A pressure sensor sensitive structure

Abstract

The present application relates to the field of force measurement technology, and provides a pressure sensor sensitive structure, including a pressure-sensitive layer, a vibration beam layer, a stress isolation layer and a base layer, wherein the pressure-sensitive layer includes a pressure-sensitive film; the vibration beam layer includes a vibration beam base and a vibration beam structure, wherein the vibration beam base is connected to the pressure-sensitive film, and the vibration beam structure is connected to the vibration beam base; the stress isolation layer includes a stress isolation ring structure, wherein the stress isolation ring structure is connected to the side of the vibration beam base away from the pressure-sensitive film, wherein the stress isolation ring structure is hollow inside to form a through hole, and the vibration beam base covers the first end of the through hole; the base layer includes a quartz base sheet, wherein the quartz base sheet is connected to the stress isolation layer, and the quartz base sheet covers the second end of the through hole. By arranging a stress isolation ring structure between the base layer and the vibration beam layer, the influence of external stress on the vibration beam layer can be isolated, the stability and precision of the vibration beam structure can be protected, the assembly stress, thermal stress and vibration impact stress from the package can be effectively weakened, and the stability of the zero bias of the entire table can be improved.

Description

Technical Field

[0001] The present application relates to the field of force measurement technology, and in particular to a sensitive structure of a pressure sensor. Background Art

[0002] As a high-precision and high-stability pressure measurement device, quartz resonant pressure sensor is widely used in industrial production, scientific research and other fields. Its sensitive structure, as the core part of the sensor, plays a decisive role in the performance of the sensor. At present, the sensitive structure of quartz resonant pressure sensor mainly includes all-quartz sensitive structure, metal Bourdon tube + quartz vibration beam structure and other types. These structures have their own characteristics in design, but they also expose some problems in practical applications:

[0003] 1. The existing products use a metal Bourdon tube + quartz vibration beam structure bonding solution. Due to the use of multiple materials, the thermal expansion coefficients of the materials themselves cannot be completely matched, and the use of process adhesive bonding cannot effectively guarantee the matching of the thermal expansion coefficients, resulting in a relatively large temperature drift coefficient when the temperature changes within the full temperature range;

[0004] 2. The existing sensitive structure adopts a chip-level micro-assembly solution. The pressure-sensitive film, vibration beam layer and substrate layer need to be assembled with high precision. The process is complex and the efficiency is low, which affects the production capacity. The core vibration beam electrode cannot be led out separately. It is necessary to use gold wire bonding to lead out the wire. Chip-level micro-assembly is required. The process is difficult and inefficient. The gold wire is anchored to the pressure-sensitive film through the vibration beam structure layer. The thermal deformation of the gold wire itself will affect the pressure-sensitive film, thereby causing the vibration beam frequency to drift.

[0005] 3. The pressure-sensitive membranes of existing sensitive structures are all over-positioned structures, which cannot effectively isolate assembly stress and thermal stress, causing the pressure-sensitive membrane itself to be easily deformed. The contact process between the pressure-sensitive membrane and the external fluid will cause the uniformity of the pressure-sensitive temperature to change. The temperature gradient of the pressure-sensitive membrane itself will also cause vibration beam drift;

[0006] 4. The existing structure cannot maintain high vacuum for a long time. It relies on the initial vacuum of product assembly to maintain product performance. It cannot maintain high vacuum for a long time. Due to leakage in the product package itself, product performance deteriorates. Summary of the invention

[0007] The present application aims to solve at least one of the technical problems existing in the related art. To this end, the present application proposes a pressure sensor sensitive structure.

[0008] The pressure sensor sensitive structure proposed in the embodiment of the first aspect of the present application includes:

[0009] A pressure-sensitive layer, including a pressure-sensitive film;

[0010] A vibration beam layer, comprising a vibration beam base and a vibration beam structure, wherein the vibration beam base is connected to the pressure-sensitive film, and the vibration beam structure is connected to the vibration beam base;

[0011] The stress isolation layer comprises a stress isolation ring structure, wherein the stress isolation ring structure is connected to a side of the vibration beam base away from the pressure-sensitive film, the stress isolation ring structure is hollow inside to form a through hole, and the vibration beam base covers a first end of the through hole;

[0012] The base layer comprises a quartz base plate, wherein the quartz base plate is connected to the stress isolation layer and covers the second end of the through hole.

[0013] According to the sensitive structure of the pressure sensor in the embodiment of the present application, a stress isolation ring structure is set between the base layer and the vibration beam layer to isolate the influence of external stress on the vibration beam layer, thereby protecting the stability and accuracy of the vibration beam structure, effectively weakening the assembly stress, thermal stress and vibration impact stress from the package, and improving the stability of the zero bias of the entire meter.

[0014] According to an embodiment of the present application, the stress isolation ring structure connects the vibration beam layer and the base layer through a bonding glass paste ring.

[0015] According to one embodiment of the present application, the base layer includes a quartz base sheet and a coated getter layer, the coated getter layer is connected to the quartz base sheet, the quartz base sheet is connected to the stress isolation ring structure, and the coated getter layer is arranged on the side of the quartz base sheet close to the stress isolation ring structure.

[0016] According to an embodiment of the present application, the pressure-sensitive film is provided with a first concave cavity, a second concave cavity and a convex platform, the first concave cavity is provided on the first side of the pressure-sensitive film, the second concave cavity is provided on the second side of the pressure-sensitive film, the first side of the pressure-sensitive film and the second side of the pressure-sensitive film are opposite to each other, and the convex platform is provided in the first concave cavity;

[0017] At least one anchoring area of ​​the vibration beam structure is fixedly connected to the boss.

