CN103532516B - Body wave resonator and its manufacture method - Google Patents

Abstract

The invention discloses a piezoelectric bulk wave resonator and a manufacturing method thereof, wherein the piezoelectric bulk wave resonator comprises: a multilayer structure; a substrate, the surface of the substrate has at least one groove, and the multilayer structure covers at least a groove through which at least one cavity is formed to constitute the acoustic reflection structure of the piezoelectric bulk wave resonator; wherein, in each cavity, the multilayer structure is depressed toward the bottom of the cavity and does not contact the bottom of the cavity contact; or, the multilayer structure protrudes away from the bottom of the cavity, and the height of the protrusion is greater than or equal to a predetermined height of the protrusion. The present invention ensures that the upper and lower sides of the multilayer film structure of the piezoelectric bulk wave resonator have good air reflection interfaces by controlling the degree of downward depression and the height of the upper protrusion of the multilayer film structure in the piezoelectric bulk wave resonator, In this way, good bulk acoustic wave reflection effect is ensured, and the Q value is kept at a high level.

Description

Bulk wave resonator and manufacturing method thereof

technical field

The present invention relates to the field of semiconductors, and in particular, to a piezoelectric bulk wave resonator and a manufacturing method thereof.

Background technique

The multilayer piezoelectric bulk wave resonator made by using the longitudinal resonance of the piezoelectric multilayer structure in the thickness direction has become a surface acoustic wave device and a quartz crystal resonator in mobile phone communication and high-speed serial data applications. a viable alternative. RF front-end bulk acoustic wave piezoelectric filter/duplexer provides superior filtering characteristics, such as low insertion loss, steep transition band, large power capacity, strong anti-electrostatic discharge (ESD) ability, etc.

The high-frequency multilayer film structure piezoelectric bulk wave oscillator has ultra-low frequency temperature drift, and its advantages are: low phase noise, low power consumption and large bandwidth modulation range. In addition, these miniature piezoelectric bulk wave resonators can use complementary metal-oxide-semiconductor (CMOS) compatible processing technology on silicon substrates to reduce the unit cost and facilitate the eventual integration with CMOS circuits.

A typical piezoelectric bulk wave resonator includes two metal electrodes, a piezoelectric material between the upper and lower electrodes, an acoustic reflective structure under the bottom electrode, and a substrate under the acoustic reflective structure. Generally, the area where the upper electrode, the piezoelectric layer, and the lower electrode three-layer materials overlap in the thickness direction is defined as the effective area of the resonator. When a voltage signal of a certain frequency is applied between the electrodes, due to the inverse piezoelectric effect of the piezoelectric material, sound waves propagating in the vertical direction will be generated between the upper and lower electrodes in the effective area, and the sound waves will travel at the interface between the upper electrode and the air. Reflect back and forth with the acoustic reflection structure under the bottom electrode and generate resonance at a certain frequency. The Q value is the ratio of the total energy stored by the resonator to the energy lost by the resonator due to various channels. The higher the acoustic reflection efficiency, the smaller the acoustic energy leaked from the resonator, that is, the higher the Q value of the resonator. The improvement of the Q value helps to improve the pass-stop band characteristics of the filter with the piezoelectric resonator as the basic unit, and can ensure the performance of the multilayer film structure piezoelectric filter.

In order to form a good reflection effect of the sound wave between the upper and lower electrodes, the effective area of the resonator is usually formed on a substrate with a cavity structure as shown in FIG. 1 . The multilayer piezoelectric bulk wave resonator shown in Figure 1 includes: two metal electrodes T and B, a piezoelectric material P between the upper and lower electrodes, a sacrificial layer PSG under the bottom electrode, and a sacrificial layer PSG Substrate S below. Since the acoustic impedance ratio between the air and the bottom electrode is very large, sound waves are reflected very well at the interface between the bottom electrode and the air. In order to ensure the least sound wave leakage, it is necessary to make the projection of the formed effective area in the vertical direction as possible as possible in the cavity area of the substrate.

The steps of a method for making a cavity acoustic reflection structure may include:

Step 1, etching a cavity structure on the substrate S;

Step 2, filling the cavity structure with a sacrificial layer material;

Step 3, making the bottom electrode B, the piezoelectric layer P, and the top electrode T on the substrate that has been planarized;

Step 4, removing the sacrificial layer to form a suspension structure.

