CN109450401B - Flexible single crystal lamb wave resonator and method of forming the same - Google Patents
Flexible single crystal lamb wave resonator and method of forming the same Download PDFInfo
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- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical group [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims description 14
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
- H03H9/02—Details
- H03H9/02007—Details of bulk acoustic wave devices
- H03H9/02015—Characteristics of piezoelectric layers, e.g. cutting angles
- H03H9/02039—Characteristics of piezoelectric layers, e.g. cutting angles consisting of a material from the crystal group 32, e.g. langasite, langatate, langanite
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
- H03H9/02—Details
- H03H9/02007—Details of bulk acoustic wave devices
- H03H9/02086—Means for compensation or elimination of undesirable effects
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
- H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
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- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
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Abstract
本发明提供一种柔性单晶兰姆波谐振器及其形成方法。该方法包括：提供硬质基底；在硬质基底之上形成牺牲层；在牺牲层之上形成单晶薄膜层；将单晶薄膜层划分为器件区、周围区、窗口区和锚结构，窗口区用于将器件区和周围区隔开，锚结构用于连接器件区和周围区，然后在器件区之上形成叉指电极；刻蚀去除窗口区，保留器件区、锚结构和周围区；释放去除窗口区、锚结构和器件区下方的牺牲层，以使器件区和叉指电极在锚结构的作用下悬于硬质基底上；利用印章粘附器件区和叉指电极，然后断开锚结构从而使器件区和叉指电极脱离硬质基底；提供具有顶部空腔的柔性基底；利用印章将器件区和叉指电极转移至柔性基底之上并且覆盖对准顶部空腔。
The present invention provides a flexible single crystal Lamb wave resonator and a method for forming the same. The method includes: providing a hard substrate; forming a sacrificial layer on the hard substrate; forming a single crystal thin film layer on the sacrificial layer; dividing the single crystal thin film layer into a device area, a peripheral area, a window area and an anchor structure, the window The area is used to separate the device area from the surrounding area, the anchor structure is used to connect the device area and the surrounding area, and then interdigitated electrodes are formed on the device area; the window area is removed by etching, and the device area, the anchor structure and the surrounding area are retained; Release and remove the sacrificial layer under the window area, the anchor structure and the device area, so that the device area and the interdigital electrode are suspended on the hard substrate under the action of the anchor structure; use the stamp to adhere the device area and the interdigital electrode, and then disconnect Anchor structure thereby freeing the device area and interdigital electrodes from the rigid substrate; providing a flexible substrate with a top cavity; using a stamp to transfer the device area and interdigital electrodes onto the flexible substrate and cover alignment of the top cavity.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a flexible single crystal lamb wave resonator and a forming method thereof.
Background
The novel application in the fields of Internet of things and 5G provides higher requirements for the power consumption and bandwidth of the resonator, and the lamb wave resonator which takes single crystal materials such as lithium niobate and lithium tantalate as piezoelectric films has high Kt2 and high Q value at the same time, so that the requirements of next generation of reconfigurable and multi-frequency broadband filtering can be met. Ultra-low power wake-Up receivers (Ultra-low power wake-Up receivers) are also a big research hotspot of single crystal lamb wave resonators. The conventional lamb wave resonators are based on a hard substrate, so that the requirements of the flexible electronic field (such as flexible resonators, filters, oscillators and sensors) are still not met, and therefore, a flexible lamb wave resonator is urgently needed to be developed.
Existing preparation flexibilityThe method of the device is roughly divided into two steps: firstly, a device is prepared on a hard substrate, and then the device is transferred from the hard substrate to a flexible substrate through a seal transfer method. Taking a flexible Film Bulk Acoustic Resonator (FBAR) device made of a conventional piezoelectric material (AlN or ZnO) as an example, the manufacturing process specifically comprises: (1) providing a silicon substrate, depositing SiO2 material as a sacrificial layer on the top surface of the silicon substrate, and then only preserving the SiO deposited under the device region by defining the device region2SiO of the remaining region2Removing; (2) then, sequentially forming a bottom electrode layer, a piezoelectric layer (i.e., AlN or ZnO), and a top electrode on the sacrificial layer, as shown in fig. 1; (3) because only the sacrificial layer is reserved in the device area and no sacrificial layer is reserved in other areas, the lower part of the device is suspended through a release process, and then the anchor point structure is arranged at the joint with the substrate to separate the device main body independently, and the piezoelectric layers around the device are removed; (4) the device main body is stuck by pressing the seal and then transferred to other flexible substrates.
