CN113922782A

CN113922782A - Preparation method of temperature compensation surface acoustic wave device and device

Info

Publication number: CN113922782A
Application number: CN202111213290.4A
Authority: CN
Inventors: 姚远; 付先; 肖力; 龙铮; 陈曦; 韩超
Original assignee: Maxscend Microelectronics Co ltd
Current assignee: Maxscend Microelectronics Co ltd
Priority date: 2021-10-19
Filing date: 2021-10-19
Publication date: 2022-01-11

Abstract

The invention discloses a temperature compensation surface acoustic wave device and a preparation method thereof, wherein the temperature compensation surface acoustic wave device comprises: the piezoelectric substrate comprises a piezoelectric substrate, a load layer, an interdigital transducer, a temperature compensation layer and a passivation layer, wherein the load layer is positioned on the upper surface layer of the piezoelectric substrate or extends a certain distance from the upper surface layer of the piezoelectric substrate to the interior of the piezoelectric substrate; the temperature compensation layer is located on the interdigital transducer, and the passivation layer is located on the temperature compensation layer. The temperature compensation surface acoustic wave device has flexible design and simple process, can inhibit a transverse mode, and the Q value of the manufactured resonator is high.

Description

Preparation method of temperature compensation surface acoustic wave device and device

Technical Field

The invention relates to the technical field of surface acoustic wave devices, in particular to a method for preparing a temperature compensation surface acoustic wave and a device prepared according to the method.

Background

In today's mobile communication systems, radio frequency filters, in particular surface acoustic wave filters, play an important role. It can eliminate out-of-band interference and noise to meet the signal-to-noise ratio requirements of communication systems and protocols. With the increasingly complex communication protocols, the number of frequency bands which a terminal needs to support is increasing, the number of required filters is increasing, the requirements on the electrical performance in a pass band and the suppression outside the pass band are also increasing, especially the requirements on mutual suppression among the frequency bands are also becoming stricter, and the design challenge of the surface acoustic wave filter is increased dramatically. A common Surface Acoustic Wave filter (STD-SAW) adopts LiTaO3 as a chip substrate material, is sensitive to temperature change, and has a temperature coefficient of about-40 ppm/K. The chip temperature coefficient of the LiNbO3 material serving as a substrate reaches-75 ppm/K. Obviously, the characteristic of the electrical property changing sharply due to the temperature change cannot meet the requirement of the communication system for temperature stability and the like. The technical research for maintaining the frequency temperature stability of the surface acoustic wave filter in a wider temperature range has become one of the key problems of the current surface acoustic wave filter technology development and device application.

In order to meet the requirement of the communication system for temperature stability, it is usually necessary to cover the surface of an Interdigital transducer (IDT) with a positive temperature coefficient material to counteract the temperature drift of the substrate material. However, after a layer of temperature compensation material for temperature compensation is plated on the surface of a chip using a high coupling coefficient substrate material, although the temperature characteristics are greatly improved, the change of the chip performance is brought, and wave modes of other modes exist simultaneously in the structure, so that the main wave mode in the original device is influenced, more fine ripples appear in the pass band of the surface acoustic wave device, or the insertion loss of the pass band is increased. This phenomenon has a bad influence on the performance of the surface acoustic wave filter.

Aiming at the adverse effect, some manufacturers widen the line width at the tail end of the IDT metal finger, reduce the propagation speed of surface acoustic waves in the head area of the finger, and achieve the purpose of inhibiting clutter in a transverse mode. However, in this structure, since the width of the finger is increased only a little at a single layer of metal, the propagation speed of the surface acoustic wave in the end region of the finger is increased to a limited extent, and thus the clutter suppression effect is also limited. In addition, some manufacturers add a second layer of metal at the end of the first layer of metal finger strip of the IDT, considering that the second layer of metal has a smaller width than the first layer of metal finger strip due to the requirement of photoetching alignment precision, the thickness of the second layer needs to be increased to achieve the purposes of reducing the SAW propagation speed of the end area of the finger strip and inhibiting the clutter in the transverse mode, and the process difficulty is increased due to the small and thick second layer of metal. There is a need to develop new structures and fabrication methods that overcome the problems of the two structures.

