A metal embedded micro-nano film thermal flow sensor

Abstract

The present invention relates to a metal embedded micro-nano film heat flow sensor, belonging to the field of sensor technology. The sensor comprises a protective layer I, a protective layer II, a conductive seed layer I, a conductive seed layer II, an adhesive layer I, an adhesive layer II, an insulating layer I, an insulating layer II, a sensing layer and an epoxy resin. The manufacturing method is: a bonding layer, an insulating layer, a sensing layer, a barrier layer, a seed layer and a protective layer are deposited layer by layer by electroplating, spin coating, photolithography, magnetron sputtering, electron beam evaporation, low pressure chemical vapor deposition, plasma enhanced chemical vapor deposition and other process steps. The present invention can effectively ensure the use effect of the sensor in a harsh industrial environment, and help to greatly improve its service life.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors and relates to a metal embedded micro-nano film heat flow sensor. Background Art

[0002] Thermal field detection is a task that is often carried out in the process of modern industrial production and scientific research. It mainly involves two physical quantities: temperature and heat flow. A full understanding of the dynamic characteristics of thermal field distribution and heat transfer process and the correct analysis of the factors affecting related production processes and product quality control, the latter of which often better reflects the close correlation in physical mechanisms, is particularly important. For the detection of heat flow, traditional thermopiles are often difficult to use in some scenarios with strict restrictions on installation space size and more drastic instantaneous dynamic changes due to their shortcomings such as large size and slow response. Even if they can be used, their performance will be greatly reduced in terms of accuracy, reliability, timeliness and durability. Summary of the invention

[0003] In view of this, an object of the present invention is to provide a metal embedded micro-nano film thermal flow sensor.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A metal embedded micro-nano film heat flow sensor mainly comprises a protective layer I, a protective layer II, a conductive seed layer I, a conductive seed layer II, an adhesive layer I, an adhesive layer II, an insulating layer I, an insulating layer II, a sensing layer and epoxy resin.

[0006] A conductive seed layer I is sputtered on the surface of the protective layer I.

[0007] The protective layer I and the protective layer II are electroplated nickel protective layers.

[0008] The bonding layer I is sputtered on the surface of the conductive seed layer I.

[0009] The insulating layer I is deposited on the surface of the bonding layer I.

[0010] The insulating layer I includes an aluminum oxide insulating layer I, a silicon nitride insulating layer I and an aluminum oxide insulating layer II which are deposited in sequence.

[0011] A sensing layer is sputtered on the surface of the insulating layer I.

[0012] The sensing layer is composed of at least two thermocouple loops connected in series; each thermocouple loop includes a first sensing loop and a second sensing loop sputtered on the surface of the insulating layer I.

[0013] A plurality of thermopile loops are deposited between the aluminum oxide insulating layer I and the aluminum oxide insulating layer III to achieve multi-point detection in a local area.

[0014] The first sensing circuit includes a bonding layer III, a metal sensing layer I and a bonding layer IV which are sputtered in sequence.

[0015] The second sensing circuit includes an adhesive layer V, a metal sensing layer II and an adhesive layer VI which are sputtered in sequence.

[0016] The insulating layer II is deposited on the surfaces of the bonding layer III, the bonding layer V and the aluminum oxide insulating layer II.

[0017] The insulating layer II includes an aluminum oxide insulating layer III, a silicon nitride insulating layer II and an aluminum oxide insulating layer IV which are deposited in sequence.

[0018] The bonding layer II is sputtered on the surface of the aluminum oxide insulating layer IV.

[0019] The conductive seed layer II is sputtered on the surface of the bonding layer II.

[0020] The protection layer II is electroplated on the conductive seed layer II to protect the metal embedded micro-nano film thermal flow sensor.

[0021] The materials of the bonding layer I, bonding layer II, bonding layer III, bonding layer IV, bonding layer V and bonding layer VI are titanium. The materials of the conductive seed layer I and conductive seed layer II are nickel.

[0022] Epoxy resin is coated on the outer surface of the metal embedded micro-nano thin film heat flow sensor.

[0023] The thickness of the bonding layer I, bonding layer II, bonding layer III, bonding layer IV, bonding layer V, and bonding layer VI ranges from 5nm to 50nm. The thickness of the aluminum oxide insulating layer I, aluminum oxide insulating layer II, aluminum oxide insulating layer III, and aluminum oxide insulating layer IV ranges from 500nm to 1000nm; the thickness of the silicon nitride insulating layer I and silicon nitride insulating layer II ranges from 750nm to 1500nm; the thickness of the metal sensing layer I and the metal sensing layer II ranges from 100nm to 900nm. The thickness of the conductive seed layer I and the conductive seed layer II ranges from 50nm to 300nm.

[0024] The metal embedded micro-nano film heat flow sensor detects heat flow by collecting the temperature difference potential signal between two points in the heat transfer direction. The temperature difference potential signal between two points in the heat transfer direction is amplified by the thermopile circuit, and the amplification factor depends on the number of series thermocouple circuit groups.

[0025] A method for manufacturing the metal embedded micro-nano film thermal flow sensor mainly comprises the following steps:

[0026] Step 1: Select a silicon substrate, and clean and smooth the silicon substrate. The main steps are:

[0027] Step 1.1: Clean the silicon substrate with acetone / deionized water.

[0028] Step 1.2: Clean the silicon substrate by using persulfuric acid.

[0029] Step 1.3: wet-etch the silicon substrate using BOE.

[0030] Step 2: Using low pressure chemical vapor deposition process, silicon nitride layer I and silicon nitride layer II are deposited on the upper top surface and lower bottom surface of the silicon substrate substrate, respectively. Silicon nitride layer I is used as an etching barrier layer when wet etching the silicon substrate substrate. The thickness of silicon nitride layer I ranges from 0.1 μm to 5 μm.

[0031] Step 3: Remove the silicon nitride layer II using RIE reactive ion etching process.

[0032] Step 4: Coat the surface of silicon nitride layer I with photoresist by spin coating process, pre-bake on a hot plate, expose with a mask on a photolithography machine, place on a hot plate for post-bake, place in a developer for development, and form a sensor plate after cleaning and drying.