However, devices with a single crystal lithium niobate piezoelectric layer cannot be fabricated using similar processes. The conventional sputtering, chemical vapor deposition and epitaxial growth are suitable for polycrystalline films, but are not suitable for the production of high-quality lithium niobate and lithium tantalate single crystal films. The current mature method for obtaining high-quality single crystal film is to produce lithium niobate and lithium tantalate single crystal film by crystal ion slicing technology and then bond the film on silicon chip. If a patterned sacrificial layer corresponding to a device region is formed on a hard substrate as shown in fig. 1, it is difficult to bond a single-crystal lithium niobate thin film thereon. In addition, the crystal ion slicing technology cannot control stress, so that the prepared single crystal film has residual stress, and after the cavity process is released, the single crystal film can be bent or cracked to reduce the performance of the device, and even the device is directly cracked to cause the rejection of the device. Finally, in the process of dry etching the top of the silicon substrate, due to the isotropy of the dry etching, the bottom of the released cavity is uneven, and the device is easily damaged during subsequent transfer.
Disclosure of Invention
In view of the foregoing, the present invention provides a flexible single crystal lamb wave resonator and a method of forming the same.
The forming method of the flexible single crystal lamb wave resonator provided by the first aspect of the invention comprises the following steps: providing a hard substrate; forming a sacrificial layer over the hard substrate; forming a single crystal thin film layer over the sacrificial layer; dividing the monocrystalline film layer into a device area, a peripheral area, a window area and an anchor structure, wherein the window area is used for separating the device area from the peripheral area, the anchor structure is used for connecting the device area with the peripheral area, and then interdigital electrodes are formed on the device area; etching to remove the window region, and reserving the device region, the anchor structure and the surrounding region; releasing and removing the sacrificial layer below the window area, the anchor structure and the device area so as to enable the device area and the interdigital electrode to be suspended on the hard substrate under the action of the anchor structure; adhering the device area and the interdigital electrode by using a seal, and then disconnecting the anchor structure so as to separate the device area and the interdigital electrode from the hard substrate; providing a flexible substrate having a top cavity; and transferring the device region and the interdigital electrode to the flexible substrate by using the seal and covering and aligning the device region and the interdigital electrode to the top cavity.
Optionally, after the step of forming the sacrificial layer and before the step of forming the single crystal thin film layer, further comprising: before the step of forming the single crystal thin film layer, the method further comprises the following steps: forming a metal layer under the single crystal thin film layer; after the steps of removing the window region by etching and reserving the device region, the anchor structure and the surrounding region, the method further comprises the following steps: removing the metal layer below the window region, and reserving a bottom electrode metal layer below the device region as a bottom electrode; (ii) a Adhering the bottom electrode while adhering the device region and the interdigital electrode by using a stamp; and simultaneously transferring the bottom electrode onto the flexible substrate and in covering alignment with the top cavity by using the seal to transfer the device region and the interdigital electrode onto the flexible substrate and in covering alignment with the top cavity.
Optionally, after the step of forming the single crystal thin film layer, the method further comprises: and forming an air reflecting grid above the device region and near the interdigital electrode.
Optionally, the material of the sacrificial layer is silicon dioxide or benzocyclobutene.
Optionally, the sacrificial layer has a thickness of 0.1 μm to 10 μm.
Optionally, the material of the single crystal thin film layer is lithium niobate or lithium tantalate.
Optionally, the thickness of the single crystal thin film layer is 0.1 μm to 2 μm.
Optionally, the anchor structure comprises a plurality of breakpoint structures.
Optionally, the stamp includes a press-lifting portion and an adhesion portion, wherein the press-lifting portion is located above the adhesion portion, the cross-sectional dimension of the adhesion portion is larger than the device region dimension and smaller than the inner dimension of the surrounding region, and the cross-sectional dimension of the press-lifting portion is larger than the cross-sectional dimension of the adhesion portion.
