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    • 专利摘要:
    The invention relates to a hybrid structure (100) for a surface acoustic wave device comprising a useful layer (10) of piezoelectric material having a first free face (1) and a second face (2) disposed on a support substrate (20). whose coefficient of thermal expansion is less than that of the useful layer (10), the hybrid structure (100) being remarkable in that the useful layer (10) comprises a zone (30) of nanocavities (31).
    公开号:FR3052298A1
    申请号:FR1655030
    申请日:2016-06-02
    公开日:2017-12-08
    发明作者:Marcel Broekaart
    申请人:Soitec SA；
    IPC主号:
    专利说明:

    HYBRID STRUCTURE FOR ACOUSTIC WAVE DEVICE
    AREA
    FIELD OF 1 / INVENTION
    The present invention relates to the field of surface acoustic wave devices. It relates in particular to a hybrid structure adapted for the manufacture of surface acoustic wave devices.
    BACKGROUND OF THE INVENTION
    Acoustic resonator structures such as Surface Acoustic Wave (SAW) devices use one or more interdigital transducers produced on a piezoelectric substrate to convert electrical signals into acoustic waves. and vice versa. Such SAW devices or resonators are often used in filtering applications. Radio Frequency (RF) SAW technology provides excellent performance such as high isolation and low insertion loss. For this reason, it is used for RF duplexers in wireless communication applications. However, in order to be more competitive with RF duplexers based on Bulk Acoustic Wave (BAW) technology, the performance of RF SAW devices needs to be improved, and in particular Frequency response is stable with respect to temperature.
    The dependence of the operating frequency of the SAW devices on the temperature, or the thermal frequency coefficient ("TCF" for "Temperature Coefficient of Frequency"), depends on the one hand on the variations in the spacing between the interdigitated electrodes of the transducers, which are generally due to the relatively high thermal expansion coefficients ("CTE" for "Coefficient of Thermal Expansion") of the piezoelectric substrates used; on the other hand, the TCF depends on the thermal speed coefficient because the expansion or contraction of the piezoelectric substrate is accompanied by an increase or decrease in the speed of the surface acoustic wave. To minimize the thermal frequency coefficient (TCF), an objective is therefore to minimize the expansion / contraction of the piezoelectric substrate, especially in the surface area in which the acoustic waves will propagate. The article by K.Hashimoto, M.Radota et al, "Recent Development of Temperature Compensated SAW Devices," IEEE Ultrasound. Symp. 2011, pages 79 to 86, 2011, provides an overview of commonly used approaches to overcoming the frequency dependence problem of SAW frequency response.
    One approach is to use a hybrid substrate, for example composed of a layer of piezoelectric material disposed on a silicon substrate. The low CTE of the silicon makes it possible to limit the expansion / contraction of the piezoelectric layer in temperature. In the case of a piezoelectric layer of lithium tantalate (LiTaO 3), the above-mentioned article indicates that a ratio of 10 between the thickness of LiTaO 3 and the thickness of the silicon substrate makes it possible to improve suitably the coefficient of thermal frequency (TCF). One of the drawbacks of this approach comes from the presence of spurious acoustic waves (called "spurious acoustic modes" in the article "Characterization of bonded wafer for RF filters with reduced TCF", BPAbbott et al., Proc 2005 IEEE International Ultrasonics Symposium, Sept 19-21, 2005, pp.926-929) which negatively impact the frequency characteristics of the resonator developed on the hybrid substrate. These parasitic resonances are notably related to parasitic reflections of the main acoustic wave (propagating mainly in a superficial zone of the LiTaO3 layer) on the underlying interfaces, including in particular the interface between LiTaO3 and silicon. One solution for reducing these parasitic resonances is to increase the thickness of the LiTaO 3 layer; this assumes that the thickness of the Si substrate is also increased to maintain improvements in the TCF, the total thickness of the hybrid substrate is no longer compatible with the thickness reduction requirements of the final components, in particular to address the market. cell phones. Another solution, proposed by K.Hashimoto et al. is to roughen the lower surface of the LiTaO 3 layer (at the bonding interface with the substrate) so as to limit the reflections of the acoustic wave thereon. Such roughening represents a difficulty to manage when a direct bonding process, requiring very smooth surfaces to assemble, is used for the realization of the hybrid substrate.
