JP2004186938A - Surface acoustic wave element, surface acoustic wave device, electronic circuit device, method of manufacturing the element, and method of manufacturing surface acoustic wave device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a surface acoustic device small-sized and thin by suppressing corrosion of interdigital electrodes due to a local battery effect. <P>SOLUTION: The surface acoustic wave device has a surface acoustic wave element 11 and packages 9 and 10. The surface acoustic wave element is provided with a piezoelectric single crystal substrate 1, an interdigital electrode 2 provided on one principal surface of the substrate 1, and a back electrode 3 provided on the other surface of the substrate 1. One principal surface 1a provided with the interdigital electrode 2A is made into a negatively charged surface of spontaneous polarization of the piezoelectric single crystal substrate. Packages 9 and 10 have sealing structure of covering the surface acoustic wave element 1 and of enabling water to pass through the packages. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface acoustic wave device, a surface acoustic wave device, a method of manufacturing a surface acoustic wave device, a method of manufacturing a surface acoustic wave device, and a surface acoustic wave device used as a frequency filter or a resonator mounted on a communication device such as a mobile phone and a keyless entry. And a method for producing the same.
[0002]
[Prior art]
FIG. 11 shows a sectional view of a conventional surface acoustic wave device. In FIG. 11, reference numeral 101 denotes a piezoelectric single crystal substrate. Reference numeral 102 denotes a comb-shaped electrode forming surface of the piezoelectric single crystal substrate 101. A comb-shaped electrode (not shown) for exciting a surface acoustic wave is provided on the comb-shaped electrode forming surface 102. Reference numeral 103 denotes a protruding electrode provided on the comb-shaped electrode forming surface 102. The projecting electrode 103 is electrically connected to a comb-shaped electrode (not shown). Reference numeral 104 denotes a ceramic package that houses the piezoelectric substrate 101. Reference numeral 105 denotes a lid part of the ceramic package 104. The cover 105 is made of metal or the like. Reference numeral 106 denotes an electrode provided on the lid 105. The electrode 106 inputs and outputs an electric signal to and from the outside. The electrode 106 is electrically connected to the protruding electrode 102.
[0003]
This surface acoustic wave device is used in mobile phones and the like. For electronic components including surface acoustic wave devices, it is necessary to ensure that characteristics do not deteriorate even in a high-temperature, high-humidity environment. In order to make such a guarantee, an electronic component is subjected to a standing test under a high-temperature and high-humidity test.
[0004]
In order to increase the durability against such a standing test, in the surface acoustic wave device, the lid 105 and the ceramic package 104 are hermetically sealed with a hermetic seal or the like. Thereby, moisture and the like can be completely shut off, and even if the above-described standing test is performed, corrosion of the electrode, particularly, corrosion of the comb-shaped electrode does not occur.
[0005]
FIG. 12 shows a portion around a comb-shaped electrode of the surface acoustic wave device. In this configuration, a piezoelectric single crystal substrate 111 of lithium tantalate or the like is provided, and a comb-shaped electrode 115 formed on the surface of the piezoelectric single crystal substrate 111 is provided. The comb electrode 115 has a three-layer structure. The comb electrode 115 includes a first layer 112, a second layer 113, and a third layer 114 from the side closer to the piezoelectric substrate 111. The first layer 112 and the third layer 14 are main electrodes that greatly contribute to transmission of an electric signal. The second layer is an intermediate layer for preventing Al alloy crystal grains from growing. The first layer 112 and the third layer 114, which are main electrodes, are made of an Al alloy. Here, Cu, Ti, Pd, Mg, Cr, Ni, and Ta are used as additive metals to Al. Further, unlike the Al alloy, the second layer 113, which is an intermediate layer, is mainly composed of a semiconductor and an insulator which are materials capable of suppressing corrosion caused by the local battery effect.
[0006]
By using the structure in FIG. 12, it is possible to reduce the corrosion deterioration of the comb-shaped electrode due to the local battery effect in the step of contact with moisture (dicing treatment or the like). (For example, see Patent Document 1)
[0007]
[Patent Document 1]
JP-A-11-163661 (full text)
[0008]
[Problems to be solved by the invention]
However, the conventional structure using the hermetic seal shown in FIG. 11 has problems in that miniaturization of the element is hindered and cost is increased. In addition, in order to prevent corrosion of the comb-shaped electrode during the process, it is necessary to avoid contact with water during the process or to perform a special operation even when the contact is made. For example, water used in dicing or the like requires precise pH adjustment so that corrosion does not occur. Therefore, there are restrictions such as complicated process management and restrictions on the chemical solution used, which leads to an increase in cost.
[0009]
In the configuration shown in FIG. 12, by providing the second layer 113, corrosion caused by the local battery effect can be suppressed. For this reason, the above-mentioned inconvenience during the process is avoided to some extent. However, there occurs a problem that the electrode finger resistance of the comb-shaped electrode 115 increases. The increase in the electrode finger resistance is, for example, a factor of deterioration of insertion loss when configuring a filter with a surface acoustic wave device, and a factor of decreasing a Q value when configuring a vibrator with a surface acoustic wave device.
[0010]
The first factor for increasing the electrode finger resistance is that the second layer 103 has a high resistivity. Here, the resistance of the comb-shaped electrode 115 can be reduced by reducing its weight. However, the weight of the comb-shaped electrode 115 is a factor that determines the performance of the elastic surface device, and it is difficult to freely change the weight because it is desired to reduce the resistance. For this reason, the weight of the comb-shaped electrode 115 must be subject to certain restrictions based on desired characteristics. For such a reason, by providing the second layer 103 made of a material having a high resistivity, the electrode finger resistance of the comb-shaped electrode 115 substantially increases.
[0011]
A second cause of the increase in the electrode finger resistance is a multi-layered comb electrode 115. The metal thin film has such a property that its resistance becomes larger than the bulk metal's original resistivity as it becomes thinner. On the other hand, by making the comb-shaped electrode 115 multilayer, the thickness of each of the layers 112 to 114 is reduced. Therefore, the overall resistance of the multi-layered comb-shaped electrode 115 increases as the thickness per layer decreases. This tendency exists unless each layer constituting the comb-shaped electrode 115 is formed of a metal epi-film which is difficult and expensive.
[0012]
A third cause of the increase in the electrode finger resistance is a limitation of the additive metal added to the alloy layers forming the first layer 112 and the third layer 114. In order to maintain the characteristics of the first layer 112 and the third layer 114, a metal which causes an increase in the resistivity of the alloy layer must be added, thereby increasing the electrode finger resistance.
[0013]
Further, the additive metal is also limited in order to suppress the local battery effect generated inside the first layer 112 and the third layer 114. This will be described below. Corrosion deterioration of the electrode layer caused by the local battery effect is caused not only between the second layer 103 and other layers (the first layer 112 and the third layer 114) but also between the first layer 112 and the third layer 114. It also occurs inside. Specifically, a local battery effect also occurs between Al, which is a main material of the first layer 112 and the third layer 114, and an additional metal added thereto. In order to suppress such a local battery effect occurring inside the layer, the additive metal has a standard electrode potential close to the main material (Al) of the layer or is smaller than the standard electrode potential of the main material (Al). A metal having a standard electrode potential is selected.
