A MEMS differential pressure chip

Abstract

This invention relates to a MEMS differential pressure chip, mainly composed of a three-layer structure. The first layer is a first silicon substrate, mainly containing a lower microchannel; the second layer is an intermediate layer, mainly containing heating and temperature sensing elements and a bonding layer; and the third layer is a second silicon substrate, mainly containing an upper microchannel and an overflow ring. A set of lead pads is provided on both sides of the upper center of the first silicon substrate, and leads are provided at both ends of the heating and temperature sensing elements to connect to the corresponding pads. Airflow outlets communicating with the microchannels are provided on one side of the upper surface of both the first and second silicon substrates. The microchannel of this invention has extremely high aerodynamic resistance, minimizes gas flow, is resistant to dust and humid environments, and operates stably and reliably. Simultaneously, the packaging structure has the advantages of high design flexibility, small size, and low cost. Finally, this invention is suitable for mass production.

Description

Technical Field

[0001] This utility model relates to the field of silicon microsensor chip technology, and in particular to a MEMS micro differential pressure chip and its fabrication method. Background Technology

[0002] MEMS (Micro-Electro-Mechanical Systems) silicon micro-pressure sensors, as a product of the integration of modern microelectronics and precision machining technologies, are closely related to the rise of the semiconductor industry in the second half of the 20th century. With breakthroughs in integrated circuit manufacturing processes, micro-mechanical structures began to be built on silicon-based materials. High-precision pressure detection was achieved through sensitive mechanisms such as piezoresistive, capacitive, and resonant sensing. This technological innovation has reduced the size of traditional pressure sensors to the millimeter or even micrometer level, while also offering advantages such as low power consumption, high sensitivity, and low mass production costs. Globally, the urgent demand for miniaturized and intelligent sensing devices in fields such as automotive electronics, healthcare, and industrial automation has further propelled the commercialization of MEMS pressure sensors. Many medical devices, such as pulmonary function instruments, ventilators, spirometers, sleep diagnostic equipment, and oxygen conservators, achieve their intended functions with the help of micro-differential pressure sensors (range less than 10 kPa).

[0003] Currently, there are two main technical routes for realizing micro differential pressure sensor chips. One is a micro differential pressure sensor chip based on a silicon film structure. Its basic working principle is that the measured pressure difference causes stress in the silicon film, changes the size of the piezoresistive or capacitive resistor, and outputs a voltage or current signal proportional to the input pressure difference. The other is a micro differential pressure sensor chip based on micro flow rate. Its basic working principle is that it has a heating element and two temperature-sensitive elements. The micro flow rate of gas caused by the pressure difference carries the heat generated by the heating element from upstream to downstream, causing the temperature fields of the upstream and downstream to become asymmetrical, and outputting a voltage signal proportional to the input pressure difference.

[0004] Micro-differential pressure sensor chips based on micro-flow rates have the following drawbacks: ① To measure flow rate, flow-based differential pressure sensors must be connected to the main flow channel. Bypass channels often require filters to protect the sensor from dust, humidity, or bacterial contamination. However, any pneumatic components between the main flow channel and the bypass channel increase flow resistance, leading to pressure drop. Therefore, the pressure difference measured by the pressure sensor is lower than the actual pressure in the main channel, resulting in inaccurate measurements. Additional pressure compensation is required, and the maximum tube length is limited. ② Dust, moisture, etc., can easily enter the sensor chip, degrading or even completely malfunctioning the output signal, ultimately causing system failure. ③ Designing gas flow channels on the package, whose geometry and dimensions determine the gas flow rate through the chip, results in low packaging design flexibility, large size and instability, and high manufacturing costs. For example, in medical device applications, the respiratory airflow contains a significant amount of humidity and is usually warmer than the ambient temperature. This can lead to condensation inside the device, with water droplets forming on the walls of bypass lines or the sensors themselves. If these droplets exceed a certain size or accumulate into larger droplets, they can alter the aerodynamic characteristics of the connecting lines and sensors, resulting in increased sensor signal output errors. In severe cases, this can completely block the sensor, rendering it inoperable and causing medical device malfunctions, or even endangering life and health. Utility Model Content

