chamber 100, the heat insulating chamber 100 being formed by recessing an upper surface of the substrate 10 inward;
the first dielectric layer 20 is formed on the upper surface of the substrate 10, and a plurality of through holes 40 which are uniformly distributed are formed on the first dielectric layer by local etching;
a heating element 31 formed on the upper surface of the first dielectric layer 20 and partially located above the insulating cavity 100;
the temperature sensing elements 32 are formed on the upper surface of the first medium layer 20, symmetrically distributed on two sides of the heating element 31, and partially located above the heat insulation cavity 100;
a metal electrode 33 formed on the upper surface of the first dielectric layer 20;
the second dielectric layer 50 covers the heating element 31, the temperature sensing element 32, the metal element 33 and the through hole 40, the heat insulation cavity 100 is in a vacuum sealing state, and a contact hole 60 exposing a part of the metal electrode 33 is formed on the second dielectric layer 50 through partial etching.
It should be noted that the principle of forming the vacuum-tight heat-insulating chamber 100 is as follows: the second dielectric layer 20 is formed by a low pressure chemical vapor deposition method, on one hand, the gas density in the thermal insulation cavity 100 is reduced by the low pressure deposition process, and on the other hand, the dielectric layer material formed by the method generates a "conformal effect" at the through hole 40, please refer to fig. 1a and fig. 1b, the width of the through hole 40 is properly set, and finally, the through hole 40 can be sealed, so that a vacuum sealing state is formed in the thermal insulation cavity 100.
It should be noted that, compared with the common thermal insulation cavity in the existing flow sensor, the vacuum-tight thermal insulation cavity can effectively reduce the heat loss of the heating element, and further generate a larger temperature difference between the upstream and downstream temperature sensing elements, and the reason thereof includes two aspects: firstly, the reduction of the gas density reduces the collision probability of gas molecules, and the heat transferred by the collision of the gas molecules is also reduced, namely, the heat insulation performance of the heat insulation cavity is further improved; secondly, the through hole is closed, so that the heat convection between the measured fluid and the heat insulation cavity can be avoided, and the heat convection loss is greatly reduced. Therefore, the vacuum sealed heat insulation cavity is beneficial to reducing the power consumption of the device and improving the sensitivity of the device.
Specifically, the substrate 10 is a common semiconductor substrate including, but not limited to, one of a silicon substrate, a germanium substrate, an SOI substrate, a GeOI substrate. Referring to fig. 8, in the first embodiment of the present invention, the substrate 10 is a single crystal silicon substrate; referring to fig. 9, in the second embodiment of the present invention, the substrate 10 is an SOI substrate.
It should be noted that, optionally, a sacrificial layer 90 is first deposited on the substrate 10, and then other structures are fabricated on the sacrificial layer 90, at this time, the thermal insulation cavity 100 is disposed in the sacrificial layer 90 and is formed by recessing the upper surface of the sacrificial layer 90 inward; the material of the sacrificial layer 90 is one of silicon oxide, silicon nitride, polysilicon, and amorphous silicon. Referring to fig. 10, in a third embodiment of the present invention, a sacrificial layer 90 of polysilicon is first deposited on a single-crystal silicon substrate 10.
It should be noted that, for convenience of description, the substrate deposited with the sacrificial layer 90 is still referred to as the substrate 10.
Specifically, the material of the first dielectric layer 20 is one or a combination of two of silicon oxide and silicon nitride; in the embodiment of the present invention, the first dielectric layer 20 is formed by compounding silicon oxide and silicon nitride.
Specifically, the material of the heating element 31 is one of P-type polysilicon, N-type polysilicon, and metal; in an embodiment of the present invention, the material of the heating element 31 is platinum.
Specifically, the temperature-sensing element 32 may be a thermistor, or a thermopile; the material of the thermistor is metal with positive/negative temperature coefficients, and the material of the thermopile is a combination of P-type polycrystalline silicon/N-type polycrystalline silicon, or a combination of P-type polycrystalline silicon/metal, or a combination of N-type polycrystalline silicon/metal; in the embodiment of the present invention, the temperature sensing element 32 employs a platinum thermistor.
Specifically, the material of the metal electrode 33 is one or a combination of more of titanium, tungsten, chromium, platinum, aluminum and gold; in an embodiment of the present invention, the material of the metal layer 33 is platinum.
Specifically, the through holes 40 are uniformly distributed, and the shape thereof includes, but is not limited to, one of a circle, a rectangle, and a cross; in the embodiment of the present invention, the shape of the through-hole 40 is circular.
Specifically, the material of the second dielectric layer 50 is silicon oxide or silicon nitride formed by a low-pressure chemical vapor deposition method; in an embodiment of the present invention, the material of the second dielectric layer 50 is silicon oxide formed by low pressure chemical vapor deposition.
