Piezoelectric device

Abstract

The invention provides a piezoelectric device, and relates to the technical field of semiconductors, the piezoelectric device comprises a substrate and a cantilever beam stacked on the substrate, the substrate forms a cavity, and the cantilever beam is divided into a fixed end located on the substrate and a free end located on the cavity; the cantilever beam comprises a piezoelectric layer and at least one first metal layer, the piezoelectric layer and the first metal layer are stacked on the substrate, the piezoelectric layer extends to the substrate and the cavity, the first metal layer is at least suspended at the free end above the cavity and is far away from the fixed end, and the piezoelectric layer and the first metal layer are stacked on the substrate in the extending direction from the free end to the fixed end. A preset distance is formed between the first end face, facing the cavity, of the fixed end and the second end face, facing the fixed end, of the first metal layer. By adjusting the relative position of the first metal layer on the cantilever beam and the fixed end, the stress is partially transferred to the first metal layer, so that the stress of the piezoelectric layer is reduced, and the brittle rupture resistance of the cantilever beam is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly relates to a piezoelectric device. Background Art

[0002] MEMS (Micro-Electro-Mechanical System, also known as microelectronic mechanical system) piezoelectric devices, as an advanced sensor technology, mainly consist of a piezoelectric unit and an ASIC circuit (Application-Specific Integrated Circuit). The main structure of the piezoelectric unit generally includes a cantilever beam or a diaphragm. Due to the material properties of the piezoelectric material, when the cantilever beam is driven (externally driven or self-driven) to vibrate, the cantilever beam will deform in the direction of the arrow in Figure 1 and thus undergo cyclic changes of compression and tension.

[0003] When the cantilever beam / diaphragm undergoes large strains, it is prone to fracture in the root region, and this fracture phenomenon has a serious impact on the application scenarios and service life of the product. Figure 2a shows the situation where the cantilever beam fractures during the reliability shock test, Figure 2b which is a schematic model diagram of the fracture of the cantilever beam of the MEMS piezoelectric device. The fracture generally occurs in the root region, and part of the cantilever beam may remain at the fixed end, as shown in the positions selected by the dashed boxes in Figure 2a and Figure 2b . When 100 samples are selected for the reliability shock test, only 27 devices can pass the test, that is, the qualified rate is only 27%. Therefore, under the existing process capabilities, it is urgent to improve the reliability of the device and increase the yield rate through some improvements. Summary of the Invention

[0004] The purpose of the present invention is to provide a piezoelectric device that can improve the reliability and yield rate of the device.

[0005] On the one hand, the present invention provides a piezoelectric device, including a substrate and a cantilever beam laminated on the substrate. The substrate forms a cavity, and the cantilever beam is divided into a fixed end located on the substrate and a free end located on the cavity; The cantilever beam includes a piezoelectric layer laminated on the substrate and at least one first metal layer. The piezoelectric layer extends onto the substrate and the cavity, and the first metal layer is at least suspended above the cavity at the free end and away from the fixed end. In the extending direction from the free end to the fixed end, a preset distance is formed between the first end face of the fixed end facing the cavity and the second end face of the first metal layer facing the fixed end.

[0006] Optionally, the second end face of the first metal layer extends into the fixed end, and the preset distance between the first end face and the second end face is greater than zero; Alternatively, the second end face of the first metal layer extends to the first end face of the fixed end, and the preset distance between the first end face and the second end face is equal to zero; Alternatively, the first metal layer is located at the free end, and the second end face of the first metal layer does not extend to the first end face of the fixed end. It is defined that the preset distance between the first end face and the second end face is less than zero.

[0007] Optionally, when the preset distance from the first end face to the second end face is less than zero, the preset distance ≥ -25um; When the preset distance between the first end face and the second end face is greater than zero, the preset distance ≥ 25um.

[0008] Optionally, at least one layer of the first metal layer is disposed below the piezoelectric layer, and / or at least one layer of the first metal layer is disposed above the piezoelectric layer, and / or at least one layer of the first metal layer is disposed within the piezoelectric layer.

[0009] Optionally, when the preset distance from the first end face of the first metal layer to the second end face of the fixed end is less than zero, the cantilever beam further includes at least one layer of a second metal layer stacked on the substrate, and at least one layer of the second metal layer is close to the fixed end and extends toward the first metal layer.

[0010] Optionally, the second metal layer is located within the fixed end, or the second metal layer is located within the free end, or the second metal layer extends from the fixed end to within the free end.

