MEMS acoustic wave transducer and manufacturing method thereof

Abstract

The invention relates to a MEMS acoustic wave transducer (1), in particular for generating and / or detecting acoustic waves in the audible wavelength spectrum and / or ultrasonic range, comprising a carrier (2) and at least one piezoelectric element (4, 17) which is arranged on the carrier (2) and which can be pivoted in the direction of a lifting axis (3), said at least one piezoelectric element (4, 17) having at least one piezoelectric layer (5, 25) and at least one structural layer (6, 31), the electrical signal and the deflection of the piezoelectric element (4) can be converted to each other by means of the at least one piezoelectric layer (5, 25). According to the invention, at least one piezoelectric layer (5, 25) is made of aluminum scandium nitrite. The invention also relates to a method for producing a MEMS acoustic wave transducer (1).

Description

Technical Field

[0001] The present invention relates to a MEMS acoustic wave transducer, in particular for generating and / or detecting acoustic waves in the audible wavelength spectrum and / or ultrasonic range, comprising a carrier and at least one piezoelectric element arranged on the carrier and capable of deflecting along a lifting axis, wherein the at least one piezoelectric element has at least one piezoelectric layer and at least one structural layer, wherein the electrical signal and the deflection degree of the piezoelectric element can be converted into each other through the at least one piezoelectric layer. Background Art

[0002] The prior art discloses a piezoelectric element comprising a PZT piezoelectric layer. Summary of the invention

[0003] The purpose of the present invention is to provide a high-performance MEMS acoustic wave transducer.

[0004] The present invention achieves the above-mentioned object by providing a MEMS acoustic wave transducer and a method for manufacturing the same having the features described in the independent claims.

[0005] The present invention provides a MEMS acoustic wave transducer, in particular for generating and / or detecting acoustic waves in the audible wavelength spectrum and / or in the ultrasonic range. The MEMS acoustic wave transducer can be operated as a loudspeaker and / or a microphone.

[0006] The MEMS acoustic wave transducer includes a carrier.

[0007] In addition, the MEMS acoustic wave transducer includes at least one piezoelectric element, which is arranged on the carrier and can be tilted along the lifting axis direction.

[0008] In addition, the MEMS acoustic wave transducer has at least one piezoelectric layer and at least one structural layer, wherein the electrical signal and the deflection of the piezoelectric element can be converted into each other through the at least one piezoelectric layer.

[0009] In addition, at least one piezoelectric layer is made of scandium aluminum nitrite. This piezoelectric layer is extremely robust, mainly due to the scandium content, which can preferably be 10% to 40%.

[0010] According to an advantageous development of the invention, at least one structural layer is made of a polymer. The polymer may be polyamide. With the aid of the at least one polymer structural layer, a greater deflection of the piezoelectric element can be achieved. Additionally or alternatively, the length of the piezoelectric element can also be shortened, so that at least the deflection can be kept constant.

[0011] Advantageously, the piezoelectric element has a compensation layer. The compensation layer can be used to adjust the mechanical stress of the polymer structural layer. The structural layer is easy to shrink due to being made of polymer. At least one structural layer can generate internal mechanical stress due to its production properties and / or the polymer, which causes the structural layer to shrink. In the static state, the piezoelectric element will bend upward or in the direction of the structural layer. The mechanical stress can be compensated by means of the compensation layer. In this case, the mechanical stress of the compensation layer can offset, compensate and / or balance the at least one structural layer. The compensation layer is used to compensate the mechanical stress in the at least one structural layer. Additionally or alternatively, the compensation layer can be used to stretch the at least one structural layer. In this case, the compensation layer keeps the at least one structural layer in a stretched orientation and prevents the structural layer from shrinking and deforming like a rubber band due to mechanical stress. Additionally or alternatively, the compensation layer can be used to prevent the at least one polymer structural layer from shrinking. The compensation layer offsets the mechanical stress of the at least one polymer structural layer and / or is stronger and / or more rigid than the mechanical stress of the at least one structural layer. As a result, shrinkage of the at least one structural layer can be prevented. The force of the at least one polymer structural layer is opposite to the force of the compensation layer and / or advantageously balances and / or cancels each other out. This prevents the structural layer from shrinking. However, the compensation layer does not prevent the piezoelectric element from deflecting. The mechanical stress of the compensation layer is adjusted so that the rubber-like shrinkage of the structural layer is prevented, balanced or compensated. In addition, the compensation can be used to ensure that the piezoelectric element is in a stress-free state in the static position.

[0012] Furthermore, the neutral layer or neutral plane of the piezoelectric element can be positioned with the aid of the compensation layer. The piezoelectric element is a cantilever and compressive and tensile stresses are generated inside the piezoelectric element when it deflects. The range of the compressive and tensile stresses depends on whether the piezoelectric element deflects upward or downward. Compressive stress is formed on the side to which the piezoelectric element deflects. Tensile stress is formed on the other side of the piezoelectric element. This is exactly the general principle of strength theory. In the plane of the piezoelectric element, i.e. in the neutral plane or neutral layer, tensile stress and compressive stress cancel each other out, so that there is no stress in this plane. However, the deflection of the piezoelectric element depends on the position of this neutral plane or neutral layer in the piezoelectric element. The position of the neutral plane or neutral layer can be adjusted by changing the mechanical properties of the compensation layer. For example, the compensation layer can be made thicker or thinner so that the neutral plane or neutral layer is displaced. This displacement or positioning of the neutral plane or neutral layer is parallel to the lifting axis. As a result, the neutral plane or neutral layer can be displaced parallel to the lifting axis.