The invention also provides a manufacturing method of the vacuum heat-insulation MEMS flow sensor, as shown in FIG. 2, comprising the following steps:
s1, providing a substrate 10, and forming a first dielectric layer 20 on the substrate 10, as shown in fig. 3;
specifically, the material of the first dielectric layer 20 is one or two combinations of silicon oxide and silicon nitride, wherein the silicon oxide can be formed by thermal oxidation, low-pressure chemical vapor deposition, and plasma chemical vapor deposition, and the silicon nitride can be formed by low-pressure chemical vapor deposition, and plasma chemical vapor deposition; in an embodiment of the present invention, the first dielectric layer 20 is formed by combining silicon oxide and silicon nitride, wherein the silicon oxide is formed by thermal oxidation and the silicon nitride is formed by low pressure chemical vapor deposition.
Specifically, the substrate 10 is a common semiconductor substrate including, but not limited to, one of a silicon substrate, a germanium substrate, an SOI substrate, a GeOI substrate. Referring to fig. 8, in the first embodiment of the present invention, the substrate 10 is a single crystal silicon substrate; referring to fig. 9, in the second embodiment of the present invention, the substrate 10 is an SOI substrate.
It should be noted that, alternatively, a sacrificial layer 90 is first deposited on the substrate 10, and the subsequent steps are performed on the sacrificial layer 90; the sacrificial layer 90 is made of one of silicon oxide, silicon nitride, polysilicon, and amorphous silicon, and is formed by chemical vapor deposition, physical vapor deposition, liquid phase epitaxy, or the like. Referring to fig. 10, in a third embodiment of the present invention, a sacrificial layer 90 of polysilicon is first deposited on a single crystal silicon substrate 10 by low pressure chemical vapor deposition.
S2, forming the heating element 31, the temperature sensing element 32 and the metal electrode 33 on the second dielectric layer 30, as shown in fig. 4;
specifically, the material of the heating element 31 is one of P-type polysilicon, N-type polysilicon, and metal, the temperature sensing element 32 may be a thermistor (whose material is metal with positive/negative temperature coefficient), or may be a thermopile (whose material is a combination of P-type polysilicon/N-type polysilicon, or a combination of P-type polysilicon/metal, or a combination of N-type polysilicon/metal), and the material of the metal electrode 33 is one or more combinations of titanium, tungsten, chromium, platinum, aluminum, and gold; wherein, the P-type polysilicon or N-type polysilicon is formed by the combination of LPCVD, ion implantation, annealing, etching and other processes; the metal is formed by a stripping process or a method of sputtering or evaporation and then etching; in the embodiment of the present invention, the heating element 31, the temperature sensing element 32 and the metal element 33 are made of platinum and are formed simultaneously by a peeling process.
S3, performing local etching on the first dielectric layer 30 to form through holes 40 uniformly distributed, as shown in fig. 5;
specifically, the through hole 40 may be formed by plasma etching, ion beam etching, reactive ion etching, or the like, and the shape thereof includes, but is not limited to, one of circular, rectangular, and cross-shaped; in the embodiment of the present invention, the circular via hole 40 is formed by a reactive ion etching method.
S4, releasing the substrate 10 from the through hole to form an insulating cavity 100, as shown in fig. 6;
specifically, the heat insulation cavity 100 may be formed by wet etching, dry etching, or the like; in the first embodiment shown in fig. 8, the heat insulating cavity 100 is formed in the single crystal silicon substrate 10; in the second embodiment shown in fig. 9, the insulating cavity 100 is formed in the top silicon of the SOI substrate 10; in the third embodiment shown in fig. 10, the heat insulating cavity 100 is formed in the sacrificial layer 90 on the single crystal silicon substrate 10; in all three embodiments of the present invention, XeF is used2The method of isotropic dry etching forms the insulating cavity 100.
S5, forming a second dielectric layer 50 by low pressure chemical vapor deposition, covering the heating element 31, the temperature sensing element 32, the metal electrode 33 and the through hole 40, and forming the heat insulating cavity 100 in a vacuum-tight state, as shown in fig. 7;
specifically, the material of the second dielectric layer 50 is one or two of silicon oxide and silicon nitride, and is formed by a low-pressure chemical vapor deposition method; in an embodiment of the present invention, the material of the second dielectric layer 50 is silicon oxide formed by low pressure chemical vapor deposition.
The principle of forming the heat insulating cavity 100 in a vacuum-tight state by the low-pressure chemical vapor deposition method is as follows: on the one hand, the low pressure deposition process reduces the gas density in the insulating cavity 100, and on the other hand, the dielectric layer material formed by this method has a "conformal effect" at the through holes 40, eventually sealing the through holes 40.
S6, partially etching the second dielectric layer 50 to form a contact hole 60 exposing a portion of the metal electrode 33, as shown in fig. 8-10;
specifically, the contact hole 70 may be formed by plasma etching, ion beam etching, reactive ion etching, or the like, and the shape thereof includes, but is not limited to, one of circular, rectangular, and cross-shaped; in the embodiment of the present invention, the rectangular via hole 40 is formed by a reactive ion etching method.
