WO2020125355A1

WO2020125355A1 - Filter having increased via hole area and electronic apparatus

Info

Publication number: WO2020125355A1
Application number: PCT/CN2019/121110
Authority: WO
Inventors: 杨清瑞; 庞慰; 张孟伦
Original assignee: 天津大学; 诺思(天津)微系统有限责任公司
Priority date: 2018-12-18
Filing date: 2019-11-27
Publication date: 2020-06-25
Also published as: CN111342807A; CN111342807B

Abstract

The present invention relates to a filter unit, comprising: a functional substrate; a functional device provided on the functional substrate and having an input port, an output port and a grounding port; and a package substrate provided opposite to the functional substrate, the package substrate being provided with a plurality of via holes extending therethrough. The plurality of via holes are provided outside a region where the functional device is located, at least one of the plurality of via holes is a first via hole electrically connected to a corresponding port, and the opening area of the first via hole on the surface of the package substrate is not less than 100 square microns. The present invention further relate to a filter and an electronic apparatus having the filter. On the basis of the solution above, additional electrical impedance caused by the non-functional region can be reduced, and the heat dissipation effect of the device is improved, thereby improving the reliability of the device.

Description

Filter and electronic device with increased via area

Technical field

Embodiments of the present invention relate to the semiconductor field, and in particular, to a filter unit, a filter with the filter unit, and an electronic device with the filter unit or filter.

Background technique

The radio frequency filter is one of the indispensable important devices in the radio frequency front end of various wireless communication systems. It can effectively filter out various unnecessary signals and noises, reduce the signal interference between various communication channels, and thus guarantee the normal operation of the communication equipment. To achieve high-quality communication, and then to achieve the effective use of spectrum resources.

In recent years, with the rapid development of wireless mobile communication technology, wireless communication equipment has gradually developed toward portable, multi-functional, high-performance, and low-cost, which has promoted electronic components to be miniaturized, highly integrated, highly reliable, and high yield. The direction of development, RF filters are no exception.

The requirement for miniaturization of RF filters has led to smaller and smaller chip areas. For certain filter specifications, when using fixed materials for processing, the area of the device functional area on the chip will remain basically unchanged, thereby forcing the shrinkage of the gasket outside the functional area (Pad) and via size. The smaller the size of the gasket and the via, the greater the electrical impedance, which will affect the insertion loss and heat dissipation of the filter, resulting in a reduction in the power capacity of the filter.

FIG. 1a is a schematic top view of a filter unit (filter chip) 100 in the prior art. In FIG. 1a, reference numeral 110 is a gasket, reference numeral 120 is an effective area or functional area of a device, and reference numeral 130 is a metal through hole or via. The device effective area 120 has a single-end-single-end trapezoidal structure, and is composed of a plurality of piezoelectric acoustic wave resonators S121, S122, S123 connected in series and a plurality of piezoelectric acoustic wave resonators P121, P122 connected in parallel. In Figure 1a, "IN" indicates an input port, "OUT" indicates an output port, and "G1" and "G2" indicate ground ports.

Fig. 1b is a partially enlarged cross-sectional view taken along line AA' in Fig. 1a. In FIG. 1b, reference numeral 140 is a packaging substrate (cap), reference numeral 150 is a functional substrate, reference numeral 160 is an adhesive layer, and reference numeral 170 is a sealing structure. The metal layer and the adhesion layer 160 on the gasket 110 may be made of gold, tungsten, molybdenum, platinum, ruthenium, iridium, germanium, copper, titanium, titanium tungsten, aluminum, chromium, arsenic doped gold, or an alloy thereof Or made in combination.

FIG. 1c schematically shows the filter unit 100 in a state where the flip-chip packaging is completed. In FIG. 1c, reference numeral 180 is a substrate, and reference numeral 190 is a metal ball (solder ball) that bonds the substrate 180 and the filter unit 100 together. The heat generated during the operation of the filter will be introduced into the substrate 180 through the adhesive layer 160, the metal via 130, the metal layer on the spacer 110, the metal ball 190, and the adhesive layer 160 to achieve heat dissipation.

When the metal gaskets and vias are small and the number is small, there are few heat conduction paths, which results in poor heat dissipation, resulting in severe local heating of the functional zone resonator and failure.

It can be seen that in the existing filter unit, the impedance of the via is large, the heat dissipation effect after the device is packaged is poor, and the power capacity is low, which affects the technical index of the product and reduces its reliability.

