Novel thermopile type MEMS flow sensor easy to package and preparation method thereof

Abstract

The invention discloses a novel thermopile type MEMS flow sensor easy to package and a preparation method thereof. The sensor comprises a heating resistor, an environment temperature measurement resistor, a first temperature measurement thermopile, a second temperature measurement thermopile, a silicon dioxide layer, a mixed substrate, a conductive through hole, a silicon supporting layer and a back cavity. Wherein the heating resistor is distributed in the middle of the sensor, and four groups of temperature measuring thermopiles are symmetrically distributed on two sides of the heating resistor. Through the back cavity and the silicon oxide heat insulation area, heat transfer through the substrate is effectively reduced, the measuring range and the sensitivity of the sensor are improved by optimizing the arrangement mode of the thermopiles, and the packaging difficulty of the device is reduced by arranging the back conductive through hole structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of flow sensor preparation, and in particular relates to a novel thermopile MEMS flow sensor which is easy to package and a preparation method thereof. Background Art

[0002] Accurate flow measurement can provide important information for many fields such as industrial production, scientific research, and medical health. There are many types of flow sensors commonly used at present, among which the thermal temperature difference flow sensor based on MEMS technology is widely used due to its simple structure, small size, high accuracy, fast response, low power consumption and many other advantages.

[0003] MEMS thermal flow sensors based on the thermal temperature difference principle can be classified according to different control modes. Common control modes include: constant voltage mode, constant current mode, constant power mode, constant temperature difference mode and temperature balance mode. Among them, the constant temperature difference mode is the most commonly used. This mode controls the chip temperature through a feedback loop to be a constant temperature difference higher than the ambient temperature, effectively suppressing the influence of the ambient temperature on the sensor measurement results. However, the disadvantage of this mode is that it requires an external ambient temperature sensor, which increases the complexity of the system.

[0004] Factors that affect the measurement accuracy of thermal flow sensors include heating elements, temperature measuring elements and thermal insulation treatment. Among them, heating elements and temperature measuring elements can affect the response speed and range of the sensor, and good thermal insulation treatment can improve the sensitivity of the sensor. Usually, in order to improve the thermal insulation effect and reduce heat dissipation, MEMS thermal flow sensor chips are usually set as suspended structures, such as suspended membranes, suspended bridges, etc. However, due to its structural characteristics, the suspended structure is prone to uneven stress distribution, resulting in reduced device stability. At the same time, during the device packaging process, the pins led out from the front of the chip will affect the flow rate measurement of the fluid, resulting in measurement errors and reducing the measurement accuracy of the chip. Summary of the invention

[0005] The purpose of the present invention is to provide a novel thermopile MEMS flow sensor that is easy to package and a preparation method thereof. The back cavity and the substrate insulation area are used to effectively reduce the transmission of heat through the substrate and improve the performance of the sensor. The heating resistor and the temperature measuring thermopile are generated on a mixed substrate with a certain strength, thereby improving the working stability of the device. By optimizing the arrangement of the thermopiles, the number of thermopiles under the same effective area is increased, thereby improving the range and sensitivity of the sensor. At the same time, there are back conductive through holes in the thermopile flow sensor, which avoids the influence of the front leads on the sensor accuracy and reduces the packaging difficulty, so as to solve the technical problems mentioned in the background technology.

[0006] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0007] A novel thermopile MEMS flow sensor that is easy to package, comprising:

[0008] A hybrid substrate, a first temperature measuring thermopile, a second temperature measuring thermopile, a silicon support layer, a silicon dioxide layer, a heating resistor, an environmental temperature measuring resistor, a conductive through hole, a back cavity and a first surface of the silicon support layer.

[0009] The silicon dioxide layer is located on the first surface of the silicon supporting layer.

[0010] The hybrid substrate consists of the polysilicon substrate and the silicon oxide thermal isolation region; the polysilicon substrate is located on the silicon dioxide layer and is divided into several parts by the silicon oxide thermal isolation region; the silicon oxide thermal isolation region is symmetrically distributed on both sides of the center line of the flow sensor.

[0011] The heating resistor is located on the hybrid substrate and distributed at the center line of the flow sensor. A first insulating layer and a first through hole for leading out the heating resistor and a lead wire for connecting the heating resistor are provided above the heating resistor.

[0012] The environmental temperature measuring resistor is arranged on the hybrid substrate and distributed outside the flow sensor, and has the first insulating layer and the fifth through hole for leading out the environmental temperature measuring resistor, and the environmental temperature measuring resistor lead wire for connecting the environmental temperature measuring resistor and the conductive through hole;

[0013] The first temperature measuring thermopile is formed on the surface of the hybrid substrate, and the first temperature measuring thermopile has two symmetrically distributed on both sides of the heating resistor, including a first temperature measuring thermopile first temperature sensing material layer and a second temperature measuring thermopile second temperature sensing material layer, a first insulating layer and a second through hole are provided between the first temperature measuring thermopile first temperature sensing material layer and the second temperature measuring thermopile second temperature sensing material layer, and a second insulating layer is provided on the second temperature measuring thermopile second temperature sensing material layer; the second temperature measuring thermopile is formed on the surface of the hybrid substrate, and the second temperature measuring thermopile has two symmetrically distributed on both sides of the heating resistor, including a first temperature measuring thermopile first temperature sensing material layer and a second temperature measuring thermopile second temperature sensing material layer; a first insulating layer and a third through hole are provided between the first temperature measuring thermopile first temperature sensing material layer and the second temperature measuring thermopile second temperature sensing material layer, and a second insulating layer is provided on the second temperature measuring thermopile second temperature sensing material layer;

[0014] The conductive through hole penetrates the hybrid substrate, the silicon oxide layer and the silicon support layer, and the conductive through hole is formed by connecting the metal conductive through hole, the conductive silicon column and the bonding block in sequence from top to bottom.

