Surface elastic wave device and method for manufacturing the same

Abstract

An elastic surface wave device includes an IDT electrode, wherein the IDT electrode includes two comb-shaped electrodes arranged opposite to each other, the comb-shaped electrode has a bus bar, a plurality of electrode fingers extending from a corresponding bus bar to another bus bar and arranged in an interlaced manner, and a plurality of additional parts, wherein the additional parts are respectively superimposed on the front end and the rear end of the electrode fingers distributed along the extension direction thereof. The width of the additional part in the propagation direction of the elastic surface wave is the same as the width of the electrode finger provided with the additional part, and the position of the additional part in the propagation direction of the elastic surface wave is the same as the position of the electrode finger, thereby effectively suppressing the noise of the lateral vibration mode. A method for manufacturing an elastic surface wave device, wherein the additional part is formed by setting a groove-shaped stripping portion of the photoresist of the electrode finger, thereby eliminating the need to use a highly accurate and expensive exposure machine, thereby having an advantage in manufacturing cost.

Description

Technical Field

[0001] The present invention relates to a surface acoustic wave device formed by arranging an IDT electrode on a piezoelectric substrate, and a method for manufacturing the same. Background Art

[0002] A surface elastic wave device is an electronic device in which a pair of IDT electrodes with opposite polarities are provided on a piezoelectric substrate, and at least one of the IDT electrodes has a comb-shaped morphology. In order to suppress frequency fluctuations caused by temperature changes, the surface elastic wave device usually covers the surface of the piezoelectric substrate forming the IDT electrode with a protective layer such as silicon dioxide as the main component. By providing the protective layer, the frequency temperature coefficient of the frequency characteristics of the surface acoustic wave (SAW) propagating on the surface of the piezoelectric substrate will be opposite to the frequency temperature coefficient of the protective layer, so the influence of temperature fluctuations on the frequency characteristics can be suppressed. The surface elastic wave device with the above-mentioned structure is called a temperature-compensated surface elastic wave device. A surface elastic wave device is a device that generates vibrations of expected characteristics on a piezoelectric substrate through an IDT electrode, but the influence of unexpected lateral vibration modes on the characteristics is a problem to be solved. Generally speaking, by changing the surface morphology of the IDT electrode, the occurrence frequency of the lateral vibration mode and the noise (spurious) intensity of the lateral vibration mode can be adjusted. However, this method often fails to achieve the expected effect. The reason is that in order to achieve the desired frequency characteristics, the shape of the IDT electrode is often limited. If the shape of the electrode is changed in order to adopt the above method, the frequency characteristics tend to be deteriorated.

[0003] The piston structure is a conventional means for preventing noise in the lateral vibration mode and reducing characteristic degradation.

[0004] For example, patent document 1 (Japanese Patent No. 5503020) and patent document 2 (Japanese Patent No. 5221616) disclose piston structures. Electrode fingers of the piston structure are provided with components that increase width or weight at the front end and the rear end of the electrode fingers. Fig.18 and Fig.19 The electrode pattern shown is an example of an electrode finger structure using a piston structure. Fig.18 and Fig.19 The surface acoustic wave device shown in the figure includes an IDT electrode 51 formed on a piezoelectric substrate 50, and the IDT electrode 51 includes a comb electrode 52 and a comb electrode 53 arranged opposite to each other. The comb electrode 52 and the comb electrode 53 respectively have a bus bar 52a and a bus bar 53a, and a plurality of electrode fingers 52b and electrode fingers 53b extending from the corresponding bus bar to the other bus bar.

[0005] Each electrode finger 52b of the comb-shaped electrode 52 is further provided with an additional portion 52c and an additional portion 52d for increasing weight at the front end and the rear end along the extension direction thereof. Each electrode finger 53b of the comb-shaped electrode 53 is also provided with an additional portion 53c and an additional portion 53d at the front end and the rear end along the extension direction thereof. The additional portion 52c (53c) at the front end of one comb-shaped electrode 52 (53) and the additional portion 53d (52d) at the rear end of the other comb-shaped electrode 53 (52) are arranged at intervals along the propagation direction of the surface acoustic wave, that is, they are arranged along the arrangement direction of the electrode fingers 52b and the electrode fingers 53b indicated by the arrow X.

[0006] In the region 54 defined by the additional portions 52c and 52d, and the additional portions 53c and 53d, the acoustic velocity is slower than the acoustic velocity in the region 55 where the electrode fingers 52b and 53b are staggered. By setting the electrode finger structure, the fundamental mode wave can be confined to the region 55 where the electrode fingers 52b and 53b are staggered, and unnecessary noise of high-order lateral vibration modes can be suppressed.

[0007] Fig. 20 for Fig.18 The enlarged view of the additional part structure shown in FIG. Fig. 20 As shown, the width t2 of the additional portion 52c and the additional portion 52d of the electrode finger 52b is narrower than the width t1 of the electrode finger 52b. Similarly, the width t2 of the additional portion 53c and the additional portion 53d of the electrode finger 53b is narrower than the width t1 of the electrode finger 53b.

[0008] For another existing surface elastic wave device, such as Fig.21 As shown, the width t3 of the additional portion 52e and the additional portion 52f on the electrode finger 52b is wider than the width t1 of the electrode finger 52b. Similarly, the width t3 of the additional portion 53e and the additional portion 53f on the electrode finger 53b is wider than the width t1 of the electrode finger 53b.