[0013] Advantageously, the piezoelectric layer is arranged between the carrier and the structural layer in the direction of the lifting axis.

[0014] Advantageously, the structural layer is arranged between the piezoelectric layer and the compensation layer.

[0015] Advantageously, the compensation layer is made of metal, in particular gold, and / or silicon dioxide, in particular TEOS. This allows the compensation layer to be formed advantageously.

[0016] Advantageously, the length of the piezoelectric element in its longitudinal direction, in particular from the carrier to the free end of the piezoelectric element, is 0.5 mm to 2 mm.

[0017] Advantageously, the compensation layer extends in the longitudinal direction of the piezoelectric element to the carrier and / or the free end of the piezoelectric element.

[0018] Advantageously, at least one piezoelectric element comprises a plurality of piezoelectric layers, in particular two to six piezoelectric layers, preferably four piezoelectric layers.

[0019] Advantageously, at least one piezoelectric element comprises at least one electrode layer. By means of the at least one electrode layer, an electrical signal causing the piezoelectric element to deflect and / or an electrical signal formed when the piezoelectric element deflects can be exchanged.

[0020] Advantageously, at least one piezoelectric element comprises at least one insulating layer.

[0021] Advantageously, at least one piezoelectric element is formed by a plurality of piezoelectric layers and electrode layers in a sandwich manner.

[0022] Advantageously, the MEMS acoustic wave transducer comprises a coupling element such that the at least one piezoelectric element can be coupled to the diaphragm.

[0023] In a further development of the present invention, the piezoelectric element and the coupling element are coupled to each other via at least one spring element, wherein the at least one spring element is preferably arranged between the structural layer and the coupling element in the longitudinal direction of the piezoelectric element.

[0024] Advantageously, the spring element is preferably formed only from structural layers and / or polymers. This allows the spring element to be designed in a simple manner. Additionally or alternatively, the spring element has the mechanical properties of a polymer.

[0025] Advantageously, the piezoelectric element and the coupling element have the same layered structure as one another.

[0026] Advantageously, the compensation layer has a thickness of 0.2 μm to 4 μm. Alternatively, the compensation layer may have a thickness of 0.5 μm to 3 μm. Furthermore, the compensation layer may have a thickness of 0.6 μm to 2 μm. Alternatively, the compensation layer may have a thickness of 1 μm to 2 μm. In this way, shrinkage of the structural layer can be prevented or compensated by means of the compensation layer.

[0027] In an improved solution of the present invention, the thickness of the structural layer is 10 μm to 50 μm.

[0028] Advantageously, at least one piezoelectric element has at least one notch. The mechanical properties of the piezoelectric element can be adjusted by means of the notch. This makes it possible, for example, to reduce stresses in the piezoelectric element and / or to adjust movement properties. The at least one notch can be arranged in at least one piezoelectric layer, in at least one electrode layer, in at least one insulating layer, in at least one structural layer and / or in at least one compensation layer.

[0029] It is also advantageous if the modulus of elasticity of the polymer structural layer is 2 GPa to 50 GPa, in particular 2 GPa to 5 GPa, preferably 3.5 GPa to 4 GPa.

[0030] Advantageously, the polymer structural layer has a tensile strength of 70 MPa to 100 MPa, in particular 85 MPa to 95 MPa.

[0031] Due to the above-mentioned mechanical properties of at least one structural layer, the deflection can be increased and / or the deflection size can be kept at least the same or the piezoelectric element can be shortened when the deflection is increased.

[0032] It is also advantageous if the mechanical stress state of the compensation layer is equal to or at least slightly higher than the mechanical stress state of at least one structural layer. Additionally or alternatively, the electrical resistance of the compensation layer may be higher than the electrical resistance of the structural layer. The mechanical stress state of the compensation layer may counteract the mechanical stress state of at least one structural layer. In this way, the compensation layer maintains the tensile orientation of at least one structural layer. As a result, the compensation layer can resist or prevent the structural layer from shrinking due to mechanical stress. If there are multiple structural layers, the mechanical stress state of the compensation layer is equal to or higher than the mechanical stress state of the combined structural layer. Additionally or alternatively, the mechanical stress state of the compensation layer may also counteract the piezoelectric element or make the piezoelectric element stress-free in a neutral position. The mechanical stress state depends on a number of factors. The desired mechanical stress state of the compensation layer depends on the thickness of the structural layer or the thickness of all structural layers and on the elastic modulus, tensile strength and / or elasticity of the structural layer or polymer. The polymer may exhibit rubber elasticity, so that the structural layer tends to shrink. This mechanical stress state of the compensation layer makes it possible to counteract the shrinkage of the polymer. The shrinkage force of the polymer depends on the thickness and strength of the polymer, i.e., for example, on the rubber elastic strength. The mechanical stress state of the compensation layer depends inter alia on the thickness and the elastic modulus or the compressive strength of the compensation layer.

[0033] The mechanical stress state of the compensation layer is equal to or higher than the mechanical stress state of the structural layer or the entirety of the structural layers and / or the piezoelectric layer. This equal or higher mechanical stress state enables the compensation layer to hold the structural layer and / or the piezoelectric layer in their stretched position and impart stability to them. The compensation layer serves to counteract the tendency of the structural layer to contract due to its elasticity.