[0033] Step 5: depositing a first sensing circuit on the surface of the photoresist by a magnetron sputtering process, placing the first sensing circuit in acetone for immersion to remove the photoresist, and finally drying. The first sensing circuit includes a bonding layer III, a metal sensing layer I, and a bonding layer IV sputtered in sequence.

[0034] Step 6: Coat the surface of silicon nitride layer I with photoresist by a uniform coating spin coating process, perform pre-baking on a hot plate, then use a mask plate on a photolithography machine for exposure, place it on a hot plate for post-baking, place it in a developer for development, and form a sensor plate after cleaning and drying. The photoresist thickness ranges from 1 μm to 5 μm.

[0035] Step 7: Deposit a second sensing circuit on the surface of the photoresist layer by magnetron sputtering, soak the formed second sensing circuit in acetone to strip the photoresist, and finally dry the second sensing circuit. The second sensing circuit includes a bonding layer V, a metal sensing layer II, and a bonding layer VI sputtered in sequence.

[0036] Step 8: Repeat steps 5 to 7 to deposit a sensing layer composed of a plurality of thermocouple loops connected in series on the surface of the photoresist. Each thermocouple loop includes a first sensing loop and a second sensing loop sputtered on the surface of the insulating layer I.

[0037] Step 9: Deposit an aluminum oxide insulating layer I on the sensing layer by electron beam evaporation. Deposit a silicon nitride insulating layer I on the surface of the aluminum oxide insulating layer I by plasma enhanced chemical vapor deposition. Deposit an aluminum oxide insulating layer II on the surface of the silicon nitride insulating layer I by electron beam evaporation.

[0038] Step 10: sputtering an adhesive layer II and a conductive seed layer on the surface of the aluminum oxide insulating layer II in sequence.

[0039] Step 11: Electroplating a protective layer I on the top surface of the silicon nitride layer I and the conductive seed layer I by electroplating. Using a potassium hydroxide solution wet etching process to remove the silicon substrate substrate to achieve substrate transfer. Using an RIE dry etching process to remove the silicon nitride layer I.

[0040] Step 12: After excluding the pad area through the baffle, an aluminum oxide insulating layer III is deposited on the exposed surfaces of the first sensing circuit and the second sensing circuit by an electron beam evaporation process. A silicon nitride insulating layer II is deposited on the surface of the aluminum oxide insulating layer III by a plasma enhanced chemical vapor deposition process. An aluminum oxide insulating layer IV is deposited on the surface of the silicon nitride insulating layer II by an electron beam evaporation process.

[0041] Step 13: sputter an adhesive layer II and a conductive seed layer II on the surface of the aluminum oxide insulating layer IV in sequence. Electroplating a protective layer II on the surface of the conductive seed layer II is performed by an electroplating process to achieve embedded protection of the sensor.

[0042] Step 14: Use conductive silver glue to connect compensation wires to all pads on the sensing layer, apply a layer of epoxy resin after curing on a hot plate, and then cure for t time to complete the production of the metal embedded micro-nano film heat flow sensor. The time range of t is 10 to 36 hours.

[0043] It is worth mentioning that the micro-nano thin film thermal flow sensor is made based on the MEMS micro-electromechanical processing technology in the clean room. The main process links involve lithography, magnetron sputtering, electron beam evaporation, dry etching, wet etching, low-pressure chemical vapor deposition, plasma enhanced chemical vapor deposition and other processes. It is a relatively more advanced and cutting-edge sensor technology. The thickness of its working layer is usually only a few hundred nanometers, and the protective layer is usually no more than 1mm. At the same time, the line width and node size of its working layer are in the micron level. Such small size characteristics give it technical characteristics such as convenient and flexible installation, fast dynamic response, and true and reliable detection. In addition, multiple detection points can be reasonably arranged in a small local area through line optimization design, which can significantly improve the technical limitations of traditional detection components in these aspects. In addition, the use of a metal substrate with high hardness, high melting point and good thermal conductivity as an embedded protective layer can greatly improve the thin film sensor's ability to withstand high temperature and high pressure harsh environments and its service life, providing an important hardware foundation for further optimization of heat flow detection schemes and further enrichment of detection methods in various industrial scenarios.

[0044] The present invention is based on the classic Seebeck effect and the thermopile principle of multiple groups of K-type thermocouples connected in series. In a clean room, MEMS micro-electromechanical processing processes such as uniform resin spin coating, photolithography development, magnetron sputtering, electron beam evaporation, dry etching, wet etching, low-pressure chemical vapor deposition, and plasma enhanced chemical vapor deposition are used to manufacture the core circuit of the sensing layer with traditional silicon wafers as the substrate material, and combined with electroplating and etching processes to achieve transfer to a metal substrate with relatively high melting point and hardness and good thermal and electrical conductivity, to produce a typical sandwich layered structure of a metal embedded micro-nano thin film heat flux sensor that can withstand high temperatures of 1000°C.

[0045] The technical effect of the present invention is unquestionable. The present invention is suitable for local dynamic heat flow detection in a high temperature environment of 1000°C. Compared with the traditional thermopile detection method, it has significant technical characteristics such as small size, fast response, high precision, and good protection. It is particularly suitable for detection scenarios with strict installation size restrictions and drastic changes in transient heat flow. It can be widely used in aerospace, precision machine tool processing, national defense and military industry, metallurgical manufacturing and other fields. The micro-nano film sensor provided by the present invention is small in size, fast in response, and has little disturbance to the original thermal field. It can capture the instantaneous dynamic changes of the thermal field in a timely and accurate manner. It can be flexibly and conveniently installed in a small space and closer to the test point for detection. Multiple groups of thermopile circuits can be arranged simultaneously in a detection area according to needs to realize local multi-point detection. Based on the metal embedded packaging method with relatively high melting point hardness and good corrosion resistance, the sensor has good high temperature and high pressure resistance and anti-interference performance, which can effectively ensure the use effect of the sensor in harsh industrial environments and help to greatly improve its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0047] Figure 1 Schematic diagram of the design of micro-nano thin film heat flow sensor;

[0048] Figure 2 The schematic diagram of the structure after the silicon nitride etching barrier layer is completed on the substrate;

[0049] Figure 3 Schematic diagram of the exposure and development process steps;

[0050] Figure 4 Schematic diagram of sputtering deposition of metal sensing layer;

[0051] Figure 5 This is a schematic diagram after the deposition of the bipolar sensing circuit is completed;

[0052] Figure 6 A schematic diagram of the structure after the first composite insulating layer I is deposited;

[0053] Figure 7 Schematic diagram of the structure after the sensing layer is transferred from silicon base to metal base;

[0054] Figure 8 It is a schematic diagram of the structure of an embedded package formed after electroplating a metal protective layer;

[0055] Fig. 9 Schematic diagram of the core working layer of the micro-nano thin film thermal flux sensor.