    OBJECT OF THE INVENTION
    An object of the present invention is to propose an alternative solution to the solutions of the state of the art. An object of the invention is in particular to provide a hybrid structure for reducing and / or eliminating said parasitic acoustic waves.
    BRIEF DESCRIPTION OF 1 / INVENTION
    The present invention relates to a hybrid structure for a surface acoustic wave device comprising a useful layer of piezoelectric material having a first free face and a second face disposed on a support substrate whose thermal expansion coefficient is less than that of the useful layer. The hybrid structure is remarkable in that the useful layer comprises a zone of nanocavities.
    The nanocavity zone is adapted to diffuse an acoustic wave propagating in the thickness of the useful layer to said zone; it reduces or even eliminates parasitic reflections of the acoustic wave, which usually occur at the interface (s) of the hybrid structure and negatively impact the frequency characteristics of the SAW device.
    In addition, the nanocavity zone is formed in the thickness of the useful layer and does not affect the roughness of the second face, which facilitates and makes reliable the assembly of the useful layer on the support substrate.
    According to advantageous features of the invention, taken alone or in combination: the nanocavity zone has a functional thickness of between 50 nm and 3 microns; The zone of nanocavities is closer to the second face than to the first face of the useful layer; The zone of nanocavities is at a distance of more than 50 nm from the second face of the useful layer; The nanocavities have, at least in part, a maximum dimension of between 1 nm and 500 nm; • nanocavities occupy between 10% and 20% of the volume in the nanocavity zone; The nanocavities have a substantially spherical or polyhedral shape; • all or part of the nanocavities contains a gaseous species; The zone of nanocavities extends in a plane parallel to the second face of the useful layer; The zone of nanocavities is continuous in a plane parallel to the second face of the useful layer; The zone of nanocavities is discontinuous in a plane parallel to the second face of the useful layer; The support substrate comprises a material chosen from silicon, glass, silica, sapphire, alumina, aluminum nitride, silicon carbide; The useful layer comprises a piezoelectric material chosen from lithium tantalate (LiTaO 3), lithium niobate (LiNbO 3), quartz, zinc oxide (ZnO); The hybrid structure comprises an intermediate layer located between the second face of the useful layer and the support substrate.
    The present invention further relates to a surface acoustic wave device comprising a hybrid structure as above. Advantageously, the frequency of the acoustic waves is between 700 MHz - 3 GHz.
    The present invention finally relates to a method of manufacturing a hybrid structure for a surface acoustic wave device comprising: a) a step of providing a useful layer of piezoelectric material having a first face and a second face; b) a step of providing a support substrate having a coefficient of thermal expansion less than that of the useful layer; c) a step of assemblaqe the second face of the useful layer on the support substrate;
    The method is remarkable in that it comprises a step of introducing gaseous species into the useful layer to form a zone of nanocavities.
    According to advantageous features of the invention, taken alone or in combination: the useful layer provided in step a) is included in a donor substrate made of piezoelectric material; The manufacturing method comprises, after the assembly step, a step d) of thinning the donor substrate to a thickness that is useful for forming the useful layer; The step of introducing gaseous species comprises at least one implantation of ions chosen from hydrogen, helium, argon and other noble gases; • The manufacturing process comprises a heat treatment step after the step of introducing gaseous species; The introduction of gaseous species into the useful layer is carried out at its second face, before the assembly step; The introduction of gaseous species into the useful layer is carried out at its first face, after the assembly step; The introduction of gaseous species into the useful layer is carried out locally by applying a mask.
    BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the invention will emerge from the detailed description which follows with reference to the appended figures in which: FIG. 1 shows a hybrid structure according to the invention; Figures 2a to 2e show a sectional view (2a) and top views (2b to 2e) of hybrid structures according to the invention; Figure 3 shows a hybrid structure according to the invention; FIG. 4 shows a surface acoustic wave device according to the invention; Figures 5a to 5e show a method of manufacturing a hybrid structure according to a first embodiment; Figures 6a and 6b show a method of manufacturing a hybrid structure according to a second embodiment; Figures 7a to 7c show a method of manufacturing a hybrid structure according to a third embodiment.
    DETAILED DESCRIPTION OF THE INVENTION
    In the descriptive part, the same references in the figures can be used for elements of the same nature.