After removing the sacrificial layer, in the piezoelectric bulk wave resonator shown in Figure 2, the multilayer film structure M (including the bottom electrode B, piezoelectric layer P and top electrode T) tends to be deformed. One deformation situation is: the multi-layer film structure M is depressed and is very close to or even in direct contact with the bottom C of the cavity structure. Since the reflection efficiency of the bulk acoustic wave in the contact between the bottom electrode and the substrate is much smaller than that at the interface between the bottom electrode and the air, the acoustic wave energy can leak out from the contact between the multilayer film structure and the substrate, and the bottom electrode and the bottom of the cavity The larger the contact area, the more serious the energy leakage. As a result, the Q value of the multilayer film structure resonator, especially the Q value at the parallel resonance frequency, decreases.

As shown in Figure 3, another deformation situation is: in the piezoelectric bulk wave resonator, the multilayer film structure M protrudes to the outside of the cavity. In this case, when the resonator and filter need to be covered and packaged When the wafer is used, the raised multilayer film structure is likely to be in contact with the packaging wafer (also known as the cover, Cap), which also cannot reflect the sound wave well, resulting in the multilayer film structure resonator. The Q value decreases. It is often difficult for the resonators and filters actually manufactured to achieve the performance they were designed for.

In a filter composed of a plurality of piezoelectric bulk wave resonators connected together, since resonators with different frequency impedance properties need to be used, it is usually necessary to arrange resonators with different effective area sizes together in the design. Under the same growth conditions of the multilayer film structure, the larger the cavity area, the easier the multilayer film structure is to deform. Or the packaging wafer contact, resulting in the overall performance of the filter can not meet the design requirements.

Aiming at the problem in the related art that the deformation of the multilayer film structure of the piezoelectric bulk wave resonator is too large, resulting in a decrease in the Q value of the piezoelectric bulk wave resonator, no effective solution has been proposed yet.

Contents of the invention

Aiming at the problem in the related art that the deformation degree of the multilayer film structure of the piezoelectric bulk wave resonator is too large, resulting in a decrease in the Q value of the piezoelectric bulk wave resonator, the present invention proposes a piezoelectric bulk wave resonator and a manufacturing method thereof , can control the degree of deformation of the multilayer film structure of the piezoelectric bulk wave resonator, thereby ensuring a good bulk acoustic wave reflection effect and keeping the Q value at a high level.

Technical scheme of the present invention is realized like this:

According to one aspect of the present invention, a piezoelectric bulk wave resonator is provided.

The piezoelectric bulk wave resonator consists of:

multi-layer structure;

A substrate, the surface of the substrate has at least one groove, the multilayer structure covers at least one groove, and the acoustic reflection structure of the piezoelectric bulk wave resonator is formed by at least one cavity formed;

Wherein, in each cavity, the multi-layer structure is recessed toward the bottom of the cavity, and does not contact the bottom of the cavity; or, the multi-layer structure protrudes away from the bottom of the cavity, and the height of the protrusion is Greater than or equal to the predetermined protrusion height.

And, in case the multilayer structure is recessed toward the bottom of the cavity, for each cavity, the minimum distance between the multilayer structure and the bottom of the cavity is greater than a predetermined distance.

Preferably, the aforementioned predetermined distance is 0.1 μm.

Preferably, the aforementioned predetermined protrusion height is 0.1 μm.

Further, in the opening plane of each groove, the ratio of the length of the longest straight line connecting two points on the edge of the opening of the groove to the diameter of the largest inscribed circle of the opening of the groove is greater than 1.

In addition, the above-mentioned multilayer structure includes a lower electrode, a piezoelectric layer covering the lower electrode, and an upper electrode covering the piezoelectric layer, wherein the upper electrode and the lower electrode do not overlap in areas other than the plurality of grooves.

Optionally, the shape of the opening of at least one groove includes: circular, polygonal, and irregular.

In addition, the above piezoelectric bulk wave resonator further includes:

a support, configured above the substrate;

The cover layer is supported by a support, and there is an interval between the raised multilayer structure and the cover layer.

According to one aspect of the present invention, a method for manufacturing a piezoelectric bulk wave resonator is provided.

The manufacturing method of the piezoelectric bulk wave resonator includes:

provide the substrate;

forming at least one groove on the substrate;

filling at least one groove with a sacrificial material;

forming a multilayer structure over the substrate, the multilayer structure covering the substrate and at least one groove;

removing the sacrificial material in the groove to form at least one cavity to form the acoustic reflection structure of the piezoelectric bulk wave resonator;

Wherein, at least one groove is formed by etching, and the depth of each groove is controlled by controlling the etching time, so as to prevent the multilayer structure from contacting the bottom of the cavity after the sacrificial material is removed;

Alternatively, the multi-layer structure protrudes away from the bottom of the cavity, and the height of the protrusion is greater than or equal to a predetermined height of the protrusion.