[0018] According to one embodiment of the present application, the vibration beam structure includes a pressure measuring vibration beam, a reference vibration beam and a matching vibration beam, the anchor area of ​​the pressure measuring vibration beam is fixedly connected to the boss, the anchor area of ​​the reference vibration beam is fixedly connected to the vibration beam base, the matching vibration beam and the reference vibration beam are symmetrically arranged on the vibration beam base with respect to the pressure measuring vibration beam, and the anchor area of ​​the matching vibration beam is fixedly connected to the vibration beam base.

[0019] According to an embodiment of the present application, the pressure measuring vibration beam, the reference vibration beam and the matching vibration beam have the same size.

[0020] According to an embodiment of the present application, the anchor area of ​​the pressure measuring vibration beam is fixedly connected to the boss by an adhesive material, and the adhesive material is one of glass paste, metal solder, epoxy glue and gold-gold bonding material.

[0021] According to one embodiment of the present application, the vibration beam structure includes an anchor area, a connecting beam, a node, and a tuning fork vibration beam, the anchor area is connected to the connecting beam, the connecting beam is connected to the node, and the node is connected to the tuning fork vibration beam.

[0022] According to an embodiment of the present application, the pressure-sensitive film is a quartz crystal pressure-sensitive film, the vibration beam structure is a quartz crystal vibration beam structure, the stress isolation ring structure is a quartz isolation ring structure, and the base layer is a quartz crystal base layer.

[0023] The advantages of the pressure sensor sensitive structure of the present application are as follows:

[0024] (1) Low-temperature glass paste sealing design and thin-film getter vacuum packaging design based on thermal expansion coefficient matching. The use of low-temperature glass paste sealing that matches the thermal expansion coefficient of quartz crystal improves the bonding strength, air tightness, and electrical insulation of components. Wafer-level alignment sintering is used to improve packaging efficiency. Visual alignment assembly of vibration beams is used to improve assembly accuracy. Thin-film getters are used to improve the reliability of wafer-level vacuum packaging.

[0025] (2) The three tuning fork beams are designed in an integrated package with good process consistency. The reference beam is used to suppress the temperature drift of the pressure measuring beam. The matching tuning fork beam is designed to improve the symmetry of the sensitive structure, thereby suppressing the mechanical common mode error. The reference beam leads to the electrode through a folded beam with extremely low stiffness, realizing lead-free connection inside the sensitive structure.

[0026] (3) Based on the low-temperature drift and high-sensitivity pressure-sensitive film packaging design with folded beams and bosses, grooves are dug on the front and back sides of the quartz plate to achieve internal and external stress isolation mechanisms, effectively reducing the effects of packaging stress, thermal stress and vibration shock on the stress of the pressure-sensitive film, and effectively reducing the zero drift of the sensitive structure vibration beam; by designing the boss, the strain of the pressure-sensitive film caused by the increase in pressure is multiplied by the relative displacement of the two bosses, thereby improving the sensitivity of the pressure-sensitive film.

[0027] (4) Design of stress isolation structure of pressure-sensitive membrane package with concave cavity structure. Compared with the pressure-sensitive membrane design with flat membrane structure, the concave cavity pressure-sensitive membrane can transform the pressure deformation input from the outside from tensile and compressive deformation into bending deformation, thereby improving the sensitivity of the pressure-sensitive membrane. Through the bending deformation with lower stiffness, the assembly stress and thermal stress can be transformed into the deformation of the concave cavity folded beam, thus ensuring the zero-bias stability of the vibration beam.

[0028] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present application or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 It is a cross-sectional view of the assembly of the sensitive structure of the pressure sensor provided in the embodiment of the present application.

[0031] Figure 2 It is an assembly top view of the pressure sensor sensitive structure provided by an embodiment of the present application without the pressure-sensitive layer.

[0032] Figure 3 Schematic diagram of the structure of the pressure-sensitive film provided in the embodiment of the present application.

[0033] Figure 4 It is a schematic diagram of the structure of the stress isolation layer provided in an embodiment of the present application.

[0034] Figure 5 It is a structural schematic diagram of a screen-printed wafer with a CCD alignment mark provided in an embodiment of the present application.

[0035] Figure 6 It is a schematic diagram of the screen printing alignment mark dimensions provided in an embodiment of the present application.

[0036] Figure 7 It is a schematic diagram of the wafer-level alignment mark dimensions provided in an embodiment of the present application.

[0037] Figure 8 It is a schematic diagram of the slurry unit ring size provided in the embodiment of the present application.

[0038] Fig. 9 It is a schematic diagram of the structure of screen printing of pressure-sensitive layer glass paste provided in an embodiment of the present application.

[0039] Fig.10 It is a structural schematic diagram of double-sided screen printing of stress isolation layer glass paste provided in an embodiment of the present application.

[0040] Fig.11 It is a schematic diagram of the structure of wafer-level bonding of a pressure-sensitive layer and a vibration beam layer provided in an embodiment of the present application.

[0041] Fig.12It is a schematic diagram of the structure of wafer-level bonding of a stress isolation layer, a vibration-sensing assembly sheet and a base layer provided in an embodiment of the present application.

[0042] Fig.13 It is a schematic diagram of the steps of the packaging method of the pressure sensor sensitive structure provided in an embodiment of the present application.