[0034] Advantageously, the mechanical stress state of the compensation layer offsets the mechanical stress of at least one structural layer and / or at least one piezoelectric layer, thereby achieving compensation and / or balancing. For example, the mechanical stress of the compensation layer may be 50 MPa to 1000 MPa. In addition, the mechanical stress of the compensation layer may be 100 MPa to 300 MPa. In addition, the mechanical stress of the compensation layer may be 240 MPa.

[0035] The required mechanical stress of the compensation layer may be determined by a variety of factors. These factors include the thickness of the structural layer, the elastic modulus (E modulus), tensile strength and elasticity of the structural layer or polymer. Thicker structural layers require correspondingly stronger compensation layers and / or compensation layers with higher mechanical stress to balance the elastic forces. Advantageously, the compensation layer has the ability to counteract this shrinkage.

[0036] The force with which the polymer tends to shrink depends on several factors. These factors include the thickness of the polymer and the elastic strength of the polymer. Thicker polymers produce stronger mechanical stresses. The mechanical stress of the compensation layer is also determined by its own thickness and elastic modulus. A thicker compensation layer has a higher elastic modulus and can offset the stronger mechanical stress in the polymer.

[0037] Advantageously, the strength of the compensation layer is sufficient to balance the elastic restoring force of the structural layer, thereby maintaining the stability of the overall structure.

[0038] It is also advantageous if the compensation layer has a reinforcement structure. For example, the compensation layer can have a strip-shaped reinforcement structure or be designed in this way. This can achieve the necessary mechanical stress to prevent the structural layer from shrinking and can save material and / or place material at will.

[0039] Advantageously, the polymer structural layer can be formed to have an elongation of 3% to 10%.

[0040] The present invention also provides a method for manufacturing a MEMS acoustic wave transducer, which is particularly used for generating and / or detecting acoustic waves in the audible wavelength spectrum and / or ultrasonic range. The method for manufacturing a MEMS acoustic wave transducer can be performed as follows: the MEMS acoustic wave transducer is configured to have at least one of the above and / or following features.

[0041] In the method, at least one piezoelectric element is formed on a carrier, the piezoelectric element comprising at least one piezoelectric layer and at least one structural layer coupled thereto.

[0042] Furthermore, a polymer may be disposed on the piezoelectric layer to form at least one structural layer.

[0043] At least one piezoelectric layer is made of scandium aluminum nitrite.

[0044] It is also advantageous if the at least one piezoelectric element is formed from a plurality of piezoelectric layers, in particular from two to six piezoelectric layers, in particular four piezoelectric layers.

[0045] Advantageously, at least one piezoelectric element is formed by a plurality of piezoelectric layers and at least one electrode layer in a sandwich manner.

[0046] The multiple piezoelectric layers and the multiple electrode layers may be alternately arranged one above the other.

[0047] It is also advantageous if at least one insulating layer is arranged when forming the at least one piezoelectric element.

[0048] It is useful to arrange the polymer structure layer on the side of the piezoelectric layer facing away from the carrier.

[0049] In a further development of the invention, a polymer structural layer is arranged on at least one piezoelectric layer after the piezoelectric layer and / or the coupling element have been formed and / or after the carrier, the piezoelectric layer and / or the coupling element have been post-processed, in particular separated from one another, in particular by etching.

[0050] Advantageously, the piezoelectric element and the coupling element are formed together in layers, which is preferably done on a carrier.

[0051] It is advantageous if, after the layered construction of the piezoelectric element and the coupling element, the piezoelectric element and the coupling element are at least partially separated from one another, in particular by etching.

[0052] It is also advantageous if at least one polymer structural layer is laminated onto the piezoelectric layer and / or the coupling element, in particular in the form of a polymer foil, preferably a self-adhesive polymer foil.

[0053] Advantageously, a two-layer structural layer is formed, which is preferably arranged one above the other and / or is made of the same or different polymers.

[0054] Advantageously, the polymer structure layer is laminated at a temperature of 70°C to 90°C.

[0055] Advantageously, after lamination, a polymer curing step takes place, preferably at a temperature of 150° C. to 200° C. and / or for a duration of 0.5 to 2 hours.

[0056] According to an advantageous development of the invention, the compensation layer is arranged on the structural layer.

[0057] It is useful to post-treat at least one of the polymeric structural layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] More advantages of the present invention are described below in conjunction with the embodiments.

[0059] Figure 1 A schematic cross-sectional view of a MEMS acoustic wave transducer having a piezoelectric element composed of at least one piezoelectric layer and at least one structural layer is shown;

[0060] Figure 2 shows a schematic cross-sectional view of a MEMS acoustic wave transducer having two piezoelectric elements and a coupling element;

[0061] Figure 3 shows a schematic cross-sectional view of a MEMS acoustic wave transducer having two piezoelectric elements and two coupling elements;

[0062] Figure 4 A schematic cross-sectional view showing a layered structure of a MEMS acoustic wave transducer;

[0063] Figure 5 A top view of a MEMS acoustic wave transducer is shown.