Wherein, the number of the above-mentioned grooves is multiple, and when at least one groove is formed on the substrate, by controlling the number and/or parameters of the formed grooves, the direction of the multilayer structure toward the groove after the sacrificial material is removed is controlled. The extent to which the bottom of the groove is recessed and avoids contact of the multilayer structure with the bottom of the cavity.

And, in case the multilayer structure is recessed toward the bottom of the cavity, for each cavity, the minimum distance between the multilayer structure and the bottom of the cavity is greater than a predetermined distance.

Preferably, the aforementioned predetermined distance is 0.1 μm.

Preferably, the aforementioned predetermined protrusion height is 0.1 μm.

Further, in the opening plane of each groove, the ratio of the length of the longest straight line connecting two points on the edge of the opening of the groove to the diameter of the largest inscribed circle of the opening of the groove is greater than 1.

Moreover, the multi-layer structure includes a lower electrode, a piezoelectric layer covering the lower electrode, and an upper electrode covering the piezoelectric layer, wherein the upper electrode and the lower electrode do not overlap in regions other than the plurality of grooves.

Optionally, the shape of the opening of at least one groove includes: circular, polygonal, and irregular.

In addition, the manufacturing method of the above-mentioned piezoelectric bulk wave resonator further includes:

disposing a support over the substrate prior to removing the sacrificial material in the groove;

removing the sacrificial material in the groove to form at least one cavity to form the acoustic reflection structure of the piezoelectric bulk wave resonator;

Wherein, by controlling the shape of the contact surface between the cavity and the multilayer structure, the multilayer structure is prevented from protruding upward beyond the height of the support after the sacrificial material is removed.

Moreover, the manufacturing method of the piezoelectric bulk wave resonator further includes:

disposing supports above the substrate;

A cover layer is provided, supported by a support, with a space between the raised multilayer structure and the cover layer in the case where the multilayer structure protrudes away from the bottom of the cavity.

The present invention ensures that the upper and lower sides of the multilayer film structure of the piezoelectric bulk wave resonator have good air reflection interfaces by controlling the degree of downward depression and the height of the upper protrusion of the multilayer film structure in the piezoelectric bulk wave resonator, In this way, good bulk acoustic wave reflection effect is ensured, and the Q value is kept at a high level.

Description of drawings

1 is a schematic diagram of a piezoelectric bulk wave resonator in the prior art;

2 is a schematic diagram of a piezoelectric bulk wave resonator in the prior art when the multilayer film structure is in contact with the bottom of the cavity;

3 is a schematic diagram of a piezoelectric bulk wave resonator in the prior art when the multilayer film structure is in contact with the surface of the upper package crystal;

4 is a schematic diagram of a piezoelectric bulk wave resonator according to an embodiment of the present invention when the multilayer structure is recessed downward;

5 is a structural diagram of a piezoelectric bulk wave resonator according to an embodiment of the present invention when the multilayer structure is convex upward;

6 is a schematic diagram of a polygonal shape of a groove surface defined by a piezoelectric bulk wave resonator according to an embodiment of the present invention;

7 is a schematic diagram of changing the polygonal shape of the groove surface of the piezoelectric bulk wave resonator according to an embodiment of the present invention;

Fig. 8a is a top view of a piezoelectric bulk wave resonator according to yet another embodiment of the present invention;

Fig. 8b is a cross-sectional view taken along the section line A-A of the piezoelectric bulk wave resonator shown in Fig. 8a;

Fig. 8c is a sectional view taken along the section line N-N of the piezoelectric bulk wave resonator shown in Fig. 8a;

Fig. 9a is a top view of a piezoelectric bulk wave resonator according to yet another embodiment of the present invention;

Fig. 9b is a cross-sectional view taken along the section line A-A of the piezoelectric bulk wave resonator shown in Fig. 9a;

Fig. 9c is a cross-sectional view taken along the section line N-N of the piezoelectric bulk wave resonator shown in Fig. 9a.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention belong to the protection scope of the present invention.

According to an embodiment of the present invention, a piezoelectric bulk wave resonator is provided.

