Implementation of RF filters

Abstract

Implementation of RF filters The present description relates to a device comprising first (12) and second (14) filters, the first filter (12) comprising a first region (20) made of a first piezoelectric material, the second filter (14) comprising a second region (22) made of a second piezoelectric material, the first and second materials being different and the first (20) and second (22) regions being on the same substrate. Figure for abstract: Fig. 1

Description

Title of the invention: Implementation of RF filters Technical field

[0001] The present description relates generally to electronic devices and more specifically to electronic devices comprising filters and their manufacturing methods. Prior art

[0002] Piezoelectricity is the property that certain materials have of becoming electrically polarized under the action of mechanical stress (direct piezoelectric effect) and conversely of deforming when an electric field is applied to them (inverse piezoelectric effect).

[0003] This effect is used in many applications. In particular, piezoelectricity is used in filters, for example surface acoustic wave (SAW) filters or bulk acoustic wave (BAW) filters. Summary of the invention

[0004] One embodiment provides a device comprising first and second filters, the first filter comprising a first region of a first piezoelectric material, the second filter comprising a second region of a second piezoelectric material, the first and second materials being different and the first and second regions being on a same substrate.

[0005] According to one embodiment, the first and second filters are of the same type.

[0006] According to one embodiment, the first and second filters are wave filters surface acoustics, bulk acoustic wave filters, or Lamb wave filters.

[0007] According to one embodiment, the first and second materials are among LiNbO3, LiTaO3, Lil-xNbxO3, AIN, All-xScxN, KTal-xNbxO3 and have an orientation among: X-, Y-, Y+30°-, Y+36°-, Y+38°-, Y+41°-, Y+50°- Y+64°-, Y+128°-, Y+163°-, Z-cut.

[0008] According to one embodiment, the first and second regions are in the same level.

[0009] According to one embodiment, the first and second regions are adjacent.

[0010] According to one embodiment, the device comprises at least a third filter of the same type as the first and second filters in a third piezoelectric material, the third material being different from the first and second materials.

[0011] According to one embodiment, the first and second filters are surface acoustic wave filters and each comprise on an upper face of the first or second region, interdigitated comb-shaped electrodes.

[0012] According to one embodiment, the first and second filters are bulk acoustic wave filters on a Bragg reflector, and comprise a stack of a Bragg mirror and a first layer comprising a first electrode for each first and second filter, the first layer being located between the first and second regions and the substrate.

[0013] According to one embodiment, the first and second filters are thin-film resonator bulk acoustic wave filters, and comprise a first layer comprising a first electrode and a first cavity for each first and second filter, the first layer being located between the first and second regions and the substrate, the first cavity extending under the first electrode and being opened by a second cavity passing through the first or second region.

[0014] Another embodiment provides a method of manufacturing a device comprising first and second filters, the method comprising forming a first region of the first filter from a first piezoelectric material, and forming a second region of the second filter from a second piezoelectric material, the first and second materials being different and the first and second regions being on a same substrate.

[0015] According to one embodiment, the method comprises forming on the substrate a first layer of the first material, a step of etching the first layer so as to form the first region, forming a second layer of the second material filling at least the location of the second region and etching the second layer so as to form the second region.

[0016] According to one embodiment, the method comprises forming the first region on the substrate, forming the second region on an intermediate substrate, forming a third attachment layer at least at the location of the second region on the substrate, attaching the second region to the substrate, and removing the intermediate substrate.

[0017] According to one embodiment, the method comprises forming first electrodes on the first and second regions, forming a fourth insulating layer on the first electrodes and on the first and second regions, forming on another substrate, a Bragg mirror, fixing the fourth insulating layer on the mirror, removing the first substrate, forming second electrodes on the first and second regions and forming a via passing through each first and second region so as to reach a first electrode.

[0018] According to one embodiment, the method comprises: - between the formation of the first electrodes and the formation of the fourth insulating layer, the formation of elements made of a sacrificial material, each element partially covering the face of a first electrode furthest from the substrate and a side wall of the first electrode; and - after fixing the fourth layer, forming a cavity reaching each element and removing the sacrificial material. Brief description of the drawings

[0019] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0020] [Fig.l] represents an embodiment of a device comprising filters;

[0021] [Fig.2A] represents a step of a manufacturing process of the device of the [Fig.l];

[0022] [Fig.2B] represents another step of a method of manufacturing the device of [Fig.l];

[0023] [Fig.2C] represents another step of a method of manufacturing the device of [Fig.l];