[0009] Figure 22 to Figure 29 Description Fig. 20 The existing manufacturing process of the electrode structure. Fig. 22 As shown, first, a first photoresist layer 61 for forming an IDT electrode is provided on a cleaned wafer-shaped piezoelectric substrate 50. Fig.18 and 19 The IDT electrode shown in FIG. 1 is subjected to an exposure and development process for the first photoresist layer 61. Fig.23As shown in FIG. 1 , a stripping pattern 62 is formed in which a portion of the first photoresist layer 61 corresponding to the IDT electrode is stripped. The stripping pattern 62 has a groove-shaped stripping portion 62a for forming the electrode fingers 52b and 53b. Subsequently, by a process such as evaporation or sputtering, as shown in FIG. Fig.24 As shown in FIG. 1 , a first metal layer 63 for forming an IDT electrode 51 is provided. The first metal layer 63 is formed in the region of the groove-shaped peeling portion 62a to form the electrode fingers 52b and the electrode fingers 53b of the comb-shaped electrode. Thereafter, the first photoresist layer 61 and the first metal layer 63 thereon are removed together. Fig.25 As shown, the IDT electrode having the electrode finger 52b and the electrode finger 53b on the piezoelectric substrate 50 is exposed.

[0010] Then as Fig.26 As shown, the second photoresist layer 64 is fully coated on the piezoelectric substrate 50 where the IDT electrode 51 is formed. Fig. 20 The exposure patterns of the additional parts 52c and 52d, the additional parts 53c and 53d shown in FIG. 5 are irradiated onto the second photoresist layer 64. Then, through a development process, a photoresist layer 64 is formed as shown in FIG. Fig. 27 As shown, there is a peeling pattern having a window-shaped peeling portion 65a for setting the additional portion.

[0011] Then, if Fig.28 As shown in FIG. 1 , a second metal layer 66 is formed on the second photoresist layer 64 having the window-shaped peeling portion 65a by evaporation or sputtering. The second metal layer 66 forms an additional portion 52c (52d) on the electrode finger 52b in the area of ​​the window-shaped peeling portion 65a, or forms an additional portion 53d (53c) on the electrode finger 53b. Thereafter, the second photoresist layer 64 and the second metal layer 66 are removed together, and as shown in FIG. Fig.29 As shown, an IDT electrode having additional portions 52c and 52d, and additional portions 53c and 53d, which are located on electrode fingers 52b and 53b, respectively, is formed.

[0012] Fig.21 The formation of the additional portion 52e and the additional portion 52f, the additional portion 53e and the additional portion 53f is Fig. 27 In the steps shown, the width of the window-shaped peeling portion 65a is made larger than the widths of the electrode fingers 52b and 53b, and the rest of the manufacturing process is the same.

[0013] like Fig. 20 As shown in FIG. 1 , the width t2 of the additional portion 52c and the additional portion 52d, and the width t2 of the additional portion 53c and the additional portion 53d are narrower than the width t1 of the electrode finger 52b and the electrode finger 53b for the following reason. Fig. 27When the window-shaped peeling portion 65a is formed, in order to reserve the inevitable deviation between the position of the peeling pattern and the predetermined position. Fig.30 As shown in the figure, the position of the window-shaped peeling portion 65a is designed to form an additional portion 52c1 at the leftmost position on the electrode finger 52b, or to form an additional portion 52c2 at the rightmost position on the electrode finger 52b, so that the additional portion can be completely located within the width t1 range of the electrode finger 52b.

[0014] like Fig.21 As shown, the width t3 of the additional portion 52e and the additional portion 52f, and the width t3 of the additional portion 53e and 53f are wider than the width t1 of the electrode finger 52b and the electrode finger 53b for the same reason, that is, to reserve Fig. 27 The deviation between the position of the stripping pattern 65 of the second photoresist layer 64 and the predetermined position. Fig.31 As shown in the figure, the window-shaped peeling portion 65a is designed to form an additional portion 52e1 on the leftmost side of the electrode finger, or an additional portion 52e2 on the rightmost side of the electrode finger. In either case, the additional portion can completely cover the electrode finger 52b.

[0015] As mentioned above, in the existing surface acoustic wave components, there are problems with process position accuracy, such as Fig. 20 As shown in FIG. 1 , the width t2 of the additional portion 52c and the additional portion 52d, and the width t2 of the additional portion 53c and the additional portion 53d are designed to be narrower than the width t1 of the electrode finger 52b and the electrode finger 53b. Fig.21 As shown in FIG. 1 , the width t3 of the additional portion 52e and the additional portion 52f, and the width t3 of the additional portion 53e and the additional portion 53f are designed to be wider than the width t1 of the electrode finger 52b and the electrode finger 53b. Fig.30 or Fig.31 As shown in FIG. 1 , the propagation direction of the surface acoustic wave is misaligned between the electrode finger 52 b and the additional portion of the electrode finger 53 b. The misalignment is not conducive to suppressing noise in the lateral vibration mode, and deteriorates the characteristics. Summary of the invention

[0016] In view of the above problems, an object of the present invention is to provide an elastic surface wave device including an electrode structure capable of suppressing lateral vibration mode noise, and a method for manufacturing the same.

[0017] An embodiment of the elastic surface wave device of the present invention includes a piezoelectric substrate and an IDT electrode formed on the piezoelectric substrate, the IDT electrode includes two comb-shaped electrodes arranged opposite to each other, the comb-shaped electrode has a bus bar, a plurality of electrode fingers extending from a corresponding bus bar to another bus bar and arranged in an interlaced manner, and a plurality of additional parts, the additional parts are respectively superimposed on the front end portion and the tail end portion distributed along the extension direction of the electrode finger, the width of the additional part along the propagation direction of the elastic surface wave is the same as the width of the electrode finger provided with the additional part, and the position of the additional part along the propagation direction of the elastic surface wave is the same as the position of the electrode finger.