[0064] Reference numerals

[0065] 1: MEMS acoustic wave transducer; 2: carrier; 3: lifting axis; 4: first piezoelectric element; 5: first piezoelectric layer; 6: first structural layer; 7: compensation layer; 8: free end; 9: first coupling element; 10: first spring element; 11: diaphragm; 12: first coupling plate; 13: diaphragm frame; 14: neutral plane; 15: upper side; 16: lower side; 17: second piezoelectric element; 18: second spring element; 19: second coupling element; 20: second coupling plate; 21: construction direction; 22: first electrode layer; 24 : second electrode layer; 25: second piezoelectric layer; 26: third electrode layer; 27: first insulating layer; 28: second insulating layer; 29: contact layer; 30: first gap; 31: second structural layer; 32: second gap; 33: length; 34: thickness; 35: notch; 36: third piezoelectric element; 37: fourth piezoelectric element; 38: fifth piezoelectric element; 39: sixth piezoelectric element; 40: third spring element; 41: fourth spring element; 42: fifth spring element; 43: sixth spring element; 44: cross section. DETAILED DESCRIPTION

[0066] Figure 1 A perspective view of a MEMS acoustic wave transducer is shown. For example, with the aid of the MEMS acoustic wave transducer 1, sound waves in the audible wavelength spectrum can be generated, so that it can be used as a MEMS loudspeaker. Additionally or alternatively, with the aid of the MEMS acoustic wave transducer 1, sound waves in the audible wavelength spectrum can be recorded, so that it can be used as a MEMS microphone. The MEMS acoustic wave transducer 1 can also be arranged, for example, in a smartphone, in order to be able to make calls or listen to music, for example. The MEMS acoustic wave transducer 1 can also be arranged, for example, in headphones.

[0067] Other fields of application of the MEMS sound wave transducer 1 include the generation and / or detection of sound waves in the ultrasonic range. The MEMS sound wave transducer 1 can be arranged, for example, in an ultrasonic sensor (eg a distance sensor).

[0068] The MEMS acoustic wave transducer 1 also includes a carrier 2, which can form the basic structure of the MEMS acoustic wave transducer 1. For example, the carrier 2 can include a semiconductor substrate that can be produced by an etching process. For example, the carrier 2 can be made of silicon and / or in the form of a wafer. The present figure shows two carriers 2. However, the carrier 2 can be designed as a frame, and in this cross-sectional view, the two parts of the carrier 2 shown are associated with each other. For example, the carrier 2 can be rectangular in a top view. The top-view orientation is, for example, the direction of the lifting axis 3 described below. For example, the top-view direction can be parallel to the lifting axis 3. For example, if the carrier 2 is designed as a frame, for example, at least one piezoelectric element 4 can at least partially face the interior of the carrier 2.

[0069] Furthermore, at least one piezoelectric element 4 is arranged on the carrier 2. The at least one piezoelectric element 4 can also be coupled to the carrier 2. The at least one piezoelectric element 4 can be deflected along the lifting axis 3 shown. The at least one piezoelectric element 4 can convert an electrical signal into a deflection, so that the MEMS acoustic wave transducer 1 can be used as a loudspeaker or can generate sound waves. Additionally or alternatively, the deflection can be converted into an electrical signal by means of the at least one piezoelectric element 4, so that the MEMS acoustic wave transducer 1 can be used as a microphone or can detect sound waves.

[0070] The free end 8 of the at least one piezoelectric element 4 can be pivoted along the lifting axis 3 .

[0071] The piezoelectric element 4 further includes at least one piezoelectric layer 5. The at least one piezoelectric layer 5 is made of a piezoelectric material. The at least one piezoelectric layer 5 can convert an electrical signal into a deflection and / or convert a deflection into an electrical signal. Here, the piezoelectric layer 5 is made of scandium aluminum nitrate (ScAlN).

[0072] In addition, the piezoelectric element 4 further comprises at least one structural layer 6. The at least one structural layer 6 is coupled to the at least one piezoelectric layer 5. According to the present embodiment, the at least one structural layer 6 is arranged on the side of the at least one piezoelectric layer 5 facing away from the carrier 2. Additionally or alternatively, the at least one piezoelectric layer 5 is arranged between the carrier 2 and the at least one structural layer 6. With the aid of the at least one structural layer 6, the at least one piezoelectric layer 5 can be stabilized. In addition, the at least one structural layer 6 can prevent the at least one piezoelectric layer 5 from being broken when it is deflected. The at least one structural layer 6 can also be used as a bearing layer for the at least one piezoelectric layer 5, 25.

[0073] Advantageously, the structural layer 6 is made of a polymer. Thus, the structural layer 6 is a polymer structural layer. The polymer may be a polyamide. Polymers are softer, in particular softer than silicon, so that the piezoelectric element 4 can be made smaller, but the piezoelectric element 4 can still maintain a high degree of deflection. The performance or power of the piezoelectric element 4 depends in particular on the deflection or elongation. Since the polymer is in particular softer than silicon, the deflection can be kept constant when the piezoelectric element 4 is reduced in size, in particular in length.