[0024] [Fig.2D] represents another step of a method of manufacturing the device of [Fig.l];

[0025] [Fig.3A] represents a step of another method of manufacturing the device of [Fig.l];

[0026] [Fig.3B] represents another step of another method of manufacturing the device of [Fig.l];

[0027] [Fig.3C] represents another step of another method of manufacturing the device of [Fig.l];

[0028] [Fig.3D] represents another step of another method of manufacturing the device of [Fig.l];

[0029] [Fig.4] represents another embodiment of a device comprising filters;

[0030] [Fig.5] represents another embodiment of a device comprising filters;

[0031] [Fig.6A] represents a step of a method of manufacturing the device of the [Fig.5] ;

[0032] [Fig.6B] represents another step of a method of manufacturing the device of [Fig.5];

[0033] [Fig.6C] represents another step of a method of manufacturing the device of [Fig.5];

[0034] [Fig.7] shows another embodiment of a device comprising filters;

[0035] [Fig.8A] represents a step of a method of manufacturing the device of the [Fig.7] ;

[0036] [Fig.8B] represents another step of a method of manufacturing the device of [Fig.7]; and

[0037] [Fig.8C] represents another step of a method of manufacturing the device of [Fig.7], Description of the embodiments

[0038] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0039] For the sake of clarity, only the steps and elements useful for understanding the embodiments described have been represented and are detailed.

[0040] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of one or more other elements.

[0041] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made unless otherwise specified to the orientation of the figures.

[0042] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0043] [Fig.l] represents an embodiment of a device 10 comprising filters 12 and 14. In the example of [Fig.l], the device comprises a single filter 12 and a single filter 14. More generally, the device 10 may comprise a plurality of filters 12 and a plurality of filters 14.

[0044] The filters 12, 14 are preferably radio frequency filters of the same type, i.e. surface acoustic wave (SAW) filters.

[0045] The device 10 comprises a substrate 16. The substrate 16 is for example a semiconductor substrate. The substrate 16 is for example made of silicon, silicon carbide (SiC), sapphire (A13O2), or gallium nitride (GaN).

[0046] The filters 12, 14 are located on the same substrate 16. Each filter 12, 14 rests on the substrate 16. More precisely, each filter 12, 14 rests on an upper face of the substrate 16. Each filter 12, 14 is fixed to the substrate 16, for example by a layer of fixing 18. Thus, the device 10 comprises a fixing layer 18, for example common to the filters 12, 14, fixing the filters 12, 14 to the substrate 16. More precisely, the layer 18 rests on the upper face of the substrate 16 and the filters 12, 14 rest on an upper face of the layer 18. The fixing layer 18 has for example a constant thickness, for example at least opposite the filters 12, 14

[0047] Each filter 12, 14 comprises a region 20, 22 made of a piezoelectric material. More specifically, the filters 12 each comprise a region 20 and the filters 14 each comprise a region 22. The regions 20, 22 rest on the upper face of the layer 18. For example, the regions 20, 22 are in contact with the layer 18.

[0048] The regions 20 are all made of a first piezoelectric material. The regions 22 are all made of a second piezoelectric material. The first and second materials are different. The first and second materials are, for example, monocrystalline piezoelectric materials. The piezoelectric materials are defined by their nature and their orientation. The first and second materials have a different nature and / or orientation. The natures of the first and second materials, i.e. the atomic composition of the material, are, for example, among: LiNbO3, LiTaO3, Lii xNbxO3, AIN, Ali_xScxN, KTai xNbxO3. The orientations of the first and second materials are for example among: X-, Y-, Y+30°-, Y+36°-, Y+38°-, Y+41°-, Y+50°- Y+64°-, Y+128°-, Y+163°-, Z-cut, the nomenclature of the orientations being for example described in the document “IEEE Standard on Piezoelectricity,” of ANSI / IEEE Std 176-1987, 1988, doi: 10.1109 / IEEESTD. 1988.79638.

[0049] The regions 20 and 22 have, for example, identical dimensions. The regions 20 and 22 have, for example, the same height. The regions 20 and 22 are, for example, in the same layer, or in the same level, of the device. The upper faces of the regions 20, 22 are, for example, coplanar. The lower faces of the regions 20, 22 are, for example, coplanar. The regions 20, 22 of at least some filters, for example of all the filters 12, 14, are in lateral contact with the neighboring filters. Thus, the filter 12 and the filter 14 of [Fig. 1] are neighbors and the regions 20 and 22 of [Fig. 1] are in lateral contact. Preferably, the layer comprising the regions 20 and 22 only comprises regions 20 and 22.

