Gas sensor based on micro-electro-mechanical ultrasonic transducer

Abstract

The invention provides a gas sensor based on a micro-electro-mechanical ultrasonic transducer, which comprises an electrical carrier plate provided with a hole; the electrical carrier plate is provided with a micro-electro-mechanical ultrasonic transducer electrically connected with the electrical carrier plate, and the micro-electro-mechanical ultrasonic transducer comprises a receiving end transducer arranged above the hole and a transmitting end transducer arranged below the hole; in addition, a plurality of groups of micro-electro-mechanical ultrasonic transducers form a micro-electro-mechanical ultrasonic transducer array. Compared with a traditional ultrasonic gas sensor, the gas sensor based on the micro-electro-mechanical ultrasonic transducer has the advantages of being small in size, high in integration level and the like by combining a semiconductor packaging process, the consistency of the sensor is improved, and the gas sensor is suitable for batch production.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and more specifically, to a gas sensor based on a microelectromechanical ultrasonic transducer. Background Technology

[0002] Gas sensors play a crucial role in environmental monitoring, industrial production, and healthcare. While traditional gas sensors can meet market demands to some extent, they still have shortcomings in terms of lifespan, reliability, power consumption, and integration.

[0003] Ultrasonic measurement, as a non-contact measurement technology, has advantages such as high precision, high reliability, and long lifespan, and has been widely used in fields such as liquid level measurement and flow detection. However, its application in the field of gas concentration detection, especially in miniaturization and integration, is still in its infancy.

[0004] Therefore, the existing technology has problems and needs further improvement and development. Summary of the Invention

[0005] (I) Purpose of the invention: In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a gas sensor based on a microelectro-mechanical ultrasonic transducer. By combining microelectro-mechanical systems (MEMS) technology and ultrasonic detection technology, the shortcomings of traditional ultrasonic gas sensors in terms of size, integration, and consistency are solved.

[0006] (II) Technical Solution: In order to solve the above-mentioned technical problems, this technical solution provides a gas sensor based on a microelectromechanical ultrasonic transducer, including an electrical carrier plate, wherein the electrical carrier plate has holes; two microelectromechanical ultrasonic transducers electrically connected to the electrical carrier plate are disposed on the electrical carrier plate, and the two microelectromechanical ultrasonic transducers include a receiving transducer disposed above the holes and a transmitting transducer disposed below the holes.

[0007] The gas sensor based on a microelectromechanical ultrasonic transducer includes a transmitting transducer comprising a second substrate having a back cavity and a second diaphragm covering the back cavity; a receiving transducer comprising a first substrate having a back cavity and a first diaphragm covering the back cavity; the second diaphragm of the transmitting transducer and the first diaphragm of the receiving transducer are arranged opposite to the surface of the electrical carrier plate in a horizontal direction.

[0008] The gas sensor based on a microelectromechanical ultrasonic transducer, wherein the second diaphragm of the transmitting transducer and the first diaphragm of the receiving transducer are symmetrically arranged with respect to the surface of the electrical carrier plate in the horizontal direction.

[0009] The gas sensor based on a microelectromechanical ultrasonic transducer, wherein the electrical carrier is a substrate or a printed circuit board.

[0010] The gas sensor based on a microelectromechanical ultrasonic transducer, wherein the transmitting transducer and the receiving transducer of the microelectromechanical ultrasonic transducer are electrically connected to and fixed on the electrical carrier plate via solder balls.

[0011] The gas sensor based on a microelectromechanical ultrasonic transducer has a gas inlet gap between the second substrate of the transmitting transducer and the electrical carrier plate, and between the first substrate of the receiving transducer and the electrical carrier plate, due to the support of the solder balls.

[0012] The gas sensor based on a microelectromechanical ultrasonic transducer, wherein the receiving transducer and the transmitting transducer are electrically connected to the electrical carrier board via a flip-chip packaging method.

[0013] The gas sensor based on a microelectromechanical ultrasonic transducer includes an arithmetic and / or power supply circuit module and a temperature sensor on the electrical carrier plate. The arithmetic and / or power supply circuit module and the temperature sensor are electrically connected to and fixed on the electrical carrier plate via solder balls.

[0014] The gas sensor based on a microelectromechanical ultrasonic transducer includes an electrical carrier plate with multiple conductor structures inside for connecting the microelectromechanical ultrasonic transducer and other electrical or sensor modules.

[0015] The gas sensor based on a microelectromechanical ultrasonic transducer has a horizontal dimension of less than 3 cm; or a horizontal dimension of less than 1 cm; or a horizontal dimension of less than 0.5 cm.

[0016] The gas sensor based on a microelectromechanical ultrasonic transducer, wherein the distance between the transmitting transducer and the receiving transducer is less than 1 cm; or the distance between the transmitting transducer and the receiving transducer is less than 5 mm; or the distance between the transmitting transducer and the receiving transducer is less than 2 mm.

[0017] The gas sensor based on a microelectromechanical ultrasonic transducer includes an electrical carrier plate consisting of three substrates, from bottom to top: a first substrate, a second substrate, and a third substrate. The first substrate and the third substrate are covered by a second substrate with a cavity. Mounting holes are provided on the first substrate and the third substrate, and the mounting holes and the cavity communicate to form holes on the electrical carrier plate.

[0018] The gas sensor based on a microelectromechanical ultrasonic transducer is wherein the first substrate, the second substrate, and the third substrate are electrically connected and fixed together by solder balls.

[0019] The gas sensor based on a microelectromechanical ultrasonic transducer, wherein the second substrate of the transmitting transducer is fixed to the inner wall of the third substrate facing the cavity, and the first substrate of the receiving transducer is fixed to the inner wall of the first substrate facing the cavity.