Disclosure of Invention

The invention aims to at least solve the technical problems in the prior art, and particularly innovatively provides a method for preparing a temperature compensation surface acoustic wave device and the device.

In order to achieve the above object of the present invention, according to a first aspect of the present invention, there is provided a temperature-compensated surface acoustic wave device comprising:

a piezoelectric substrate;

the load layer is positioned on the upper surface layer of the piezoelectric substrate or extends a certain distance from the upper surface layer of the piezoelectric substrate to the interior of the piezoelectric substrate, the load layer comprises a plurality of load blocks, and each load block is positioned in a region corresponding to the finger tip of the interdigital transducer;

the finger strip end of the interdigital transducer is connected with the load block and is not covered, and the load block is partially covered or fully covered;

a temperature compensation layer located over the interdigital transducer; and

a passivation layer over the temperature compensation layer.

The temperature compensation surface acoustic wave device can restrain a transverse mode, and the Q value of a manufactured resonator is high.

According to a preferred embodiment of the invention, the interdigital transducer is also provided with a load layer in the area of the body of the adjacent finger corresponding to the position of the end of the finger.

According to another preferred embodiment of the present invention, the shape of the load block is a triangle, a square, or a rectangle, or an ellipse, or a circle, or a trapezoid, or a polygon with more than four sides; the different load blocks are the same size, are not identical or are not identical.

According to yet another preferred embodiment of the invention, the material of the load block is a metal, or a combination of metal materials, or a metal oxide.

According to yet another preferred embodiment of the invention, the load mass has a width which is greater than the width of the finger or the load mass is located in the region of the finger tip.

According to a preferred embodiment of the invention, the number of load blocks of each finger end is one, or a plurality of blocks arranged transversely, or a plurality of blocks arranged longitudinally, or a plurality of blocks arranged in a curved shape.

According to another preferred embodiment of the invention, the loading block length of each finger tip is 0.2-1 lambda, the lambda being the wavelength of the surface acoustic wave.

The invention has flexible structure design.

According to a preferred embodiment of the present invention, the thickness of the temperature compensation layer is 500nm to 2000 nm. Thereby canceling out the negative temperature coefficient of the piezoelectric substrate.

According to a preferred embodiment of the present invention, the reflection grating of the temperature compensated saw device is also provided with a load block, the load block is located at a position where the metal finger of the reflection grating corresponds to the end of the transducer finger, and the load block is made of metal. The transverse mode suppression effect is improved.

According to a preferred embodiment of the present invention, load blocks are connected between the metal finger gaps of the reflective grating of the temperature compensated saw device, the load blocks are made of metal, and the number of the load blocks between the reflective grating finger gaps is gradually reduced from the edge to the direction of the transducer; the different load blocks are the same size, are not identical or are not identical. The reflecting grating design, in which the propagating wave speed is more uniform, avoids causing distortion of the filter performance.

According to another preferred embodiment of the present invention, the load blocks connect the reflective gratings to form an arc-shaped reflective surface or a chamfer reflective surface. The influence of the clutter on the performance of the filter passband can be effectively reduced, and some fine ripples of the passband or some burrs of the transition band of the filter are eliminated.

In order to achieve the above object of the present invention, according to a second aspect of the present invention, there is provided a method of manufacturing a temperature compensated surface acoustic wave device, comprising the steps of:

s1, preparing a piezoelectric substrate material;

s2, photoetching the surface of the piezoelectric substrate material, and preparing a load block on the surface of the piezoelectric substrate material;

s3, photoetching and preparing an interdigital transducer and a reflecting grating;

s4, preparing a temperature compensation layer with a positive temperature coefficient on the upper end face of the interdigital transducer;

and S5, preparing a passivation layer on the temperature compensation layer.

The preparation method has the advantages of simple process, flexible design, good transverse mode suppression effect and high Q value of the manufactured resonator.