[0018] Therefore, by making the width of the additional portion provided on the electrode finger uniform and matching the position along the width direction, the acoustic velocity in the region where the additional portion is formed is made uniform, thereby making it possible to obtain uniform noise suppression characteristics in the lateral vibration mode of the surface acoustic wave device and obtain good frequency characteristics.

[0019] In the surface acoustic wave device of the present invention, as a specific implementation of the above-mentioned aspect, the IDT electrode is formed by lithography technology, and the additional portion is superimposed on the electrode finger by a photoresist stripping pattern used to form the electrode finger.

[0020] Therefore, in the specific implementation, since the additional portion utilizes the photoresist stripping pattern of the photoresist layer forming the electrode finger, the width of the additional portion provided on the electrode finger can be the same as that of the electrode finger, and the position of the additional portion along the width direction can also be the same as that of the electrode finger. Thus, the sound velocity in the area where the additional portion is formed can be the same. Therefore, the noise suppression characteristics of the lateral vibration mode of the acoustic surface wave device can be the same, and good frequency characteristics can be obtained.

[0021] In the surface acoustic wave device of the present invention, the material of the additional part includes any one of Au, Cu, Ag, Pt, Pd, W, Ta, Mo or its oxide.

[0022] An embodiment of the method for manufacturing an elastic surface wave device of the present invention comprises the following steps: coating a first photoresist layer on a piezoelectric substrate; forming a peeling pattern having a peeling portion corresponding to the shape of an IDT electrode on the first photoresist layer through an exposure and development process; forming a first metal layer for setting the IDT electrode on the piezoelectric substrate corresponding to the peeling portion of the peeling pattern and on the first photoresist layer, wherein the IDT electrode comprises a pair of comb-shaped electrodes, each of which has a bus bar and a plurality of electrode fingers extending from a corresponding bus bar to another bus bar and arranged in an interlaced manner; coating a second photoresist layer on the first metal layer; and forming a peeling pattern on the first photoresist layer through an exposure and development process. The light and development process forms two groove-shaped stripping portions on the second photoresist layer for setting the additional portion and intersecting with the electrode fingers of the comb-shaped electrode; forms a second metal layer for setting the additional portion on the second photoresist layer forming the groove-shaped stripping portions, and the second metal layer forms the additional portion on the front end portion and the tail end portion of the electrode finger distributed along the extension direction thereof through the groove-shaped stripping portions; and removes the first photoresist layer, the second photoresist layer, and the first metal layer and the second metal layer on the first photoresist layer and the second photoresist layer, so that the IDT electrode forming the additional portion in the aforementioned groove-shaped stripping portions is exposed.

[0023] The manufacturing method is to set a stripping pattern for forming a comb-shaped electrode on the first photoresist layer, and after forming the first metal layer according to the stripping pattern, retain the stripping pattern of the first photoresist layer, and use the remaining stripping pattern for forming the electrode finger to form the additional part. In other words, the method is to open a slit-shaped stripping pattern for forming the additional part on the second photoresist layer stacked on the first photoresist layer, and form a second metal layer for setting the additional part on the stripping pattern, and then, the first photoresist layer and the second photoresist layer together with the metal above are stripped to expose the electrode finger with the bus bar and the additional part. Therefore, the stripping pattern for the electrode finger formed on the first photoresist layer can be used intact to set the additional part. Therefore, the width of the additional part can be the same as the width of the electrode finger forming the additional part, and the position of the additional part and the electrode finger in the direction of propagation of the surface acoustic wave can be the same. Thereby, a surface acoustic wave device with good noise suppression characteristics of the lateral vibration mode can be provided.

[0024] Furthermore, even if an exposure device commonly used for manufacturing surface acoustic wave devices is used for the exposure device used in the lithography technology, a surface acoustic wave device having the above-mentioned good characteristics can be obtained. Therefore, there is no need to use an expensive exposure device having a short-wavelength exposure light source, which has an advantage in production cost.

[0025] In the manufacturing method of the elastic surface wave device of the present invention, the first photoresist layer comprises a lower photoresist layer and an upper photoresist layer stacked up and down, and the lower photoresist layer comprises a material having the property of being soluble in the developer of the upper photoresist layer.

[0026] In the manufacturing method of the elastic surface wave device of the present invention, after forming the first metal layer and before coating the second photoresist layer on the first metal layer, the first photoresist layer is not removed.

[0027] In the method for manufacturing an elastic surface wave device of the present invention, the second photoresist layer is made of a material with different properties from the first photoresist layer, and the different properties refer to different developers used in combination with the first photoresist layer and the second photoresist layer.

[0028] The manufacturing method of the elastic surface wave device of the present invention forms two groove-shaped stripping parts on the second photoresist layer through exposure and development processes, which are used to set the additional parts and intersect with the electrode fingers of the comb electrode. A developer that cannot remove the first photoresist layer but can remove the exposed area or the unexposed area of ​​the second photoresist layer is used.

