MEMS transducer having at least metal layer and oxide layer

Abstract

The invention relates to a MEMS transducer (1), in particular a MEMS sound transducer unit, preferably for generating and / or detecting sound waves in the audible wavelength spectrum and / or ultrasound range, comprising a carrier (2) and at least one piezoelectric element (4) which is arranged on the carrier (2) and which can be deflected in the direction of a lifting axis (3), the piezoelectric element has at least one piezoelectric layer (5, 25, 35, 36) and at least one carrier layer (6), wherein an electrical signal and a deflection of the piezoelectric element (4) can be converted to each other by means of the at least one piezoelectric layer (5, 25, 35, 36). According to the invention, the carrier layer (6) comprises at least one metal layer (41-43) and at least one oxide layer (37-40). The invention further relates to the use of a structural layer (6) for a MEMS transducer (1) and to a method for producing said MEMS transducer (1).

Description

Technical Field

[0001] The present invention relates to a MEMS transducer, in particular a MEMS acoustic transducer unit, preferably for generating and / or detecting sound waves in the audible wavelength spectrum and / or in the ultrasonic range. The MEMS transducer has a carrier and at least one piezoelectric element arranged at the carrier and deflectable in the direction of a lift axis. The piezoelectric element has at least one piezoelectric layer and at least one carrier layer, wherein an electrical signal and a deflection of the piezoelectric element can be converted into each other by means of the at least one piezoelectric layer. Summary of the Invention

[0002] The object of the present invention is to create a powerful MEMS transducer.

[0003] This object is achieved by means of a MEMS transducer having the features of the independent claims, the use of a carrier layer for a MEMS transducer, and a method for manufacturing a MEMS sensor. Advantageous or preferred embodiments are each the subject matter of the dependent claims.

[0004] The present invention provides a MEMS transducer, preferably a MEMS acoustic transducer, in particular for generating and / or detecting sound waves in the audible wavelength spectrum and / or in the ultrasonic range. The MEMS transducer can be operated as a loudspeaker and / or a microphone and thus as a MEMS acoustic transducer.

[0005] The MEMS acoustic transducer includes a carrier.

[0006] Furthermore, the MEMS transducer includes at least one piezoelectric element arranged at the carrier and deflectable in the direction of a lift axis.

[0007] In addition, the at least one piezoelectric element has at least one piezoelectric layer and at least one carrier layer, wherein an electrical signal and a deflection of the piezoelectric element can be converted into each other by means of these piezoelectric layers.

[0008] Furthermore, the carrier layer includes at least one metal layer and at least one oxide layer.

[0009] Advantageously, the piezoelectric layer is composed of aluminum scandium nitride. These piezoelectric layers are very robust, which is particularly attributed to the scandium content, which can preferably be between 30% and 70%. It can be particularly advantageous if the scandium content is 30%, 40% or 50%.

[0010] Advantageously, the at least one piezoelectric layer is arranged above or below the carrier layer in the direction of the lift axis.

[0011] Equally advantageously, two piezoelectric layers are arranged below or above the carrier layer in the direction of the lift axis. Advantageously, the metal layer is an aluminum layer. Additionally or alternatively advantageously, the oxide layer is a silicon oxide layer. With these materials, the carrier layer can be constructed using known manufacturing methods, for example, methods used in semiconductor technology. Thus, the carrier layer can be manufactured in large quantities and / or very inexpensively. Further, the aluminum layer and the silicon oxide layer have similar E-moduli (elastic moduli) in the range of 70 GPa. Thus, the two layers have similar or almost identical deflection characteristics.

[0012] The at least one oxide layer and / or at least one metal layer further have the advantage that they are heat-resistant and even high-temperature resistant, for example, resistant to high temperatures up to 1200 °C - 1400 °C. Thus, the piezoelectric layer and / or the electrode layer can be applied by methods of semiconductor technology, for example, methods compatible with CMOS. For example, the piezoelectric layer and / or the electrode layer can be applied by chemical vapor deposition (CVD) methods.

[0013] Advantageously, the carrier layer includes several metal layers and several oxide layers. These metal layers and oxide layers can also be arranged and / or stacked alternately and overlappingly. Thereby, a sandwich structure of the carrier layer is formed. Such a carrier layer is thus a stack composed of multiple layers, preferably a stack composed of at least one metal layer and at least one, especially at least two oxide layers. The carrier layer can also be a structural layer in this case.

