Method for manufacturing a piezoelectric resonator and piezoelectric resonator

Abstract

A method for manufacturing a piezoelectric resonator is proposed, wherein the structure which can be vibrated is formed from a highly doped silicon functional layer, the method having the following steps: depositing a piezoelectric layer and forming a recess in a lateral region such that the silicon functional layer is exposed within the recess, forming a silicide layer on the surface of the silicon functional layer which is exposed within the recess. Forming a diffusion barrier layer on the silicide layer, depositing and structuring a first and a second metallization layer such that a feed line and two connection elements are formed, forming the structure which can be vibrated by structuring the silicon functional layer, wherein the silicon functional layer of the structure which can be vibrated is electrically contactable via the first connection element and forms an electrode of the lower part of the resonator, wherein the first metallization layer of the structure which can be vibrated is electrically contactable via the second connection element and forms an electrode of the upper part of the resonator.

Description

Technical Field

[0001] The present invention is based on a method for manufacturing a piezoelectric resonator, wherein the resonator’s vibratory structure is formed of a highly doped silicon functional layer, wherein the silicon functional layer is disposed on a substrate relative to a vertical direction and has a lateral main extension surface, the main extension surface having a first lateral region, a second lateral region and a third lateral region, wherein a cavity is disposed below the silicon functional layer in the first lateral region. Background Technology

[0002] Silicon-based piezoelectric MEMS resonators offer the advantages of high resonance sharpness and small form factor, as well as the ability to be fabricated as integrated components on silicon chips. Here, the actuator that generates the conversion from electrical signals to mechanical vibrations is typically a piezoelectric layer, which is arranged as part of a sandwich structure between two electrodes and undergoes elastic deformation under the influence of the field generated by the electrodes.

[0003] For example, such silicon resonators are known from the publication "Experimental study of the effects of size variations on piezoelectrically transduced MEMS resonators" by Jaakkola et al. (IEEE International Symposium on Frequency Control, Newport Beach, CA, 2010, pp. 410-414). The resonator studied here consists of a square plate made of highly p-doped single-crystal silicon, which is bound to the substrate at the corners by flexible anchors. Electromechanical coupling is achieved through a layer of aluminum nitride (AlN) deposited on the plate. A molybdenum layer disposed on this piezoelectric layer acts as the upper electrode, while the lower electrode is formed by the silicon plate itself. An alternating electric field can be applied to the AlN layer through the corresponding contact of the electrodes, through which different vibrational modes of the resonator can be excited, the shape and frequency of which are determined essentially by the geometry of the resonator and, in particular, by its lateral dimensions. Summary of the Invention

[0004] In this context, one objective of the present invention is to provide a cost-effective MEMS process for resonators with high-performance and miniaturized constructions having piezoelectric functional layers.

[0005] Compared to existing technologies, the method according to the present invention allows for cost-effective, highly parallel MEMS processes that achieve maximum overlap between the piezoelectric layer and the two electrodes, thus maximizing the electromechanical efficiency of the resonator, while simultaneously ensuring high conductivity of the wire-bonded connecting elements and feed lines. Here, the two soft metallization layers on the resonator, while maintaining high conductivity, do not lead to hardening, mechanical tension, or significant temperature-dependent tension. Furthermore, this method yields a resonator with very low scattering in the piezoelectric layer in terms of layer thickness, and exhibits very small overall structural variations from component to component.