[0056] Figure numerals: 101 - protective layer I, 102 - protective layer II, 103 - silicon substrate, 201 - conductive seed layer I, 202 - conductive seed layer II, 301 - bonding layer I, 302 - bonding layer II, 401 - aluminum oxide insulating layer I, 402 - silicon nitride insulating layer I, 403 - aluminum oxide insulating layer II, 501 - bonding layer III, 502 - metal sensing layer I, 503 - bonding layer IV, 504 - bonding layer V, 505 - metal sensing layer II, 506 - bonding layer VI, 601 - aluminum oxide insulating layer III, 602 - silicon nitride insulating layer II, 603 - aluminum oxide insulating layer IV, 7 - silicon nitride layer I, 8 - photoresist, 9 - wire, 10 - pad, A - sensor anode, B - sensor cathode, T - upper temperature sensing contact, T0 - lower temperature sensing contact. DETAILED DESCRIPTION

[0057] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0058] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0059] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0060] Embodiment 1:

[0061] See also Figures 1 to 9 A metal embedded micro-nano thin film thermal flow sensor mainly comprises a protective layer I (101), a protective layer II (102), a conductive seed layer I (201), a conductive seed layer II (202), an adhesive layer I (301), an adhesive layer II (302), an insulating layer I, an insulating layer II, a sensing layer and epoxy resin.

[0062] A conductive seed layer I (201) is sputtered on the surface of the protective layer I (101).

[0063] The protective layer I (101) and the protective layer II (102) are electroplated nickel protective layers.

[0064] The bonding layer I (301) is sputtered on the surface of the conductive seed layer I (201).

[0065] The insulating layer I is deposited on the surface of the bonding layer I (301).

[0066] The insulating layer I includes an aluminum oxide insulating layer I (401), a silicon nitride insulating layer I (402) and an aluminum oxide insulating layer II (403) which are deposited in sequence.

[0067] A sensing layer is sputtered on the surface of the insulating layer I.

[0068] The sensing layer is composed of at least two thermocouple loops connected in series; each thermocouple loop includes a first sensing loop and a second sensing loop sputtered on the surface of the insulating layer I.

[0069] A plurality of thermopile loops are deposited between the aluminum oxide insulating layer I (401) and the aluminum oxide insulating layer III (601) to achieve multi-point detection in a local area.

[0070] The first sensing circuit comprises an adhesive layer III (501), a metal sensing layer I (502) and an adhesive layer IV (503) which are sputtered in sequence.

[0071] The second sensing circuit includes an adhesive layer V (504), a metal sensing layer II (505) and an adhesive layer VI (506) which are sputtered in sequence.

[0072] The insulating layer II is deposited on the surfaces of the bonding layer III (501), the bonding layer V (504) and the aluminum oxide insulating layer I (401).

[0073] The insulating layer II includes an aluminum oxide insulating layer III (601), a silicon nitride insulating layer II (602) and an aluminum oxide insulating layer IV (603) which are deposited in sequence.

[0074] The bonding layer II (302) is sputtered on the surface of the aluminum oxide insulating layer IV (603).

[0075] The conductive seed layer II (202) is sputtered on the surface of the bonding layer II (302).

[0076] The protection layer II (102) is electroplated on the conductive seed layer II (202) to protect the metal embedded micro-nano film thermal flow sensor.

[0077] The materials of the bonding layer I (301), the bonding layer II (302), the bonding layer III (501), the bonding layer IV (503), the bonding layer V (504) and the bonding layer VI (506) are titanium.

[0078] The conductive seed layer I (201) and the conductive seed layer II (202) are made of nickel.

[0079] Epoxy resin is coated on the outer surface of the metal embedded micro-nano thin film heat flow sensor.

[0080] The thickness of the adhesive layer I (301), the adhesive layer II (302), the adhesive layer III (501), the adhesive layer IV (503), the adhesive layer V (504), and the adhesive layer VI (506) ranges from 5 nm to 50 nm.

[0081] The thickness of the aluminum oxide insulating layer I (401), the aluminum oxide insulating layer II (403), the aluminum oxide insulating layer III (601), and the aluminum oxide insulating layer IV (603) ranges from 500 nm to 1000 nm;

[0082] The thickness of the silicon nitride insulating layer I (402) and the silicon nitride insulating layer II (602) ranges from 750 nm to 1500 nm.

[0083] The thickness of the metal sensing layer I (502) and the metal sensing layer II (505) ranges from 100 nm to 900 nm.

[0084] The thickness of the conductive seed layer I (201) and the conductive seed layer II (202) ranges from 50 nm to 300 nm.

[0085] The metal embedded micro-nano film heat flow sensor detects heat flow by collecting the temperature difference potential signal between two points in the heat transfer direction. The temperature difference potential signal between two points in the heat transfer direction is amplified by the thermopile circuit, and the amplification factor depends on the number of series thermocouple circuit groups.

[0086] Embodiment 2:

[0087] A metal embedded micro-nano film heat flow sensor, the main structure of which is shown in Example 1, wherein:

[0088] The thickness of the adhesive layer I (301), the adhesive layer II (302), the adhesive layer III (501), the adhesive layer IV (503), the adhesive layer V (504), and the adhesive layer VI (506) is 5 nm.