Optionally, the frequency range of the flexible single crystal resonator is between 20MHz-2 GHz.
The forming method of the flexible single crystal lamb wave resonator at least has the following advantages: (1) the anchor structure enables the piezoelectric film in the device area to be connected with the piezoelectric films in other parts, so that the device area is ensured not to float away in the release process; and meanwhile, the anchor structure also bears the release of the residual stress of the piezoelectric film after the cavity releasing process. (2) A sacrificial layer is introduced between the rigid substrate and the single crystal thin film layer, the sacrificial layer enables a device area on the rigid substrate to be suspended through a release process, and a flat plane is arranged below the device area, so that the device area cannot be damaged due to the fact that the lower plane is not flat when the soft stamp is used for stamping transfer, and the transfer success rate is improved.
The flexible single crystal lamb wave resonator provided by the second aspect of the invention is obtained by the method provided by the invention.
Drawings
The drawings are included to provide a better understanding of the invention and are not to be construed as unduly limiting the invention. Wherein:
fig. 1 is a schematic structural diagram of a conventional piezoelectric material flexible device before an unreleased cavity process;
FIG. 2 is a schematic flow diagram of a method of forming a flexible single crystal lamb wave resonator in accordance with an embodiment of the invention;
FIG. 3 is an electron diffraction diagram of a material of a lithium niobate single crystal thin film layer of an embodiment of the present invention;
FIGS. 4-13 are process schematic diagrams of a method of forming a flexible single crystal lamb wave resonator in accordance with one embodiment of the invention;
fig. 14 to 16 are schematic process diagrams of a method for forming a flexible single crystal lamb wave resonator according to a second embodiment of the invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.
The invention aims to provide a single crystal lamb wave resonator with a cavity flexible substrate and a forming method thereof. The single-crystal lamb wave resonator with the cavity flexible substrate has the characteristics of high performance of the single-crystal resonator and bending of a flexible device, so that the single-crystal lamb wave resonator has a wider application field and a very good application prospect, and compared with a traditional resonator, the lamb wave resonator with the flexible substrate has the advantages as shown in table 1.
TABLE 1 comparison of conventional lamb wave resonators with single crystal lamb wave resonators on flexible substrates
| Technical index | Traditional lamb wave resonator | Single crystal lamb wave resonator with flexible substrate |
| Piezoelectric material | AlN, ZnO and the like | LiNO3，LiTaO3AlN, ZnO and the like |
| Base material | Silicon/sapphire, etc | PET/PI and the like |
| Piezoelectric film production process | Sputtering/chemical vapor deposition | thinning/MOCVD after single crystal growth |
| Class of crystal | Polycrystalline | (Single Crystal) |
| Dislocation density | >1012Per cm2 | ＜1012Per cm2 |
| Acoustic wave loss of material | Height of | Is low in |
| Electromechanical coupling coefficient of material | Medium and high grade | Height of |
| Electromechanical coupling coefficient of resonator | Lower (<3％) | High (>20％) |
| Relative bandwidth of Filter (FBW) | Narrow and narrow | Width of |
| Filter Insertion Loss (IL) | Big (a) | Small |
| Flexibility | Is not bendable | Can be bent |
| Field of application | Field of conventional electronics | Traditional electronics field + flexible electronics field |
Fig. 2 is a schematic flow diagram of a method of forming a flexible single crystal lamb wave resonator in accordance with an embodiment of the invention. As shown in fig. 2, the method comprises the steps of:
step S1: a hard substrate is provided.
Step S2: a sacrificial layer is formed over a hard substrate.
Step S3: a monocrystalline film layer is formed over the sacrificial layer.
Step S4: the single crystal thin film layer is divided into a device area, a peripheral area, a window area and an anchor structure, the window area is used for separating the device area from the peripheral area, the anchor structure is used for connecting the device area and the peripheral area, and then the interdigital electrodes are formed on the device area.
Step S5: and etching to remove the window region and reserving the device region, the anchor structure and the surrounding region.
Step S6: and releasing and removing the sacrificial layer below the window area, the anchor structure and the device area so as to enable the device area and the interdigital electrode to be suspended on the hard substrate under the action of the anchor structure.