[0014]
Suitable metals for the above-mentioned additional metals in view of the standard electrode potential include Ti, Li, Mg and the like. However, both of these metals have the property of increasing the resistivity significantly with small additions. For example, in the case of Ti, the addition of 1% by weight causes the resistivity to increase more than twice.
[0015]
On the other hand, as a metal that does not significantly increase the resistivity of the first layer 112 and the third layer 114, Cu or the like can be given. However, a metal such as Cu has a characteristic that corrosion deterioration due to a local battery corrosion effect inside the first layer 112 and the third layer 114 is easily caused.
[0016]
The above is a major disadvantage of the multilayer electrode finger structure shown in FIG. The multi-layer electrode finger structure shown in FIG. 12 further has the following disadvantages. That is, in this electrode finger structure, it is difficult to control the thickness of the electrode finger, and thus it is difficult to adjust the frequency. This is because a multilayer film is formed, that is, the number of times of film formation increases. Further, the multilayer electrode finger structure of FIG. 12 has a disadvantage that the manufacturing process is complicated and the cost is increased by using a multilayer film.
[0017]
As described above, in the configuration of the conventional surface acoustic wave device, if a completely sealed structure is used, miniaturization and cost reduction are hindered. If the structure of the electrode finger is improved to increase the water resistance (corrosion resistance), In addition, there arises a problem that the resistivity of the comb-shaped electrode is increased. Therefore, it is desired to improve the water resistance (corrosion resistance) of the electrode finger without causing such inconvenience.
[0018]
[Means to solve the problem]
The surface acoustic wave device of the present invention includes a piezoelectric single crystal substrate, a comb-shaped electrode provided on one main surface of the piezoelectric single crystal substrate, and a back electrode provided on the other main surface of the piezoelectric single crystal substrate. The method is characterized in that the one main surface on which the comb-shaped electrodes are provided is a negative surface of spontaneous polarization of the piezoelectric single crystal substrate.
[0019]
A surface acoustic wave device according to the present invention includes a surface acoustic wave element and a package that houses the surface acoustic wave element, wherein the surface acoustic wave element includes a piezoelectric single crystal substrate and one of the piezoelectric single crystal substrates. A comb-shaped electrode provided on a surface of the piezoelectric single-crystal substrate, and a back electrode provided on the other main surface of the piezoelectric single-crystal substrate. There is a feature in making a surface.
[0020]
According to such a configuration of the surface acoustic wave element and the surface acoustic wave device of the present invention, the occurrence of the local battery effect between the comb-shaped electrode and the back electrode is suppressed, so that the electrode corrosion of the comb-shaped electrode is suppressed. .
[0021]
In the present invention, it is preferable that the package has a sealing structure that covers the surface acoustic wave element and allows water to flow inside and outside the package. Then, the size and the height can be reduced and the cost can be reduced. This means that if the electrode corrosion inhibiting effect of the present invention is exerted, it is possible to use a package having a sealing structure that covers the surface acoustic wave element and allows moisture to flow in and out of the package without any problem. That's why. Such a package brings the surface acoustic wave device to a reduction in size, height, and cost.
[0022]
The package preferably includes a wiring board on which the surface acoustic wave element is mounted, and a lid that covers the surface of the wiring board on which the surface acoustic wave element is arranged together with the surface acoustic wave element.
[0023]
Note that the present invention can be more suitably implemented in a surface acoustic wave device in which circuit elements are mixedly mounted on the wiring board. Then, the benefits of downsizing and cost reduction can be fully enjoyed.
[0024]
With the configuration of the present invention, electrode corrosion does not occur even if the lid is not made of a resin in which the concentration of halogen ions (such as chlorine) is suppressed to a sufficiently low level in order to improve moisture resistance. For this reason, the concentration of halogen ions (such as chlorine) is not suppressed to a sufficiently low level, that is, the lid can be made of a resin containing halogen ions, and the cost can be further reduced.
[0025]
Note that, in the present invention, a conductive electrode is provided on the one main surface of the piezoelectric single crystal substrate, and the conductive electrode is electrically separated from the comb electrode, and It is preferable to adopt a configuration that is electrically connected. It depends on the following reasons. That is, in such a configuration, a local battery effect is likely to occur structurally. Therefore, if the present invention is implemented in such a configuration, a remarkable effect can be obtained.
[0026]
The present invention has a remarkable effect when the piezoelectric single crystal substrate is mainly composed of lithium niobate or lithium tantalate. This is because a local single cell effect is likely to occur in a piezoelectric single crystal substrate containing lithium niobate or lithium tantalate as a main component because of its large polarization vector.
[0027]
Further, in the present invention, the back electrode is preferably made of a material in which a standard electrode potential of an element constituting the main material is equal to or lower than a standard electrode potential constituting a main material of the comb-shaped electrode. preferable. Then, the opposite local battery effect in which the comb-shaped electrode becomes a canod occurs, and the effect of the present invention can be further promoted.
[0028]
Further, in the present invention, the back electrode has a main material the same as the main material of the comb-shaped electrode, and the back electrode has a standard electrode potential of the added metal which is equal to or less than a standard electrode of the added metal of the comb-shaped electrode. Preferably, the back electrode is made of a material whose weight ratio of the added metal is smaller than the weight ratio of the added metal of the comb-shaped electrode. Then, the suppression of the local battery effect of the present invention can be further increased.
[0029]
In the present invention, it is preferable to use an electrode whose main material is aluminum as the comb-shaped electrode. This is because the electrode mainly containing aluminum is most often used as a comb-shaped electrode, and the comb-shaped electrode mainly containing aluminum is apt to cause electrode corrosion due to a local battery effect.
[0030]
Further, the present invention further includes an insulating film mainly composed of silicon oxide or silicon nitride and covering the comb-shaped electrode, and the thickness of the insulating film is preferably 5 to 10 nm. This is based on the following reasons. Although it is preferable to provide the above-described insulating film in order to increase the moisture resistance, it is necessary to reduce the thickness of the insulating film to about 5 to 10 nm in order to suppress the electrode weight and maintain the characteristics of the surface acoustic wave device. is there. However, in such a case, a shape defect such as a pinhole occurs in the insulating film, and it becomes difficult to maintain the moisture resistance. On the other hand, if the present invention is carried out after providing the insulating film, even if the insulating film thickness is about 5 to 10 nm, it is equivalent to the case where the relatively thick insulating film of 10 nm or more is provided. Moisture resistance is obtained.
[0031]
Further, the present invention provides a step 1 of providing an entire surface electrode on one main surface which is a negative surface of spontaneous polarization of the piezoelectric single crystal substrate, and a back surface electrode on another main surface which is a positive surface of spontaneous polarization of the piezoelectric single crystal substrate. This is configured as a method for manufacturing a surface acoustic wave device, including a step 2 of providing and a step 3 of processing the entire surface electrode into a comb-shaped electrode by photolithography.