[0006] The multilayer system produced and structured according to the method of the invention initially has at least one highly doped, especially p-doped, silicon functional layer arranged parallel to the substrate wafer. The lateral direction (i.e., the direction extending parallel to the main extension plane) and the direction extending perpendicular to the main extension plane are determined by the main extension plane of the silicon functional layer or the substrate; this direction is also referred to below as the vertical direction. The extension of each layer in the vertical direction is referred to as the thickness, and the relative positions of these layers are referred to as the "upper" and "lower". The formation steps according to the method of the invention are carried out in first, second, and third lateral regions, which are distinct from each other or spaced apart in the lateral direction. A resonant vibratory structure is formed in the first lateral region, a connection portion for the lower electrode is formed in the second region, and a connection portion for the upper electrode is formed in the third region. A first connecting element in the second region is connected to the underlying silicon layer via a groove in the piezoelectric layer, which is in turn connected to the structured silicon layer via anchoring of the vibratory structure, thus acting as the lower electrode. The second connecting element in the third region is connected to the first metallization layer on the vibrating structure via a feed wire, so that the first metallization layer can be contacted by the second connecting element and form an electrode for the upper part of the piezoelectric layer. It is also conceivable that the piezoelectric layer has two or more grooves, which may be constructed in a manner similar to the first groove.

[0007] In the first region, a cavity is arranged beneath the silicon functional layer, which is formed, in particular, by etching the substrate or a sacrificial layer. Here, material is removed from the entire surface of the first lateral region, thus exposing the region downwards. In the second and third regions, preferably, at least one dielectric layer is arranged between the substrate and the silicon functional layer, the at least one dielectric layer electrically insulating the two layers from each other and / or the at least one dielectric layer serving as an etching mask for the cavity.

[0008] After depositing the piezoelectric layer, a sacrificial layer is deposited, particularly a sacrificial layer made of silicon oxide. The necessary over-etching of the metallization layer at the contacts in the sacrificial layer is then carried out via the sacrificial layer. This avoids material stripping of the piezoelectric layer, which would lead to undesirable changes in layer thickness. The sacrificial layer, made of oxide, can be removed, in particular, by vapor-phase hydrofluoric acid etching, by chemical-physical dry etching, or by etching with an aqueous hydrofluoric acid solution. A groove is then formed in the sacrificial and piezoelectric layers, through which the silicon functional layer is exposed on the inner surface of the groove (contact hole). To increase the electrical contact between the silicon layer and the subsequently deposited metallization layer, a silicide layer is first formed. To prevent metal diffusion into the silicon layer, a diffusion inhibition layer is deposited after silicide formation. It is preferable to selectively remove the silicide layer and the barrier layer (Barriere-Schicht) around the groove, as these involve rigid, mechanically tensioned layers that are not permitted on the resonator structure. Two metallization layers are then deposited. The first and second metallization layers can, for example, consist primarily, substantially, or entirely of gold, respectively. Here, the second metallization layer is particularly thicker than the first metallization layer.

[0009] In the subsequent structuring of the first lateral region (through which the vibratory structure is exposed in the lateral direction), one, two, or more anchors are formed, through which the silicon layer of the vibratory structure is connected to the silicon layer of the second region and preferably also to the silicon layer of the third region. In the resonator manufactured by means of the method according to the invention, the silicon functional layer of the vibratory structure fulfills a dual function. On the one hand, it forms a vibrator for exciting resonator modes; on the other hand, it acts as an electrode at the lower part of the piezoelectric layer disposed on the silicon layer.

[0010] Advantageous configurations and extensions of the invention are derived in the following description, with reference to the accompanying drawings.