A piezoelectric bulk wave resonator according to an embodiment of the present invention may include:

A multilayer structure, wherein the multilayer structure includes a bottom electrode, a piezoelectric layer, and an upper electrode;

A substrate, the surface of the substrate has at least one groove, the multilayer structure covers at least one groove, and the acoustic reflection structure of the piezoelectric bulk wave resonator is formed by at least one cavity formed;

Wherein, in each cavity, the multilayer structure is recessed toward the bottom of the cavity and does not contact the bottom of the cavity. Also, for each cavity, the minimum distance between the multilayer structure and the bottom of the cavity is greater than a predetermined distance. In order to avoid the acoustic wave energy of the bulk acoustic wave resonator from being coupled to the substrate through the air, the minimum distance between the multilayer film structure and the bottom of the cavity should be at least greater than a quarter of the wavelength of the resonant acoustic wave in the air. Therefore, preferably, the predetermined distance can be 0.1 μm.

As shown in Figure 4 and Figure 5, the piezoelectric bulk wave resonator structure according to the embodiment of the present invention includes: a substrate S, a cavity C, a bottom electrode B, a piezoelectric layer P, and an upper electrode T, wherein the bottom electrode B , The area where the piezoelectric layer P and the upper electrode T overlap in the vertical direction is defined as the effective area of the piezoelectric bulk wave resonator, and the composite film structure composed of all films on the cavity area is defined as the multilayer film structure M.

In practical application, as shown in FIG. 4 , it is a schematic diagram of a piezoelectric bulk wave resonator according to an embodiment of the present invention when the multilayer structure is recessed downward. At this time, the multilayer film structure is recessed downward, and the multilayer film The structure is not in contact with the bottom of the cavity. By controlling the depth of the cavity or the process parameters for growing the multilayer film structure, the multilayer film structure is not in contact with the bottom of the cavity. The maximum distance between the bottom electrode B and the bottom of the cavity is Dp. Preferably, the minimum distance between the lowest point of the depression of the multilayer film structure and the bottom of the cavity should be greater than 0.1 μm.

For example, the surface profile of the multilayer film M can be drawn on the surface of the multilayer film M with a step meter, and the maximum depth Ld of the depression of the multilayer film structure can be obtained by calculating the lowest point of the curve. By controlling the etching time of the cavity when preparing the substrate, the depth Dp of the cavity can be controlled, thereby controlling the vertical distance (Dp-Ld) between the lowest point of the depression of the multilayer film structure and the bottom of the cavity (Dp-Ld), so that the distance is greater than 0.1 μm. In this way, the sound wave can be well reflected in the overlapping range of the effective area and the cavity area, and at the same time, a certain area is reserved for the further deformation of the multilayer film structure due to environmental changes (such as temperature changes or impact forces), avoiding the The acoustic wave of the resonator leaks in the cavity area and causes the Q value to decrease.

According to another embodiment of the present invention, a piezoelectric bulk wave resonator is provided.

A piezoelectric bulk wave resonator according to an embodiment of the present invention may include:

multi-layer structure;

A substrate, the surface of the substrate has at least one groove, the multilayer structure covers at least one groove, and the acoustic reflection structure of the piezoelectric bulk wave resonator is formed by at least one cavity formed;

Wherein, in each cavity, the multi-layer structure protrudes away from the bottom of the cavity, and the height of the protrusion is greater than or equal to a predetermined height of the protrusion. Optionally, the aforementioned predetermined protrusion height may also be 0.1, 0.2, 0.3, 0.4 μm. Preferably, the aforementioned predetermined protrusion height may be 0.1 μm.

As shown in FIG. 5 , a structure diagram of a piezoelectric bulk wave resonator according to an embodiment of the present invention when the multilayer structure is convex upward, wherein the multilayer film structure M is convex upward. By controlling the process parameters during the formation of the multi-layer film structure M, the multi-layer film structure M can be arched upward after removing the material of the sacrificial layer, so as to prevent the multi-layer film structure from contacting the bottom of the cavity.

Scanning a cross-section on the surface of the multilayer film structure M through a step meter can describe the surface profile as a curve with an upward arch in the middle. In this way, the sound wave can be well reflected in the overlapping range of the effective area and the cavity area, and at the same time, it is not affected by the environment. Further deformation of the multilayer film structure due to changes (such as temperature changes or impact forces) leaves a certain safety margin and avoids Q-value degradation due to leakage of sound waves from the resonator in the cavity region. Since the multilayer film structure is upwardly arched, a cavity with a shallower depth than that of the piezoelectric bulk wave resonator structure of the embodiment shown in FIG. 4 can be formed when making the substrate cavity. Preferably, the cavity depth can be 0.5-1μm. Such a structural design reduces the etching time, and more importantly, the shallow cavity relative to the deep cavity makes the structure have better stability and improves the yield rate in the production process.

In addition, if the environment requires it, the piezoelectric bulk wave resonator according to the embodiment of the present invention may further include:

a support, configured above the substrate;

The cover layer is supported by a support, and there is an interval between the raised multilayer structure and the cover layer.