    The figures are schematic representations which, for purposes of readability, are not to scale. In particular, the thicknesses of the layers along the z axis are not scaled with respect to the lateral dimensions along the x and y axes. Likewise, the size of the nanocavities is not to scale with respect to the thicknesses of layers or other lateral dimensions of elements of the invention. The invention relates to a hybrid structure 100 for a surface acoustic wave device comprising a useful layer 10 of piezoelectric material having a first free face 1 and a second face 2 disposed on a support substrate 20. The useful layer 10 typically has a useful thickness between 1 micron and 50 microns, depending on the type of SAW device to be developed on the hybrid structure 100. The useful layer 10 advantageously comprises a piezoelectric material chosen from lithium tantalate (LiTaO 3), lithium niobate (LiNbO 3), quartz, zinc oxide (ZnO).
    The support substrate 20 of the hybrid structure 100 has a coefficient of thermal expansion less than that of the useful layer 10, at least along a crystallographic axis in the case of anisotropic materials. It may comprise a material selected from silicon, glass, silica, sapphire, alumina, aluminum nitride, silicon carbide.
    Of course, this list of materials is not exhaustive, other substrates or useful piezoelectric layers could be chosen according to the type of applications and properties required.
    The hybrid structure 100 further comprises a zone 30 of nanocavities 31 in the useful layer 10, as illustrated in FIG.
    Preferably, the nanocavities 31 have a substantially spherical, polyhedral or ellipsoidal shape. This form is advantageous because it promotes a multidirectional reflection and therefore the diffusion of acoustic waves may propagate in the thickness of the useful layer 10, thus avoiding reflection on a flat surface such as the interface between the useful layer 10 and the substrate 20. The nanocavities 31 may be empty or contain a gaseous species or a mixture of gaseous species.
    The nanocavities 31 typically have a maximum dimension of between 1 nm and 500 nm; maximum dimension means, for example, the diameter of the nanocavity if it has a spherical shape or its largest diameter if it is slightly ellipsoidal. The density of the nanocavities 31 in the zone 30 is such that they occupy preferably 10% to 20% of the volume of said zone 30. The size and the density of the nanocavities 31 may have an influence on the diffusion efficiency of the acoustic waves. Thus, depending on the frequency of the acoustic wave (s) propagating in the device that will be developed on the hybrid structure 100, the size and density parameters of the nanocavities 31 can be adjusted.
    The area 30 of nanocavities 31 advantageously has a so-called functional thickness e of between 50 nm and 3 microns, along the axis z in FIG. 1. The functional thickness e is advantageously chosen to be equal to or substantially smaller than the wavelength λ. the acoustic signal used for the SAW device, for example between
    and
    On the other hand, the average maximum dimension of the nanocavities will preferably be chosen less than or equal to the wavelength λ of the acoustic wave; typically it can be between
    and λ. This configuration favors the interaction between the acoustic wave and the zone of nanocavities 31. In particular, the acoustic wave portion that is usually reflected at the interfaces of the hybrid structure will advantageously be diffused by zone 30: this will result in strongly limit or even eliminate the reflected component of the acoustic wave at the origin of parasitic effects.
    Preferably, the area 30 of nanocavities 31 is close to the second face 2 of the useful layer 10. In particular, it may be located at a distance d of the order of 50 nm from the second face 2. It may alternatively be located at a distance of between a few nm and about 30% of the useful thickness. By way of example, for a useful layer 10 with a useful thickness of 10 microns, the zone 30 may be situated at a distance of between 50 nm and 3 microns from the second face 2.
    Advantageously, the zone 30 of nanocavities extends in a plane parallel to the second face 2 of the useful layer 10. It can be continuous in the useful layer 10, that is to say present throughout the hybrid structure 100. This configuration leaves room for the positioning of the SAW device on the hybrid structure 100.
    Alternatively, the zone 30 of nanocavities 31 may be discontinuous and be present only locally, in certain regions of the useful layer 10, as illustrated in FIG. 2a. By way of example and without limitation, in plan view, the area 30 of nanocavities 31 may take the form of strip patterns (FIG. 2b), circular patterns (FIG. 2c), regions complementary to patterns circular (Figure 2d) or square patterns (Figure 2e). A dimension in the (x, y) plane of regions comprising the area of nanocavities is preferably between 1 and 10 microns.