[0089] The thickness of the aluminum oxide insulating layer I (401), the aluminum oxide insulating layer II (403), the aluminum oxide insulating layer III (601), and the aluminum oxide insulating layer IV (603) is 500 nm;

[0090] The thickness of the silicon nitride insulating layer I (402) and the silicon nitride insulating layer II (602) is 750 nm;

[0091] The thickness of the metal sensing layer I (502) and the metal sensing layer II (505) is 100 nm.

[0092] The thickness of the conductive seed layer I (201) and the conductive seed layer II (202) is 50 nm.

[0093] Embodiment 3:

[0094] A metal embedded micro-nano film heat flow sensor, the main structure of which is shown in Example 1, wherein:

[0095] The thickness of the adhesive layer I (301), the adhesive layer II (302), the adhesive layer III (501), the adhesive layer IV (503), the adhesive layer V (504), and the adhesive layer VI (506) is 50 nm.

[0096] The thickness of the aluminum oxide insulating layer I (401), the aluminum oxide insulating layer II (403), the aluminum oxide insulating layer III (601), and the aluminum oxide insulating layer IV (603) is 1000 nm;

[0097] The thickness of the silicon nitride insulating layer I (402) and the silicon nitride insulating layer II (602) is 1500 nm;

[0098] The thickness of the metal sensing layer I (502) and the metal sensing layer II (505) is 900 nm.

[0099] The thickness of the conductive seed layer I (201) and the conductive seed layer II (202) is 300 nm.

[0100] Embodiment 4:

[0101] A metal embedded micro-nano film heat flow sensor, the main structure of which is shown in Example 1, wherein:

[0102] The thickness of the adhesive layer I (301), the adhesive layer II (302), the adhesive layer III (501), the adhesive layer IV (503), the adhesive layer V (504), and the adhesive layer VI (506) is 22.5 nm.

[0103] The thickness of the aluminum oxide insulating layer I (401), the aluminum oxide insulating layer II (403), the aluminum oxide insulating layer III (601), and the aluminum oxide insulating layer IV (603) is 750 nm;

[0104] The thickness of the silicon nitride insulating layer I (402) and the silicon nitride insulating layer II (602) is 1125 nm;

[0105] The thickness of the metal sensing layer I (502) and the metal sensing layer II (505) is 500 nm.

[0106] The thickness of the conductive seed layer I (201) and the conductive seed layer II (202) is 175 nm.

[0107] Embodiment 5:

[0108] A metal embedded micro-nano thin film heat flow sensor mainly includes a bonding layer, an insulating layer, a sensing layer, a barrier layer, a seed layer and a protective layer which are deposited layer by layer by using a traditional silicon wafer as a substrate through electroplating, spin coating, photolithography, magnetron sputtering, electron beam evaporation, low pressure chemical vapor deposition, plasma enhanced chemical vapor deposition and other process steps. This embodiment adopts dry etching and wet etching processes to form a typical metal embedded sandwich layered structure.

[0109] The design of the sensing layer is based on the thermopile principle, that is, multiple K-type thermocouples are connected in series, and two different nickel-based alloys are used as the two-pole materials of the thermocouple loop. The heat flow value of the detection point is obtained by reading the amplified thermoelectric electromotive force signal. Multiple sets of thermopile loops can be deposited on the sensing layer of the same substrate substrate at the same time to achieve multi-point detection in a small local area, with high spatial resolution, and even if one detection point is damaged, the remaining detection points can still work normally, and the detection redundancy is good. The sensor film thickness is only hundreds of nanometers, the line width and hot junction size are small, the mass and heat capacity are small, and the rapid response to the rapid change of the thermal field is fast. Its response time can reach microseconds, and the interference and destructiveness to the real thermal field of the detection point is small. The sensor uses a metal with good electrical and thermal conductivity, high melting point and hardness as a protective layer, and a ceramic material with high melting point, high hardness and good dielectric properties as an insulating layer, which can reliably realize heat flow detection in a 1000℃ environment. The aluminum oxide-silicon nitride-aluminum oxide composite multilayer insulation layer design can not only overcome the pinhole defects that may exist in the aluminum oxide film layer, but also minimize the thermal stress caused by the large difference in thermal expansion coefficient between the silicon nitride layer and the metal film layer. A layer of metal is sputtered on the upper and lower sides of the metal sensor as a bonding layer to enhance the bonding between the metal sensing layer and the insulation layer, prevent the occurrence of stratification, and effectively reduce the detection noise. A layer of metal is deposited on the surface of the bonding layer of the composite insulation layer on the upper part of the sensing layer as a conductive seed layer, and a layer of metal with a high melting point and high hardness is electroplated on it as an embedded protective layer.

[0110] Traditional silicon wafers are used as the substrate for sensor manufacturing, and the sensor is transferred from the silicon base to the metal base through an etching process.

[0111] The sensor is a typical sandwich layer structure, including an adhesive layer, an insulating layer, a sensing layer, a barrier layer, a seed layer and a protective layer, which are deposited layer by layer through electroplating, spin coating, photolithography, magnetron sputtering, electron beam evaporation, low-pressure chemical vapor deposition, plasma enhanced chemical vapor deposition and other processes. Among them, the thickness of the adhesive layer is 5nm to 50nm, the thickness of the insulating layer is 1μm to 5μm, the thickness of the sensing layer is 100nm to 900nm, the thickness of the barrier layer is 0.1μm to 5μm, and the thickness of the seed layer is 50nm to 300nm.

[0112] The design of the sensor is based on the thermopile principle of multiple groups of K-type thermocouples connected in series, and uses NiCr (nickel chromium) -Ni (nickel) Al (aluminum) Mn (manganese) Si (silicon), NiCr-NiAl (nickel aluminum), and NiCr-NiSi (nickel silicide) alloys as the two-pole materials constituting the thermocouple loop.

[0113] Multiple groups of thermopile loops are deposited simultaneously on the sensing layer of the same substrate to achieve multi-point detection in a small local area.

