Filter, forming method thereof and electronic equipment

Abstract

The invention discloses a filter and a forming method thereof, and electronic equipment, and the filter comprises a substrate which comprises a working area; the piezoelectric laminated structure is located on the substrate of the working area; the groove is positioned in the substrate at the side part of the working area and is positioned around the piezoelectric laminated structure; according to the embodiment of the invention, the grooves are located around the piezoelectric laminated structure, so that the grooves can effectively isolate external stress and reduce the probability that the external stress is transmitted to the working area, correspondingly, the probability that the piezoelectric laminated structure warps can be reduced, and the probability that the filter generates frequency hopping can be reduced.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of semiconductor manufacturing, and in particular to a filter and a method for forming the filter, and an electronic device. Background Art

[0002] The RF front-end chips of wireless communication devices include power amplifiers, antenna switches, RF filters, multiplexers, and low-noise amplifiers, etc. Among them, RF filters include surface acoustic wave (SAW) filters, bulk acoustic wave (BAW) filters, micro-electro-mechanical system (MEMS) filters, integrated passive devices (IPD) filters, etc.

[0003] BAW filters have the characteristics of relatively low insertion loss, high out-of-band suppression, and relative stability over a wide temperature range. Therefore, BAW filters are widely used in wireless communication devices. High-reliability BAW filters can extend the service life of electronic devices and expand their scope of use.

[0004] At present, there are still many problems in the performance of BAW filters. Summary of the invention

[0005] The problem solved by the embodiments of the present invention is to provide a filter and a method for forming the filter, and an electronic device, which are helpful to reduce the probability of frequency hopping of the filter.

[0006] To solve the above problems, an embodiment of the present invention provides a filter, comprising: a substrate, the substrate comprising a working area; a piezoelectric stack structure located on the substrate in the working area; and a groove located in the substrate on the side of the working area and around the piezoelectric stack structure.

[0007] Correspondingly, an embodiment of the present invention also provides a method for forming a filter, comprising: providing a substrate, the substrate comprising a working area, a piezoelectric stack structure being formed on the substrate of the working area; forming a groove in the substrate on the side of the working area, the groove being located around the piezoelectric stack structure.

[0008] Correspondingly, the present invention further provides an electronic device, comprising the filter described in any embodiment of the present invention.

[0009] Compared with the prior art, the technical solution of the embodiment of the present invention has the following advantages:

[0010] An embodiment of the present invention provides a filter, comprising: a substrate, the substrate comprising a working area; a piezoelectric stack structure, located on the substrate of the working area; a groove, located in the substrate on the side of the working area and located around the piezoelectric stack structure; in this embodiment, since the groove is located around the piezoelectric stack structure, the groove can effectively isolate external stress and reduce the probability of external stress being transmitted to the working area, which can correspondingly reduce the probability of warping of the piezoelectric stack structure, thereby reducing the probability of frequency hopping of the filter.

[0011] In an optional solution, the groove is a non-enclosed structure, and the filter further includes: a first lead electrode, located above the substrate on the side of the piezoelectric laminated structure, the projection pattern of the first lead electrode on the substrate is staggered with the groove, and the first lead electrode is electrically connected to the piezoelectric laminated structure; a covering layer, covering the substrate and the piezoelectric laminated structure; a second lead electrode, penetrating the covering layer on the first lead electrode, and electrically connected to the first lead electrode; compared with the solution using a single-layer lead electrode, the embodiment of the present invention uses a stacked first lead electrode and a second lead electrode to form a lead electrode of a laminated structure, which is beneficial to increase the overall thickness of the lead electrode, thereby reducing the resistance value of the lead electrode, correspondingly reducing the impedance of the lead electrode, and thereby reducing the characteristic impedance (Z S ).

[0012] An embodiment of the present invention also provides a method for forming a filter, comprising: providing a substrate, the substrate comprising a working area, a piezoelectric stack structure being formed on the substrate of the working area; forming a groove in the substrate on the side of the working area, the groove being located around the piezoelectric stack structure; in this embodiment, since the groove is located around the piezoelectric stack structure, the groove can effectively isolate external stress and reduce the probability of external stress being transmitted to the working area, which can correspondingly reduce the probability of warping of the piezoelectric stack structure, thereby reducing the probability of frequency hopping of the filter.

[0013] In an optional scheme, in the step of providing the substrate, a first lead electrode is also formed above the substrate on the side of the piezoelectric stack structure, and the first lead electrode is electrically connected to the piezoelectric stack structure; after forming the first lead electrode, the formation method also includes: forming a covering layer covering the substrate, the piezoelectric stack structure and the first lead electrode; after forming the covering layer, forming a second lead electrode that penetrates the covering layer on the first lead electrode and is electrically connected to the first lead electrode; after forming the second lead electrode, a groove is formed in the substrate on the side of the working area, the groove is a non-closed structure, and the groove is staggered with the projection pattern of the first lead electrode on the substrate; compared with the scheme of using a single-layer lead electrode, the embodiment of the present invention uses a stacked structure of a lead electrode of a stacked structure composed of a stacked first lead electrode and a second lead electrode, which is beneficial to increasing the overall thickness of the lead electrode, thereby reducing the resistance value of the lead electrode, correspondingly reducing the impedance of the lead electrode, and thereby reducing the characteristic impedance of the filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figures 1 to 4 It is a schematic structural diagram of an embodiment of a filter of the present invention;

[0015] Figures 5 to 24 It is a structural schematic diagram corresponding to each step in an embodiment of a method for forming a filter of the present invention. DETAILED DESCRIPTION

[0016] At present, there are still many problems in the performance of BAW filters.

[0017] In the prior art, during the actual use of the filter device, due to some environmental factors, for example, under different temperature conditions, the coefficient of thermal expansion (CTE) between the material of the filter chip and the material of the substrate does not match, or the substrate is subjected to external forces, etc., the substrate will be stressed and the filter chip will be warped, which may easily cause the filter to frequency jump.

[0018] In order to solve the above technical problems, an embodiment of the present invention provides a filter, comprising: a substrate, the substrate including a working area; a piezoelectric stack structure located on the substrate in the working area; and a groove located in the substrate on the side of the working area and around the piezoelectric stack structure.

[0019] In the solution disclosed in the embodiment of the present invention, since the groove is located around the piezoelectric stack structure, the groove can effectively isolate external stress and reduce the probability of external stress being transmitted to the working area, which can correspondingly reduce the probability of warping of the piezoelectric stack structure, thereby reducing the probability of frequency hopping of the filter.

[0020] In order to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and understandable, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0021] Figures 1 to 4 1 is a schematic diagram of the structure of an embodiment of a filter of the present invention. Specifically, Figure 1 It is a top view. Figure 2 yes Figure 1 A local enlarged view at D. Figure 3 yes Figure 1 Cross-sectional view along BB1 direction, Figure 4 yes Figure 1 Cross-sectional view along CC1 direction.

[0022] It should be noted that for the convenience of illustration, Figure 4 It is a simple schematic diagram.

[0023] refer to Figures 1 to 4 The filter comprises: a substrate 100, wherein the substrate 100 comprises a working area I; a piezoelectric stack structure 101 (such as Figure 3 ), located on the base 100 of the working area I; the groove 102 (as shown Figure 4 As shown), it is located in the substrate 100 at the side of the working area I and is located around the piezoelectric stack structure 101.

[0024] The substrate 100 is used to provide a process platform for forming a bulk acoustic wave (BAW) filter. A BAW filter is a special filtering device made by using the piezoelectric effect and the physical characteristics of acoustic bulk wave propagation. In a BAW filter, the sound wave mainly propagates in the vertical direction inside the filter. BAW filters have the advantages of high operating frequency, high quality factor (Q value), good temperature stability and high frequency characteristic consistency, and therefore are widely used in various electronic devices.