[0032]
Then, it is not necessary to strictly take measures against electrode corrosion during the production, and the production cost can be reduced accordingly.
[0033]
For example, in step 3, even if a liquid containing an alkaline liquid is used as the working liquid, the possibility of electrode corrosion occurring on the comb-shaped electrode is sufficiently reduced.
[0034]
Also, in the step 3, even if a liquid containing an organic solvent having a water content of 0.5% to 2.5% by weight as a main component is used as a working liquid in the step 3, there is a possibility that electrode corrosion occurs in the comb-shaped electrode. It will be low enough.
[0035]
Further, in the step 3, even if water having a pH of 5.5 to 8.0 is used as the working liquid, the possibility of electrode corrosion occurring on the comb-shaped electrode is sufficiently reduced.
[0036]
Further, in the step of manufacturing the surface acoustic wave device by sealing the surface acoustic wave element, the surface acoustic wave element may be encapsulated in a package having a structure through which moisture can flow between inside and outside of the package. However, the possibility of electrode corrosion occurring on the comb-shaped electrode is sufficiently reduced.
[0037]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0038]
(Embodiment 1)
Embodiment 1 of a surface acoustic wave device according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a surface acoustic wave device according to Embodiment 1 of the present invention.
[0039]
In FIG. 1, reference numeral 1 denotes a piezoelectric single crystal substrate. The piezoelectric single crystal substrate 1 is made of, for example, a ferroelectric piezoelectric material such as lithium tantalate, lithium niobate, potassium niobate, and langasite. In the present embodiment, the piezoelectric single crystal substrate 1 is made of 36 ° Y-cut lithium tantalate.
[0040]
Here, the cut angle will be described with reference to FIG. FIG. 2A shows a state before the piezoelectric single crystal is cut into a wafer, and the x, y, and z axes are as shown in the figure. In this case, the piezoelectric single crystal is spontaneously polarized in the c-axis direction, that is, the z-axis direction.
[0041]
Based on such a structure of the piezoelectric single crystal, for example, as shown in FIG. 2B, a 36 ° y-cut lithium tantalate is newly obtained by rotating the y axis by 36 ° with the x axis as the rotation axis. When the z axis is rotated by 36 ° to be the z ′ axis at the same time as the ′ axis, it can be specified that the wafer is cut so that the y ′ axis is in the normal direction.
[0042]
Such a cut angle is selected in order to obtain a desired device characteristic. For example, in a high-frequency filter, a y-cut lithium tantalate substrate at around 36 ° is often used.
[0043]
Returning to the description of FIG. In FIG. 1, reference numeral 2 denotes a comb-shaped electrode for exciting a surface acoustic wave in the piezoelectric single crystal substrate 1. The comb electrode 2 is provided on one main surface 1 a of the piezoelectric single crystal substrate 1. In the present embodiment, the comb electrode 2 is made of an Al-Cu alloy containing Al as a main material. Cu is included in the comb-shaped electrode 2 in a weight ratio of 0.5%.
[0044]
Reference numeral 3 denotes a back electrode 3. The back electrode 3 is provided over the entire surface of the other main surface 1b of the piezoelectric single crystal substrate 1. In the present embodiment, back electrode 3 is made of Al.
[0045]
Reference numeral 4 denotes a pad electrode. The pad electrode 4 is provided on one main surface 1 a of the piezoelectric single crystal substrate 1. Although not shown, the pad electrode 4 is electrically connected to the comb electrode 2. Reference numeral 5 denotes a protruding electrode. The protruding electrode 5 is provided on the pad electrode 4.
[0046]
Reference numeral 9 denotes a wiring board having electric wiring (not shown). Reference numeral 6 denotes an upper electrode provided on the wiring board 9. The pad electrode 4 is connected to the upper electrode 6 via the protruding electrode 5. Although two projecting electrodes 5 are shown in FIG. 1, a large number of them are provided in accordance with at least the amount of signal extraction. Reference numeral 8 denotes an external terminal electrode provided on the wiring board 9. The external terminal electrode 8 is provided on the back surface of the surface on which the upper electrode 6 is formed. Reference numeral 7 denotes a via electrode provided on the wiring board 9. The via electrode 7 connects the upper electrode 6 and the external terminal electrode 8 between layers.
[0047]
In the present embodiment, the wiring substrate 9 is formed of a ceramic insulating substrate such as alumina. The wiring substrate 9 is formed from the ceramic insulating substrate by making an electrical connection between an electrode pattern such as the comb-shaped electrode 2 formed on the piezoelectric single crystal substrate 1 and the wiring substrate 9 so as to generate electricity generated at the comb-shaped electrode 2 and the like. This is for extracting a signal to the external terminal electrode 8.
[0048]
Reference numeral 10 denotes a cover that covers the wiring board 9 on which the piezoelectric single crystal substrate 1 is mounted. In the present embodiment, a metal cap is used as lid 10.
[0049]
Reference numeral 11 denotes a surface acoustic wave element including the piezoelectric single crystal substrate 1 having the comb electrode 2, the back electrode 3, the pad electrode 4, and the like.
[0050]
In the present embodiment, a package is configured by the wiring board 9 and the lid 10. Further, in another embodiment of the present invention described later, a package is constituted by the wiring board and the lid.
[0051]
Although not shown, the wiring substrate 9 is provided with a depression, and the lid 10 (metal cap) is provided with a claw. Then, the surface acoustic wave element 11 is sealed by the lid 10 and the wiring board 9 by hooking the claw of the lid 10 into the recess of the wiring board 9. However, the sealing structure referred to in the present embodiment is not a sealing structure such as hermetic sealing that prevents entry of almost all substances including gas and liquid, but at least moisture such as water vapor flows in the package. This is a sealing structure (packaging structure) in which the sealing strength is not so high as possible. With the hermetic sealing structure, dew condensation does not occur in the package. However, in the structure of the present embodiment without the hermetic sealing structure, dew condensation may occur in the package. However, in the configuration of the present embodiment, since the structure is simple, the cost can be reduced, and the size and the height can be reduced.
[0052]
Next, a configuration which is a feature of the present embodiment will be described. In the present embodiment, first, as described above, the surface acoustic wave element 11 is housed in a package through which moisture can flow. With such a sealing structure, dew condensation may occur on the surface of the surface acoustic wave element 11 during use of the surface acoustic wave device or during a reliability test.
[0053]
Second, one main surface 1a of the piezoelectric single crystal substrate 1 provided with the comb-shaped electrode 2 is set on the negative surface side of the spontaneous polarization in the piezoelectric single crystal substrate 1, and the piezoelectric single crystal substrate provided with the back electrode 3 is provided. The other main surface 1b of the crystal substrate 1 is set on the plus surface side of spontaneous polarization in the piezoelectric single crystal substrate 1. In addition, the minus surface of the spontaneous polarization refers to the surface of the piezoelectric single crystal substrate 1 in the direction in which the minus component of the polarization component 12 faces, as shown in FIG. 3, and the plus surface of the spontaneous polarization means The surface of the piezoelectric single crystal substrate 1 in the direction in which the plus component constituting the polarization component 12 faces.