[0015] Furthermore, the silicon dioxide layer is a dense thin film, and the generation method is one of LPCVD, plasma enhanced chemical vapor deposition or thermal oxidation; the polycrystalline silicon substrate in the hybrid substrate is obtained by epitaxial growth; the silicon oxide thermal isolation area is formed by filling the polycrystalline silicon groove array formed by etching with a thermal oxidation method.

[0016] Furthermore, the hot junctions of the first temperature measuring thermopile and the second temperature measuring thermopile are respectively arranged along different parallel lines parallel to the outside of the heating resistor, and the distance between the hot junction of the first temperature measuring thermopile and the heating resistor is closer than the distance between the second temperature measuring thermopile and the heating resistor; the cold junctions of the first temperature measuring thermopile and the second temperature measuring thermopile are respectively arranged along the same parallel line parallel to the outside of the heating resistor and its extension line.

[0017] Furthermore, the distribution trend of the first temperature measuring thermopile relative to the center line of the flow sensor is in the shape of an "eight", the thermocouples close to the heating resistor end are concentrated in a central area and arranged in parallel, and the thermocouples far from the heating resistor end are evenly distributed in two edge areas; the central area refers to an area that is closer to the central vertical line of the heating resistor along the direction perpendicular to the arrangement of the temperature measuring thermopile, and the edge area refers to an area that is farther away from the heating resistor along the central vertical line of the temperature measuring thermopile in the direction perpendicular to the arrangement of the temperature measuring thermopile; the shape arrangement of the thermocouples of the first temperature measuring thermopile in the area near the heating resistor end and in the middle area near the heating resistor end is one of a curved line, a straight line or a broken line.

[0018] Furthermore, the heating resistor and the environmental temperature measuring resistor are made of the same material, which is one of metal, N-type polycrystalline silicon or P-type polycrystalline silicon; the first temperature-sensitive material layer and the second temperature-sensitive material layer of the first temperature-measuring thermopile are made of a combination of two of metal, N-type polycrystalline silicon or P-type polycrystalline silicon; the first temperature-sensitive material layer and the second temperature-sensitive material layer of the second temperature-measuring thermopile are made of a combination of two of metal, N-type polycrystalline silicon or P-type polycrystalline silicon; the first insulating layer is made of one of silicon oxide and silicon nitride, and is formed by one of PECVD or LPCVD techniques; the second insulating layer is made of one of silicon oxide and silicon nitride, and is formed by one of PECVD or LPCVD techniques.

[0019] Furthermore, the first through hole, the second through hole, the third through hole, the fourth through hole and the fifth through hole are all formed by dry etching processes such as RIE and IBE; the fourth through hole is filled by one of metal sputtering, metal evaporation or electroplating; the material of the metal conductive through hole is one of copper, gold, titanium, chromium, aluminum, platinum or tungsten; the material of the heating resistor lead, the environmental temperature measuring resistor lead, the front lead of the thermopile through hole and the back welding block is one of titanium, tungsten, chromium, platinum, aluminum or gold; the conductive silicon column is an independent silicon column generated by deep silicon etching.

[0020] Furthermore, the fourth through hole is filled by metal sputtering, metal evaporation or electroplating; and the material of the metal conductive through hole is copper, gold, titanium, chromium, aluminum, platinum or tungsten.

[0021] Furthermore, the conductive silicon pillar is an independent silicon pillar generated by deep silicon etching; and the back cavity is formed by deep silicon etching.

[0022] Furthermore, the number of the conductive through holes is 12, which are respectively used for connecting the heating resistor, the environmental temperature measuring resistor, two pairs of first temperature measuring thermopiles, and two pairs of second temperature measuring thermopiles.

[0023] The method for preparing the novel thermopile MEMS flow sensor that is easy to package of the present invention comprises the following steps:

[0024] S1. providing a low-resistance silicon wafer as a silicon support layer, and generating silicon dioxide on a first surface of the silicon support layer to form the silicon dioxide layer;

[0025] S2, epitaxially growing polysilicon on the silicon dioxide layer to form the polysilicon substrate;

[0026] S3, etching the groove array on the polysilicon substrate;

[0027] S4, oxidizing and filling the groove array by thermal oxidation to form the silicon oxide thermal isolation region;

[0028] S5, generating the heating resistor, the environmental temperature measuring resistor, the first thermopile first temperature-sensitive material layer and the second thermopile first temperature-sensitive material layer on the surface of the hybrid substrate;

[0029] S6, forming a first insulating layer on the heating resistor, the environmental temperature measuring resistor, the first temperature-sensitive material layer of the first thermopile, the first temperature-sensitive material layer of the second thermopile and the surface of the mixed substrate, and etching a first through hole, a second through hole, a third through hole, a fourth through hole and a fifth through hole;

[0030] S7, filling the fourth through hole to generate the metal conductive through hole;

[0031] S8, forming the first thermopile second temperature-sensitive material layer, the second thermopile second temperature-sensitive material layer, the heating resistor lead, the environment temperature measuring resistor lead and the thermopile lead on the first insulating layer;

[0032] S9, forming the second insulating layer on the first thermopile second temperature-sensitive material layer, the second thermopile second temperature-sensitive material layer, the heating resistor lead, the environmental temperature measuring resistor lead and the thermopile lead;

[0033] S10, forming a back side welding block on the second surface of the silicon support layer, and performing deep silicon etching to generate a thermal isolation cavity and a conductive silicon column.