[0114] The sensor film is as thin as hundreds of nanometers, with small line width and thermal junction size, small mass and heat capacity, and can quickly reflect transient changes in the thermal field. Its response time can reach microseconds, and it has little destructive effect on the actual thermal field of the detection point.

[0115] The sensor uses oxide and nitride ceramic materials with high melting point, high hardness and good dielectric properties as the insulating layer, which can reliably realize heat flow detection in an environment of 1000℃.

[0116] The aluminum oxide-silicon nitride-aluminum oxide composite multi-layer insulation layer design can not only overcome the pinhole defects that may exist in the aluminum oxide film layer, but also minimize the thermal stress caused by the large difference in thermal expansion coefficient between the silicon nitride layer and the metal film layer.

[0117] A layer of metal titanium is sputtered on the upper and lower sides of the metal sensor as a bonding layer to enhance the bonding between the metal sensing layer and the insulating layer and effectively reduce detection noise.

[0118] A layer of metal is deposited on the surface of the bonding layer of the composite insulating layer on the upper part of the sensing layer as a conductive seed layer, and a layer of metal with a high melting point and high hardness is electroplated on the surface as an embedded protective layer.

[0119] Embodiment 6:

[0120] A method for manufacturing the metal embedded micro-nano film thermal flow sensor mainly comprises the following steps:

[0121] Step 1: Select a silicon substrate (103), and clean and smooth the silicon substrate. The main steps are:

[0122] Step 1.1: Clean the silicon substrate (103) using acetone / deionized water.

[0123] Step 1.2: Clean the silicon substrate (103) using persulfuric acid.

[0124] Step 1.3: wet-etch the silicon substrate (103) using BOE.

[0125] Step 2: using a low pressure chemical vapor deposition process to deposit a silicon nitride layer I (7) and a silicon nitride layer II on the upper top surface and the lower bottom surface of the silicon substrate substrate (103), respectively. The silicon nitride layer I (7) is used as an etching barrier layer when the silicon substrate substrate (103) is wet-etched. The thickness of the silicon nitride layer I (7) is in the range of 0.1 μm to 5 μm.

[0126] Step 3: Use RIE (reactive ion etching) to remove the silicon nitride layer II.

[0127] Step 4: Coat the surface of the silicon nitride layer I (7) with photoresist (8) by a uniform coating and spin coating process, and perform pre-baking on a hot plate. Then, use a mask plate to expose the surface on a photolithography machine, place the surface on a hot plate for post-baking, place the surface in a developer for development, and form a sensor plate after cleaning and drying.

[0128] Step 5, depositing a first sensing circuit on the surface of the photoresist by a magnetron sputtering process, placing the first sensing circuit in acetone for immersion to remove the photoresist (8), and finally drying. The first sensing circuit includes a bonding layer III (501), a metal sensing layer I (502), and a bonding layer IV (503) sputtered in sequence.

[0129] Step 6: Coat the surface of the silicon nitride layer I (7) with photoresist (8) by a uniform coating and spin coating process, and perform pre-baking on a hot plate, then use a mask plate on a photolithography machine for exposure, then place it on a hot plate for post-baking, place it in a developer for development, and form a sensor plate after cleaning and drying. The thickness of the photoresist (8) ranges from 1 μm to 5 μm.

[0130] Step 7: Deposit a second sensing circuit on the surface of the photoresist layer by magnetron sputtering, place the second sensing circuit in acetone for immersion to remove the photoresist (8), and finally dry. The second sensing circuit includes a bonding layer V (504), a metal sensing layer II (505), and a bonding layer VI (506) sputtered in sequence.

[0131] Step 8: Repeat steps 5 to 7 to deposit a sensing layer composed of a plurality of thermocouple loops connected in series on the surface of the photoresist. Each thermocouple loop includes a first sensing loop and a second sensing loop sputtered on the surface of the insulating layer I.

[0132] Step 9: Deposit an aluminum oxide insulating layer I (401) on the sensing layer by electron beam evaporation. Deposit a silicon nitride insulating layer I (402) on the surface of the aluminum oxide insulating layer I (401) by plasma enhanced chemical vapor deposition. Deposit an aluminum oxide insulating layer II (403) on the surface of the silicon nitride insulating layer I (402) by electron beam evaporation.

[0133] Step 10: sputtering an adhesive layer II and a conductive seed layer on the surface of the aluminum oxide insulating layer II (403) in sequence.

[0134] Step 11: Electroplating a protective layer I (101) on the top surface of the silicon nitride layer I (7) and the conductive seed layer I (201) by electroplating. Using a potassium hydroxide solution wet etching process to remove the silicon substrate substrate (103) to achieve substrate transfer. Using an RIE dry etching process to remove the silicon nitride layer I (7).

[0135] Step 12: After the pad area is excluded by the baffle, an aluminum oxide insulating layer III (601) is deposited on the exposed surfaces of the first sensing circuit and the second sensing circuit by electron beam evaporation. A silicon nitride insulating layer II (602) is deposited on the surface of the aluminum oxide insulating layer III (601) by plasma enhanced chemical vapor deposition. An aluminum oxide insulating layer IV (603) is deposited on the surface of the silicon nitride insulating layer II (602) by electron beam evaporation.

[0136] Step 13: sputter an adhesive layer II (302) and a conductive seed layer II (202) on the surface of the alumina insulating layer IV (603) in sequence. Electroplating a protective layer II (102) on the surface of the conductive seed layer II (202) is performed by electroplating to achieve embedded protection of the sensor.

[0137] Step 14: Use conductive silver glue to connect all pads (10) on the sensing layer to the compensation wire (9), and then apply a layer of epoxy resin after curing on a hot plate, and then cure for t time to complete the production of the metal embedded micro-nano film heat flow sensor. The time range of t is 10 to 36 hours.

[0138] Embodiment 7:

[0139] A method for manufacturing the metal embedded micro-nano film thermal flow sensor mainly comprises the following steps:

[0140] 1) According to the requirements of heat flow detection, design and manufacture the mask of micro-nano thin film heat flow sensor, including the shape, size and quantity of the sensor, see Figure 1 shown.