[0025] In this embodiment, the material of the substrate 100 is silicon. In other embodiments, the material of the substrate includes one or more of germanium, silicon germanium, silicon carbide, silicon germanium carbide, indium arsenide, gallium arsenide, and indium phosphide, and the substrate may also be a ceramic substrate, a quartz substrate, a glass substrate, or other types of substrates.

[0026] It should be noted that working area I refers to the effective resonance area, that is, the area that can store and release energy, which is mainly used to maintain oscillation, that is, store and transmit energy so that the filter can maintain stable amplitude and frequency.

[0027] The piezoelectric stacked structure 101 is used to provide a process basis for forming a filter. The corresponding piezoelectric stacked structure 101 is used to realize the mutual conversion between the electrical signal and the acoustic signal, so that the filter performs filtering processing on the signal.

[0028] Specifically, the piezoelectric stack structure 101 includes a bottom electrode layer (not labeled) located on the substrate 100 , a piezoelectric layer (not labeled) located on the bottom electrode layer, and a top electrode layer (not labeled) located on the piezoelectric layer.

[0029] The material of the bottom electrode layer is a conductive material. The conductive material may be a metal material with conductive properties, such as one or more of molybdenum (Mo), aluminum (Al), copper (Cu), platinum (Pt), gold (Au), iridium (Ir), osmium (Os), rhenium (Re), palladium (Pd), rhodium (Rh), ruthenium (Ru) and tungsten (W). As an example, the material of the bottom electrode layer is molybdenum.

[0030] It can be understood that, in other embodiments, the material of the bottom electrode layer may also be other electrode materials suitable for forming a piezoelectric stack structure.

[0031] The material of the piezoelectric layer is piezoelectric material, which is a crystalline material that will generate voltage between the two end surfaces when subjected to pressure. Piezoelectric material has a piezoelectric effect. The piezoelectric effect of piezoelectric material can be used to realize the mutual conversion between mechanical vibration (sound waves) and alternating current, thereby realizing the conversion of sound energy into electrical energy.

[0032] The material of the piezoelectric layer may be a piezoelectric crystal, a piezoelectric ceramic or a piezoelectric polymer, etc. The piezoelectric crystal may be aluminum nitride, lead zirconate titanate, quartz crystal, lithium gallate, lithium germanate, titanium germanate, lithium niobate or lithium tantalate, etc., and the piezoelectric polymer may be polyvinylidene fluoride, vinylidene fluoride-trifluoroethylene copolymer, nylon-11 or vinylene dicyano-vinyl acetate alternating copolymer, etc.

[0033] In this embodiment, the piezoelectric layer may be formed by using a deposition process such as a chemical vapor deposition process (CVD), a physical vapor deposition process (PVD), or an atomic layer deposition process (ALD).

[0034] The material of the top electrode layer is a conductive material. The conductive material may be a metal material with conductive properties, such as one or more of molybdenum, aluminum, copper, platinum, gold, iridium, osmium, rhenium, palladium, rhodium, ruthenium and tungsten. As an example, the material of the top electrode layer is molybdenum.

[0035] It can be understood that, in other embodiments, the material of the top electrode layer may also be other electrode materials suitable for forming a piezoelectric stack structure.

[0036] The groove 102 is used to isolate external stress.

[0037] It should be noted that, since the groove 102 is located around the piezoelectric stack structure 101, the groove 102 can effectively isolate external stress and reduce the probability of external stress being transmitted to the working area I, which can correspondingly reduce the probability of warping of the piezoelectric stack structure 101, thereby reducing the probability of frequency hopping of the filter.

[0038] In this embodiment, reference Figure 4 , along the direction parallel to the top surface of the substrate 100, the opening size w1 of the groove 102 should not be too small. If the opening size w1 of the groove 102 is too small, on the one hand, the groove 102 may not be able to isolate the external stress effectively, and on the other hand, it may increase the difficulty of forming the groove 102. Therefore, in this embodiment, along the direction parallel to the top surface of the substrate 100, the opening size w1 of the groove 102 is greater than or equal to 3 microns.

[0039] In this embodiment, reference Figure 4 , the ratio of the depth h of the groove 102 to the thickness t of the substrate 100 should not be too small. If the ratio of the depth h of the groove 102 to the thickness t of the substrate 100 is too small, that is, when the thickness t of the substrate 100 remains unchanged, the depth h of the groove 102 is too small, which makes it easy for the groove 102 to play a poor role in isolating external stress. Therefore, in this embodiment, the ratio of the depth h of the groove 102 to the thickness t of the substrate 100 is greater than or equal to 1 / 3.

[0040] In this embodiment, reference Figure 4 , along the direction parallel to the top surface of the substrate 100, the distance L1 between the groove 102 and the piezoelectric stack structure 101 should not be too large or too small. If the distance L1 between the groove 102 and the piezoelectric stack structure 101 is too large, it is easy to cause the groove 102 to play a poor effect of isolating external stress; if the distance L1 between the groove 102 and the piezoelectric stack structure 101 is too small, it is easy to increase the probability of the piezoelectric stack structure 101 in the working area I being damaged. Therefore, in this embodiment, along the direction parallel to the top surface of the substrate 100, the distance L1 between the groove 102 and the piezoelectric stack structure 101 is less than or equal to 100 microns and greater than or equal to 3 microns.

[0041] In other embodiments, the distance between the groove and the piezoelectric stack structure may also be set according to actual design requirements.

[0042] In this embodiment, reference Figures 1 to 3The filter also includes: a first lead electrode (not shown), which is located above the substrate 100 on the side of the piezoelectric stack structure 101, the projection pattern of the first lead electrode on the substrate 100 is staggered with the groove 102, and the first lead electrode is electrically connected to the piezoelectric stack structure 101; a covering layer 108, which covers the substrate 100 and the piezoelectric stack structure 101; a second lead electrode 115, which passes through the covering layer 108 on the first lead electrode and is electrically connected to the first lead electrode.

[0043] It should be noted that, compared with the solution using a single-layer lead electrode, the embodiment of the present invention uses a stacked first lead electrode and a second lead electrode 115 to form a stacked lead electrode, which is beneficial to increase the overall thickness of the lead electrode, thereby reducing the resistance value of the lead electrode, correspondingly reducing the impedance of the lead electrode, and further reducing the characteristic impedance (Z S ).

[0044] The first lead electrode is used to connect the bottom electrode layer and the top electrode layer respectively, and its function is to transmit signals or excite to the filter to generate oscillation or adjust the performance of the filter.

[0045] It should be noted that, since the groove 102 is located around the piezoelectric stack structure 101, the groove 102 is a non-closed structure, so that the projection pattern of the first lead electrode on the substrate 100 can be staggered with the groove 102, thereby ensuring that the first lead electrode can electrically connect the bottom electrode layer and the top electrode layer.

[0046] It should also be noted that, since the groove 102 is located around the piezoelectric stack structure 101, and the projection pattern of the first lead electrode on the substrate 100 is staggered with the groove 102, the width of the first lead electrode near the groove 102 is smaller than the width of the first lead electrode away from the groove 102.

[0047] In this embodiment, the first lead electrode includes: a first sub-lead electrode (not shown), located above the substrate 100 on the side of the bottom electrode layer, and the first sub-lead electrode is electrically connected to the bottom electrode layer; a second sub-lead electrode (not shown), located above the substrate 100 on the side of the top electrode layer, and the second sub-lead electrode is electrically connected to the top electrode layer.

[0048] It should be noted that the first sub-lead electrode is electrically connected to the bottom electrode layer, and the second sub-lead electrode is electrically connected to the top electrode layer. When the filter is working, the first sub-lead electrode and the second sub-lead electrode are used for signal input and output respectively.