[0034] A novel thermopile MEMS flow sensor that is easy to package and a preparation method thereof of the present invention have the following advantages: the present invention effectively reduces the transfer of heat through the substrate by generating a back cavity and a silicon oxide thermal insulation area formed by a thermal oxidation method, thereby improving the heat utilization rate and the performance of the sensor; the working stability of the device is improved by generating a heating resistor and a temperature measuring thermopile on a polycrystalline silicon / silicon oxide mixed substrate with a certain strength; by optimizing the arrangement of the thermopile, four groups of temperature measuring thermopiles are set, the number of temperature measuring thermocouples under the same effective area is increased, and different thermopiles have different distances from the heating resistor, thereby improving the range and sensitivity of the sensor; the present invention generates a back conductive through hole in the thermopile flow sensor, thereby avoiding the influence of the front lead on the sensor accuracy and effectively reducing the difficulty of device packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic cross-sectional view of a novel thermopile MEMS flow sensor that is easy to package disclosed in an embodiment of the present invention;

[0036] Figure 2 This is an enlarged view of the side structure of the heating resistor;

[0037] Figure 3 This is an enlarged view of the side structure of the environmental temperature measuring resistor;

[0038] Figure 4 A schematic diagram of the arrangement structure of the heating resistor, the ambient temperature measuring resistor, the temperature measuring thermopile and the front electrode pins of a novel thermopile MEMS flow sensor that is easy to package disclosed in an embodiment of the present invention;

[0039] Figure 5 A flow chart of a method for manufacturing a novel thermopile MEMS flow sensor that is easy to package disclosed in an embodiment of the present invention;

[0040] Figure 6It is a schematic cross-sectional structure diagram of the structure obtained in step S1 of the manufacturing method disclosed in the embodiment of the present invention;

[0041] Figure 7 It is a schematic cross-sectional structure diagram of the structure obtained in step S2 of the manufacturing method disclosed in the embodiment of the present invention;

[0042] Figure 8 It is a schematic cross-sectional structure diagram of the structure obtained in step S3 of the manufacturing method disclosed in the embodiment of the present invention;

[0043] Fig. 9 It is a schematic cross-sectional structure diagram of the structure obtained in step S4 of the manufacturing method disclosed in the embodiment of the present invention;

[0044] Fig.10 It is a schematic cross-sectional structure diagram of the structure obtained in step S5 of the manufacturing method disclosed in the embodiment of the present invention;

[0045] Fig.11 It is a schematic cross-sectional structure diagram of the structure obtained in step S6 of the manufacturing method disclosed in the embodiment of the present invention;

[0046] Fig.12 It is a schematic cross-sectional structure diagram of the structure obtained in step S7 of the manufacturing method disclosed in the embodiment of the present invention;

[0047] Fig.13 It is a schematic cross-sectional structure diagram of the structure obtained in step S8 of the manufacturing method disclosed in the embodiment of the present invention;

[0048] Fig.14 It is a schematic cross-sectional structure diagram of the structure obtained in step S9 of the manufacturing method disclosed in the embodiment of the present invention;

[0049] Fig.15 It is a schematic cross-sectional structural diagram of the structure obtained in step S10 of the manufacturing method disclosed in the embodiment of the present invention;

[0050] Fig.16 It is an enlarged view of the side structure of the through hole on the environmental temperature measuring resistor of the present invention;

[0051] Explanation of the marks in the figure: 12, hybrid substrate; 21, first temperature measuring thermopile combination; 22, second temperature measuring thermopile combination; 100, silicon support layer; 101, first surface of silicon support layer; 102, second surface of silicon support layer; 110, silicon dioxide layer; 120, polycrystalline silicon substrate; 130, etching groove array; 140, silicon oxide filling area; 201, heating resistor; 202, environmental temperature measuring resistor; 210, first temperature measuring thermopile first temperature sensing material layer; 212, first temperature measuring thermopile second temperature sensing material layer; 220, second The first temperature-sensing material layer of the temperature-measuring thermopile; 222, the second temperature-sensing material layer of the second temperature-measuring thermopile; 230, the first insulating layer; 232, the second insulating layer; 240, the first through hole; 242, the second through hole; 244, the third through hole; 246, the fourth through hole; 247, the fifth through hole; 248, the heating resistor lead; 250, the ambient temperature measuring resistor lead; 300, the conductive through hole; 301, the metal conductive through hole; 302, the thermopile lead; 310, the conductive silicon column; 320, the back-side pressure welding block; 340, the back-side cavity 340. DETAILED DESCRIPTION

[0052] In order to better understand the purpose, structure and function of the present invention, a novel thermopile MEMS flow sensor that is easy to package and a preparation method thereof are further described in detail below in conjunction with the accompanying drawings.

[0053] The following describes the embodiments of the present invention through 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. For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional view showing the device structure will not be partially enlarged according to the general proportion, and the schematic diagram is only an example, which should not limit the scope of protection of the present invention. In addition, in actual preparation, the three-dimensional dimensions of length, width and depth should be included.

[0054] For ease of description, spatial relational terms such as "under", "below", "below", "below", "on", "upper", etc. may be used herein to describe the relationship between one element or feature shown in the drawings and other elements or features. It will be understood that these spatial relational terms are intended to include other directions of the device in use or operation in addition to the directions depicted in the drawings. In addition, when a layer is referred to as being "between" two layers, it may be the only layer between the two layers, or there may be one or more intervening layers. It should be noted that in order to make the illustrations as concise as possible, not all structures are labeled one by one in the drawings.

[0055] In the context of the present application, a structure in which a first feature is described as being "above" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0056] It should be noted that the diagrams provided in this embodiment are only schematic illustrations of the basic concept of the present invention, and the diagrams only show the components related to the present invention rather than the number, shape and size of the components in actual implementation. The type, quantity and proportion of each component in actual implementation may be changed at will, and the layout of the components may also be more complicated. In order to make the diagrams as concise as possible, not all structures are marked in the drawings.