According to another preferred embodiment of the present invention, the step S2 may be replaced with: and photoetching the surface of the piezoelectric substrate material, etching the piezoelectric substrate to form a groove, and forming a load block in the groove. The flexibility of design is improved.

Drawings

FIG. 1 is a graph comparing admittance curves of a TC-SAW resonator with and without a loading mass in accordance with a preferred embodiment of the present invention;

fig. 2 is a schematic diagram of a load block structure (one) to a structure (six) in a preferred embodiment of the present invention, wherein fig. 2(a) is a schematic diagram of the structure (one), fig. 2(b) is a schematic diagram of the structure (two), fig. 2(c-1) is a schematic diagram of an embodiment of the structure (three), fig. 2(c-2) is a schematic diagram of another embodiment of the structure (three), fig. 2(d) is a schematic diagram of the structure (four), fig. 2(e-1) is a schematic diagram of an embodiment of the structure (five), fig. 2(e-2) is a schematic diagram of another embodiment of the structure (five), fig. 2(f-1) is a schematic diagram of an embodiment of the structure (six), and fig. 2(f-2) is a schematic diagram of another embodiment of the structure (six);

FIG. 3 is a schematic illustration of a substrate material prepared in a preferred embodiment of the invention;

FIG. 4 is a schematic illustration of the coating of photoresist on the substrate shown in FIG. 3;

FIG. 5 is a schematic illustration of the structure of FIG. 4 after completion of a photolithography process and fabrication of a loading layer material;

FIG. 6 is a schematic view of the structure shown in FIG. 5 after removing the photoresist and the metal on the photoresist to form a loading layer;

FIG. 7 is a schematic view of a support layer prepared in a preferred embodiment of the present invention, wherein FIG. 7(a) is a schematic view of a support block prepared at a finger tip position and a position corresponding to a finger tip of a reflective grating, and FIG. 7(b) is a schematic view of a support block prepared at a finger tip position, an adjacent body region of a finger corresponding to the finger tip position, and a position corresponding to the finger tip of the reflective grating;

fig. 8 is a schematic view of a supporting layer manufactured in another preferred embodiment of the present invention, wherein fig. 8(a) is a schematic view of manufacturing a supporting block between metal fingers of a partial edge reflective grating and at finger tip positions, and fig. 8(b) is a schematic view of manufacturing a supporting block between metal fingers of a total reflective grating, at finger tip positions and in adjacent finger body regions corresponding to the finger tip positions;

fig. 9 is a schematic structural diagram of forming an interdigital finger and a reflective gate on the structure shown in fig. 7 according to a preferred embodiment of the present invention, wherein fig. 9(a) is a schematic structural diagram of forming an interdigital finger and a reflective gate on the structure shown in fig. 7(a), and fig. 9(b) is a schematic structural diagram of forming an interdigital finger and a reflective gate on the structure shown in fig. 7 (b);

fig. 10 is a schematic structural diagram of forming an interdigital finger and a reflective gate on the structure shown in fig. 8 according to another preferred embodiment of the present invention, wherein fig. 10(a) is a schematic structural diagram of forming an interdigital finger and a reflective gate on the structure shown in fig. 8(a), and fig. 10(b) is a schematic structural diagram of forming an interdigital finger and a reflective gate on the structure shown in fig. 8 (b);

fig. 11 is a schematic structural view of an interdigital finger and a reflective grating formed in accordance with a preferred embodiment of the present invention, wherein fig. 11(a) is a schematic view of a loading block fabricated on a finger tip position and a reflective grating, and fig. 11(b) is a schematic view of a loading block fabricated on a finger tip position, an adjacent finger body region corresponding to the finger tip position, and a reflective grating;

FIG. 12 is a schematic structural view of a temperature compensation layer after being prepared according to a preferred embodiment of the present invention;

FIG. 13 is a schematic diagram of a structure after planarization of a temperature compensation layer in accordance with a preferred embodiment of the present invention;

FIG. 14 is a schematic diagram of a structure after a passivation layer is formed on a temperature compensation layer in accordance with a preferred embodiment of the present invention;

FIG. 15 is a schematic cross-sectional view of a temperature compensated SAW resonator in accordance with a preferred embodiment of the present invention;

FIG. 16 is a schematic cross-sectional view of a temperature compensated SAW resonator in accordance with another preferred embodiment of the present invention;

FIG. 17 is a schematic cross-sectional view of a temperature compensated surface acoustic wave resonator in accordance with yet another preferred embodiment of the invention;

FIG. 18 is a graph of simulated admittance magnitude values for a resonator fabricated in accordance with a preferred embodiment of the invention at different loadblock lengths;

fig. 19 is a graph of real simulated admittance for a resonator at different loadblock lengths in a preferred embodiment of the invention.