[0141] 2) A 4” diameter silicon wafer was used as the substrate for sensor deposition. After acetone / deionized water cleaning, persulfate cleaning for 20 min, and BOE (buffered oxide etchant, such as hydrofluoric acid + water, ammonium fluoride + water, etc.) wet etching for 5 min, the surface of the silicon wafer was thoroughly cleaned and smoothed.

[0142] 3) A thin layer of low-stress silicon nitride with a thickness of 0.1 μm to 5.0 μm is deposited on both sides of the silicon wafer by low-pressure chemical vapor deposition (LPCVD) process. Then, the silicon nitride layer on the back side of the silicon wafer is removed by RIE reactive ion etching process. The silicon nitride layer on the front side of the silicon wafer is used as an etching barrier layer for subsequent wet etching of the silicon wafer. Figure 2 shown.

[0143] 4) A layer of photoresist with a thickness of 1 μm to 5 μm is applied on the surface of the silicon nitride layer on the front side of the silicon wafer by a uniform coating spin coating process, and then pre-baked on a hot plate, and then exposed using a mask on a photolithography machine. After completion, it is placed on a hot plate for post-baking, and then placed in a developer for development. After cleaning and drying, a plate with the shape and size of the sensor is formed, as shown in FIG. Figure 3 shown.

[0144] 5) Three layers of metal are sequentially deposited on the surface of the photoresist layer by magnetron sputtering process, which are metal titanium with a thickness of 5nm to 50nm, nickel-based alloy with a thickness of 100nm to 900nm, and metal titanium with a thickness of 5nm to 50nm. Then, the metal is placed in acetone for immersion and stripping, and after cleaning and drying, the first pole sensing circuit is formed. Figure 4 shown.

[0145] 6) Repeat the above two process steps, apply a new layer of photoresist with a thickness of 1μm to 5μm, and after exposure and development, deposit metal titanium, another nickel-based alloy, and metal titanium in turn, and then place it in acetone for immersion and stripping, and after cleaning and drying, form the second-pole sensing circuit. Figure 5 shown.

[0146] Next, an aluminum oxide-silicon nitride-aluminum oxide composite insulating layer is deposited on the sensing layer. First, a 500nm-1000nm thick aluminum oxide layer is deposited by electron beam evaporation (EB), and then a 750nm-1500nm thick silicon nitride layer is deposited by plasma enhanced chemical vapor deposition (PECVD). Then, a 500nm-1000nm thick aluminum oxide layer is deposited by electron beam evaporation. Next, a 5nm-50nm thick titanium layer is sputtered on the composite insulating layer as a bonding layer and a 50nm-300nm thick nickel layer is sputtered as an electroplating seed layer. Figure 6 shown.

[0147] 7) A metal nickel layer with a thickness of 100 μm to 200 μm is formed on the front side of the silicon wafer by electroplating, and then the silicon wafer is removed by a potassium hydroxide solution wet etching process to achieve the transfer of the sensor with the silicon nitride layer from the silicon wafer to the nickel substrate, and then the silicon nitride layer is removed by a RIE dry etching process. Figure 7 shown.

[0148] 8) On the exposed sensing layer, an aluminum oxide-silicon nitride-aluminum oxide composite insulating layer is deposited again using the same process as step (7), and the pad area is excluded from the deposition step by a baffle, and then a layer of 5nm-50nm thick titanium as a bonding layer and a layer of 50nm-300nm thick nickel as an electroplating seed layer are sputtered again on the composite insulating layer, and finally a metal nickel layer with a thickness of 30μm-100μm is formed on the seed layer by an electroplating process to achieve embedded protection of the sensor, see Figure 8 shown.

[0149] 9) Use conductive silver glue to connect all pads on the sensing layer to compensation wires, and then apply a layer of epoxy resin after curing on a hot plate. After aging curing for 10 to 36 hours, the entire sensor is completed. It detects heat flow by collecting potential signals. The sensing layer is its core working layer. Fig. 9 shown.

[0150] Embodiment 8:

[0151] A method for manufacturing the metal embedded micro-nano film thermal flow sensor mainly comprises the following steps:

[0152] 1) First, according to the requirements of heat flow detection, a micro-nano thin film heat flow sensor is designed, such as Figure 1As shown, the shape, size and number of sensors are included. The design of the sensor is based on the Seebeck effect thermoelectric principle and the thermopile principle of multiple groups of K-type thermocouples in series, that is, two different conductors are used as anodes and cathodes respectively, and their two ends are tightly connected to each other to form a closed loop. When the temperatures of the two junctions are not equal (T>T0), an electromotive force will be generated in the loop, thereby forming a thermal current. If multiple groups of thermocouples with the same physical properties are connected in series to form a thermopile, the temperature difference potential between the two points in the heat transfer direction will be amplified, and the amplification factor depends on the number of series groups. A key indicator of the thermopile is sensitivity, that is, the thermoelectric potential output under unit heat flow, and its value depends on the thermal conductivity of the substrate material, the number of series thermocouple groups, and the distance between the upper and lower temperature sensing junctions, and meets the requirement that a good design must ensure sufficient sensitivity. The sensor uses a thermopile composed of multiple groups of K-type thermocouples in series, and uses a K-type thermocouple alloy as the sensing layer. Multiple groups of sensors are arranged on the substrate as required, and each group of sensors can be arranged with multiple pairs of thermocouple thermopile loops. The loop routing design should be as symmetrical and beautiful as possible and easy to cut and process. At the same time, the success rate of sensor production should also be taken into account when considering the plane size of the sensor, that is, the line width of a single electrode and the distance between each pair of electrodes should not be too small. In addition, in order to reduce the difficulty of lead connection and ensure insulation between each pair of pads, the side length of a single square pad and the distance between each pair of pads should not be too small.

[0153] 2) A 4” diameter silicon wafer was used as the substrate for sensor deposition. It was first cleaned with acetone / deionized water to remove grease, then cleaned with persulfuric acid (mixed with hot sulfuric acid and hydrogen peroxide) for 20 minutes to remove organic pollutants, and then wet-etched with BOE (buffered oxide etchant mixed with 49% hydrofluoric acid and water in a ratio of 6:1) for 5 minutes to obtain a smooth surface, thus achieving thorough cleaning and flattening of the silicon wafer surface.