[0011] According to one preferred embodiment, the piezoelectric layer has aluminum nitride. According to another embodiment, the silicide layer has platinum and nickel. According to another embodiment, the diffusion barrier layer has tantalum and tantalum nitride. According to another preferred embodiment, the first and second metallization layers (7, 8) have gold, wherein the first metallization layer (7) is particularly composed of a layer sequence of a thin tantalum layer, a platinum layer, a gold layer, another platinum layer, and another thin tantalum layer, wherein the second metallization layer (8) is particularly composed of a sequence of tantalum layers and gold layers. The silicide layer is preferably formed in combination of platinum and nickel. These two materials are good silizidbildners, and nickel, in addition, has excellent adhesion not only to the oxide surface but also to the AlN sidewalls of the groove. For the specific requirements of the metal-silicon contact, the targeted and mutually coordinated material combination described above has proven to be optimal for the silicide layer and the barrier layer. By combining according to the invention, good electrical contact is created, and effective suppression of gold diffusion is achieved, resulting in good adhesion to the oxide and a low layer thickness. Furthermore, in subsequent processes (e.g., wafer bonding), excellent stability of the electrical contacts and excellent stability of the barrier against thermal stress are achieved. The silicide layer can be nickel platinum silicide (NiPtSi) or composed of nickel platinum silicide. Preferably, the barrier layer is composed of tantalum and tantalum nitride. Preferably, the first metallization layer consists of a tantalum / platinum / gold / platinum / tantalum layer sequence. Here, these two thin tantalum layers are adhesion layers to the underlying aluminum nitride and to the layers above it (especially the first mask layer). The second metallization layer preferably consists of a single layer of tantalum followed by a thick gold layer.

[0012] According to a preferred embodiment, prior to depositing the piezoelectric layer, an oxide sub-region of the silicon functional layer is formed in the third lateral region, wherein a second connection element is formed above the oxide sub-region such that the second connection element is shielded downward through the oxide sub-region. The oxide sub-region thus advantageously reduces or suppresses parasitic capacitance.

[0013] Preferably, the oxide sub-regions are formed by the following steps: isotropically etching the silicon functional layer, thermally oxidizing the silicon functional layer, and then wet chemically structuring the oxidized silicon functional layer such that the surfaces of the oxide sub-regions extend flush with the surfaces of the non-oxide sub-regions. After oxide formation, the oxide is wet chemically structurated such that it remains only in the formed grooves. Here, the interaction between the silicon etching depth and the oxide thickness is preferably selected such that the center of the subsequently formed second interconnect is flush with the surface of the silicon layer. Here, the interaction of the mask, the isotropic silicon etching and oxide etching, and the downward etching of the oxide mask are considered. Preferably, the selection is such that only a minimal surface shape (topographie) remains at the transition between silicon and oxide. This overhead for minimizing the surface shape advantageously achieves the production of the flattest possible surface for the key lithography techniques used in resonator structuring.

[0014] According to a preferred embodiment, the deposition and structuring of the first and second metallization layers are performed in the first lateral region such that the first metallization layer completely covers the surface of the piezoelectric layer, and the second metallization layer is structured such that it covers one sub-region of the first metallization layer but not another sub-region. The sub-region covered by the second metallization layer significantly increases the conductivity of the arrangement formed by the first and second metallization layers. Preferably, the second metallization layer is arranged only in those regions on a vibrating structure where vibrational behavior is relatively insignificant. However, it is also conceivable that these elements can generate additional mass occupancy and / or local hardening of the resonator, by which unwanted vibrational modes can be suppressed, for example.

[0015] According to a preferred embodiment, the structuring of the second metallization layer is performed through the following steps: depositing a first mask layer; performing chemical-physical dry etching on the first mask layer, wherein the first mask layer is only partially etched in the vertical direction; and etching the first mask layer, wherein the first mask layer is completely etched in the vertical direction, wherein the etching of the first mask layer is performed by hydrofluoric acid vapor phase etching, chemical-physical dry etching, or etching with an aqueous hydrofluoric acid solution. The first mask layer is preferably an oxide layer. The structuring of the mask layer is performed in two stages to selectively terminate etching on the first metallization layer. Thus, the mask layer is partially etched in the first sub-step and completely etched in the second sub-step in a selective manner by means of hydrofluoric acid vapor phase etching, chemical-physical dry etching, or etching with an aqueous hydrofluoric acid solution, up to the first metallization layer. Preferably, the second metal layer is deposited as a layer sequence of tantalum and a thicker gold layer, and structuring is stopped in a sacrificial oxide.