[0011] Optionally, the projection of the second metal layer and the first metal layer in the stacking direction do not overlap, or the projection of the second metal layer and the first metal layer in the stacking direction overlaps.

[0012] Optionally, at least one layer of the second metal layer is disposed below the piezoelectric layer, and / or at least one layer of the second metal layer is disposed above the piezoelectric layer, and / or at least one layer of the second metal layer is disposed within the piezoelectric layer.

[0013] Optionally, an oxide layer is further disposed on the substrate corresponding to the fixed end, and the piezoelectric layer and the first metal layer are both located on the oxide layer.

[0014] Optionally, the cantilever beam further includes at least one functional film layer, and at least one of the functional film layers is disposed below the piezoelectric layer, and / or at least one of the functional film layers is disposed above the piezoelectric layer, and / or at least one of the functional film layers is disposed within the piezoelectric layer.

[0015] For the piezoelectric device provided by the present invention, a preset distance is formed between the first end surface of the fixed end and the second end surface of the first metal layer. By adjusting the relative positional relationship between the first metal layer in the cantilever beam and the root of the fixed end of the cantilever beam (the first end surface of the fixed end), the first metal layer with stronger tensile capacity is used to replace the piezoelectric material to bear part of the stress, and part of the stress is transferred to the first metal layer, thereby improving the anti-cracking ability of the cantilever beam. The principle is to disperse the stress generated when the piezoelectric device undergoes strain, so that the first metal layer bears most of the stress, thereby reducing the stress of the piezoelectric layer. And because the metal material has high tensile strength and is not prone to brittle fracture, the anti-cracking ability of the root of the cantilever beam is enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for the present invention will be briefly introduced below. It should be understood that the following drawings only show some examples of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0017] Figure 1 is a schematic diagram of the force deformation of the cantilever beam of the MEMS piezoelectric device; Figure 2a is a schematic diagram of the fracture of the cantilever beam of the MEMS piezoelectric device; Figure 2b is a schematic model diagram of the fracture of the cantilever beam of the MEMS piezoelectric device; Figure 3 is a schematic diagram of the wurtzite crystal structure of AlN; Figure 4 is a schematic diagram of the chemical bond between aluminum and nitrogen atoms; Figure 5 is a top view of the AlN crystal structure; Figure 6 is a schematic diagram of the fracture of the cantilever beam of the MEMS piezoelectric device due to stress concentration force; Figure 7 is one of the schematic diagrams of the structure of the piezoelectric device provided by the present invention; Figure 8 is another schematic diagram of the structure of the piezoelectric device provided by the present invention; Figure 9 is yet another schematic diagram of the structure of the piezoelectric device provided by the present invention; Figure 10 is Figure 7, Figure 8 , Figure 9 The corresponding stress distribution simulation diagram; Figure 11 is Figure 7 , Figure 8 , Figure 9 The curve graph of the maximum tensile stress distribution corresponding thereto; Figure 12 is Figure 7 , Figure 8 , Figure 9 One of the influence trend diagrams of stress; Figure 13 is Figure 7 , Figure 8 , Figure 9 Another influence trend diagram of stress; Figure 14 The sectional view of the surface topography of the piezoelectric device provided by the present invention; Figure 15 The schematic diagram of the rugged surface structure design of the piezoelectric device provided by the present invention; Figure 16 The schematic diagram of the rugged surface stress distribution of the piezoelectric device provided by the present invention; Figure 17 The normalized maximum tensile stress curve graph of the rugged surface and the flat surface of the piezoelectric device provided by the present invention; Figure 18 The comparison diagram of different coverage areas of the first metal layer of the piezoelectric device provided by the present invention; Figure 19 The schematic diagram of the bending resistance and brittle fracture resistance model structure of the piezoelectric device provided by the present invention; Figure 20 The schematic diagram of the surface topography characterization of the piezoelectric device provided by the present invention; Figure 21 The fourth schematic diagram of the structure of the piezoelectric device provided by the present invention; Figure 22 The fifth schematic diagram of the structure of the piezoelectric device provided by the present invention; Figure 23 The sixth schematic diagram of the structure of the piezoelectric device provided by the present invention; Figure 24 The seventh schematic diagram of the structure of the piezoelectric device provided by the present invention; Figure 25 The eighth schematic diagram of the structure of the piezoelectric device provided by the present invention; Figure 26 The ninth schematic diagram of the structure of the piezoelectric device provided by the present invention; Figure 27 The tenth schematic diagram of the structure of the piezoelectric device provided by the present invention; Figure 28 The eleventh schematic diagram of the structure of the piezoelectric device provided by the present invention; Figure 29 It is the twelfth schematic diagram of the piezoelectric device structure provided by the present invention; Figure 30 It is the stress distribution diagram of the MEMS piezoelectric device; Figure 31 It is the thirteenth schematic diagram of the piezoelectric device structure provided by the present invention; Figure 32 It is the fourteenth schematic diagram of the piezoelectric device structure provided by the present invention; Figure 33 It is the fifteenth schematic diagram of the piezoelectric device structure provided by the present invention; Figure 34 It is the sixteenth schematic diagram of the piezoelectric device structure provided by the present invention; Figure 35 It is the seventeenth schematic diagram of the piezoelectric device structure provided by the present invention; Figure 36 It is the eighteenth schematic diagram of the piezoelectric device structure provided by the present invention; Figure 37 It is the nineteenth schematic diagram of the piezoelectric device structure provided by the present invention; Figure 38 It is the twentieth schematic diagram of the piezoelectric device structure provided by the present invention; Figure 39 It is the twenty - first schematic diagram of the piezoelectric device structure provided by the present invention; Figure 40 It is the twenty - second schematic diagram of the piezoelectric device structure provided by the present invention; Figure 41 It is the twenty - third schematic diagram of the piezoelectric device structure provided by the present invention.