Summary of the invention

Reducing the additional electrical impedance caused by the non-functional area, improving the heat dissipation effect of the device, and improving the reliability of the device have become one of the problems to be solved urgently in the development of radio frequency filters. In order to alleviate or solve at least one aspect of using the above problems in the prior art, the present invention is proposed.

According to an aspect of an embodiment of the present invention, a filter unit is proposed, including:

Functional base

A functional device, provided on the functional substrate, having an input port, an output port, and a ground port; and

The packaging substrate is opposite to the functional substrate, and the packaging substrate is provided with a plurality of vias extending therethrough,

among them:

The plurality of via holes are provided outside the area where the functional device is located;

At least one of the plurality of vias is a first via electrically connected to the corresponding port, and the area of the opening of the first via on the surface of the packaging substrate is not less than 100 square microns, further, Not less than 300 square microns.

Optionally, the total area of the openings of the plurality of vias at the surface of the packaging substrate is not less than 15% of the area of the surface of the packaging substrate.

Optionally, the opening of the first via hole on the surface of the packaging substrate has a longitudinal aperture size of not less than 20 μm, and a lateral aperture size of not less than 5 μm, and an aspect ratio of greater than 4; or a longitudinal aperture size of not less than 25 μm, and lateral The caliber size is not less than 10μm.

Optionally, the plurality of vias include two first vias juxtaposed.

Optionally, on the surface of the packaging substrate, two juxtaposed first vias are respectively provided at the opening position with a first gasket and a second gasket disposed around and electrically connected thereto; and the first The closed shape formed by the gasket and the closed shape formed by the second gasket have a common side, or the closed shape formed by the first gasket and the closed shape formed by the second gasket are spaced apart from each other open. Further, a heat transfer conductive layer is provided between the packaging substrate and the functional substrate at positions corresponding to the two juxtaposed first vias; and the juxtaposed two first vias are both connected to the heat transfer The conductive layer is electrically connected.

Optionally, the plurality of vias further includes a second via hole juxtaposed with the corresponding first via hole, and on the surface of the packaging substrate, the juxtaposed first via hole is provided around the opening at the opening position And the first gasket electrically connected thereto, the corresponding second via hole is provided at the opening position with a second gasket disposed around and electrically connected to the second gasket; and the first gasket surrounds the closed shape and the first gasket The closed shapes formed by the two gaskets are spaced apart from each other. Further, the area of the opening of the second via hole on the surface of the packaging substrate is not less than 100 square microns, further, not less than 300 square microns. Further, the opening of the second via hole on the surface of the packaging substrate has a longitudinal aperture size of not less than 20 μm, and a lateral aperture size of not less than 5 μm, and an aspect ratio of greater than 4; or a longitudinal aperture size of not less than 25 μm and a lateral aperture The size is not less than 10 μm.

Optionally, at least one of the second vias is thermally connected to the functional device for dissipating heat from the functional device.

Optionally, all vias are the first vias.

Optionally, the sum of the areas of the effective regions of all resonators in the functional device is not greater than 2/3 of the area of one surface of the functional substrate, and further, it is 1/2.

In the above filter unit, optionally, the functional device includes multiple resonators, and the resonator includes a sandwich structure composed of a top electrode, a piezoelectric layer, and a bottom electrode; the piezoelectric layer is doped with the following elements One or more of: scandium, yttrium, magnesium, titanium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium; and doping elements Atomic Fractions range from 1% to 40%.

Optionally, the piezoelectric layer is an aluminum nitride piezoelectric layer, a zinc oxide piezoelectric layer, a lithium niobate piezoelectric layer, or a lead titanium zirconate piezoelectric layer.

Optionally, the atomic fraction of the doping element ranges from 3% to 20%.

An embodiment of the present invention also relates to a filter, including: the above-mentioned filter unit; and a substrate, the filter unit being disposed on the substrate, wherein: at least one via hole forms a thermal connection with the substrate.

Embodiments of the present invention also relate to an electronic device, including the above filter unit or the above filter.