[0029] Another embodiment of the method for manufacturing an elastic surface wave device of the present invention comprises the following steps: coating a first photoresist layer on a piezoelectric substrate; forming a stripping pattern having a stripping portion corresponding to the shape of an IDT electrode on the first photoresist layer through an exposure and development process; forming a first metal layer for setting the IDT electrode on the piezoelectric substrate corresponding to the stripping portion of the stripping pattern and on the first photoresist layer, wherein the IDT electrode comprises a pair of comb-shaped electrodes, each of which has a bus bar and a plurality of electrode fingers extending from one of the bus bars to the other bus bar and arranged in an interlaced manner; forming a second metal layer for setting an additional portion on the first metal layer formed in the stripping pattern and the first photoresist layer; A second photoresist layer is coated on the piezoelectric substrate on which the first photoresist layer, the first metal layer, and the second metal layer are formed; two photoresist layer residues for setting the additional portion and intersecting with the electrode fingers of the comb-shaped electrode are formed on the second photoresist layer through exposure and development processes; the second metal in the area outside the two photoresist layer residues is removed through dry etching, while the additional portion is retained, which is respectively overlapped on the front end portion and the tail end portion of the electrode finger distributed along the extension direction thereof; and the first photoresist layer, the second photoresist layer, and the first metal layer and the second metal layer on the first photoresist layer and the second photoresist layer are removed, so that the IDT electrode forming the additional portion in the aforementioned photoresist layer residue is exposed.

[0030] The manufacturing method provides a stripping pattern for forming a comb-shaped electrode on a first photoresist layer, and after forming a first metal layer according to the stripping pattern, the stripping pattern of the first photoresist layer is retained, and a second metal layer for forming the additional part is stacked on the first metal layer using the remaining stripping pattern for forming electrode fingers. Then, in order to stack the second photoresist layer on the first photoresist layer and remove the area other than the area for forming the additional part in the second metal layer, two columns of photoresist residues common to the comb-shaped electrodes arranged opposite to each other are retained, and the second photoresist layer is removed. Then, unnecessary parts of the second metal layer are removed by dry etching. Therefore, the stripping pattern for the electrode fingers formed on the first photoresist layer can be used intact to set the additional part. In this way, the width of the additional part can be the same as the width of the electrode fingers forming the additional part, and the positions of the additional part and the electrode fingers in the direction of propagation of the surface acoustic wave can be the same. Therefore, a surface acoustic wave device having good noise suppression characteristics in the lateral vibration mode can be provided. Furthermore, even if an exposure device commonly used for manufacturing surface acoustic wave devices is used for the exposure device used in the lithography technology, a surface acoustic wave device having the above-mentioned good characteristics can be obtained. Therefore, there is no need to use an expensive exposure device having a short-wavelength exposure light source, which has an advantage in production cost.

[0031] In the manufacturing method of the elastic surface wave device of the present invention, the second photoresist layer and the first photoresist layer are made of materials with different characteristics. In the process of forming the residual part of the photoresist layer through exposure and development processes, a developer is used that cannot remove the first photoresist layer but can remove the exposed area or the unexposed area of ​​the second photoresist layer.

[0032] The beneficial effect of the present invention is that the surface acoustic wave device can make the sound velocity of the additional portion region consistent by making the width of the additional portion provided on the electrode finger the same as the width of the electrode finger and matching the position of the additional portion in the width direction with the electrode finger. Thus, a surface acoustic wave device having good characteristics of suppressing lateral vibration modal noise can be obtained.

[0033] In the manufacturing method of the surface elastic wave device, after forming the first photoresist layer, forming the electrode pattern for setting the electrode finger, and forming the first metal layer for setting the electrode finger for the electrode pattern, and before removing the first photoresist layer, a second metal layer for setting the additional part superimposed on the electrode finger is formed. Thus, the width of the additional part set on the electrode finger will be the same as the width of the electrode finger, and the position of the additional part along the width direction will also match the electrode finger, and an elastic surface wave device with good characteristics of suppressing lateral vibration mode noise can be obtained.

[0034] In addition, since there is no need to use an expensive exposure machine having a short wavelength exposure light source and high accuracy, there is an advantage in manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Other features and effects of the present invention will be clearly presented in the embodiments with reference to the accompanying drawings, in which:

[0036] Figure 1 is a cross-sectional view of an embodiment of an elastic surface wave device of the present invention;

[0037] Figure 2 yes Figure 1 A top view of an electrode pattern of an IDT electrode of a surface acoustic wave device;

[0038] Figure 3 yes Figure 2 Section along EE;

[0039] Figure 4 yes Figure 2 Section along FF;

[0040] Figure 5 In order to form Figure 2 IDT electrode, a cross-sectional view of step 1 of the first embodiment of the manufacturing method of the present invention;

[0041] Figure 6 is a cross-sectional view of step 2 of the first embodiment of the manufacturing method of the present invention;

[0042] Figure 7 is a cross-sectional view of step 3 of the first embodiment of the manufacturing method of the present invention;

[0043] Figure 8 is a cross-sectional view of step 4 of the first embodiment of the manufacturing method of the present invention;

[0044] Fig. 9 is a top view of step 5 of the first embodiment of the manufacturing method of the present invention;

[0045] Fig.10 yes Fig. 9 Section along GG;

[0046] Fig.11 is a top view of step 6 of the first embodiment of the manufacturing method of the present invention;

[0047] Fig.12 In the second embodiment of the manufacturing method of the present invention, Figure 7 A cross-sectional view of the fourth step after the step;

[0048] Fig.13 is a cross-sectional view of step 5 of the second embodiment of the manufacturing method of the present invention;

[0049] Fig.14 is a top view of step 6 of the second embodiment of the manufacturing method of the present invention;

[0050] Fig.15 yes Fig.14 Section along HH;

[0051] Fig.16 is a cross-sectional view of step 7 of the second embodiment of the manufacturing method of the present invention;

[0052] Fig.17 is a cross-sectional view of step 8 of the second embodiment of the manufacturing method of the present invention;

[0053] Fig.18 is a top view of an electrode pattern of a conventional elastic surface wave device;

[0054] Fig.19 yes Fig.18 Section along II;