[0018] Icon: 10 - Substrate; 11 - Cavity; 12 - Oxide layer; 13 - First metal layer; 14 - Piezoelectric layer; 15 - Second metal layer; 16 - Functional film layer; A - Stress concentration point; B1 - Fixed end; B2 - Free end; D - Preset distance; E1 - First end face; E2 - Second end face; F - Tensile stress; G - Corner area; S - Extension direction. Detailed implementation manners

[0019] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the accompanying drawings in the present invention.

[0020] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "inner" and "outer" is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present invention is customarily placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, terms such as "first" and "second" are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0021] It should also be noted that unless otherwise clearly specified and defined, the terms "arrangement" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] The crystal lattice of piezoelectric materials is generally a wurtzite crystal structure. For example, Figure 3 , Figure 4 As shown, taking the AlN (aluminum nitride) crystal lattice structure as an example, the crystal lattice structure of piezoelectric materials has no center of symmetry, and the finally formed crystal structure is as shown in Figure 5 . Such crystals can be regarded as composed of multiple hexagonal prisms. Inside a hexagonal prism, the forces between atoms are very tight, but the forces between prisms are relatively weak.

[0023] When the piezoelectric material is subjected to a transverse tensile stress F, the crystal structure is very likely to break along the interface of two prisms. Macroscopically, it is manifested that the cantilever beam of the piezoelectric device is prone to brittle fracture in the direction perpendicular to the cantilever beam. As shown in Figure 6 , brittle fracture may occur at the stress concentration point A.

[0024] Based on this, the present invention provides a piezoelectric device. Please refer to Figures 7 - 9 As shown, it includes: a substrate 10 and a cantilever beam laminated on the substrate 10. The substrate 10 forms a cavity 11, and the cantilever beam is divided into a fixed end B1 located on the substrate 10 and a free end B2 located on the cavity 11; The cantilever beam includes a piezoelectric layer 14 laminated on the substrate 10 and at least one first metal layer 13. The piezoelectric layer 14 extends to the substrate 10 and the cavity 11. The first metal layer 13 is at least suspended above the cavity 11 at the free end B2 and away from the fixed end B1. In the extension direction S from the free end B2 to the fixed end B1, a preset distance D is formed between the first end face E1 of the fixed end B1 facing the cavity 11 and the second end face E2 of the first metal layer 13 facing the fixed end B1.

[0025] A cantilever beam is formed on a substrate 10 with a cavity 11. The area of the cantilever beam located on the substrate 10 is called the fixed end B1, and the area located on the cavity 11 is called the free end B2.

[0026] Specifically, the cantilever beam includes a piezoelectric layer 14 and a first metal layer 13. The piezoelectric layer 14 covers both the substrate 10 and the cavity 11. There is at least one layer of the first metal layer 13, and the first metal layer 13 is at least suspended above the cavity 11 at the free end B2 and away from the fixed end B1. That is to say, the first metal layer 13 extends from the free end B2 towards the fixed end B1.