    The discontinuity of the zone 30 of nanocavities 31 can bring advantages in the case of acoustic waves of long wavelengths (of the order of 5 microns and more): in fact, the presence of larger patterns and A longer period than the nanocavities 31 can promote the interaction of the acoustic wave with the discontinuous zone and thus improve the diffusion of the wave.
    According to another embodiment, the local area of nanocavities may be present only in the regions on which the electrodes of the SAW device will be developed, electrodes between which the acoustic waves will propagate.
    The hybrid structure 100 according to the invention may also comprise an intermediate layer 40, disposed between the second face 2 of the useful layer 10 and the support substrate 20 (FIG. 3). This intermediate layer 40 is, for example, made of a material chosen from silicon oxide, silicon nitride, amorphous or polycrystalline silicon, and the like. The intermediate layer 40 may have a function (electrical insulation, trapping charge carriers, etc ...) in the future SAW device, which will be developed on the hybrid structure 100. It can also be used to facilitate the assembly between the useful layer 10 and the support substrate 20, in particular to reinforce the bonding energy of the assembly interface.
    The hybrid structure 100 according to the invention is suitable for the manufacture of a surface acoustic wave device 200, a simplified representation of which is given in FIG. 4. Such a device 200 comprises in particular metal electrodes 50 arranged on the first face. 1 of the useful layer 10. One or more acoustic waves (s) will be propagated between the electrodes 50 during the operation of the device 200.
    The zone 30 of nanocavities 31 of the hybrid structure 100 is adapted to diffuse an acoustic wave propagating in the thickness of the useful layer 10 to said zone 30; it reduces or even eliminates the parasitic reflections of the acoustic wave, which usually occur at the interface (s) of the hybrid structure 100 and have a negative impact on the frequency characteristics of the SAW device 200.
    The hybrid structure 100 according to the invention is particularly suitable for the manufacture of SAW 200 devices using acoustic wave frequencies between 700 MHz and 3GHz.
    The present invention also relates to a method of manufacturing a hybrid structure 100 for a surface acoustic wave device 200 comprising a first step of providing a useful layer 10 of piezoelectric material having a first face 1 and a second face 2 The manufacturing method also comprises a step of providing a support substrate 20 having a coefficient of thermal expansion less than that of the useful layer 10. It also comprises a step of assembling the second face 2 of the useful layer 10 on the support substrate 20. As known per se, different assembly techniques can be implemented, including molecular bonding adhesion, adhesive bonding, or other type of bonding suitable for the manufacture of a hybrid structure. An intermediate layer 40 may be added prior to assembly, either on the second face 2 of the useful layer 10, or on the face to be assembled of the support substrate 20, or on both. This intermediate layer 40 is for example made of silicon oxide, silicon nitride or polycrystalline silicon and have a thickness of between a few nanometers and a few microns. The intermediate layer 40 may be prepared according to the various techniques known from the state of the art, such as thermal treatments of oxidation or nitriding, chemical deposits (PECVD, LPCVD ...), etc.
    The manufacturing method according to the invention further comprises a step of introducing gaseous species into the useful layer 10 to form a zone 30 of nanocavities 31. This step can be carried out before or after the step of assembling the useful layer 10 on the support substrate 20. Advantageously, the step of introducing gaseous species comprises at least one implantation of ions chosen from hydrogen, helium, argon, or other noble gases. It is of course possible to use other gases capable of forming nanocavities 31 in the useful layer 10.
    As is well known to those skilled in the art, the implantation energy is chosen as a function of the desired depth for the nanocavity zone 30. The dose of implanted ions is chosen from the range that makes it possible to form nanocavities 31 in the material of the useful layer 10, of size and density advantageously allowing the nanocavities 31 to occupy 10% to 20% of the volume in the zone 30. The dose of implanted ions is also chosen less than the dose likely to generate deformations or other damage at one or other of the faces 1,2 of the useful layer 10.
    Depending on the chosen functional thickness of the nanocavity zone 30, one or more ion implantation steps may be performed in the active layer (10), at different implantation energies, in the aim of broadening the implantation profile and thus said functional thickness or for the purpose of forming a specific profile different from the substantially Gaussian profile generated by a single implantation.
    According to one variant, the step of introducing gaseous species can be made locally in the useful layer 10. For this, it is usual to use a masking layer, deposited on the face of the useful layer 10 to be implanted, which protects regions in which it is not desired to form the zone 30 and which leaves exposed regions in which the zone 30 is to be formed. It is thus possible to obtain a hybrid structure 100 such as those illustrated in FIGS. 2a to 2e.