[0055] Fig. 20 is a top view of an example of an electrode finger structure having an additional portion of a conventional surface acoustic wave device;

[0056] Fig.21 is a top view of another example of an electrode finger structure having an additional portion of a conventional surface acoustic wave device;

[0057] Fig. 22 is a cross-sectional view of the first step of a conventional method for manufacturing an elastic surface wave device;

[0058] Fig.23 is a cross-sectional view of the second step of the conventional method for manufacturing an elastic surface wave device;

[0059] Fig.24 is a cross-sectional view of the third step of the conventional method for manufacturing an elastic surface wave device;

[0060] Fig.25 is a cross-sectional view of the fourth step of the conventional method for manufacturing an elastic surface wave device;

[0061] Fig.26 is a cross-sectional view of the fifth step of the conventional method for manufacturing an elastic surface wave device;

[0062] Fig. 27 is a cross-sectional view of step 6 of a conventional method for manufacturing an elastic surface wave device;

[0063] Fig.28 is a cross-sectional view of the seventh step of the conventional method for manufacturing an elastic surface wave device;

[0064] Fig.29is a cross-sectional view of the eighth step of the conventional method for manufacturing an elastic surface wave device;

[0065] Fig.30 yes Fig. 20 An explanatory diagram of the problems of conventional surface acoustic wave devices; and

[0066] Fig.31 yes Fig.21 Illustration of the problems of existing surface acoustic wave devices. DETAILED DESCRIPTION

[0067] Figure 1 An embodiment of the surface acoustic wave device of the present invention is described. The surface acoustic wave device includes a piezoelectric substrate 1 and an IDT electrode 2 formed on the piezoelectric substrate 1. The IDT electrode 2 includes: Figure 2 The comb-shaped electrodes 3 and 4 are arranged opposite to each other. The comb-shaped electrodes 3 and 4 respectively have bus bars 3a and 4a, and a plurality of electrode fingers 3b and 4b connecting the bus bars 3a and 4a. The electrode fingers 3b and 4b are arranged alternately. The piezoelectric substrate 1 is also provided with wiring 5 and wiring 6 electrically connected to the IDT electrode 2.

[0068] like Figure 1 As shown, the IDT electrode 2 is provided with a first protective layer 7a covering the IDT electrode 2. A bump 8 for electrically connecting to a substrate with other circuits is provided above the first protective layer 7a. The wiring 5 on the piezoelectric substrate 1 is electrically connected to the bump 8 through a conductor layer 9. Another wiring 6 electrically connected to the comb-shaped electrode 4 is electrically connected to other circuits on the piezoelectric substrate 1. A second protective layer 7b for protecting the conductor layer 9 and the like is provided on the first protective layer 7a.

[0069] like Figure 2 and Figure 3 As shown, the electrode finger 3b and the electrode finger 4b extend from the bus bar 3a and the bus bar 4a to the opposite bus bar, respectively. An additional portion 3c is provided at the front end portion of the electrode finger 3b along the extension direction thereof, which is overlapped on the electrode finger 3b and increases the weight. In addition, at the rear end portion of the electrode finger 3b, that is, on the side close to the bus bar 3a, an additional portion 3d is provided, which is overlapped on the electrode finger 3b and is used to increase the weight. The additional portion 4c and the additional portion 4d are respectively provided at the front end portion and the rear end portion of the electrode finger 4b along the extension direction thereof, which are overlapped on the electrode finger 4b.

[0070] like Figure 2As shown in the figure, the arrangement direction of the additional portion 3c located at the front end of the electrode finger 3b and the additional portion 4d located at the rear end of the electrode finger 4b is the same as the propagation direction of the surface acoustic wave shown by the arrow X, thereby forming a region 10b with a relatively slow sound velocity. Furthermore, the arrangement direction of the additional portion 3d located at the rear end of the electrode finger 3b and the additional portion 4c located at the front end of the electrode finger 4b is the same as the propagation direction of the surface acoustic wave shown by the arrow X, thereby forming a region 10a with a relatively slow sound velocity. Between the region 10a and the region 10b is a region 11 where the electrode fingers are staggered.

[0071] like Figure 4 As shown in FIG. 1 , the width t4 of the additional portion 3d and the additional portion 4c along the propagation direction of the surface acoustic wave is the same as the width t5 of the electrode finger 3b and the electrode finger 4b provided with the additional portion (t4=t5). The width of the additional portion 3c and the additional portion 4d along the propagation direction of the surface acoustic wave is also t4 as the width of the additional portion 3d and the additional portion 4c. Figure 2 The positions of the additional parts 3c and 3d along the propagation direction of the SAW are the same as those of the electrode fingers 3b provided with the additional parts. The positions of the additional parts 4c and 4d along the propagation direction of the SAW are the same as those of the electrode fingers 4b provided with the additional parts.

[0072] In addition, although the width t4 of the additional portion 3c and the additional portion 3d is the same as the width t5 of the electrode finger 3b, when the electrode finger 3b, the additional portion 3c and the additional portion 3d are formed by film forming technology, the process error of the width cannot be avoided. Specifically, for example, for a resonator with a resonant frequency of 2GHz, the width t5 of the electrode finger 3b is, for example, 0.4 to 0.6μm. In this case, it is inevitable that there will be an error (t4-t5) of about ±0.03μm in the width due to the process. In the present invention, the degree of the error can be ignored. In addition, the position error of the electrode finger 3b, the additional portion 3c and the additional portion 3d along the width direction is about half of the aforementioned width difference ±0.015μm, and therefore can be ignored. The width and position relationship of the electrode finger 4b, the additional portion 4c and the additional portion 4d are the same. In addition, in this embodiment, although the widths of the electrode finger 3b and the electrode finger 4b are the same, in other embodiments of the present invention, the electrode finger 3b and the electrode finger 4b can also be designed to have different widths.