[0005] The purpose of this invention is to address the problems mentioned in the prior art by providing a MEMS micro differential pressure chip and its fabrication method. First, this invention solves the problems of insufficient pneumatic impedance in existing micro pressure sensors, which are easily affected by dust and humid environments, have limited pressure-feeding pipe length, and are not stable and reliable in operation. Simultaneously, this invention addresses the issues of low packaging structure design flexibility, large size, and high manufacturing cost. Finally, this invention solves the problem of the feasibility of large-scale mass production.

[0006] To achieve the above objectives, the technical solution provided by this utility model is as follows:

[0007] A MEMS differential pressure chip comprises a first silicon substrate and a second silicon substrate. A first dielectric layer and a second dielectric layer are disposed on the first silicon substrate, and a ring-shaped glass paste bonding layer is disposed on the underside of the second silicon substrate. The bonding layer is bonded to the second dielectric layer using a bonding process. The chip is characterized by:

[0008] a. A lower microchannel is provided in the middle of the first silicon substrate, including an inlet wide channel, a left narrow channel, a working area wide channel, a right narrow channel, and an outlet wide channel. There is a smooth transition channel between the wide channel and the narrow channel. The entire lower microchannel structure is symmetrical in all directions. An airflow inlet communicating with the lower microchannel is provided on the lower side of the first silicon substrate.

[0009] b. At least one set of upstream temperature sensing elements, heating elements, and downstream temperature sensing elements are provided on the first silicon substrate at a location within the wide flow channel of the working area, each spanning the wide flow channel.

[0010] c. A set of lead pads is provided on both sides of the middle part of the first silicon substrate. Leads are provided at both ends of the upstream temperature sensing element, the heating element and the downstream temperature sensing element to connect to the corresponding pads.

[0011] d. The second silicon substrate has an upper microchannel on its underside, which has the same structure and size as the lower microchannel of the first silicon substrate. An overflow ring is provided around the upper microchannel on the underside of the second silicon substrate.

[0012] e. The second silicon substrate is T-shaped. After the first and second silicon substrates are bonded together, the pad windows of the dielectric layer on the lower first silicon substrate are exposed on both sides of the T-shaped body.

[0013] f. An airflow outlet communicating with the upper microchannel is provided on one side of the second silicon substrate.

[0014] The further technical solution is as follows:

[0015] The heating element is composed of a dielectric and a metal composite film layer, wherein the metal film layer is a four-fold serpentine metal wire that forms a heating resistor; the upstream and downstream temperature sensing elements are composed of a dielectric and a metal composite film layer and are suspended between the upper and lower microchannels, wherein the metal film layer is an eight-fold serpentine metal wire that forms a temperature sensing resistor; the heating element and the two temperature sensing elements form a unit, and one or two units can be set on the first silicon substrate.

[0016] A further technical solution is as follows: the heating element, the upstream temperature sensing element, and the downstream temperature sensing element are composed of a dielectric and metal composite film layer. The first dielectric layer is prepared on the first silicon substrate, and the material is thermally oxidized silicon / LPCVD silicon nitride / LPCVD silicon oxide, which plays a role in structural support. The metal film layer is prepared on the first dielectric layer, and the material is metal Ti / Pt or Ti / Pt / Au. The second dielectric layer is prepared on the first dielectric layer to wrap the metal film layer, and the material is PECVD silicon oxide / PECVD silicon nitride, which plays a role in passivation protection and stress balance matching.