    The manufacturing method may advantageously comprise a heat treatment step subsequent to the introduction of gaseous species, making it possible to remove, at least partially, the gaseous species from the useful layer 10 and in particular to form and / or stabilize the nanocavities 31 in the material. This heat treatment may, for example, be carried out at a temperature of between 200 ° C. and 900 ° C., for a duration ranging from a few minutes to a few hours. The temperature of the heat treatment will preferably be chosen to be lower than the Curie temperature of the piezoelectric material of the useful layer 10.
    Particular embodiments of the manufacturing method will now be described with reference to Figures 5, 6 and 7.
    According to a first embodiment of the invention, the first step of the method consists in providing a donor substrate 11 made of piezoelectric material (FIG. 5a), including the useful layer 10. The donor substrate 11 comprises a first face 1 and a second face 2. For example, it may consist of a piezoelectric material selected from lithium tantalate (LiTaO 3), lithium niobate (LiNbO 3), quartz, zinc oxide (ZnO) ).
    The support substrate 20 having a coefficient of thermal expansion less than that of the donor substrate 11 is provided in a second process step (FIG. 5b). As indicated above, it may for example comprise a material selected from silicon, glass, silica, sapphire, alumina, aluminum nitride, silicon carbide.
    Prior to the assembly step, the step of introducing gaseous species is performed at the second face of the donor substrate 11, as shown in Figure 5c. It thus generates a buried zone, the thickness and depth of which is dependent on the ion implantation energy and dose, as well as the nature of the donor substrate 11. This buried zone will form the nanocavity zone 30. Depending on whether the implantation will be carried out on the whole of the second face 2 or locally, the zone 30 will be either continuous or discontinuous, in a plane parallel to the second face 2.
    The nanocavities 31 are either directly present after implantation or are formed and stabilized by a subsequent heat treatment step. This heat treatment step also has the advantage, in the present embodiment, of exodiffing all or part of the gaseous species from the donor substrate 11, prior to assembly: this can notably prevent degassing at the bonding interface. , likely to degrade its mechanical strength and / or its quality.
    A step of assembling the second face 2 of the donor substrate 11 on the support substrate 20 is then performed (Figure 5d). Molecular adhesion bonding is an advantageous technique in that it does not require adding material to assemble the surfaces. It nevertheless requires a good surface condition (good flatness, low roughness, excellent cleanliness) to give rise to a good quality assembly. The formation of the zone 30 of nanocavities 31 according to the invention does not degrade the quality of the second face 2; the step of introduction of gaseous species is defined so that the buried zone does not generate deformation or damage at the second face 2 to be assembled.
    To consolidate the bonding interface, the bonded hybrid structure 101 is advantageously subjected to a heat treatment. It should be noted that the materials of the donor substrate 11 and the support substrate 20 have very different coefficients of thermal expansion, the heat treatment applied must therefore remain at a temperature below the temperature of damage or breakage of the bonded structure 101 The temperature range will typically be from a few tens of degrees to 500 ° C.
    The manufacturing method according to this first embodiment of the invention further comprises a thinning step of the donor substrate 11, by its first face 1 ', so as to obtain a so-called useful thickness of the useful layer 10 and form the first free face 1 (Figure 5e). This useful thickness depends on the type of acoustic wave device that will be developed on the hybrid structure 100. The thinning stage may be based on the known techniques of honing ("grinding" in the English terminology), polishing ( CMP for "Chemical Mechanical Polishing") and / or chemical etching (wet or dry). These methods are particularly suited to the formation of thick useful layers, for example from a few microns to several tens of microns, and up to a few hundred microns.
    To form a useful layer 10 of small thickness, that is to say typically less than 2 microns, other methods of transfer of layers can be implemented, among which the Smart Cut ™ process. It is based on implantation of light ions of hydrogen and / or helium in the donor substrate 11 to form a weakened buried layer, at a depth with respect to the second face 2, greater than or equal to the useful thickness . This implantation step can be carried out prior to the assembly step, before or after the formation of the nanocavity zone 30.
    A detachment step, subsequent to the assembly on the support substrate 20, then makes it possible to separate a thin surface layer of the donor substrate 11 (the useful layer 10), at the level of the embrittled buried layer. Finishing steps, which may include heat treatments and / or polishing or chemical etching, finally provide the required crystalline and surface quality to the useful layer 10. This process is particularly suitable for the manufacture of thin useful layers.