[0154] 3) A low-stress silicon nitride layer with a thickness of 0.1 μm to 5.0 μm is deposited on both sides of the silicon wafer by low-pressure chemical vapor deposition (LPCVD) process, and then the silicon nitride layer on the back side of the silicon wafer is removed by RIE reactive ion etching process. The silicon nitride layer on the front side of the silicon wafer is used as an etching barrier layer for subsequent wet etching of the silicon wafer. Figure 2 As shown. The specific chemical vapor deposition process parameters are: SiCl2H2 flow rate 100sccm~200sccm, NH3 flow rate 10sccm~40sccm, working pressure 200mTorr~400mTorr, working temperature 700℃~100℃. The specific RIE etching process parameters are: CF4 flow rate 30sccm~90sccm, O2 flow rate 1sccm~10sccm, working pressure 40mTorr~100mTorr, power 70W~150W.

[0155] 4) In order to produce the designed sensor plate to carry out the next step of sputtering deposition of the metal sensing layer, it is necessary to apply a layer of photoresist with a thickness of 1μm to 5μm on the surface of the silicon nitride layer on the front side of the silicon wafer through a uniform coating spin coating process. Then, pre-bake on a hot plate to remove the solvent in the photoresist and enhance adhesion. Next, place the pre-baked substrate on a photolithography machine for exposure. After the exposure is completed, place the substrate on a hot plate for post-bake to stimulate the acid produced by the PAG photosensitive acid generator of the chemically enhanced photoresist to react with the protective group on the photoresist and remove the group so that it can be dissolved in the developer, while reducing the standing wave effect. Subsequently, the post-baked substrate is placed in a developer for development. After the development is completed, it is washed with deionized water and blown dry with nitrogen to finally form a plate of the shape and size of the sensor, such as Figure 3 shown.

[0156] 5) In order to enhance the bonding between the silicon nitride layer and the subsequent metal sensing layer, it is first necessary to deposit a layer of metal titanium with a thickness of 5nm to 50nm as a bonding layer on the silicon nitride layer through a magnetron sputtering process. Sputtering is the use of plasma with a kinetic energy of more than tens of electron volts to bombard the surface of the solid target material. The atoms near the surface obtain part of the energy carried by the incident particles. When it is sufficient to overcome the binding energy, these atoms will break away from the solid and enter the vacuum chamber, and then deposit on the substrate. The specific sputtering process parameters are: sputtering power 500W~1000W, working pressure 1mTorr~5mTorr, Ar flow rate 10sccm~30sccm, sputtering rate 10nm / min~20nm / min, sputtering time 2min~6min. Of course, the parameters may be adjusted for different equipment platforms. Then, a layer of nickel-based alloy with a thickness of 100nm to 900nm is deposited through the magnetron sputtering process. The specific sputtering process parameters are: sputtering power 200W to 600W, working pressure 1mTorr to 5mTorr, Ar flow 10sccm to 30sccm, sputtering rate 10nm / min to 20nm / min, sputtering time 30min to 80min. Similarly, the parameters may be adjusted for different equipment platforms. Then, a layer of 5nm to 50nm thick titanium is sputtered according to the same process as before. After the deposition is completed, the substrate is taken out and placed in acetone for an immersion stripping process to remove the remaining photoresist on the substrate. It is then cleaned with deionized water and blown dry with nitrogen to complete the deposition of the first-pole sensing circuit on the substrate. Figure 4 Shown

[0157] 6) Repeat the above two process steps. First apply a layer of photoresist with a thickness of 1μm to 5μm. Then sputter deposit a layer of metal titanium with a thickness of 5nm to 50nm. Then sputter deposit a layer of another nickel-based alloy with a thickness of 100nm to 900nm. The specific sputtering process parameters are: sputtering power 200W to 600W, working pressure 1mTorr to 5mTorr, Ar flow 10sccm to 30sccm, sputtering rate 10nm / min to 20nm / min, sputtering time 30min to 80min. The parameters may be adjusted for different equipment platforms. Then sputter deposit a layer of metal titanium with a thickness of 5nm to 50nm. After the deposition is completed, it is soaked, peeled, cleaned and dried to complete the deposition of the second-pole sensing circuit on the substrate, such as Figure 5 As shown. So far, the core sensing layer has been completed.

[0158] 7) Next, it is necessary to make the first aluminum oxide-silicon nitride-aluminum oxide composite insulating layer above the sensing layer. First, an electron beam evaporation process is used to deposit a 500nm-1000nm thick aluminum oxide layer. The so-called electron beam evaporation is a physical vapor deposition method, that is, using the coordination of the electromagnetic field to accurately achieve the use of high-energy electrons to bombard the target material, so that it melts and deposits on the substrate object. The specific evaporation process parameters are: working pressure (2-6) × 10-5 Torr, substrate temperature 100℃-300℃, oxygen replenishment. To ensure that the insulating layer is uniform and dense, a plasma enhanced chemical vapor deposition process is then used to deposit a 750nm-1500nm thick silicon nitride layer. The specific chemical deposition process parameters are: SiH4 flow rate 100sccm-200sccm, NH3 flow rate 80sccm-120sccm, N2O flow rate 800sccm-1200sccm, working pressure 600mTorr-1000mTorr. Then, a 500nm to 1000nm thick aluminum oxide layer is deposited by electron beam evaporation. Next, a 5nm to 50nm thick titanium layer is sputtered on the composite insulating layer as a bonding layer and a 50nm to 300nm thick nickel layer is sputtered as an electroplating seed layer. The resistance between the upper and lower titanium layers of the composite insulating layer finally formed should be ensured to reach the megohm level, such as Figure 6 shown.