[0057] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0058] To achieve the above-mentioned objectives, the present invention provides a novel thermopile MEMS flow sensor that is easy to package, comprising: a hybrid substrate 12; two first temperature measuring thermopiles 21, symmetrically distributed on both sides of a heating resistor; two second temperature measuring thermopiles 22, symmetrically distributed on both sides of a heating resistor; a silicon support layer 100; a silicon dioxide layer 110; one heating resistor 201, distributed on the center line of the flow sensor; one environmental temperature measuring resistor 202, distributed at the edge of the flow sensor; 12 conductive through holes 300, distributed on the hybrid substrate 12; a back cavity 340; and a first surface 101 of the silicon support layer.

[0059] The silicon dioxide layer 110 is formed on the first surface 101 of the silicon support layer. The silicon dioxide layer 110 is a dense thin film, and is generated by one of LPCVD, PECVD or thermal oxidation. In an embodiment of the present invention, the silicon dioxide layer 110 is generated by LPCVD.

[0060] The hybrid substrate 12 is located on the silicon dioxide layer 110, and is composed of a polycrystalline silicon substrate 120 and a silicon oxide thermal isolation region 140; wherein the polycrystalline silicon substrate 120 is formed on the silicon dioxide layer 110 and is obtained by epitaxial growth; the silicon oxide thermal isolation region 140 is formed by filling the polycrystalline silicon groove array 130 formed by etching through a thermal oxidation method, and is symmetrically distributed on both sides of the center line of the flow sensor, embedded in the polycrystalline silicon substrate, and is used to block the lateral transfer of heat in the substrate; in an embodiment of the present invention, there are four groups of silicon oxide thermal isolation regions 140, which are distributed between the first temperature measuring thermopile 21 and the heating resistor 201 and on the inner side of the hot end of the second temperature measuring thermopile 22, such as Figure 4 shown.

[0061] The heating resistor 201 is formed on the hybrid substrate 12 and distributed at the center line of the flow sensor. The heating resistor 201 has a first insulating layer 230 and a first through hole 240 for leading out the heating resistor, and a heating resistor lead 248 for connecting the heating resistor 201 and the conductive through hole 300. The material of the heating resistor 201 is one of P-type polysilicon, N-type polysilicon, and metal; the cross-section of the connection structure of the heating resistor 201, the first insulating layer 230, the second insulating layer 232, and the heating resistor lead 248 is as shown in FIG. Figure 2 As shown; in an embodiment of the present invention, the heating resistor 201 is made of metal nickel.

[0062] The environmental temperature measuring resistor 202 is formed on the hybrid substrate 12 and distributed at the edge of the flow sensor. The environmental temperature measuring resistor 202 has a first insulating layer 230 and a fifth through hole 247 for leading out the environmental temperature measuring resistor, and an environmental temperature measuring resistor lead 250 for connecting the environmental temperature measuring resistor 202 and the conductive through hole 300. The material of the environmental temperature measuring resistor 202 is one of P-type polysilicon, N-type polysilicon, and metal; the cross-section of the connection structure of the environmental temperature measuring resistor 202, the first insulating layer 230, the second insulating layer 232, and the environmental temperature measuring resistor lead 250 is as shown in FIG. Figure 3 As shown; the cross-section of the connection structure of the ambient temperature measuring resistor 202, the first insulating layer 230 and the fifth through hole 247 is as shown Fig.16 As shown; in an embodiment of the present invention, the environmental temperature measuring resistor 202 is made of metal nickel.

[0063] The first temperature measuring thermopile 21 is formed on the surface of the hybrid substrate 12. The first temperature measuring thermopile 21 has two symmetrically distributed on both sides of the heating resistor 201, including the first temperature measuring thermopile first temperature sensing material layer 210 and the first temperature measuring thermopile second temperature sensing material layer 212, with a first insulating layer 230 and a second through hole 242 in between, and a second insulating layer 232 thereon. The second temperature measuring thermopile 22 is formed on the surface of the hybrid substrate 12. The second temperature measuring thermopile 22 has two symmetrically distributed on both sides of the center line of the heating resistor 201, including the second temperature measuring thermopile first temperature sensing material layer 220 and the second temperature measuring thermopile second temperature sensing material layer 222; with a first insulating layer 230 and a third through hole 244 in between, and a second insulating layer 232 thereon.

[0064] The materials of the first temperature-sensing material layer 210 and the second temperature-sensing material layer 212 of the first temperature-measuring thermopile 21 are a combination of two of metal, N-type polysilicon or P-type polysilicon; the materials of the first temperature-sensing material layer 220 and the second temperature-sensing material layer 222 of the second temperature-measuring thermopile 22 are a combination of two of metal, N-type polysilicon or P-type polysilicon; in an embodiment of the present invention, the materials of the first temperature-sensing material layer 210 and the second temperature-sensing material layer 212 of the first temperature-measuring thermopile 21 are nickel and aluminum, respectively; the materials of the first temperature-sensing material layer 220 and the second temperature-sensing material layer 222 of the second temperature-measuring thermopile 22 are nickel and aluminum, respectively.