    According to a second embodiment of the invention, the step of introducing the gaseous species into the useful layer 10 is made after the assembly step. A hybrid structure 100 'comprising the useful layer 10 disposed on the support substrate 20 is subjected to the step of introducing gaseous species to form the zone 30 of nanocavities 31 (Figure 6a). The energy of the ions, in the case of implantation, is advantageously chosen so that the zone 30 is formed in the lower third of the useful layer 10, close to the second face 2.
    A heat treatment may be performed to form and / or stabilize the nanocavities 31 of the zone 30. This heat treatment must take into account the difference in coefficient of thermal expansion of the materials constituting the hybrid structure 100, illustrated in FIG. 6b.
    According to a third embodiment of the invention, during the first step of supplying the method, the first face 1 of the useful layer 10 is disposed on a temporary substrate 60 (FIG. 7a). It has advantageously been reported by the Smart Cut process and therefore comprises a residue of the buried layer embrittled at its second face 2.
    Preferably, an intermediate layer 40 is deposited on the second face 2 of the useful layer 10 prior to its assembly on the support substrate 20 (FIG. 7b).
    The temporary substrate 60 is then removed, either by mechanical or chemical thinning, or by dismounting at the interface between the first face 1 of the useful layer 10 and the temporary substrate 60.
    FIG. 7c shows the hybrid structure 100 obtained: the residue of the embrittled buried layer formed during the Smart Cut process makes it possible to generate, in this embodiment, the zone 30 of nanocavities 31, close to the second face 2 of the layer useful 10.
    This third embodiment is advantageous when the coefficients of expansion (CTE) of the materials of the hybrid structure 100 make it difficult to directly apply the Smart Cut process for the transfer of a thin useful layer 10 onto the support substrate 20. case, the useful layer
    10 is first formed on a temporary substrate 60 (which may have the same CTE as the useful layer 10 or a CTE intermediate that of the useful layer 10 and that of the support substrate 20) and then transferred to the support substrate 20. L The light ion implantation required for the Smart Cut process is then used to form the nanocavity zone 31, avoiding an additional implantation step. In this third embodiment nevertheless, there is little flexibility on the functional thickness of the zone 30 and on the characteristics (dimensions, density, etc.) of the nanocavities 31, the implantation parameters being dictated in the first place by the Smart Cut process.
    Example 1
    A donor substrate 11 of LiNbO 3 is implanted at its second face 2, with helium ions, at an energy of 180 keV and a dose of 3.5 × 10 16 He / cm 2. Advantageously, a protective layer, for example S1O2, is deposited on the second face 2, prior to implantation, in order to limit the contamination of the donor substrate 11 during the implantation step.
    Such an implantation typically forms a zone 30 of nanocavities 31 of functional thickness of the order of 700 nm, at a distance of the order of 350 nm from the second face 2.
    The protective layer is removed by chemical etching.
    Heat treatment at 700 ° C. for 2 hours is carried out to stabilize the nanocavities 31 and remove all or part of the helium species from the donor substrate 11.
    The donor substrate 11 and a support substrate 20 made of silicon, for example of respective thicknesses of 350 microns and 625 microns, are then subjected to cleaning sequences, before being assembled by molecular adhesion, thus forming a bonded hybrid structure 101. The face 2 of the donor substrate 11 is of very good quality, compatible with direct bonding, the implantation of gaseous species to form the zone 30 not generating deformations or surface damage.
    Successive grinding and polishing steps are applied to the first face 1 'of the donor substrate 11, until the useful layer 10 with a useful thickness of 20 microns is obtained. The hybrid structure 100 according to the invention is thus formed.
    This structure is adapted to the development of a surface acoustic wave device 200, including in particular the formation of interdigitated metal electrodes 50 on the first face 1 of the useful layer 10. The presence of the nanocavity zone 30 according to the invention makes it possible to attenuate or even eliminate unwanted reflections of acoustic waves on the interface between the useful layer 10 and the support substrate 20: the acoustic waves propagating towards said interface are reflected in multiple directions, thus diffused by the plurality of nanocavities 31 forming the zone 30.