[0017] The beneficial effects of this utility model are as follows:

[0018] Compared with existing technologies, the MEMS differential pressure chip of this invention integrates a microfluidic channel and a heating and temperature sensing element. The miniaturized fluid channel achieves extremely high aerodynamic resistance on the order of 100 kPa / (ml / s), more than a thousand times higher than traditional pressure sensors, minimizing the gas flow rate through the differential pressure chip. It is unaffected by dust and humid environments, does not limit the length of the pressure-sensing pipe, and operates stably and reliably. Simultaneously, the packaging structure offers advantages such as high design flexibility, minimal and stable size, and low manufacturing cost. Finally, this invention is suitable for large-scale mass production. Attached Figure Description

[0019] Figure 1 This is a top view of the MEMS differential pressure chip structure of this utility model;

[0020] Figure 2 for Figure 1 Sectional view at point A-A;

[0021] Figure 3 for Figure 1 Cross-sectional view of BB section;

[0022] Figure 4 This is a schematic diagram of the first silicon substrate structure of this utility model;

[0023] Figure 5 for Figure 4 Sectional view at point A-A;

[0024] Figure 6 for Figure 4 The cross-sectional view is shown at point B-B;

[0025] Figure 7 A schematic diagram of a unit consisting of one heating element and two temperature sensing elements;

[0026] Figure 8 This is a schematic diagram of the second silicon substrate structure of this utility model;

[0027] Figure 9 for Figure 8 Sectional view at point A-A;

[0028] Figure 10 for Figure 8 Cross-sectional view at point B-B;

[0029] Figure 11 This is a schematic diagram of the microchannel and overflow ring structure of this utility model.

[0030] In the diagram, 1 represents the first silicon substrate, 11 the airflow inlet, 12 the lower microchannel, 121 the inlet wide channel, 122 the upstream narrow channel, 123 the working area wide channel, 124 the downstream narrow channel, 125 the outlet wide channel, and 126 the transition channel; 2 represents the second silicon substrate, 21 the airflow outlet, 22 the upper microchannel, 23 the overflow ring, 24 the lead pad via, 221 the outlet wide channel, 222 the downstream narrow channel, and 223 the working area. 224 is the upstream wide flow channel, 225 is the inlet wide flow channel, 226 is the transition flow channel, 3 is the upstream temperature sensing element, 4 is the heating element, 5 is the downstream temperature sensing element, 6 is the metal film layer, 7 is the thermal silicon oxide / LPCVD silicon nitride / LPCVD silicon oxide dielectric film layer, 8 is the PECVD silicon oxide / PECVD silicon nitride dielectric film layer, 9 is the glass paste bonding layer, 10 is the bonding cavity, 130 is the metal lead, and 131 is the metal pad. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] A MEMS differential pressure chip, specifically comprising the following components:

[0034] 1. For example Figure 1 , Figure 2 and Figure 3 As shown, the MEMS micro differential pressure chip is composed of a first silicon substrate 1 and a second silicon substrate 2. The first silicon substrate 1 is provided with a first dielectric layer 7 and a second dielectric layer 8. The second silicon substrate 2 is provided with an annular glass paste bonding layer 9. The bonding layer 9 is bonded to the second dielectric layer 8 through a bonding process, so that the first silicon substrate 1 and the second silicon substrate 2 are combined into a MEMS micro differential pressure chip.

[0035] 2. For example Figure 2 , Figure 4 As shown, a lower microchannel 12 is provided in the middle of the first silicon substrate 1, and a set of lead pads 131 are respectively provided on both sides of the middle of the first silicon substrate 1 (in the dielectric layer); Figure 2 , Figure 4 and Figure 11 As shown, the lower microchannel 12 of the first silicon substrate 1 consists of five parts, including an inlet wide channel 121, a left narrow channel 122, a working area wide channel 123, a right narrow channel 124, and an outlet wide channel 125. A smooth transition channel 126 connects the wide and narrow channels. Each channel has process bevels 12a on both sides. The entire lower microchannel 12 structure is symmetrical vertically and horizontally. Figure 4As shown, at least one set of upstream temperature sensing element 3, heating element 4 and downstream temperature sensing element (two sets in this embodiment) are provided on the first silicon substrate 1 at the position of the wide flow channel 123 in the working area. They span the wide flow channel 123 respectively. Leads 130 are provided at both ends of the upstream temperature sensing element 3, heating element 4 and downstream temperature sensing element and are connected to the corresponding pads 131.