[0016] According to a preferred embodiment, the formation of the vibratory structure is achieved by depositing and structuring a second mask layer, wherein, during etching, the first metallization layer, piezoelectric layer, and silicon functional layer are completely etched away in the vertical direction outside the etch mask defined by the second mask layer. The second mask layer is preferably also an oxide layer. The thickness of the second mask layer preferably depends on the oxide etch during aluminum nitride and silicon etching. Here, a photolithography step is used to structure the entire layer stack in a first region: an oxide hard mask, thin gold electrodes, aluminum nitride, and silicon functional layer. This advantageously results in maximum overlap between the piezoelectric layer and the two electrodes, and thus maximum electromechanical efficiency of the resonator. Another advantage obtained through the oxide hard mask is the steeper etch angle during aluminum nitride structuring and therefore better electrode overlap.

[0017] Preferably, the silicide layer is formed by the deposition of platinum and nickel followed by thermal silicide, wherein the thermal silicide is performed, particularly at a temperature of 250°C to 450°C.

[0018] Preferably, the structuring of the second metallization layer is performed by ion beam etching. Particularly preferably, the ion beam etching is performed at an angled incident angle, resulting in downward etching of the first and / or second mask layers.

[0019] According to a preferred embodiment, after deposition, the lateral variation in the thickness of the piezoelectric layer 3 is reduced by an ion beam trimming process.

[0020] Another subject of the present invention is a piezoelectric resonator manufactured by an embodiment of the method according to the invention. Attached Figure Description

[0021] Embodiments of the present invention are shown in the accompanying drawings and described in more detail in the following description.

[0022] Figure 1 A resonator manufactured using an embodiment of the method according to the invention is shown.

[0023] Figure 2 illustrates the steps of one embodiment of the method according to the present invention. Detailed Implementation

[0024] exist Figure 1 The image shows a cross-section (left) and a top view (right) of one embodiment of the resonator 1 according to the invention. The direction parallel to the main extension surface 10 of the device is also referred to hereinafter as the lateral direction, while the directions perpendicular to it are described by the terms "upper" and "lower". The resonator 1 has a vibrating structure 9, which consists of a silicon body with a centrally arranged groove 24. Formation 9. A vibratory structure 9 is arranged above a substrate wafer 15, in which cavities 4 have been etched to expose the resonator 1. The vibratory structure may include a single movable body 9 or multiple movable bodies 9. The body 9 is formed by a structured, highly doped silicon functional layer 2, which is mechanically connected to the substrate 15 outside the vibratory structure 9 via a dielectric layer 16. A piezoelectric aluminum nitride layer 3 is arranged on the vibratory structure 9, by means of which the body 9 can be excited to vibrate. The deformation of the piezoelectric layer 3 is driven by an electric field generated by two electrodes. The lower electrode is formed by the silicon layer 2 of the body 9 itself, while the upper electrode consists of a thin metallization layer 7, which consists of a tantalum / platinum / gold / platinum / tantalum layer sequence and is arranged on the piezoelectric layer 3 of the body 9. For electrical contact between the two electrodes, the surface of the component has two bonding pads 22 and 23. The first bonding pad is connected to the portion 17 of the silicon layer 2 below it via a metal-silicon contact 6, and is anchored to the vibrating structure 9 via it. The upper electrode, i.e., the gold layer 7, is connected to the second bonding pad 23 via a feed wire 21. A dielectric region 14 is arranged below the bonding pad 23 below the piezoelectric layer 3, which reduces the parasitic capacitance of the contact element 23. The bonding pads 22 and 23 and the feed wire 21 are formed by a thin metallization layer 7 and a thicker gold layer 8 disposed above it, respectively. Additionally, the vibrating structure 9 has a thicker structured layer 18 of gold layer 8 in mechanically non-critical areas to improve conductivity accordingly.

