CN112938892A - Porous silicon heat-insulating support high-temperature heat flow sensor and preparation method thereof - Google Patents
Porous silicon heat-insulating support high-temperature heat flow sensor and preparation method thereof Download PDFInfo
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- 229910021426 porous silicon Inorganic materials 0.000 title claims abstract description 81
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 56
- 229910052751 metal Inorganic materials 0.000 claims abstract description 56
- 239000002184 metal Substances 0.000 claims abstract description 56
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 56
- 239000010703 silicon Substances 0.000 claims abstract description 56
- 239000000758 substrate Substances 0.000 claims abstract description 37
- 238000009413 insulation Methods 0.000 claims abstract description 22
- 239000011248 coating agent Substances 0.000 claims abstract description 21
- 238000000576 coating method Methods 0.000 claims abstract description 21
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims abstract description 13
- 229910010271 silicon carbide Inorganic materials 0.000 claims abstract description 13
- 238000000034 method Methods 0.000 claims description 43
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 40
- 229920005591 polysilicon Polymers 0.000 claims description 32
- 230000008569 process Effects 0.000 claims description 26
- 238000005530 etching Methods 0.000 claims description 19
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 16
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 16
- 238000001312 dry etching Methods 0.000 claims description 15
- 238000004518 low pressure chemical vapour deposition Methods 0.000 claims description 9
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 6
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 5
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 3
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 3
- 229910052804 chromium Inorganic materials 0.000 claims description 3
- 239000011651 chromium Substances 0.000 claims description 3
- 238000000151 deposition Methods 0.000 claims description 3
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 3
- 229910052737 gold Inorganic materials 0.000 claims description 3
- 239000010931 gold Substances 0.000 claims description 3
- 238000005468 ion implantation Methods 0.000 claims description 3
- 229910021421 monocrystalline silicon Inorganic materials 0.000 claims description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 2
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- 238000001755 magnetron sputter deposition Methods 0.000 claims description 2
- 238000001451 molecular beam epitaxy Methods 0.000 claims description 2
- 229910052697 platinum Inorganic materials 0.000 claims description 2
- 238000004544 sputter deposition Methods 0.000 claims description 2
- 229910052719 titanium Inorganic materials 0.000 claims description 2
- 239000010936 titanium Substances 0.000 claims description 2
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 2
- 229910052721 tungsten Inorganic materials 0.000 claims description 2
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- 238000001039 wet etching Methods 0.000 claims description 2
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
- B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B2201/00—Specific applications of microelectromechanical systems
- B81B2201/02—Sensors
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Abstract
The invention discloses a high-temperature heat flow sensor supported by porous silicon thermal insulation and a preparation method thereof, wherein the heat flow sensor comprises: a silicon substrate; porous silicon formed on top of the silicon substrate; a first insulating layer covering the upper surfaces of the silicon substrate and the porous silicon; the resistor strip is positioned on the first insulating layer; the second insulating layer at least covers the upper surface and the side surfaces of the resistor strip and is locally etched to form a contact hole; the metal layer is positioned on the second insulating layer, part of the metal layer is positioned above the porous silicon, and part of the metal layer is connected with the resistor strip through the contact hole; and the high-temperature resistant coating covers the second insulating layer and the metal layer and is partially etched to expose part of the metal layer. The high-temperature heat flow sensor based on the micro-mechanical thermocouple/thermopile has small volume, high sensitivity and high response speed, forms a heat insulation supporting structure by utilizing thicker porous silicon, forms a high-temperature resistant coating by utilizing silicon carbide, and can remarkably improve the survival capability and the mechanical stability of the high-temperature heat flow sensor while ensuring the heat insulation performance of the hot end of the device.
Description
Technical Field
The invention belongs to the technical field of heat flow measurement, and particularly relates to a porous silicon heat-insulating supported high-temperature heat flow sensor and a preparation method thereof.