Reference numerals: 1 a piezoelectric substrate; 2, a metal electrode; 3, a load block; 4 a temperature compensation layer; 5 passivation layer.

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 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 only and should not be construed as limiting the invention.

In the description of the present invention, it is to be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used merely for convenience of description and for simplicity of description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, configuration, and operation in a particular orientation, and therefore, are not to be construed as limiting the present invention.

In the description of the present invention, unless otherwise specified and limited, it is to be noted that the terms "mounted," "connected," and "connected" are to be interpreted broadly, and may be, for example, a mechanical connection or an electrical connection, a communication between two elements, a direct connection, or an indirect connection via an intermediate medium, and specific meanings of the terms may be understood by those skilled in the art according to specific situations.

The invention provides a temperature compensation surface acoustic wave device, which comprises a piezoelectric substrate, wherein in the implementation mode, the piezoelectric substrate can be any substrate material which can be used by the surface acoustic wave device, and can be specifically but not limited to materials such as LiTaO3 (lithium tantalate), LiNbO3 (lithium niobate), quartz and the like, and the substrate material can be any cut type which can be used by the surface acoustic wave device.

The surface wave device of the present embodiment further includes a load layer and an interdigital transducer, the load layer is located on the upper surface layer of the piezoelectric substrate or extends a certain distance from the upper surface layer of the piezoelectric substrate to the inside of the piezoelectric substrate, the load layer includes a plurality of load blocks, the load blocks are located in a region corresponding to the ends of the interdigital transducer fingers, and the load blocks may be one or formed by a plurality of sub-blocks. The specific interdigital transducer comprises two bus bars and a plurality of interdigital connected with the bus bars, wherein the interdigital connected with different bus bars are distributed in a staggered mode and have intervals, and reflecting grids can be arranged at two ends of the transducer.

The surface acoustic wave device also comprises a temperature compensation layer, wherein the temperature compensation layer is positioned on the interdigital transducer, the material of the temperature compensation layer can be silicon dioxide, germanium dioxide and other materials with positive temperature coefficients, and the thickness of the temperature compensation layer is preferably 500 nm-2000 nm. And a passivation layer can be prepared on the temperature compensation layer, and the negative temperature coefficient of the original piezoelectric substrate is counteracted by controlling the thickness of each layer, so that the superior performances of smaller temperature coefficient (-15ppm/K to-25 ppm/K), more stable frequency and higher Q value are realized. Due to the addition of the temperature compensation layer, if the conventional SAW design method is still used, the resonator and the RF filter will have strong transverse mode ripples, the passband noise will be severe, and the performance of the whole device will be deteriorated, as shown by the dotted lines (line a and line B) in fig. 1, and more parasitic resonance peaks will appear. By providing the load layer in the temperature compensated surface acoustic wave device of the present invention, as shown by the solid line in fig. 1, the effect of improving the suppression of the transverse mode is very significant in the amplitude value (line C) and the real part (line D) of the resonator admittance curve. The method can be widely applied to TC-SAW (Temperature Compensated Surface Acoustic Wave) structures and other structures with thick film covering layers.

In the present embodiment, the number of the load blocks at each finger tip is one; in another preferred embodiment, the load block comprises a plurality of sub-blocks arranged in a transverse direction, or a plurality of sub-blocks arranged in a longitudinal direction, or a plurality of sub-blocks arranged in a curved shape. Preferably, n load block sub-blocks with intervals are arranged, wherein n is a positive integer and is more than or equal to 2, and the n load block sub-blocks adopt one of the following structures:

structure (i): as shown in fig. 2(a), n load block sub-blocks are arranged in a lateral direction (in this embodiment, a lateral direction refers to a direction perpendicular to the interdigital fingers, and a longitudinal direction refers to a direction parallel to the interdigital fingers).