[0020] The gas sensor based on a microelectromechanical ultrasonic transducer includes an additional hole and two enclosed microelectromechanical ultrasonic transducers on the electrical carrier plate. The two enclosed microelectromechanical ultrasonic transducers are a transmitting transducer and a receiving transducer positioned above and below the additional hole. One of the enclosed microelectromechanical ultrasonic transducers has a receiving dry film disposed outside the receiving transducer, and the other enclosed microelectromechanical ultrasonic transducer has a transmitting dry film disposed outside the transmitting transducer. The receiving dry film and the transmitting dry film are used to seal the background gas between the receiving transducer and the transmitting transducer.

[0021] The gas sensor based on a microelectromechanical ultrasonic transducer, wherein the first diaphragm of the receiving transducer and the second diaphragm of the transmitting transducer are diaphragms with slits.

[0022] The gas sensor based on a microelectromechanical ultrasonic transducer allows a small amount of gas to enter the gas-containing space formed by the holes through the gaps in the slits of the first diaphragm of the receiving transducer and the slits in the second diaphragm of the transmitting transducer.

[0023] The gas sensor based on a microelectromechanical ultrasonic transducer, wherein the slit divides the second diaphragm of the transmitting transducer or the first diaphragm of the receiving transducer into multiple regions.

[0024] The gas sensor based on a microelectromechanical ultrasonic transducer, wherein the diaphragm of the slit is a double sandwich diaphragm, comprising a first sandwich diaphragm and a second sandwich diaphragm; the first sandwich diaphragm comprises, from bottom to top, a first bottom electrode layer, a first piezoelectric layer and a first top electrode layer; the second sandwich diaphragm comprises, from bottom to top, a second bottom electrode layer, a second piezoelectric layer and a second top electrode layer; a seed layer exists between the first sandwich diaphragm and the second sandwich diaphragm.

[0025] The gas sensor based on a microelectromechanical ultrasonic transducer, wherein the materials of the first piezoelectric layer and the second piezoelectric layer are aluminum nitride, doped aluminum nitride, lead zirconate titanate, and doped lead zirconate titanate; and the electrode materials of the first bottom electrode layer, the first top electrode layer, the second bottom electrode layer, and the second top electrode layer are molybdenum, platinum, and gold.

[0026] (III) Beneficial effects: The gas sensor based on microelectromechanical ultrasonic transducer provided by the present invention, combined with semiconductor packaging technology, has advantages such as small size and high integration compared with traditional ultrasonic gas sensors, and also improves the consistency of the sensor, making it suitable for mass production. Attached Figure Description

[0027] Figure 1A This is a top view of the structure of the first preferred embodiment of the gas sensor based on a microelectromechanical ultrasonic transducer of the present invention;

[0028] Figure 1B yes Figure 1A A schematic diagram of the cross-sectional structure formed along A1A2;

[0029] Figure 1C yes Figure 1A A schematic diagram of the cross-sectional structure formed along B1B2;

[0030] Figure 2 This is a schematic diagram of the second preferred embodiment of the gas sensor based on a microelectromechanical ultrasonic transducer of the present invention;

[0031] Figure 3A This is a top view of the structure of the third preferred embodiment of the gas sensor based on a microelectromechanical ultrasonic transducer of the present invention;

[0032] Figure 3B yes Figure 3A A schematic diagram of the cross-sectional structure formed along D1D2;

[0033] Figure 4A This is a schematic diagram of the fourth preferred embodiment of the gas sensor based on a microelectromechanical ultrasonic transducer of the present invention, which has a slit-type multi-diaphragm structure;

[0034] Figure 4B yes Figure 4A A schematic diagram of the cross-sectional structure formed along C1C2;

[0035] Figure 5 This is a schematic diagram of the structure of the gas sensor comprising an array of microelectromechanical ultrasonic transducers in the fifth preferred embodiment of the present invention;

[0036] Figure 6(a) is a schematic diagram of the principle of the accommodating space carrying the background gas in the gas sensor based on the microelectromechanical ultrasonic transducer of the present invention;

[0037] Figure 6(b) is a schematic diagram of the principle of testing the gas under test in the accommodating space between the transmitting and receiving transducers in the gas sensor based on the microelectromechanical ultrasonic transducer of the present invention.

[0038] Figure label:

[0039] Q100 - Electrical substrate, QC100 - Hole, Q110 - First substrate, Q120 - Second substrate, Q130 - Third substrate;

[0040] 100, 100' - Receiver transducer; 200, 200' - Transmitter transducer;

[0041] U100 - Operation and / or power supply circuit module, T100 - Temperature sensor;

[0042] S100 - First substrate, S200 - Second substrate, S100' - Third substrate, S200' - Fourth substrate, D100 - First diaphragm, D200 - Second diaphragm, D100' - Third diaphragm, D200' - Fourth diaphragm, MR100 - Receiver dry film, MR200 - Transmitter dry film;

[0043] F100 - First diaphragm region, F200 - Second diaphragm region, F300 - Third diaphragm region, F400 - Fourth diaphragm region; P110, P310 - Electrode contacts;

[0044] BE401 - First bottom electrode layer, PZ401 - First piezoelectric layer, TE401 - First top electrode layer, BE402 - Second bottom electrode layer, PZ402 - Second piezoelectric layer, TE402 - Second top electrode layer, BS400 - Seed layer;

[0045] E101 - Eleventh electrode contact, E103 - Thirteenth electrode contact, E201 - Twenty-first electrode contact, E202 - Twenty-second electrode contact, E203 - Twenty-third electrode contact, E204 - Twenty-fourth electrode contact, E211 - Thirty-first electrode contact, E212 - Thirty-second electrode contact, E221 - Forty-first electrode contact, E222 - Forty-second electrode contact;