[0036] like Figure 2 , Figure 5 As shown, the lower side of the first silicon substrate 1 is provided with an airflow inlet 11 that communicates with the lower microchannel 12.

[0037] 3. For example Figure 1 , Figure 2 , Figure 3 , Figure 8 and Figure 11 As shown, the upper microchannel 22 of the second silicon substrate 2 has the same structure and dimensions as the lower microchannel 12 of the first silicon substrate 1, and also consists of five parts: an outlet wide channel 221, a right-side narrow channel 222, a working area wide channel 223, a left-side narrow channel 224, and an inlet wide channel 225. There is a smooth transition channel between the wide and narrow channels, and the entire upper microchannel 22 structure is symmetrical vertically and horizontally. The overflow ring 23 of the second silicon substrate 2 consists of a rectangular shallow cavity with self-cureable etching, surrounding the upper microchannel 22. Figure 2 As shown, the wide flow channel 223 of the working area of ​​the second silicon substrate 2 is located a distance directly above the upstream temperature sensing element 3, the heating element 4, and the downstream temperature sensing element 5. Figure 1 , Figure 3 and Figure 8 As shown, the second silicon substrate 2 is T-shaped, with a narrower T-shaped section to expose the pad window 24 of the dielectric layer on the lower first silicon substrate 1 after the two silicon substrates are bonded. Additionally, as... Figure 1 , Figure 3 and Figure 8 As shown, the second silicon substrate 2 has a process bevel 2a on its T-shaped body, which is produced during the processing and has no special technical meaning.

[0038] like Figure 9 As shown, the upper side of the second silicon substrate 2 is provided with an airflow outlet 21 that communicates with the upper microchannel 22.

[0039] like Figure 2 As shown, the airflow inlet 11 and airflow outlet 21 of the first silicon substrate 1 and the second silicon substrate 2 can be equivalently interchanged. The airflow inlet 11 can be changed to the airflow outlet 11, and the airflow outlet 21 can be changed to the airflow inlet 21. At the same time, the inlet wide flow channel 121 is changed to the outlet wide flow channel 121, the outlet wide flow channel 125 is changed to the inlet wide flow channel 125, the outlet wide flow channel 221 is changed to the inlet wide flow channel 221, and the inlet wide flow channel 225 is changed to the outlet wide flow channel 225.

[0040] 4. For example Figure 2 , Figure 4 , Figure 5 and Figure 7 As shown, on the first silicon substrate 1, an upstream temperature sensing element 3, a heating element 4, and a downstream temperature sensing element 5 are arranged sequentially at a distance from each other at the position of the lower microchannel 12. They are all suspended in the middle of the upper and lower microchannels, and their geometry is a parallelogram. They are connected to the external pads 131 through leads 130.

[0041] See Figure 7 As shown, the heating element 4 is composed of a dielectric and a metal composite film layer, wherein the metal film layer 6 is a four-fold serpentine metal wire, which constitutes a heating resistor; the upstream temperature sensing element 3 and the downstream temperature sensing element 5 are located on the left and right sides of the heating element 4, and are composed of a dielectric and a metal composite film layer, suspended in the middle of the upper and lower microchannels, wherein the metal film layer 6 is an eight-fold serpentine metal wire, which constitutes a temperature sensing resistor; the heating element 4 and the two temperature sensing elements can form a unit, and a unit or a set of units can be set on the first silicon substrate 1.