[0027] For example Figure 9 As shown, the first metal layer 13 is located at the free end B2, and the second end face E2 of the first metal layer 13 towards the fixed end B1, that is, the left end of the first metal layer 13, has not extended to the first end face E1 of the fixed end B1. At this time, it is defined that the preset distance D between the first end face E1 and the second end face E2 is less than zero because the defined extension direction S is from right to left, and the second end face E2 is on the right side of the first end face E1, making the preset distance D between the first end face E1 and the second end face E2 in the reverse direction of the extension direction S, that is, the direction is negative.

[0028] The second end face E2 of the first metal layer 13 continues to extend towards the first end face E1 of the fixed end B1 until it extends to be flush with the first end face E1, forming Figure 8 the structure shown. At this time, the preset distance D between the first end face E1 and the second end face E2 is zero.

[0029] The second end face E2 of the first metal layer 13 continues to extend along the extension direction S and extends beyond the first end face E1 of the fixed end B1 into the fixed end B1, obtaining Figure 7 the structure shown. At this time, the direction of the preset distance D between the first end face E1 and the second end face E2 is positive and greater than zero.

[0030] A preset distance D is formed between the first end face E1 of the fixed end B1 and the second end face E2 of the first metal layer 13. The value of the preset distance D is different in Figures 7 - 9 , that is, the relative position relationship between the first end face E1 of the fixed end B1 and the second end face E2 of the first metal layer 13 is different. By adjusting the relative position relationship between the first metal layer 13 in the cantilever beam and the root of the fixed end B1 of the cantilever beam (the first end face E1 of the fixed end B1), the first metal layer 13 with stronger tensile strength is used to replace the piezoelectric material to bear part of the stress, thereby improving the anti-cracking ability of the cantilever beam. The principle is to disperse the stress when the piezoelectric device undergoes strain, so that the first metal layer 13 bears most of the stress, and because the tensile strength of the metal material is high and it is not easy to crack, the anti-cracking ability of the root of the cantilever beam is enhanced.

[0031] Figure 10 The stress distribution simulation images of the piezoelectric device after Figures 7 - 9 are shown from top to bottom. Figure 10 In the figure, the chromaticity bar represents the magnitude of the stress value. The stress image shows the stress distribution through the shades of gray corresponding to different sections, where the uppermost section has the maximum stress.

[0032] Figure 10 The simulation results of are obtained under the same driving conditions. Due to the symmetry of the cantilever beam bending, only the modeling of the first metal layer 13 located below the piezoelectric layer 14 and the simulation of the downward bending are carried out.

[0033] Corresponding to Figure 8 , it can be seen from Figure 10 that the corner region G of the fixed end B1 of the cantilever beam is the stress concentration region for the downward bending of the entire model. This corner region G is a relatively large range, not a single corner point.

[0034] Among them Figure 9 The corresponding structure does not show the first metal layer 13 in Figure 10 because after the local image is enlarged, the first metal layer 13 corresponding to Figure 9 cannot be displayed together within the limited image range, but it does not mean that Figure 9 the corresponding simulation image does not have the first metal layer 13.

[0035] Figure 11 shows Figures 7 - 9 the normalized stress performance of the piezoelectric device model. The curve represents the trend of the maximum tensile stress in the piezoelectric layer 14 and the first metal layer 13 changing with time. By comparison, the stress distribution of Figures 7 - 9 three types of models can be judged. Among them, Figure 7 is Example 1, Figure 8 is Example 2, Figure 9 is Example 3, and the first metal layer 13 can use molybdenum as the material.

[0036] Among them, the AlN region (i.e., the piezoelectric layer 14) where the first metal layer 13 is "shortened" (corresponding to Figure 9 ) bears the maximum stress value, and the first metal layer 13 bears the minimum stress value. This is because in the region with the maximum strain, Figure 9 the first metal layer 13 of the model has the least participation. The stress situation in the region with the maximum strain is equivalent to that without the first metal layer 13, and all are borne by AlN.

[0037] It can be seen from the change of the stress curve that as the length of the first metal layer 13 increases, the maximum stress value shared by the first metal layer 13 continuously increases, and the maximum stress value borne by AlN continuously decreases. In particular, Figure 7The maximum stress of the corresponding (extended) first metal layer 13 exceeds the maximum stress value of AlN.