BRIEF DESCRIPTION

The following description and drawings can better help to understand these and other features and advantages in the various embodiments disclosed in the present invention. The same reference numerals in the figures always denote the same parts, among which:

FIG. 1a is a schematic top view of the filter unit 100 in the prior art;

Fig. 1b is a partially enlarged cross-sectional view taken along line AA' in Fig. 1a;

FIG. 1c schematically shows a state in which the filter unit of FIG. 1a is packaged in a flip-chip manner;

2a is a schematic top view of a filter unit according to an exemplary embodiment of the present invention;

2b is a schematic partially enlarged cross-sectional view taken along line BB' in FIG. 2a;

FIG. 2c schematically shows a state in which the filter unit of FIG. 2a is packaged in a flip-chip manner;

3a is a schematic top view of a filter unit according to an exemplary embodiment of the present invention;

Fig. 3b is a schematic partially enlarged cross-sectional view taken along line CC' in Fig. 3a;

4a is a schematic top view of a filter unit according to an exemplary embodiment of the present invention;

4b is a schematic partially enlarged cross-sectional view taken along line DD' in FIG. 4a;

5 is a schematic top view of a filter unit according to an exemplary embodiment of the present invention.

6 is a schematic diagram of a sandwich structure of a bulk acoustic wave resonator; and

7 is a graph showing the relationship between the electromechanical coupling coefficient Nkt and the ratio r of a bulk acoustic wave resonator.

detailed description

The technical solutions of the present invention will be further specifically described below through the embodiments and the accompanying drawings. In the description, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the drawings is intended to explain the general inventive concept of the present invention, and should not be construed as a limitation of the present invention.

The present invention will be exemplarily described below with reference to FIGS. 2a-5.

The filter unit 200 according to an exemplary embodiment of the present invention is described below with reference to FIGS. 2a-2c.

FIG. 2a is a schematic top view of a filter unit 200 according to an exemplary embodiment of the present invention. In FIG. 2a, reference numeral 210 is a pad, reference numeral 220 is an effective area or functional area of the device, and reference numeral 230 is a metal through hole or via. The device effective area 220 has a single-end-single-end trapezoidal structure, and is composed of a plurality of piezoelectric acoustic wave resonators S221, S222, S223 connected in series and a plurality of piezoelectric acoustic wave resonators P221, P222 connected in parallel.

In the present invention, "IN" indicates an input port, "OUT" indicates an output port, and "G1" and "G2" indicate ground ports.

Fig. 2b is a partially enlarged cross-sectional view taken along line BB' in Fig. 2a. In FIG. 2b, reference numeral 240 is a packaging substrate (cap), reference numeral 250 is a functional substrate, reference numeral 260 is an adhesive layer, and reference numeral 270 is a sealing structure. The metal layer and the adhesion layer 260 on the gasket 210 can be made of gold, tungsten, molybdenum, platinum, ruthenium, iridium, germanium, copper, titanium, titanium tungsten, aluminum, chromium, arsenic doped gold, or alloys thereof Or made in combination.

FIG. 2c schematically shows the filter unit 200 in a state where the flip-chip packaging is completed. In FIG. 2c, reference numeral 280 is a substrate, and reference numeral 290 is a metal ball (solder ball) that bonds the substrate 280 and the filter unit 200 together. The heat generated during the operation of the filter will be introduced into the substrate 280 through the adhesive layer 260, the metal via 230, the metal layer on the spacer 210, the metal sphere 290, and the adhesive layer 260 to achieve heat dissipation.

In the example shown in FIGS. 2a-2c, the opening area of the via hole is increased compared to FIGS. 1a-1c.

The increase here can be embodied as follows: the area of the opening of the via hole on the surface of the packaging substrate is not less than 100 square microns, and further, not less than 300 square microns. In an alternative embodiment, the total area of the openings of the plurality of vias at the surface of the packaging substrate is not less than 15% of the area of the surface of the packaging substrate.

Furthermore, the longitudinal aperture size of the via hole at the surface of the packaging substrate is not less than 20 μm, and the lateral aperture size is not less than 5 μm, and the aspect ratio is greater than 4.

It should be noted that, in the present invention, the longitudinal aperture size refers to the longest distance between two points on the opening edge of the opening at the surface of the package substrate for the via, and the lateral aperture size is the opening in the direction perpendicular to the longitudinal direction The longest distance between two points on the edge. The longitudinal and lateral directions here are determined only according to the opening size of the via. For example, it can be simply considered that for the opening of the via, the longitudinal direction of the opening is longitudinal and the width direction of the opening is lateral. More specifically, for example, in FIG. 2a, the opening of the via is shown as a rectangle whose longitudinal direction corresponds to the long-side direction of the rectangle, and the lateral direction corresponds to the short-side direction of the rectangle. The above expression is also applicable to other embodiments of the present invention.