[0049] In this embodiment, the first sub-lead electrode and the second sub-lead electrode are made of molybdenum. In other embodiments, the first sub-lead electrode and the second sub-lead electrode may also be made of other types of metal materials, such as copper, gold, tungsten, aluminum, platinum or silver.

[0050] The second lead electrode 115 is used to form a lead electrode of a stacked structure with the first lead electrode.

[0051] In this embodiment, the second lead electrode 115 passes through the covering layer 108 on the first lead electrode and is electrically connected to the first lead electrode, and the second lead electrode 115 covers the top of the first lead electrode. Therefore, the projection pattern of the second lead electrode 115 on the substrate 100 is also staggered with the groove 102, so that the width of the second lead electrode 115 near the groove 102 is smaller than the width of the second lead electrode 115 away from the groove 102.

[0052] In this embodiment, the material of the second lead electrode 115 includes one or more of aluminum, copper, gold, platinum, silver, titanium, tungsten and nickel. It should be noted that aluminum, copper, gold, platinum, silver, titanium, tungsten and nickel all have good electrical conductivity. As an example, the material of the second lead electrode 115 is aluminum.

[0053] In this embodiment, reference Figure 3 The covering layer 108 includes a top acoustic reflection layer 110, and the top acoustic reflection layer 110 includes a plurality of low acoustic impedance reflection layers 111 and a high acoustic impedance reflection layer 112 located between the low acoustic impedance reflection layers 111 of adjacent layers. The low acoustic impedance reflection layer 111 is located at the top of the piezoelectric stack structure 101, the top of the substrate 100 on the side of the piezoelectric stack structure 101, and the top of the first lead electrode, and the high acoustic impedance reflection layer 112 is located at the top of the piezoelectric stack structure 101.

[0054] The top acoustic reflection layer 110 is formed into a Bragg reflection surface by stacking multiple low acoustic impedance reflection layers 111 and high acoustic impedance reflection layers 112 located between the adjacent low acoustic impedance reflection layers 111. At the interface between each low acoustic impedance reflection layer 111 and the high acoustic impedance reflection layer 112, most of the sound waves are reflected, thereby reducing the probability of sound wave leakage, thereby improving the acoustic-to-electrical conversion performance of the filter.

[0055] In this embodiment, the material of the low acoustic impedance reflection layer 111 includes a dielectric material, such as silicon oxide, aluminum nitride or silicon carbide, etc. As an example, the material of the low acoustic impedance reflection layer 111 is silicon oxide.

[0056] In this embodiment, the material of the high acoustic impedance reflection layer 112 includes a metal material, such as tungsten, molybdenum, or platinum, etc. As an example, the material of the high acoustic impedance reflection layer 112 is tungsten.

[0057] In this embodiment, the second lead electrode 115 penetrates through the multiple layers of low acoustic impedance reflective layer 111 on the first lead electrode and is electrically connected to the first lead electrode.

[0058] In this embodiment, the cover layer 108 further includes: a passivation layer 116 located on the top sound reflection layer 110 .

[0059] The passivation layer 116 is used to protect the top sound reflection layer 110 , which helps to prevent the top sound reflection layer 110 from being exposed to the air, thereby reducing the probability of moisture and pollutants in the air adhering to the top sound reflection layer 110 .

[0060] The material of the passivation layer 116 includes one or more of aluminum nitride, silicon carbide, silicon oxide and silicon nitride. As an example, the material of the passivation layer 116 is silicon nitride.

[0061] In this embodiment, the second lead electrode 115 penetrates the passivation layer 116 and the top sound reflection layer 110 on the first lead electrode.

[0062] It should be noted that, since the passivation layer 116 and the top sound reflection layer 110 are both located on the top of the first lead electrode, and the second lead electrode 115 is electrically connected to the first lead electrode, the second lead electrode 115 penetrates the passivation layer 116 and the top sound reflection layer 110; and, since the material of the passivation layer 116 is a dielectric material, isolation between adjacent second lead electrodes 115 can be achieved.

[0063] In other embodiments, the second lead electrode may be formed first, and then the passivation layer may be formed, so that the passivation layer can protect the second lead electrode and prevent the second lead electrode from being exposed to the air.

[0064] In this embodiment, reference Figure 2 The second lead electrode 115 also extends to cover a portion of the top of the covering layer 108 .

[0065] It should be noted that, in the process of forming the second lead electrode 115, an opening is usually formed in the cover layer 108 first, and then a second lead electrode material layer (not shown) covering the cover layer 108 is formed, the second lead electrode material layer is also filled in the second opening, and then the second lead electrode material layer is etched through the patterned mask layer. Since the material layer of the second lead electrode 115 needs to be overetched, by making the second lead electrode 115 also extend to cover part of the top of the cover layer 108, it is easy for the mask layer to cover the side wall of the opening during the overetching process, thereby helping to reduce the probability of the first lead electrode being damaged.

[0066] In this embodiment, continue to refer to Figure 2 , the second lead electrode 115 includes a first portion 118 located in the cover layer 108, and a second portion 119 covering the top of the first portion 118 and part of the top of the cover layer. On the projection plane parallel to the top surface of the substrate 100, the width w3 of the area where the second portion 119 and the first portion 118 do not overlap should not be too small. If the width w3 of the area where the second portion 119 and the first portion 118 do not overlap is too small, when the material layer of the second lead electrode 115 is over-etched, the mask layer is likely to expose the sidewall of the covering opening, thereby easily causing the first lead electrode to be damaged. Therefore, in this embodiment, on the projection plane parallel to the top surface of the substrate 100, the width w3 of the area where the second portion 119 and the first portion 118 do not overlap is greater than or equal to 2 microns.

[0067] In this embodiment, reference Figure 3 The filter further includes: a bottom acoustic reflection layer 113, the structure of the bottom acoustic reflection layer 113 is similar to that of the top acoustic reflection layer 110, and also includes a plurality of low acoustic impedance reflection layers 111 and a high acoustic impedance reflection layer 112 located between the low acoustic impedance reflection layers 111 of adjacent layers, the low acoustic impedance reflection layer 111 is located between the piezoelectric laminated structure 101 and the substrate 100, the high acoustic impedance reflection layer 112 is located at the bottom of the piezoelectric laminated structure 101, between the substrate 100 and the top acoustic reflection layer 110 on the side of the piezoelectric laminated structure 101, and at the bottom of the first lead electrode.

[0068] In this embodiment, reference Figure 1 and Figure 3 The filter further includes: a pad 117 located on the second lead electrode 115 and located at an end position of the second lead electrode 115 away from the piezoelectric stacked structure 101.

[0069] The pad 117 is used to electrically connect the second lead electrode 115 to achieve electrical connection between the second lead electrode 115 and an external circuit.

[0070] In this embodiment, the material of the pad 117 includes one or more of aluminum, copper, gold, titanium, nickel, silver and tungsten. It should be noted that aluminum, copper, gold, titanium, nickel, silver and tungsten all have good electrical conductivity. As an example, the material of the pad 117 is aluminum.

[0071] In this embodiment, reference Figure 4 The filter also includes: a dielectric layer 103, located on the substrate 100 at the side of the working area I and covering the side wall of the piezoelectric stack structure 101; a first opening 104, located in the dielectric layer 103, the first opening 103 is located above the groove 102, and the bottom of the first opening 102 is connected to the top of the groove 102.

[0072] The dielectric layer 103 is a residual film layer remaining in the working area during the process of forming the piezoelectric stack structure 101 and the cover layer 108 in the working area I.

[0073] It should be noted that, in this embodiment, the dielectric layer 103 is a stacked structure. In the process of forming the piezoelectric stacked structure 101 and the covering layer 108 in the working area I, some film layers in the piezoelectric stacked structure 101 and the covering layer 108 are also formed on the side of the working area I.