Step S7: and adhering the device area and the interdigital electrode by using a stamp, and then disconnecting the anchor structure so as to separate the device area and the interdigital electrode from the hard substrate.
Step S8: a flexible substrate having a top cavity is provided.
Step S9: and transferring the device region and the interdigital electrodes onto the flexible substrate by using a stamp and covering the aligned top cavity.
As can be seen from the above, the method for forming a flexible single-crystal lamb wave resonator according to the embodiment of the invention has at least the following advantages: (1) the anchor structure enables the piezoelectric film in the device area to be connected with the piezoelectric film in the surrounding area, so that the device area is ensured not to float away in the releasing process, and meanwhile, the anchor structure is also used for bearing and releasing the residual stress of the piezoelectric film after the cavity releasing process. (2) The sacrificial layer is introduced between the rigid substrate and the single crystal thin film layer and can be removed through a release process, so that the device area is suspended on the rigid substrate, a flat plane is arranged below the device area, the device area is prevented from being damaged due to the fact that the plane below the device area is not flat when the device area is stamped and transferred by a stamp, and the transfer success rate is improved.
In the method for forming a flexible single crystal lamb wave resonator according to the embodiment of the invention, before the step of forming the single crystal thin film layer, the method further includes: forming a metal layer under the single crystal thin film layer; after the steps of removing the window region by etching and reserving the device region, the anchor structure and the surrounding region, the method further comprises the following steps: removing the metal layer below the window region, and reserving a bottom electrode metal layer below the device region as a bottom electrode; adhering a bottom electrode while adhering the device region and the interdigital electrode by using a stamp; and simultaneously transferring the device region and the interdigital electrodes onto the flexible substrate and covering the alignment top cavity by using the stamp, and transferring the bottom electrode onto the flexible substrate and covering the alignment top cavity. In this embodiment, the presence of the bottom electrode can improve the resonator performance.
In the method for forming a flexible single crystal lamb wave resonator according to the embodiment of the invention, after the step of forming the single crystal thin film layer, the method may further include: and forming an air reflecting grid on the device region and near the interdigital electrode. The presence of an air reflecting grating may improve the performance of the device.
In the method for forming the flexible single-crystal lamb wave resonator according to the embodiment of the invention, the sacrificial layer may be made of silicon dioxide or Benzocyclobutene (BCB).
In the method of forming the flexible single crystal lamb wave resonator according to the embodiment of the invention, the thickness of the sacrificial layer may be 0.1 μm to 10 μm. If the thickness of the sacrificial layer is less than 0.1 μm, the single crystal thin film is difficult to bond to the sacrificial layer; if the thickness of the sacrificial layer is higher than 10 μm, it is not beneficial to remove the sacrificial layer by a subsequent release process.
In the method for forming the flexible single crystal lamb wave resonator according to the embodiment of the invention, the material of the single crystal thin film layer may be lithium niobate or lithium tantalate.
In the method of forming the flexible single crystal lamb wave resonator according to the embodiment of the invention, the thickness of the single crystal thin film layer may be 0.1 μm to 2 μm. If the thickness of the single crystal film layer is less than 0.1 mu m, the manufacturing process difficulty is too large, and the device is extremely easy to damage due to the too thin subsequent transfer step; if the thickness of the single crystal thin film layer is more than 2 μm, the flexibility of the device may be deteriorated.
In the method of forming the flexible single crystal lamb wave resonator according to the embodiment of the invention, the anchor structure may include a plurality of breakpoint structures. A plurality of breakpoint structures can make the anchor structure slightly connect device area and surrounding area, have ensured that the fracture of anchor structure when receiving external force fracture is neat, and the stress is released simultaneously in the convenient separation. Preferably, the anchor structure is generally designed to be elongate in shape, for example with an aspect ratio greater than 10: 1.