[0050] Each filter 12, 14 further comprises electrodes 26, 28. In other words, each filter 12 comprises electrodes 26 and each filter 14 comprises electrodes 28. The electrodes 26, 28 are located on the upper face of the region 20, 22 of the filter, preferably in contact with the upper face of the region 20, 22.

[0051] Each filter 12 comprises for example two electrodes 26, each electrode 26 having a comb shape. By comb shape is meant a shape comprising a plurality of parallel auxiliary strips each comprising one end connected to a main strip. The electrodes 26 of a filter 12 are interdigitated. In other words, the electrodes 26 are arranged in such a way that each auxiliary strip of one of the electrodes 26 is separated from the neighboring auxiliary strip of the same electrode 26 by an auxiliary strip of the other electrode 26. Similarly, each filter 14 comprises for example two electrodes 28, each electrode 28 having a comb shape. The electrodes 28 of a filter 14 are interdigitated.

[0052] The difference in material between regions 20 and 22 causes a difference in acoustic background speed in regions 20 and 22 and therefore a difference in frequency between filters 12 and 14. Filters 12 and 14 thus filter different frequencies, or ranges of frequencies.

[0053] Figures 2A to 2D represent steps, preferably successive, of a method of manufacturing the device of [Fig.l].

[0054] [Fig.2A] represents a step of a method of manufacturing the device of [Fig.l].

[0055] During this step, a layer 30 made of the material of the regions 20 is fixed on the substrate 16. More precisely, this step comprises the formation of the substrate 16, the formation of the fixing layer 18 on an upper face of the substrate 16 and the fixing of the layer 30 on an upper face of the fixing layer 18.

[0056] For example, the step of [Fig.2A] may correspond to a known surface acoustic wave filter forming step. For example, the step of [Fig.2A] may correspond to a step of a method described in WO 2019002080.

[0057] The layer 30 has for example a constant thickness. The thickness of the layer 30 preferably has a height at least equal, preferably substantially equal, to the height of the region 20.

[0058] [Fig.2B] represents another step of a method of manufacturing the device of [Fig.l].

[0059] During this step, layer 30 is etched and / or thinned so as to obtain region 20. Preferably, layer 18 is not etched. In other words, the step of [Fig.2B] comprises the etching of layer 30, around the location of region 20, so as to reach the upper face of layer 18. In particular, the portions of layer 30 located in the location of region 22 are etched during the step of [Fig.2B].

[0060] [Fig.2C] represents another step of a method of manufacturing the device of [Fig.l].

[0061] During this step, a layer 32 made of the material of the region 22 is formed on the structure resulting from the step of FIG. B. The layer 32 is for example formed in a conformal manner.

[0062] The thickness of the layer 32 is at least equal, for example substantially equal, to the thickness of the region 22. Thus, the location of the region 22 is entirely filled by layer 32. Layer 32 further covers the upper face of region 20.

[0063] [Fig.2D] represents another step of a method of manufacturing the device of [Fig.l].

[0064] During this step, region 22 is formed. Thus, during the step of [Fig.2D], the portions of layer 32 located outside the location of region 22 are removed. For example, said portions are etched. Alternatively, said portions are removed by a chemical-mechanical polishing (CMP) process. For example, in the case where the layer comprising regions 20 and 22 only comprises regions 20 and 22, the step of [Fig.2D] comprises a chemical-mechanical polishing process. Thus, all the portions located outside the location of region 22 are above the level of the upper face of regions 20 and 22 and are removed by the CMP process.

[0065] The step of [Fig.2D] is for example followed by a step not shown of forming the electrodes 26 and 28. For example, the step of forming the electrodes 26, 28 comprises the formation of a conductive layer, for example metallic, on the upper faces of the regions 20 and 22. Said conductive layer is then etched so as to form the electrodes 26, 28.

[0066] Figures 3A to 3D represent steps, preferably successive, of another method of manufacturing the device of [Fig.l].

[0067] [Fig.3A] represents a step of another method of manufacturing the device of [Fig.l].

[0068] During this step, a structure 33 is formed. The structure 33 comprises an intermediate substrate 34, a fixing layer 36 and a region 22' identical to the region 22 described previously. The region 22' is formed so as to be fixed on the intermediate substrate 34, for example by the fixing layer 36. For example, the step of [Fig. 3A] corresponds to steps identical to the steps of FIGS. 2A and 2B, in which the layer 36 replaces the layer 18, in which the region 22' replaces the region 20 and in which the intermediate substrate 34 replaces the substrate 16.