[0046] M101 - Eleventh pad, M103 - Thirteenth pad, M201 - Twenty-first pad, M203 - Twenty-third pad, M211 - Thirty-first pad, M212 - Thirty-second pad, M221 - Forty-first pad, M222 - Forty-second pad;

[0047] W101 - Eleventh solder ball, W103 - Thirteenth solder ball, W201 - Twenty-first solder ball, W203 - Twenty-third solder ball, W211 - Thirty-first solder ball, W212 - Thirty-second solder ball, W221 - Forty-first solder ball, W222 - Forty-second solder ball;

[0048] W301 - First welding point, W302 - Second welding point, W303 - Third welding point, W304 - Fourth welding point, W305 - Fifth welding point, W306 - Sixth welding point, W307 - Seventh welding point, W308 - Eighth welding point;

[0049] H201 - First conductor structure, N201 - Second conductor structure, C201 - Third conductor structure, N211 - Fourth conductor structure, H211 - Fifth conductor structure, H203 - Sixth conductor structure, N203 - Seventh conductor structure, H101 - Eleventh conductor structure, N101 - Twelfth conductor structure, C101 - Thirteenth conductor structure, N212 - Fourteenth conductor structure, H212 - Fifteenth conductor structure, H103 - Sixteenth conductor structure, N103 - Seventeenth conductor structure, H221 - Twenty-first conductor structure, N221 - Twenty-second conductor structure, H222 - Twenty-third conductor structure, N222 - Twenty-fourth conductor structure;

[0050] WL10 - Tenth Metal Wire, WL11 - Eleventh Metal Wire, WL20 - Twentieth Metal Wire, WL21 - Twenty-first Metal Wire;

[0051] K11 - Eleventh Connecting Node, K12 - Twelfth Connecting Node, K21 - Twenty-first Connecting Node, K22 - Twenty-second Connecting Node, K31 - Thirty-first Connecting Node, K32 - Thirty-second Connecting Node;

[0052] G12 - Twelfth connecting conductor, G13 - Thirteenth connecting conductor, G14 - Fourteenth connecting conductor, G22 - Twenty-second connecting conductor, G24 - Twenty-fourth connecting conductor, G31 - Thirty-first connecting conductor;

[0053] FX100 - Gas to be tested, GX100 - Sample distribution of the gas to be tested, WA100 - First sound wave, WA200 - Second sound wave. Detailed Implementation

[0054] The present invention will be further described in detail below with reference to preferred embodiments. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0055] The accompanying drawings are schematic diagrams of embodiments of the present invention. It should be noted that these drawings are for illustrative purposes only and are not drawn to scale, and should not be construed as limiting the actual scope of protection of the present invention.

[0056] This invention relates to a gas sensor based on microelectromechanical ultrasonic transducers (MEMS), comprising an electrical carrier plate Q100 with a hole QC100, and at least two MEMS ultrasonic transducers electrically connected to the electrical carrier plate Q100. When there are two MEMS ultrasonic transducers on the electrical carrier plate, each transducer includes a transmitting transducer 200 (Tx, Transmit) and a receiving transducer 100 (RX, Receive). The transmitting transducer 200 and the receiving transducer 100 are respectively disposed above and below the hole QC100, such that the transmitting transducer 200 and the receiving transducer 100 are stacked vertically on the surface of the electrical carrier plate Q100. The second diaphragm D200 of the transmitting transducer 200 and the first diaphragm D100 of the receiving transducer 100 are symmetrically arranged horizontally on the surface of the electrical carrier plate Q100. In a first preferred embodiment of the gas sensor, the aperture QC100 may be a mounting hole. The receiving transducer 100 and the transmitting transducer 200 are stacked vertically on the surface of the aperture QC100 of the electrical carrier plate Q100, forming a gas containment space with the inner wall of the aperture QC100.

[0057] The gas sensor based on the microelectromechanical ultrasonic transducer of the present invention introduces air into the gas containing space through the gap between the second substrate S200 of the receiving transducer 200 and the electrical carrier plate Q100, and the gap between the first substrate S100 of the transmitting transducer 100 and the electrical carrier plate Q100. In a fourth preferred embodiment of the gas sensor based on the microelectromechanical ultrasonic transducer of the present invention, a small amount of gas enters the gas containing space through the gap between the diaphragm structure with slits of the first diaphragm D100 of the receiving transducer 100 and the second diaphragm D200 of the transmitting transducer 200.

[0058] Preferably, the electrical carrier Q100 can be a substrate or a printed circuit board (PCB).

[0059] The first preferred embodiment of the gas sensor based on a microelectromechanical ultrasonic transducer of the present invention is as follows: Figure 1A , Figure 1B and Figure 1CAs shown, the two microelectromechanical ultrasonic transducers include a transmitting transducer 200 and a receiving transducer 100. The receiving transducer 100 includes a first substrate S100 having a back cavity and a first diaphragm D100 disposed on the first substrate S100 covering the back cavity. The transmitting transducer 200 includes a second substrate S200 having a back cavity and a second diaphragm D200 disposed on the second substrate S200 covering the back cavity.

[0060] The second diaphragm D200 on the second substrate S200 of the transmitter transducer 200 faces the inside of the hole QC100 on the electrical carrier plate Q100. The transmitter transducer 200 is electrically connected to the electrical carrier plate Q100 through a plurality of electrode contacts on the second substrate S200. The electrode contacts include a twenty-first electrode contact E201, a twenty-second electrode contact E202, a twenty-third electrode contact E203, and a twenty-fourth electrode contact E204.

[0061] The first diaphragm D100 on the first substrate S100 of the receiving transducer 100 faces the inside of the hole QC100 on the electrical carrier plate Q100, and the receiving transducer 100 is electrically connected to the electrical carrier plate Q100 through a plurality of electrode contacts on the first substrate S100.