[0074] The first opening 104 is an initial opening for forming the groove 102 .

[0075] In this embodiment, reference Figure 4 , along a direction parallel to the top surface of the substrate 100, the opening size w2 of the first opening 104 is larger than the opening size w1 of the groove 102, which is beneficial to increasing the process window for forming the groove 102, thereby reducing the difficulty of forming the groove 102, and is also beneficial to increasing the tolerance of the overlay error between the first opening 104 and the groove 102, thereby reducing the process difficulty of forming the groove 102.

[0076] As an example, the difference between the opening size w2 of the first opening 104 and the opening size w1 of the groove 102 is greater than or equal to 2 micrometers.

[0077] In other embodiments, the difference between the opening size of the first opening and the opening size of the groove may be set according to actual design requirements.

[0078] It should be noted that Figure 3 The structures of the piezoelectric stack structure 101 and the cover layer 108 shown are only used as an example. In other embodiments, according to actual conditions, Figure 4 The piezoelectric stack structure 101 and the dielectric layer 103 may also be membrane layers of other structural types.

[0079] In this embodiment, continue to refer to Figure 4 The filter further includes: a support portion 105, which is located on the substrate 100 at the side of the working area I and the groove 102, and is located on the side of the groove 102 away from the working area I, and the support portion 105 surrounds the groove 102; a cap layer 106, which is located on the support portion 105, and the cap layer 106, the support portion 105 and the substrate 100 form a cavity 107.

[0080] The support portion 105 is used to prepare for bonding the cap layer 106 .

[0081] In this embodiment, the material of the support portion 105 includes a photosensitive material.

[0082] It should be noted that the material of the support portion 105 is a photosensitive material, and the support portion 105 can be patterned by a photolithography process later, which is beneficial to reducing the process complexity and process accuracy of the patterning process. Specifically, the photosensitive material is a dry film. The dry film is a permanent bonding film, and the bonding strength of the dry film is high, so that the bonding strength between the support portion 105 and the substrate 100 and the cap layer 106 is guaranteed, and at the same time, it is beneficial to improve the sealing of the cavity.

[0083] In other embodiments, the material of the support portion may also be a non-photosensitive material, and a photolithography process including coating photoresist, exposure and development may be used to form a photoresist mask (not shown), and the non-photosensitive material may be etched through the photoresist mask and a dry etching process to form the support portion. The dry etching process has anisotropic etching characteristics, which is beneficial to improving the morphology quality and dimensional accuracy of the support portion, and the dry etching process may be a plasma dry etching process. Accordingly, after the support portion is formed, it also includes: removing the photoresist mask by a wet degumming or ashing process.

[0084] The cap layer 106 is used to enclose a cavity 107 together with the support portion 105 and the substrate 100 .

[0085] It should be noted that the cavity 107 is helpful to reduce the vibration energy loss of the filter, thereby improving the acoustic-to-electrical conversion performance of the filter.

[0086] In this embodiment, the material of the capping layer 106 is silicon. In other embodiments, the material of the capping layer includes one or more of germanium, silicon germanium, silicon carbide, silicon germanium carbide, indium arsenide, gallium arsenide and indium phosphide, and the capping layer can also be a ceramic capping layer, a quartz capping layer or a glass capping layer or other types of capping layers.

[0087] Correspondingly, the present invention also provides a method for forming a filter. Figures 5 to 24It is a structural schematic diagram corresponding to each step in an embodiment of a method for forming a filter of the present invention.

[0088] refer to Figures 5 to 7 , Figure 6 It is a top view. Figure 7 yes Figure 6 A cross-sectional view along the AA1 direction is provided, wherein a substrate 500 is provided, wherein the substrate 500 includes a working area i, and a piezoelectric stack structure 501 (such as Figure 6 and Figure 7 shown).

[0089] in, Figure 6 Only the electrode layers and the first lead electrode of the piezoelectric stack structure are illustrated.

[0090] The substrate 500 is used to provide a process platform for forming a bulk acoustic wave filter. A BAW filter is a special filtering device made by utilizing the piezoelectric effect and the physical characteristics of the propagation of acoustic bulk waves. In a BAW filter, the acoustic wave mainly propagates in the vertical direction inside the filter. BAW filters have the advantages of high operating frequency, high quality factor (Q value), good temperature stability and high frequency characteristic consistency, and therefore are widely used in various electronic devices.

[0091] In this embodiment, the material of the substrate 500 is silicon. In other embodiments, the material of the substrate includes one or more of germanium, silicon germanium, silicon carbide, silicon germanium carbide, indium arsenide, gallium arsenide, and indium phosphide. The substrate may also be a ceramic substrate, a quartz substrate, a glass substrate, or other types of substrates.

[0092] It should be noted that the working area i refers to the effective resonance area, that is, the area that can store and release energy, which is mainly used to maintain oscillation, that is, store and transmit energy so that the filter can maintain the stability of amplitude and frequency.

[0093] The piezoelectric stacked structure 501 is used to prepare for the subsequent formation of a filter. The corresponding piezoelectric stacked structure 501 is used to realize the mutual conversion between the electrical signal and the acoustic signal, so that the filter performs filtering processing on the signal.

[0094] Specifically, Figure 7 As shown, the piezoelectric stack structure 501 includes a bottom electrode layer (not labeled) located on the substrate 500, a piezoelectric layer (not labeled) located on the bottom electrode layer, and a top electrode layer (not labeled) located on the piezoelectric layer.

[0095] The material of the bottom electrode layer is a conductive material. The conductive material may be a metal material with conductive properties, such as one or more of molybdenum, aluminum, copper, platinum, gold, iridium, osmium, rhenium, palladium, rhodium, ruthenium and tungsten. As an example, the material of the bottom electrode layer is molybdenum.

[0096] It can be understood that, in other embodiments, the material of the bottom electrode layer may also be other electrode materials suitable for forming a piezoelectric stack structure.

[0097] The material of the piezoelectric layer is piezoelectric material, which is a crystalline material that will generate voltage between the two end surfaces when subjected to pressure. Piezoelectric material has a piezoelectric effect. The piezoelectric effect of piezoelectric material can be used to realize the mutual conversion between mechanical vibration (sound waves) and alternating current, thereby realizing the conversion of sound energy into electrical energy.

[0098] The material of the piezoelectric layer may be a piezoelectric crystal, a piezoelectric ceramic or a piezoelectric polymer, etc. The piezoelectric crystal may be aluminum nitride, lead zirconate titanate, quartz crystal, lithium gallate, lithium germanate, titanium germanate, lithium niobate or lithium tantalate, etc., and the piezoelectric polymer may be polyvinylidene fluoride, vinylidene fluoride-trifluoroethylene copolymer, nylon-11 or vinylene dicyano-vinyl acetate alternating copolymer, etc.

[0099] In this embodiment, the piezoelectric layer may be formed by using deposition processes such as chemical vapor deposition, physical vapor deposition or atomic layer deposition.

[0100] The material of the top electrode layer is a conductive material. The conductive material may be a metal material with conductive properties, such as one or more of molybdenum, aluminum, copper, platinum, gold, iridium, osmium, rhenium, palladium, rhodium, ruthenium and tungsten. As an example, the material of the top electrode layer is molybdenum.

[0101] It can be understood that, in other embodiments, the material of the top electrode layer may also be other electrode materials suitable for forming a piezoelectric stack structure.

[0102] Continue to refer Figure 6 to Figure 7 In the step of providing the substrate 500, a first lead electrode 514 (such as Figure 6 As shown), the first lead electrode 514 is electrically connected to the piezoelectric stack structure 501.

[0103] The first lead electrode 514 is used to connect the bottom electrode layer and the top electrode layer respectively, and its function is to transmit signals or excite to the filter to generate oscillation or adjust the performance of the filter.