[0069] [Fig.3B] represents another step of another method of manufacturing the device of [Fig.l].

[0070] During this step, a structure 37 is formed. The structure 37 comprises a region 20', a substrate 16' and a layer 18', respectively identical to the region 20, the substrate 16 and the layer 18 described previously. The region 20' is formed on the substrate 16', for example fixed by the layer 18'. Thus, the step of [Fig.3B] comprises for example steps identical to the steps of FIGS. 2A and 2B.

[0071] The step of [Fig.3B] comprises the formation of a fixing layer 38. The layer fixing layer 38 is for example formed conformally over the entire structure. The layer 38 covers for example at least the portion of the upper face of the layer 18 located at the location of the region 22'. In the example of [Fig.3B], the layer 38 covers the upper face of the region 20', the side walls of the region 20' and the location of the region 22'.

[0072] Regions 20' and 22' have for example the same height.

[0073] The steps of Figures 3A and 3B are performed independently. Thus, the step of [Fig.3B] can be performed before or during the step of [Fig.3A].

[0074] [Fig.3C] represents another step of another method of manufacturing the device of [Fig. 1].

[0075] During this step, structures 33 and 37 are assembled in such a way that region 22' is in its location. In other words, structures 33 and 37 are arranged and aligned in such a way that regions 20' and 22' are between substrates 16 and 34 and region 22' is attached to layer 18 in the location of region 22'.

[0076] [Fig.3D] represents another step of another method of manufacturing the device of [Fig. 1].

[0077] During this step, the substrate 34 and the layer 36 are removed. For example, the attachment layer 36 is configured to be able to be detached from the region 22', for example by a heat treatment step.

[0078] The step of [Fig.3D] then comprises, for example, the removal of the portions of the layer 38 located on the upper face of the region 20'.

[0079] The method then comprises, for example, a step of flattening the upper face of the structure, for example a step of chemical-mechanical polishing. The flattening step makes it possible, for example, to remove the portion of the region 22' located at a level higher than the level of the upper face of the region 20'.

[0080] Alternatively, region 22' may be formed such that the height of region 20' is equal to the sum of the height of layer 38 and region 22'.

[0081] [Fig.4] shows another embodiment of a device 40 comprising filters 42, 44, 46, 48. The filters 42, 44, 46, 48 are preferably filters of the same type, i.e. surface acoustic wave (SAW) filters. The filters 42, 44, 46, 48 are, for example, radio frequency filters.

[0082] The device 40 comprises elements of the device 10 of [Fig.l]. In particular, the device 40 comprises the substrate 16 and the attachment layer 18. The device 40 differs from the device 10 of [Fig.l] in that the device 40 comprises at least three types of filters. In the example of [Fig.4], the device 40 comprises four types of filters. The device 40 comprises at least one filter of each type. Only one filter of each type is shown in [Fig.4]. Thus, the filters 42, 44, 46, 48 are filters of different types.

[0083] As in the embodiment of [Fig.l], each filter comprises a region of piezoelectric material resting on layer 18 and electrodes resting on said region and forming two interdigital combs. In other words, filter 42 comprises a region 50 of piezoelectric material fixed to substrate 16 by fixing layer 18 and electrodes 52 forming interdigital combs. Filter 44 comprises a region 54 of piezoelectric material fixed to substrate 16 by fixing layer 18 and electrodes 56 forming interdigital combs. Filter 46 comprises a region 58 of piezoelectric material fixed to substrate 16 by fixing layer 18 and electrodes 60 forming interdigital combs. The filter 48 comprises a region 62 of a piezoelectric material fixed to the substrate 16 by the fixing layer 18 and electrodes 64 forming interdigital combs.

[0084] The piezoelectric materials of the regions 50, 54, 58, 62 are materials that are different from each other. Said materials are, for example, single-crystal piezoelectric materials. Said materials have a different nature and / or orientation. The natures of the materials, i.e. the atomic composition of the material, are, for example, among: LiNbO3, LiTaO3, Lii xNbxO3, AIN, Ali_xScxN, KTa i_xNbxO3. The orientations of the materials are, for example, among: X-, Y-, Y+30°-, Y+36°-, Y+38°-, Y+41°-, Y+50°- Y+64°-, Y+128°-, Y+163°-, Z-cut.