[0065] The hot junctions of the first temperature measuring thermopile 21 and the second temperature measuring thermopile 22 are arranged along different parallel lines parallel to the outside of the heating resistor 201, and the distance between the hot junction of the first temperature measuring thermopile 21 and the heating resistor 201 is closer than the distance between the second temperature measuring thermopile 22 and the heating resistor 201; the cold junctions of the first temperature measuring thermopile 21 and the second temperature measuring thermopile 22 are arranged along the same parallel lines parallel to the outside of the heating resistor 201 and its extension line; the distribution trend of the first temperature measuring thermopile 21 relative to the center line of the flow sensor is in the shape of an "eight", the thermocouples close to the heating resistor end are concentrated in a central area and arranged in parallel, and the thermocouples far from the heating resistor end are evenly distributed in two edge areas; the central area described refers to the vertical The edge area described refers to the area perpendicular to the arrangement direction of the temperature measuring thermopile, which is closer to the heating resistor 201 along the central vertical line perpendicular to the arrangement direction of the temperature measuring thermopile. The edge area described refers to the area perpendicular to the arrangement direction of the temperature measuring thermopile, which is away from the heating resistor 201 along the central vertical line perpendicular to the arrangement direction of the temperature measuring thermopile; the shape arrangement mode of the thermocouple of the first temperature measuring thermopile 21 in the middle area close to the heating resistor end and away from the heating resistor end is one of a curved line type, a straight line type, or a broken line type; in an embodiment of the present invention, the shape arrangement mode of the thermocouple of the first temperature measuring thermopile 21 in the middle area close to the heating resistor end and away from the heating resistor end is a broken line type, and an arrangement mode of the first temperature measuring thermopile 21 and the second temperature measuring thermopile 22 is as follows Figure 4 shown.

[0066] The first insulating layer 230 is generated on the surface of the heating resistor 201, the environmental temperature measuring resistor 202, the first temperature measuring thermopile first temperature sensing material layer 210, the second temperature measuring thermopile first temperature sensing material layer 220 and the mixed substrate 12; the second insulating layer 232 is generated on the heating resistor lead 248, the environmental temperature measuring resistor lead 250, the thermopile lead 302, the first temperature measuring thermopile second temperature sensing material layer 212, the second temperature measuring thermopile second temperature sensing material layer 222 and the first insulating layer 230; the material of the first insulating layer 230 is one of silicon oxide and silicon nitride; the material of the second insulating layer 232 is one of silicon oxide and silicon nitride; in an embodiment of the present invention, the material of the first insulating layer 230 is silicon oxide, and the material of the second insulating layer 230 is silicon nitride.

[0067] The first through hole 240 is used to lead out the heating resistor 201, the second through hole 242 is used to connect the first temperature measuring thermopile first temperature sensing material layer 210 and the first temperature measuring thermopile second temperature sensing material layer 212, the third through hole 244 is used to connect the second temperature measuring thermopile first temperature sensing material layer 220 and the second temperature measuring thermopile second temperature sensing material layer 222, the fourth through hole 246 is used to connect the conductive silicon column 310 and the front lead, and the fifth through hole 247 is used to lead out the environmental temperature measuring resistor 202. The first through hole 240, the second through hole 242, the third through hole 244, the fourth through hole 246 and the fifth through hole 247 are all formed by dry etching processes such as RIE and IBE; in the embodiment of the present invention, the first through hole 240, the second through hole 242, the third through hole 244, the fourth through hole 246 and the fifth through hole 247 are all formed by RIE dry etching process.

[0068] The conductive through hole 300 passes through the hybrid substrate 12, the silicon dioxide layer 110 and the silicon support layer 100, and includes a metal conductive through hole 301, a conductive silicon column 310 and a backside bonding block 320. The number of the conductive through holes 300 is 12, which are respectively used for the electrical connection of the heating resistor 201, the environmental temperature measuring resistor 202, the two pairs of the first temperature measuring thermopiles 21, and the two pairs of the second temperature measuring thermopiles 22; in the embodiment of the present invention, the arrangement of the conductive through holes 300 is as follows: Figure 4 shown.

[0069] The fourth through hole 246 is filled by metal sputtering, metal evaporation or electroplating, and the material of the metal conductive through hole 301 is copper, gold, titanium, chromium, aluminum, platinum or tungsten; in an embodiment of the present invention, the fourth through hole 246 is filled by electroplating, and the material of the metal conductive through hole 301 is copper.

[0070] The conductive silicon pillar 310 is an independent silicon pillar generated by deep silicon etching; the back cavity 340 is obtained by deep silicon etching of a semiconductor high thermal conductivity silicon support layer 100 compatible with CMOS process, and is used to form back thermal isolation.

[0071] The material of the heating resistor lead 248, the ambient temperature measuring resistor lead 250, the thermopile through-hole lead 302 and the back-side welding block 320 is one of titanium, tungsten, chromium, platinum, aluminum or gold; in an embodiment of the present invention, the heating resistor lead 248 is made of metal aluminum, the ambient temperature measuring resistor lead 250 is made of metal aluminum, the thermopile through-hole lead 302 is made of metal aluminum, and the back-side welding block 320 is made of metal copper.

[0072] The cross-sectional structure diagram of a novel thermopile MEMS flow sensor that is easy to package provided by the present invention is as follows: Figure 1 shown.

[0073] It should be noted that, compared with the design without setting the silicon oxide thermal isolation region, the design of introducing the silicon oxide thermal isolation region can provide good thermal isolation between the heating resistor 201 and the temperature measuring thermopiles 21 and 22, reduce heat conduction loss, and effectively reduce the power consumption of the device; the suspended thick film structure composed of the hybrid substrate 12 composed of the polysilicon substrate 120 and the silicon oxide thermal isolation region 140 and the silicon dioxide layer 110 has higher stability than the suspended thin film structure composed of silicon dioxide and silicon nitride; the optimized arrangement of the temperature measuring thermopiles improves the range and sensitivity of the flow sensor by setting two groups of temperature measuring thermopiles at different distances from the heating resistor 201: the first temperature measuring thermopiles 21 and the second temperature measuring thermopiles 22; the setting of the conductive through-holes not only avoids the influence of the front leads on the sensor, but also reduces the difficulty of packaging.

[0074] The present invention also provides a method for preparing a novel thermopile MEMS flow sensor that is easy to package, such as Figure 5 As shown, the method comprises the following steps:

[0075] S1, providing a low-resistance silicon wafer as a silicon support layer 100, generating silicon dioxide on the first surface 101 of the silicon support layer to form the silicon dioxide layer 110, such as Figure 6 shown.