[0054]
With the first characteristic configuration of the present embodiment, the surface acoustic wave device allows moisture to easily penetrate from the gap in the lid portion 10, and therefore, the surface of the piezoelectric single crystal substrate 1 is caused by the penetrated moisture (water vapor or the like). Dew condensation is likely to occur. However, in the configuration of the present embodiment, by providing the second characteristic configuration, even if dew condensation occurs, the occurrence of the local battery effect due to the dew condensation is sufficiently suppressed. Electrode corrosion hardly occurs due to the local battery effect. This will be described below.
[0055]
In order to evaluate the surface acoustic wave device of this embodiment, a standing test was performed on this embodiment and a comparative example under the conditions of a temperature of 85 ° C. and a humidity of 85% RH. As a measurement object, a frequency filter having a center frequency of 942.5 MHz, which is a filter having the same configuration as that of the embodiment of the present invention in which the comb-shaped electrode 2 is provided on the minus side of the spontaneous polarization, but has a spontaneously generated comb-shaped electrode 2 100 comparative examples provided on the plus side of polarization were prepared.
[0056]
Then, the insertion loss of the measurement object composed of the example product and the comparative example product was continuously measured, and the time until the deterioration of the insertion loss reached 0.2 dB was measured. Here, the reason why the threshold value of the deterioration of the insertion loss is set to 0.2 dB is based on the fact that it is said that the life of a frequency filter (measurement object) exhibiting the above characteristics is exhausted when the insertion loss is deteriorated by 0.2 dB. ing.
[0057]
As a result of the comparative experiment, it was confirmed that the life of the product of the example of the present invention in which the comb-shaped electrode 2 was provided on the minus side of the spontaneous polarization of the piezoelectric single crystal substrate 1 was more than twice as long as the life of the product of the comparative example. Was.
[0058]
As described above, the present embodiment in which the formation surface of the comb-shaped electrode 2 is limited to the minus surface of the spontaneous polarization of the piezoelectric single crystal substrate 1 as compared with the configuration in which the formation surface of the comb-shaped electrode 2 is not conventionally defined. With this configuration, the moisture resistance of the surface acoustic wave device is improved, and the life is extended. Hereinafter, the reason will be described with reference to FIG.
[0059]
4A and 4B, an electrode 36 made of Al is provided on the plus surface of the spontaneous polarization of the piezoelectric single crystal substrate 1, and an Al-Cu alloy film (Cu is 1% by weight) is provided on the minus surface. 3 shows a configuration in which an electrode 37 is provided. In this case, when both the plus surface and the minus surface of the spontaneous polarization are electrically open, the spontaneous polarization vector P changes to the state shown in FIG. 4A according to the direction of the spontaneous polarization component. In this state, if dew condensation occurs across the electrode 36 and the electrode 37, a local battery as shown in FIG. 4B may be generated. In FIGS. 4A and 4B, reference numeral 38 denotes a polarization component.
[0060]
However, when considering the vector component in the thickness direction of the piezoelectric single crystal substrate 1 among the vector components of the spontaneous polarization vector P, since the electric displacement vector Dv in the thickness direction is constant, the electric field vector Ev that satisfies the equation of Dv = Pv + Ev Appear along the thickness direction of the piezoelectric single crystal substrate 1. Therefore, even if dew condensation occurs across the electrode 36 and the electrode 37 because the electric charge Ev flows as a current, a local battery is not generated and emission of electrons due to electrode oxidation is reduced. Thereby, electrode corrosion is suppressed.
[0061]
The effect of the present invention increases as the spontaneous polarization vector P increases. Therefore, it is very effective for piezoelectric single crystal materials having ferroelectric properties such as the above-mentioned lithium niobate, lithium tantalate, potassium niobate, and langasite.
[0062]
Although the surface acoustic wave device having the flip-chip structure has been described in the present embodiment, the surface acoustic wave element 11 is die-bonded on the wiring board 9 as shown in FIG. The same effect is obtained in the structure. In FIG. 5, reference numeral 13 denotes an Al wire. Reference numeral 14 denotes an electrode provided on the surface of the wiring substrate 9 on which the surface acoustic wave element is mounted. Further, in FIG. 5, the same parts as those in FIG. 1 are denoted by the same reference numerals. In the wire bonding structure shown in FIG. 5, the surface acoustic wave element 11 is die-bonded to the wiring substrate 9 by bringing the back electrode 3 into close contact with the electrode 14 of the wiring substrate 9 and electrically connecting them. The pad electrode 4 and the upper electrode 6 are connected by an Al wire 13.
[0063]
Also in the wire bonding structure shown in FIG. 5, even if dew condensation occurs across electrode 14 and comb electrode 2, the effect described in the present embodiment (suppression of the local electrode effect) can be obtained. In the configuration of FIG. 5, the same effect can be obtained by using a ceramic substrate of alumina, a substrate of another ceramic substrate, a glass epoxy substrate, or the like as the wiring substrate 9. In addition, although the sealing was performed using the metal cap 10, the same effect can be obtained by a structure using a resin mold.
[0064]
The point is that the structure of the present invention is provided even if the sealing structure is simple, inexpensive and can be miniaturized, but is not hermetically sealed, so that dew condensation may occur on the surface acoustic wave element 11. Thus, corrosion caused by the local electrode effect can be suppressed.
[0065]
In the present invention, it is preferable to use a material whose standard electrode potential is equal to or lower than the standard electrode potential of the main electrode material of the comb-shaped electrode 2 as an element constituting the back electrode 3. This is because if a material having a higher standard electrode potential than the comb electrode 2 is selected as the material of the back electrode 3, a local electrode in which the comb electrode 2 becomes an anode due to the standard electrode potential difference between the back electrode 3 and the comb electrode 2. This is because a battery effect may occur and the effect of the present invention may be reduced. Conversely, if a material having a lower standard electrode potential than that of the comb-shaped electrode 2 is selected as the material of the back electrode 3, a local battery effect in which the comb-shaped electrode 2 serves as a cathode occurs, and the effect of the present embodiment is increased.
[0066]
For example, in the case of using an Al—Cu alloy as the material of the comb-shaped electrode 2, when comparing the case where Ni is used as the material of the back electrode 3 and the case where Al is used as the material of the back electrode 3, the former is more suitable for the present invention. The effect of the invention is reduced.
[0067]
Conversely, when the Al—Cu alloy is used as the material of the comb-shaped electrode 2, the Al—Mg alloy (10% by weight of Mg) is used as the material of the back electrode 3, and the Al is used as the material of the back electrode 3. The effect of the present invention is greater in the former case than in the former case.
[0068]
Further, when the Al—Cu alloy (weight ratio Cu: 1%) is used as the comb-shaped electrode 2, when the Al—Cu (weight ratio Cu: 0.5%) is used as the material of the back electrode 3, Compared with the case where Al was used as the material No. 3, the effect of the present invention was hardly changed in both cases.
[0069]
As described above, even when the same additive metal is added, an effect that is hardly changed can be obtained by reducing the additive ratio (weight ratio) of the additive metal.