[0062] Preferably, the receiving transducer 100 and the transmitting transducer 200 can be disposed in the space outside the hole QC100 on the electrical carrier board Q100, such as... Figure 1B As shown.

[0063] The gas sensor of the present invention may have an arithmetic and / or power supply circuit module U100 and a temperature sensor T100 disposed on an electrical carrier plate Q100. The arithmetic and / or power supply circuit module U100 and the temperature sensor T100 are electrically connected to the electrode contacts of the receiving transducer and / or the transmitting transducer through a metal conductor layer embedded in the electrical carrier plate Q100.

[0064] The microelectromechanical ultrasonic transducer of the present invention, such as Figure 1B As shown, the second diaphragm D200 of the transmitting transducer 200 is disposed on the second substrate S200, and the first diaphragm D100 of the receiving transducer 100 is disposed on the first substrate S100. The first diaphragm D100 and the second diaphragm D200 are disposed opposite to each other. The transmitting transducer 200 and the receiving transducer 100 are stacked vertically. The transmitting transducer 200 and the receiving transducer 100 are electrically connected to the electrical carrier board Q100 through a flip-chip packaging method.

[0065] Specifically, taking the transmitter transducer 200 as an example, the electrode layer of D200 in the second diaphragm of the transmitter transducer 200 is connected to the twenty-first electrode contact E201 and the twenty-third electrode contact E203 on the surface of the second substrate S200. The twenty-first electrode contact E201 is electrically connected to the twenty-first pad M201 on the surface of the electrical carrier Q100 through the twenty-first solder ball W201. The twenty-third electrode contact E203 is electrically connected to the twenty-third pad M203 on the surface of the electrical carrier Q100 through the twenty-third solder ball W203. Through the above connection, the second substrate S200 of the transmitter transducer 200 is fixed on one side surface of the electrical carrier Q100.

[0066] Taking the receiving transducer 100 as an example, the electrode layer in the first diaphragm D100 of the receiving transducer 100 is connected to the eleventh electrode contact E101 and the thirteenth electrode contact E103 on the surface of the first substrate S100. The eleventh electrode contact E101 is electrically connected to the eleventh pad M101 on the surface of the electrical carrier Q100 through the eleventh solder ball W101. The thirteenth electrode contact E103 is electrically connected to the thirteenth pad M103 on the surface of the electrical carrier Q100 through the thirteenth solder ball W103. Through the above connection, the substrate S100 of the receiving transducer 100 is fixed on the other side surface of the electrical carrier Q100.

[0067] The thirty-first electrode contact E211 and the thirty-second electrode contact E212 on the operation and / or power supply circuit module U100 are electrically connected to and fixed to the thirty-first solder pad M211 and the thirty-second solder pad M212 on the electrical carrier board Q100 through the thirty-first solder ball W211 and the thirty-second solder ball W212, respectively.

[0068] The electrical carrier board Q100 contains multiple conductor structures for connecting the microelectromechanical ultrasonic transducer and other electrical or sensor modules. For example, an electrical connection from the 21st pad M201 to the 31st pad M211 is achieved through the first conductor structure H201, the second conductor structure N201, the third conductor structure C201, the fourth conductor structure N211, and the fifth conductor structure H211 embedded inside the electrical carrier board Q100, which is also an electrical connection from the transmitting transducer 200 to the computing and / or power supply circuit module U100; an electrical connection from the 11th pad M101 to the 32nd pad M212 is achieved through the 11th conductor structure H101, the 12th conductor structure N101, the 13th conductor structure C101, the 14th conductor structure N212, and the 15th conductor structure H212 embedded inside the electrical carrier board Q100, which is also an electrical connection from the receiving transducer 100 to the computing and / or power supply circuit module U100. The electrical carrier board Q100 also contains a sixth conductor structure H203 and a seventh conductor structure N203 for electrically connecting the transmitter transducer 200 to other electrical or sensor modules; furthermore, it also contains a sixteenth conductor structure H103 and a seventeenth conductor structure N103 for electrically connecting the receiver transducer 100 to other electrical or sensor modules.

[0069] Preferably, the horizontal dimension of the gas sensor based on the microelectromechanical ultrasonic transducer of the present invention is less than 3 cm; more preferably, the horizontal dimension of the gas sensor is less than 1 cm; even more preferably, the horizontal dimension of the gas sensor is less than 0.5 cm.

[0070] The distance between the transmitting transducer 200 and the receiving transducer 100 of the present invention is mainly determined by the thickness of the electrical carrier board Q100 and the thickness of the electrical connection structure. Specifically, the thickness of the electrical connection structure can be the height of the solder ball.

[0071] In the gas sensor based on a microelectromechanical ultrasonic transducer of the present invention, the electrical carrier plate Q100 and the electrical connection structure are mass-produced using semiconductor technology, resulting in a high degree of thickness consistency, far exceeding that of traditional assembly methods. Therefore, the consistency of the final gas sensor, such as sensitivity consistency, can be guaranteed. Furthermore, the thickness of the electrical carrier plate Q100 and the electrical connection structure is relatively small, thus the thickness of the gas sensor based on the microelectromechanical ultrasonic transducer of the present invention can be kept small.

[0072] Preferably, the distance between the transmitting transducer 200 and the receiving transducer 100 is less than 1 cm; more preferably, the distance between the transmitting transducer 200 and the receiving transducer 100 is less than 5 mm; even more preferably, the distance between the transmitting transducer 200 and the receiving transducer 100 is less than 2 mm.