Structure (ii): as shown in FIG. 2(b), n load block sub-blocks are arranged transversely, n is more than or equal to 3, and the n load block sub-blocks cover the end area of the finger strip and are retracted longitudinally relative to the end of the finger strip. Specifically, the n load block sub-blocks may be located in the region corresponding to the finger tip or may exceed the region corresponding to the finger tip in the transverse direction, and in a preferred embodiment, as shown in fig. 2(b), the middle load block sub-block is located in the region corresponding to the finger tip, and the load block sub-blocks on the two sides exceed the regions corresponding to the finger tip.

Structure (iii): as shown in fig. 2(c-1) and fig. 2(c-2), the n load block sub-blocks are arranged longitudinally, as shown in the figure, the n load block sub-blocks are sequentially arranged along the extending direction of the finger, the n load block sub-blocks cover the end area of the finger and protrude out of the end of the finger longitudinally and/or transversely, specifically, the n load block sub-blocks can only protrude out of the end of the finger longitudinally, and are level with the finger or smaller than the area where the finger is located transversely; it may also project beyond the ends of the fingers only in the transverse direction, be longitudinally flush with the fingers or be recessed a distance from the ends of the fingers, as shown in fig. 2(c-2), or project beyond the ends of the fingers in both the longitudinal and transverse directions, as shown in fig. 2 (c-1).

Structure (iv): as shown in fig. 2(d), the n load block sub-blocks are arranged longitudinally, and the n load block sub-blocks cover the end area of the finger and are located within the end range of the finger.

Structure (v): as shown in fig. 2(e-1) and 2(e-2), the n load block sub-blocks are disposed in an inclined manner or in a curved manner, in the present invention, the load block sub-blocks are disposed in an inclined manner or in a curved manner, which means that the connecting line of the central points of the load block sub-blocks is in an inclined state or a curved state relative to the finger, and the n load block sub-blocks cover the end area of the finger and protrude out of the end of the finger in the longitudinal direction and/or the transverse direction. The finger strips are arranged on the finger strips, and the finger strips are arranged on the finger strips; it may also project beyond the ends of the fingers only in the transverse direction, be longitudinally flush with the fingers or be set back from the ends of the fingers, or project beyond the ends of the fingers both in the longitudinal and transverse directions.

Structure (vi): as shown in fig. 2(f), the n load block sub-blocks are arranged obliquely or in a curve, and the n load block sub-blocks cover the finger tip area and are located within the finger tip range.

In this embodiment, the shape of the load blocks may be a triangle, a square, a rectangle, an ellipse, a circle, a trapezoid, or a polygon with more than four sides, preferably a rectangle, and the sizes of different load blocks may be completely the same, or the sizes of part of load blocks may be different, or the sizes of different load blocks may be completely different. The width of the load mass may be greater than the width of the finger, or the load mass may be located in the region of the finger tip. In this embodiment, the lateral direction refers to a direction perpendicular to the interdigital fingers, the longitudinal direction refers to a direction parallel to the interdigital fingers, the pad width refers to a dimension of the pad in the lateral direction, and the pad length refers to a dimension of the pad in the longitudinal direction.

In this embodiment, the material of the load block is a metal, a combination of metal materials, or a metal oxide. Preferably, the carrier material may be the same metal material as the finger metal, i.e., titanium, chromium, copper, silver, aluminum, platinum, tungsten, or the like or combinations thereof, or alumina, Ta₂O₅And the like.

In the present embodiment, the length of the load block at each finger tip is 0.2 × lmabda to 1 × lambda, and when there are a plurality of load block sub-blocks, that is, the total length of the plurality of load block sub-blocks is 0.2 × lmabda to 1 × lambda, where lmabda is the wavelength of the surface acoustic wave.