[0038] Furthermore, Figure 12 shows the influence trend of the stress corresponding to different lengths of the first metal layer 13. The AlN pressure is the pressure when the piezoelectric layer 14 is aluminum nitride, and the Mo (molybdenum) pressure is the pressure when the first metal layer 13 is metal molybdenum. The abscissa represents the preset distance D from the first end face E1 of the fixed end B1 to the leftmost end (the second end face E2) of the first metal layer 13. The direction to the left of the preset distance D is the positive direction. As the x-axis increases, the structural model changes from Figure 9 the corresponding structure to Figure 7 the corresponding structure.

[0039] It can be seen from Figure 12 that when the first metal layer 13 is far from the fixed end B1 ( Figure 9 ), the stress sharing effect of the first metal layer 13 on the cantilever beam is small. As the left end (the second end face E2) of the first metal layer 13 gradually approaches the fixed end B1, the pressures on the first metal layer 13 and the AlN layer begin to change significantly at -25 μm. The stress borne by the first metal layer 13 increases suddenly, while that of the AlN layer decreases suddenly. Until the first metal layer 13 crosses the fixed end B1 and extends 25 μm into the fixed end B1 ( Figure 7 ), the stress on the AlN layer reaches the minimum value, and the stress on the first metal layer 13 reaches the maximum value. After that, as the first metal layer 13 continues to extend, the stresses on the two types of film layers remain stable and no longer have an obvious change trend.

[0040] In summary, conclusion 1 can be obtained: Under the same driving force, the first metal layer 13 plays a good protective role for the AlN layer (the piezoelectric layer 14), greatly reducing the brittle fracture risk of the cantilever beam under the same conditions. In particular, when the preset distance D from the first end face E1 to the second end face E2 is less than zero ( Figure 9 ), when the preset distance D ≥ -25 μm, the protective effect of the first metal layer 13 is obvious; when the preset distance D between the first end face E1 and the second end face E2 is greater than zero ( Figure 7 ), after the preset distance D ≥ 25 μm, the protective effect of the first metal layer 13 reaches the maximum.

[0041] Figure 13 shows the influence trend of the change of the preset distance D between the first end face E1 and the second end face E2 on the stress under the condition of different cantilever beam lengths. To verify whether different cantilever beam lengths have an impact on the change of the preset distance D, Figure 13 the length of the cantilever beam is reduced by 0.2 mm compared with Figure 12 . It can be seen from the Figure 13 data that the change of the cantilever beam length has an impact on conclusion 1.Figure 12 The protective effect of the first metal layer 13 shown is basically not affected.

[0042] In addition, Figure 14 The figure shows a cross-sectional view of the AlN film layer covered with a metal layer. It can be seen that the surface of the AlN film layer has a rugged morphology like mountains / valleys. The metal layer covering it can relieve the surface unevenness, making the surface of the entire composite film layer a relatively flat and continuous surface.

[0043] During the verification process, for the cantilever beam not protected by the metal layer, the actual impact acceleration at which it breaks is much smaller than the theoretical value of the structural simulation. Therefore, Figure 14 the rugged AlN surface shown was studied.

[0044] It is considered that the rugged morphology is also one of the reasons for the easy fracture in the root area of the cantilever beam. Because considering its morphological characteristics, this morphology like mountains / valleys will cause stress concentration at the 'valleys' when stress deformation and bending occur, which is more likely to cause intergranular fracture of the AlN film layer, and then lead to the fracture of the cantilever beam. After simulation, this view can be demonstrated based on the results.

[0045] The simulation model was processed, and a morphological structure design equivalent to the rugged surface was added to the surface of the root area of the cantilever beam, as Figure 15 shown.

[0046] Figure 16 The stress distribution diagram of the model under external excitation is given.

[0047] The models all adopt the method of " Figure 8 the first metal layer 13, and the second end face E2 of the first metal layer 13 is flush with the first end face E1 of the fixed end B1".

[0048] From Figure 16 it can be seen that after adding the fine rugged surface morphology, stress concentration points of tensile stress F will be formed at the valleys on the upper surface. Its value is even greater than the maximum compressive stress in the lower metal layer area. ( Figure 16 shows the maximum and minimum values of the section. The absolute maximum value of the uppermost section is 5.59x10 7 which is greater than the absolute maximum value of 5.37x10 7 )

[0049] By comparison, it can be seen that there are more stress concentration points on the rough surface compared to the flat surface. This further proves that when the surface of the film layer is rough and uneven, under the condition of the same tensile stress F, there will be more stress concentration points on the rough surface, and it will bear greater stress than the flat surface. For piezoelectric materials, due to the lattice characteristics, cracks are more likely to occur at these stress concentration points, and these cracks will gradually spread and ultimately lead to the brittle fracture of the cantilever beam.