[0070]
Even when a material whose standard electrode potential of the elements constituting the back electrode 3 is larger than the standard electrode potential of the main electrode material of the comb-shaped electrode 2 is used, by reducing the amount of the metal added, The effects of the invention can be enjoyed without any problem.
[0071]
For example, when the Al—Ti alloy (weight ratio Ti: 1%) is used as the comb electrode 2, the Al—Cu (weight ratio Cu: 0.3%) is used as the back electrode 3, and the material of the back electrode 3 is different. As compared with the case where Al was used, the weight ratio of Cu in the former was small, so that the effect of the present invention was hardly changed in both cases.
[0072]
The configuration of the present invention also has the following first and second advantages. First, the first advantage will be described. The surface acoustic wave element 11 has a structure in which a protective film such as silicon nitride or silicon oxide is provided on the comb-shaped electrode 2 to improve the moisture resistance of the device. However, this structure has a disadvantage that when the thickness of the protective film is 10 nm or less, it becomes difficult to secure moisture resistance due to the influence of pinholes and the like. On the other hand, when the protective film structure is used in combination with the structure of the present invention, even when the thickness of the protective film is in the range of 5 to 10 nm, the same effect as when a protective film of 10 nm or more is formed. Moisture resistance is obtained.
[0073]
Next, a second advantage will be described. In some cases, a resin is used as a package material of the surface acoustic wave element 11. In this case, conventionally, it has been necessary to use a resin that has been strictly controlled and manufactured, such as reducing the chlorine ion concentration to several tens of ppm or less, as the package material. On the other hand, if the configuration of the present invention is adopted, even if a resin having a chlorine ion concentration of about 100 ppm is used for the package material, the reliability is not significantly impaired.
[0074]
Next, a method of manufacturing the surface acoustic wave device according to the present embodiment will be described with reference to FIG. First, in a first step, an entire surface electrode 15 is formed on one main surface 1a of the piezoelectric single crystal substrate 1 which is a negative surface of spontaneous polarization. The whole surface electrode 15 can be formed by using a manufacturing method such as a sputtering method, a vacuum evaporation method, and an ion plating method. In the present embodiment, it is manufactured by a sputtering method.
[0075]
Next, in a second step, a back surface electrode 3 is formed on the other main surface 1b which is the spontaneous polarization plus surface of the piezoelectric single crystal substrate 1. The back surface electrode 3 is manufactured by the same method as that of the entire surface electrode 15, but in the present embodiment, it is manufactured by a vacuum evaporation method. This is because the back electrode 3 has a small effect on the device characteristics unlike the full-surface electrode 15, so that an inexpensive vacuum deposition method can be used (see FIG. 6A).
[0076]
Next, in a third step, a resist 16 is applied on the entire surface electrode 15. The resist 16 is applied by spin coating. In the present embodiment, a positive resist is used as the resist 16, but a negative resist may be used if a desired shape is obtained (see FIG. 6B).
[0077]
Next, in a fourth step, a portion of the resist 16 from which the entire surface electrode 15 is removed in a later step is exposed. For exposure, a stepper device is used. Next, in a fifth step, after the resist 16 is developed, the resist in the exposed portion is removed. As the developer used for the development, there are a water-based developer and a solvent-based developer. In this embodiment, a solvent-based developer is used (see FIG. 6C).
[0078]
Next, in a sixth step, the entire surface electrode 15 is patterned by dry etching. At this stage, the comb electrode 2 and the pad electrode 4 are formed. Next, in a seventh step, the remaining resist 16 is removed. For removing the resist, an aqueous stripping solution is used (see FIG. 6D).
[0079]
Next, in an eighth step, the bump electrodes 5 are formed on the pad electrodes 4. Further, in a ninth step, the surface acoustic wave elements 11 are cut out by dicing (see FIG. 6E).
[0080]
Next, in a tenth step, the surface acoustic wave element 11 is mounted on the wiring board 9, and the lid (metal cap) 10 seals the surface acoustic wave element 11. Sealing is performed as follows. The wiring board 9 is provided with a not-shown depression, and the lid 10 (metal cap) is provided with a not-shown claw. Then, the surface acoustic wave element 11 is sealed by the lid 10 and the wiring board 9 by hooking the claws of the lid 10 in the depressions of the wiring board 9. However, the sealing structure here is not a sealing structure such as airtight sealing that prevents almost all substances including gas and liquid from being mixed, and at least moisture such as water vapor can be transferred inside and outside the package. It is a sealing structure (packaging structure) in which the sealing strength is not so high. If the hermetic sealing structure is used, no dew condensation occurs in the package. However, if the hermetic sealing structure is not used, dew condensation may occur in the package.
[0081]
In the present embodiment, the first step constitutes step 1 in the claims of the present invention, the second step constitutes step 2, the third to seventh steps constitute step 3, and the ninth step Step 4 constitutes the process, and Step 5 constitutes the tenth process.
[0082]
The surface acoustic wave device was manufactured as described above. As described above, in the surface acoustic wave device having no hermetic sealing structure, there is a possibility that dew condensation may occur in the package, but no corrosion of the comb-shaped electrode 2 was observed. Further, since the lid 10 is attached to the piezoelectric single crystal substrate 1 with a simple sealing structure, the structure is simple, inexpensive, and small (including a reduction in height).
[0083]
The following was performed to more clearly examine the effects of the manufacturing method of the present embodiment. In addition to the embodiment of the present invention in which the entire surface electrode 15 is formed on the minus surface (one main surface 1a) of spontaneous polarization and the back surface electrode 3 is formed on the plus surface (other main surface 1b) of spontaneous polarization, The surface acoustic wave device is manufactured according to a comparative example in which the back surface electrode 3 is formed on the plus surface (other main surface 1b) and the back surface electrode 3 is formed on the minus surface (one main surface 1a) of spontaneous polarization. In the comparative example, the same steps are performed except that the arrangement positions of the full surface electrode 15 and the back surface electrode 3 are different from those of the embodiment of the present invention. An embodiment product and a comparative example product manufactured under such conditions are comparatively manufactured. At that time, the following considerations were made.
[0084]
First, as a first study, in the fifth step, development was performed using an alkaline developer mainly containing water as a developer. The developer contains about several% of TMAH (tetramethylammonium hydroxide) and is alkaline.
[0085]
In the case of using the new developing solution, no problem such as corrosion occurred in the product of the embodiment of the present invention and the product of the comparative example. On the other hand, when the same developer is used a plurality of times, corrosion occurs in the comb-shaped electrode 2 in both the embodiment product of the present invention and the comparative product. Such corrosion is caused by the following factors. That is, by repeating the development, impurities that promote corrosion, for example, chloride ions, etc., enter the developer. Then, while the development is repeated, the amount of penetration of the corrosion-promoting impurities becomes too large, and corrosion starts.
[0086]
A comparison between the manufacturing method of the embodiment of the present invention and the manufacturing method of the comparative example in terms of the number of times of use of the developer that causes corrosion of the comb-shaped electrode 2 (hereinafter referred to as the limit number of uses) clearly shows that the embodiment of the present invention is Had a larger number of uses. Specifically, the limit number of uses in the embodiment of the present invention was about twice that in the comparative example.