[0074] According to the present embodiment, at least one piezoelectric element 4 includes at least one compensation layer 7. The compensation layer 7 can balance the stress generated by the contraction of the polymer structural layer 6. With the aid of the compensation layer 7, the piezoelectric element 4 can be prevented from convexly bending upward or in a direction away from the carrier 2 due to the contraction of the polymer structural layer 6 in a static state. With the aid of the compensation layer 7, the neutral plane 14 (or neutral layer) of the piezoelectric element 4 can also be adjusted. The neutral plane 14 is a term in strength theory and / or stress theory, also known as a neutral line or zero line. The neutral line or neutral plane 14 or zero line is a plane or line where the tensile stress and the compressive stress in the piezoelectric element 4 offset each other and no longer generate stress. Otherwise, there is tensile stress or compressive stress above and below it. Of course, tensile stress or compressive stress only occurs when the piezoelectric element 4 is deflected. If the piezoelectric element 4 deflects, for example, upward (i.e., away from the carrier 2), compressive stress acts on the upper part of the piezoelectric element 4 and tensile stress acts on the lower part of the piezoelectric element 4. If, on the other hand, the piezoelectric element 4 is deflected downwards (i.e. towards the carrier 2), the compressive stress and the tensile stress are interchanged. There is neither tensile stress nor compressive stress in the neutral plane 14 or the neutral layer, which is arranged between the upper side and the lower side of the piezoelectric element 4. With the aid of the compensation layer 7, the position of the neutral line or the neutral plane 14 (or the neutral layer) or the zero line can be adjusted in the height or in the direction of the lifting axis 3. With the aid of the compensation layer 7, in particular the mechanical properties of the compensation layer 7, i.e. its mechanical stress, thickness, etc., the neutral plane 14 can be displaced in the direction of the lifting axis 3. The neutral plane 14 can be displaced or arranged in the direction of the upper side 15 of the piezoelectric element 4 or in the direction of the lower side 16 of the piezoelectric element 4. The lower side 16 of the piezoelectric element 4 faces the carrier 2. In contrast, the upper side 15 of the piezoelectric element 4 faces away from the carrier 2.

[0075] For example, the compensation layer 7 can be made of metal. The metal can be gold, for example. Additionally or alternatively, the compensation layer 7 can also be made of silicon dioxide, in particular TEOS. With such a material, the mechanical properties of the compensation layer 7 can be easily formed.

[0076] According to the present embodiment, the MEMS acoustic wave transducer 1 includes a coupling element 9 so that at least one piezoelectric element 4 can be coupled to the diaphragm 11 of the MEMS acoustic wave transducer 1. By means of the coupling element 9, when acoustic waves are generated by means of the diaphragm 11, the deflection of the piezoelectric element 4 can be transmitted to the diaphragm 11. Additionally or alternatively, when acoustic waves are detected by means of the diaphragm 11, the deflection of the diaphragm 11 can also be transmitted to the piezoelectric element 4.

[0077] Advantageously, as shown in the figure, a coupling plate 12 is arranged between the coupling element 9 and the diaphragm 11. With the help of the coupling plate 12, a planar transmission of the deflection between the coupling element 9 and the diaphragm 12 can be achieved. According to this embodiment, a diaphragm frame 13 is also shown so that the diaphragm 11 can be arranged on the carrier 2.

[0078] Furthermore, at least one piezoelectric element 4 has a length 33. Here, the length 33 is defined as from the carrier 2 to the free end 8 of the at least one piezoelectric element 4. The length 33 can be 0.5 mm to 2 mm. The structural layer 6 allows the piezoelectric element 4 to have this length 33, so that the runout can be increased along the lifting axis 3. The runout of the at least one piezoelectric element 4, in particular at its free end 8, can be at least 3%, preferably at least 10%.

[0079] The thickness 34 of the at least one piezoelectric element 4 may be 2 μm to 50 μm. The thickness 34 is parallel to the lifting axis 3 and / or perpendicular to the orientation of the layers of the at least one piezoelectric element 4 (see Figure 4 ). The local thickness of at least one compensation layer 7 can be 0.5 μm to 3 μm. If there are multiple compensation layers 7, such as Figure 4 As shown, the common local thickness of the multi-layer compensation layer 7 can be 0.5 μm to 3 μm.

[0080] Furthermore, at least one piezoelectric element 4 may have at least one notch 35 (not shown in the present figure). At least one notch 35 may extend at least partially between the upper side 15 and the lower side 16. At least one notch 35 may extend from the upper side 15 and / or from the lower side 16 in the direction of the opposite lower side 16 or upper side 15. With the aid of these notches 35, stresses in the piezoelectric element 4 or in at least one piezoelectric layer 5, in at least one structural layer 6 and / or in the compensation layer 7 may be reduced. Additionally or alternatively, the notch 35 extends in the direction of the lifting axis 3.

[0081] For the sake of brevity, features that are already described in at least one of the preceding figures are not described in detail. Otherwise, only features in this figure or in at least one of the succeeding figures are described. Also, for the sake of brevity, identical features are marked with identical reference numerals. Also, for the sake of clarity, not all features are shown and / or marked with reference numerals in the drawings. However, features shown in one or more of the preceding figures may also appear in one or more of the succeeding figures. Also, for the sake of clarity, features may only be shown and / or marked with reference numerals in this figure or in one or more of the succeeding figures. However, features shown in one or more of the succeeding figures may also already exist in this figure or in the preceding figures.

[0082] Figure 2 A schematic side view of a MEMS acoustic wave transducer 1 having two piezoelectric elements 4, 17 is shown. As mentioned above, all features are not repeated here. For example, Figure 1 The features of the first piezoelectric element 4 have already been described in . Advantageously, the two piezoelectric elements 4 , 17 shown in this figure are of identical design to each other. Therefore, the second piezoelectric element 17 has the same features as the first piezoelectric element 4 .