Background
Nature andin the production process, a large amount of heat transfer problems exist. With the development of modern science and technology, it is far from enough to use temperature as the basis for researching heat transfer, so that the theory and technology of heat flow measurement are more and more emphasized, and the heat flow sensor is also greatly developed. At present, a heat flow sensor can meet the general measurement requirements of industrial and agricultural production, but the heat flow sensor is usually large in volume and has the problems of poor heat resistance, low sensitivity, long response time and the like. In high temperature harsh environments such as aerospace, power engineering, etc., the temperature and heat flux density is typically up to thousands of degrees celsius and several MW/m2The existing heat flow sensor is difficult to realize rapid and accurate measurement.
The micro-mechanical thermocouple/thermopile manufactured by adopting the MEMS technology has the unique advantages of small volume, high sensitivity, high response speed and the like, and can be used for measuring high-temperature heat flow. The fabrication of such high temperature heat flux sensors typically requires etching the substrate from the front or back to create a localized suspended membrane structure (cantilever structure or closed membrane structure) to thermally insulate the hot end of the thermocouple/thermopile. However, the mechanical stability of the suspended film is poor, on one hand, because the stress is difficult to control in the manufacturing process, and on the other hand, when the working temperature is high and the heat flux density is high, a high temperature of several hundreds or even thousands of degrees celsius is generated on the suspended film, and such a high temperature easily causes the film to deform or even break, and finally leads to the failure of the device.
Therefore, how to make the MEMS high-temperature heat flow sensor have good hot end thermal insulation performance and mechanical stability at the same time is a technical problem to be solved urgently at present.
Disclosure of Invention
In order to solve the technical problems, the invention provides the high-temperature heat flow sensor with the porous silicon heat insulation support and the preparation method thereof, so that the high-temperature heat flow sensor has good hot end heat insulation performance and high mechanical strength, and is more stably used for quickly and accurately measuring high-temperature heat flow.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a porous silicon adiabatically supported high temperature heat flow sensor comprising:
a silicon substrate;
porous silicon formed inward from a top local area of the silicon substrate;
a first insulating layer covering the silicon substrate and the upper surface of the porous silicon;
the resistor strip is positioned on the first insulating layer and is locally positioned above the porous silicon;
the second insulating layer at least covers the upper surface and the side faces of the resistor strip and is locally etched to form a contact hole with the resistor strip;
the metal layer is positioned on the second insulating layer and is partially positioned above the porous silicon, and part of the metal layer is connected with the resistance strip through the contact hole so as to form a thermocouple/thermopile;
and the high-temperature resistant coating covers the second insulating layer and the metal layer and is partially etched to expose part of the metal layer.
In a further technical scheme, a back cavity is formed in the lower surface of the silicon substrate, and the back cavity is stopped at the lower surface of the porous silicon.
Preferably, the resistor strips comprise N-type doped polysilicon resistor strips and P-type doped polysilicon resistor strips, the N-type doped polysilicon resistor strips and the P-type doped polysilicon resistor strips are alternately connected through the metal layer to form thermocouples/thermopiles, the number of pairs of the thermocouples is one, and the number of pairs of the thermopiles is at least two.
Preferably, the resistor strips are N-type doped polysilicon resistor strips or P-type doped polysilicon resistor strips, the N-type doped polysilicon resistor strips or the P-type doped polysilicon resistor strips are alternately connected with the metal layer to form thermocouples/thermopiles, the number of pairs of the thermocouples is one, and the number of pairs of the thermopiles is at least two.
In the above scheme, the silicon substrate is a P-type doped monocrystalline silicon wafer, and the doping concentration is not less than 7 × 1016cm-3(ii) a The porosity of the porous silicon is not less than 30%, and the thickness of the porous silicon is 10-80 mu m; the materials of the first insulating layer and the second insulating layer are silicon oxide andthe material of the metal layer is one or a combination of more of titanium, tungsten, chromium, platinum, aluminum and gold, and the material of the high-temperature resistant coating is silicon carbide; the shape of the contact hole is circular, polygonal or cross-shaped; the cross section of the back cavity is rectangular or trapezoidal.