[0014] Advantageously, in the direction of the lift axis, the uppermost or lowermost layer is an oxide layer. When the carrier layer is constructed in layers with the at least one metal layer and at least two oxide layers, in the direction of the lift axis, the uppermost and / or lowermost layer is an oxide layer. The advantage of this is that the oxide layer, especially the silicon oxide layer, has the highest heat resistance. The piezoelectric layer and / or the electrode layer are applied on these oxide layers (which form both the uppermost and the lowermost layers), especially at higher temperatures. The oxide layer does not change at higher temperatures.

[0015] In addition, the oxide layer, especially the silicon oxide layer, can be processed simply. For example, the layer can be polished by a chemical-mechanical method. Such a method is called chemical mechanical polishing, also known as chemical mechanical planarization (CMP, English : “chemical mechanical polishing”, also known as “chemical mechanical planarization”). Thus, the oxide layer, especially the silicon oxide layer, can be made very flat and / or smooth.

[0016] Advantageously, the piezoelectric element has a length between 0.5 mm and 2 mm in its longitudinal direction, especially from the carrier to the free end of the piezoelectric element.

[0017] Advantageously, in the direction of the lifting axis, the at least one piezoelectric layer is arranged only on one side of the carrier layer. Additionally or alternatively advantageously, in the direction of the lifting axis, the at least one piezoelectric layer is arranged on one side of the carrier layer and there is no such at least one piezoelectric layer on its opposite side.

[0018] Advantageously, in the direction of the lifting axis, the at least one piezoelectric layer is arranged only and / or exclusively between the carrier and the carrier layer. Through the arrangement of the at least one piezoelectric layer only on one side of the carrier layer, the piezoelectric element can be manufactured simply and easily.

[0019] Advantageously, the at least one piezoelectric element comprises several piezoelectric layers, in particular between two and six, preferably four.

[0020] Advantageously, the at least one piezoelectric element comprises at least one electrode layer. By means of the at least one electrode layer, electrical signals can be exchanged, which cause the piezoelectric element to deflect and / or are formed when the piezoelectric element deflects.

[0021] Advantageously, the at least one piezoelectric element comprises at least one isolation layer.

[0022] Advantageously, the at least one piezoelectric element is configured to be sandwich-shaped and composed of several piezoelectric layers and electrode layers.

[0023] Advantageously, the MEMS acoustic transducer comprises a coupling element by means of which the at least one piezoelectric element can be coupled to the membrane.

[0024] Improved is that the piezoelectric element and the coupling element are coupled together by means of at least one elastic element, wherein the at least one elastic element is preferably arranged between the carrier layer and the coupling element in the longitudinal direction of the piezoelectric element.

[0025] Advantageously, the elastic element, preferably exclusively, is formed by the carrier layer. Thus, the elastic element can be constructed simply.

[0026] Advantageously, the elastic element is made of the polymer or a polymer, in particular polyamide. Additionally or alternatively, the elastic element has the mechanical properties of a polymer.

[0027] Beneficially, the piezoelectric element and the coupling element have the same layered structure as each other.

[0028] Improved is that the thickness of the carrier layer is between 5 µm and 100 µm. Preferably, the carrier layer has a thickness of less than 100 µm.

[0029] Further advantageously, the carrier layer has an E modulus (elastic modulus) between 40 GPa and 300 GPa.

[0030] Due to the above mechanical properties of the at least one carrier layer, the deflection can be increased and / or the piezoelectric element can be shortened with at least the same deflection or with an increased deflection.

[0031] Further advantageously, the piezoelectric element includes at least one compensation layer. This compensation layer can be arranged on the carrier layer and / or on the at least one piezoelectric layer. The carrier layer can be arranged between the compensation layer and the at least one piezoelectric layer. By means of the compensation layer, the neutral layer can be moved along the lift axis. Furthermore advantageously, the at least one piezoelectric layer is arranged between the carrier and the carrier layer in the direction of the lift axis.

[0032] Furthermore, the present invention provides a use of the carrier layer for a MEMS transducer. The MEMS transducer has at least one of the features described above and / or below herein. Additionally or alternatively, the carrier layer has at least one of the features described above and / or below herein. In particular, the carrier layer can include at least one metal layer, in particular an aluminum layer, and / or at least one oxide layer, in particular a silicon oxide layer, and can optionally include at least one additional feature associated therewith.