[0087]
The same study was conducted for the stripping solution, but the result was almost the same as that of the developing solution.
[0088]
According to the first study described above, when a surface acoustic wave device is manufactured by the manufacturing method of the embodiment of the present invention under the condition that an aqueous developer or a stripper is used, the surface acoustic wave device is manufactured by the manufacturing method of the comparative example. As compared with the case, the use limit number of the developing solution and the stripping solution can be doubled or more, and the manufacturing cost can be reduced accordingly.
[0089]
Next, as a second study, a production experiment similar to that described above was conducted using a solvent-based developer mainly containing an organic solvent as a developer. Also in this production experiment, when a new developing solution was used, no problem such as corrosion occurred in both the embodiment of the present invention and the comparative example. On the other hand, when the same developer is used for a long time, the comb-shaped electrode 2 is corroded in both the embodiment of the present invention and the comparative example.
[0090]
Thus, the corrosion that occurs when developing with a developing solution containing an organic solvent as a main component depends not on the number of times the developing solution is used (the number of times of development) but on the elapsed time since the use of the developing solution. The reason is that the ratio of water in the organic solvent increases due to the incorporation of water vapor and the like in the atmosphere into the organic solvent.
[0091]
A comparison between the manufacturing method of the embodiment of the present invention and the manufacturing method of the comparative example in terms of the use time (hereinafter referred to as the “limit use time”) of the developer in which the comb electrode 2 causes corrosion clearly shows that the embodiment of the present invention is clearly shown. Has a longer limit usage time. Specifically, the limit use time in the embodiment of the present invention is about three times that of the comparative example.
[0092]
At this time, in the comparative example, when the water concentration in the developing solution at which the corrosion of the comb-shaped electrode 2 started to be generated was examined, it was 0.5% by weight. On the other hand, according to the embodiment of the present invention, when the moisture concentration in the developing solution at which corrosion of the comb-shaped electrode 2 starts to be generated was 2.5% by weight. To suppress the water concentration of the developer to 2.5% or less, not so strict quality control and storage control are required, but to suppress it to 0.5% or less, quite strict quality control and storage control are required. Need. As described above, in the manufacturing method of the present invention, since strictness is not required for quality control and storage management of the developer and the like, the manufacturing cost can be reduced accordingly.
[0093]
The same study was conducted for the stripping solution, but the result was almost the same as that of the developing solution.
[0094]
According to the second study described above, when a surface acoustic wave device is manufactured by the manufacturing method of the embodiment of the present invention under the condition that a solvent-based developer or stripper is used, the use of the developer or stripper is The limit time can be extended three times or more, and the manufacturing cost can be reduced accordingly. Furthermore, it is not necessary to perform strict management of the developer and the stripper, for example, management processing such as monitoring the amount of water and performing the process in a closed state, so that the manufacturing cost can be reduced.
[0095]
Next, as a third study, a manufacturing experiment similar to that described above was conducted by changing the pH of water jetted during dicing in the ninth step in the range of 5 to 7. Usually, in order to prevent the comb-shaped electrode 2 from being corroded due to the local battery effect, the pH of water jetted onto the piezoelectric single crystal substrate 1 during the dicing process is adjusted to the acidic side. Therefore, in the manufacturing method of the embodiment of the present invention and the manufacturing method of the comparative example, the pH range of the injection water at the time of the dicing treatment in which the comb-shaped electrode 2 does not corrode was measured. As a result of the measurement, the pH range in the comparative example was 5.0 to 5.5, whereas the pH range in the embodiment of the present invention was 5.0 to 6.5.
[0096]
According to the third study described above, when a surface acoustic wave device is manufactured by the manufacturing method according to the embodiment of the present invention, the range of the pH of water to be jetted at the time of the dicing process is widened, and the process management is made easier by that much. As a result, manufacturing costs can be kept low.
[0097]
(Embodiment 2)
The surface acoustic wave device according to Embodiment 2 of the present invention will be described with reference to FIG. The surface acoustic wave device according to the present embodiment is characterized in that, as shown in FIG. 7, a conductive electrode 17 is provided, and the back surface of the metal lid 10 is in contact with the back electrode 3. .
[0098]
The conduction electrode 17 is provided on one main surface 1 a of the piezoelectric single crystal substrate 1. The conductive electrode 17 includes an extraction electrode (not shown, an electrode electrically connected to the pad electrode 4 and the conductive electrode), the pad electrode 4, the protruding electrode 5, the upper electrode 6, the via electrode 7, and the like. The back electrode 3 is electrically connected to the rear electrode 3 via the lid 10. Other structures are the same as in the first embodiment.
[0099]
FIG. 8 shows another example of the present embodiment, in which the electrical connection structure is wire bonding. Since the configuration is basically the same as in FIGS. 5 and 7, the reference numerals in FIG. 8 are the same as those in FIGS.
[0100]
In the present embodiment, the conducting electrode 17 is provided on the negative surface (one main surface 1a) of the spontaneous polarization of the piezoelectric single crystal substrate 1. In this case, if dew condensation occurs between the conductive electrode 17 and the comb-shaped electrode 2, a local battery effect may be generated there. However, even in such a case, the local battery effect is suppressed in the same manner as described in the first embodiment, so that no electrode corrosion occurs on the comb-shaped electrode 2 or the like.
[0101]
According to the present embodiment, even when dew condensation occurs in a relatively small area, or when most of the back electrode 3 is not exposed as shown in FIG. Can be obtained.
[0102]
(Embodiment 3)
An electronic circuit device (in which the surface acoustic wave device of the present invention is incorporated) according to Embodiment 3 of the present invention will be described with reference to FIG. In FIG. 9, portions denoted by the same reference numerals as those in FIG. 5 are the same as those in the first embodiment, and therefore, description thereof will be omitted. This electronic circuit device can be considered to be one in which electronic components are incorporated in the surface acoustic wave device of the first embodiment.
[0103]
In FIG. 9, reference numeral 18 denotes a lid. The cover 18 seals the entire electronic circuit device. Reference numeral 19 denotes an electronic component. The circuit element 19 is composed of electronic components such as a resistor, a capacitor, a coil, and a semiconductor device. Although only one is shown in the figure, a plurality of circuit elements are usually mounted. Also in this embodiment, a plurality of electronic components are mounted. The circuit element 19 is mounted by solder reflow. 20 is a circuit board. The circuit board 20 incorporates passive components (not shown) such as coils and capacitors. As in the first embodiment, the cover 18 is provided with a depression on the side surface of the circuit board 20 and is fixed by hooking a claw of the cover (metal cap) 18 to seal the circuit board 20. Reference numeral 21 denotes a built-in electrode provided in the circuit board 20. Reference numeral 22 denotes a via electrode for connecting the built-in electrode 21. Reference numeral 23 denotes a terminal electrode provided on the back surface of the circuit board 20. The surface acoustic wave element 11 has substantially the same configuration as the surface acoustic wave element of FIG. 5 described in the first embodiment.