[0083] It can also be seen in the figure that the two piezoelectric elements 4 and 17 are coupled to the diaphragm 11 via a single coupling element 9. In addition, the first spring element 10 is arranged between the first piezoelectric element 4 and the coupling element 9, and the second spring element 18 is arranged between the second piezoelectric element 17 and the coupling element 9. Both piezoelectric elements 4 and 17 deflect the diaphragm 11 via the coupling element 9 shown in this figure. Additionally or alternatively, the deflection of the diaphragm 11 can also be transmitted to the piezoelectric elements 4 and 17 via the coupling element 9.

[0084] Figure 3 A MEMS acoustic wave transducer 1 is shown having two piezoelectric elements 4, 17 and two coupling elements 9, 19. Here again, individual features which are already apparent from at least one of the preceding figures will not be described in detail.

[0085] As shown in this embodiment, the first piezoelectric element 4 is coupled to the diaphragm 11 via the first coupling element 9. A first spring element 10 is further arranged between the first coupling element 9 and the first piezoelectric element 4. Additionally or alternatively, a first coupling plate 12 is arranged between the first coupling element 9 and the diaphragm 11.

[0086] Furthermore, the second piezoelectric element 17 is coupled to the diaphragm 11 via a second coupling element 19. A second spring element layer 18 is arranged between the second piezoelectric element 17 and the second coupling element 19. A second coupling plate 20 is arranged between the second coupling element 19 and the diaphragm 11. According to the embodiment shown in the figure, the two piezoelectric elements 4, 17 can be coupled to the diaphragm 11 independently of each other to a certain extent.

[0087] As an alternative to the embodiment shown in this figure, the two coupling elements 9, 19 shown can be coupled to the diaphragm 11 via a single coupling plate 12, 20. For example, the two coupling plates 12, 20 shown in this figure can be combined into a single coupling plate 12, 20.

[0088] Figure 4 A schematic side cross-sectional view showing the layered structure of the MEMS acoustic wave transducer 1 is shown. Figure 4 Shows Figure 1 The schematic structure of the MEMS acoustic wave transducer 1 in FIG. 1 does not show the area to the right of the coupling element 9. This means that Figure 4 Not shown Figure 1 The right part of the carrier 2.

[0089] Figure 4 A building direction 21 is shown. The layers of the MEMS acoustic wave transducer 1 shown in this figure can be built along this building direction 21. It should also be noted here that the layers can be arranged over the entire width of the shown MEMS acoustic wave transducer 1. This means that the unshaded areas shown in this figure are created later.

[0090] The carrier 2 may extend along the entire width of the MEMS acoustic wave transducer 1 shown in the figure at the beginning of the process, and the first electrode layer 22 may be arranged on the carrier 2 according to the construction direction 21. In the further process, the first piezoelectric layer 5 may be formed on the first electrode layer 22. The second electrode layer 24 may be formed on the first piezoelectric layer 5. The second piezoelectric layer 25 may be formed on the second electrode layer 24. The third electrode layer 26 may be formed on the second piezoelectric layer 25. Figure 1 Only the first piezoelectric layer 5 is shown. Figure 4 25. The piezoelectric element 4 is shown in more detail in FIG. Advantageously, the piezoelectric element 4 can have multiple piezoelectric layers 5, 25. For example, the piezoelectric element 4 can have two to six piezoelectric layers 5, 25. In an advantageous embodiment of the present invention, the piezoelectric element 4 can have four piezoelectric layers 5, 25. The electrode layers 22, 24, 26 described here are used to transmit electrical signals to at least one piezoelectric layer 5, 25 and / or to transmit electrical signals away from at least one piezoelectric layer 5, 25.

[0091] According to the present embodiment, the coupling element 9 and the piezoelectric element 4 have the same layered structure. Therefore, the coupling element 9 includes a section of the carrier 2, the first electrode layer 22, the first piezoelectric layer 5, the second electrode layer 24, the second piezoelectric layer 25 and / or the third electrode layer 26. However, these layers in the coupling element 9 only have the function of constructing the coupling element 9. It is beneficial to the process that the coupling element 9 and the at least one piezoelectric element 4 have the same layered structure. In this way, the coupling element 9 and the at least one piezoelectric element 4 can be created at the same time. In a processing step after the coupling element 9 and the at least one piezoelectric element 4 are constructed, the two can be separated from each other, for example by etching.

[0092] Additionally, a first insulating layer 27 may be arranged. Furthermore, a contact layer 29 may be arranged in order to conduct electrical signals to and / or away from the at least one piezoelectric layer 5, 25. Additionally or alternatively, a second insulating layer 28 may also be formed. The at least one insulating layer 27, 28 serves to electrically insulate the electrical conductor (e.g., the contact layer and / or the at least one piezoelectric layer 5, 25).

[0093] After forming these layers, a first gap 30 can be formed, for example, by etching. The first gap 30 is used to separate the piezoelectric element 4 from the coupling element 9, allowing the piezoelectric element 4 to deflect, especially relative to the carrier 2. After forming the first gap 30, the piezoelectric element 4 and the coupling element 9 are coupled to each other by means of the first spring element 10.

[0094] At least one polymer structural layer 6 is formed on at least one piezoelectric layer 5, 25 and / or at least one electrode layer 22, 24, 26 shown. According to the present embodiment, a second structural layer 31 is arranged on the first structural layer 6. By means of such a multi-layer structural layer 6, 31, the thickness 34 of the resulting layer can be increased. The at least one structural layer 6, 31 can be laminated on the at least one piezoelectric layer 5, 25 and / or at least one electrode layer 22, 24, 26 and / or at least one insulating layer 27, 28 and / or at least one contact layer 29, for example, in the form of a diaphragm, in particular a polymer diaphragm. For example, the thickness 34 of the at least one structural layer 6, 31 is twice the thickness of the polymer diaphragm, and the polymer diaphragm can be laminated twice, thereby forming the double-layer structural layer 6, 31 shown in the present figure. The double-layer structural layer 6, 31 can be regarded as a single-layer structural layer 6, 31.