[0104] It should be noted that, since the groove formed subsequently is located around the piezoelectric stack structure 501, and the projection pattern of the first lead electrode 514 on the substrate 500 is staggered with the groove, the width of the first lead electrode 514 near the groove is smaller than the width of the first lead electrode 514 far from the groove.

[0105] In this embodiment, the first lead electrode 514 includes: a first sub-lead electrode (not marked), located above the substrate 500 on the side of the bottom electrode layer, and the first sub-lead electrode is electrically connected to the bottom electrode layer; a second sub-lead electrode (not marked), located above the substrate 500 on the side of the top electrode layer, and the second sub-lead electrode is electrically connected to the top electrode layer.

[0106] It should be noted that the first sub-lead electrode is electrically connected to the bottom electrode layer, and the second sub-lead electrode is electrically connected to the top electrode layer. When the filter is working, the first sub-lead electrode and the second sub-lead electrode are used for signal input and output respectively.

[0107] In this embodiment, the first sub-lead electrode and the second sub-lead electrode are made of molybdenum. In other embodiments, the first sub-lead electrode and the second sub-lead electrode may also be made of other types of metal materials, such as copper, gold, tungsten, aluminum, platinum or silver.

[0108] In this embodiment, reference Figure 6 , the step of providing the substrate 500 also includes: forming a bottom acoustic reflection layer 513 on the top of the substrate 500, the structure of the bottom acoustic reflection layer 513 is similar to the structure of the top acoustic reflection layer formed subsequently, and also includes a plurality of low acoustic impedance reflection layers 511 and a high acoustic impedance reflection layer 512 located between the low acoustic impedance reflection layers 511 of adjacent layers, the low acoustic impedance reflection layer 511 is located between the piezoelectric stack structure 501 and the substrate 500, the high acoustic impedance reflection layer 512 is located at the bottom of the piezoelectric stack structure 501, between the substrate 500 and the top acoustic reflection layer on the side of the piezoelectric stack structure 501, and at the bottom of the first lead electrode.

[0109] refer to Figures 8 to 9 , Figure 8 is a top view of the forming covering layer, Fig. 9 yes Figure 8 In the cross-sectional view along the AA1 direction, after forming the first lead electrode 514 , the forming method further includes: forming a covering layer 508 covering the substrate 500 , the piezoelectric stacked structure 501 and the first lead electrode 514 .

[0110] In this embodiment, the cover layer 508 is a laminated structure. Specifically, the cover layer 508 includes a top sound reflection layer 510 and a passivation layer 516 located on the top of the top sound reflection layer 510 .

[0111] In this embodiment, reference Fig. 9In the step of forming a covering layer 508 covering the substrate 500 and the piezoelectric stack structure 501, the covering layer 508 includes a top acoustic reflection layer 510, and the top acoustic reflection layer 510 includes a plurality of low acoustic impedance reflection layers 511 and a high acoustic impedance reflection layer 512 located between the low acoustic impedance reflection layers 511 of adjacent layers, the low acoustic impedance reflection layer 511 is located at the top of the piezoelectric stack structure 501, the top of the substrate 500 on the side of the piezoelectric stack structure 501, and the top of the first lead electrode 514, and the high acoustic impedance reflection layer 512 is located at the top of the piezoelectric stack structure 501.

[0112] The top acoustic reflection layer 510 is formed into a Bragg reflection surface by stacking multiple low acoustic impedance reflection layers 511 and high acoustic impedance reflection layers 512 located between the adjacent low acoustic impedance reflection layers 511. At the interface between each low acoustic impedance reflection layer 511 and the high acoustic impedance reflection layer 512, most of the sound waves are reflected, thereby reducing the probability of sound wave leakage, thereby improving the acoustic-to-electrical conversion performance of the filter.

[0113] In this embodiment, the material of the low acoustic impedance reflection layer 511 includes a dielectric material, such as silicon oxide, aluminum nitride or silicon carbide, etc. As an example, the material of the low acoustic impedance reflection layer 511 is silicon oxide.

[0114] In this embodiment, the material of the high acoustic impedance reflection layer 512 includes a metal material, such as tungsten, molybdenum, or platinum, etc. As an example, the material of the high acoustic impedance reflection layer 512 is tungsten.

[0115] In this embodiment, continue to refer to Fig. 9 In the step of forming a covering layer 508 covering the substrate 500 and the piezoelectric stack structure 501 , the covering layer 508 further includes a passivation layer 516 covering the top acoustic reflection layer 510 .

[0116] The passivation layer 516 is used to protect the top sound reflection layer 510 , which helps to prevent the top sound reflection layer 510 from being exposed to the air, thereby reducing the probability of moisture and pollutants in the air adhering to the top sound reflection layer 510 .

[0117] The material of the passivation layer 516 includes one or more of aluminum nitride, silicon carbide, silicon oxide and silicon nitride. As an example, the material of the passivation layer 516 is silicon nitride.

[0118] refer to Figures 10 to 17 , Fig.10 is a top view of forming a second opening in the cover layer, Fig.11 yes Fig.10 Cross-sectional view along AA1 direction, Fig.12 is a top view of a second lead electrode material layer formed to cover the covering layer, Fig.13 yes Fig.12 Cross-sectional view along AA1 direction, Fig.14 is a top view of a second mask layer that forms a pattern, Fig.15 yes Fig.14 A local enlarged view at E. Fig.16 is a top view of forming a second lead electrode, Fig.17 yes Fig.16 In the cross-sectional view along the AA1 direction, after the covering layer 508 is formed, a second lead electrode 515 (eg, Figure 16 to Figure 17 shown).

[0119] It should be noted that, compared with the solution using a single-layer lead electrode, the embodiment of the present invention uses a stacked first lead electrode 514 and a second lead electrode 515 to form a lead electrode of a laminated structure, which is beneficial to increasing the overall thickness of the lead electrode, thereby reducing the resistance value of the lead electrode, and correspondingly reducing the impedance of the lead electrode, thereby reducing the characteristic impedance of the filter.

[0120] Specifically, the step of forming the second lead electrode 515 that penetrates the cover layer 508 on the first lead electrode 514 and is electrically connected to the first lead electrode 514 includes: referring to Figure 10 to Figure 11 , forming a second opening 518 in the cover layer 508, wherein the second opening 518 exposes a portion of the top of the first lead electrode 514; Figure 12 to Figure 13 , forming a second lead electrode material layer 519 covering the cover layer 508, and the second lead electrode material layer 519 is also filled in the second opening 518; Figure 14 to Figure 15 , forming a patterned second mask layer 520 on the second lead electrode material layer 519, wherein the projection of the second mask layer 520 on the cover layer 508 covers the second opening 518, and also extends to cover the top of the cover layer 508 in a partial width area adjacent to the second opening 518; Figure 16 to Figure 17 , using the second mask layer 520 as a mask, remove the second lead electrode material layer 519 exposed by the second mask layer 520, and retain the second lead electrode material layer 519 in the second opening 518 and the second lead electrode material layer 519 located on the top of the portion of the covering layer as the second lead electrode 515.

[0121] The second opening 518 is used to provide a space for forming the second lead electrode 515 .

[0122] The second lead electrode material layer 519 is used to form the second lead electrode 515 .

[0123] The second mask layer 520 is used as a mask for forming the second lead electrode 515 .

[0124] It should be noted that, in the process of forming the second lead electrode 515, the second opening 518 is usually formed in the cover layer 508 first, and then the second lead electrode material layer 519 covering the cover layer 508 is formed, and the second lead electrode material layer 519 is also filled in the second opening 518, and then the second lead electrode material layer 519 is etched through the patterned second mask layer 520. Since the material layer of the second lead electrode 515 needs to be overetched, the projection of the second mask layer 520 on the cover layer 508 covers the second opening 518, and also extends to cover the top of the cover layer 508 of the partial width area adjacent to the second opening 518, so that during the overetching process, the second mask layer 520 can easily cover the side wall of the second opening 518, thereby helping to reduce the probability of the first lead electrode 514 being damaged.