The surface of the cover layer may be flat, or may be concave upward. In the piezoelectric bulk wave resonator according to the embodiment of the present invention, the raised multilayer structure is not in contact with the capping layer. In order to avoid the acoustic wave energy of the bulk acoustic wave resonator from being coupled to the cover layer through the air, the minimum distance between the multilayer film structure and the cover layer should be at least greater than a quarter of the wavelength of the resonant sound wave in the air. Preferably, the minimum distance is greater than 0.1 μm.

In the piezoelectric bulk wave resonator described in the above embodiments, the film structure above the cavity is sunken downward or arched upward, and there is a certain safety distance from the bottom or top of the substrate cavity to package the wafer, so as to avoid The contact between the layer film structure and the bottom of the cavity or the packaging wafer results in a decrease in the Q value of the resonator and damage to the performance of the filter.

According to another aspect of the present invention, a design method of a piezoelectric bulk wave resonator is provided, in which, by paralleling a small-area resonator with a cavity in the substrate, it is possible to control the large-area frequency impedance performance at the same time The degree of depression or protrusion of the multilayer film structure on the cavity avoids the decrease of the Q value of the resonator and the performance degradation caused by the contact between the bottom of the multilayer film structure and the bottom of the cavity, or the contact between the top of the multilayer film structure and the packaging wafer. damage etc.

And, regardless of whether a small-area substrate cavity resonator is used, the cavity shape of the substrate can be long and narrow, and, in the opening plane of each groove, two points connecting the opening edge of the groove The ratio of the length of the longest straight line to the diameter of the largest inscribed circle of the opening of the groove is greater than 1. Optionally, the shape of the opening of at least one groove may include: circular, polygonal, and irregular. The effect of the technical solution of the present invention makes the degree of depression or protrusion of the multilayer film structure on the cavity of the piezoelectric bulk wave resonator with a large area controlled, avoiding the contact between the bottom of the multilayer film structure and the bottom of the cavity or the multilayer film Resonator Q degradation or performance impairment due to contact of the top of the structure with the package wafer.

According to the piezoelectric bulk wave resonator structure of the embodiment of the present invention, the surface shape of the effective area and the corresponding substrate cavity is characterized by a narrow and long shape. The cross-sectional shape of the cavity can be rectangular, elliptical, circular, polygonal, etc. When the cross-sectional shape of the cavity is rectangular, the aspect ratio is required to be greater than 1. When the cross-sectional shape of the cavity is elliptical, the length of the major axis and the minor axis of the ellipse are required. ratio greater than 1. When the cross-sectional shape of the cavity is an irregular polygon, the requirements for the cross-sectional shape of the cavity are defined and restricted as follows: As shown in Figure 6, the diameter of the largest inscribed circle in the defined polygonal area is d, and the defined polygonal area The maximum distance between two points is L, requiring L:d>1.

As shown in Figure 7, by forming a narrow and long cavity and an effective area on the cavity while keeping the area constant, for example, in Figure 7, the square U is changed into a rectangle U', and the irregular shape X becomes X', so that the circular Z becomes Z', such a structural change makes the boundary of the suspended multilayer film effectively constrained, and it is not easy to form a large deflection in the film, so the multilayer film structure on the cavity does not There will be a large depression or convexity, the bottom of the multilayer film structure will not be in contact with the bottom of the cavity, the sound wave can be well reflected, and the Q value reduction caused by the leakage of the sound wave of the resonator in the cavity area is avoided . In a filter using a piezoelectric bulk wave resonator with a cavity as a basic unit, piezoelectric bulk wave resonators with different areas are usually required. By rationally patterning the surface shapes of cavities with different areas, the excessive concave or convex situation of the multilayer film structure is controlled, the reduction of the Q value of the resonator is avoided, and the filter performance of the resonator can meet the design requirements.

In addition, the degree of protrusion of the multilayer film structure to the outside of the cavity can also be controlled through the technical method in the embodiment of the present invention. The structure is not in contact with the packaging wafer, so the leakage of sound waves in the effective area is also avoided, and the reduction of the Q value of the resonator is avoided.

In addition, in another embodiment of the present invention, the multilayer film structure of the piezoelectric bulk wave resonator structure includes a lower electrode, a piezoelectric layer covering the lower electrode, and an upper electrode covering the piezoelectric layer, Wherein, in areas other than the plurality of grooves, the upper electrode and the lower electrode do not overlap. Optionally, the shape of the opening of at least one groove may include: circular, polygonal, and irregular.