[0085] The regions 50, 54, 58, 62 have, for example, identical dimensions. The regions 50, 54, 58, 62 have, for example, the same height. The regions 50, 54, 58, 62 are, for example, in the same layer, or the same level, of the device. The upper faces of the regions 50, 54, 58, 62 are, for example, coplanar. The lower faces of the regions 50, 54, 58, 62 are, for example, coplanar. The regions 50, 54, 58, 62 of at least some filters, for example of all the filters 42, 44, 46, 48, are in lateral contact with the neighboring filters. Thus, the filters 42, 44, 46, 48 are neighbors and the regions 50, 54, 58, 62 are in lateral contact. Preferably, the layer comprising regions 50, 54, 58, 62 only comprises regions 50, 54, 58, 62.

[0086] The device 40 is for example formed by a method similar to the method of FIGS. 2A to 2D, comprising the formation of the region 50 by the step of [Fig. 2A] and the successive formation of the regions 54, 58, 62 by repeating the steps of FIGS. 2B to 2D. In other words, the formation of the device 40 comprises for example: - the step of [Fig.2A] in which the layer 30 is made of the material of the region 50; - the step of [Fig.2B] in which layer 30 is etched at the location of region 54; - the step of [Fig.2C] in which a layer of the material of region 54 is formed; - the step of [Fig.2D] in which the portion of the layer in the material of the region 54 is removed outside the region 54 location; - the step of [Fig.2B] in which layer 30 is etched at the location of region 58; - the step of [Fig.2C] in which a layer of the material of region 58 is formed; - the step of [Fig.2D] in which the portion of the layer of the material of the region 58 is removed outside the location of the region 58; - the step of [Fig.2B] in which layer 30 is etched at the location of region 62; - the step of [Fig.2C] in which a layer of the material of region 62 is formed; - the step of [Fig.2D] in which the portion of the layer of material of the region 62 is removed outside the location of the region 62; and - the formation of the electrodes 52, 56, 60, 64.

[0087] According to a variant, the method of [Fig.4] can be obtained by a method similar to the method of Figures 3A to 3D. The method then comprises: - the step of [Fig.3A] in which each region 54, 58, 62 is formed on an intermediate substrate; - the step of [Fig.3B], in which region 50 is formed on layer 18; - the successive placement of the regions 54, 58, 62 on the substrate 18 as described in relation to figures 3C and 3D; and - the formation of electrodes 52, 56, 60, 64.

[0088] [Fig. 5] shows another embodiment of a device 70 comprising filters 72 and 74. In the example of [Fig. 5], the device comprises a single filter 72 and a single filter 74. More generally, the device 70 may comprise a plurality of filters 72 and a plurality of filters 74.

[0089] The filters 72, 74 are preferably filters of the same type, i.e. bulk acoustic wave (BAW) filters. More precisely, the filters 72, 74 are preferably bulk acoustic wave filters on a Bragg reflector (or mirror) (BAW-SMR - Bulk Acoustic Waves-Solidly Mounted Resonator). The filters 72, 74 are, for example, radio frequency filters.

[0090] The device 70 comprises a substrate 76. The substrate 76 is for example an insulating substrate. The substrate 76 is for example made of high resistivity silicon.

[0091] The device 70 comprises a Bragg mirror 78. In other words, the device comprises a stack 78 of several layers alternating two different refractive indices. The materials of the Bragg mirror are for example chosen according to the application of the device. The mirror 78 rests on an upper face of the substrate 76. The mirror 78 covers at least the portion of the substrate 76 located opposite the filters 72, 74. The mirror 78 covers, for example, the entire upper face of the substrate 76.

[0092] The device 70 further comprises an insulating layer 80. The layer 80 is for example made of a dielectric material, for example silicon oxide. The layer 80 covers at least the portion of the mirror 78 located opposite the filters 72, 74. The layer 80 covers for example the entire upper face of the mirror 78.

[0093] The device 70 comprises electrodes 82, 84. More specifically, the device 70 comprises one electrode 82, 84 per filter. Each electrode 82 corresponds to a filter 72 and each electrode 84 corresponds to a filter 74. The electrodes correspond to conductive strips, for example metal strips. The electrodes 82, 84 are located in the layer 80. More specifically, the electrodes 82, 84 are flush with the upper face of the layer 80. The side and lower walls of the electrodes 82, 84 are covered by the layer 80. Each electrode 82 is located opposite the location of the corresponding filter 72. Each electrode 84 is located opposite the location of the corresponding filter 74.