[0042] like Figure 2 and Figure 7 As shown, the dielectric and metal composite film layer can be divided into three layers. The first dielectric layer 7 is prepared on the first silicon substrate 1, and the material is thermally oxidized silicon / LPCVD silicon nitride / LPCVD silicon oxide, which plays a role in structural support. The metal film layer 6 is prepared on the first dielectric layer 7, and the material is metal Ti / Pt or Ti / Pt / Au, which constitutes the heating resistor, the temperature sensing resistor, the metal lead 130, and the metal pad 131. The second dielectric layer 8 is prepared on the first dielectric layer 7 and wraps the metal film layer 6. The material is PECVD silicon oxide / PECVD silicon nitride, which plays a role in passivation protection and stress balance matching.

Claims

1. A MEMS differential pressure chip, comprising a first silicon substrate (1) and a second silicon substrate (2), wherein a first dielectric layer (7) and a second dielectric layer (8) are disposed on the first silicon substrate (1), and an annular glass paste bonding layer (9) is disposed on the underside of the second silicon substrate (2), wherein the bonding layer (9) is bonded to the second dielectric layer (8) by a bonding process, characterized in that: a. A lower microchannel (12) is provided in the middle of the first silicon substrate (1), including an inlet wide channel (121), a left narrow channel (122), a working area wide channel (123), a right narrow channel (124), and an outlet wide channel (125). There is a smooth transition channel (126) between the wide channel and the narrow channel. The entire structure of the lower microchannel (12) is symmetrical in all directions. An airflow inlet (11) communicating with the lower microchannel (12) is provided on the lower side of the first silicon substrate (1). b. At least one set of upstream temperature sensing element (3), heating element (4) and downstream temperature sensing element are provided on the first silicon substrate (1) at the position of the working area wide flow channel (123), which respectively span the wide flow channel (123). c. A set of lead pads (131) are provided on both sides of the middle part of the first silicon substrate (1). Leads (130) are provided at both ends of the upstream temperature sensing element (3), the heating element (4) and the downstream temperature sensing element (5) and connected to the corresponding pads (131); d. The second silicon substrate (2) has an upper microchannel (22) on its underside. The upper microchannel has the same structure and size as the lower microchannel (12) of the first silicon substrate (1). An overflow ring (23) is provided around the upper microchannel (22) on the underside of the second silicon substrate (2). e. The second silicon substrate (2) is T-shaped. After the first silicon substrate (1) and the second silicon substrate (2) are bonded together, the pad windows (24) of the dielectric layer on the first silicon substrate (1) are exposed on both sides of the T-shaped body. f. The upper side of the second silicon substrate (2) is provided with an airflow outlet (21) that communicates with the upper microchannel (22).

2. The MEMS differential pressure chip according to claim 1, characterized in that: The heating element (4) is composed of a dielectric and a metal composite film layer (6), wherein the metal film layer (6) is a four-fold serpentine metal wire that forms a heating resistor; the upstream temperature sensing element (3) and the downstream temperature sensing element (5) are composed of a dielectric and a metal composite film layer and are suspended in the middle of the lower microchannel, wherein the metal film layer (6) is an eight-fold serpentine metal wire that forms a temperature sensing resistor; the heating element (4) and the two temperature sensing elements form a unit, and one or two units are provided on the first silicon substrate (1).

3. A MEMS differential pressure chip according to claim 2, characterized in that: The heating element (4), the upstream temperature sensing element (3), and the downstream temperature sensing element (5) are composed of a dielectric and metal composite film layer. The first dielectric layer (7) is prepared on the first silicon substrate (1) and the material is thermal silicon oxide / LPCVD silicon nitride / LPCVD silicon oxide, which plays a structural support role. The metal film layer (6) is prepared on the first dielectric layer (7) and the material is metal Ti / Pt or Ti / Pt / Au. The second dielectric layer (8) is prepared on the first dielectric layer (7) to wrap the metal film layer (6) and the material is PECVD silicon oxide / PECVD silicon nitride, which plays a passivation protection and stress balance matching role.

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