[0033] In addition, the present invention provides a method for manufacturing a MEMS transducer, preferably a MEMS acoustic transducer, in particular for generating and / or detecting sound waves in the audible wavelength spectrum and / or in the ultrasonic range. The method for manufacturing the MEMS transducer can be carried out such that the MEMS transducer is configured to have at least one of the features described above and / or hereinafter.

[0034] In this method, at least one piezoelectric element is constructed on the carrier, and the piezoelectric element includes at least two piezoelectric layers and at least one carrier layer coupled thereto.

[0035] Furthermore, in this method, the carrier layer is arranged between the at least two piezoelectric layers. Thereby, a symmetric structure of the piezoelectric element can be formed, particularly in the direction of the lift axis. Thus, advantageous deflection characteristics can be achieved. It is also beneficial to process the oxide layer, in particular the silicon oxide layer, by chemical mechanical polishing. Thereby, the oxide layer is made flat and / or smooth. Then, the at least one piezoelectric layer and / or the electrode layer are applied on the flat and / or smooth oxide layer.

[0036] Advantageously, the piezoelectric layer is constructed on the carrier layer by means of a semiconductor manufacturing method.

[0037] Furthermore, it is advantageous to deposit a piezoelectric layer on a carrier layer. In this case, the piezoelectric layer, at least the first piezoelectric layer, can also be deposited on an oxide layer. Then, all the other subsequent piezoelectric layers are deposited one by one.

[0038] Equally advantageously, the piezoelectric layer and / or the carrier layer are constructed on the carrier layer by means of chemical vapor deposition. Thereby, the method for constructing the piezoelectric layer and / or the electrode layer is easy to understand. In addition, such a method can be carried out particularly simply.

[0039] In this case, a method compatible with CMOS can be used to construct and / or in particular arrange a metal layer, an oxide layer, an electrode layer, and / or a piezoelectric layer on an existing layer.

[0040] It is further beneficial to remove at least one region, in particular by means of etching, after the piezoelectric layer and / or the carrier layer are constructed. By means of the method steps described herein, the piezoelectric layer and / or the carrier layer can be constructed layer by layer.

[0041] It is useful that the piezoelectric layer is composed of scandium aluminum nitride.

[0042] It is also advantageous that the at least one piezoelectric element is constructed with several piezoelectric layers, in particular between two and six, especially four. With several piezoelectric layers, the performance of the piezoelectric element can be improved.

[0043] It is further advantageous that the same number of piezoelectric layers are arranged above and below the carrier layer in the direction of the lift axis.

[0044] For example, it is advantageous that two piezoelectric layers are respectively arranged above and below the carrier layer in the direction of the lift axis, so that the piezoelectric element includes a total of four piezoelectric layers.

[0045] It is beneficial that the at least one piezoelectric element is constructed in a sandwich shape composed of several piezoelectric layers and at least one electrode layer.

[0046] These several piezoelectric layers and several electrode layers can be arranged alternately and overlappingly.

[0047] It is further advantageous to arrange at least one isolation layer when constructing the at least one piezoelectric element.

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

[0049] It is improved that when the carrier layer made of a polymer is arranged on the at least one piezoelectric layer after the piezoelectric layer and / or the coupling element are constructed and / or after the carrier, the piezoelectric layer, and / or the coupling element have undergone post-treatment, in particular post-treatment by means of etching, especially after being separated from each other.

[0050] Advantageously, the piezoelectric element and the coupling element are constructed together in a layered manner, which is preferably carried out on a carrier.

[0051] Advantageously, after the piezoelectric element and the coupling element are constructed in a layered manner, they are at least partially separated from each other, in particular by means of etching.

[0052] Furthermore, a method can be carried out in order to create the MEMS transducer as described in one or more of the above and / or below. Description of the Drawings

[0053] Other advantages of the present invention are described in the following embodiments. Among them: Figure 1 A schematic cross-sectional view of a MEMS transducer is shown, which has a piezoelectric element composed of two piezoelectric layers and at least one carrier layer; Figure 2 A schematic cross-sectional view of a piezoelectric element is shown, which has two piezoelectric layers and at least one carrier layer; Figure 3 A schematic cross-sectional view of a piezoelectric element is shown, which has two piezoelectric layers above and below the carrier layer in the direction of the lifting axis; and Figure 4 A schematic cross-sectional view of a carrier layer composed of a metal layer and an oxide layer is shown. Detailed Description of the Invention

[0054] Figure 1 A schematic cross-sectional view of a MEMS transducer 1 is shown. The MEMS transducer 1 can also be a MEMS acoustic transducer. By means of the MEMS acoustic transducer, for example, sound waves within the audible wavelength spectrum can be generated, so that it can be operated as a MEMS speaker. By means of the MEMS acoustic transducer, sound waves within the audible wavelength spectrum can be additionally or alternatively detected, so that it can be operated as a MEMS microphone. In addition, the MEMS acoustic transducer can be arranged, for example, in a smartphone to enable, for example, making a call or listening to music. The MEMS acoustic transducer can also be arranged, for example, in headphones. However, pressure can also be generated and / or detected by means of the MEMS transducer 1.