[0050] Figure 17 Figure 4 shows the normalized maximum tensile stress curves of the rough surface and the flat surface under the same conditions. Figure 17 It can be seen that under the same conditions, the maximum tensile stress of the flat surface is only 40% of the maximum tensile stress of the rough surface. Thus, conclusion 2 is obtained: the rough surface will greatly weaken the anti-brittle fracture performance of the cantilever beam when subjected to a large tensile stress.

[0051] In addition, during the actual testing process, the thicker the metal layer on the surface of the cantilever beam, the higher the flatness of its surface. This is due to the metal deposition process and the characteristics of the metal material. The metal film deposition process will fill and flatten the relatively rough surface. Therefore, the thicker the metal layer, the higher the improvement in the anti-brittle fracture performance of the cantilever beam, and the cantilever beam is not likely to break.

[0052] Figure 18 Figure 5 shows the schematic diagrams with different covered areas of the metal layer. Figure 18 The anti-brittle fracture performance of the cantilever beams in Figure 5 shows H < I < J. That is, in the case of a rough surface, the anti-brittle fracture performance of the cantilever beam increases with the increase in the covered area of the surface metal layer. This conclusion can be obtained by combining conclusion 1 and conclusion 2.

[0053] The anti-brittle fracture ability of the cantilever beam of the piezoelectric device of the present invention has been greatly improved. Figure 19 Figure 6 shows the improved cantilever beam bending model structure. Subsequently, when the cantilever beam is subjected to a squeezing test, it can be clearly observed that the cantilever beam recovers after bending and does not break.

[0054] For the impact test of the improved product, a total of 200 samples were tested, and the number of samples that broke was 0.

[0055] The improved surface topography is as shown in Figure 20 Figure 7. Compared with the device topography before improvement in the prior art, the surface of the piezoelectric device of the present invention is covered by a metal electrode layer.

[0056] In summary, for the piezoelectric device provided by the present invention, by adjusting the relative position of the first metal layer 13 on the cantilever beam and the fixed end B1, part of the stress is transferred to the first metal layer 13, thereby reducing the stress of the piezoelectric layer 14 and improving the anti-cracking ability of the cantilever beam. The extension range of the first metal layer 13 can be from not reaching the root of the fixed end B1 to extending into the fixed end B1. When the second end face E2 of the first metal layer 13 does not reach the fixed end B1, a better effect is achieved when the preset distance D between the first end face E1 and the second end face E2 is in the range of ≥ -25um. When the second end face E2 extends into the fixed end B1 and the preset distance D is greater than 25um, the anti-cracking effect in the root area of the cantilever beam reaches the best. The setting of the first metal layer 13 has a certain improvement effect on the anti-brittleness of the piezoelectric device, and this effect increases with the increase of the coverage range of the first metal layer 13 and will gradually reach the maximum. That is Figure 9 The effect begins to be significant after the preset distance D ≥ -25um, Figure 7 The best effect is obtained after the preset distance D ≥ 25um.

[0057] In addition, the anti-cracking effect obtained by the first metal layer 13 covering the rough surface increases with the increase of the coverage area of the first metal layer 13: As can be seen from Conclusion 2, the rugged surface has a great impact on the anti-cracking performance of the cantilever beam. Therefore, the effect of the first metal layer 13 covering the surface to make the surface flat contributes greatly to the improvement of the anti-cracking performance of the cantilever beam. With the increase of the coverage area of the first metal layer 13 and the reduction of the rugged surface, its anti-cracking performance will continue to increase until the surface is completely covered by the first metal layer 13.

[0058] On the other hand, in the above Figures 7 - 9 , the first metal layer 13 is located below the piezoelectric layer 14, and the maximum stress distribution area when the cantilever beam undergoes strain is on the upper and lower sides of the root of the structure (as can be seen from Figure 10 ), so it is extremely important to arrange metal layers on the upper and lower sides of the cantilever beam. Special metal layers can be arranged on both the upper and lower sides at the same time. Arranging a metal layer within the piezoelectric layer 14 or additionally arranging a metal layer on the premise that there are metal layers on both the upper and lower sides should belong to the same technology.