The invention also provides a preparation method of the porous silicon heat insulation supported high-temperature heat flow sensor, which comprises the following steps:
1) providing a silicon substrate, and forming a silicon-rich silicon nitride mask layer with a window on the upper surface of the silicon substrate;
2) forming porous silicon inwards at a window on the upper surface of the silicon substrate, and then removing the silicon-rich silicon nitride mask layer;
3) forming a first insulating layer on the silicon substrate and the upper surface of the porous silicon;
4) depositing polycrystalline silicon on the first insulating layer, and doping and etching the polycrystalline silicon to form a resistor strip which is locally positioned above the porous silicon;
5) forming a second insulating layer on the first insulating layer and the resistor strip, and etching the second insulating layer to form a contact hole communicated with the resistor strip;
6) forming a metal layer on the surface of the second insulating layer, wherein part of the metal layer is connected with the resistor strip through the contact hole;
7) and forming a high-temperature-resistant coating on the surfaces of the second insulating layer and the metal layer, and etching the high-temperature-resistant coating to expose part of the metal layer, namely the electrode.
In a further technical scheme, the method also comprises the following steps: and forming a back cavity inwards on the lower surface of the silicon substrate, wherein the back cavity is stopped at the lower surface of the porous silicon.
In the scheme, in the step 1), the silicon-rich silicon nitride mask layer is formed by adopting low-pressure chemical vapor deposition or plasma enhanced chemical vapor deposition, and the window is formed by adopting a dry etching process; in the step 2), forming the porous silicon by adopting an electrochemical corrosion method; and removing the silicon-rich silicon nitride mask layer by adopting a phosphoric acid solution.
In the above scheme, in step 3) and step 5), the first insulating layer and the second insulating layer are formed by low-pressure chemical vapor deposition and/or plasma-enhanced chemical vapor deposition, the first insulating layer and the second insulating layer are made of silicon oxide and/or silicon nitride, and the contact hole is formed by a dry etching process.
In the scheme, in the step 4), the polycrystalline silicon is formed by adopting low-pressure chemical vapor deposition, the polycrystalline silicon is doped by adopting an ion implantation process, and the resistor strips are formed by adopting an inductively coupled plasma etching process; in the step 6), a metal stripping process is adopted to form the metal layer, or a method of firstly sputtering metal or evaporating metal and then etching is adopted to form the metal layer; in the step 7), one of a chemical vapor deposition method, a magnetron sputtering method and a molecular beam epitaxy method is adopted to form the high-temperature-resistant coating, and a dry etching process is adopted to etch the high-temperature-resistant coating; and forming the back cavity by adopting one of anisotropic wet etching, isotropic wet etching or dry etching.
Through the technical scheme, the porous silicon heat insulation supported high-temperature heat flow sensor and the preparation method thereof provided by the invention have the following beneficial effects:
1. the heat flow sensor manufactured based on the MEMS technology has the advantages of small volume, high sensitivity, high response speed, simple preparation process and strong controllability, and is compatible with the existing mature microelectronic process.
2. Compared with a suspended membrane, the porous silicon support structure has high mechanical stability and is not easy to deform or even crack, and meanwhile, the porous silicon has thermal conductivity far lower than that of bulk silicon (when the porosity of the porous silicon is more than 30%, the thermal conductivity of the porous silicon is reduced by nearly 3 orders of magnitude compared with that of the bulk silicon). Therefore, the invention uses thicker porous silicon to form a heat insulation support structure, and can remarkably improve the mechanical stability of the device while ensuring the heat insulation performance of the hot end of the thermocouple/thermopile.
3. The invention adopts the silicon carbide as the high-temperature resistant coating, and has the following advantages: the silicon carbide has high melting point and good heat resistance, and can keep stable chemical properties at ultrahigh temperature; the silicon carbide has high thermal conductivity, and can quickly dissipate a large amount of heat caused by ultrahigh temperature and large heat flow, thereby protecting a silicon-based structure and improving the survival capability and mechanical stability of devices; the silicon carbide also has good mechanical property and chemical property, and is beneficial to improving the wear resistance and corrosion resistance of the device.