[0076] Specifically, the preparation method of the silicon dioxide layer is one of LPCVD, PECVD or thermal oxidation; in the present invention, the LPCVD method is used to generate a dense silicon dioxide layer on the surface of the silicon wafer.

[0077] S2, epitaxially growing polysilicon on the silicon dioxide layer 110 to form the polysilicon substrate 120, such as Figure 7 shown.

[0078] S3, etching the groove array 130 on the polysilicon substrate 120, such as Figure 8 shown.

[0079] Specifically, RIE technology is used to etch the surface of the polysilicon substrate to form a groove array.

[0080] S4, oxidizing and filling the groove array 130 by thermal oxidation to form the silicon oxide thermal isolation region 140, and thinning and polishing the polysilicon substrate and the silicon oxide thermal isolation region, such as Fig. 9 shown.

[0081] Specifically, the surface of the hybrid substrate is processed by mechanical thinning and chemical mechanical polishing processes to make the surface smooth and flat.

[0082] S5, generating the heating resistor 201, the environmental temperature measuring resistor 202, the first temperature measuring thermopile first temperature sensing material layer 210 and the second temperature measuring thermopile first temperature sensing material layer 220 on the surface of the hybrid substrate 12, such as Fig.10 shown.

[0083] Specifically, the material of the heating resistor 201 is one of P-type polysilicon, N-type polysilicon, and metal. In an embodiment of the present invention, the heating resistor 201 is made of metal nickel and is formed by electron beam evaporation combined with a metal stripping process; the material of the environmental temperature measuring resistor 202 is one of P-type polysilicon, N-type polysilicon, and metal. In an embodiment of the present invention, the environmental temperature measuring resistor 202 is made of metal nickel and is formed by electron beam evaporation combined with a metal stripping process; the material of the first temperature sensing material layer 210 of the first temperature measuring thermopile is one of metal, N-type polysilicon or P-type polysilicon. In an embodiment of the present invention, the first temperature sensing material layer 210 of the first temperature measuring thermopile is made of metal nickel and is formed by electron beam evaporation combined with a metal stripping process; the material of the first temperature sensing material layer 220 of the second temperature measuring thermopile is one of metal, N-type polysilicon or P-type polysilicon. In an embodiment of the present invention, the first temperature sensing material layer 220 of the second temperature measuring thermopile is made of metal nickel and is formed by electron beam evaporation combined with a metal stripping process.

[0084] S6, forming a first insulating layer 230 on the surfaces of the heating resistor 201, the environmental temperature measuring resistor 202, the first thermopile first temperature sensing material layer 210, the second thermopile first temperature sensing material layer 220 and the hybrid substrate 12, and etching a first through hole 240, a second through hole 242, a third through hole 244, a fourth through hole 246 and a fifth through hole 247, as shown in FIG. Fig.11 shown.

[0085] Specifically, the material of the first insulating layer 230 is one of silicon oxide and silicon nitride, and is formed by one of PECVD or LPCVD techniques. In an embodiment of the present invention, the material of the first insulating layer 230 is silicon oxide, and is formed by LPCVD; the first through hole 240 is used to lead out the heating resistor 201, the second through hole 242 is used to connect the first temperature sensing material layer 210 of the first temperature measuring thermopile and the second temperature sensing material layer 212 of the first temperature measuring thermopile, and the third through hole 244 is used to connect the first temperature sensing material layer 220 of the second temperature measuring thermopile and The second temperature measuring thermopile has a second temperature sensing material layer 222, the fourth through hole 246 is used to connect the conductive silicon column 310 and the front lead, the fifth through hole 247 is used to lead out the ambient temperature measuring resistor 202, the first through hole 240, the second through hole 242, the third through hole 244, the fourth through hole 246 and the fifth through hole 247 are all formed by dry etching processes such as RIE and IBE. In an embodiment of the present invention, the first through hole 240, the second through hole 242, the third through hole 244, the fourth through hole 246 and the fifth through hole 247 are all formed by RIE process.

[0086] S7, filling the fourth through hole 246 to form the metal conductive through hole 301, such as Fig.12 shown.

[0087] Specifically, the method of filling the fourth through hole 246 is one of metal evaporation, metal sputtering or electroplating. In an embodiment of the present invention, the method of filling the fourth through hole 246 is electroplating; the material of the metal conductive through hole 301 is one of copper, gold, titanium, chromium, aluminum, platinum or tungsten. In an embodiment of the present invention, the material of the metal conductive through hole 301 is metal copper.

[0088] S8, forming the first thermopile second temperature-sensitive material layer 212, the second thermopile second temperature-sensitive material layer 222, the heating resistor lead 248, the environment temperature measuring resistor lead 250 and the thermopile lead 302 on the first insulating layer 230, as shown in FIG. Fig.13 shown.

[0089] Specifically, the material of the second temperature-sensing material layer 212 of the first temperature-measuring thermopile is one of metal, N-type polysilicon or P-type polysilicon. In an embodiment of the present invention, the second temperature-sensing material layer 212 of the first temperature-measuring thermopile is made of metal aluminum, which is formed by electron beam evaporation combined with a metal stripping process; the material of the second temperature-sensing material layer 222 of the second temperature-measuring thermopile is one of metal, N-type polysilicon or P-type polysilicon. In an embodiment of the present invention, the second temperature-sensing material layer 222 of the second temperature-measuring thermopile is made of metal aluminum, which is formed by electron beam evaporation combined with a metal stripping process. The material of the heating resistor lead 248 is one of titanium, tungsten, chromium, platinum, aluminum or gold. In the embodiment of the present invention, the material of the heating resistor lead 248 is metal aluminum. The material of the ambient temperature measuring resistor lead 250 is one of titanium, tungsten, chromium, platinum, aluminum or gold. In the embodiment of the present invention, the material of the ambient temperature measuring resistor lead 250 is metal aluminum. The material of the thermopile lead 302 is one of titanium, tungsten, chromium, platinum, aluminum or gold. In the embodiment of the present invention, the material of the thermopile through-hole lead 302 is metal aluminum.