[0059] Therefore, in some other examples, at least one first metal layer 13 is arranged below the piezoelectric layer 14, and / or, at least one first metal layer 13 is arranged above the piezoelectric layer 14, and / or, at least one first metal layer 13 is arranged within the piezoelectric layer 14.

[0060] As Figures 7 - 9 shown, there is only one first metal layer 13, and it is all located below the piezoelectric layer 14.

[0061] As Figures 21 - 26As shown, the first metal layer 13 has two layers, located below and above the piezoelectric layer 14 respectively. And the lengths of the two layers of the first metal layer 13 in the extending direction S can be the same, that is, the preset distance D from the first end face E1 of the fixed end B1 to the second end face E2 of the first metal layer 13 can be the same. For example Figures 21 - 23 As shown; the lengths of the two layers of the first metal layer 13 in the extending direction S can also be different. For example Figures 24 - 26 As shown.

[0062] Of course, the first metal layer 13 can also have only one layer, only set above the piezoelectric layer 14.

[0063] It can also be as Figures 27 - 29 As shown, on the premise that there is a metal layer on at least one side of the piezoelectric layer 14, adding at least one layer of metal layer at any position in the piezoelectric layer 14 material can slightly improve the anti-cracking performance.

[0064] As Figure 30 As shown, the stress value of the cantilever beam at the position of the black dotted line is small, and the stress gradually increases from the dotted line to the upper and lower sides until it reaches the maximum at the upper and lower sides of the cantilever beam. Therefore, setting metal layers on the upper and lower sides of the cantilever beam has the best effect. Inserting a metal layer in the piezoelectric layer 14 has a smaller effect, but it also has a certain improvement effect, and its improvement effect should conform to the aforementioned conclusion 1.

[0065] Figures 31 - 33 shows the situation of inserting at least one layer of metal layer in the piezoelectric layer 14 material. However, this setting method has some defects, that is, without the protection of a metal layer outside the piezoelectric layer 14 material, there may still be a high probability that cracks will occur on the surface of the piezoelectric layer 14 material due to the lattice structure characteristics, and then expand during the subsequent vibration process, ultimately leading to the scrapping of the device. But from Figure 30 It can be seen that although the effect of inserting a metal layer in the piezoelectric layer 14 is not the best, it can still improve the anti-cracking effect of the cantilever beam.

[0066] In addition, the cantilever beam further includes at least one layer of the second metal layer 15 laminated on the substrate 10, and at least one layer of the second metal layer 15 is close to the fixed end B1 and extends towards the first metal layer 13.

[0067] Figures 34 - 39 shows the situation where the second metal layer 15 can also be used as the metal layer on the upper and lower sides of the cantilever beam to enhance the anti-cracking property.

[0068] The coverage condition of the second metal layer 15 should conform to conclusion 1, that is, the best coverage range of the second metal layer 15 is in the interval of -25um to 25um. As Figure 35 As shown, the second metal layer 15 extends from the fixed end B1 to the inside of the free end B2; the left end of the second metal layer 15 can be as Figure 38extends towards the left end as shown to achieve full coverage of the fixed end B1.

[0069] The second metal layer 15 can also be located at the fixed end B1 or the free end B2 as shown in Figure 34 and Figure 36 shown. Its coverage range intersects with [-25um, 25um], but its performance is slightly weaker compared to Figure 35 However, it can still play a role in enhancing the anti-cracking property.

[0070] Figures 34 - 38 In Figure 39 shown, the projection of the second metal layer 15 and the first metal layer 13 in the stacking direction does not overlap. Or, it can also be as shown in

[0071] Therefore, at least one second metal layer 15 is disposed below the piezoelectric layer 14, and / or at least one second metal layer 15 is disposed above the piezoelectric layer 14, and / or at least one second metal layer 15 is disposed within the piezoelectric layer 14.

[0072] It should be noted that Figure 36 the shorter second metal layer 15 is for the convenience of drawing. In fact, the distances of the second metal layer 15 from the fixed end B1 in the above examples can be the same or different, which is related to the actual design requirements.

[0073] And, the first metal layer 13 can also be as in the above Figures 34 - 39 where it does not extend to the fixed end B1. When the first metal layer 13 extends to the fixed end B1 or beyond the fixed end B1, the above-described setting manner of the second metal layer 15 can also be applied, and details are not described herein again.