In the method of forming a flexible single crystal lamb wave resonator according to an embodiment of the present invention, the stamp may include a press-up portion and an adhesion portion. Wherein the pressure increasing portion is located above the adhesion portion. The adhesion portion has a cross-sectional dimension greater than a device region dimension and less than an inner dimension of the surrounding region. The cross-sectional dimension of the press-lifting part is larger than that of the adhesion part. Compared with the existing common cylindrical stamp, the common cylindrical stamp is large, and an electrode layer and a piezoelectric layer outside a device area are easily adhered together, so that the damage rate of the device is greatly increased. The bottom surface of the stamp shape of the embodiment of the invention is matched with the size of the device area, so that the release window does not need to be opened too wide, more devices can be manufactured in unit area, the utilization rate of the single crystal piezoelectric material can be improved, and the economic benefit is increased.
In the method for forming the flexible single-crystal lamb wave resonator, the frequency range of the flexible single-crystal resonator is 20MHz-2 GHz.
The invention also provides a flexible single crystal lamb wave resonator which is obtained by the method disclosed by the invention.
For better understanding of those skilled in the art, the following detailed description will be given of specific processes of the method for forming a flexible single crystal lamb wave resonator according to the embodiments of the present invention, with reference to the accompanying drawings.
Example 1
A hard substrate 101 of a silicon material having a thickness of about 400 μm is provided, followed by forming a sacrificial layer 102 of a silicon dioxide material having a thickness of 0.1 to 10 μm (preferably 1 μm) on the hard substrate 101 by a chemical vapor deposition process, and then bonding a single crystal thin film layer 103 of a lithium niobate material having a thickness of 0.1 to 2 μm (preferably 0.7 μm) on the sacrificial layer 102 by an ion slicing process.
It should be explained that the ion slicing process specifically refers to implanting He on the front side of the donor lithium niobate wafer+Ions, so that He+Ion implantation into a certain depth of a lithium niobate wafer and formation of a He+Ion layer, and then heating and annealing to obtain He+He molecule bubbles are formed, thereby peeling off the thin film layer. Finally, the lithium niobate thin film layer is thinned to the specified thickness of 0.1-2 μm, preferably 0.7 μm, by utilizing a Chemical Mechanical Polishing (CMP) process). The electron diffraction pattern of the material of the single crystal thin film layer 103 obtained by the process is shown in fig. 3. Use throughAnd a radio electron microscope for studying the lattice arrangement of the piezoelectric film by electron diffraction. The bragg diffraction intensity is a direct result of the periodic arrangement of the crystal lattice, the better the periodicity, the more ordered the arrangement, the greater the bragg diffraction intensity. In fig. 3, the reciprocal lattice is clear, no amorphous ring appears, and the diffraction pattern shows a hexagonal lattice pattern, indicating that the lithium niobate thin film has a single crystal structure.
The three-layer material structure thus far processed is shown in fig. 4.
Providing a device layout as shown in fig. 5, the single crystal thin film layer 103 in the layout is divided into a device region 103A, a peripheral region 103B, a window region 103C, and an anchor structure 103D. Window region 103B separates device region 103A from surrounding region 103B, and anchor structure 103D connects device region 103A and surrounding region 103B. The size of window area 103C needs reasonable setting, avoids the raw materials extravagant. The anchor structure 103D is generally provided in an elongated shape, and preferably several breakpoint structures are provided on the anchor structure 103D, as shown in fig. 6.
Next, a plurality of interdigital electrodes 104 are formed on the single crystal thin film layer 103. The number of the interdigital electrodes is not limited, and the signal terminal (S) and the ground terminal (G) may be alternately arranged, as shown in fig. 7. The interdigital electrodes 104 are used to generate a transverse electric field to excite the resonator to operate.
In addition, an air reflective grid 105 may be formed on the device region 103A of the single crystal thin film layer 103 and near the interdigital electrode 104, as shown in fig. 5. The air reflection grating 105 can reflect the sound waves transmitted to the reflection grating, and the performance of the resonator is improved.