[0043] Reference numerals:

[0044] 100, pressure-sensitive layer; 110, pressure-sensitive film; 111, first concave cavity; 112, second concave cavity; 113, boss; 114, overflow groove;

[0045] 200, vibration beam layer; 210, vibration beam base; 220, vibration beam structure; 221, pressure measuring vibration beam; 222, reference vibration beam; 223, matching vibration beam; 224, first excitation electrode; 225, second excitation electrode; 226, anchor area; 227, connecting beam; 228, wave node; 229, tuning fork vibration beam; 230, folding beam;

[0046] 300, stress isolation layer; 310, stress isolation ring structure; 311, through hole;

[0047] 400, substrate layer; 410, quartz substrate; 420, coating getter layer; DETAILED DESCRIPTION

[0048] The following is a further detailed description of the implementation of the present application in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present application but cannot be used to limit the scope of the present application.

[0049] In the description of the embodiments of the present application, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the embodiments of the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0050] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection, wherein the fixed connection can include an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0051] In the embodiments of the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0052] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiments of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0053] Combine the following Figures 1 to 13 The sensitive structure of the pressure sensor of the present application is described.

[0054] According to the pressure sensor sensitive structure proposed in the embodiment of the present application (hereinafter referred to as the sensitive structure), please refer to Figures 1 to 4The sensitive structure includes a pressure-sensitive layer 100, a vibration beam layer 200, a stress isolation layer 300 and a base layer 400. The pressure-sensitive layer 100 includes a pressure-sensitive film 110; the vibration beam layer 200 includes a vibration beam base 210 and a vibration beam structure 220, wherein the vibration beam base 210 is connected to the pressure-sensitive film 110, and the vibration beam structure 220 is connected to the vibration beam base 210; the stress isolation layer 300 includes a stress isolation ring structure 310, wherein the stress isolation ring structure 310 is connected to the side of the vibration beam base 210 away from the pressure-sensitive film 110, wherein the stress isolation ring structure 310 is hollow inside to form a through hole 311, and the vibration beam base 210 covers the first end of the through hole 311; the base layer 400 includes a quartz base plate 410, wherein the quartz base plate 410 is connected to the stress isolation layer 300, and the quartz base plate 410 covers the second end of the through hole 311.

[0055] According to the sensitive structure of the pressure sensor of the embodiment of the present application, by setting a stress isolation ring structure 310 between the base layer 400 and the vibration beam layer 200, the influence of external stress on the vibration beam layer 200 can be isolated, the stability and accuracy of the vibration beam structure 220 can be protected, and the assembly stress, thermal stress and vibration impact stress from the package can be effectively weakened, thereby improving the stability of the zero bias of the entire meter.

[0056] According to an embodiment of the present application, the sensitive structure includes a pressure-sensing layer 100 , a vibration beam layer 200 , a stress isolation layer 300 and a base layer 400 . The pressure-sensitive layer 100 includes a pressure-sensitive film 110, and the pressure-sensitive film 110 is provided with a first cavity 111, a second cavity 112 and a boss 113. The first cavity 111 is provided on a first side of the pressure-sensitive film 110, and the second cavity 112 is provided on a second side of the pressure-sensitive film 110. The first side of the pressure-sensitive film 110 and the second side of the pressure-sensitive film 110 are opposite to each other, and the boss 113 is provided in the first cavity 111; the vibration beam layer 200 includes a vibration beam base 210 and a vibration beam structure 220. The vibration beam base 210 is connected to the first side of the pressure-sensitive film 110, and the vibration beam structure 220 is connected to the vibration beam base 210. An anchor area 226 of at least one vibration beam structure 220 is fixedly connected to the boss 113; the stress isolation layer 300 is connected to a side of the vibration beam layer 200 away from the pressure-sensitive layer 100; and the base layer 400 is connected to a side of the stress isolation layer 300 away from the vibration beam layer 200.

[0057] According to the sensitive structure of the pressure sensor in the embodiment of the present application, a folded structure is formed by the first cavity 111 and the second cavity 112 of the pressure-sensitive film 110, which can transform the pressure-sensitive deformation of the pressure-sensitive film 110 from traditional tensile and compressive deformation into bending deformation, thereby improving the sensitivity of the pressure-sensitive film 110, and can also effectively absorb assembly stress and thermal stress. The boss 113 can amplify the deformation of the pressure-sensitive film 110, thereby improving the sensitivity.

[0058] It is understandable that the pressure-sensitive film 110 is designed with a first cavity 111, a second cavity 112 and a boss 113. The boss 113 is arranged in the first cavity 111, and the two together constitute a stress isolation groove structure. During the assembly process, due to the existence of assembly stress, the over-positioned pressure-sensitive film 110 may be twisted and deformed, and the pressure-sensitive film 110 with the first cavity 111 can effectively absorb the assembly stress; when the sensitive structure is tested at high and low temperatures, the thermal stress will cause the pressure-sensitive film 110 to be twisted and deformed, and the first cavity 111 can effectively absorb the thermal stress; fourth, the boss 113 can amplify the deformation of the pressure-sensitive film 110, thereby improving the resistance to temperature change and overload. In one embodiment, the pressure-sensitive film 110 is fixedly connected to the vibration beam base 210 by glass slurry.

[0059] The vibration beam base 210 is connected to the portion of the pressure-sensitive layer 100 provided with the first side of the pressure-sensitive film 110, and plays the role of supporting and fixing the vibration beam structure 220. The vibration beam structure 220 is connected to the vibration beam base 210, and at least one anchor area 226 thereof is fixedly connected to the boss 113. The vibration beam structure 220 will vibrate when affected by the deformation of the pressure-sensitive film 110, and its vibration frequency is related to the pressure.

[0060] The stress isolation layer 300 is connected to the side of the vibration beam layer 200 away from the pressure-sensing layer 100, and its main function is to isolate the influence of external stress on the vibration beam layer 200 and protect the stability and accuracy of the vibration beam structure 220. It can be understood that the stress isolation layer 300 can effectively weaken the assembly stress, thermal stress and vibration impact stress from the package, and improve the stability of the zero bias of the whole table.