[0055] However, another application field of the MEMS acoustic transducer can also be the generation and / or detection of sound waves in the ultrasonic range. The MEMS acoustic transducer can be arranged, for example, in an ultrasonic sensor, such as a distance sensor.

[0056] In addition, the MEMS transducer 1 includes a carrier 2, which can form the basic framework of the MEMS transducer 1. The carrier 2 can, for example, include a semiconductor substrate, which can be fabricated in an etching process. The carrier 2 can, for example, be made of silicon and / or have the shape of a wafer. Two carriers 2 are shown in the current view. However, the carrier 2 can be configured as a frame such that, in the cross-sectional view shown here, two elements of the carrier 2 shown here are joined together. For example, the carrier 2 can be configured as rectangular in a top view. The top view can, for example, be oriented towards the lift axis 3, which will be described below. The top view can, for example, be parallel to the lift axis 3. For example, if the carrier 2 is configured as a frame, the at least one piezoelectric element 4 can face at least partially towards the interior of the carrier 2.

[0057] At least one piezoelectric element 4 is further arranged at the carrier 2. The at least one piezoelectric element 4 can additionally be coupled to the carrier 2. The at least one piezoelectric element 4 can be deflected along the shown lift axis 3. The at least one piezoelectric element 4 can hereby convert an electrical signal into a deflection such that the MEMS transducer 1 operates as a loudspeaker or can generate sound waves. Additionally or alternatively, a deflection can also be converted into an electrical signal by means of the at least one piezoelectric element 4 such that the MEMS transducer 1 can operate as a microphone or can detect sound waves. However, a pressure can also be generated by means of the deflection. Additionally or alternatively, a pressure can also be detected, since this causes a deflection of the at least one piezoelectric element 4.

[0058] The at least one piezoelectric element 4 includes a free end 8, which can be deflected along the lift axis 3.

[0059] The piezoelectric element 4 further includes at least one piezoelectric layer 5, 25, 35, 36. The at least two piezoelectric layers 5, 25, 35, 36 are made of a piezoelectric material. The at least one piezoelectric layer 5, 25, 35, 36 can convert an electrical signal into a deflection and / or convert a deflection into an electrical signal. The at least one piezoelectric layer 5, 25, 35, 36 can be made of scandium aluminum nitride (ScAlN).

[0060] Furthermore, the piezoelectric element 4 includes at least one carrier layer 6. The at least one carrier layer is coupled to the at least one piezoelectric layer 5, 25, 35, 36. The at least one piezoelectric layer 5, 25, 35, 36 is arranged here between the carrier 2 and the at least one carrier layer 6. By means of the at least one carrier layer 6, the at least one piezoelectric layer 5, 25, 35, 36 can be stabilized. Additionally, the at least one piezoelectric layer 5, 25, 35, 36 can be prevented from breaking during deflection by means of the at least one carrier layer 6. The at least one carrier layer 6 can also serve as a carrier layer for the at least one piezoelectric layer 5, 25, 35, 36. In Figure 1 the present embodiment, the first piezoelectric layer 5 is shown.

[0061] The carrier layer 6 further comprises at least one metal layer 41-43 and at least one oxide layer 37-40, as shown in more detail in Figure 4 as shown. The at least one piezoelectric layer 5, 25, 35, 36 is further arranged only on one side of the carrier layer 6. According to this embodiment, the at least one piezoelectric layer 5, 25, 35, 36 is arranged between the carrier 2 and the carrier layer 6 in the direction of the lifting axis 3. Alternatively, the at least one piezoelectric layer 5, 25, 35, 36 can also be arranged on the side of the carrier layer 6 facing away from the carrier 2. Thus, in this alternative embodiment, the carrier layer 6 is arranged between the carrier 2 and the at least one piezoelectric layer 5, 25, 35, 36 in the direction of the lifting axis 3.