And etching to remove the window region 103C of the monocrystalline film layer. Then, a release process is used to remove the sacrificial layer, i.e. the sacrificial layer 102 is removed by soaking in a hydrofluoric acid solution or placing in a gaseous hydrofluoric acid machine to obtain a cavity. It should be noted that although the initial etching of HF is performed by using silicon dioxide under the window region 103C, HF may slowly diffuse during the etching process, gradually releasing the silicon dioxide under the device region 103A, and the anchor structure 103D is responsible for releasing the residual stress of the single crystal thin film, thereby preventing the device region 103A from cracking due to the release of the residual stress. To this end, a cavity is formed under the device region 103A, and the device structure is as shown in fig. 8a and 8 b. Specifically, fig. 8a is a cross-sectional view of the device without passing through the anchor structure, which corresponds to a cross-sectional view in the horizontal direction of the layout shown in fig. 5; fig. 8b is a cross-sectional view of the device through the anchor structure, which corresponds to a cross-sectional view in the vertical direction of the layout shown in fig. 5. It should be noted that for simplicity, only the interdigital electrodes 104 are shown in fig. 8a and 8b, and the air reflection grid is omitted. As can be seen in fig. 8a and 8B, the device region 103A is suspended above the hard substrate 101 and is connected to the surrounding region 103B by means of anchor structures 103D. The top of the hard substrate 101 is flat and smooth.
A transfer stamp is provided, the cross-sectional view of which is shown in fig. 9a, and the top view of which is shown in fig. 9 b. The transfer stamp includes an upper press-lifting portion a and a lower adhering portion B. The cross-sectional dimension of adhesion portion a needs to be slightly larger than device region 103A and smaller than the inner dimension of surrounding region 103B, which ensures effective adhesion of the device region while not excessively adhering to the surrounding region. The size of the cross section of the pressing part B is larger than that of the cross section of the adhesion part A, so that the mechanical arm can clamp and transfer the seal conveniently.
Note that the interdigital electrode 104 and the structural air reflection gate 105 are always located above the device region 103A during the whole stamp transfer process. Since the interdigital electrodes 104 and the structural air reflection grid 105 have a relatively thin thickness, they are omitted from the drawings of the following part of the specification and are not shown.
As shown in fig. 10, after aligning the transfer stamp with the device region 103A, a downward pressure is applied, so that the device region 103A adheres to the transfer stamp, and simultaneously releases the growth stress of the single crystal film, thereby preventing the device region 103A from cracking due to residual stress. The top of the hard substrate 101 is flat so that the device region 103A remains intact when pressed to the top of the hard substrate 101.
As shown in fig. 11, the transfer stamp is pulled and anchor structure 103D is forced open, thereby releasing device region 103A from the original hard substrate 101.
A flexible substrate 106 having a top cavity is provided. As shown in fig. 12 a-12 c, device region 103A is then transferred onto flexible substrate 106 using a transfer stamp and covering the aligned top cavity. The resulting device is shown in fig. 13.
Example 2
First, a four-layer structure including a hard base layer 101, a sacrificial layer 102, a metal layer 107 (having a thickness of about 0.1 μm), and a single crystal thin film layer 103 as shown in fig. 14 is formed in this order from bottom to top. Then, the single crystal thin film was divided into regions, windows were etched, and cavities were released by referring to the procedure in example 1. The release process removes the silicon dioxide of the sacrificial layer 102. referring to fig. 15, a bottom electrode 107' is formed under the device region 103A. Continuing with the procedure of example 1, a stamp transfer was performed to transfer the resonator structure from the rigid substrate to the flexible substrate with the top cavity. The resulting device is shown in fig. 16.
The above-described embodiments should not be construed as limiting the scope of the invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions can occur, depending on design requirements and other factors. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (11)
1. A method of forming a flexible single crystal lamb wave resonator comprising:
providing a hard substrate;
forming a sacrificial layer over the hard substrate;
forming a single crystal thin film layer over the sacrificial layer;
dividing the monocrystalline film layer into a device area, a peripheral area, a window area and an anchor structure, wherein the window area is used for separating the device area from the peripheral area, the anchor structure is used for connecting the device area with the peripheral area, and then interdigital electrodes are formed on the device area;
etching to remove the window region, and reserving the device region, the anchor structure and the surrounding region;
releasing and removing the sacrificial layer below the window area, the anchor structure and the device area so as to enable the device area and the interdigital electrode to be suspended on the hard substrate under the action of the anchor structure;
adhering the device area and the interdigital electrode by using a seal, and then disconnecting the anchor structure so as to separate the device area and the interdigital electrode from the hard substrate;
providing a flexible substrate having a top cavity;
and transferring the device region and the interdigital electrode to the flexible substrate by using the seal and covering and aligning the device region and the interdigital electrode to the top cavity.