[0095] The present embodiment shows a double piezoelectric layer 5 , 25 . If the piezoelectric layer 5 , 25 is made of scandium aluminum nitrite, it is advantageous if at least one piezoelectric element 4 , 17 has two to six, in particular four, piezoelectric layers 5 , 25 .

[0096] After forming at least one structural layer 6, 31, a second gap 32 may be formed in the layer. Via the second gap 32, a connection may be formed with the contact layer 29 shown.

[0097] Figure 4 Also shown in FIG. 1 is a first spring element 10 . The first spring element 10 is formed by a first structural layer 6 and a second structural layer 31 .

[0098] Furthermore, the figure shows a compensation layer 7 which extends in the longitudinal direction of the piezoelectric element 4 from the carrier 2 to the spring element 10 .

[0099] Figure 4 The layers shown in FIG. 1 may be formed at least partially by a photolithography process.

[0100] Figure 5 Shows Figure 1 A top view of an embodiment of a MEMS acoustic wave transducer is shown in FIG. The top view is parallel to or along the direction of the lifting axis 3.

[0101] The present figure shows a total of six piezoelectric elements 4 , 17 , 36 , 37 , 38 , 39 , which are arranged in the form of a regular polygon (hexagon in the present figure).

[0102] According to the present embodiment, the piezoelectric elements 4, 17, 36, 37, 38, 39 are coupled to the coupling element 9 via spring elements 10, 18, 40, 41, 42, 43. The figure also shows six spring elements 10, 18, 40, 41, 42, 43. In addition, there is only one coupling element 9. Alternatively, there may be at least one additional coupling element, so that the piezoelectric elements 4, 17, 36, 37, 38, 39 can be coupled to the diaphragm 11 via multiple coupling elements.

[0103] Furthermore, the figure shows a recess 35. At least one piezoelectric element 4, 17, 36, 37, 38, 39 can have at least one recess 35. With the aid of the recess 35, mechanical properties, such as mechanical stress and / or movement properties, of the piezoelectric element 4, 17, 36, 37, 38, 39 can be adjusted. At least one recess 35 can extend in a piezoelectric layer, a structural layer and / or a compensation layer of the respective piezoelectric element 4, 17, 36, 37, 38, 39.

[0104] In addition, this figure also shows a cross section 44. For example, Figure 2 A cross-sectional view is shown along section 44. However, for example Figure 2 The notch 35 is not shown.

Claims

1. A MEMS acoustic wave transducer (1) for generating and / or detecting acoustic waves in the audible wavelength spectrum and / or in the ultrasonic range, comprising: Carrier (2); as well as At least one piezoelectric element (4, 17) is arranged on the carrier (2) and can be tilted along the lifting axis (3). The at least one piezoelectric element (4, 17) comprises at least one piezoelectric layer (5, 25) and at least one structural layer (6, 31), wherein the electrical signal and the deflection of the piezoelectric element (4) can be mutually converted via the at least one piezoelectric layer (5, 25), It is characterized in that The at least one piezoelectric layer (5, 25) is made of scandium aluminum nitrite.

2. The MEMS acoustic wave transducer according to claim 1, characterized in that: The at least one structural layer (6, 31) is a polymer structural layer (6, 31), in particular a structural layer made of polyamide.

3. The MEMS acoustic wave transducer according to claim 1 or 2, characterized in that: The piezoelectric element (4, 17) has a compensation layer (7) for equalizing the mechanical stress of the at least one structural layer (6, 31) and / or for stretching the at least one structural layer (6, 31).

4. The MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that In the direction of the lifting axis (3), the piezoelectric layer (5, 25) is arranged between the carrier (2) and the structural layer (6, 31).

5. The MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that The structural layer (6, 31) is arranged between the piezoelectric layer (5, 25) and the compensation layer (7).

6. The MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that The compensation layer (7) is made of metal, in particular gold and / or silicon dioxide, in particular TEOS; and / or the thickness (34) of the compensation layer (7) is 0.2 μm to 4 μm, in particular 0.5 μm to 3 μm, preferably 0.6 μm to 2 μm, more preferably 1 μm to 2 μm.

7. The MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that The length (33) of the piezoelectric element (4, 17) in its longitudinal direction, in particular from the carrier (2) to the free end (8) of the piezoelectric element (4, 17), is 0.5 mm to 2 mm.

8. The MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that The compensation layer (7) extends in the longitudinal direction of the piezoelectric element (4, 17) to the carrier (2) and / or the free end (8) of the piezoelectric element (4, 17).

9. The MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that The at least one piezoelectric element (4, 17) comprises a plurality of piezoelectric layers (5, 25), in particular 2 to 6 layers, preferably 4 layers; and / or The at least one piezoelectric element (4, 17) comprises at least one electrode layer (22, 24, 26); and / or The at least one piezoelectric element (4, 17) comprises at least one insulating layer (27, 28).

10. The MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that At least one piezoelectric element (4, 17) is formed by sandwiching a plurality of piezoelectric layers (5, 25) and electrode layers (22, 24, 26).