[0073] In this embodiment, the piezoelectric material used in the piezoelectric substrate 1 is lithium niobate (LiNbO 3 ), but in other embodiments, lithium tantalate (LiTaO 3 And, preferably, the material of the first protective layer 7a is silicon dioxide (SiO 2). The frequency temperature coefficients of lithium niobate and silicon dioxide are opposite to each other. Therefore, when lithium niobate is used for the piezoelectric substrate 1 and silicon dioxide is used for the first protective layer 7a, a temperature-compensated surface acoustic wave device having stable frequency characteristics relative to temperature changes can be obtained.

[0074] The material of the IDT electrode 2 is, for example but not limited to, Al, Au, Cu, Ni, Pt, Ti, Cr, Ag or their alloys, and other metals or their alloys may also be used. The material of the additional parts 3c, 3d, 4c, 4d is preferably a heavy metal or its oxide that can increase the weight, such as Au, Cu, Ag, Pt, Pd, W, Ta, Mo or their oxides.

[0075] The piezoelectric substrate 1 may also be disposed on a carrier substrate (not shown). The carrier substrate is made of a high-impedance semiconductor or insulating material, such as amorphous silicon or crystalline sapphire. The material of the carrier substrate is not limited to the above materials, and may also be other materials such as polycrystalline silicon, polycrystalline alumina, polycrystalline sapphire, etc. that can solve the problem to be solved by the present invention. In addition, an intermediate layer may also be disposed between the piezoelectric substrate 1 and the carrier substrate (not shown).

[0076] In the present embodiment, in the regions 10a and 10b on both sides of the region 11 where the electrode fingers 3b and the electrode fingers 4b are arranged in an interlaced manner, because the additional portions 3c, 3d, 4c and 4d are provided, the sound velocity of the regions is slower than the sound velocity of the region 11. Therefore, the fundamental mode wave can be locked in the region 11 where the electrode fingers 3b and the electrode fingers 4b are arranged in an interlaced manner, and the unnecessary high-frequency transverse mode can be suppressed.

[0077] In addition, since the width t5 of the electrode finger 3b (electrode finger 4b) is the same as the width t4 of the additional portion 3c and the additional portion 3d (additional portion 4c and additional portion 4d) respectively provided, and the positions of the additional portion 3c and the additional portion 3d (additional portion 4c and additional portion 4d) in the width direction are the same as those of the electrode finger 3b (electrode finger 4b), the acoustic velocities of the region 10a and the region 10b where the additional portion is formed can be made consistent. Thus, the acoustic surface wave device can unify the suppression characteristics of the lateral vibration mode noise and obtain good frequency characteristics.

[0078] then, Figures 5 to 11 Description Figures 1 to 4 The first embodiment of the method for manufacturing an elastic surface wave device having an electrode pattern shown in FIG. Figure 5 As shown, a first photoresist layer 12 for forming an IDT electrode 2 is disposed on a cleaned wafer-shaped piezoelectric substrate 1. The first photoresist layer may be a negative or positive Novolac photoresist, or other types of photoresists.

[0079] The first photoresist layer 12 of the first embodiment comprises a lower photoresist layer 12a and an upper photoresist layer 12b stacked one above the other. The first photoresist layer 12 has a double-layer structure for the following reasons: Figure 6 The lower photoresist layer 12a is made of a material that can be dissolved by the developer of the upper photoresist layer 12b.

[0080] For the first photoresist layer 12, Figure 2 As shown in FIG. 1 , the exposure pattern of the IDT electrode 2 is exposed and developed. Figure 6 As shown, a region corresponding to the IDT electrode 2 is removed to form a lift-off pattern 13 having a lift-off portion. In the lift-off pattern 13, a groove-shaped lift-off portion 13a corresponds to a region formed in the electrode finger 3b and the electrode finger 4b.

[0081] like Figure 7 As shown in FIG. 1 , a first metal layer 14 for setting the IDT electrode 2 is formed on the first photoresist layer 12 having the lift-off pattern 13 by evaporation or sputtering. The first metal layer 14 is formed at the bottom of the groove-shaped lift-off portion 13a of the lift-off pattern 13 to form the electrode finger 3b and the electrode finger 4b. Through the above process, a metal layer serving as the IDT electrode 2 is formed. In other words, Figure 2 The comb-shaped electrodes 3 and 4 including the wirings 5 ​​and 6 are shown.

[0082] In the existing manufacturing methods, Fig.25 As shown in FIG. 1 , after the IDT electrode 2 is formed, the first photoresist layer 61 is removed. However, in this embodiment, after the first metal layer 14 is formed, the first photoresist layer 12 is not removed. Figure 8 As shown, a second photoresist layer 15 is coated on the first photoresist layer 12 and the first metal layer 14 .

[0083] Although the second photoresist layer 15 can be made of the same material as the first photoresist layer 12, preferably, the second photoresist layer 15 is made of a material with different properties from the first photoresist layer 12. The reason is as follows: when the groove-shaped peeling portion 15a and the groove-shaped peeling portion 15b are subsequently formed, a portion of the first photoresist layer 12 may be removed and thinned, and the width of the groove-shaped peeling portion 13a may be expanded. Therefore, the first photoresist layer 12 may be made of, for example, an alkali-developable material, and the second photoresist layer 15 may be made of, for example, an organic solvent-developable material.