[0104]
In general, in the electronic circuit device of the present embodiment, the size, particularly the height, of the electronic circuit device becomes very large in order to hermetically seal the mounted surface acoustic wave device. For example, the height of a general electronic component can be reduced to 0.7 mm or less, whereas the height of a general electronic circuit device on which a surface acoustic wave device is mounted increases to about 1.2 to 1.5 mm.
[0105]
On the other hand, the height of the surface acoustic wave element 11 in the present embodiment is about 0.7 mm, which is almost equal to that of the electronic component 19, and the height of the electronic circuit device is reduced by about 0.5 to 0.8 mm in the related art. It has become possible. This is because adopting the configuration of the present invention (providing the comb-shaped electrode 2 on the minus side of spontaneous polarization) eliminates the need to attach the cover 18 to the circuit board 20 in a strictly hermetically sealed state.
[0106]
By mounting the elastic surface element 11 described with reference to FIG. 7, the height of the electronic circuit device can be further reduced by about 0.2 to 0.3 mm. Needless to say, in the third embodiment, the same effects as those described in the first embodiment can be obtained.
[0107]
Further, even if the conductive electrode 17 is provided on the minus side of the spontaneous polarization of the piezoelectric single crystal substrate 1, the effects of the present embodiment and the effects described in the second embodiment can be obtained.
[0108]
(Embodiment 4)
A method for manufacturing a surface acoustic wave device according to Embodiment 4 of the present invention will be described. In the present embodiment, a cleaning step for removing residual impurities such as chlorine or a chlorine compound is added to the manufacturing method described in Embodiment 1 after the resist is stripped in the seventh step. It is.
[0109]
In the manufacturing method of the present embodiment, cleaning was performed by using a water-based surfactant as a cleaning liquid and performing nitrogen bubbling for 20 minutes. In the comparative example in which the comb-shaped electrode 2 was provided on the plus surface of the spontaneous polarization, electrode corrosion was observed in part, but no electrode corrosion occurred in the manufacturing method of this embodiment. In addition, even in the case of Megasonic, which performs cleaning while applying ultrasonic waves of several hundred kHz to about 1 MHz to the cleaning liquid, even in the case where cleaning is performed for 20 minutes, similarly, in the comparative example, electrode corrosion occurs, but the manufacturing of the present embodiment is also performed. The method did not cause electrode corrosion.
[0110]
It is known that the residual impurity residue affects the reliability of the device such as moisture resistance. In particular, this is remarkable in a surface acoustic wave device that does not hermetically seal as in the present invention. In particular, when Al is used as an electrode material for the comb-shaped electrode 2 or the like, a chlorine-based gas is often used as a dry etchant, and chlorine residues are likely to remain. On the other hand, if the manufacturing method of the present embodiment is used, electrode corrosion caused by the local battery effect can be effectively suppressed even if the cleaning is performed by a cleaning method effective for removing residual chlorine. Thus, a highly reliable surface acoustic wave device can be manufactured.
[0111]
(Embodiment 5)
A method for manufacturing a surface acoustic wave device according to Embodiment 5 of the present invention will be described with reference to FIG. First, in the first step, the entire surface electrode 15 is provided on the negative surface of the piezoelectric single crystal substrate 1 with the spontaneous polarization by sputtering. Regarding the method for forming the entire surface electrode 15, the method described in Embodiment 1 can be used. Next, in a second step, the back surface electrode 3 is provided on the plus surface of the spontaneous polarization of the piezoelectric single crystal substrate 1 by vacuum evaporation. Furthermore, by performing the third step (the same step as the third to seventh steps in the first embodiment), comb-shaped electrode 2 is formed on the spontaneous electrode minus surface of piezoelectric single crystal substrate 1. . (See FIG. 10A).
[0112]
Next, in a fourth step, a resist 25 (not shown) is applied to the surface of the piezoelectric single crystal substrate 1 on which the comb-shaped electrodes are formed. In the present embodiment, a negative resist is used as the resist 25.
[0113]
Next, in a fifth step, portions other than the pad electrode 4 are exposed. Next, in a sixth step, the resist 25 is developed to remove the unexposed portion of the pad electrode 4 to form a resist pattern 25 '. Next, in a seventh step, the entire surface electrode 26 is provided on the surface of the piezoelectric single crystal substrate 1 on which the comb-shaped electrodes are formed by vacuum evaporation (see FIG. 10B). The entire surface electrode 26 finally becomes the pad reinforcing electrode 24 by a process described later.
[0114]
Next, in an eighth step, the resist pattern 25 'is removed by a solvent-based stripping solution containing an organic solvent as a main component. At this time, at the same time, the region of the entire surface electrode 26 disposed on the resist pattern 25 ′ is selectively peeled off, and only the region of the entire surface electrode 26 disposed on the pad electrode 4 remains. The remaining entire surface electrode 26 becomes the pad reinforcing electrode 24. (See FIG. 10 (c)). Such a process is usually called a lift-off process.
[0115]
Next, in a ninth step, the surface acoustic wave element 11 is cut out by dicing (see FIG. 10D). Next, in a tenth step, the surface acoustic wave element 11 is packaged by using the lid 10 (however, sealing does not take an airtight sealing structure), and the elastic surface device is completed.
[0116]
The fourth to eighth steps in the manufacturing method of the present embodiment described above are steps for providing the pad reinforcing electrode 24. By providing the pad reinforcing electrode 24 in this manner, the connection reliability with the protruding electrode 5 or the wire 16 increases. However, in the lift-off step conventionally performed for forming the pad reinforcing electrode, unless the liquid management of the organic solvent used in the eighth step is strictly performed, there is a problem that the comb electrode 2 is corroded. Corrosion is mainly caused by the incorporation of moisture into the stripping solution, as in the second study described in the first embodiment. On the other hand, in the manufacturing method of the present embodiment, by providing the comb-shaped electrode 2 on the negative spontaneous polarization surface of the piezoelectric single crystal substrate 1, it is possible to effectively suppress the corrosion of the comb-shaped electrode 2. Therefore, it is not necessary to strictly manage the liquid of the organic solvent used in the eighth step, so that the cost can be reduced.
[0117]
Further, in the case of performing the eighth step, in order to prevent the region of the stripped whole electrode 26 from re-adhering to the comb-shaped electrode 2, the stripping liquid is heated and the stripping process of the whole electrode 26 is performed quickly. There is a need. In this case, by heating the stripping solution, the incorporation of moisture into the stripping solution becomes more severe, and it is necessary to change the stripping solution in a short time. More specifically, in order to prevent the corrosion of the comb-shaped electrode 2 reliably, the content of water in the stripping solution is suppressed to about 0.5% by weight, as described in the first embodiment. There is a need. However, in such a case, it is conceivable that the liquid needs to be replaced in about several hours. On the other hand, if the manufacturing method of the present embodiment is adopted, the eighth step can be performed without causing electrode corrosion of the comb-shaped electrode 2 even when the water content of the stripping solution is increased to about 2.5%. Becomes possible. Therefore, the life of the stripper is extended, and the manufacturing cost is reduced.
[0118]
Although a negative resist is used in the present embodiment, it goes without saying that a similar effect can be obtained even if a positive resist is used.