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. 1 is a schematic flow chart of a method for manufacturing a porous silicon adiabatic-supported high-temperature heat flow sensor according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of the step S1 in the method of manufacturing disclosed in the embodiments of the present invention;
FIG. 3 is a schematic structural diagram of the step S2 in the method of manufacturing disclosed in the embodiments of the present invention;
FIG. 4 is a schematic structural diagram of the step S3 in the method of manufacturing disclosed in the embodiments of the present invention;
FIG. 5a is a schematic structural diagram of the structure obtained in step S4 of the disclosed manufacturing method according to an embodiment of the invention;
FIG. 5b is a schematic structural diagram of the structure obtained in step S4 of the second embodiment of the present invention;
FIG. 6a is a schematic structural diagram of the structure obtained in step S5 of the disclosed manufacturing method according to an embodiment of the invention;
FIG. 6b is a schematic structural diagram of the structure obtained in step S5 of the second embodiment of the present invention;
FIG. 7a is a schematic structural diagram of the structure obtained in step S6 of the disclosed manufacturing method according to an embodiment of the invention;
FIG. 7b is a schematic structural diagram of the structure obtained in step S6 of the second embodiment of the present invention;
FIG. 8a is a schematic structural diagram of the structure obtained in step S7 of the disclosed manufacturing method according to an embodiment of the invention;
FIG. 8b is a schematic structural diagram of the structure obtained in step S7 of the second embodiment of the present invention;
FIG. 9a is a schematic structural diagram of the structure obtained in step S8 of the preparation method disclosed in the third embodiment of the present invention;
fig. 9b is a schematic structural diagram of the structure obtained in step S8 in the preparation method disclosed in the fourth embodiment of the present invention.
In the figure, 10, a silicon substrate; 11. a back cavity; 20. porous silicon; 30. a first insulating layer; 40. a resistor strip; 41. n-type doped polysilicon resistor strips; 42. p-type doped polysilicon resistor strips; 50. a second insulating layer; 51. a contact hole; 60. a metal layer; 70. a high temperature resistant coating; 80. a silicon-rich silicon nitride mask layer.
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 high-temperature heat flow sensor supported by porous silicon thermal insulation, which comprises:
a silicon substrate 10;
a first insulating layer 30 covering the upper surfaces of the silicon substrate 10 and the porous silicon 20;
the resistor strip 40 is positioned on the first insulating layer 30 and is partially positioned above the porous silicon 20;
a second insulating layer 50 at least covering the upper surface and the side surface of the resistor strip 40, and partially etching to form a contact hole 51 with the resistor strip 40;
a metal layer 60 on the second insulating layer 50 and partially above the porous silicon 20, wherein part of the metal layer 60 is connected to the resistive bar 40 through the contact hole 51 to form a thermocouple/thermopile;
and a refractory coating 70 covering the second insulating layer 50 and the metal layer 60 and partially etched to expose a portion of the metal layer 60.
As an alternative of the invention, the back cavity 11 is opened on the lower surface of the silicon substrate of the high-temperature heat flow sensor supported by the porous silicon in a heat insulation way, and the back cavity 11 is stopped at the lower surface of the porous silicon 20.
Specifically, in the first and second embodiments of the present invention, as shown in fig. 8a and 8b, the porous silicon adiabatic-supported high-temperature heat flow sensor does not include the back cavity 11. In the third and fourth embodiments of the present invention, as shown in fig. 9a and 9b, the porous silicon adiabatic-supported high-temperature heat flow sensor includes a back cavity 11.
In the embodiment of the present invention, the silicon substrate 10 is a P-type doped monocrystalline silicon wafer with a doping concentration of 7 × 1018cm-3(ii) a The porous silicon 20 has a porosity of about 60% and a thickness of about 50 μm.
The material of the first insulating layer 30 is silicon oxide and silicon nitride.
The resistive track 40 is used to form a thermocouple/thermopile, which is made of N-type doped polysilicon and/or P-type doped polysilicon.
In the first and third embodiments of the present invention, as shown in fig. 8a and 9a, the resistor strip 40 includes an N-type doped polysilicon resistor strip 41 and a P-type doped polysilicon resistor strip 42, the N-type doped polysilicon resistor strip 41 and the P-type doped polysilicon resistor strip 42 are used as two thermoelectric materials, and are alternately connected by a metal layer 60 to form a thermocouple/thermopile, the number of pairs of thermocouples is one, and the number of pairs of thermopiles is at least two. At this time, the metal layer 60 serves only as a lead and an electrode, i.e., the N-type doped polysilicon resistor bar 41 and the P-type doped polysilicon resistor bar 42 constitute a thermocouple/thermopile.