[0094] Each filter 72, 74 comprises a region 86, 88 made of a piezoelectric material. More specifically, the filters 72 each comprise a region 86 and the filters 74 each comprise a region 88. The regions 86, 88 rest on the upper face of the layer 80 and on the upper face of the electrodes 82, 84. For example, the regions 86 and 88 are in contact with the layer 80 and with the electrodes. More specifically, the lower face of the region 86 is in contact with the layer 80 and the electrode 82. The lower face of the region 88 is in contact with the layer 80 and the electrode 84. The electrode 84 is not in contact with the region 86. The electrode 82 is not in contact with the region 88.

[0095] The regions 86 are all made of a first piezoelectric material. The regions 88 are all made of a second piezoelectric material. The first and second materials are different. The first and second materials are, for example, single-crystal piezoelectric materials. The piezoelectric materials are defined by their nature and their orientation. The first and second materials have a different nature and / or orientation. The natures of the first and second materials, i.e. the atomic composition of the material, are, for example, among: LiNbO3, LiTaO3, Lii xNbxO3, AIN, Ali.xScxN, KTai xNbxO3. The orientations of the first and second materials are for example among: X-, Y-, Y+30°-, Y+36°-, Y+38°-, Y+41°-, Y+50°- Y+64°-, Y+128°-, Y+163°-, Z-cut.

[0096] The regions 86, 88 have for example identical dimensions. The regions 86, 88 have for example the same height. The regions 86, 88 are for example in the same layer, or the same level, of the device. The upper faces of the regions 86, 88 are for example coplanar. The lower faces of the regions 86, 88 are for example coplanar. The regions 86, 88 of at least certain filters, for example of all filters 72, 74 are in lateral contact with neighboring filters. Thus, filter 72 and filter 74 of [Fig.5] are neighbors and regions 86, 88 of [Fig.5] are in lateral contact. Preferably, the layer comprising regions 86, 88 only comprises regions 86, 88.

[0097] Each filter 72, 74 further comprises an electrode 90, 92. In other words, each filter 72 comprises an electrode 90 and each filter 74 comprises an electrode 92. The electrodes 90, 92 are located on the upper face of the region 86, 88 of the filter, preferably in contact with the upper face of the region 86, 88.

[0098] Each filter 72, 74 further comprises an opening passing through the region 86, 88 so as to reach the electrode 82, 84 located in contact with the lower face of the region 86, 88. Each opening is for example filled by an insulated conductive via 94 allowing the connection of the electrodes 82, 84. Each via 94 comprises for example a lateral insulating sheath and a conductive core.

[0099] Figures 6A to 6C represent steps, preferably successive, of another method of manufacturing the device of [Fig.5].

[0100] [Fig.6A] represents a step of a manufacturing process of the device of the [Fig.5],

[0101] The step of [Fig.6A] comprises forming the structure of [Fig.1], wherein region 88 corresponds to region 20 and region 86 corresponds to region 22. Thus, the step of [Fig.6A] comprises, for example, the method of Figures 2A to 2D or the method of Figures 3A to 3D.

[0102] The step of [Fig.6A] further comprises the formation of the electrodes 82 and 84. The formation of the electrodes 82 and 84 comprises for example the formation of a layer of the material of the electrodes 82, 84, for example metal, and the etching of said layer so as to remove the portions of the layer outside the locations of the electrodes 82, 84.

[0103] The step of [Fig.6A] further comprises the formation of the layer 80. In other words, the layer 80 is deposited on the structure resulting from the formation of the electrodes 82, 84. The layer 80 is formed so as to cover the electrodes 82, 84 and the regions 86, 88. The formation of the layer 80 is for example such that the face of the layer 80 furthest from the regions 86, 88 is flat.

[0104] [Fig.6B] represents another step of a method of manufacturing the device of [Fig.5],

[0105] During this step, the Bragg mirror 78 is formed on the substrate 76.

[0106] The step of [Fig.6B] further comprises fixing the structure resulting from the step of [Fig.6A] on the Bragg mirror. More precisely, the structures are fixed to each other in such a way that the face of the layer 80 furthest from the regions 86, 88 is fixed to the face of the Bragg mirror 78 furthest from the substrate 76.

[0107] [Fig.6C] represents another step of a method of manufacturing the device of [Fig.5].

[0108] During this step, the layer 18 and the substrate 16 are removed. The removal of the layer 18 and the substrate 16 is for example carried out by a method such as the method described in document EP 4006998.

[0109] The step of [Fig.6C] further comprises the formation of the electrodes 90 on the regions 86 and 88, for example by the formation and etching of a conductive layer, for example metallic.