[0062] According to this embodiment, the MEMS transducer 1 comprises a coupling element 9, by means of which the at least one piezoelectric element 4 can be coupled to the membrane 11 shown here of the MEMS transducer 1. By means of the coupling element 9, if the MEMS transducer 1 is a MEMS acoustic transducer, when acoustic waves are generated by means of the membrane 11, the deflection of the piezoelectric element 4 can be transmitted to the membrane 11. Additionally or alternatively, if the MEMS transducer 1 is a MEMS acoustic transducer, when acoustic waves are detected by means of the membrane 11, the deflection of the membrane 11 can also be transmitted to the piezoelectric element 4.

[0063] According to this embodiment, the piezoelectric element 4 is coupled to the coupling element 9 by means of an elastic element 10. The elastic element 10 can be made of a polymer, for example. The elastic element 10 is thus flexible. Advantageously, as shown here, a coupling plate 12 is arranged between the coupling element 9 and the membrane 11. By means of the coupling plate 12, planar transmission of the deflection between the coupling element 9 and the membrane 12 can be achieved. According to this embodiment, a membrane frame 13 is also shown, by means of which the membrane 11 can be arranged on the carrier 2.

[0064] Furthermore, the at least one piezoelectric element 4 has a length 33. The length 33 is defined here as the distance from the carrier 2 to the free end 8 of the at least one piezoelectric element 4. The length 33 can be between 0.5 mm and 2 mm. By means of the carrier layer 6, the piezoelectric element 4 can have a length 33, where large deflections along the lifting axis 3 are possible. The deflection of the at least one piezoelectric element 4, especially at the free end 8, can be at least 3%, preferably at least 10%. The thickness 34 of the at least one piezoelectric element 4 can be between 2 μm and 50 μm. The thickness 34 is oriented parallel to the lifting axis 3 and / or perpendicular to the layer of the at least one piezoelectric element 4 (see Figure 4 ). Furthermore, the at least one piezoelectric element 4 may have at least one notch not shown in this figure. The at least one notch may extend at least partially between the upper side 15 and the lower side 16. The at least one notch may extend from the upper side 15 and / or from the lower side 16 in the direction of the corresponding opposite upper side or lower side 15, 16. By means of these notches, the stress in the piezoelectric element 4 or in the at least one piezoelectric layer 5, 25, 35, 36 and / or in the at least one carrier layer 6 can be reduced.

[0065] The upper side 15 faces the membrane 11 here. The lower side 16 faces away from the membrane 11. By means of the terms "upper side 15" and "lower side 16", the terms "above" and "below" are also defined. "Upper side 15" and "lower side 16" and "above" and "below" refer to the direction of the lifting axis 3.

[0066] Furthermore, the neutral layer 14 is shown here. The neutral layer 14 is a concept in strength theory and is also referred to as the neutral fiber (neutraler Faser) or the zero line (Nulllinie). The neutral line or the neutral layer 14 or the zero line is here a plane or a line in the piezoelectric element 4, where the tensile stress and the compressive stress cancel each other out, so that there is no stress there. Instead, above and below it, either tensile stress or compressive stress acts. Of course, the tensile stress or the compressive stress only occurs in this case when the piezoelectric element 4 is deflected. For example, if the piezoelectric element 4 is deflected upwards, i.e., away from the carrier 2, then compressive stress acts in the upper region of the piezoelectric element 4 and tensile stress acts in the lower region of the piezoelectric element 4. Conversely, if the piezoelectric element 4 is deflected downwards, i.e., towards the carrier 2, the compressive stress and the tensile stress are swapped. In the neutral layer 14 or in the neutral plane, there is neither tensile stress nor compressive stress, where the central layer 14 or the neutral plane is arranged between the upper side 15 and the lower side 16 of the piezoelectric element 4. By means of the first piezoelectric layer 5 and the second piezoelectric layer 25 above and below the carrier layer 6 in the direction of the lifting axis 3, the position of the neutral line or the neutral layer 14 (or plane) or the zero line is adjusted in height or in the direction of the lifting axis 3. Since the two piezoelectric layers 5, 25, 35, 36 are also configured to be the same as each other, i.e., made of the same material (e.g., AlScN) and / or have the same thickness 34, the neutral layer 14 is arranged in the middle of the piezoelectric element 4 and / or the carrier layer 6.

[0067] The MEMS transducer 1 shown here only has one piezoelectric element 4. Alternatively, the MEMS transducer 1 may also have several piezoelectric elements 4, which are coupled to one or several membranes 11.