[0073] like Figure 1C As shown, the forty-first electrode contact E221 and the forty-second electrode contact E222 on the temperature sensor T100 are electrically connected to and fixed to the forty-first solder pad M221 and the forty-second solder pad M222 on the electrical carrier board Q100 through the forty-first solder ball W221 and the forty-second solder ball W222, respectively. The electrical connection between the temperature sensor T100 and other electrical or sensor modules is achieved through the twenty-first conductor structure H221, the twenty-second conductor structure N221, the twenty-third conductor structure H222, and the twenty-fourth conductor structure N222 embedded inside the electrical carrier board Q100.

[0074] The transmitting transducer 200 includes a second substrate S200 having a back cavity and a second diaphragm D200 covering the back cavity; the receiving transducer 100 includes a first substrate S100 having a back cavity and a first diaphragm D100 covering the back cavity.

[0075] The electrical connection structure between the second substrate S200 of the transmitter transducer 200 and the first substrate S100 of the receiver transducer 100 and the electrical carrier Q100 occupies only a limited area. Therefore, sufficient gaps are left between the second substrate S200 and the electrical carrier Q100, and between the first substrate S100 and the electrical carrier Q100, so that the gas flow FX100 of the gas to be measured can flow into and fill the space between the transmitter transducer 200 and the receiver transducer 100 through these gaps, and form a stable sample distribution GX100.

[0076] The above-described structure of the gas sensor of this invention can significantly reduce the horizontal dimension of the gas sensor based on a microelectromechanical ultrasonic transducer, wherein the horizontal direction is parallel to the surface of the electrical carrier plate Q100. Because microelectromechanical ultrasonic transducers are very suitable for connection to circuit carriers such as substrates using semiconductor packaging processes, the microelectromechanical ultrasonic transducer is connected to the electrical carrier plate Q100 via semiconductor packaging. However, the structure of the microelectromechanical ultrasonic transducer of this invention is not suitable for traditional piezoelectric ceramic ultrasonic transducers, as traditional piezoelectric ceramic ultrasonic transducers cannot be connected to the electrical carrier plate Q100 via semiconductor packaging. Compared with the assembly method of traditional piezoelectric ceramic ultrasonic transducers and circuit carriers, this assembly method offers higher consistency, better reliability, and is suitable for mass production.

[0077] The second preferred embodiment of the gas sensor based on a microelectromechanical ultrasonic transducer of the present invention is as follows: Figure 2 As shown, the electrical carrier board Q100 employs a three-layer substrate (or PCB) stacked vertically, comprising a first substrate Q110, a second substrate Q120, and a third substrate Q130 from bottom to top. The first substrate Q110 and the third substrate Q130 cover the second substrate Q120, which has a cavity. Mounting holes are provided on the first substrate Q110 and the third substrate Q130. In this invention, a microelectromechanical ultrasonic transducer can be placed inside the cavity of the second substrate Q120. The mounting holes and the cavity communicate to form the aperture of the gas sensor. The second substrate S200 of the transmitting transducer 200 is fixed to the inner wall of the third substrate Q130 facing the cavity, and the first substrate S100 of the receiving transducer 100 is fixed to the inner wall of the first substrate Q110 facing the cavity. The second diaphragm D200 of the transmitting transducer 200 and the first diaphragm D100 of the receiving transducer 100 are arranged opposite to each other, or the second diaphragm D200 of the transmitting transducer 200 and the first diaphragm D100 of the receiving transducer 100 are arranged symmetrically in the horizontal direction. The transmitting transducer 200, the receiving transducer 100, and the inner wall of the hole together constitute a gas containment space.

[0078] In this preferred embodiment, the 21st electrode contact E201 and the 23rd electrode contact E203 of the transmitting transducer 200 are electrically connected to the 21st and 23rd pads M201 and M203 of the electrical carrier board Q100 via the 20th metal line WL20 and the 21st metal line WL21. Specifically, the 21st electrode contact E201 is connected to the 8th solder point W308, and the 21st pad M201 is connected to the 7th solder point W307. The 8th solder point W308 and the 7th solder point W307 are electrically connected via the 21st metal line WL21. The 23rd electrode contact E203 is connected to the 6th solder point W306, and the 23rd pad M203 is connected to the 5th solder point W305. The 6th solder point W306 and the 5th solder point W305 are electrically connected via the 20th metal line WL20.

[0079] In this preferred embodiment, the eleventh electrode contact E101 and the thirteenth electrode contact E103 of the receiving transducer 100 are electrically connected to the eleventh pad M101 and the thirteenth pad M103 of the electrical carrier board Q100 via the tenth metal line WL10 and the eleventh metal line WL11. Specifically, the eleventh electrode contact E101 is connected to the second solder point W302, the eleventh pad M101 is connected to the first solder point W301, and the second solder point W302 is electrically connected to the first solder point W301 via the eleventh metal line WL11; the thirteenth electrode contact E103 is connected to the fourth solder point W304, the thirteenth pad M103 is connected to the third solder point W303, and the fourth solder point W304 is electrically connected to the third solder point W303 via the tenth metal line WL10.

[0080] In a preferred embodiment, the electrical carrier board Q100 is further provided with an operational and / or power supply circuit module U100 and a temperature sensor T100. The operational and / or power supply circuit module U100 is electrically connected to other electrical or sensor modules through the eleventh connection node K11, the twelfth connection node K12, and the twelfth connection conductor G12 and the fourteenth connection conductor G14 inside the electrical carrier board Q100; the temperature sensor T100 is electrically connected to other electrical or sensor modules through the twenty-first connection node K21, the twenty-second connection node K22, and the twenty-second connection conductor G22 and the twenty-fourth connection conductor G24 inside the electrical carrier board Q100.