[0110] The step of [Fig.6C] further comprises forming an opening in each region 86, 88 so as to reach the electrode 82, 84. The openings are for example then filled with insulated conductive vias 94.

[0111] [Fig.7] represents another embodiment of a device 100 comprising filters 102, 104. In the example of [Fig.7], the device comprises a single filter 102 and a single filter 104. More generally, the device 100 may comprise a plurality of filters 102 and a plurality of filters 104.

[0112] The filters 102, 104 are preferably filters of the same type, i.e. bulk acoustic wave (BAW) filters. More specifically, the filters 102, 104 are preferably bulk acoustic wave filters with self-suspended thin-film resonator (BAW-FBAR - Bulk Acoustic Waves- Film Bulk Acoustic Resonator). The filters 102, 104 are, for example, radio frequency filters.

[0113] The device 100 comprises elements identical to elements of the device 70. Thus, the device 100 comprises the substrate 76, the layer 80, the electrodes 82, 84, the regions 86, 88, the vias 94 and the electrodes 90, 92. The device 100 differs from the device 70 in that the device 100 does not comprise the Bragg mirror 78 and comprises cavities 106.

[0114] Each filter 102, 104 comprises a cavity 106. Each cavity 106 is located under a portion of each electrode 82, 84. Thus, a portion of the lower face of each electrode 82, 84, for example at least half of the lower face of each electrode 82, 84, forms a portion of the wall of the cavity 106 of the corresponding filter. Each cavity 106 extends, for example, along a side wall of each electrode 82, 84 so as to reach the level of the upper face of the layer 80.

[0115] Each filter further comprises a cavity 108 passing through the region 86, 88 so as to reach the cavity 106.

[0116] Figures 8A to 8C represent steps, preferably successive, of another method of manufacturing the device of [Fig.7].

[0117] Alternatively, the filters 102, 104 of the device 100 may be Lamb wave filters. Each filter then comprises electrodes, not shown, located on the upper face of region 86, 88 and forming crenellations.

[0118] [Fig.8A] represents a step of a method of manufacturing the device of the [Fig.7],

[0119] The step of [Fig.8A] comprises the steps of [Fig.6A]. Thus, the step of [Fig.8A] comprises the formation of the substrate 16, the layer 18, the regions 86, 88, the electrodes 82, 84 and the layer 80, as described in connection with [Fig.6A]. Step 8A differs from step 6A in that step 8A comprises the formation of an element 110 made of a sacrificial material at the location of the cavity 106. The element 110 is for example made of polycrystalline silicon, amorphous silicon, resin or another material that can be etched preferentially compared to the materials of the layers 80, 88 and the material of the electrode 84, i.e. that can be etched at least twice as fast, for example at least ten times as fast, as the materials of the layers 80, 88 and the material of the electrode 84.

[0120] Each element 110 partially covers, for example covers at least half, of the face of an electrode 82, 84 furthest from the substrate 16. Said element 110 further covers a side wall of the electrode 82, 84 and a portion of the face of the region 86, 88 furthest from the substrate 16.

[0121] [Fig.8B] represents another step of a method of manufacturing the device of [Fig.7],

[0122] The step of [Fig.8B] comprises, like the step of [Fig.6B], the fixing of the structure resulting from the step of [Fig.8A] on the substrate 76. More precisely, the structures are fixed to each other in such a way that the face of the layer 80 furthest from the regions 86, 88 is fixed to a face of the substrate 76.

[0123] The step of [Fig.8B] further comprises removing the layer 18 and the substrate 16, for example as described in relation to [Fig.6C].

[0124] [Fig.8C] represents another step of a method of manufacturing the device of [Fig.7],

[0125] The step of [Fig.8C] comprises, like the step of [Fig.6C], the formation of the electrodes 90 on the regions 86 and 88, for example by the formation and etching of a conductive layer, for example metallic.

[0126] The step of [Fig.8C] further comprises forming an opening in each region 86, 88 so as to reach the electrode 82, 84. The openings are for example then filled with insulated conductive vias 94.

[0127] The step of [Fig.8C] further comprises the formation of the openings 108 each passing through a region 86, 88 so as to reach an element 110. The device comprises as many openings 108 as there are elements 106. The device comprises, for example, as many openings 108 as there are filters 102 and 104. The cavities 108 are, for example, formed at the same time as the cavities of the vias 94.