[0119]
【The invention's effect】
According to the present invention described above, a surface acoustic wave device and an electronic circuit device having a simple structure and excellent in moisture resistance can be realized. Further, according to the manufacturing method of the present invention, strict control of the process is not required by a simple method, and the manufacturing yield can be improved. As a result, manufacturing costs can be reduced.
[Brief description of the drawings]
FIG. 1 is a sectional view of a surface acoustic wave device according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining a cutting angle of a piezoelectric single crystal.
FIG. 3 is a diagram provided for explanation of spontaneous polarization of a piezoelectric single crystal.
FIG. 4 is a diagram for explaining the principle of the present invention.
FIG. 5 is a sectional view of a modification of the first embodiment.
FIG. 6 is a diagram for explaining a method of manufacturing the surface acoustic wave device according to the first embodiment;
FIG. 7 is a sectional view of a surface acoustic wave device according to Embodiment 2 of the present invention.
FIG. 8 is a sectional view of a modification of the second embodiment.
FIG. 9 is a sectional view of an electronic circuit device according to a third embodiment of the present invention.
FIG. 10 is a diagram for explaining a method of manufacturing the surface acoustic wave device according to the fourth embodiment of the present invention.
FIG. 11 is a sectional view of a conventional example.
FIG. 12 is a sectional view of a main part of a conventional example.
[Explanation of symbols]
1 piezoelectric single crystal substrate 1a one main surface 1b other main surface 2 comb-shaped electrode
3 Back electrode 4 Pad electrode 5 Protruding electrode 6 Upper electrode
7 Via electrode 8 External terminal electrode 9 Wiring board
10 lid part 11 surface acoustic wave element 13Al wire
14 electrode 15 whole surface electrode 16 resist 17 conductive electrode
18 Lid 19 Electronic components 20 Circuit board 21 Built-in electrode 22 Via electrode
23 terminal electrode 24 pad reinforcement electrode
25 resist 25 'resist pattern 26 whole surface electrode
36 electrodes 37 electrodes 38 polarization components

Claims (17)

A piezoelectric single-crystal substrate, a comb-shaped electrode provided on one main surface of the piezoelectric single-crystal substrate, and a back electrode provided on the other main surface of the piezoelectric single-crystal substrate,
The one main surface on which the comb-shaped electrode is provided is a minus surface of spontaneous polarization of the piezoelectric single crystal substrate,
A surface acoustic wave device characterized by the above-mentioned. A surface acoustic wave element, and a package that houses the surface acoustic wave element;
The surface acoustic wave element includes a piezoelectric single crystal substrate, a comb-shaped electrode provided on one main surface of the piezoelectric single crystal substrate, and a back electrode provided on the other main surface of the piezoelectric single crystal substrate,
The one main surface on which the comb-shaped electrode is provided is a minus surface of spontaneous polarization of the piezoelectric single crystal substrate,
A surface acoustic wave device characterized by the above-mentioned. The surface acoustic wave device according to claim 2,
The package has a sealing structure that covers the surface acoustic wave element and allows water to flow in and out of the package.
A surface acoustic wave device characterized by the above-mentioned. The surface acoustic wave device according to claim 3,
The package has a wiring board on which the surface acoustic wave element is mounted, and a lid that covers a surface of the wiring board on which the surface acoustic wave element is arranged, together with the surface acoustic wave element.
A surface acoustic wave device characterized by the above-mentioned. The surface acoustic wave device according to claim 4,
Circuit elements are mixedly mounted on the wiring board,
A surface acoustic wave device characterized by the above-mentioned. The surface acoustic wave device according to claim 4 or 5,
The lid is made of a resin containing halogen ions,
A surface acoustic wave device characterized by the above-mentioned. The surface acoustic wave device according to any one of claims 2 to 6,
A conductive electrode is provided on the one main surface of the piezoelectric single crystal substrate,
The conductive electrode is electrically separated from the comb-shaped electrode, and is electrically connected to the back electrode.
A surface acoustic wave device characterized by the above-mentioned. The surface acoustic wave device according to any one of claims 2 to 7,
The piezoelectric single crystal substrate is mainly composed of lithium niobate or lithium tantalate,
A surface acoustic wave device characterized by the above-mentioned. The surface acoustic wave device according to any one of claims 2 to 8,
The back electrode is formed of a material having a standard electrode potential of an element constituting the main material thereof is equal to or lower than a standard electrode potential constituting a main material of the comb-shaped electrode,
A surface acoustic wave device characterized by the above-mentioned. The surface acoustic wave device according to any one of claims 2 to 9,
The main material of the back electrode is the same as the main material of the comb-shaped electrode,
In the back electrode, the standard electrode potential of the additional metal is equal to or lower than the standard electrode of the additional metal of the comb-shaped electrode,
The back electrode is made of a material whose weight ratio of the added metal is smaller than the weight ratio of the added metal of the comb-shaped electrode.
A surface acoustic wave device characterized by the above-mentioned. The surface acoustic wave device according to any one of claims 2 to 10,
The main material of the comb-shaped electrode is aluminum,
A surface acoustic wave device characterized by the above-mentioned. The surface acoustic wave device according to any one of claims 2 to 11,
The semiconductor device further includes an insulating film covering the comb-shaped electrode, wherein the insulating film has silicon oxide or silicon nitride as a main component and a thickness of 5 to 10 nm.
A surface acoustic wave device characterized by the above-mentioned. A step 1 of providing an entire surface electrode on one main surface of the piezoelectric single crystal substrate, which is a negative surface of spontaneous polarization;
A step 2 of providing a back surface electrode on the other main surface, which is a positive surface of the spontaneous polarization of the piezoelectric single crystal substrate,
A step 3 of processing the entire surface electrode into a comb-shaped electrode by photolithography;
A method for manufacturing a surface acoustic wave device, comprising: The method for manufacturing a surface acoustic wave device according to claim 13,
In the step 3, a liquid containing an alkaline liquid is used as a working liquid.
A method for manufacturing a surface acoustic wave device. The method for manufacturing a surface acoustic wave device according to claim 13,
In the step 3, a liquid mainly containing an organic solvent having a water content of 0.5% to 2.5% by weight is used as a working liquid.
A method for manufacturing a surface acoustic wave device. The method for manufacturing a surface acoustic wave device according to claim 13,
In the step 3, water having a pH of 5.5 to 8.0 is used as a working liquid.
A method for manufacturing a surface acoustic wave device. A step 1 of providing an entire surface electrode on one main surface of the piezoelectric single crystal substrate, which is a negative surface of spontaneous polarization;
A step 2 of providing a back surface electrode on the other main surface, which is a positive surface of the spontaneous polarization of the piezoelectric single crystal substrate,
A step 3 of processing the entire surface electrode into a comb-shaped electrode by photolithography, a step 4 of cutting the piezoelectric single crystal substrate to cut out individual surface acoustic wave elements,
A step 5 of enclosing the surface acoustic wave element in a package having a structure through which moisture can flow inside and outside the package;
A method for manufacturing a surface acoustic wave device, comprising:

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