[0081] In this preferred embodiment, the first substrate Q110, the second substrate Q120, and the third substrate Q130 are electrically connected and fixed together using solder balls. Specifically, the first substrate Q110 and the second substrate Q120 are electrically connected and fixed together through a 32nd connection node K32 containing solder balls, and the second substrate Q120 and the third substrate Q130 are electrically connected and fixed together through a 31st connection node K31 containing solder balls. The second substrate Q120 has a 31st connecting conductor G31 inside for electrically connecting the 32nd connection node K32 and the 31st connection node K31 on the surface of the second substrate Q120. The first substrate Q110 also has a 13th connecting conductor G13 inside for electrically connecting other electrical or sensor modules.

[0082] More preferably, the first substrate Q110, the second substrate Q120, and the third substrate Q130 are electrically connected and fixed using other industry-known connection methods, which will not be elaborated upon in this invention. Sufficient gaps are maintained between the first substrate Q110, the second substrate Q120, and the third substrate Q130 in this invention, and these gaps are used for the inflow of the gas to be tested.

[0083] In the gas sensor based on the microelectromechanical ultrasonic transducer of this invention, the electrical carrier plate Q100 and the electrical connection structure are mass-produced using semiconductor technology, resulting in a high degree of thickness consistency, far exceeding that of traditional assembly methods. Therefore, the consistency of the final gas sensor, such as the consistency of sensitivity, can be guaranteed.

[0084] The third preferred embodiment of the gas sensor based on a microelectromechanical ultrasonic transducer of the present invention is as follows: Figure 3A and Figure 3B As shown, the circuit includes two holes on the electrical carrier board Q100. Two microelectromechanical ultrasonic transducers (MEMS) are positioned above and below one of the holes, each including a transmitting transducer 200 and a receiving transducer 100. Two enclosed MEMS ultrasonic transducers are positioned above and below the other hole. The two MEMS ultrasonic transducers and the two enclosed MEMS ultrasonic transducers are connected to the computational and / or power supply circuit module U100.

[0085] The two microelectromechanical ultrasonic transducers are a transmitting transducer 200 and a receiving transducer 100, respectively. The receiving transducer 100 includes a first substrate S100 with a back cavity and a first diaphragm D100 disposed on the first substrate S100 covering the back cavity. The transmitting transducer 200 includes a second substrate S200 with a back cavity and a second diaphragm D200 disposed on the second substrate S200 covering the back cavity. There is a gap between the second substrate S200 of the transmitting transducer 200 and the first substrate S100 of the receiving transducer 100 and the electrical carrier Q100. The gas to be tested FX100 enters the accommodating space through the gap and mixes with the background gas to form a sample distribution GX100 of the gas to be tested.

[0086] The two enclosed microelectromechanical ultrasonic transducers are similar in structure to the two microelectromechanical ultrasonic transducers in the first and second preferred embodiments in that the enclosed microelectromechanical ultrasonic transducer includes a transmitting transducer 200' and a receiving transducer 100'. The transmitting transducer 200' of the enclosed microelectromechanical ultrasonic transducer has the same structure as the transmitting transducer 200 of the microelectromechanical ultrasonic transducer in the first and second preferred embodiments. The receiving transducer 100' of the enclosed microelectromechanical ultrasonic transducer has the same structure as the receiving transducer 100 of the microelectromechanical ultrasonic transducer in the first and second preferred embodiments. Different numbers are used in this embodiment to distinguish the enclosed microelectromechanical ultrasonic transducer from the microelectromechanical ultrasonic transducer in the figures and descriptions.

[0087] The receiving transducer 100' includes a third substrate S100' having a back cavity, and a third diaphragm D100' disposed on the third substrate S100' covering the back cavity; the transmitting transducer 200' includes a fourth substrate S200' having a back cavity, and a fourth diaphragm D200' disposed on the fourth substrate S200' covering the back cavity.

[0088] The two enclosed MEMS ultrasonic transducers differ structurally from the two MEMS ultrasonic transducers in the first and second preferred embodiments in that: the two enclosed MEMS ultrasonic transducers are the receiving transducer 100' and the transmitting transducer 200', which are positioned above and below another hole QC100'; a receiving dry film MR100 is disposed on the outside of the receiving transducer 100' of one enclosed MEMS ultrasonic transducer, and a transmitting dry film MR200 is disposed on the outside of the transmitting transducer 200' of the other enclosed MEMS ultrasonic transducer; the receiving dry film MR100 and the transmitting dry film MR200 are used to encapsulate the receiving transducer and the transmitting transducer.

[0089] The receiving transducer 100' and the transmitting transducer 200' of the two enclosed microelectromechanical ultrasonic transducers of the present invention are stacked vertically on the surface of another hole QC100' of the electrical carrier plate Q100, forming a space for containing background gas together with the inner wall of the other hole QC100', the receiving dry film MR100 and the transmitting dry film MR200.

[0090] The background gas refers to the original gas or basic gas that has not been mixed with the gas being tested.

[0091] The dry film structure of the enclosed microelectromechanical ultrasonic transducer described in this invention prevents the gas to be detected from entering the gas containment space surrounded by the dry film encapsulation structure, thereby enabling differential measurement with the receiving and transmitting transducers of the microelectromechanical ultrasonic transducer, suppressing common-mode interference, and improving the anti-drift characteristics of the gas sensor.

[0092] The fourth preferred embodiment of the gas sensor based on a microelectromechanical ultrasonic transducer of the present invention, as follows: Figure 4A and Figure 4B The first diaphragm D100 of the receiving transducer 100 and the second diaphragm D200 of the transmitting transducer 200, as shown, are diaphragms with slits. Preferably, the slits are cross-shaped slits. These slits divide the second diaphragm D200 of the transmitting transducer 200 or the first diaphragm D100 of the receiving transducer 100 into four triangular regions: a first diaphragm region F100, a second diaphragm region F200, a third diaphragm region F300, and a fourth diaphragm region F400. Several electrode contacts P110 and P310 are distributed around the periphery of each diaphragm region.