In this embodiment, a load layer is also provided in an adjacent finger strip body region corresponding to the finger strip end position on the interdigital transducer, the load layer includes a plurality of load blocks, the load block may be one or a plurality of sub-blocks, and the load block in the specific finger strip body region may adopt the same technology as the load block in the finger strip end region, which is not described herein again.

In another preferred real-time mode of the invention, the reflecting grating of the temperature compensation surface acoustic wave device is also provided with a load block, the load block is positioned at the position where the metal finger of the reflecting grating corresponds to the end of the transducer finger, and the load block on the reflecting grating is made of metal. The number, shape, size and material of the load blocks on the specific reflection grating can all adopt the same technical scheme as the load blocks at the end of the interdigital transducer finger strip, and are not described herein again.

In another preferred embodiment of the present invention, the load blocks are connected between the metal finger gaps of the reflective grating of the temperature compensated saw device, the load blocks are made of metal, and the number of the load blocks between the reflective grating finger gaps is gradually reduced from the edge to the direction of the transducer. The load blocks connect the reflecting grids to form an arc reflecting surface or a chamfer reflecting surface.

The invention has flexible design and convenient process manufacturing, and reduces the requirement on the process manufacturing precision. Because the transverse mold has a similar propagation pattern to the main mold, reflections and standing waves form when regions of acoustic impedance discontinuity are encountered along the length of the fingers. It is possible to form a plurality of transverse modes within a pass band in one transducer. The present invention blocks the lateral mode generation by weighting in the end regions of the acoustic aperture, such as the end of a finger or a finger prosthesis. The invention reduces the propagation speed of surface acoustic waves in the end area of the finger strip and can well inhibit clutter in a transverse mode. The structure can also improve the electrical performance index of the TC-SAW, the Q value of the quality factor and the like.

The invention also provides a preparation method of the temperature compensation surface acoustic wave device, which comprises the following steps:

s1, preparing the piezoelectric base material 1;

s2, photoetching the surface of the piezoelectric substrate material, and preparing a load block 3 on the surface of the piezoelectric substrate material;

s3, photoetching, preparing an interdigital transducer and a reflecting grating, and forming a finger strip metal electrode 2;

s4, preparing a temperature compensation layer 4 with a positive temperature coefficient on the upper end face of the interdigital transducer;

s5, a passivation layer 5 is prepared on the temperature compensation layer.

The load block is positioned in the area corresponding to the end of the interdigital transducer, and/or positioned in the area of the adjacent interdigital transducer body corresponding to the position of the end of the interdigital transducer, and/or positioned at the position of the reflecting grating metal finger corresponding to the end of the interdigital transducer, and/or positioned between the metal fingers of the reflecting grating and connected with the adjacent reflecting grating metal finger.

In a preferred embodiment of the present invention, the specific preparation process is as follows:

the suitable piezoelectric material substrate is selected according to design requirements, and may be a material such as LiTaO3 (lithium tantalate), LiNbO3 (lithium niobate), quartz, and the like, which are cut in various shapes, as shown in fig. 3.

As shown in fig. 4, the surface of the piezoelectric substrate is uniformly coated with photoresist to protect the surface from contamination.

As shown in fig. 5, a plurality of layers of photoresist are uniformly coated on the surface of a piezoelectric material substrate, and then the photoresist is subjected to exposure, development, baking and other processes, so that the side surface of the photoresist is in an inverted trapezoid shape, and then a loading block for suppressing the transverse wave mode is deposited on the surface of the photoresist by means of electron beam evaporation, magnetron sputtering and other methods.

As shown in fig. 6, a wet stripping process is used to remove the photoresist and the metal on the photoresist, and the metal block of the loading layer is retained, thereby forming an isolated metal block grown at the end position of the finger, as shown in fig. 7 (a); alternatively, the load blocks are prepared on the interdigital transducers at the regions of the adjacent finger strip bodies corresponding to the positions of the finger strip ends, as shown in fig. 7 (b). As shown in fig. 7(a) and 7(b), the load blocks may be prepared at positions where the reflective grating metal fingers correspond to the ends of the transducer fingers.