[0084] Then, if Fig. 9 and Fig.10As shown, through the exposure and development process, two groove-shaped peeling portions 15a and 15b extending along the arrangement direction of the electrode fingers 3b and the electrode fingers 4b are formed on the second photoresist layer 15. The groove-shaped peeling portions 15a and the groove-shaped peeling portions 15b intersect at each front end and tail end of the electrode fingers 3b and the electrode fingers 4b, respectively. In order to form the groove-shaped peeling portions 15a and the groove-shaped peeling portions 15b, a developer that cannot remove the first photoresist layer 12 but can remove the exposed area or the unexposed area of ​​the second photoresist layer 15 is used.

[0085] The position of the groove-shaped peeling portion 15a corresponds to Figure 2 The position of the region 10b shown in the figure is equivalent to the position of the region 10a. That is to say, the position of the groove-shaped peeling portion 15a is equivalent to the position of the additional portion 3c on the front end of the electrode finger 3b and the additional portion 4d on the rear end of the electrode finger 4b. Moreover, the position of the groove-shaped peeling portion 15b is equivalent to the position of the additional portion 3d on the rear end of the electrode finger 3b and the additional portion 4c on the front end of the electrode finger 4b. In the step of forming the groove-shaped peeling portion 15a and the groove-shaped peeling portion 15b, the first photoresist layer 12 is still retained, and the groove-shaped peeling portion 13a is also retained and exposed in the groove-shaped peeling portion 15a and the groove-shaped peeling portion 15b.

[0086] Then, if Fig.11 As shown, a second metal layer 16 for setting an additional portion is formed on the second photoresist layer 15 having the groove-shaped peeling portion 15a and the groove-shaped peeling portion 15b. The second metal layer 16 is formed in the region of the groove-shaped peeling portion 13a of the exposed first photoresist layer 12, and additional portions 3c (3d) and additional portions 4d (4c) are formed on the electrode fingers 3b and 4b in the groove-shaped peeling portion 13a, respectively.

[0087] Next, a developer capable of removing the first photoresist layer 12 and the second photoresist layer 15 is used to remove the first photoresist layer 12 and the second photoresist layer 15, and the first metal layer 14 and the second metal layer 16 thereon are removed simultaneously. Thus, the comb-shaped electrodes 3 and 4 including the wiring 5, the wiring 6, the additional portion 3c, the additional portion 3d, the additional portion 4c and the additional portion 4d are exposed. In other words, Figure 2 and Figure 4 As shown, busbars 3a and 4a, electrode fingers 3b and 4b, additional portions 3c and 3d on electrode fingers 3b, and additional portions 4c and 4d on electrode fingers 4b are all exposed.

[0088] As described above, the method for manufacturing the surface acoustic wave device of the first embodiment is to form a peeling pattern 13 having a peeling portion for setting an electrode finger on the first photoresist layer 12, then form a first metal layer 14 on the first photoresist layer 12 having the peeling pattern 13, and then form a second metal layer 16 for setting the additional portion 3c, 3d and the additional portion 4c, 4d on the electrode finger 3b and the electrode finger 4b before removing the first photoresist layer 12. Therefore, the width t4 of the additional portion 3c and the additional portion 3d set on the electrode finger 3b, and the additional portion 4c and the additional portion 4d set on the electrode finger 4b is the same as the width t5 of the electrode finger 3b and the electrode finger 4b. In addition, the positions of the additional portion 3c and the additional portion 3d, and the additional portion 4c and the additional portion 4d along the width direction are the same as those of the electrode finger 3b and the electrode finger 4b, respectively. Therefore, the acoustic velocities of the region 10a and the region 10b are made the same, and a surface acoustic wave device capable of effectively suppressing lateral vibration mode noise is obtained.

[0089] Moreover, for example, when the frequency of the elastic surface wave device is 2 GHz, in order to form the stripping pattern of the photoresist, the exposure device generally uses an i-line stepper. However, in this first embodiment, the position and width of the additional part and the width and position of the electrode finger can be aligned using a general exposure device. Therefore, there is no need to use an exposure machine such as an i-line stepper that has a short wavelength exposure light source and is highly accurate and expensive, and it can have an advantage in manufacturing cost. In addition, if a high-frequency fine electrode pattern is to be further produced, for example, a KrF excimer laser or an ArF excimer laser can be used as a light source. Therefore, there is no need to use an exposure machine that is highly accurate and expensive, and it has an advantage in manufacturing cost.

[0090] Next, a second embodiment of the method for manufacturing an acoustic surface wave device of the present invention is described. In this second embodiment, after forming the electrode fingers 3b and 4b, the electrode pattern of the photoresist layer is retained, and a metal layer for setting the additional part is formed by the stripping pattern, and then the unnecessary metal layer other than the additional part is removed by dry etching, and finally the additional part 3c, the additional part 3d, the additional part 4c, and the additional part 4d are formed.

[0091] The manufacturing method of the second embodiment is Figures 5 to 11 In the steps, Figures 5 to 7 The steps are the same as those of the first embodiment. In this second embodiment, Figure 7 As shown, after the IDT electrode is formed by the stripping pattern 13 of the first photoresist layer 12, as shown in FIG. Fig.12 As shown, a second metal layer 18 for setting the additional portion is formed on the IDT electrode 2 by evaporation or sputtering process. The second metal layer 18 is formed on the electrode fingers 3b and 4b in the groove-shaped peeling portion 13a of the first photoresist layer 12.

[0092] Then as Fig.13 As shown, a second photoresist layer 19 is coated on the second metal layer 18. The second photoresist layer 19 uses a material with different properties from the first photoresist layer 12. In other words, a developer that cannot remove the first photoresist layer 12 but can remove the exposed area or unexposed area of ​​the second photoresist layer 19 can be used.