2. The method of claim 1,
before the step of forming the single crystal thin film layer, the method further comprises the following steps: forming a metal layer under the single crystal thin film layer;
after the steps of removing the window region by etching and reserving the device region, the anchor structure and the surrounding region, the method further comprises the following steps: removing the metal layer below the window region, and reserving a bottom electrode metal layer below the device region as a bottom electrode;
adhering the bottom electrode while adhering the device region and the interdigital electrode by using a stamp;
and simultaneously transferring the bottom electrode onto the flexible substrate and in covering alignment with the top cavity by using the seal to transfer the device region and the interdigital electrode onto the flexible substrate and in covering alignment with the top cavity.
3. The method according to claim 1 or 2, further comprising, after the step of forming the single crystal thin film layer: and forming an air reflecting grid above the device region and near the interdigital electrode.
4. The method according to claim 1 or 2, wherein the material of the sacrificial layer is silicon dioxide or benzocyclobutene.
5. The method of claim 1 or 2, wherein the sacrificial layer has a thickness of 0.1 μm to 10 μm.
6. The method according to claim 1 or 2, wherein the material of the single crystal thin film layer is lithium niobate or lithium tantalate.
7. The method according to claim 1 or 2, wherein the thickness of the single crystal thin film layer is 0.1 μm to 2 μm.
8. A method according to claim 1 or 2, wherein the anchor structure comprises a plurality of breakpoint structures.
9. The method of claim 1 or 2, wherein the stamp includes a press-up portion and an adhesive portion, wherein the press-up portion is located over the adhesive portion, the adhesive portion cross-sectional dimension is greater than the device region dimension and less than the inner dimension of the surrounding region, the press-up portion cross-sectional dimension is greater than the adhesive portion cross-sectional dimension.
10. The method of claim 1 or 2, wherein the flexible single crystal resonator has a frequency in the range of 20MHz-2 GHz.
11. A flexible single crystal lamb wave resonator obtained by the method of any one of claims 1 to 10.
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| CN201811102525.0A CN109450401B (en) | 2018-09-20 | 2018-09-20 | Flexible single crystal lamb wave resonator and method of forming the same |
| PCT/CN2018/110929 WO2020056835A1 (en) | 2018-09-20 | 2018-10-19 | Flexible single-crystal lamb wave resonator, and production method therefor |
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| CN201811102525.0A CN109450401B (en) | 2018-09-20 | 2018-09-20 | Flexible single crystal lamb wave resonator and method of forming the same |
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| CN111431501B (en) * | 2020-03-31 | 2023-09-29 | 中国科学院上海微系统与信息技术研究所 | Lamb wave resonator and preparation method thereof |
| CN111555733A (en) * | 2020-05-26 | 2020-08-18 | 北京航天微电科技有限公司 | Lamb wave resonator structure and preparation method thereof |
| CN113037245B (en) * | 2021-03-11 | 2023-02-03 | 天津大学 | Quartz resonator based on piezoelectric thin film transduction and electronic equipment |
| CN113171545B (en) * | 2021-04-12 | 2023-04-07 | 天津大学 | Micro-robot propulsion device in liquid environment |
| CN113381720B (en) * | 2021-06-29 | 2023-12-22 | 南通大学 | Two-dimensional modal lamb wave resonance structure, lamb wave resonator comprising same and preparation method thereof |
| CN114301412B (en) * | 2021-12-29 | 2024-04-30 | 苏州达波新材科技有限公司 | Lamb wave acoustic wave device with improved substrate structure and manufacturing method thereof |
| CN116318023B (en) * | 2023-04-04 | 2024-08-16 | 中国科学院上海微系统与信息技术研究所 | Lamb wave resonator and filter |
| CN116865701A (en) * | 2023-05-19 | 2023-10-10 | 南京大学 | Lamb wave resonator containing through hole |
| CN117176104B (en) * | 2023-11-01 | 2024-01-30 | 镭友芯科技(苏州)有限公司 | Resonator based on lithium tantalate film and method of forming same |
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| CN109450401A (en) | 2019-03-08 |
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