According to the technical solution of the present invention, the frequency impedance performance of the large-area piezoelectric bulk wave resonator can be realized through the parallel connection of the small-area piezoelectric bulk wave resonator, and at the same time, the concave or convex degree of the multilayer film structure is reduced. Further, the shape of the groove surface of the piezoelectric bulk wave resonator may adopt the shape shown in the ratio shown in FIG. 6 .

Figures 8a, 8b and 8c show a piezoelectric bulk wave resonator according to another embodiment of the present invention. As shown in FIG. 8a, it is a top view of a piezoelectric bulk wave resonator according to another embodiment of the present invention. The piezoelectric bulk wave resonator structure according to an embodiment of the present invention includes: a substrate S, a cavity C, and a bottom electrode B , the piezoelectric layer P and the upper electrode T, wherein, the overlapping area of the bottom electrode B, the piezoelectric layer P and the upper electrode T in the vertical direction is defined as the effective area of the piezoelectric bulk wave resonator, and all The composite film structure composed of films is defined as a multilayer film structure; Figure 8b is a cross-sectional view taken along the section line A-A of the piezoelectric bulk wave resonator shown in Figure 8a; Figure 8c is a section view taken along the piezoelectric bulk wave resonator shown in Figure 8a A cross-sectional view taken along the section line N-N of the resonator. It can be seen from Figures 8a-8c that the bottom electrodes formed on the substrate are connected to each other across the two cavities, and the top electrodes on the two cavities are also connected together, and the P part of the piezoelectric layer is etched to expose the bottom. Electrode B is connected electrically, and as a result, the resonator structures on the two cavities are connected in parallel, wherein the connection part pattern of the bottom electrode and the connection part pattern of the top electrode do not overlap in the direction perpendicular to the substrate, so No active area is formed outside the cavity to cause energy leakage. Since the area of the multilayer film structure on a single cavity is reduced, the depression of the multilayer film structure is effectively controlled, and the sound wave can be well reflected, avoiding the leakage of the sound wave of the resonator in the cavity area. The Q value is reduced while realizing the frequency impedance performance of a large-area resonator.

Similarly, the method in this embodiment can also control the degree of protrusion of the multilayer film structure to the outside of the cavity so that the multilayer film structure does not contact the packaging wafer. FIG. 9a is a piezoelectric piezoelectric film according to another embodiment of the present invention The top view of the bulk wave resonator, the structural composition of the piezoelectric bulk wave resonator shown in Figure 9a is the same as that of the piezoelectric bulk wave resonator shown in Figure 8a; Figure 9b is along the piezoelectric bulk wave resonator shown in Figure 9a A cross-sectional view taken along the section line A-A; FIG. 9c is a cross-sectional view taken along the section line N-N of the piezoelectric bulk wave resonator shown in FIG. 9a. The structure shown in Figures 9a-9c is basically the same as the structure shown in Figures 8a-8c, the difference lies in the multilayer film structure (including the upper electrode T, the piezoelectric layer P, the bottom electrode B) in the structure shown in Figures 9a-9c ) protrude upwards and have a certain distance from the packaging wafer. The convex structure also enables sound waves to be well reflected, avoiding the reduction of the Q value caused by the leakage of the sound waves of the resonator in the cavity region, and at the same time realizing the frequency impedance performance of the large-area resonator.

Figures 8a-8c and Figures 9a-9c show only two exemplary embodiments, and for the sake of simplicity, the channels for removing the sacrificial layer material are not shown in the figures. Although Figures 8a-8c and Figures 9a-9c show two resonator cavities connected in parallel, and the shape of their effective area is rectangular, in fact, the number of resonators can be more, and the cavity of the resonator The shape of the cavity and the effective area can also be circular, elliptical, polygonal, etc. In addition, there are many ways to connect resonators in parallel, such as connecting the upper and lower electrodes of different resonators, using metals with higher conductivity materials other than the top electrode or bottom electrode material for electrical parallel connection of resonators, etc. It should be understood that, in order to control the concave or convex degree of the multilayer film structure and avoid the reduction of the Q value of the resonator, the practice of achieving the effect of the electrical impedance characteristic of the larger area resonator by parallel connection of the smaller area resonator should be in the within the protection scope of this patent.

According to an embodiment of the present invention, a method for manufacturing a piezoelectric bulk wave resonator is provided.