[0061] The base layer 400 is connected to the side of the stress isolation layer 300 facing away from the vibration beam layer 200 to provide support and stability for the entire sensitive structure.

[0062] According to an embodiment of the present application, the first cavity 111 and the second cavity 112 are staggered. It can be understood that the first cavity 111 is located on one side of the pressure-sensitive film 110, and the second cavity 112 is located on the opposite side of the pressure-sensitive film 110. The first cavity 111 and the second cavity 112 are staggered to form a folded structure of bending deformation, thereby enhancing the deformation effect of the pressure-sensitive film 110.

[0063] According to an embodiment of the present application, the first cavity 111 and the second cavity 112 have the same depth. It is understandable that the first cavity 111 and the second cavity 112 have the same depth, and this design helps to maintain uniform deformation of the pressure-sensitive film 110 when subjected to force, thereby improving measurement accuracy.

[0064] According to an embodiment of the present application, the pressure-sensitive film 110 is fixedly connected to the vibration beam base 210 through glass slurry, and the pressure-sensitive film 110 is provided with an overflow groove 114, and the overflow groove 114 is arranged beside the glass slurry. It can be understood that the overflow groove 114 is arranged beside the glass slurry, which can provide a channel for excess slurry to flow out during the curing process of the glass slurry, so as to avoid the overflow of slurry affecting the stability and accuracy of the structure. At the same time, the overflow groove 114 can also alleviate the thermal stress caused by temperature changes to a certain extent, thereby improving the reliability of the sensor.

[0065] According to an embodiment of the present application, the depth of the first cavity 111 is the same as the height of the boss 113. It can be understood that the first cavity 111 and the boss 113 cooperate to form a stress isolation groove structure, wherein the depth of the first cavity 111 and the height of the boss 113 are the same to ensure that the boss 113 does not protrude too much from the pressure-sensitive layer 100 to the vibration beam layer 200.

[0066] According to one embodiment of the present application, the vibration beam structure 220 includes a pressure measuring vibration beam 221, a reference vibration beam 222 and a matching vibration beam 223. The anchor area 226 of the pressure measuring vibration beam 221 is fixedly connected to the boss 113, the anchor area 226 of the reference vibration beam 222 is fixedly connected to the vibration beam base 210, the matching vibration beam 223 and the reference vibration beam 222 are symmetrically arranged on the vibration beam base 210 with respect to the pressure measuring vibration beam 221, and the anchor area 226 of the matching vibration beam 223 is fixedly connected to the vibration beam base 210.

[0067] The vibration beam layer 200 includes a vibration beam base 210 and a plurality of vibration beam structures 220, and the anchoring area 226 of the pressure measuring vibration beam 221 is fixedly connected to the boss 113. Since the boss 113 can amplify the deformation of the pressure sensing film 110, the pressure measuring vibration beam 221 can more accurately sense the change in pressure and convert it into an electrical signal for output. The anchoring area 226 of the reference vibration beam 222 is fixedly connected to the vibration beam base 210. The reference vibration beam 222 is used as a reference for comparison with the output signal of the pressure measuring vibration beam 221, thereby eliminating common mode errors and improving the accuracy of the measurement. The matching vibration beam 223 makes the entire vibration beam layer 200 more symmetrical and stable in structure, which helps to reduce the influence of external interference on the measurement results. In addition, the matching vibration beam 223 can also be used as an additional reference vibration beam to further improve the accuracy and reliability of the measurement.

[0068] According to one embodiment of the present application, the pressure measuring vibration beam 221, the reference vibration beam 222 and the matching vibration beam 223 have the same size. It is understandable that the same size of the vibration beam structure 220 helps to reduce the thermal stress and mechanical stress caused by the size difference, thereby improving the stability and reliability of the sensor. The pressure measuring vibration beam 221, the reference vibration beam 222 and the matching vibration beam 223 with the same size are integrated into one process, and the process consistency of the pressure measuring vibration beam 221 and the reference vibration beam 222 is utilized to suppress the common mode error of the pressure sensing vibration beam, thereby reducing and improving the temperature drift coefficient of the sensitive structure as a whole, and effectively isolating the influence of external thermal stress on the tuning fork vibration beam 229, thereby solving the stress isolation problem under high sensitivity conditions. The integrated temperature measuring diode bare DIE can accurately reflect the core temperature of the vibration beam and improve the temperature compensation effect.

[0069] According to one embodiment of the present application, the vibration beam structure 220 includes an anchor area 226, a connecting beam 227, a node 228, and a tuning fork vibration beam 229, wherein the anchor area 226 is connected to the connecting beam 227, the connecting beam 227 is connected to the node 228, and the node 228 is connected to the tuning fork vibration beam 229.

[0070] It is understandable that the vibration beam structure 220 is responsible for converting the mechanical deformation sensed by the pressure-sensitive layer 100 into an electrical signal for output. The anchor area 226 of the vibration beam structure 220 of this embodiment is connected to the connecting beam 227, providing a stable support point for the connecting beam 227. The connecting beam 227 is the connecting part between the anchor area 226 and the node 228. It is responsible for transferring the fixing effect of the anchor area 226 to the node 228 while maintaining the integrity and stability of the structure. The node 228 is located between the connecting beam 227 and the tuning fork vibration beam 229. The design of the node 228 enables the vibration beam to form a specific vibration mode when vibrating, thereby improving the accuracy and stability of the measurement. The tuning fork vibration beam 229 is the vibration part in the vibration beam structure 220, which is responsible for converting the mechanical deformation sensed by the pressure-sensitive layer 100 into an electrical signal for output. In this embodiment, the tuning fork vibration beam 229 is connected to the wave node 228, and the external force is transmitted to the tuning fork vibration beam 229 through the vibration of the wave node 228, thereby realizing the output of the vibration signal.