    Example 2
    A masking layer is formed on the second face 2 of a LiTaCU donor substrate 11, giving rise to masked regions and exposed regions. The exposed regions form, for example, circular blocks, as illustrated in plan view in FIG. 2c, separated from each other by masked regions. The diameter of the exposed regions is 5 microns, the spacing between two neighboring exposed regions is also 5 microns.
    The donor substrate 11 is then implanted at its second face 2, with helium ions, successively at several energies: 140 keV, 160 keV, 180 keV and with a dose of 2.1016 He / cnp applied for each energy.
    The masking layer is removed by chemical etching.
    A heat treatment at 580 ° C. for 2 hours is carried out to stabilize the nanocavities 31 and evacuate all or part of the gaseous species from the donor substrate 11.
    The donor substrate 11 and a silicon support substrate 20 are then subjected to cleaning sequences, before being assembled by molecular adhesion, thus forming a bonded hybrid structure 101. The face 2 of the donor substrate 11 is of very good quality, compatible with a direct bonding, the implantation of gaseous species to form the zone 30 not generating deformations or superficial damage.
    Successive grinding and polishing steps are applied to the first face 1 'of the donor substrate 11, until the useful layer 10 with a useful thickness of 20 microns is obtained. The hybrid structure 100 according to the invention is thus formed.
    This structure is adapted to the development of a surface acoustic wave device 200, including in particular the formation of interdigitated metal electrodes 50 on the first face 1 of the useful layer 10. The presence of the nanocavity zone 30 according to the invention makes it possible to attenuate or even eliminate unwanted reflections of acoustic waves on the interface between the useful layer 10 and the support substrate 20: the acoustic waves propagating towards said interface are reflected in multiple directions, thus diffused by the plurality of nanocavities 31 forming the zone 30.
    权利要求:
    Claims (13)
    [1" id="c-fr-0001]
    A hybrid structure (100) for a surface acoustic wave device comprising a useful layer (10) of piezoelectric material having a first free face (1) and a second face (2) disposed on a support substrate (20) whose coefficient thermal expansion is less than that of the useful layer (10), the hybrid structure (100) being characterized in that the useful layer (10) comprises a zone (30) of nanocavities (31).
    [2" id="c-fr-0002]
    2. Hybrid structure (100) for surface acoustic wave device according to the preceding claim, wherein the zone (30) of nanocavities (31) has a functional thickness of between 50 nm and 3 microns.
    [3" id="c-fr-0003]
    3. hybrid structure (100) for surface acoustic wave device according to one of the preceding claims, wherein the zone (30) of nanocavities (31) is at a distance of more than 50 nm from the second face (2). of the useful layer (10).
    [4" id="c-fr-0004]
    4. hybrid structure (100) for surface acoustic wave device according to one of the preceding claims, wherein the nanocavities (31) have, at least in part, a maximum dimension between 1 nm and 500 nm.
    [5" id="c-fr-0005]
    5. hybrid structure (100) for surface acoustic wave device according to one of the preceding claims, wherein the zone (30) of nanocavities (31) extends in a plane parallel to the second face (2) of the useful layer (10).
    [6" id="c-fr-0006]
    6. Hybrid structure (100) for surface acoustic wave device according to one of the preceding claims, wherein the support substrate (20) comprises a material selected from silicon, glass, silica, sapphire, alumina. , aluminum nitride, silicon carbide.
    [7" id="c-fr-0007]
    7. hybrid structure (100) for surface acoustic wave device according to one of the preceding claims, wherein the useful layer (10) comprises a piezoelectric material selected from lithium tantalate (LiTa03), lithium niobate (LiNb03 ), quartz, zinc oxide (ZnO).
    [8" id="c-fr-0008]
    8. hybrid structure (100) for surface acoustic wave device according to one of the preceding claims, comprising an intermediate layer (40) located between the second face (2) of the useful layer (10) and the support substrate (20). ).
    [9" id="c-fr-0009]
    Surface acoustic wave device (200) comprising a hybrid structure (100) according to one of the preceding claims.
    [10" id="c-fr-0010]
    A method of manufacturing a hybrid structure (100) for a surface acoustic wave device comprising: a) a step of providing a useful layer (10) of piezoelectric material having a first face (1) and a second face (2); b) a step of providing a support substrate (20) having a coefficient of thermal expansion less than that of the useful layer (10); c) a step of assembling the second face (2) of the useful layer (10) on the support substrate (20); The method is characterized in that it comprises a step of introducing gaseous species into the useful layer (10) to form a zone (30) of nanocavities (31).