[0025] As in Figure 2a As shown, the starting point of the method according to the invention is a silicon layer 2 disposed on a wafer substrate 15, the wafer substrate having a buried cavity 4 for the resonator 1. Relative to the main extension surface 10 (see...) Figure 1 The three transverse regions 11, 12, and 13 can be distinguished. The cavity 4 is arranged in region 11, and a dielectric layer 16 is arranged between the substrate 15 and the functional layer 2 in regions 12 and 13. The dielectric layer 16 electrically insulates the silicon layer 2 from the substrate 15.

[0026] Then, as in Figure 2bAs shown, for the contact of the upper electrode, a dielectric oxide layer 14 is applied to reduce parasitic capacitance. For this purpose, an isotropic silicon etching is first performed. The wafer is then thermally oxidized, and the oxide is structured in a wet chemical manner such that it remains only in the groove. The interaction between the silicon etching depth and the oxide thickness is chosen such that the center of the pad 23 is flush with the surface of the silicon layer 2. Therefore, the interaction between the mask, the isotropic silicon etching, and the oxide etching, as well as the downward etching of the oxide mask, is chosen such that only a minimal surface shape remains at the transition from silicon 2 to oxide 14. This overhead for minimizing the surface shape is necessary to achieve the flattest possible surface for the key lithography technique used in resonator structuring.

[0027] As in Figure 2c As shown, a piezoelectric layer 3 made of aluminum nitride is then deposited. Since this piezoelectric layer forms the active layer for the resonator 1, the layer characteristics must be controlled very precisely to obtain a high-performance resonator 1 that is identical from component to component. An important parameter here is the layer thickness, where layer thickness fluctuations can advantageously be reduced by an ion beam trimming process after deposition.

[0028] Then, the metal-silicon contact 6 is manufactured. Figure 2d For this purpose, a sacrificial layer made of silicon oxide is first deposited. The aim here is to collect the metallization layer of contact 6 and the necessary over-etching in the sacrificial layer, rather than transferring it to the aluminum nitride layer 3, which is critical in terms of layer thickness variation. Then, the sacrificial layer and aluminum nitride 3 are structured up to silicon 2. After the contact hole is structured, silicides are deposited. The combination of platinum and nickel has proven to be particularly suitable for this. Thermal silicide is performed within a process window between 250°C and 450°C. Additionally, it is necessary to prevent gold from diffusing into silicon 2. For this purpose, a barrier layer consisting of tantalum and tantalum nitride is subsequently deposited. The silicide layer stack and the barrier stack represent a rigid, mechanically tensioned layer that is not allowed to appear on the resonator structure and is therefore removed around the contact hole 5. The oxide is removed very selectively relative to aluminum nitride by vapor-phase hydrofluoric acid etching, chemical-physical dry etching, or etching with an aqueous hydrofluoric acid solution. Here, the requirements for the silicide layer and the barrier are: good electrical contact, adhesion to oxides, prevention of gold diffusion into silicon, low layer thickness, stability against oxide etching, thermal stability of electrical contact, and thermal stability of the barrier against thermal stress in subsequent processes (such as wafer bonding).

[0029] Figure 2e The deposition and structuring of the thin metallization layer 7 are described. This metallization layer preferably consists of a layer sequence of tantalum / platinum / gold / platinum / tantalum. Two thin tantalum layers are attached here to the underlying aluminum nitride 3 and to the subsequent second sacrificial oxide layer 19 (see [link to documentation]). Figure 2f Since the resonator 1 and therefore the active aluminum nitride layer 3 are completely covered by a thin metallization layer 7, the metallization can be stopped directly in the adjacent non-critical aluminum nitride layer 3.