[0093] Taking the receiver transducer 100 of the present invention having a slit-type multi-diaphragm structure as an example, such as Figure 4B As shown, the first diaphragm D100 is constructed on the substrate S100, and S100 has a back cavity. Taking the fourth diaphragm region F400 of the first diaphragm D100 as an example, its structure adopts a bimorph structure. The bimorph structure includes a first bimorph diaphragm and a second bimorph diaphragm. The first bimorph diaphragm includes, from bottom to top, a first bottom electrode layer BE401, a first piezoelectric layer PZ401, and a first top electrode layer TE401. The second bimorph diaphragm includes, from bottom to top, a second bottom electrode layer BE402, a second piezoelectric layer PZ402, and a second top electrode layer TE402. A seed layer BS400 is also present between the first bimorph diaphragm and the second bimorph diaphragm.

[0094] Preferably, the materials of the first substrate S100 and the second substrate S200 are silicon; the materials of the first piezoelectric layer PZ401 and the second piezoelectric layer PZ402 can be aluminum nitride, doped aluminum nitride, lead zirconate titanate, or doped lead zirconate titanate; the electrode materials of the first bottom electrode layer BE401, the first top electrode layer TE401, the second bottom electrode layer BE402, and the second top electrode layer TE402 can be molybdenum, platinum, gold, etc.

[0095] It is worth noting that, in the fourth preferred embodiment of the present invention, the second diaphragm D200 of the transmitting transducer 200 or the first diaphragm D100 of the receiving transducer 100 having a slit-type multi-diaphragm structure is only intended to illustrate the specific possible structure of the second diaphragm D200 of the transmitting transducer 200 or the first diaphragm D100 of the receiving transducer 100, and is not intended to limit other possible structures.

[0096] The present invention also provides a gas sensor, which may include multiple sets of microelectromechanical ultrasonic transducers. The multiple sets of microelectromechanical ultrasonic transducers may form a microelectromechanical ultrasonic transducer array. Each set of microelectromechanical ultrasonic transducers refers to two microelectromechanical ultrasonic transducers arranged above and below a hole on an electrical carrier plate, or two closed microelectromechanical ultrasonic transducers, or a combination of two microelectromechanical ultrasonic transducers and two closed microelectromechanical ultrasonic transducers. No limitation is made here.

[0097] Preferred, such as Figure 5 As shown, the gas sensor includes multiple sets of microelectromechanical ultrasonic transducers according to the first to fourth preferred embodiments. These multiple sets of microelectromechanical ultrasonic transducers can preferably be arranged in an array; for example, an array can be used as described above. Figure 5 The 3x3 microelectromechanical ultrasonic transducer array shown shares the same electrical carrier plate. The diaphragm of each microelectromechanical ultrasonic transducer in the array adopts a cross-shaped diaphragm structure. Several electrode contacts P110 and P310 are distributed around the microelectromechanical ultrasonic transducer array.

[0098] Preferably, the gas sensor of the present invention, composed of a microelectromechanical ultrasonic transducer array, comprises multiple sets of microelectromechanical ultrasonic transducers. Each set of microelectromechanical ultrasonic transducers includes a hole on an electrical carrier plate, and a receiving transducer and a transmitting transducer disposed above and below the hole. The diaphragm of the microelectromechanical ultrasonic transducer in the gas sensor is not limited to a slit-type multi-diaphragm design; other structures are also possible, which will not be elaborated here.

[0099] Preferably, the gas sensor of the present invention, composed of a microelectromechanical ultrasonic transducer array, includes multiple sets of microelectromechanical ultrasonic transducers and enclosed microelectromechanical ultrasonic transducers, which form an array. Each set of microelectromechanical ultrasonic transducers and enclosed microelectromechanical ultrasonic transducers is preferably as follows: Figure 3A and Figure 3B The structure is shown in the diagram, and will not be elaborated upon here.

[0100] The working principle of the gas sensor based on the microelectromechanical ultrasonic transducer of this invention is shown in Figures 6(a) and 6(b). The receiving transducer 100 and the transmitting transducer 200 are stacked vertically on the surface of the hole QC100 of the electrical carrier plate Q100, forming a gas containment space with the inner wall of the hole QC100. The containment space contains background gas, such as air, as shown in Figure 6(a). The first sound wave WA100 emitted by the transmitting transducer 200 propagates to the receiving transducer 100 through the background gas. As shown in Figure 6(b), the test gas FX100 is mixed into the background gas between the transmitting transducer 200 and the receiving transducer 100, forming a sample distribution GX100 of the test gas. The second acoustic wave WA200 emitted by the transmitting transducer 200 propagates through the background gas of the sample distribution GX100 of the gas being measured to the receiving transducer 100. Since the molar mass of the sample distribution GX100 of the gas being measured is different from that of the background gas, the propagation speed of the second acoustic wave WA200 is different from that of the first acoustic wave WA100. By performing relevant calculations based on this difference, such as time-of-flight calculations or phase calculations, the concentration and / or species of the gas being measured FX100 can be obtained.

[0101] This invention relates to a gas sensor based on a microelectromechanical ultrasonic transducer. The microelectromechanical ultrasonic transducer is electrically connected to the surface of an electrical carrier plate. The receiving and transmitting transducers are positioned opposite each other in the vertical direction on the surface of the electrical carrier plate, with the diaphragms of the receiving and transmitting transducers parallel to the surface of the electrical carrier plate. Compared to traditional ultrasonic gas sensors, this invention, combined with semiconductor packaging technology, not only has advantages such as small size and high integration, but also improves sensor consistency, making it suitable for mass production.