[0071] According to an embodiment of the present application, the two first excitation electrodes 224 of the reference vibration beam 222 are led out by routing on the vibration beam base 210. In this embodiment, the two first excitation electrodes 224 of the reference vibration beam 222 are led out by routing on the vibration beam base 210. This design not only simplifies the electrode lead-out process, but also reduces the manufacturing cost. At the same time, since the first excitation electrodes 224 are directly connected to the vibration beam base 210, they can more accurately reflect the real state of the vibration beam, thereby improving the accuracy of the measurement.

[0072] According to an embodiment of the present application, the vibration beam layer 200 includes a folded beam 230, and the second excitation electrode 225 of the pressure measuring vibration beam is electrically led out through the folded beam 230. The folded beam 230 achieves compactness and lightness of the vibration beam structure 220 by folding a part of the vibration beam. At the same time, the folded beam 230 also serves as an electrical lead-out path for the second excitation electrode 225 of the pressure measuring vibration beam. This design not only simplifies the electrode lead-out process, but also improves the overall rigidity and stability of the vibration beam structure 220.

[0073] According to an embodiment of the present application, the number of bosses 113 corresponds to the number of anchor areas 226 of the pressure measuring vibration beam 221 . The number of anchor areas 226 of the pressure measuring vibration beam 221 is two, and the anchor areas 226 of the two pressure measuring vibration beams 221 are arranged at intervals.

[0074] The number of bosses 113 is set corresponding to the number of anchoring areas 226 of the pressure measuring vibration beam 221. In this embodiment, the number of anchoring areas 226 of the pressure measuring vibration beam 221 is two, so the number of bosses 113 is also two. The two bosses 113 are arranged at intervals, providing a stable support point for the anchoring area 226 of the pressure measuring vibration beam 221. The anchoring areas 226 of the two pressure measuring vibration beams 221 are arranged at intervals, so that the pressure measuring vibration beam 221 can better sense the deformation of the pressure sensing film 110.

[0075] According to an embodiment of the present application, the stress isolation layer 300 includes a stress isolation ring structure 310 , and the stress isolation ring structure 310 is hollow and has a through hole 311 therein.

[0076] When the sensitive structure is bonded to the TO tube shell or LCC ceramic tube shell base, the thermal expansion coefficients of the tube shell material and the quartz material do not match, resulting in assembly stress. The stress isolation ring structure 310 can effectively isolate the assembly stress. The stress isolation ring structure 310 can be used to protect the vibration beam layer 200; adding a stress isolation layer 300 between the base layer 400 and the vibration beam layer 200 can provide a second level of "blocking" of the thermal stress of the external tube shell.

[0077] The through hole 311 can reduce the thermal expansion coefficient of the stress isolation ring structure 310 , making its dimensional changes at different temperatures more stable.

[0078] According to an embodiment of the present application, the stress isolation ring structure 310 connects the vibration beam layer 200 and the base layer 400 through a bonding glass paste ring.

[0079] According to an embodiment of the present application, the pressure-sensitive film 110 is a quartz crystal pressure-sensitive film 110 , the vibration beam structure 220 is a quartz crystal vibration beam structure 220 , the stress isolation ring structure 310 is a quartz isolation ring structure, and the base layer 400 is a quartz crystal base layer 400 .

[0080] According to an embodiment of the present application, the anchor region 226 of the pressure measuring vibration beam 221 is fixedly connected to the boss 113 by an adhesive material, and the adhesive material is one of glass paste, metal solder, epoxy glue and gold-gold bonding material.

[0081] According to an embodiment of the present application, the base layer 400 includes a quartz base plate 410 and a film-coated getter layer 420, the film-coated getter layer 420 is connected to the quartz base plate 410, the quartz base plate 410 is connected to the stress isolation ring structure 310, and the film-coated getter layer 420 is arranged on the side of the quartz base plate 410 close to the stress isolation ring structure 310. The film-coated getter layer 420 is provided with a getter, and the getter can absorb the surrounding gas when activated.

[0082] It is understandable that a coated getter layer 420 is provided at the bottom of the through hole 311 of the stress isolation ring structure 310, and the coated getter layer 420 is activated at the same time at the hot pressing bonding temperature to achieve long-term maintenance of high vacuum and ensure that the quartz resonator has a higher quality factor.

[0083] In one embodiment, the sensitive structure adopts a full quartz sensitive structure solution; the pressure-sensitive film 110, the vibration beam structure 220, the stress isolation ring and the base layer 400 are all made of quartz crystal materials, which improves the matching of the thermal expansion coefficient of the material, solves the temperature drift problem caused by the mismatch of the thermal expansion coefficient of the material, and replaces the traditional single-part processing method.

[0084] The sensitive structure of the pressure sensor of the present application is described below in conjunction with an embodiment.

[0085] The entire sensitive structure consists of four layers: pressure-sensitive layer, vibration beam layer, stress isolation layer and base layer.