In the second and fourth embodiments of the present invention, as shown in fig. 8b and 9b, the resistor strip 40 is an N-type doped polysilicon resistor strip 41 or a P-type doped polysilicon resistor strip 42, the N-type doped polysilicon resistor strip 41 or the P-type doped polysilicon resistor strip 42 and the metal layer 60 are alternately connected to form a thermocouple/thermopile, the number of pairs of thermocouples is one, and the number of pairs of thermopiles is at least two. At this time, a portion of the metal layer 60 serves as another thermoelectric material of the thermocouple/thermopile, i.e., the resistive strip 40 and a portion of the metal layer 60 constitute the thermocouple/thermopile.
In an embodiment of the present invention, the material of the metal layer 60 is a combination of chromium and gold.
It should be noted that the ends of the resistive strips 40 and the metal layer 60 above the porous silicon 20 form the hot end of the thermocouple/thermopile, and the ends of the resistive strips 40 and the metal layer 60 above the silicon substrate form the cold end of the thermocouple/thermopile.
In the embodiment of the present invention, the material of the second insulating layer 50 is silicon nitride.
The contact holes 51 are used for providing a connection path between the metal layer 60 and the resistor strip 40, and have a shape including, but not limited to, one of a circle, a polygon, and a cross pattern; in the embodiment of the present invention, the contact hole 51 has a rectangular shape.
In the third and fourth embodiments of the present invention, the cross-sectional shape of the back cavity 11 is rectangular.
The working principle of the high-temperature heat flow sensor with the porous silicon heat insulation support is as follows: since porous silicon has much lower thermal conductivity than bulk silicon, when high temperature heat flow is incident on the device surface, the heat flows rapidly along its radius, creating a temperature gradient between the hot and cold ends of the thermocouple/thermopile. The intensity of the incident heat flow can be directly measured by the magnitude of the output potential of the cold end and the hot end. When a back cavity exists, the heat insulation performance of the hot end is better, the potential difference output by the hot end and the cold end is more obvious, and the measurement is more accurate.
It should be noted that high-temperature heat flow generates high temperature of several hundreds or even thousands of degrees centigrade on the surface of the device to cause the silicon-based structure to be damaged, high-temperature-resistant silicon carbide is used as a coating to realize rapid heat dissipation, the temperature is reduced to the bearable range of the silicon-based structure, and then the temperature difference of a cold end and a hot end is generated through the porous silicon heat insulation structure; in addition, the silicon carbide also has good mechanical property and chemical property, and is beneficial to improving the wear resistance and corrosion resistance of the device.
The invention also provides a preparation method of the porous silicon heat insulation supported high-temperature heat flow sensor, as shown in figure 1, the preparation method comprises the following steps:
s1, providing a silicon substrate 10, forming a silicon-rich silicon nitride mask layer 80 with a window on the silicon substrate 10 by low pressure chemical vapor deposition, and forming a window by dry etching, as shown in fig. 2; the dry etching process includes, but is not limited to, plasma etching, ion beam etching, and reactive ion etching, and the reactive ion etching process is used in this embodiment.
S2, forming porous silicon 20 by electrochemical etching inward on the upper surface of the silicon substrate 10, and removing the silicon-rich silicon nitride mask layer 80 by using phosphoric acid solution, as shown in fig. 3.
S3, forming a first insulating layer 30 on the silicon substrate 10 and the porous silicon 20 by low pressure chemical vapor deposition, as shown in fig. 4.
S4, depositing polysilicon on the first insulating layer 30 by using low-pressure chemical vapor deposition, doping the polysilicon by using an ion implantation process, and forming the resistor strip 40 partially located above the porous silicon 20 by using an inductively coupled plasma etching process, where, as shown in the first embodiment shown in fig. 5a, two resistor strips 40 are included, and both of the two resistor strips are partially located above the porous silicon 20; in the second embodiment shown in fig. 5b, the resistor strip 40 includes one resistor partially located above the porous silicon 20.
S5, forming a second insulating layer 50 on the first insulating layer 30 and the resistor strip 40 by using plasma enhanced chemical vapor deposition, and etching the second insulating layer 50 by using a dry etching process to form a contact hole 51, as shown in fig. 6a and 6 b; the dry etching process includes, but is not limited to, plasma etching, ion beam etching, and reactive ion etching, and the reactive ion etching process is used in this embodiment.