Referring to FIG. 2a, the device effective area or functional area 220 is smaller than the area 120 in FIG. 1a.

In one embodiment, the small can be embodied as: the sum of the areas of the effective regions of all the resonators in the functional device is not greater than 2/3 of the area of one surface of the functional substrate, and further is 1/2 .

It should be noted that the area of the surface of the functional substrate here is the entire area of one surface (including the area where the via and the functional device are located).

In FIG. 2b, the width of the via hole 230 in the thickness direction or the height direction is the same. However, the cross-section of the via hole 230 may also be an isosceles trapezoid shape, or other shapes, which are within the protection scope of the present invention.

In the embodiment shown in FIGS. 2a-2c, the cross-sectional area of the via 230 is increased. Even if the number of vias does not change compared with FIGS. 1a-1c, the heat dissipation effect is improved and the power capacity of the device is improved. .

The filter unit 300 according to an exemplary embodiment of the present invention is described below with reference to FIGS. 3a-3b.

FIG. 3a is a schematic top view of a filter unit 300 according to an exemplary embodiment of the present invention. In FIG. 3a, reference numeral 310 is a pad, reference numeral 320 is an effective area or functional area of the device, and reference numeral 330 is a metal through hole or via. The device effective area 320 has a single-end-single-end trapezoidal structure, and is composed of a plurality of piezoelectric acoustic wave resonators S321, S322, S323 connected in series and a plurality of piezoelectric acoustic wave resonators P321, P322 connected in parallel.

Fig. 3b is a partially enlarged cross-sectional view taken along line CC' in Fig. 3a. In FIG. 3b, reference numeral 340 is a packaging substrate (cap), reference numeral 350 is a functional substrate, reference numeral 360 is an adhesive layer, and reference numeral 370 is a sealing structure. The metal layer and the adhesive layer 360 on the gasket 310 may be made of gold, tungsten, molybdenum, platinum, ruthenium, iridium, germanium, copper, titanium, titanium tungsten, aluminum, chromium, arsenic doped gold, or an alloy thereof Or made in combination.

The flip-chip packaging of the filter unit 300 and the substrate 350 is similar to that shown in FIG. 2c and will not be repeated here.

The difference between the example shown in FIGS. 3a-3b and the example in FIGS. 2a-2c is that in FIGS. 2a-2c, the via is a single structure, while in FIGS. 3a-3b, the via is connected in Double hole structure together. Obviously, in the example of FIGS. 3a-3b, the opening area of the via hole is further increased compared to the solutions in FIGS. 1a-1c.

Similarly, the increase here can be embodied as follows: the area of the opening of each via in the conjoined via on the surface of the packaging substrate is not less than 100 square microns, and the plurality of vias in the packaging substrate The sum of the area of the openings at the surface of is at least 15% of the area of the surface of the packaging substrate. Furthermore, the longitudinal aperture size of each via hole on the surface of the package substrate is not less than 20 μm, and the lateral aperture size is not less than 5 μm, and the aspect ratio is greater than 4; or the longitudinal aperture size is not less than 25 μm , And the lateral caliber size is not less than 10μm.

Referring to FIG. 3a, the device effective area or functional area 320 is smaller than the area 120 in FIG. 1a. In one embodiment, the small can be embodied as: the sum of the areas of the effective regions of all the resonators in the functional device is not greater than 2/3 of the area of one surface of the functional substrate, and further is 1/2 .

In the embodiment shown in FIGS. 3a-3b, the cross-sectional area of the combination of vias 330 is significantly increased compared to the cross-sectional area of single vias in FIGS. 1a-1c, which will improve the heat dissipation effect and improve the device’s Power Capacity.