[0068] For the sake of simplicity, features that have been described in at least one of the preceding figures may not be explained again. Additionally, features may also be described in at least one of this figure or subsequent figures. Further, for the sake of simplicity, the same reference signs are used for the same features. Moreover, for the sake of clarity, not all features may be shown and / or labeled with reference signs in the subsequent figures. However, features shown in one or more of the preceding figures may also be present in one or more of this figure or subsequent figures. Additionally, for the sake of clarity, features may also be shown and / or labeled with reference signs in this figure or subsequent figures. Nevertheless, features shown only in one or more of the subsequent figures may also have been present in this figure or the preceding figures.

[0069] Figure 2 Shows a detailed schematic cross-sectional view of the piezoelectric element 4. For the sake of clarity, a more detailed structure of the piezoelectric element 4 is set forth in Figure 2 the following.

[0070] Here, at least two piezoelectric layers 5, 25 are shown, both of which are arranged on one side of the carrier layer 6.

[0071] Additionally, several electrode layers 22, 23, 26 are shown here. In this embodiment, three electrode layers 22, 23, 26 are shown. By means of the electrode layers 22, 23, 26, electrical signals can be supplied to the two piezoelectric layers 5, 25 so that they are deflected, or electrical signals can be derived when they are deflected by themselves.

[0072] As can be seen here, the piezoelectric layers 5, 25 and the electrode layers 22, 23, 26 are arranged alternately and overlappingly. One piezoelectric layer 5, 25 is arranged between every two electrode layers 22, 23, 26.

[0073] Figure 3 Shows an embodiment of the piezoelectric element 4, which includes a carrier layer 6 and four piezoelectric layers 5, 25, 35, 36. Further, five electrode layers 22, 23, 26, 27, 28 are shown. The piezoelectric layers 5, 25, 35, 36 and the electrode layers 22, 23, 26, 27, 28 are again arranged alternately and overlappingly. The piezoelectric layers 5, 25, 35, 36 and the electrode layers 22, 23, 26, 27, 28 are arranged, in particular only, on one side of the carrier layer 6.

[0074] Figure 4An embodiment of the carrier layer 6 is shown by a sectional view. As can be seen here, the carrier layer 6 consists of further layers 37 - 43. The carrier layer 6 includes at least one oxide layer 37 - 40 and at least one metal layer 41 - 43. In particular, with the aid of the lifting shaft 3, it becomes clear again what "above" and "below" mean.

[0075] The at least one metal layer 41 - 43 can preferably be made of aluminum. Additionally or alternatively, the at least one oxide layer 37 - 40 can be made of silicon oxide. With these materials, the carrier layer 6 and the at least one piezoelectric layer 5, 25, 35, 36 arranged on the carrier layer can be constructed by means of known manufacturing methods, for example, methods used in semiconductor technology, such as CMOS-compatible methods.

[0076] The at least one oxide layer 37 - 40 and / or at least one metal layer 41 - 43 additionally have the advantage that they are heat-resistant or even high-temperature resistant, for example, resistant to high temperatures of up to 1200 °C - 1400 °C. Therefore, the piezoelectric layers 5, 25, 35, 36 and / or the electrode layers 22, 23, 26 - 29 can be applied by means of methods of semiconductor technology, such as CMOS-compatible methods. For example, the piezoelectric layers 5, 25, 35, 36 and / or the electrode layers 22, 23, 26 - 29 can be applied by means of chemical vapor deposition (CVD) methods.

[0077] In this embodiment, the carrier layer 6 includes four oxide layers 37 - 40 and three metal layers 41 - 43, as can be seen here, which are advantageously arranged overlappingly and alternately in the direction of the lifting shaft 3. Furthermore, in the direction of the lifting shaft 3, oxide layers 37, 40 are arranged above and below. The at least one piezoelectric layer 5, 25, 35, 36 can be arranged on the first or fourth oxide layer 37, 40 shown here. Advantageously, the at least one piezoelectric layer 5, 25, 35, 36 is arranged on the oxide layers 37 - 40 because the oxide layers 37 - 40 are temperature-resistant and easy to process. On the side where the piezoelectric layers 5, 25, 35, 36 are not arranged, the carrier layer 6 can end with a metal layer 41 - 43 or an oxide layer 37 - 40. Furthermore, adjacent to the electrode layers 22, 23, 26 - 29, there can also first be an oxide layer 37 - 40, and then the piezoelectric layer 5, 25, 35, 36 is adjacent to this oxide layer. However, this is only the case if an electrode for the piezoelectric layer 5, 25, 35, 36 is also configured as an electrode layer 22, 23, 26 - 29. The electrodes for the piezoelectric layer 5, 25, 35, 36 can also be arranged at the end faces of the piezoelectric layer 5, 25, 35, 36. At this time, the piezoelectric layer 5, 25, 35, 36 may be directly adjacent to the first or fourth oxide layer 37, 40.