S6, forming a metal layer 60 on the surface of the first insulating layer 30 and/or the second insulating layer 50 by a metal stripping process, and connecting a portion of the metal layer 60 with the resistor strip 40 through the contact hole 51, as shown in fig. 7a and 7 b.
S7, forming the refractory coating 70 on the surfaces of the second insulating layer 50 and the metal layer 60 by using a plasma enhanced chemical vapor deposition method, and etching the refractory coating 70 by using a dry etching process to expose a portion of the metal layer 60, i.e., the electrode, as shown in fig. 8a and 8 b. The dry etching process includes, but is not limited to, inductively coupled plasma etching and magnetic neutral loop discharge plasma etching, and in this embodiment, the inductively coupled plasma etching process is used.
As an alternative of the invention, the preparation method of the porous silicon heat insulation supported high-temperature heat flow sensor further comprises the following steps:
s8, forming a back cavity 11 inward on the lower surface of the silicon substrate 10 by using a dry etching process, wherein the back cavity 11 stops at the lower surface of the porous silicon 20, as shown in the third embodiment shown in fig. 9a and the fourth embodiment shown in fig. 9 b.
In addition, in the preparation methods of the third embodiment and the fourth embodiment of the present invention, step S8 needs to be executed; in the preparation methods of the first and second embodiments of the present invention, the step S8 is not required to be executed.
The heat flow sensor manufactured based on the MEMS technology has the advantages of small volume, high sensitivity, high response speed, simple preparation process and strong controllability, and is compatible with the existing mature microelectronic process. Compared with a suspended membrane, the porous silicon support structure has high mechanical stability and is not easy to deform or even crack, and meanwhile, the porous silicon has thermal conductivity far lower than that of bulk silicon (when the porosity of the porous silicon is more than 30%, the thermal conductivity of the porous silicon is reduced by nearly 3 orders of magnitude compared with that of the bulk silicon). Therefore, the invention uses thicker porous silicon to form a heat insulation support structure, and can remarkably improve the mechanical stability of the device while ensuring the heat insulation performance of the hot end of the thermocouple/thermopile. Meanwhile, the silicon carbide is adopted as the high-temperature-resistant coating, so that the invention has the following advantages: the silicon carbide has high melting point and good heat resistance, and can keep stable chemical properties at ultrahigh temperature; the silicon carbide has high thermal conductivity, and can quickly dissipate a large amount of heat caused by ultrahigh temperature and large heat flow, thereby protecting a silicon-based structure and improving the survival capability and mechanical stability of devices; the silicon carbide also has good mechanical property and chemical property, and is beneficial to improving the wear resistance and corrosion resistance of the device.
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 (10)
1. A porous silicon adiabatically supported high temperature heat flow sensor, comprising:
a silicon substrate;
porous silicon formed inward from a top local area of the silicon substrate;
a first insulating layer covering the silicon substrate and the upper surface of the porous silicon;
the resistor strip is positioned on the first insulating layer and is locally positioned above the porous silicon;
the second insulating layer at least covers the upper surface and the side faces of the resistor strip and is locally etched to form a contact hole with the resistor strip;
the metal layer is positioned on the second insulating layer and is partially positioned above the porous silicon, and part of the metal layer is connected with the resistance strip through the contact hole so as to form a thermocouple/thermopile;
and the high-temperature resistant coating covers the second insulating layer and the metal layer and is partially etched to expose part of the metal layer.
2. The porous silicon adiabatic support high temperature heat flow sensor of claim 1, wherein the lower surface of the silicon substrate is provided with a back cavity, and the back cavity is stopped at the lower surface of the porous silicon.
3. The porous silicon adiabatic support high temperature heat flow sensor of claim 1 or 2, wherein the resistive tracks comprise N-type doped polysilicon resistive tracks and P-type doped polysilicon resistive tracks, the N-type doped polysilicon resistive tracks and the P-type doped polysilicon resistive tracks are alternately connected through the metal layer to form thermocouples/thermopiles, the number of pairs of the thermocouples is one, and the number of pairs of the thermopiles is at least two.