[0125] In this embodiment, reference Fig.14 , the width W3 of the projection of the second mask layer 520 on the cover layer 508 extending to cover the partial width area of ​​the top of the cover layer 508 adjacent to the second opening 518 should not be too small. If the width W3 of the projection of the second mask layer 520 on the cover layer 508 extending to cover the partial width area of ​​the top of the cover layer 508 adjacent to the second opening 518 is too small, when the second lead electrode material layer 519 is over-etched, the second mask layer 520 is likely to expose the sidewall of the second opening 518, thereby easily damaging the first lead electrode 514. Therefore, in this embodiment, the width W3 of the projection of the second mask layer 520 on the cover layer 508 extending to cover the partial width area of ​​the top of the cover layer 508 adjacent to the second opening 518 is greater than or equal to 2 microns.

[0126] In this embodiment, the second lead electrode 515 penetrates the covering layer 508 on the first lead electrode 514 and is electrically connected to the first lead electrode 514, and the second lead electrode 515 covers the top of the first lead electrode 514. Therefore, the projection pattern of the second lead electrode 515 on the substrate 500 is also aligned with the groove 502 (such as Fig. 22 The second lead electrodes 515 are staggered as shown, so that the width of the second lead electrodes 515 near the groove 502 is smaller than the width of the second lead electrodes 515 far from the groove 502.

[0127] In this embodiment, the material of the second lead electrode 515 includes one or more of aluminum, copper, gold, platinum, silver, titanium, tungsten and nickel. It should be noted that aluminum, copper, gold, platinum, silver, titanium, tungsten and nickel all have good electrical conductivity. As an example, the material of the second lead electrode 515 is aluminum.

[0128] In this embodiment, in the step of forming the second lead electrode 515 , the second lead electrode 515 penetrates through the multi-layer low acoustic impedance reflective layer 511 on the first lead electrode 514 and is electrically connected to the first lead electrode 514 .

[0129] In this embodiment, in the step of forming the second lead electrode 515 , the second lead electrode 515 penetrates the passivation layer 516 and the top sound reflection layer 510 on the first lead electrode 514 .

[0130] It should be noted that, since the passivation layer 516 and the top sound reflection layer 510 are both located on the top of the first lead electrode 514, and the second lead electrode 515 is electrically connected to the first lead electrode 514, the second lead electrode 515 penetrates the passivation layer 516 and the top sound reflection layer 510; and, since the material of the passivation layer 516 is a dielectric material, isolation between the second lead electrodes 515 can be achieved.

[0131] In other embodiments, the second lead electrode may be formed first, and then the passivation layer may be formed, so that the passivation layer can protect the second lead electrode and prevent the second lead electrode from being exposed to the air.

[0132] refer to Figure 18 to Figure 19 , Fig.18 is a top view of a pad formed on the second lead, Fig.19 yes Fig.18 The cross-sectional view along the AA1 direction, after forming the second lead electrode 515 and before forming the groove in the substrate 500 on the side of the working area i, also includes: forming a solder pad 517 on the second lead electrode 515, and the solder pad 517 is located at the end position of the second lead electrode 515 away from the side of the piezoelectric stack structure 501.

[0133] The pad 517 is used to electrically connect the second lead electrode 515 to achieve electrical connection between the second lead electrode 515 and an external circuit.

[0134] In this embodiment, the material of the pad 517 includes one or more of aluminum, copper, gold, titanium, nickel, silver and tungsten. It should be noted that aluminum, copper, gold, titanium, nickel, silver and tungsten all have good electrical conductivity. As an example, the material of the pad 517 is aluminum.

[0135] For the convenience of illustration, Figure 20 to Figure 24is a simple schematic diagram. Specifically, Fig. 20 yes Fig.18 Cross-sectional view along AA2 direction, Fig.21 is based on Fig. 20 A cross-sectional view after the first opening is formed, Fig. 22 is based on Fig.21 Cross-sectional view after the groove is formed, Fig.23 is based on Fig. 22 A cross-sectional view after forming the support portion, the cap layer and the cavity, Fig.24 is based on Fig.23 Cross-sectional view of the substrate after thinning.

[0136] refer to Fig. 20 , Fig. 20 yes Fig.18 In the cross-sectional view along the AA2 direction, in this embodiment, a dielectric layer 503 is formed on the substrate 500 at the side of the working area i, and the dielectric layer 503 covers the side wall of the piezoelectric stack structure 501.

[0137] The dielectric layer 503 is a residual film layer remaining in the working area i during the process of forming the piezoelectric stack structure 501 and the cover layer 508 in the working area i.

[0138] It should be noted that, in this embodiment, the dielectric layer 503 is a stacked structure. During the process of forming the piezoelectric stacked structure 501 and the covering layer 508 in the working area i, part of the film layers in the piezoelectric stacked structure 501 and the covering layer 508 are also formed on the side of the working area i.

[0139] refer to Fig.21 In this embodiment, after forming a pad 517 on the second lead electrode 515 and before forming a groove in the substrate 500 on the side of the working area i, it also includes: forming a first opening 504 in the dielectric layer 503 on the side of the working area i, and the first opening 504 is located around the piezoelectric stack structure 501.

[0140] The first opening 504 is an initial opening for subsequently forming a groove.

[0141] refer to Fig. 22 A groove 502 is formed in the substrate 500 at the side of the working area i, and the groove 502 is located around the piezoelectric stack structure 501.

[0142] It should be noted that, since the groove 502 is located around the piezoelectric stack structure 501, the groove 502 can effectively isolate external stress and reduce the probability of external stress being transmitted to the working area i, which can correspondingly reduce the probability of warping of the piezoelectric stack structure 501, thereby reducing the probability of frequency hopping of the filter.

[0143] In this embodiment, in the step of forming the groove 502 , the groove 502 is formed in the substrate 500 along the bottom of the first opening 504 , and the bottom of the first opening 504 is connected to the top of the groove 502 .

[0144] It should be noted that, along the direction parallel to the top surface of the substrate 500, the opening size W2 of the first opening 504 is larger than the opening size W1 of the groove 502, which is beneficial to increasing the process window for forming the groove 502, thereby reducing the difficulty of forming the groove 502, and is also beneficial to increasing the tolerance of the overlay error between the first opening 504 and the groove 502, thereby reducing the process difficulty of forming the groove 502.

[0145] As an example, the difference between the opening size W2 of the first opening 504 and the opening size W1 of the groove 502 is greater than or equal to 2 micrometers.

[0146] In other embodiments, the difference between the opening size of the first opening and the opening size of the groove may be set according to actual design requirements.

[0147] Specifically, the step of forming the groove 504 in the substrate 500 at the side i of the working area includes: forming a first mask layer (not shown) covering the sidewall of the first opening 504, the first mask layer also covering the substrate 500, the dielectric layer 503 and the piezoelectric stack structure 501 outside the first opening 504, and exposing a portion of the bottom of the first opening 504; Fig. 22 Using the first mask as a mask, a portion of the thickness of the substrate 500 is removed along the exposed bottom of the first opening 504 to form a groove 502 .

[0148] The first mask layer is used as a mask for forming the groove 502 .

[0149] In this embodiment, the material of the first mask layer includes photoresist. Photoresist has high resolution, so the opening size of the groove 502 can be accurately controlled; moreover, the use of photoresist reduces the complexity of forming the groove 502, and at the same time, the photoresist is easy to be removed, thereby reducing the complexity of the process and improving the production efficiency. In other embodiments, the first mask layer can also be made of other materials that can be used as an etching mask and are easy to be removed.