[0030] The structuring of the second metal layer 8 again requires the oxide sacrificial layer 19, because otherwise the second gold layer 8 cannot be selectively structured relative to the first gold layer 7. The structuring of the oxide sacrificial layer 19 is two-stage. Figure 2f In the first structuring step, dry chemical-physical etching is performed, although not the entire layer 19 is etched away. Then, in the second structuring step, material erosion is stopped very selectively at the thin gold layer 7 by means of hydrofluoric acid vapor phase etching. Alternatively, etching can also be performed by means of chemical-physical dry etching, especially reactive ion etching (RIE), or etching with hydrofluoric acid aqueous solution, wherein the etching process must be performed such that sufficient selectivity is given to the relatively thin gold layer 7. A second metal layer 8 consisting of tantalum and a thicker gold layer is then deposited and structurated to stop in the sacrificial oxide. For structuring, for example, ion beam etching can be advantageously used at an angled incident angle, thereby obtaining a downward etching of the paint mask. The process and layer thickness are chosen such that the surface shape of the resulting second metallized layer 8 advantageously compensates for the key photolithography techniques used for resonator structuring. This includes: the second metal layer 8 being embedded in the sacrificial oxide 19. This is achieved by selecting the layer thickness of the oxide layer 19, which matches the thickness of the second metal layer 8 and the etch erosion. Additionally, the edges of the oxide etching are strongly rounded. The structured interaction of the mask, the oxide sacrificial layer etching, and the second metal layer 8, as well as the downward etching of the metal mask 19, are chosen such that only a minimal surface shape remains at the transition from the sacrificial oxide to the second metal layer 8.

[0031] As in Figure 2g As shown, oxide layer 25 is deposited again, this time as a hard mask for resonator structuring. The layer thickness here depends on the oxide etch during aluminum nitride and silicon etching. A single photolithography step is used to perform the structuring of the entire layer stack: oxide hard mask 25, thin gold electrode 7, aluminum nitride 3, and silicon functional layer 2. This results in maximum overlap of piezoelectric layer 3 with the two electrodes for maximum electromechanical efficiency of resonator 1. Another advantage derived from oxide hard mask 25 is the steeper etch angle during aluminum nitride structuring, and therefore, better electrode overlap again.

[0032] Finally, sacrificial oxides 19 and 25 are removed by means of hydrofluoric acid vapor phase etching, dry chemical etching, or etching with hydrofluoric acid aqueous solution, and the process is completed. Figure 2hThe MEMS resonator 1 shown is shown in the figure.

Claims

1. A method for manufacturing a piezoelectric resonator (1), wherein, The vibratory structure (9) of the resonator (1) is formed of a highly doped silicon functional layer (2), wherein the silicon functional layer (2) is arranged above the substrate (15) relative to the vertical direction and has a lateral main extension surface (10), the main extension surface having a first lateral region, a second lateral region and a third lateral region (11, 12, 13), wherein a cavity (4) is arranged below the silicon functional layer (2) in the first lateral region (11), characterized in that the method has the following steps: - Deposit a piezoelectric layer (3) on the silicon functional layer (2). - A silicon oxide sacrificial layer is deposited on the piezoelectric layer (3), and - At least one groove (5) is formed in the second lateral region (12) such that the surface of the silicon functional layer (2) within the groove (5) is exposed, wherein the groove (5) extends in the vertical direction through the silicon oxide sacrificial layer and the piezoelectric layer (3). - A silicide layer is formed on the surface of the silicon functional layer (2) exposed within the groove (5). - A diffusion barrier layer is formed on the silicide layer. - Remove the silicon oxide sacrificial layer. - A first metallization layer and a second metallization layer (7, 8) are deposited and structured on the piezoelectric layer (3) and the diffusion barrier layer, wherein a feed line (21) is formed by the structuring of the first metallization layer and the second metallization layer (7, 8), the feed line conductively connecting the first lateral region and the third lateral region (11, 13), and a first connecting element (22) is formed in the second lateral region (12) and a second connecting element (23) is formed in the third lateral region (13) by the structuring. - The silicon functional layer (2) and the piezoelectric layer (3) are structured such that the vibrating structure (9) is formed in the first lateral region (11), wherein the silicon functional layer (2) of the vibrating structure (9) is electrically connected to the first connecting element (22) through the silicon functional layer (2) of the second lateral region (12), and forms the lower electrode of the resonator (1), wherein the lower electrode can make electrical contact through the first connecting element (22), wherein the first metallization layer (7) of the vibrating structure (9) can make electrical contact through the second connecting element (23), and forms the upper electrode of the resonator (1).