In order to improve the Q value, a plurality of metal blocks can also be weighted and grown on the reflecting grating according to a certain rule in the gap of the reflecting grating, and the metal blocks are positioned among the metal fingers of the reflecting grating and are connected with the adjacent metal fingers of the reflecting grating. FIG. 8(a) shows an embodiment in which load blocks are located between metal fingers of a partial edge reflective grating and connected to adjacent reflective grating metal fingers; fig. 8(b) shows another embodiment, in which the load blocks are located between the metal fingers of all the reflective gratings and connected to the adjacent metal fingers of the reflective gratings.

Performing processes such as glue spreading, exposure, development, metal deposition, wet stripping and the like on the basis of the structure shown in fig. 6 to form the interdigital finger, as shown in fig. 9 and fig. 10, where fig. 9(a) is a schematic diagram of a structure in which the interdigital finger and the reflective gate are formed on the structure shown in fig. 7(a), fig. 9(b) is a schematic diagram of a structure in which the interdigital finger and the reflective gate are formed on the structure shown in fig. 7(b), fig. 10(a) is a schematic diagram of a structure in which the interdigital finger and the reflective gate are formed on the structure shown in fig. 8(a), and fig. 10(b) is a schematic diagram of a structure in which the interdigital finger and the reflective gate are formed on the structure shown in fig. 8 (b).

The width of the loading layer can also be smaller than the width of the finger, as shown in fig. 11, in this embodiment, fig. 11(a) is a schematic diagram of preparing the loading block at the finger tip position and on the reflective grating, and fig. 11(b) is a schematic diagram of preparing the loading block at the finger tip position, the adjacent finger body region corresponding to the finger tip position, and on the reflective grating.

As shown in fig. 12, a layer of temperature compensation material with positive temperature coefficient, such as silicon dioxide, germanium dioxide, silicon oxyfluoride, etc., is grown on the upper end surface of the metal by PVD (Physical Vapor Deposition) magnetron sputtering or electron beam evaporation. The thickness is controlled to be 500-2000 nm.

As shown in fig. 13, the temperature compensation layer is planarized while reaching a target thickness of the temperature compensation layer using a CMP (Chemical Mechanical Planarization) process.

As shown in fig. 14, a passivation layer is further grown on the temperature compensation layer of fig. 13 by using PECVD (Plasma Enhanced Chemical Vapor Deposition). So that the metal surface is not easily oxidized and the protection temperature compensation layer is not easily affected by moisture in the air. The passivation layer may be a material such as silicon nitride.

In this embodiment, the finger tips interface with the load mass and do not cover (as shown in fig. 15), partially cover (as shown in fig. 16) or fully cover the load mass (as shown in fig. 17).

In another embodiment of the present invention, step S2 may be replaced with: and photoetching the surface of the piezoelectric substrate material, etching the piezoelectric substrate to form a groove, and filling a load layer material in the groove to form a load block, preferably filling metal.

Fig. 18 and 19 are examples of simulation results of resonators fabricated according to the inventive structure. To show clarity, each curve is shifted by 5dB on the y-axis. When the loading layer width is fixed at 0.3 wavelength (lambda), the loading layer length varies from 0.3 wavelength to the real part and amplitude of the admittance at 0.6 wavelength. It can be seen from the figure that there is an optimum value of the load configuration parameter to optimise the resonator performance. When the load length is too small, L is 0.3 lambda or 0.4 lambda, the suppression of transverse mode is incomplete, and more parasitic peaks exist in the admittance amplitude and real part curves; when the load length is larger, L is 0.6 × lmabda, although the transverse mode parasitics are inhibited, the main mode in the IDT is seriously affected, a splitting peak is obviously generated at a resonance peak in an admittance curve, and the Q value is obviously reduced. The best suppression of the transverse mode of TC-SAW is obtained only when the load length takes the optimum value, L0.5 lambda, the amplitude value and the curve of the real part of the admittance are smoother, and at the same time a higher Q value is obtained.