[0090] S9, forming the second insulating layer 232 on the first thermopile second temperature-sensitive material layer 212, the second thermopile second temperature-sensitive material layer 222, the heating resistor lead 248, the environment temperature-measuring resistor lead 250 and the thermopile lead 302, such as Fig.14 shown.

[0091] Specifically, the material of the second insulating layer 232 is one of silicon oxide and silicon nitride, and is formed by one of PECVD and LPCVD techniques. In an embodiment of the present invention, the material of the second insulating layer 232 is silicon nitride, and is formed by LPCVD deposition.

[0092] S10, forming a pressure welding block 320 on the second surface 102 of the silicon support layer, and performing deep silicon etching to generate a thermal isolation cavity 340 and a conductive silicon column 310, such as Fig.15 shown.

[0093] Specifically, DRIE technology is used to etch the second surface 102 of the silicon support layer to obtain an isolation cavity 340, forming 12 independent conductive silicon pillars 310; the material of the welding block 320 is one of titanium, tungsten, chromium, platinum, aluminum or gold. In an embodiment of the present invention, the material of the welding block 320 is metal copper.

[0094] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A novel thermopile MEMS flow sensor that is easy to package, characterized in that: include: A hybrid substrate (12), a first temperature measuring thermopile (21), a second temperature measuring thermopile (22), a silicon support layer (100), a silicon dioxide layer (110), a heating resistor (201), an environmental temperature measuring resistor (202), a conductive through hole (300), a back cavity (340), and a first surface (101) of the silicon support layer; The silicon dioxide layer (110) is located on the first surface (101) of the silicon support layer; The hybrid substrate (12) is composed of a polycrystalline silicon substrate (120) and a silicon oxide thermal isolation region (140); the polycrystalline silicon substrate (120) is located on the silicon dioxide layer (110) and is divided into a plurality of parts by the silicon oxide thermal isolation region (140); the silicon oxide thermal isolation region (140) is symmetrically distributed on both sides of the center line of the flow sensor; The heating resistor (201) is located on the hybrid substrate (12) and distributed at the center line of the flow sensor, and the heating resistor (201) has a first insulating layer (230) and a first through hole (240) for leading out the heating resistor (201), and a heating resistor lead (248) for connecting the heating resistor (201) and the conductive through hole (300); The environmental temperature measuring resistor (202) is arranged on the hybrid substrate (12) and distributed outside the flow sensor, and the environmental temperature measuring resistor (202) has the first insulating layer (230) and a fifth through hole (247) for leading out the environmental temperature measuring resistor (202), and an environmental temperature measuring resistor lead (250) for connecting the environmental temperature measuring resistor (202) and the conductive through hole (300); The first temperature measuring thermopile (21) is formed on the surface of the hybrid substrate (12); the first temperature measuring thermopile (21) has two symmetrically distributed on both sides of the heating resistor (201); the first temperature measuring thermopile (21) comprises a first temperature measuring thermopile first temperature sensing material layer (210) and a first temperature measuring thermopile second temperature sensing material layer (212); a first insulating layer (230) and a second through hole (242) are provided between the first temperature measuring thermopile first temperature sensing material layer (210) and the first temperature measuring thermopile second temperature sensing material layer (212); and a second insulating layer (230) and a second through hole (242) are provided on the first temperature measuring thermopile second temperature sensing material layer (212). (232); the second temperature measuring thermopile (22) is formed on the surface of the hybrid substrate (12); the second temperature measuring thermopile (22) has two symmetrically distributed on both sides of the heating resistor (201), including a first temperature sensing material layer (220) of the second temperature measuring thermopile and a second temperature sensing material layer (222) of the second temperature measuring thermopile; a first insulating layer (230) and a third through hole (244) are provided between the first temperature sensing material layer (220) of the second temperature measuring thermopile and the second temperature sensing material layer (222) of the second temperature measuring thermopile, and a second insulating layer (232) is provided on the second temperature sensing material layer (222) of the second temperature measuring thermopile; The conductive through hole (300) penetrates the hybrid substrate (12), the silicon dioxide layer (110) and the silicon support layer (100), and is formed by connecting the metal conductive through hole (301), the conductive silicon column (310) and the welding block (320) in sequence from top to bottom; the metal conductive through hole (301) is filled with the fourth through hole (246), and the fourth through hole (246) penetrates the hybrid substrate (12) and the silicon dioxide layer (110); the center of the back cavity (340) is at the same position as the heating resistor (201) in the horizontal direction; the back cavity (340) penetrates the silicon support layer (100) in the vertical direction, and extends from the first surface (101) of the silicon support layer to the second surface (102) of the silicon support layer, and the depth is equal to the thickness of the silicon support layer (100).

2. The novel thermopile MEMS flow sensor that is easy to package according to claim 1 is characterized in that: The silicon dioxide layer (110) is a dense thin film, which is generated by one of LPCVD, plasma enhanced chemical vapor deposition or thermal oxidation; the polysilicon substrate (120) in the hybrid substrate (12) is obtained by epitaxial growth; and the silicon oxide thermal isolation region (140) is formed by filling a polysilicon groove array (130) formed by etching with a thermal oxidation method.