2. The method according to claim 1, wherein, The piezoelectric layer (3) has aluminum nitride.

3. The method according to claim 1 or 2, wherein, The silicide layer contains platinum and nickel.

4. The method according to claim 1 or 2, wherein, The diffusion barrier layer comprises tantalum and tantalum nitride.

5. The method according to claim 1 or 2, wherein, The first metallization layer and the second metallization layer (7, 8) are gold.

6. The method according to claim 5, wherein, The first metallization layer (7) consists of a layer sequence of tantalum layer, platinum layer, gold layer, another platinum layer and another tantalum layer.

7. The method according to claim 5, wherein, The second metallization layer (8) consists of a sequence of tantalum and gold layers.

8. The method according to claim 1 or 2, wherein, Before depositing the piezoelectric layer (3), an oxide sub-region (14) of the silicon functional layer (2) is formed in the third lateral region (13), wherein the second connection element (23) is formed above the oxide sub-region (14) such that the second connection element (23) is shielded downward through the oxide sub-region (14).

9. The method according to claim 8, wherein, The oxidized sub-region (14) is formed by the following steps: - Isotropically etch the silicon functional layer (2). - Thermal oxidation of the silicon functional layer (2). - The oxidized silicon functional layer (2) is chemically structured by wet process so that the surface of the oxidized sub-region (14) extends flush with the surface of the non-oxidized sub-region.

10. The method according to claim 1 or 2, wherein, The deposition and structuring of the first metallization layer and the second metallization layer (7, 8) are carried out in the first lateral region (11) such that the first metallization layer (7) completely covers the surface of the piezoelectric layer (3), and the second metallization layer (8) is structuring such that the second metallization layer covers one sub-region (18) of the first metallization layer (7) but does not cover the other sub-region of the first metallization layer (7).

11. The method according to claim 1 or 2, wherein, The structuring of the second metallization layer (8) is performed through the following steps: - Deposit the first mask layer (19). - The first mask layer (19) is subjected to chemical-physical dry etching, wherein the first mask layer (19) is only partially etched in the vertical direction. - The first mask layer (19) is etched, wherein the first mask layer (19) is completely etched in the vertical direction, wherein the etching of the first mask layer (19) is performed by hydrofluoric acid vapor phase etching, chemical-physical dry etching or hydrofluoric acid aqueous solution etching.

12. The method according to claim 1 or 2, wherein, The vibratory structure (9) is formed by depositing and structuring a second mask layer (25), wherein, during etching, the first metallization layer (7), the piezoelectric layer (3) and the silicon functional layer (2) are completely etched in the vertical direction outside the etch mask defined by the second mask layer (25), wherein the etching of the second mask layer (25) is performed by hydrofluoric acid vapor phase etching, chemical-physical dry etching or by etching with hydrofluoric acid aqueous solution.

13. The method according to claim 1 or 2, wherein, The silicide layer is formed by the deposition of platinum and nickel followed by thermal silicide formation.

14. The method according to claim 13, wherein, The thermal siliconization is carried out at a temperature of 250°C to 450°C.

15. The method according to claim 1 or 2, wherein, The structuring of the second metallization layer (8) is performed by ion beam etching.

16. The method according to claim 1 or 2, wherein, After deposition, the lateral variation in the thickness of the piezoelectric layer (3) is reduced by an ion beam trimming process.

17. A piezoelectric resonator (1), said piezoelectric resonator being manufactured according to the method of claims 1 to 16.

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