[0078] Furthermore, the electrode layers 22, 23, 26 - 29 can also extend in sections between the piezoelectric layers 5, 25, 35, 36 and the adjacent oxide layers 37 - 40.

[0079] As shown here, the oxide layers 37 - 40 extend laterally beyond the metal layers 41 - 43. Additionally or alternatively, some of the oxide layers, in particular all of the oxide layers 37 - 40 and the metal layers 41 - 43, can also be flush and / or coincident.

[0080] As can be seen in Figure 4 the carrier layer 6 shown here includes four oxide layers 37 - 40 and three metal layers 41 - 43. Alternatively, the carrier layer 6 can also include only two or one oxide layer 37 - 40 and one metal layer 41 - 43. Further alternatively, the carrier layer 6 can also include several oxide layers 37 - 40, for example eleven, and several metal layers 41 - 43, for example ten.

[0081] Advantageously, the carrier layer 6 has oxide layers 37 - 40 above and below in the direction of the lift axis 6. Additionally, the uppermost and lowermost layers of the layered structure of the carrier layer 6 can be oxide layers 37 - 40. Additionally, metal layers 41 - 43 are respectively arranged between two oxide layers 37 - 40. Thus, the number of oxide layers 37 - 40 is one greater than the number of metal layers 41 - 43.

[0082] The oxide layers 37 - 40 have the advantage that they can be well further processed. For example, the oxide layers 37 - 40 can be processed by chemical mechanical polishing. Thus, a flat and / or smooth surface is formed on the oxide layers 37 - 40, and then the at least one piezoelectric layer 5, 25, 35, 36 and / or electrode layer 22, 23, 26 - 29 is arranged on this surface. Thus, it is advantageous that the uppermost and lowermost layers of the carrier layer are oxide layers 37 - 40.

[0083] Here there are four oxide layers 37 - 40 and three metal layers 41 - 43 in order to obtain a thickness 34 of the piezoelectric element 4 of approximately 7 µm, which is advantageous for the deflection and performance of the piezoelectric element 4. The number of oxide layers 37 - 40 and metal layers 41 - 43, and the thickness 34 of the piezoelectric element 4, also depend on the length 33 of the piezoelectric element 4 in this case.

[0084] List of reference signs 1 MEMS transducer 2 Carrier 3 Lift axis 4 Piezoelectric element 5 First piezoelectric layer 6 Carrier layer 8 Free end 9 Coupling element 10 Elastic element 11 Membrane 12 First coupling plate 13 Membrane frame 14 Neutral layer 15 Upper side 16 Lower side 22 First electrode layer 23 Second electrode layer 25 Second piezoelectric layer 26 Third electrode layer 27 Fourth electrode layer 28 Fifth electrode layer 33 Length 34 Thickness 35 Third piezoelectric layer 36 Fourth piezoelectric layer 37 First oxide layer 38 Second oxide layer 39 Third oxide layer 40 Fourth oxide layer 41 First metal layer 42 Second metal layer 43 Third metal layer

Claims

1. A MEMS transducer (1), in particular a MEMS acoustic transducer unit, preferably for generating and / or detecting acoustic waves in the audible wavelength spectrum and / or in the ultrasonic range, the MEMS transducer having Vector (2) and at least one piezoelectric element (4) arranged on the carrier (2) and capable of being deflected in the direction of the lifting axis (3), The piezoelectric element comprises at least one piezoelectric layer (5, 25, 35, 36) and at least one carrier layer (6), wherein an electrical signal and a deflection of the piezoelectric element (4) can be converted into one another by means of the at least one piezoelectric layer (5, 25, 35, 36). Features ， The carrier layer (6) comprises at least one metal layer (41-43) and at least one oxide layer (37-40).

2. MEMS transducer according to the preceding claim, Features The piezoelectric layer (5, 25, 35, 36) is composed of scandium aluminum nitride, wherein the scandium content is between 30% and 70%, preferably 30%, 40% or 50%.

3. MEMS transducer according to one or more of the preceding claims, Features , the metal layer (41-43) is an aluminum layer, and / or The oxide layer (37-40) is a silicon oxide layer.