[0086] The pressure-sensitive layer adopts a z-cut 3-inch quartz wafer with a thickness of 220um~1920um. The pressure-sensitive film includes a first cavity, a second cavity, a boss and an overflow groove. Since the top and bottom layers of the pressure-sensitive film are simultaneously sandblasted, wet-etched or laser-processed, the angle between the side edge of the structure and the wafer ranges from thet1:45 degrees to 75 degrees, so that the depth of the bottom cavity layer and the height of the top boss layer are equal. The thickness of the pressure-sensitive film determines the range of the sensitive structure. The designed thickness is 108um~500um, and the range is 100kPa~50.1MPa; the height of the quartz boss is 50um. The quartz boss here plays the role of amplifying the strain of the pressure-sensitive film, thereby improving the pressure sensitivity of the pressure-sensitive film. The back cavity and the front cavity form a folded pressure-sensitive film structure. The packaging structural parameters of the sensitive structure are shown in Table 1.

[0087] The vibration beam layer uses a z-cut 3-inch quartz wafer, including three types: pressure measuring vibration beam, reference vibration beam and matching vibration beam. The basic dimensions of the three vibration beams are exactly the same, and the entire structure is axially symmetrical. Each quartz vibration beam structure consists of four parts: anchor area, connecting beam, wave node, and tuning fork vibration beam; the anchor area E and anchor area F of the pressure measuring vibration beam are rigidly connected to the upper surface of the boss of the folded pressure-sensitive membrane through glass slurry to sense the pressure changes input from the outside; the reference vibration beam anchor areas A and B are rigidly connected to the vibration beam base, and have the same temperature characteristics as the pressure measuring vibration beam without sensing the external input pressure. The frequencies of the two vibration beams are subtracted, and the common mode suppression function is realized through the frequency difference output; the matching vibration beam mainly realizes the symmetry of the vibration beam layer structure, and its anchor area C and anchor area D are rigidly connected to the vibration beam base;

[0088] The stress isolation layer adopts a z-cut 3-inch quartz wafer, including a stress isolation ring structure and a double-sided bonded glass slurry ring. The width of the bonding slurry ring is 0.5 mm. The concave cavity ring is processed by double-sided sandblasting, double-sided laser grooving or double-sided wet etching. The angle between the edge of the processed structure and the wafer plane is thet2, and the value range is: 45 degrees to 75 degrees.

[0089] The substrate layer uses a z-cut 3-inch quartz wafer, including a quartz substrate and a coated getter layer. A hard shielding plate process is used and magnetron sputtering technology is used to sputter non-evaporable metal film getter at the bottom of the cavity. The main component of the target material is titanium-zirconium alloy.

[0090] When the input pressure of the pressure-sensitive film in the normal direction increases, the strain of the pressure-sensitive film causes the relative position of the two quartz islands on the pressure-sensitive film to increase, and the axial tensile stress of the pressure-sensitive vibration beam anchored to it increases, causing the resonance frequency of the tuning fork to increase. When the input pressure of the pressure-sensitive film in the normal direction decreases, the strain of the pressure-sensitive film causes the relative position of the two quartz islands on the pressure-sensitive film to decrease, and the axial tensile stress of the pressure-sensitive vibration beam anchored to it decreases, causing the resonance frequency of the tuning fork to decrease. The strain of the pressure-sensitive film causes the axial pressure of the tuning fork resonance, and the resonance frequency of the tuning fork resonance plane differential mode caused by the pressure-sensitive film is as follows:

[0091] (1)

[0092] here, To measure the axial tensile stress felt by the pressure vibration beam, is the eigenresonant frequency of the reference beam, is the Euler constant of the tuning fork beam, where and The expression is as follows:

[0093] (2)

[0094] (3)

[0095] here, is the elastic modulus of the quartz beam, is the density of quartz, , and is the length, width and thickness of a single beam of the tuning fork vibration beam. The recommended resonant frequency of the vibration beam is 115kHz~125kHz, and the recommended quality factor Q is 12000~19000; the vibration beam is an axisymmetric structure, symmetrical along the x-axis.

[0096] It should be noted that this solution uses quartz crystal material as an example, and single crystal silicon material, fused quartz material, functional ceramic material and metal material can also be used; the bonding material uses glass slurry, and can also use metal solder, matching epoxy glue or gold-gold bonding material, etc.

[0097] It should be noted that this solution is suitable for low, medium and high range pressure sensors, can measure gas, liquid and gas-liquid mixtures, and is used in pressure transmitters, level meters and flow meters. It can also be expanded to quartz inertial sensors (quartz gyroscopes and quartz accelerometers) and silicon micromechanical inertial sensors (silicon microaccelerometers and silicon microgyroscopes).

[0098] It is understandable that the use of an all-quartz solution to replace the traditional solution can effectively improve the consistency of the sensitive structure and facilitate mass production; the use of a base layer structure with an isolation ring can effectively weaken the assembly stress, thermal stress and vibration impact stress from the package, and improve the stability of the zero bias of the entire table; the use of a glass slurry wafer-level bonding process with a getter can reduce the stringent requirements of wafer-level direct bonding on the wafer surface morphology, improve the sealing strength and airtightness, and activate the getter at the same time as the wafer-level hot pressing bonding, which is conducive to maintaining a high vacuum for a long time. The use of an integrated processing solution for the reference vibration beam and the pressure-sensitive vibration beam can effectively suppress the common-mode error of the pressure-sensitive vibration beam and improve the stability of the entire table. The use of a grooved pressure-sensitive film structure can convert the tensile and compressive deformation of the pressure-sensitive film with a larger stiffness into a bending deformation with a smaller stiffness, which improves the sensitivity of the pressure-sensitive element while effectively absorbing the assembly stress and thermal stress, and improving the zero bias stability of the vibration beam.

[0099] Table 1 Sensitive structure packaging structure parameters (unit: um)

[0100]

[0101] Combine the following Figures 5 to 13 The packaging method of the pressure sensor sensitive structure of the present application includes step 100, step 200, step 300, step 400, step 500 and step 600.