As shown in FIGS. 3a and 3b, two juxtaposed vias are spaced apart from each other. On the surface of the packaging substrate 340, one via is provided with a first gasket disposed around and electrically connected to the other via in the opening, and the other The opening is provided with a second gasket disposed around and electrically connected to the opening at the opening; and the closed shape enclosed by the first gasket and the closed shape enclosed by the second gasket have a common side. As shown in FIG. 3b, a heat transfer conductive layer 360 is provided between the packaging substrate 340 and the functional substrate 350 at positions corresponding to the juxtaposed vias. The adhesive layer 360 may be a heat-conducting electrical conductor, and the juxtaposed vias are all electrically connected to the corresponding adhesive layer. The adhesive layer electrically connected to the juxtaposed via hole can also be replaced with another heat transfer conductive layer. In the above case, two juxtaposed vias are connected in parallel, so that the impedance becomes smaller, and at the same time, there are more heat dissipation paths or the heat dissipation efficiency is improved.

The filter unit 400 according to an exemplary embodiment of the present invention is described below with reference to FIGS. 4a-4b.

FIG. 4a is a schematic top view of a filter unit 400 according to an exemplary embodiment of the present invention. In FIG. 4a, reference numeral 410 is a pad, reference numeral 420 is an effective area or functional area of a device, and reference numeral 430 is a metal through hole or via. The device effective region 420 has a single-end-single-end trapezoidal structure, and is composed of a plurality of piezoelectric acoustic wave resonators S421, S422, S423 connected in series and a plurality of piezoelectric acoustic wave resonators P421, P422 connected in parallel.

Fig. 4b is a partially enlarged cross-sectional view taken along line DD' in Fig. 4a. In FIG. 4b, reference numeral 440 is a packaging substrate (cap), reference numeral 350 is a functional substrate, reference numeral 360 is an adhesive layer, and reference numeral 370 is a sealing structure. The metal layer and the adhesion layer 460 on the spacer 410 can be made of gold, tungsten, molybdenum, platinum, ruthenium, iridium, germanium, copper, titanium, titanium tungsten, aluminum, chromium, arsenic doped gold, or alloys thereof Or made in combination.

The flip-chip packaging of the filter unit 400 and the substrate 450 is similar to that shown in FIG. 2c, and will not be repeated here.

The difference between the example shown in FIGS. 4a-4b and the example in FIGS. 2a-2c is that in FIGS. 2a-2c, the vias are a single structure, while in FIGS. 4a-4b, the vias are separated from each other. Double hole structure. Obviously, in the example of FIGS. 4a-4b, the opening area of the via hole is further increased compared to the solutions in FIGS. 1a-1c.

The increase here can be embodied as follows: the area of the opening of each via in the double-hole structure on the surface of the packaging substrate is not less than 300 square micrometers, and the plurality of vias on the surface of the packaging substrate The sum of the area of the openings is at least 15% of the area of the surface of the packaging substrate. Furthermore, the longitudinal aperture size of each via in the double-hole structure at the surface of the packaging substrate is not less than 25 μm, and the lateral aperture size is not less than 10 μm.

Referring to FIG. 4a, the device effective area or functional area 420 is smaller than the area 120 in FIG. 1a. In one embodiment, the small can be embodied as: the sum of the areas of the effective regions of all the resonators in the functional device is not greater than 2/3 of the area of one surface of the functional substrate, and further is 1/2 .

In the embodiment shown in FIGS. 4a-4b, the combined cross-sectional area of the two vias 430 is significantly increased compared to the cross-sectional area of the single vias in FIGS. 1a-1c, which will improve the heat dissipation effect and improve the device. Power capacity.

As shown in FIGS. 4a and 4b, two juxtaposed vias are spaced apart from each other, and on the surface of the packaging substrate 440, one via is provided at the opening position with a first gasket 410 disposed around and electrically connected to it, The other via hole is provided with a second gasket 410' disposed around and electrically connected to the opening. The first gasket and the second gasket may use the same material or different; and as shown in FIGS. 4a and 4b, The closed shape formed by the first gasket and the closed shape formed by the second gasket are spaced apart from each other. As shown in FIG. 4b, a heat transfer conductive layer 460 is provided between the packaging substrate 440 and the functional substrate 450 at positions corresponding to the juxtaposed vias. The adhesion layer 460 may be a heat-conducting conductor, and the juxtaposed vias are electrically connected to the corresponding adhesion layer, and the corresponding adhesion layer 460 is electrically connected through the metal connection layer 480, which may be an adhesive A part of the attached layer may be a material different from the adhesive layer. The adhesion layer electrically connected to the juxtaposed via hole and the metal connection layer can also be replaced with other heat transfer conductive layers. In the above case, two juxtaposed vias are connected in parallel, so that the impedance becomes smaller, and at the same time, there are more heat dissipation paths or the heat dissipation efficiency is improved.