[0102] The above description illustrates preferred embodiments of the present invention and helps those skilled in the art to more fully understand the technical solution of the present invention. However, these embodiments are merely illustrative and should not be construed as limiting the specific implementation of the present invention to these embodiments. For those skilled in the art, several simple deductions and modifications can be made without departing from the inventive concept, and all such modifications should be considered within the protection scope of the present invention.

Claims

1. A gas sensor based on a microelectromechanical ultrasonic transducer, comprising an electrical carrier plate, characterized in that, The electrical carrier plate has holes; a microelectromechanical ultrasonic transducer electrically connected to the electrical carrier plate is disposed thereon, the microelectromechanical ultrasonic transducer includes a receiving transducer disposed above the holes and a transmitting transducer disposed below the holes.

2. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 1, characterized in that, The transmitting transducer includes a second substrate with a back cavity and a second diaphragm covering the back cavity; the receiving transducer includes a first substrate with a back cavity and a first diaphragm covering the back cavity; the second diaphragm of the transmitting transducer and the first diaphragm of the receiving transducer are arranged opposite to each other in the horizontal direction on the surface of the electrical carrier plate.

3. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 2, characterized in that, The second diaphragm of the transmitting transducer and the first diaphragm of the receiving transducer are symmetrically arranged in the horizontal direction with respect to the surface of the electrical carrier plate.

4. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 1, characterized in that, The electrical carrier is a substrate or a printed circuit board.

5. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 1, characterized in that, The transmitter and receiver transducers of the microelectromechanical ultrasonic transducer are electrically connected to and fixed on the electrical carrier plate via solder balls.

6. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 5, characterized in that, Due to the support of the solder balls, there are gaps for gas to enter between the second substrate of the transmitting transducer and the electrical carrier plate, and between the first substrate of the receiving transducer and the electrical carrier plate.

7. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 1, characterized in that, The receiving transducer and the transmitting transducer are electrically connected to the electrical carrier board via a flip-chip packaging method.

8. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 1, characterized in that, The electrical carrier board is also provided with an arithmetic and / or power supply circuit module and a temperature sensor. The arithmetic and / or power supply circuit module and the temperature sensor are electrically connected to the electrical carrier board and fixed on the electrical carrier board through solder balls.

9. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 1, characterized in that, The electrical carrier plate has multiple conductor structures inside, which are used to connect the microelectromechanical ultrasonic transducer and other electrical or sensor modules.

10. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 1, characterized in that, The horizontal dimension of the gas sensor is less than 3 cm; or the horizontal dimension of the gas sensor is less than 1 cm; or the horizontal dimension of the gas sensor is less than 0.5 cm.

11. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 1, characterized in that, The distance between the transmitting transducer and the receiving transducer is less than 1 cm; or the distance between the transmitting transducer and the receiving transducer is less than 5 mm; or the distance between the transmitting transducer and the receiving transducer is less than 2 mm.

12. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 1, characterized in that, The electrical carrier is a three-layer substrate, comprising a first substrate, a second substrate, and a third substrate from bottom to top; the first substrate and the third substrate are covered by a second substrate with a cavity on the top and bottom, and mounting holes are provided on the first substrate and the third substrate, the mounting holes and the cavity communicating to form holes on the electrical carrier.

13. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 12, characterized in that, The first substrate, the second substrate, and the third substrate are electrically connected and fixed together using solder balls.

14. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 12, characterized in that, The second substrate of the transmitting transducer is fixed to the inner wall of the third substrate facing the cavity, and the first substrate of the receiving transducer is fixed to the inner wall of the first substrate facing the cavity.

15. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 2, characterized in that, The electrical carrier plate also has another hole and two enclosed microelectromechanical ultrasonic transducers; the two enclosed microelectromechanical ultrasonic transducers are a transmitter transducer and a receiver transducer disposed above and below the other hole; one of the enclosed microelectromechanical ultrasonic transducers has a receiver dry film disposed outside the receiver transducer, and the other enclosed microelectromechanical ultrasonic transducer has a transmitter dry film disposed outside the transmitter transducer; the receiver dry film and the transmitter dry film are used to seal the background gas between the receiver transducer and the transmitter transducer.

16. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 2, characterized in that, The first diaphragm of the receiving transducer and the second diaphragm of the transmitting transducer are diaphragms with slits.

17. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 16, characterized in that, A small amount of gas enters the gas-containing space formed by the holes through the gaps in the slits of the first diaphragm of the receiving transducer and the slits in the second diaphragm of the transmitting transducer.

18. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 16, characterized in that, The slit divides the second diaphragm of the transmitting transducer or the first diaphragm of the receiving transducer into multiple regions.

19. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 16, characterized in that, The diaphragm of the slit is a double sandwich diaphragm, comprising a first sandwich diaphragm and a second sandwich diaphragm; the first sandwich diaphragm comprises, from bottom to top, a first bottom electrode layer, a first piezoelectric layer and a first top electrode layer; the second sandwich diaphragm comprises, from bottom to top, a second bottom electrode layer, a second piezoelectric layer and a second top electrode layer; a seed layer exists between the first sandwich diaphragm and the second sandwich diaphragm.

20. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 16, characterized in that, The materials of the first piezoelectric layer and the second piezoelectric layer are aluminum nitride, doped aluminum nitride, lead zirconate titanate, and doped lead zirconate titanate; the electrode materials of the first bottom electrode layer, the first top electrode layer, the second bottom electrode layer, and the second top electrode layer are molybdenum, platinum, and gold.

21. The gas sensor based on a microelectromechanical ultrasonic transducer according to claim 1, characterized in that, Multiple sets of microelectromechanical ultrasonic transducers are arranged on the electrical carrier plate, and the multiple sets of microelectromechanical ultrasonic transducers form an array.

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