[0128] The step of [Fig.8C] further comprises the removal of the element 110 made of sacrificial material. The removal of the element 110 is for example carried out before the formation of the vias 94.

[0129] According to another embodiment, the filters may be Lamb wave filters and the formation of the electrodes 90 may be replaced by the formation of electrodes having an interdigital comb shape.

[0130] An advantage of the described embodiments is that it is possible to form, on the same substrate, radio frequency filters adapted to different frequencies and different bandwidths.

[0131] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art.

[0132] Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

Claims

Claims

1. A device comprising first (12, 72, 102) and second (14, 74, 104) filters, the first filter (12, 72, 102) comprising a first region (20, 86) of a first piezoelectric material, the second filter (14, 74, 104) comprising a second region (22, 88) of a second piezoelectric material, the first and second materials being different and the first (20, 86) and second (22, 88) regions being on the same substrate.

2. Device according to claim 1, in which the first (12, 72, 102) and second (14, 74, 104) filters are of the same type.

3. A device according to claim 1 or 2, wherein the first (12, 72, 102) and second (14, 74, 104) filters are surface acoustic wave filters, bulk acoustic wave filters, or Lamb wave filters.

4. Device according to any one of claims 1 to 3, wherein the first and second materials are among LiNbO3, LiTaO3, LibxNbx O3, AIN, Ali_xScxN, KTai xNbxO3 and have an orientation among: X-, Y-, Y+30°-, Y+36°-, Y+38°-, Y+41°-, Y+50°- Y+64°-, Y+128°-, Y+163°-, Z-cut.

5. A device according to any one of claims 1 to 4, wherein the first (20, 86) and second (22, 88) regions are in the same level.

6. A device according to any one of claims 1 to 5, wherein the first (20, 86) and second (22, 88) regions are adjacent.

7. A device according to any one of claims 1 to 6, wherein the device comprises at least one third filter (42, 44, 46, 48) of the same type as the first (12, 72, 102) and second (14, 74, 104) filters made of a third piezoelectric material, the third material being different from the first and second materials.

8. Device according to any one of claims 1 to 7, in which the first (12) and second (14) filters are surface acoustic wave filters and each comprise on an upper face of the first or second region, electrodes (26, 28) in the form of interdigitated combs.

9. A device according to any one of claims 1 to 7, wherein the first (72) and second (74) filters are bulk acoustic wave filters on a Bragg reflector, and comprise an em- stacking a Bragg mirror (78) and a first layer (80) comprising a first electrode (82, 84) for each first and second filter, the first layer (80) being located between the first and second regions and the substrate (16).

10. A device according to any one of claims 1 to 7, wherein the first (102) and second (104) filters are thin-film resonator bulk acoustic wave filters, and comprise a first layer (80) comprising a first electrode (82, 84) and a first cavity (106) for each first and second filter, the first layer being located between the first and second regions and the substrate, the first cavity extending under the first electrode and being opened by a second cavity passing through the first or second region.

11. A method of manufacturing a device comprising first (12, 72, 102) and second (14, 74, 104) filters, the method comprising forming a first region of the first filter (12, 72, 102) from a first piezoelectric material, and forming a second region of the second filter from a second piezoelectric material, the first and second materials being different and the first and second regions being on a same substrate.

12. The method of claim 11, wherein the method comprises forming on the substrate (16) a first layer (30) of the first material, a step of etching the first layer (30) so as to form the first region (20), forming a second layer (32) of the second material filling at least the location of the second region (22) and etching the second layer (32) so as to form the second region (22).

13. The method of claim 11, comprising forming on the substrate (16) the first region (20), forming the second region (22) on an intermediate substrate (34), forming a third attachment layer (38) at least at the location of the second region (22) on the substrate (16), attaching the second region (22) to the substrate (16), and removing the intermediate substrate (34).

14. The method of claim 12 or 13, wherein the method comprises forming first electrodes (82, 84) on the first and second regions, forming a fourth insulating layer (80) on the first electrodes and on the first and second regions, forming on another substrate, a Bragg mirror (78), fixing the fourth insulating layer on the mirror, removing the first substrate, forming second electrodes on the first and second regions and forming a via (94) passing through each first and second region so as to reach a first electrode.

15. A method according to claim 14, wherein the method comprises: - between the formation of the first electrodes and the formation of the fourth insulating layer, the formation of elements made of a sacrificial material, each element partially covering the face of a first electrode furthest from the substrate and a side wall of the first electrode; and - after fixing the fourth layer, the formation of a cavity reaching each element and the removal of the sacrificial material.

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