The filter unit 500 according to an exemplary embodiment of the present invention is described below with reference to FIG. 5.

FIG. 5 is a schematic top view of a filter unit 500 according to an exemplary embodiment of the present invention. In FIG. 5, reference numeral 510 is a pad, reference numeral 520 is an effective area or functional area of a device, and reference numeral 530 is a metal via or via. The device effective area or functional area 520 has a single-end-single-end trapezoidal structure, and is composed of a plurality of piezoelectric acoustic wave resonators S521, S522, S523 connected in series and a plurality of piezoelectric acoustic wave resonators P521, P522 connected in parallel.

In FIG. 5, for example, on the upper side of the figure, the input port and the output port are respectively connected with a via, for example, the output port is connected to the via 530B. In addition, there are two vias thermally connected to the functional area, for example, the via 530A is thermally connected to the functional area 520; on the lower side of the figure, each ground port is electrically connected to the two vias 530 at the same time.

Thus, in FIG. 5, the corresponding two vias are spaced apart from each other, and gaskets are respectively provided at the openings, and the closed shapes formed by the two gaskets are spaced apart from each other.

As can be seen from FIG. 5, at least one via (for example, 530A) is a heat dissipation via that is thermally connected to the functional area, and is used to dissipate heat from the functional area.

The metal layer on the gasket 510 and the corresponding adhesion layer may be made of gold doped with gold, tungsten, molybdenum, platinum, ruthenium, iridium, germanium, copper, titanium, titanium tungsten, aluminum, chromium, arsenic, or Made of alloy or combination.

The flip-chip packaging of the filter unit 500 and the substrate is similar to that shown in FIG. 2c and will not be repeated here.

The difference between the example shown in FIG. 5 and the examples in FIGS. 4a-4b is that in FIGS. 4a-4b, the vias are a double-hole structure separated from each other, but the double holes are electrically connected to the corresponding ports at the same time; and In FIG. 5, the two vias in the partial double-hole structure, one is electrically connected to the port, and the other is thermally connected to the functional area.

Similarly, in one embodiment, the increase here can be embodied as follows: the area of the opening of the via hole on the surface of the packaging substrate is not less than 300 square microns, and the plurality of via holes are on the surface of the packaging substrate The sum of the areas of the openings at is at least 15% of the area of the surface of the packaging substrate. Furthermore, the longitudinal aperture size of the via hole at the surface of the packaging substrate is not less than 25 μm, and the lateral aperture size is not less than 10 μm.

Referring to FIG. 5, the device effective area or functional area 520 is smaller than the area 120 in FIG. 1a. In one embodiment, the small can be embodied as: the sum of the areas of the effective regions of all the resonators in the functional device is not greater than 2/3 of the area of one surface of the functional substrate, and further is 1/2 .

In the embodiment shown in FIG. 5, the cross-sectional area of the two vias 530 added up is significantly increased compared to the cross-sectional area of the single vias in FIGS. 1a-1c, which will improve the heat dissipation effect and increase the power of the device. capacity.

Similar to the example description with reference to FIGS. 4a and 4b, in FIG. 5, in the case where two juxtaposed vias are formed in parallel, the via impedance becomes smaller, and at the same time, the heat dissipation paths become more or the heat dissipation efficiency is improved.

It should be pointed out that although in the present invention, the functional region has a single-end-single-end trapezoidal structure as an example, the structure of the functional region is not limited to this.

Enlarging the cross-sectional area of the via hole or increasing the number of via holes can be achieved without increasing the size of the current resonator, or without changing or even reducing the size of the current resonator. For the latter case, the present invention proposes a solution to reduce the size of the resonator by reducing the area of the effective area of the resonator.

Specifically, in one embodiment, a bulk acoustic wave resonator (having a piezoelectric layer, a bottom electrode, and a top electrode), by incorporating an impurity element in a piezoelectric layer such as an aluminum nitride (AlN) piezoelectric layer, makes the resonator The area of the effective area is reduced, making the size of the resonator smaller.

The principle of using element doping to reduce the area of the effective area of the bulk acoustic wave resonator is specifically described below with reference to FIGS. 6-7.