[0074] In the piezoelectric device of the present invention, the cantilever beam can further include at least one functional film layer 16. At least one functional film layer 16 is disposed below the piezoelectric layer 14, and / or at least one functional film layer 16 is disposed above the piezoelectric layer 14, and / or at least one functional film layer 16 is disposed within the piezoelectric layer 14.

[0075] Taking Figure 40 and Figure 41 as an example, in the stacking direction, functional film layers 16 are disposed on both the upper and lower sides of the piezoelectric layer 14. The functional film layer 16 can be a composite film layer, and the functional film layers 16 on the upper and lower sides of the piezoelectric layer 14 can be different, that is, the materials of the two functional film layers 16 can be different, the lengths can be different, and so on.

[0076] The material of the functional film layer 16 is not limited and is specifically selected according to needs.

[0077] The functional film layer 16 can be applied to the above various different examples, and details are not described herein again.

[0078] In each of the above examples, an oxide layer 12 may also be provided in a region corresponding to the fixed end B1 on the substrate 10, and each film layer such as the piezoelectric layer 14, the first metal layer 13, and the second metal layer 15 is located on the oxide layer 12.

[0079] The above description is only an example of the present invention and is not intended to limit the protection scope of the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A piezoelectric device, characterized in that: include: A substrate and a cantilever beam stacked on the substrate, wherein the substrate is formed with a cavity, and the cantilever beam is divided into a fixed end located on the substrate and a free end located on the cavity; The cantilever beam includes a piezoelectric layer and at least one first metal layer stacked on the substrate, the piezoelectric layer extends to the substrate and the cavity, the first metal layer is suspended at least at a free end above the cavity and away from the fixed end, and in the extension direction from the free end to the fixed end, a preset distance is formed between a first end surface of the fixed end facing the cavity and a second end surface of the first metal layer facing the fixed end.

2. The piezoelectric device according to claim 1, characterized in that: The second end surface of the first metal layer extends into the fixed end, and a preset distance between the first end surface and the second end surface is greater than zero; Alternatively, the second end surface of the first metal layer extends to the first end surface of the fixed end, and the preset distance between the first end surface and the second end surface is equal to zero; Alternatively, the first metal layer is located at the free end, the second end surface of the first metal layer does not extend to the first end surface of the fixed end, and a preset distance between the first end surface and the second end surface is defined to be less than zero.

3. The piezoelectric device according to claim 2, characterized in that: When the preset distance from the first end surface to the second end surface is less than zero, the preset distance is ≥-25um; When the preset distance between the first end surface and the second end surface is greater than zero, the preset distance is ≥25 um.

4. The piezoelectric device according to claim 2, characterized in that: At least one first metal layer is disposed below the piezoelectric layer, and / or at least one first metal layer is disposed above the piezoelectric layer, and / or at least one first metal layer is disposed within the piezoelectric layer.

5. The piezoelectric device according to any one of claims 2 to 4, characterized in that: The cantilever beam further includes at least one second metal layer stacked on the substrate, wherein the at least one second metal layer is close to the fixed end and extends toward the first metal layer.

6. The piezoelectric device according to claim 5, characterized in that: The second metal layer is located in the fixed end, or the second metal layer is located in the free end, or the second metal layer extends from the fixed end to the free end.

7. The piezoelectric device according to claim 6, characterized in that: The projections of the second metal layer and the first metal layer in the stacking direction do not overlap, or the projections of the second metal layer and the first metal layer in the stacking direction overlap.

8. The piezoelectric device according to claim 7, characterized in that: At least one second metal layer is disposed below the piezoelectric layer, and / or at least one second metal layer is disposed above the piezoelectric layer, and / or at least one second metal layer is disposed within the piezoelectric layer.

9. The piezoelectric device according to any one of claims 1 to 4 and 6 to 8, characterized in that: An oxide layer is further provided on the substrate corresponding to the fixed end, and the piezoelectric layer and the first metal layer are both located on the oxide layer.

10. The piezoelectric device according to any one of claims 1 to 4 and 6 to 8, characterized in that: The cantilever beam also includes at least one functional film layer, at least one functional film layer is arranged below the piezoelectric layer, and / or at least one functional film layer is arranged above the piezoelectric layer, and / or at least one functional film layer is arranged in the piezoelectric layer.

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