    [11" id="c-fr-0011]
    11. A method of manufacturing a hybrid structure (100) according to the preceding claim, wherein the step of introducing gaseous species comprises at least one implantation of ions selected from hydrogen, helium, argon and other noble gases.
    [12" id="c-fr-0012]
    12. A method of manufacturing a hybrid structure (100) according to one of the 2 preceding claims, comprising a heat treatment step after the step of introduction of gaseous species.
    [13" id="c-fr-0013]
    13. A method of manufacturing a hybrid structure (100) according to one of the 3 preceding claims, wherein the introduction of gaseous species into the useful layer (10) is performed locally by applying a mask.
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    同族专利:
    公开号 | 公开日
    FR3052298B1|2018-07-13|
    JP2019520753A|2019-07-18|
    EP3465784A1|2019-04-10|
    CN109219896A|2019-01-15|
    US20190165252A1|2019-05-30|
    EP3465784B1|2020-04-08|
    SG11201810733PA|2018-12-28|
    KR20190014072A|2019-02-11|
    WO2017207911A1|2017-12-07|
    引用文献:
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    DE102004045181A1|2004-09-17|2006-03-23|Epcos Ag|SAW device with reduced temperature response and method of manufacture|
    US20090224853A1|2008-03-07|2009-09-10|Oh Young Joo|Piezoelectric substrate and surface acoustic wave filter using the same|
    EP2658123A1|2010-12-24|2013-10-30|Murata Manufacturing Co., Ltd.|Elastic wave device andmethod for manufacturing the same.|
    US20160065162A1|2013-04-08|2016-03-03|Soitec|Advanced thermally compensated surface acoustic wave device and fabrication|WO2020098910A1|2018-11-13|2020-05-22|Huawei Technologies Co., Ltd.|Surface acoustic wave device with phononic crystal|
    WO2020120175A1|2018-12-12|2020-06-18|RF360 Europe GmbH|Thin film saw device|JP5429200B2|2010-05-17|2014-02-26|株式会社村田製作所|Method for manufacturing composite piezoelectric substrate and piezoelectric device|
    JP5695394B2|2010-11-17|2015-04-01|日本碍子株式会社|Composite substrate manufacturing method|FR3091032B1|2018-12-20|2020-12-11|Soitec Silicon On Insulator|Method of transferring a surface layer to cavities|
    EP3896850A1|2020-04-14|2021-10-20|IQE plc|Layered structure with regions of localized strain in crystalline rare earth oxides|
    法律状态:
    2017-05-22| PLFP| Fee payment|Year of fee payment: 2 |
    2017-12-08| PLSC| Search report ready|Effective date: 20171208 |
    2018-05-25| PLFP| Fee payment|Year of fee payment: 3 |
    2020-05-20| PLFP| Fee payment|Year of fee payment: 5 |
    2021-05-27| PLFP| Fee payment|Year of fee payment: 6 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1655030A|FR3052298B1|2016-06-02|2016-06-02|HYBRID STRUCTURE FOR ACOUSTIC SURFACE WAVE DEVICE|
    FR1655030|2016-06-02|FR1655030A| FR3052298B1|2016-06-02|2016-06-02|HYBRID STRUCTURE FOR ACOUSTIC SURFACE WAVE DEVICE|
    KR1020197000090A| KR20190014072A|2016-06-02|2017-05-30|Hybrid structure for surface acoustic wave device|
    JP2018563171A| JP2019520753A|2016-06-02|2017-05-30|Hybrid structure for surface acoustic wave devices|
    US16/306,822| US20190165252A1|2016-06-02|2017-05-30|Hybrid structure for a suface acoustic wave device|
    EP17732512.3A| EP3465784B1|2016-06-02|2017-05-30|Hybrid structure for a surface acoustic wave device|
    CN201780034366.2A| CN109219896A|2016-06-02|2017-05-30|Mixed structure for surface acoustic wave device|
    PCT/FR2017/051339| WO2017207911A1|2016-06-02|2017-05-30|Hybrid structure for a surface acoustic wave device|
    SG11201810733PA| SG11201810733PA|2016-06-02|2017-05-30|Hybrid structure for surface acoustic wave device|
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