Electromechanical coupling coefficient (Nkt) is one of the important performance indicators of bulk acoustic wave resonators. This performance parameter is closely related to the following factors: (1) the proportion of the impurity elements incorporated into the piezoelectric film; and (2) the electrode layer and The thickness ratio of the piezoelectric layer.

The sandwich structure of the bulk acoustic wave resonator shown in FIG. 6 includes a top electrode TE having a thickness t, a bottom electrode BE, and a piezoelectric layer PZ having a thickness d. Define scale here

For a specific undoped resonator, the relationship between the normalized electromechanical coupling coefficient Nkt and the ratio r can be described by the characteristic curve C0 shown in FIG. 7.

As shown in FIG. 7, when the piezoelectric layer of the resonator is doped, the characteristic curve C0 moves upward to form a curve C1. If the electromechanical coupling coefficient of the resonator with the thickness ratio r ₀ is Nkt ₀ before undoping, then the coefficient increases to Nkt ₁ after doping.

Generally, the electromechanical coupling coefficient is limited by the technical specifications of the filter's relative bandwidth and roll-off characteristics, so it needs to remain unchanged. Therefore, in the case of doping, the electromechanical coupling coefficient needs to be restored to the undoped level by adjusting the ratio r. Note that curve C1 has a maximum value, so there are two ways to adjust the ratio r, which can reduce the ratio r from r ₀ to r ₂ or increase to r ₁ . However, since reducing r means that the electrode layer becomes thinner and the resistance increases, which causes the device loss to increase, the ratio r to r ₁ is selected to be increased.

On the other hand, the frequency f of the resonator is constrained by the technical specifications of the filter center frequency and needs to be fixed. The frequency f has the following simplified relationship with the overall thickness of the sandwich structure:

Where D is the equivalent total thickness of the electrode material (Mo) to the piezoelectric material, specifically D = 2tv ₁ /v ₂ + d, where v ₂ is the longitudinal wave sound velocity in the electrode material and v ₁ is the piezoelectric material Medium longitudinal wave sound velocity. Taking formula (1) into formula (2), we can get:

Since the sound velocity v ₁ due to doping decreases, and at the same time, r increases, then if the frequency f is not required to change, then the thickness d of the piezoelectric layer should decrease.

In addition, there is a technical requirement for the impedance of the resonator (50 ohms), and the impedance Z and the thickness d of the piezoelectric layer are related by the following formula:

Where ε is the dielectric constant of the piezoelectric material, A is the effective area of the resonator, and j is the imaginary unit representing the phase.

When the impedance Z is required to be constant, if the thickness d of the piezoelectric layer becomes smaller, the effective area A must also become smaller.

Based on the above, it is possible to reduce the thickness d of the piezoelectric layer by adding an impurity element to the piezoelectric layer, thereby reducing the effective area A of the resonator.

In an embodiment, the piezoelectric layer is doped with one or more of the following elements: scandium, yttrium, magnesium, titanium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium , Holmium, erbium, thulium, ytterbium, lutetium; and the atomic fraction of the doping element ranges from 1% to 40%, further, from 3% to 20%. The specific atomic fraction may be 3%, 6%, 9%, 20%, 30%, 40%, etc.

The piezoelectric layer may be an aluminum nitride piezoelectric layer, a zinc oxide piezoelectric layer, a lithium niobate piezoelectric layer, or a titanium zirconate piezoelectric layer.

In the present invention, the materials of the top electrode and the bottom electrode may be selected but not limited to: molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a combination of the above metals or alloys thereof.

The use of the above doping technical solution greatly reduces the area of the resonator, which can reduce the size of the filter (resonator as the core device of the filter), and can enlarge the width of the via hole when the filter area is unchanged. Cross-sectional area or increase the number of vias.

Correspondingly, the invention also relates to a filter, including the above-mentioned filter unit.

The invention also relates to an electronic device including the above-mentioned filter unit or filter. It should be noted that the electronic devices here include but are not limited to intermediate products such as radio frequency front-ends, filter amplification modules, and terminal products such as mobile phones, WIFI, and drones.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that these embodiments can be changed without departing from the principle and spirit of the present invention. The appended claims and their equivalents are limited.