A manufacturing method of a piezoelectric bulk wave resonator according to an embodiment of the present invention includes:

Step 1, providing a substrate;

Step 2, forming at least one groove on the substrate;

Step 3, filling the sacrificial material in at least one groove;

Step 4, forming a multilayer structure above the substrate, the multilayer structure covering the substrate and at least one groove;

Step 5, removing the sacrificial material in the groove to form at least one cavity to form the acoustic reflection structure of the piezoelectric bulk wave resonator;

Step 6, wherein at least one groove is formed by etching, and the depth of each groove is controlled by controlling the etching time, so as to prevent the multilayer structure from contacting the bottom of the cavity after the sacrificial material is removed;

Alternatively, the multilayer structure protrudes away from the bottom of the cavity, and the height of the protrusion is greater than or equal to a predetermined height of the protrusion, preferably, the predetermined height of the protrusion is 0.1 μm. The multilayer structure is the multilayer film structure mentioned in the text. When the multilayer structure is convex upward, the depth of the groove may be shallower than when the multilayer structure is concave downward.

Wherein, the number of the above-mentioned grooves is multiple, and when at least one groove is formed on the substrate, by controlling the number and/or parameters of the formed grooves, the direction of the multilayer structure toward the groove after the sacrificial material is removed is controlled. The extent to which the bottom of the groove is recessed and avoids contact of the multilayer structure with the bottom of the cavity.

And, in the case where the multilayer structure is depressed toward the bottom of the cavity, for each cavity, the minimum distance between the multilayer structure and the bottom of the cavity is greater than a predetermined distance, preferably, the predetermined distance is 0.1 μm .

Further, in the opening plane of each groove, the ratio of the length of the longest straight line connecting two points on the edge of the opening of the groove to the diameter of the largest inscribed circle of the opening of the groove is greater than 1.

Moreover, the multi-layer structure includes a lower electrode, a piezoelectric layer covering the lower electrode, and an upper electrode covering the piezoelectric layer, wherein the upper electrode and the lower electrode do not overlap in regions other than the plurality of grooves.

Optionally, the shape of the opening of at least one groove includes: circular, polygonal, and irregular.

In addition, the manufacturing method of the above-mentioned piezoelectric bulk wave resonator may further include:

disposing a support over the substrate prior to removing the sacrificial material in the groove;

removing the sacrificial material in the groove to form at least one cavity to form the acoustic reflection structure of the piezoelectric bulk wave resonator;

Wherein, by controlling the shape of the contact surface between the cavity and the multilayer structure, the multilayer structure is prevented from protruding upward beyond the height of the support after the sacrificial material is removed.

Moreover, the manufacturing method of the piezoelectric bulk wave resonator further includes:

disposing a support above the substrate;

A cover layer is provided, supported by a support, with a space between the raised multilayer structure and the cover layer in the case where the multilayer structure protrudes away from the bottom of the cavity. Wherein, the surface of the cover layer relative to the multilayer film structure can be concave upwards, or can be flat.

According to an embodiment of the present invention, both the substrate and the packaging wafer described herein may be made of silicon, germanium, gallium arsenide, gallium nitride, sapphire, etc., but are not limited to the above materials. The upper and lower electrodes can be made of gold (Au), tungsten (W), molybdenum (Mo), platinum (Pt), ruthenium (Ru), iridium (Ir), titanium tungsten (TiW), aluminum (Al), titanium ( Ti) and other similar metals, the materials of the upper and lower electrodes are generally the same, but can also be different. The piezoelectric layer can be aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium niobate (LiNbO ₃ ), quartz (quartz), potassium niobate (KNbO ₃ ) or lithium tantalate (LiTaO ₃ ) and other materials, but not limited to the above materials.

To sum up, with the help of the above technical solution of the present invention, the present invention ensures the multilayer structure of the piezoelectric bulk wave resonator by controlling the degree of downward depression and the height of the upward convexity, so as to ensure the multi-layer structure of the piezoelectric bulk wave resonator. The effective area of the layered film structure is not in contact with the upper and lower solid surfaces, thereby ensuring a good reflection effect of the bulk acoustic wave, and maintaining the Q value at the original level, thereby obtaining a multilayer film structure that ensures the effective area of the bulk acoustic wave resonator. The upper and lower surfaces have A piezoelectric bulk wave resonator structure with good bulk acoustic wave reflection effect and a multilayer film structure piezoelectric filter structure.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (16)

1. a kind of piezoelectrics wave resonator, it is characterised in that including：

Sandwich construction；

Substrate, the surface of the substrate has at least one groove, and described at least one described groove of sandwich construction covering passes through At least one cavity formed constitutes the sound reflecting structure of the piezoelectrics wave resonator；

Wherein, in each cavity, the sandwich construction is configured to the bottom notch to the cavity, and the sandwich construction is with being somebody's turn to do Minimum range between the bottom of cavity is contacted more than preset distance with the bottom not with cavity, wherein, the bottom of the cavity It is flat surface；Or, the sandwich construction is raised to the direction of the bottom away from the cavity, and raised height is more than or equal to Predetermined height of projection；And

Top electrode above supporting part and bottom electrode between adjacent cavities is misaligned in vertical direction.