4. MEMS transducer according to the preceding claim, Features The carrier layer (6) comprises several metal layers (41-43) and several oxide layers (37-40), which are preferably arranged and / or stacked in an alternating manner.

5. MEMS transducer according to one or more of the preceding claims, Features , the at least one piezoelectric layer (5, 25, 35, 36) is arranged on the oxide layer (37-40).

6. MEMS transducer according to one or more of the preceding claims, Features A piezoelectric layer (5, 25, 35, 36) is arranged below or above the carrier layer (6) in the direction of the lifting axis (3).

7. MEMS transducer according to one or more of the preceding claims, Features , the at least one piezoelectric layer (5, 25, 35, 36) is arranged only on one side of the carrier layer (6) in the direction of the lifting axis (3), and / or In the direction of the lifting axis (3), the at least one piezoelectric layer (5, 25, 35, 36) is arranged on one side of the carrier layer (6), and the at least one piezoelectric layer (5, 25, 35, 36) is not arranged on the opposite side of the carrier layer (6).

8. MEMS transducer according to one or more of the preceding claims, Features , in the direction of the lifting axis (3), the at least one piezoelectric layer (5, 25, 35, 36) is arranged only and / or exclusively between the carrier (2) and the carrier layer (6).

9. MEMS transducer according to one or more of the preceding claims, Features The piezoelectric element (4) has a length (33) in its longitudinal direction of between 0.5 mm and 2 mm, in particular from the carrier (2) to the free end (8) of the piezoelectric element (4).

10. MEMS transducer according to one or more of the preceding claims, Features , the at least one piezoelectric element (4) comprises several piezoelectric layers (5, 25, 35, 36), in particular between two and six, preferably four, and / or The at least one piezoelectric element (4) comprises at least one electrode layer (22, 23, 26-28), and / or The at least one piezoelectric element (4) comprises at least one isolation layer.

11. MEMS transducer according to one or more of the preceding claims, Features The MEMS transducer (1) comprises a coupling element (9), by means of which the at least one piezoelectric element (4) can be coupled to a membrane (11).

12. MEMS transducer according to one or more of the preceding claims, Features The piezoelectric element (4) and the coupling element (9) are coupled together by means of at least one elastic element (10), wherein the at least one elastic element (10) is arranged between the carrier layer (6) and the coupling element (9) in the longitudinal direction of the piezoelectric element (4).

13. MEMS transducer according to one or more of the preceding claims, Features The elastic element (10) is preferably formed exclusively by the carrier layer (6) and / or a polymer.

14. Use of a carrier layer (6) for a MEMS transducer (1), wherein the MEMS transducer (1) is formed at least as claimed in any one of the preceding claims and / or wherein the carrier layer (6) is formed as at least one of the claims.

15. A method for manufacturing a MEMS transducer (1), in particular a MEMS acoustic transducer unit, preferably for generating and / or detecting acoustic waves in the audible wavelength spectrum and / or in the ultrasonic range, The MEMS transducer (1) preferably has at least one feature of the above claims, At least one piezoelectric element (4) is arranged on the carrier (2) and is deflectable in the direction of the lifting axis (3). The piezoelectric element comprises at least two piezoelectric layers (5, 25, 35, 36) and at least one carrier layer (6), wherein an electrical signal and a deflection of the piezoelectric element (4) can be converted into one another by means of the at least two piezoelectric layers (5, 25, 35, 36). Features ， The carrier layer (6) is constructed as at least one metal layer (41-43) and at least one oxide layer (37-40).

16. The method according to the preceding claim, Features , the oxide layer (37-40), in particular the silicon oxide layer, of the carrier layer (6) is processed by chemical mechanical polishing.

17. The method according to one or more of the preceding claims, Features The piezoelectric layer (5, 25, 35, 36) is formed on the carrier layer (6) by means of a semiconductor manufacturing method.

18. The method according to one or more of the preceding claims, Features , the piezoelectric layer (5, 25, 35, 36) is deposited on the carrier layer (6), in particular on the oxide layer (37-40).

19. The method according to one or more of the preceding claims, Features The piezoelectric layer (5, 25, 35, 36) is formed on the carrier layer (6) by means of chemical vapor deposition and / or the carrier layer (6) is formed.

20. The method according to one or more of the preceding claims, Features After the piezoelectric layer (5, 25, 35, 36) and / or the carrier layer (6) has been formed, at least one region is removed, in particular by etching.

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