[0150] It should be noted that the above processes are photolithography and etching processes, which are compatible with the existing technology, thereby helping to reduce the difficulty of forming the groove 502 .

[0151] As an example, the process for forming the groove 502 is a deep silicon etching process. It should be noted that the deep silicon etching process is anisotropic and has a relatively high etching selectivity, so it is beneficial to improve the morphology quality and aspect ratio of the groove 502.

[0152] In this embodiment, after the groove 502 is formed, the step further includes: removing the first mask layer.

[0153] As an example, the first mask layer is removed by an ashing process.

[0154] In this embodiment, after the second lead electrode 515 is formed, a groove 502 is formed in the substrate 500 on the side of the working area i. The groove 502 is a non-closed structure, and the groove 502 and the projection pattern of the first lead electrode 514 on the substrate 500 are staggered.

[0155] It should be noted that, since the groove 502 is located around the piezoelectric stack structure 501, the groove 502 is a non-closed structure, so that the projection pattern of the first lead electrode 514 on the substrate 500 can be staggered with the groove 502, thereby ensuring that the first lead electrode 514 can electrically connect the bottom electrode layer and the top electrode layer.

[0156] In this embodiment, the opening size W1 of the groove 502 should not be too small along the direction parallel to the top surface of the substrate 500. If the opening size W1 of the groove 502 is too small, on the one hand, the groove 502 may not be able to isolate the external stress effectively, and on the other hand, it may increase the difficulty of forming the groove 502. Therefore, in this embodiment, along the direction parallel to the top surface of the substrate 500, the opening size W1 of the groove 502 is greater than or equal to 3 microns.

[0157] In this embodiment, along the direction parallel to the top surface of the substrate 500, the distance l1 between the groove 502 and the piezoelectric stack structure 501 should not be too large or too small. If the distance l1 between the groove 502 and the piezoelectric stack structure 501 is too large, it is easy to cause the groove 502 to play a poor effect of isolating external stress; if the distance l1 between the groove 502 and the piezoelectric stack structure 501 is too small, it is easy to increase the probability of the piezoelectric stack structure 501 in the working area i being damaged. Therefore, in this embodiment, along the direction parallel to the top surface of the substrate 500, the distance l1 between the groove 502 and the piezoelectric stack structure 501 is less than or equal to 100 microns and greater than or equal to 3 microns.

[0158] In other embodiments, the distance between the groove and the piezoelectric stack structure may also be set according to actual design requirements.

[0159] refer to Fig.23 After the groove 502 is formed in the substrate 500 on the side of the working area i, it also includes: forming a supporting portion 505 on the substrate 500 on the side of the working area i and the groove 502, the supporting portion 505 is located on the side of the groove 502 away from the working area i, and the supporting portion 505 surrounds the groove 502.

[0160] The support portion 505 is used to prepare for bonding the cap layer.

[0161] In this embodiment, the material of the support portion 505 includes a photosensitive material.

[0162] It should be noted that the material of the support portion 505 is a photosensitive material, and the support portion 505 can be patterned by a photolithography process later, which is conducive to reducing the process complexity and process accuracy of the patterning process. Specifically, the photosensitive material is a dry film. The dry film is a permanent bonding film, and the bonding strength of the dry film is high, so that the bonding strength between the support portion 505 and the substrate 500 and the cap layer is guaranteed, and at the same time, it is conducive to improving the sealing of the cavity.

[0163] In other embodiments, the material of the support portion may also be a non-photosensitive material, and a photolithography process including coating photoresist, exposure and development may be used to form a photoresist mask (not shown), and the non-photosensitive material may be etched through the photoresist mask and a dry etching process to form the support portion. The dry etching process has anisotropic etching characteristics, which is beneficial to improving the morphology quality and dimensional accuracy of the support portion, and the dry etching process may be a plasma dry etching process. Accordingly, after the support portion is formed, it also includes: removing the photoresist mask by a wet degumming or ashing process.

[0164] Continue to refer Fig.23 A capping layer 506 is formed on the support portion 505 , and the capping layer 506 , the support portion 505 and the substrate 500 form a cavity 507 .

[0165] It should be noted that the cavity 507 is helpful to reduce the vibration energy loss of the filter, thereby improving the acoustic-to-electrical conversion performance of the filter.

[0166] In this embodiment, the material of the capping layer 506 is silicon. In other embodiments, the material of the capping layer includes one or more of germanium, silicon germanium, silicon carbide, silicon germanium carbide, indium arsenide, gallium arsenide and indium phosphide, and the capping layer can also be a ceramic capping layer, a quartz capping layer or a glass capping layer or other types of capping layers.

[0167] refer to Fig.24After forming the cap layer 506 on the support portion 505 , the method further includes: performing a thinning process on the substrate 500 .

[0168] It should be noted that thinning the substrate 500 is beneficial to reducing the ratio of the depth of the groove 502 to the thickness of the substrate 500, thereby more effectively improving the effect of the groove 502 in isolating the stress between the piezoelectric stack structure 501 and the external semiconductor device.

[0169] It should also be noted that the substrate 500 may be thinned by a grinding or etching process, wherein the etching process includes a wet etching process or a dry etching process, wherein the dry etching process is preferably used.

[0170] In this embodiment, the ratio of the depth H of the groove 502 to the thickness T of the remaining substrate 500 should not be too small. If the ratio of the depth H of the groove 502 to the thickness T of the substrate 500 is too small, that is, when the thickness T of the substrate 500 remains unchanged, the depth H of the groove 502 is too small, which makes it easy for the groove 502 to play a poor role in isolating external stress. Therefore, in this embodiment, the ratio of the depth H of the groove 502 to the thickness T of the substrate 500 is greater than or equal to 1 / 3.

[0171] The filter of the embodiment of the present invention may be formed by the method for forming the filter of the aforementioned embodiment, or may be formed by other methods for forming filters, which will not be described in detail in this embodiment.

[0172] Correspondingly, an embodiment of the present invention further provides an electronic device, and the electronic device includes the filter of the above embodiment.

[0173] The filter can be assembled into various electronic devices. From the above analysis, it can be seen that the probability of frequency hopping of the filter is reduced, which can correspondingly obtain electronic devices with high reliability. Among them, the electronic devices can also be personal computers, mobile terminals such as smart phones, media players, navigation devices, electronic game devices, game controllers, tablet computers, wearable devices, anti-access electronic systems, POS terminals, medical equipment, flight simulators, etc.

[0174] For a detailed description of the filter in the electronic device, reference may be made to the relevant description in the aforementioned embodiment, which will not be repeated here.

[0175] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A filter, characterized in that: include: a substrate, the substrate comprising a working area; A piezoelectric stack structure is located on the substrate of the working area; A groove is located in the base at the side of the working area and around the piezoelectric stack structure.

2. The filter according to claim 1, characterized in that Along a direction parallel to the top surface of the substrate, an opening size of the groove is greater than or equal to 3 micrometers.

3. The filter according to claim 1, characterized in that The ratio of the depth of the groove to the thickness of the substrate is greater than or equal to 1 / 3.

4. The filter according to claim 1, characterized in that Along a direction parallel to the top surface of the substrate, a distance between the groove and the piezoelectric stack structure is greater than or equal to 3 micrometers.

5. The filter according to claim 1, characterized in that The groove is a non-enclosed structure, and the filter further comprises: A first lead electrode is located above the substrate at the side of the piezoelectric stack structure, the projection pattern of the first lead electrode on the substrate is staggered with the groove, and the first lead electrode is electrically connected to the piezoelectric stack structure; A covering layer, covering the substrate and the piezoelectric stack structure; The second lead electrode penetrates the cover layer on the first lead electrode and is electrically connected to the first lead electrode.