[0093] Then, if Fig.14 and Fig.15 As shown, by exposing and developing the second photoresist layer 19, photoresist residues 19a and 19b are formed, which intersect the electrode fingers 3b and 4b of the comb-shaped electrodes 3 and 4 and have a bank-like appearance. In other words, the second photoresist layer 19 other than the photoresist residues 19a and 19b is removed. The position of the photoresist residue 19b corresponds to the additional portion 3c on the front end of the electrode finger 3b and the additional portion 4d on the rear end of the electrode finger 4b. In addition, the position of the photoresist residue 19a corresponds to the additional portion 3d on the rear end of the electrode finger 3b and the additional portion 4c on the front end of the electrode finger 4b. When removing the second photoresist layer 19, a developer that can remove the second photoresist layer 19 but cannot remove the first photoresist layer 12 is used.

[0094] Then, if Fig.16 As shown, the second metal layer 18 other than the photoresist residue portion 19a and the photoresist residue portion 19b is removed by dry etching. Thus, the additional portion 3c and the additional portion 3d located below the photoresist residue portion 19a and the photoresist residue portion 19b and located on the electrode finger 3b as the residue of the second metal layer 18 are retained. In addition, the additional portion 4c and the additional portion 4d as the residue of the second metal layer 18 on the electrode finger 4b are retained.

[0095] Then, the photoresist remaining portion 19a and the photoresist remaining portion 19b of the second photoresist layer 19 are removed. Figure 2 As shown, the comb-shaped electrodes 3 and 4 are exposed, and the additional portions 3c and 3d are provided on the electrode fingers 3b, and the additional portions 4c and 4d are provided on the electrode fingers 4b.

[0096] Thus, in the manufacturing method of the surface acoustic wave device of the second embodiment, the IDT electrode 2 having the additional portion 3c and the additional portion 3d, and the additional portion 4c and the additional portion 4d, respectively, on the electrode finger 3b and the electrode finger 4b is manufactured by means of the peeling pattern formed on the first photoresist layer 12. Therefore, the width t4 of the additional portion 3c and the additional portion 3d, and the width t4 of the additional portion 4c and the additional portion 4d, provided on the electrode finger 3b and the electrode finger 4b, will be the same as the width t5 of the electrode finger 3b and the electrode finger 4b. Furthermore, the positions of the additional portion 3c and the additional portion 3d, and the additional portion 4c and the additional portion 4d in their respective width directions will be matched with the positions of the electrode finger 3b and the electrode finger 4b in the width directions, respectively. Therefore, the acoustic velocities in the region 10a and the region 10b can be made consistent, and a surface acoustic wave device that can effectively suppress lateral vibration modal noise is obtained.

[0097] Furthermore, in the second embodiment, the exposure light source used to form the comb-shaped electrodes can be applied to the production of the additional portion, so there is no need to use a high-precision and expensive exposure machine, which has an advantage in production cost.

[0098] In the above embodiment, although the wiring 5 and the wiring 6 are provided on the IDT electrode 2, when the surface acoustic wave device is used as a resonator, reflectors may be provided on both sides of the IDT electrode 2. In the above case, the IDT electrode excluding the additional portion and the reflectors are formed simultaneously by the first metal layer, and then the additional portion is formed by the steps described in the above embodiment.

[0099] The above are merely embodiments of the present invention and should not be used to limit the scope of the present invention. That is, any simple equivalent changes and modifications made according to the claims and description of the present invention still fall within the scope of the present invention.

Claims

1. A method for manufacturing an elastic surface wave device, characterized in that: The method for manufacturing the surface acoustic wave device comprises the following steps: A first photoresist layer is coated on the piezoelectric substrate; the first photoresist layer comprises a lower photoresist layer and an upper photoresist layer stacked up and down, the lower photoresist layer comprises a material having a property of being soluble in a developer of the upper photoresist layer; a stripping pattern having a stripping portion corresponding to the shape of the IDT electrode is formed on the first photoresist layer through an exposure and development process; A first metal layer for setting the IDT electrode is formed on the piezoelectric substrate corresponding to the peeling portion of the peeling pattern and on the first photoresist layer, wherein the IDT electrode includes a pair of comb-shaped electrodes, each of which has a bus bar and a plurality of electrode fingers extending from one bus bar to another bus bar and arranged in an interlaced manner; forming a second metal layer for setting an additional portion on the first metal layer formed by the lift-off pattern and the first photoresist layer; coating a second photoresist layer on the piezoelectric substrate on which the first photoresist layer, the first metal layer, and the second metal layer are formed; Forming two photoresist layer residual portions on the second photoresist layer through an exposure and development process, the two residual portions are used to set the additional portions and intersect with the electrode fingers of the comb-shaped electrode; The second metal in the area other than the two photoresist layer residual parts is removed by dry etching, and the additional parts respectively overlapped on the front end part and the tail end part of the electrode finger distributed along the extension direction thereof are retained; and The first photoresist layer, the second photoresist layer, and the first metal layer and the second metal layer on the first photoresist layer and the second photoresist layer are removed, so that the IDT electrode forming the additional portion in the remaining portion of the photoresist layer is exposed.

2. The method for manufacturing a surface acoustic wave device according to claim 1, characterized in that: The second photoresist layer and the first photoresist layer are made of materials with different properties. In the process of forming the residual portion of the photoresist layer through exposure and development processes, a developer is used that cannot remove the first photoresist layer but can remove the exposed area or unexposed area of ​​the second photoresist layer.

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