[0102] Step 100, prepare a screen printing plate, the screen printing plate includes two pairs of screen printing marks, a pair of wafer-level alignment marks and 40 slurry units, the screen printing marks, the wafer-level alignment marks and the slurry units are distributed according to preset positions; wherein the preset positions refer to Figure 5 As shown, the dimensions are shown in Table 1.

[0103] The thickness of the photosensitive adhesive of the screen plate should be controlled between 35um and 50um (the precise value is 35um±1um), and the screen frame is made of cast aluminum with a specification of 320mm. 320mm. The screen is made of stainless steel wire mesh or nylon mesh, with a mesh size of 150 to 250. In addition, the viscosity of the high-temperature glass slurry needs to be maintained at 80-100 Pa.s, the mesh size is 250-300 mesh, and the sintering temperature is set at 400-450 degrees.

[0104] Step 200, screen printing of the pressure-sensitive layer wafer, including: processing screen printing marks and wafer-level alignment marks in advance on the wafer through high-precision laser marking, wet etching or dry etching, etc., covering a transparent film, forming a cross-shaped alignment mark on the wafer through screen printing, using two CCD electronic marks to clamp the wafer, after determining the position, putting the formal film into the suction cup to suck it, adjusting the workbench so that the cross mark on the wafer coincides with the electronic mark, and after the pressure-sensitive layer printing is completed, the wafer needs to be left on the platform for a first preset time to allow the slurry to level and form a pressure-sensitive film;

[0105] In the step of screen printing the pressure-sensitive layer wafer, the pressure-sensitive layer uses a 3-8 inch z-cut quartz crystal as the wafer, the thickness of the wafer is between 158um and 1800um, the first preset time is 3-5 minutes, the slurry printing width is 400um-500um, and the slurry layer thickness is 25-30um.

[0106] Step 300, screen printing of the stress isolation layer wafer, including: using high-precision laser marking, wet etching or dry etching and other processes on the wafer to process screen printing marks and wafer-level alignment marks in advance. Then, cover the transparent film, form a cross-shaped alignment mark on the wafer by screen printing, use two CCD electronic marks to clamp the wafer, and after determining the position, put the formal film into the suction cup and suck it, adjust the workbench so that the cross mark on the wafer coincides with the electronic mark, and after the stress isolation layer is printed, the wafer needs to stand on the platform for a second preset time to allow the slurry to level and air dry, and screen print the back of the stress isolation layer according to the same process to form a stress isolation ring structure;

[0107] In the step of screen printing the stress isolation layer wafer, the stress isolation layer uses 3~8 inch z-cut quartz crystal, the sheet thickness is between 1000um~2800um, the slurry printing width is 400um~500um, the slurry layer thickness is 25~30um, and the second preset time is 15~30 minutes.

[0108] Step 400, debinding and pre-firing, includes: placing the printed pressure-sensitive layer and stress isolation layer in a high-temperature oven, starting from room temperature, heating up to 150 degrees at a heating rate of 5 degrees / minute, keeping warm for 15 to 30 minutes, and discharging the organic solvent; heating up to 200 degrees, keeping warm for 30 minutes. Discharging the organic binder; heating up to 250 degrees, keeping warm for 15 to 30 minutes, activating the thixotropic agent of the slurry; heating up to 300 degrees, keeping warm for 15 to 30 minutes, achieving crystallization of the glass slurry; heating up to 350 degrees, keeping warm for 15 to 30 minutes, achieving melting and sintering of the glass slurry to form a ceramic glass substrate layer, and then cooling to room temperature with the furnace before taking out the wafer;

[0109] Step 500, wafer-level bonding of the pressure-sensitive layer and the vibration beam layer, including: using glass slurry to align and pre-fix the pressure-sensitive layer and the vibration beam layer at the wafer level, and performing wafer-level bonding under vacuum conditions to form a vibration-sensitive assembly sheet;

[0110] In the wafer-level bonding of the pressure-sensitive layer and the vibration beam layer, the bonding temperature is 400 degrees, the holding time is 15 minutes, the load is 500kg, and the bonding vacuum degree is 1E-3Pa.

[0111] Step 600, wafer-level bonding of the stress isolation layer, the vibration-sensing assembly sheet and the base layer, includes: aligning and pre-fixing the stress isolation layer, the vibration-sensing assembly sheet and the base layer at the three-layer wafer level, and performing wafer-level bonding of the three-layer under vacuum conditions.

[0112] In the step of wafer-level bonding of the stress isolation layer, the vibration-sensing assembly sheet and the base layer, the alignment accuracy needs to be controlled within ±10um. In one embodiment, the getter is activated, the bonding temperature is 390 degrees, the holding time is 15 minutes, the load is 500kg, and the bonding vacuum is 1E-3Pa.

[0113] The advantages of the packaging method of the present application are as follows:

[0114] (1) Low-temperature glass paste sealing design and thin-film getter vacuum packaging design based on thermal expansion coefficient matching. The use of low-temperature glass paste sealing that matches the thermal expansion coefficient of quartz crystal improves the bonding strength, air tightness, and electrical insulation of components. Wafer-level alignment sintering is used to improve packaging efficiency. Visual alignment assembly of vibration beams is used to improve assembly accuracy. Thin-film getters are used to improve the reliability of wafer-level vacuum packaging.

[0115] (2) The three tuning fork beams are designed in an integrated package with good process consistency. The reference beam is used to suppress the temperature drift of the pressure measuring beam. The matching tuning fork beam is designed to improve the symmetry of the sensitive structure, thereby suppressing the mechanical common mode error. The reference beam leads to the electrode through a folded beam with extremely low stiffness, realizing lead-free connection inside the sensitive structure.