11. The MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that The MEMS acoustic wave transducer (1) comprises a coupling element (9, 19) to enable the at least one piezoelectric element (4, 17) to be coupled to the diaphragm (11).

12. The MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that The piezoelectric element (4, 17) and the coupling element (9, 19) are coupled to each other via at least one spring element (10, 18), wherein the at least one spring element (10, 18) is preferably arranged between the structural layer (6, 31) and the coupling element (9, 19) in the longitudinal direction of the piezoelectric element (4, 17).

13. A MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that The spring element (10, 18) is preferably formed exclusively from the structural layer (6, 31) and / or the polymer.

14. A MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that The piezoelectric element (4, 17) and the coupling element (9, 19) have the same layer structure.

15. A MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that The thickness of the structural layer (6, 31) is 10 μm to 50 μm.

16. A MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that The at least one piezoelectric element (4, 17) has at least one recess (35), wherein the recess is preferably arranged in the at least one piezoelectric layer (5, 25), in the at least one electrode layer (22, 24, 26), in the at least one insulating layer (27, 28), in the at least one structural layer (6) and / or in the at least one compensation layer (7).

17. A MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that The elastic modulus of the polymer structural layer (6, 31) is 2 GPa to 50 GPa, in particular 2 GPa to 5 GPa, preferably GPa3.5 to 4 GPa; and / or The tensile strength of the polymer structural layer (6, 31) is 70 MPa to 100 MPa, in particular 85 MPa to 95 MPa; and / or The polymer structural layer (6, 31) can form an elongation of 3% to 10%.

18. A MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that The mechanical stress of the compensation layer (7) is equal to or higher than the mechanical stress of the at least one structural layer (6, 31), wherein the mechanical stress of the compensation layer (7) offsets the mechanical stress of the at least one structural layer (6, 31).

19. A MEMS acoustic wave transducer according to any one of the preceding claims, characterized in that The mechanical stress state of the compensation layer (7) offsets and compensates for and / or balances the mechanical stress of the at least one structural layer (6, 31) and / or the at least one piezoelectric layer (5, 25), wherein the mechanical stress of the compensation layer (7) is preferably 50 MPa to 1000 MPa, in particular 240 MPa.

20. A method for producing a MEMS acoustic wave transducer (1), in particular for generating and / or detecting acoustic waves in the audible wavelength spectrum and / or in the ultrasonic range, the MEMS acoustic wave transducer preferably being constructed according to one or more of the preceding claims, in, At least one piezoelectric element (4, 17) is constructed on the carrier (2), and the at least one piezoelectric element (4, 17) includes at least one piezoelectric layer (5, 25) and at least one structural layer (6, 31) coupled thereto. It is characterized in that The at least one piezoelectric layer (5, 25) is made of scandium aluminum nitrite.

21. The method according to claim 20, characterized in that A polymer is arranged on the piezoelectric layer (5, 25) to form the at least one structural layer (6, 31).

22. The method according to claim 20 or 21, characterized in that The at least one piezoelectric element (4, 17) is formed from a plurality of piezoelectric layers (5, 25), in particular from two to six layers, especially four layers.

23. A method according to any one of the preceding claims, characterised in that The at least one piezoelectric element (4, 17) is formed by a plurality of piezoelectric layers (5, 25) and at least one electrode layer (22, 24, 26) in a sandwich manner.

24. A method according to any one of the preceding claims, characterised in that When forming the at least one piezoelectric element (4, 17), at least one insulating layer (27, 28) is arranged.

25. The method according to any one of the preceding claims, characterized in that The polymer structure layer (6, 31) is arranged on the side of the piezoelectric layer (5, 25) facing away from the carrier (2).

26. A method according to any one of the preceding claims, characterised in that After the piezoelectric layer (5, 25) and / or the coupling element (9, 19) are formed and / or after the carrier (2), the piezoelectric layer (5, 25) and / or the coupling element (9, 19) are post-processed, in particular separated from each other, in particular by etching, the polymer structure layer (6, 31) is arranged on the at least one piezoelectric layer (5, 25).

27. A method according to any one of the preceding claims, characterised in that The piezoelectric element (4, 17) and the coupling element (9, 19) are jointly formed in layers, which preferably takes place on the carrier (2).

28. A method according to any one of the preceding claims, characterised in that After the piezoelectric element (4, 17) and the coupling element (9, 19) have been constructed in layers, the piezoelectric element (4, 17) and the coupling element (9, 19) are at least partially separated from one another, in particular by etching.

29. A method according to any one of the preceding claims, characterised in that At least one polymer structural layer (6, 31) is laminated onto the piezoelectric layer (5, 25) and / or the coupling element (9, 19), in particular in the form of a polymer film, preferably a self-adhesive polymer film.

30. The method according to any one of the preceding claims, characterized in that The double layer is preferably arranged one above the other and / or is formed of the same or different polymer structural layers (6, 31).

31. A method according to any one of the preceding claims, characterised in that laminating the polymer structure layer (6, 31) at a temperature of 70°C to 90°C; and / or After lamination, a polymer curing step takes place, preferably at a temperature of 150° C. to 200° C. and / or for a duration of 0.5 to 2 hours.

32. A method according to any one of the preceding claims, characterised in that A compensation layer (7) is arranged on the structural layer (6, 31).

33. A method according to any one of the preceding claims, characterised in that The at least one polymer structural layer (6, 31) is post-processed.

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