4. The porous silicon adiabatic support high temperature heat flow sensor of claim 1 or 2, wherein the resistive tracks are N-doped polysilicon resistive tracks or P-doped polysilicon resistive tracks, the N-doped polysilicon resistive tracks or the P-doped polysilicon resistive tracks are alternately connected with the metal layer to form thermocouples/thermopiles, the number of pairs of the thermocouples is one, and the number of pairs of the thermopiles is at least two.
5. The porous silicon adiabatic support high temperature heat flow sensor of claim 1, wherein the silicon substrate is a P-type doped monocrystalline silicon wafer, and the doping concentration is not less than 7 x 1016cm-3(ii) a The porosity of the porous silicon is not less than 30%, and the thickness of the porous silicon is 10-80 mu m; the first insulating layer and the second insulating layer are made of silicon oxide and/or silicon nitride, the metal layer is made of one or a combination of titanium, tungsten, chromium, platinum, aluminum and gold, and the high-temperature-resistant coating is made of silicon carbide; the shape of the contact hole is circular, polygonal or cross-shaped; the cross section of the back cavity is rectangular or trapezoidal.
6. A preparation method of a porous silicon heat insulation support high-temperature heat flow sensor is characterized by comprising the following steps:
1) providing a silicon substrate, and forming a silicon-rich silicon nitride mask layer with a window on the upper surface of the silicon substrate;
2) forming porous silicon inwards at a window on the upper surface of the silicon substrate, and then removing the silicon-rich silicon nitride mask layer;
3) forming a first insulating layer on the silicon substrate and the upper surface of the porous silicon;
4) depositing polycrystalline silicon on the first insulating layer, and doping and etching the polycrystalline silicon to form a resistor strip which is locally positioned above the porous silicon;
5) forming a second insulating layer on the first insulating layer and the resistor strip, and etching the second insulating layer to form a contact hole communicated with the resistor strip;
6) forming a metal layer on the surface of the second insulating layer, wherein part of the metal layer is connected with the resistor strip through the contact hole;
7) and forming a high-temperature-resistant coating on the surfaces of the second insulating layer and the metal layer, and etching the high-temperature-resistant coating to expose part of the metal layer, namely the electrode.
7. The method for preparing a porous silicon adiabatic support high temperature heat flow sensor according to claim 6, further comprising the following steps: and forming a back cavity inwards on the lower surface of the silicon substrate, wherein the back cavity is stopped at the lower surface of the porous silicon.
8. The method for preparing the porous silicon heat-insulating supported high-temperature heat flow sensor according to claim 6, wherein in the step 1), the silicon-rich silicon nitride mask layer is formed by low-pressure chemical vapor deposition or plasma enhanced chemical vapor deposition, and the window is formed by a dry etching process; in the step 2), the porous silicon is formed by adopting an electrochemical corrosion method, and the silicon-rich silicon nitride mask layer is removed by adopting a phosphoric acid solution.
9. The method for preparing a porous silicon heat insulation supporting high-temperature heat flow sensor according to claim 6, wherein in the step 3) and the step 5), the first insulating layer and the second insulating layer are formed by low-pressure chemical vapor deposition and/or plasma enhanced chemical vapor deposition, the first insulating layer and the second insulating layer are made of silicon oxide and/or silicon nitride, and contact holes are formed by a dry etching process.
10. The method for preparing the porous silicon heat insulation supporting high-temperature heat flow sensor according to claim 7, wherein in the step 4), the polycrystalline silicon is formed by low-pressure chemical vapor deposition, the polycrystalline silicon is doped by an ion implantation process, and the resistor strips are formed by an inductively coupled plasma etching process; in the step 6), a metal stripping process is adopted to form the metal layer, or a method of firstly sputtering metal or evaporating metal and then etching is adopted to form the metal layer; in the step 7), one of a chemical vapor deposition method, a magnetron sputtering method and a molecular beam epitaxy method is adopted to form the high-temperature-resistant coating, and a dry etching process is adopted to etch the high-temperature-resistant coating; and forming the back cavity by adopting one of anisotropic wet etching, isotropic wet etching or dry etching.
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