6. The filter according to claim 5, characterized in that The cover layer includes a top acoustic reflective layer, the top acoustic reflective layer includes a plurality of low acoustic impedance reflective layers and a high acoustic impedance reflective layer located between the low acoustic impedance reflective layers of adjacent layers, the low acoustic impedance reflective layer is located on the top of the piezoelectric stack structure, the top of the substrate at the side of the piezoelectric stack structure, and the top of the first lead electrode, and the high acoustic impedance reflective layer is located on the top of the piezoelectric stack structure; The second lead electrode penetrates through the multiple low acoustic impedance reflective layers on the first lead electrode and is electrically connected to the first lead electrode.

7. The filter according to claim 6, characterized in that The cover layer further comprises: a passivation layer, located on the top sound reflection layer; The second lead electrode penetrates the passivation layer and the top sound reflection layer on the first lead electrode.

8. The filter according to claim 5, characterized in that The filter further includes: a pad located on the second lead electrode and at an end of the second lead electrode away from the piezoelectric stacked structure.

9. The filter according to claim 8, characterized in that The material of the pad includes one or more of aluminum, copper, gold, titanium, nickel, silver and tungsten.

10. The filter according to claim 5, characterized in that The material of the second lead electrode includes one or more of aluminum, copper, gold, platinum, silver, titanium, tungsten and nickel.

11. The filter according to claim 5, characterized in that The second lead electrode also extends to cover a portion of the top of the cover layer.

12. The filter according to claim 11, characterized in that The second lead electrode includes a first part located in the covering layer, and a second part covering the top of the first part and part of the top of the covering layer. On a projection plane parallel to the top surface of the substrate, a width of an area where the second part and the first part do not overlap is greater than or equal to 2 microns.

13. The filter according to claim 5, characterized in that The piezoelectric stack structure includes a bottom electrode layer located on the substrate, a piezoelectric layer located on the bottom electrode layer, and a top electrode layer located on the piezoelectric layer; The first lead electrode includes: a first sub-lead electrode, located above the substrate at the side of the bottom electrode layer, and the first sub-lead electrode is electrically connected to the bottom electrode layer; a second sub-lead electrode, located above the substrate at the side of the top electrode layer, and the second sub-lead electrode is electrically connected to the top electrode layer.

14. The filter according to claim 1, characterized in that The filter further comprises: a dielectric layer, which is located on the substrate at the side of the working area and covers the side wall of the piezoelectric stack structure; The first opening is located in the dielectric layer, the first opening is located above the groove, and the bottom of the first opening is connected to the top of the groove.

15. The filter according to claim 14, characterized in that Along a direction parallel to the top surface of the substrate, an opening size of the first opening is larger than an opening size of the groove.

16. The filter according to claim 15, characterized in that A difference between an opening size of the first opening and an opening size of the groove is greater than or equal to 2 micrometers.

17. The filter according to claim 1, characterized in that The filter further comprises: a support portion, located on the substrate at the working area and the side of the groove, and located at a side of the groove away from the working area, the support portion surrounding the groove; The cap layer is located on the support portion, and the cap layer, the support portion and the base form a cavity.

18. A method for forming a filter, characterized in that: include: Providing a substrate, the substrate comprising a working area, and a piezoelectric stack structure is formed on the substrate of the working area; A groove is formed in the substrate at the side of the active area, the groove being located around the piezoelectric stack structure.

19. The method for forming a filter according to claim 18, wherein: In the step of providing a substrate, a dielectric layer is formed on the substrate at the side of the working area, and the dielectric layer covers the side wall of the piezoelectric stack structure; Before forming the groove in the substrate at the side of the working area, the method further includes: forming a first opening in the dielectric layer at the side of the working area, wherein the first opening is located around the piezoelectric stack structure; In the step of forming the groove, a groove is formed in the substrate along the bottom of the first opening, and the bottom of the first opening is connected to the top of the groove.

20. The method for forming a filter according to claim 19, wherein: The step of forming a groove in the substrate at the side of the working area includes: forming a first mask layer covering the sidewall of the first opening, the first mask layer also covering the substrate, the dielectric layer and the piezoelectric stack structure outside the first opening, and exposing a portion of the bottom of the first opening; Using the first mask as a mask, removing a portion of the thickness of the substrate along the exposed bottom of the first opening to form a groove; The forming method further includes: removing the first mask layer.

21. The method for forming a filter according to claim 18, wherein: In the step of providing the substrate, a first lead electrode is further formed above the substrate on the side of the piezoelectric stack structure, and the first lead electrode is electrically connected to the piezoelectric stack structure; After forming the first lead electrode, the forming method further comprises: forming a covering layer covering the substrate, the piezoelectric stack structure and the first lead electrode; After forming the covering layer, forming a second lead electrode penetrating the covering layer on the first lead electrode and electrically connected to the first lead electrode; After forming the second lead electrode, a groove is formed in the substrate at the side of the working area, the groove is a non-closed structure, and the groove is staggered with the projection pattern of the first lead electrode on the substrate.

22. The method for forming a filter according to claim 21, wherein: The step of forming a second lead electrode penetrating the cover layer on the first lead electrode and electrically connected to the first lead electrode comprises: forming a second opening in the cover layer, wherein the second opening exposes a portion of the top of the first lead electrode; forming a second lead electrode material layer covering the cover layer, wherein the second lead electrode material layer is also filled in the second opening; forming a patterned second mask layer on the second lead electrode material layer, wherein a projection of the second mask layer on the cover layer covers the second opening and also extends to cover a top portion of the cover layer adjacent to a partial width region of the second opening; Using the second mask layer as a mask, the second lead electrode material layer exposed by the second mask layer is removed, and the second lead electrode material layer in the second opening and the second lead electrode material layer located on a partial top of the covering layer are retained as the second lead electrode.

23. The method for forming a filter according to claim 21, wherein: In the step of forming a covering layer covering the substrate, the piezoelectric stacked structure and the first lead electrode, the covering layer includes a top acoustic reflection layer, the top acoustic reflection layer includes a plurality of low acoustic impedance reflection layers and a high acoustic impedance reflection layer located between the low acoustic impedance reflection layers of adjacent layers, the low acoustic impedance reflection layer is located on the top of the piezoelectric stacked structure, the top of the substrate at the side of the piezoelectric stacked structure and the top of the first lead electrode, and the high acoustic impedance reflection layer is located on the top of the piezoelectric stacked structure; In the step of forming the second lead electrode, the second lead electrode penetrates through the multiple low acoustic impedance reflective layers on the first lead electrode and is electrically connected to the first lead electrode.

24. The method for forming a filter according to claim 23, wherein: In the step of forming a covering layer covering the substrate, the piezoelectric stack structure and the first lead electrode, the covering layer further comprises a passivation layer covering the top acoustic reflection layer; In the step of forming the second lead electrode, the second lead electrode penetrates the passivation layer and the top sound reflection layer on the first lead electrode.

25. The method for forming a filter according to claim 21, wherein: After forming the second lead electrode and before forming the groove in the substrate at the side of the working area, the method further includes: A pad is formed on the second lead electrode, and the pad is located at an end of the second lead electrode away from the piezoelectric stacked structure.

26. The method for forming a filter according to claim 18, wherein: After forming the groove in the substrate at the side of the working area, the method further includes: forming a support portion on the substrate at the working area and the side of the groove, the support portion being located at a side of the groove away from the working area, and the support portion surrounding the groove; A cap layer is formed on the support portion, and the cap layer, the support portion and the base form a cavity.

27. The method for forming a filter according to claim 26, wherein: After forming the cap layer on the support portion, the method further includes: performing a thinning process on the substrate.

28. An electronic device, characterized in that: Comprising a filter as claimed in any one of claims 1 to 17.

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