Therefore, the thermal temperature difference type flow sensor manufactured based on the MEMS technology has the advantages of small volume, quick response, low power consumption, high stability and the like, is simple in preparation process and strong in controllability, and is compatible with the existing mature micro-processing technology; compared with the common heat insulation cavity in the existing flow sensor, the vacuum sealed heat insulation cavity is formed based on the 'shape-preserving effect' in the low-pressure chemical vapor deposition method, the heat loss of the heating element can be effectively reduced, and then a larger temperature difference is generated between the upstream temperature sensing element and the downstream temperature sensing element, and the reasons include two aspects: firstly, the reduction of the gas density reduces the collision probability of gas molecules, and the heat transferred by the collision of the gas molecules is also reduced, namely, the heat insulation performance of the heat insulation cavity is further improved; secondly, the through hole is closed, so that the heat convection between the measured fluid and the heat insulation cavity can be avoided, and the heat convection loss is greatly reduced. Therefore, the MEMS flow sensor with the vacuum sealed heat insulation cavity can effectively reduce power consumption and improve sensitivity.
Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (8)
1. A vacuum insulated MEMS flow sensor, comprising:
the heat insulation device comprises a substrate and a heat insulation layer, wherein the substrate is provided with a heat insulation cavity which is formed by inwards recessing the upper surface of the substrate; a sacrificial layer is deposited on the upper surface of the substrate, and the heat insulation cavity is arranged in the sacrificial layer and is formed by inwards recessing the upper surface of the sacrificial layer; the sacrificial layer is made of one of silicon oxide, silicon nitride, polycrystalline silicon and amorphous silicon;
the first dielectric layer is formed on the upper surface of the substrate, and a plurality of through holes which are uniformly distributed are formed on the first dielectric layer through local etching;
the heating element is formed on the upper surface of the first medium layer and is locally positioned above the heat insulation cavity; the heating element is made of one of P-type polycrystalline silicon, N-type polycrystalline silicon and metal;
the temperature sensing elements are formed on the upper surface of the first medium layer, symmetrically distributed on two sides of the heating element and locally positioned above the heat insulation cavity;
the metal electrode is formed on the upper surface of the first dielectric layer;
and the second dielectric layer covers the heating element, the temperature sensing element, the metal element and the through hole, enables the heat insulation cavity to form a vacuum closed state, and forms a contact hole exposing part of the metal electrode on the second dielectric layer through local etching.
2. The vacuum insulated MEMS flow sensor of claim 1 wherein the substrate is a semiconductor substrate comprising one of a silicon substrate, a germanium substrate, an SOI substrate, a GeOI substrate.
3. The vacuum insulated MEMS flow sensor of claim 1, wherein the material of the first dielectric layer is one or a combination of silicon oxide and silicon nitride.
4. The vacuum insulated MEMS flow sensor of claim 1, wherein the temperature sensing element is a thermistor or a thermopile; the material of the thermistor is metal with positive/negative temperature coefficients, and the material of the thermopile is a combination of P-type polycrystalline silicon/N-type polycrystalline silicon, or a combination of P-type polycrystalline silicon/metal, or a combination of N-type polycrystalline silicon/metal.
5. The vacuum insulated MEMS flow sensor of claim 1, wherein the metal electrode is made of one or more of titanium, tungsten, chromium, platinum, aluminum, and gold.
6. The vacuum insulated MEMS flow sensor of claim 1, wherein the via shape comprises one of a circle, a rectangle, and a cross-hair shape.
7. The vacuum insulated MEMS flow sensor of claim 1, wherein the second dielectric layer is formed of silicon oxide or silicon nitride by low pressure chemical vapor deposition.
8. A method of fabricating a vacuum insulated MEMS flow sensor as claimed in claim 1, comprising the steps of:
s1, providing a substrate, and forming a first dielectric layer on the substrate;
s2, forming a heating element, a temperature sensing element and a metal electrode on the first medium layer;
s3, locally etching the first dielectric layer to form through holes which are uniformly distributed;
s4, releasing the substrate through the through hole to form a heat insulation cavity;
s5, forming a second medium layer by adopting a low-pressure chemical vapor deposition method, covering the heating element, the temperature sensing element, the metal electrode and the through hole, and enabling the heat insulation cavity to form a vacuum closed state;
and S6, locally etching the second dielectric layer to form a contact hole, and exposing a part of the metal electrode.
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Application publication date: 20210625 Assignee: Suzhou Taichu Microelectronics Technology Co.,Ltd. Assignor: Qingdao Xinsheng micro nano electronic technology Co.,Ltd. Contract record no.: X2023980044029 Denomination of invention: A MEMS flow sensor with vacuum insulation and its manufacturing method Granted publication date: 20221101 License type: Common License Record date: 20231020 |