Claims

A filter unit, including:

Functional base

A functional device, provided on the functional substrate, having an input port, an output port, and a ground port; and

The packaging substrate is opposite to the functional substrate, and the packaging substrate is provided with a plurality of vias extending therethrough,

among them:

The plurality of via holes are provided outside the area where the functional device is located;

At least one of the plurality of vias is a first via electrically connected to the corresponding port, and the area of the opening of the first via on the surface of the packaging substrate is not less than 100 square microns.
The filter unit according to claim 1, wherein:

The area of the opening of the first via hole on the surface of the packaging substrate is not less than 300 square microns.
The filter unit according to claim 1, wherein:

The sum of the area of the openings of the plurality of vias at the surface of the packaging substrate is not less than 15% of the area of the surface of the packaging substrate.
The filter unit according to any one of claims 1-3, wherein:

The opening of the first via hole on the surface of the packaging substrate has a longitudinal aperture size of not less than 20 μm, and a lateral aperture size of not less than 5 μm, and an aspect ratio of not less than 4; or a longitudinal aperture size of not less than 25 μm and a lateral aperture size of Less than 10μm.
The filter unit according to any one of claims 1-3, wherein:

The plurality of vias includes two first vias juxtaposed.
The filter unit according to claim 5, wherein:

On the surface of the packaging substrate, two juxtaposed first vias are respectively provided with first pads and second pads arranged around and electrically connected to the openings at the opening positions;

The closed shape of the first gasket and the closed shape of the second gasket have a common side, or the closed shape of the first gasket and the second gasket The closed shapes are spaced apart from each other.
The filter unit according to claim 6, wherein:

A heat transfer conductive layer is provided between the packaging substrate and the functional substrate at positions corresponding to the two first vias juxtaposed; and

The two juxtaposed first vias are electrically connected to the heat transfer conductive layer.
The filter unit according to any one of claims 1-3, wherein:

The plurality of vias further includes a second via that is juxtaposed with the corresponding first via. On the surface of the packaging substrate, the juxtaposed first via is disposed around the opening and electrically connected to the opening The first gasket of the corresponding second via hole is provided with a second gasket disposed around and electrically connected to the second via hole at the opening position; and

The closed shape formed by the first gasket and the closed shape formed by the second gasket are spaced apart from each other.
The filter unit according to claim 8, wherein:

The area of the opening of the second via on the surface of the packaging substrate is not less than 100 square microns.
The filter unit according to claim 9, wherein:

The area of the opening of the second via hole on the surface of the packaging substrate is not less than 300 square microns.
The filter unit according to claim 8, wherein:

At least one of the second vias is thermally connected to the functional device for dissipating heat from the functional device.
The filter unit according to any one of claims 5-11, wherein:

The opening of the second via hole on the surface of the packaging substrate has a longitudinal aperture size of not less than 20 μm, and a lateral aperture size of not less than 5 μm, and an aspect ratio of not less than 4; or a longitudinal aperture size of not less than 25 μm and a lateral aperture size of not Less than 10μm.
The filter unit according to any one of claims 1-3, wherein:

All vias are the first vias.
The filter unit according to any one of claims 1-13, wherein:

The functional device includes a plurality of resonators, and the resonator includes a sandwich structure composed of a top electrode, a piezoelectric layer, and a bottom electrode;

The sum of the areas of the effective regions of all resonators in the functional device is not greater than 2/3 of the area of one surface of the functional substrate.
The filter unit according to claim 14, wherein:

The sum of the areas of the effective regions of all resonators in the functional device is not greater than 1/2 of the area of one surface of the functional substrate.
The filter unit according to any one of claims 1-15, wherein:

The functional device includes a plurality of resonators, and the resonator includes a sandwich structure composed of a top electrode, a piezoelectric layer, and a bottom electrode;

The piezoelectric layer is doped with one or more of the following elements: scandium, yttrium, magnesium, titanium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, Thulium, Ytterbium, Lutetium; and

The atomic fraction of the doping element ranges from 1% to 40%.
The filter unit according to claim 16, wherein:

The piezoelectric layer is an aluminum nitride piezoelectric layer, a zinc oxide piezoelectric layer, a lithium niobate piezoelectric layer, or a lead titanium zirconate piezoelectric layer.
The filter unit according to claim 16 or 17, wherein:

The atomic fraction of the doping element ranges from 3% to 20%.
A filter, including:

The filter unit according to any one of claims 1-18; and

A substrate, the filter unit is provided on the substrate,

among them:

At least one via forms a thermal connection with the substrate.
An electronic device comprising the filter unit according to any one of claims 1-18 or the filter according to claim 19.