3. The novel thermopile MEMS flow sensor that is easy to package according to claim 1 is characterized in that: The hot junctions of the first temperature measuring thermopile (21) and the second temperature measuring thermopile (22) are arranged along different parallel lines parallel to the outside of the heating resistor (201), and the distance between the hot junction of the first temperature measuring thermopile (21) and the heating resistor (201) is closer than the distance between the second temperature measuring thermopile (22) and the heating resistor (201); the cold junctions of the first temperature measuring thermopile (21) and the second temperature measuring thermopile (22) are arranged along the same parallel line parallel to the outside of the heating resistor (201) and its extension line.

4. The novel thermopile MEMS flow sensor that is easy to package according to claim 3 is characterized in that: The distribution trend of the first temperature measuring thermopile (21) relative to the center line of the flow sensor is in an "eight" shape, the thermocouples close to the end of the heating resistor (201) are concentrated in a central area and arranged in parallel, and the thermocouples far from the end of the heating resistor are evenly distributed in two edge areas; the central area refers to an area closer to the heating resistor (201) along a central vertical line perpendicular to the arrangement direction of the temperature measuring thermopile, and the edge area refers to an area farther from the heating resistor (201) along a central vertical line perpendicular to the arrangement direction of the temperature measuring thermopile; the shape arrangement mode of the thermocouples of the first temperature measuring thermopile (21) in the area close to the heating resistor end and in the area between the end of the heating resistor is one of a curve type, a straight line type or a broken line type.

5. The novel thermopile MEMS flow sensor that is easy to package according to claim 1 is characterized in that: The heating resistor (201) and the environmental temperature measuring resistor (202) are made of the same material, which is one of metal, N-type polysilicon or P-type polysilicon; the first temperature sensing material layer (210) and the second temperature sensing material layer (212) of the first temperature measuring thermopile (21) are made of a combination of two of metal, N-type polysilicon or P-type polysilicon; the first temperature sensing material layer (220) and the second temperature sensing material layer (222) of the second temperature measuring thermopile (22) are made of a combination of two of metal, N-type polysilicon or P-type polysilicon; the first insulating layer (230) is made of a material of one of silicon oxide and silicon nitride, and is formed by one of PECVD or LPCVD techniques; the second insulating layer (232) is made of a material of one of silicon oxide and silicon nitride, and is formed by one of PECVD or LPCVD techniques.

6. The novel thermopile MEMS flow sensor that is easy to package according to claim 1 is characterized in that: The first through hole (240), the second through hole (242), the third through hole (244), the fourth through hole (246) and the fifth through hole (247) are all formed by dry etching processes such as RIE and IBE; the fourth through hole (246) is filled by metal sputtering, metal evaporation or electroplating; the material of the metal conductive through hole (301) is one of copper, gold, titanium, chromium, aluminum, platinum or tungsten; the material of the heating resistor lead (248), the environmental temperature measuring resistor lead (250), the front lead of the thermopile through hole (302) and the back welding block (320) is one of titanium, tungsten, chromium, platinum, aluminum or gold; and the conductive silicon column (310) is an independent silicon column generated by deep silicon etching.

7. The novel thermopile MEMS flow sensor that is easy to package according to claim 1 is characterized in that: The fourth through hole (246) is filled by one of metal sputtering, metal evaporation or electroplating; the material of the metal conductive through hole (301) is one of copper, gold, titanium, chromium, aluminum, platinum or tungsten.

8. The novel thermopile MEMS flow sensor that is easy to package according to claim 1 is characterized in that: The conductive silicon pillar (310) is an independent silicon pillar generated by deep silicon etching; the back cavity (340) is formed by deep silicon etching.

9. The novel thermopile MEMS flow sensor that is easy to package according to claim 1 is characterized in that: The number of the conductive through holes (300) is 12, which are respectively used for connecting the heating resistor (201), the environmental temperature measuring resistor (202), two pairs of first temperature measuring thermopiles (21), and two pairs of second temperature measuring thermopiles (22).

10. A method for preparing a novel thermopile MEMS flow sensor that is easy to package, used for the novel thermopile MEMS flow sensor that is easy to package as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: S1, providing a low-resistance silicon wafer as a silicon support layer (100), generating silicon dioxide on a first surface (101) of the silicon support layer (100), and forming a silicon dioxide layer (110); S2, epitaxially growing polycrystalline silicon on the silicon dioxide layer (110) to form a polycrystalline silicon substrate (120); S3, etching a groove array (130) on the polycrystalline silicon substrate (120); S4, performing oxidation filling on the groove array (130) by a thermal oxidation method to form a silicon oxide thermal isolation region (140); S5, generating a heating resistor (201), an environmental temperature measuring resistor (202), a first thermopile first temperature sensing material layer (210) and a second thermopile first temperature sensing material layer (220) on the surface of the hybrid substrate (12); S6, forming a first insulating layer (230) on the surface of the heating resistor (201), the environmental temperature measuring resistor (202), the first thermopile first temperature-sensitive material layer (210), the second thermopile first temperature-sensitive material layer (220), and the mixed substrate (12), and etching a first through hole (240), a second through hole (242), a third through hole (244), a fourth through hole (246), and a fifth through hole (247); S7, filling the fourth through hole (246) to form a metal conductive through hole (301); S8, generating a first thermopile second temperature-sensitive material layer (212), a second thermopile second temperature-sensitive material layer (222), a heating resistor lead (248), an environmental temperature-measuring resistor lead (250), and a thermopile lead (302) on the first insulating layer (230); S9, forming a second insulating layer (232) on the first thermopile second temperature-sensitive material layer (212), the second thermopile second temperature-sensitive material layer (222), the heating resistor lead (248), the environmental temperature-measuring resistor lead (250), and the thermopile lead (302); S10, forming a pressure welding block (320) on the second surface (102) of the silicon support layer, and performing deep silicon etching to generate a thermal isolation cavity (340) and a conductive silicon column (310).

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