[0116] (3) Based on the low-temperature drift and high-sensitivity pressure-sensitive film packaging design with folded beams and bosses, grooves are dug on the front and back sides of the quartz plate to achieve internal and external stress isolation mechanisms, effectively reducing the effects of packaging stress, thermal stress and vibration shock on the stress of the pressure-sensitive film, and effectively reducing the zero drift of the sensitive structure vibration beam; by designing the boss, the strain of the pressure-sensitive film caused by the increase in pressure is multiplied by the relative displacement of the two bosses, thereby improving the sensitivity of the pressure-sensitive film.

[0117] (4) Design of stress isolation structure of pressure-sensitive membrane package with concave cavity structure. Compared with the pressure-sensitive membrane design with flat membrane structure, the concave cavity pressure-sensitive membrane can transform the pressure deformation input from the outside from tensile and compressive deformation into bending deformation, thereby improving the sensitivity of the pressure-sensitive membrane. Through the bending deformation with lower stiffness, the assembly stress and thermal stress can be transformed into the deformation of the concave cavity folded beam, thus ensuring the zero-bias stability of the vibration beam.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A pressure sensor sensitive structure, characterized in that: include: The pressure-sensitive layer (100) comprises a pressure-sensitive film (110); A vibration beam layer (200) comprises a vibration beam base (210) and a vibration beam structure (220), wherein the vibration beam base (210) is connected to the pressure-sensitive film (110), and the vibration beam structure (220) is connected to the vibration beam base (210); the vibration beam structure (220) comprises a pressure-measuring vibration beam (221), a reference vibration beam (222), and a matching vibration beam (223), and an anchor region (226) of the reference vibration beam (222) is fixedly connected to the vibration beam base (210); a first excitation electrode (224) of the reference vibration beam (222) is led out by routing on the vibration beam base (210); the matching vibration beam (223) and the reference vibration beam (222) are symmetrically arranged on the vibration beam base (210) with respect to the pressure-measuring vibration beam (221), and the anchor region (226) of the matching vibration beam (223) is fixedly connected to the vibration beam base (210); The stress isolation layer (300) comprises a stress isolation ring structure (310), the stress isolation ring structure (310) being connected to a side of the vibration beam base (210) facing away from the pressure-sensitive film (110), the stress isolation ring structure (310) being hollow inside to form a through hole (311), and the vibration beam base (210) covering a first end of the through hole (311); The base layer (400) comprises a quartz base plate (410), wherein the quartz base plate (410) is connected to the stress isolation layer (300), and the quartz base plate (410) covers the second end of the through hole (311).

2. The pressure sensor sensitive structure according to claim 1, characterized in that: The stress isolation ring structure (310) connects the vibration beam layer (200) and the base layer (400) via a bonding glass slurry ring.

3. The pressure sensor sensitive structure according to claim 1, characterized in that: The base layer (400) comprises a quartz base plate (410) and a film-coated getter layer (420), wherein the film-coated getter layer (420) is connected to the quartz base plate (410), the quartz base plate (410) is connected to the stress isolation ring structure (310), and the film-coated getter layer (420) is arranged on a side of the quartz base plate (410) close to the stress isolation ring structure (310).

4. The pressure sensor sensitive structure according to claim 1, characterized in that: The pressure-sensitive film (110) is provided with a first concave cavity (111), a second concave cavity (112) and a convex platform (113); the first concave cavity (111) is provided on a first side of the pressure-sensitive film (110); the second concave cavity (112) is provided on a second side of the pressure-sensitive film (110); the first side of the pressure-sensitive film (110) and the second side of the pressure-sensitive film (110) are opposite to each other; and the convex platform (113) is provided in the first concave cavity (111); An anchor region (226) of at least one of the vibration beam structures (220) is fixedly connected to the boss (113).

5. The pressure sensor sensitive structure according to claim 4, characterized in that: The vibration beam structure (220) comprises a pressure measuring vibration beam (221), a reference vibration beam (222) and a matching vibration beam (223); the anchor region (226) of the pressure measuring vibration beam (221) is fixedly connected to the boss (113); the anchor region (226) of the reference vibration beam (222) is fixedly connected to the vibration beam base (210); the matching vibration beam (223) and the reference vibration beam (222) are symmetrically arranged on the vibration beam base (210) with respect to the pressure measuring vibration beam (221); and the anchor region (226) of the matching vibration beam (223) is fixedly connected to the vibration beam base (210).

6. The pressure sensor sensitive structure according to claim 5, characterized in that: The pressure measuring vibration beam (221), the reference vibration beam (222), and the matching vibration beam (223) have the same size.

7. The pressure sensor sensitive structure according to claim 5, characterized in that: The anchor area (226) of the pressure measuring vibration beam (221) is fixedly connected to the boss (113) via an adhesive material, wherein the adhesive material is one of glass paste, metal solder, epoxy glue and gold-gold bonding material.

8. The pressure sensor sensitive structure according to any one of claims 1 to 4, characterized in that: The vibration beam structure (220) comprises an anchor region (226), a connecting beam (227), a wave node (228), and a tuning fork vibration beam (229); the anchor region (226) is connected to the connecting beam (227), the connecting beam (227) is connected to the wave node (228), and the wave node (228) is connected to the tuning fork vibration beam (229).

9. The pressure sensor sensitive structure according to any one of claims 1 to 4, characterized in that: The pressure-sensitive film (110) is a quartz crystal pressure-sensitive film (110), the vibration beam structure (220) is a quartz crystal vibration beam structure (220), the stress isolation ring structure (310) is a quartz isolation ring structure, and the base layer (400) is a quartz crystal base layer (400).

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