[0159] 8) In order to realize the transfer of the sensor from the silicon wafer substrate to the metal substrate, firstly, a metal nickel layer with a thickness of 100μm to 200μm is formed on the electroplating seed layer on the front side of the silicon wafer through an electroplating process. The specific electroplating process parameters are: Watt plating solution plus brightener, electroplating time 20min to 40min, plating solution temperature 35℃ to 50℃, plating solution pH value 3 to 5, and current 3 to 6A. Then, a 30% potassium hydroxide solution is used to remove the entire silicon wafer substrate through a wet etching process at 70℃ to 85℃ for 5 hours to 8 hours. At this time, the sensor with the silicon nitride layer is transferred from the silicon wafer substrate to the nickel substrate. Next, the silicon nitride layer is removed by a RIE reactive ion dry etching process to expose the sensing layer, such as Figure 7 shown.

[0160] 9) On the exposed sensing layer, a second aluminum oxide-silicon nitride-aluminum oxide composite insulating layer is deposited again using the same process as step (7), and the pad area is excluded in the deposition step by a baffle specially designed for the sensing layer pattern, and then a layer of 5nm-50nm thick titanium as a bonding layer and a layer of 50nm-300nm thick nickel as a conductive seed layer are sputtered again on the composite insulating layer, and finally a metal nickel layer with a thickness of 30μm-100μm is formed on the seed layer by an electroplating process to achieve sandwich layer structure embedded protection of the sensor, see Figure 8 shown.

[0161] 10) The last step is to cure the lead wires, that is, to connect all the pads on the sensing layer with the compensation wires using conductive silver glue, and then apply a layer of epoxy resin after curing on a hot plate. After aging curing for 10 to 36 hours, the entire sensor is completed. It detects heat flow by collecting potential signals, and the sensing layer is its core working layer. Fig. 9 shown.

[0162] The metal embedded micro-nano film heat flux sensor proposed in the present invention has a small size, fast response, and little interference to the original thermal field. It can capture the instantaneous dynamic changes of the thermal field in a timely and accurate manner, can be flexibly and conveniently installed in a small space and closer to the test point for detection, and can arrange multiple groups of thermopile circuits in a detection area at the same time according to needs to achieve local multi-point detection. Based on the sandwich layered embedded structure of the metal nickel substrate with relatively high melting point hardness and good corrosion resistance, the sensor has good high temperature and high pressure resistance, anti-interference and corrosion resistance, can effectively avoid wear and erosion, can effectively ensure the use of thin film sensors in harsh industrial environments, and help to greatly improve its durability and service life. The present invention can significantly improve the technical limitations and disadvantages of traditional heat flow detection components in terms of spatial size, dynamic response, and packaging protection, and provides an important hardware foundation and technical means for the optimization and innovation of traditional heat flow detection methods. It is worthy of promotion and application in various heat flow detection fields.

[0163] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A metal embedded micro-nano film thermal flow sensor, characterized in that: The sensor comprises a protective layer I (101), a protective layer II (102), a conductive seed layer I (201), a conductive seed layer II (202), an adhesive layer I (301), an adhesive layer II (302), an insulating layer I, an insulating layer II and a sensing layer; A conductive seed layer I (201) is sputtered on the surface of the protective layer I (101); The bonding layer I (301) is sputtered on the surface of the conductive seed layer I (201); The insulating layer I is deposited on the surface of the bonding layer I (301); The insulating layer I comprises an aluminum oxide insulating layer I (401), a silicon nitride insulating layer I (402) and an aluminum oxide insulating layer II (403) which are deposited in sequence; A sensing layer is sputtered on the surface of the insulating layer I; the sensing layer is at least two thermocouple loops connected in series to form a thermopile; each thermocouple loop includes a first sensing loop and a second sensing loop sputtered on the surface of the insulating layer I; The first sensing circuit comprises a bonding layer III (501), a metal sensing layer I (502) and a bonding layer IV (503) which are sputtered in sequence; The second sensing circuit comprises a bonding layer V (504), a metal sensing layer II (505) and a bonding layer VI (506) which are sputtered in sequence; The insulating layer II is deposited on the surfaces of the bonding layer III (501), the bonding layer V (504) and the aluminum oxide insulating layer I (401); The insulating layer II comprises an aluminum oxide insulating layer III (601), a silicon nitride insulating layer II (602) and an aluminum oxide insulating layer IV (603) which are deposited in sequence; The bonding layer II (302) is sputtered on the surface of the aluminum oxide insulating layer IV (603); The conductive seed layer II (202) is sputtered on the surface of the bonding layer II (302); The protective layer II (102) is electroplated on the conductive seed layer II (202) to protect the metal embedded micro-nano thin film thermal flow sensor; A plurality of thermopile loops are deposited between the aluminum oxide insulating layer I (401) and the aluminum oxide insulating layer III (601) to achieve multi-point detection in a local area.

2. The metal embedded micro-nano thin film thermal flow sensor according to claim 1, characterized in that: The protective layer I (101) and the protective layer II (102) are electroplated nickel protective layers; The bonding layer I (301), the bonding layer II (302), the bonding layer III (501), the bonding layer IV (503), the bonding layer V (504), and the bonding layer VI (506) are made of titanium; The material of the conductive seed layer I (201) and the conductive seed layer II (202) is nickel.

3. The metal embedded micro-nano thin film thermal flow sensor according to claim 1, characterized in that: The thickness of the adhesive layer I (301), the adhesive layer II (302), the adhesive layer III (501), the adhesive layer IV (503), the adhesive layer V (504), and the adhesive layer VI (506) ranges from 5 nm to 50 nm; The thickness of the aluminum oxide insulating layer I (401), the aluminum oxide insulating layer II (403), the aluminum oxide insulating layer III (601), and the aluminum oxide insulating layer IV (603) ranges from 500 nm to 1000 nm; The thickness of the silicon nitride insulating layer I (402) and the silicon nitride insulating layer II (602) ranges from 750 nm to 1500 nm; The thickness of the metal sensing layer I (502) and the metal sensing layer II (505) ranges from 100 nm to 900 nm; The thickness of the conductive seed layer I (201) and the conductive seed layer II (202) ranges from 50 nm to 300 nm.

4. The metal embedded micro-nano thin film thermal flow sensor according to claim 1, characterized in that: The outer surface of the sensor is coated with epoxy resin.

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