2. piezoelectrics wave resonator according to claim 1, it is characterised in that the preset distance is 0.1 μm.

3. piezoelectrics wave resonator according to claim 1, it is characterised in that the predetermined height of projection is 0.1 μm.

4. piezoelectrics wave resonator according to claim 1, it is characterised in that in the plane of the opening of each groove, even The length and the diameter ratio of the maximum inscribed circle of the opening of the groove for connecing the most long straight line of 2 points of the edge of opening of the groove are big In 1.

5. piezoelectrics wave resonator according to claim 1, it is characterised in that the sandwich construction includes bottom electrode, covered The piezoelectric layer being placed on above the bottom electrode and the Top electrode being covered in above the piezoelectric layer, wherein, the multiple recessed Region beyond groove, the Top electrode is not overlapping with the bottom electrode.

6. piezoelectrics wave resonator according to claim 1, it is characterised in that the opening shape of at least one groove Including：Circle, polygon, irregular shape.

7. piezoelectrics wave resonator according to claim 1, it is characterised in that further comprise：

Supporter, configuration is square over the substrate；

Cap rock, is supported by above support, has interval between the raised sandwich construction and the cap rock.

8. a kind of manufacture method of piezoelectrics wave resonator, it is characterised in that including：

Substrate is provided；

At least one groove is formed over the substrate；

Expendable material is filled at least one described groove；

Square into sandwich construction over the substrate, the sandwich construction covers the substrate and at least one described groove；

Expendable material in the groove is removed, the sound reflecting that at least one cavity constitutes the piezoelectrics wave resonator is formed Structure；

Wherein, the sandwich construction is configured to the bottom notch to the cavity, and at least one described groove is formed by etching, and And, the depth of each groove is controlled by controlling etching period, for each cavity, the bottom of the sandwich construction and the cavity The bottom that minimum range between portion is more than preset distance to avoid the expendable material from being removed rear sandwich construction and cavity connects Touch, wherein, the bottom of the cavity is flat surface；

Or, the sandwich construction is raised to the direction of the bottom away from the cavity, and raised height is more than or equal to predetermined convex Play height；And

Top electrode above supporting part and bottom electrode between adjacent cavities is misaligned in vertical direction.

9. manufacture method according to claim 8, it is characterised in that the quantity of the groove is multiple, also, described When at least one groove is formed on substrate, controlled by the quantity and/or parameter of the groove for controlling to be formed in the sacrifice material The degree that the sandwich construction is recessed to bottom portion of groove after material is removed, and avoid the bottom of the sandwich construction and cavity from connecing Touch.

10. manufacture method according to claim 8, it is characterised in that the preset distance is 0.1 μm.

11. manufacture method according to claim 8, it is characterised in that the predetermined height of projection is 0.1 μm.

12. manufacture method according to claim 8, it is characterised in that in the plane of the opening of each groove, connect this recessed The length of the most long straight line of 2 points of the edge of opening of groove and the diameter ratio of the maximum inscribed circle of the opening of the groove are more than 1.

13. manufacture method according to claim 8, it is characterised in that the sandwich construction includes bottom electrode, is covered in institute The piezoelectric layer above bottom electrode and the Top electrode being covered in above the piezoelectric layer are stated, wherein, beyond the multiple groove Region, the Top electrode is overlapping with the bottom electrode.

14. manufacture method according to claim 8, it is characterised in that the opening shape of at least one groove includes： Circle, polygon, irregular shape.

15. manufacture method according to claim 8, it is characterised in that further comprise：

Before the expendable material in the groove is removed, side configures supporter over the substrate；

Expendable material in the groove is removed, the sound reflecting that at least one cavity constitutes the piezoelectrics wave resonator is formed Structure；

Wherein, by controlling the cavity surface configuration of the contact with the sandwich construction, it is to avoid the expendable material is removed The sandwich construction raises up more than the height of above support afterwards.

16. manufacture method according to claim 8, it is characterised in that further comprise：

Side configures supporter over the substrate；

Cap rock is provided, supported by above support, it is convex in the case of sandwich construction is raised to the direction of the bottom of the remote cavity There is interval between the sandwich construction and the cap rock that rise.