Based on the move-up analysis, the present invention employs various embodiments in order to prevent lateral parasitic modes from affecting the dominant mode in the IDT. The method has the characteristics of good transverse mode inhibition effect, high Q value of the manufactured resonator, flexible design, convenience in process manufacturing and the like.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A preparation method of a temperature compensation surface acoustic wave device is characterized by comprising the following steps:

s1, preparing a piezoelectric substrate material;

and S5, preparing a passivation layer on the temperature compensation layer.

2. The method of claim 1, wherein the step S2 can be replaced with: and photoetching the surface of the piezoelectric substrate material, etching the piezoelectric substrate to form a groove, and forming a load block in the groove.

3. The method of claim 1 or 2, wherein the load block is located in a region corresponding to an end of an interdigital transducer finger, and/or in a region of an adjacent interdigital transducer body corresponding to a position of the finger end, and/or in a position of the reflective grating metal finger corresponding to the transducer finger end, and/or between the metal fingers of the reflective grating and connected to the adjacent reflective grating metal finger.

4. The method according to claim 3, wherein the metal fingers of the reflective grating of the temperature compensated SAW device are connected with load blocks, the load blocks are made of metal, and the number of the load blocks on the reflective grating fingers is gradually reduced from the edge to the direction of the transducer;

the different load blocks are the same size, are not identical or are not identical.

5. The method of claim 4, wherein the load block connects the reflective gratings to form an arc-shaped reflective surface or a corner-cut reflective surface.

6. A temperature compensated surface acoustic wave device, comprising:

a piezoelectric substrate;

the load layer is positioned on the upper surface layer of the piezoelectric substrate or extends a certain distance from the upper surface layer of the piezoelectric substrate to the interior of the piezoelectric substrate, the load layer comprises a plurality of load blocks, and each load block is positioned in a region corresponding to the end of a finger of the interdigital transducer;

the end heads of the fingers of the interdigital transducer are connected with the load block and are not covered, and the load block is partially covered or fully covered;

a temperature compensation layer located over the interdigital transducer; and

a passivation layer over the temperature compensation layer.

7. The temperature-compensated surface acoustic wave device of claim 6, wherein the interdigital transducer is also provided with a load layer in an area of the body of the adjacent finger corresponding to the position of the tip of the finger.

8. The temperature-compensated surface acoustic wave device of claim 6 or 7, wherein the material of the load mass is a metal, or a combination of metallic materials, or a metal oxide.

9. The temperature-compensated surface acoustic wave device of claim 6 or 7, wherein the load mass has a width greater than a width of the fingers or is located in a region of the ends of the fingers.

10. The temperature-compensated surface acoustic wave device of claim 6 or 7, wherein the loading mass length of each finger tip is 0.2-1 lambda, the lambda being the wavelength of the surface acoustic wave.

11. The temperature-compensated surface acoustic wave device of claim 6, wherein the temperature compensation layer has a thickness of 500nm to 2000 nm.

12. The temperature-compensated surface acoustic wave device of claim 6, wherein a load block is also disposed on the reflective grating of the temperature-compensated surface acoustic wave device, the load block being located at a position where the metal fingers of the reflective grating correspond to the ends of the transducer fingers, the load block being made of metal.

13. The temperature-compensated surface acoustic wave device of claim 6, wherein load blocks are connected between the metal finger spaces of the reflective grating of the temperature-compensated surface acoustic wave device, the load blocks are made of metal, and the number of the load blocks between the reflective grating finger spaces is gradually reduced from the edge to the direction of the transducer;

14. The temperature-compensated surface acoustic wave device of claim 13, wherein the load block connects the reflecting gratings to form an arc reflecting surface or a chamfer reflecting surface.

15. The temperature-compensated surface acoustic wave device according to claim 6 or 7, wherein the shape of the loading block is a triangle, a square, or a rectangle, or an ellipse, or a circle, or a trapezoid, or a polygon having more than four sides;

16. A temperature compensated surface acoustic wave device according to claim 6 or 7, wherein the number of loading blocks per finger tip is one, or a plurality of blocks arranged laterally, or a plurality of blocks arranged longitudinally, or a plurality of blocks arranged in a curved shape.