JP2001168676A - Surface acoustic wave device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface acoustic wave device and its manufacturing method where the propagating characteristic of a surface acoustic wave is excellent since discharging is not generated easily between IDT electrodes. SOLUTION: This device is provided with a piezoelectric substrate 11, a first interdigital electrode 12a and a second interdigital electrode 12b, both of which are formed to face each other on the substrate 11. The substrate 11 is provided with a doping area 11a doped with a material of at least one form selected from an atom, a molecule and a cluster on a surface 11s between the electrode 12a and the electrode 12b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface acoustic wave device and a method for manufacturing the same.

[0002]

2. Description of the Related Art Surface acoustic wave devices are used in high-frequency circuits of mobile phones. As an example of a conventional surface acoustic wave device (hereinafter, sometimes referred to as a SAW device), a cross-sectional view of a SAW filter 1 is shown in FIG. SA
The W filter 1 includes a piezoelectric substrate 2 and a pair of interdigital electrodes (Inter Digit) formed on the substrate 2.
al Transducer (hereinafter sometimes referred to as IDT electrode) 3a and 3b. The substrate 2 is made of Li
It is made of TaO ₃ or LiNbO ₃ .

In the SAW filter 1, when the substrate 2 has pyroelectricity, the charge distribution on the surface of the substrate 2 becomes non-uniform due to a temperature change in an assembling process or a temperature change when used as a device. As a result, the IDT electrodes 3a and I
A potential difference is generated between the DT electrode 3b and a discharge occurs between the electrodes. When a discharge occurs between the electrodes, the electrodes are blown, and as a result, the filter characteristics deteriorate or shift.

In order to solve the above problem, the following 3
Two methods have been proposed. As a first method, a method of connecting two IDT electrodes with fine metal electrodes has been proposed (see Japanese Patent Application Laid-Open No. 3-29407). However, since this metal electrode is fine, there has been a problem that the metal electrode is easily broken by heat or the like and lacks reliability.

As a second method, a method of forming a thin film having a predetermined resistivity so as to cover the IDT electrode has been proposed (Japanese Patent Application Laid-Open Nos. 1-106611 and 10-30).
3681, JP-A-11-74750). However, in the above method, since the IDT electrode is covered with the thin film, there is a problem that the propagation characteristics of the SAW deteriorate. There is also a problem that a thin film forming step is required.

As a third method, a method has been proposed in which a substrate is heat-treated in a reducing gas such as a green gas in advance to reduce its surface resistance and then form an IDT electrode (JP-A-11-92147). Reference).

[0007]

However, the SAW filter obtained by the third method has a problem that the insertion loss of the high-frequency characteristics increases. This is presumably because, when the substrate is heat-treated in a reducing gas, lattice defects occur to a considerable depth of the substrate, which affects the propagation of surface acoustic wave energy.

To solve the above problem, the present invention provides an ID
It is an object of the present invention to provide a surface acoustic wave device in which a discharge between T electrodes is less likely to occur and which has a good surface acoustic wave propagation characteristic, and a method of manufacturing the same.

[0009]

In order to achieve the above object, a first surface acoustic wave device according to the present invention comprises a substrate having piezoelectricity and a first comb formed on the substrate so as to face the substrate. A surface acoustic wave device comprising a tooth-shaped electrode and a second comb-shaped electrode, wherein the substrate is provided on a surface between the first comb-shaped electrode and the second comb-shaped electrode. atom,
There is provided a doping region doped with at least one form of a substance (which may be an ion or a radical) selected from molecules and clusters. The present invention is based on a new finding of the present inventors that the formation of the doping region between the electrodes suppresses the discharge between the electrodes. The reason why the discharge is suppressed by forming the doping region is not clear at present. However, one reason may be that the doped region has a lower resistance than the substrate before doping. In the above SAW device, when a potential difference occurs between the first IDT electrode and the second IDT electrode, charges move through the doping region, and the potential difference is eliminated. Therefore, according to the SAW device, discharge between the IDT electrodes can be suppressed. Further, in the above SAW device, since the doping region is formed only on the substrate surface, a SAW device having good surface acoustic wave propagation characteristics can be obtained.

In the above SAW device, the depth of the doping region may be 50 nm or less. Most of the surface acoustic waves propagating on the surface of the SAW device propagate from the surface of the substrate to a depth of about 程度 of the surface acoustic wave wavelength. In the case of a 2 GHz band SAW device using LiNbO ₃ , the propagation region has a depth of 0.5 μm from the substrate surface.
To the extent. According to the above configuration, since the doping region is sufficiently thinner than the propagation region, a SAW device having particularly good surface acoustic wave propagation characteristics can be obtained.

In the above SAW device, it is preferable that the doping region has a lower resistance than the inside of the substrate.

In the above SAW device, the sheet resistance of the doping region may be in the range of 10 ⁸ Ω / □ to 10 ¹⁵ Ω / □. According to the above configuration, discharge between the IDT electrodes can be particularly suppressed.

In the above SAW device, the substance is at least one selected from a reducing gas, silane, nitrogen, oxygen, argon, silicon, arsenic, boron, phosphorus, tin, indium, chromium, tantalum, molybdenum, germanium, and nickel. One of them may be ionized. According to the above configuration, the conductivity near the surface of the substrate is increased, so that the accumulation of charges on the substrate can be prevented.

In the above SAW device, the first and second comb-shaped electrodes may include an insulating layer on a surface. According to the above configuration, it is possible to prevent a short circuit of the electrode due to the conductive particles or the like. Further, according to the above configuration, corrosion of the electrode can be prevented, and the effect is particularly large when the electrode contains aluminum. In addition, when the insulating layer is formed by doping a metal with an impurity, the doping of the impurity reduces the crystal grain size on the electrode surface and prevents movement of atoms such as Al. Therefore, in this case, migration of the electrode is suppressed.

In the above SAW device, the average thickness of the insulating layer may be in the range of 2 nm to 500 nm, and the resistivity of the insulating layer may be 10 ⁶ Ωcm or more. By setting the average layer thickness to 2 nm or more, short circuit between electrodes and corrosion of the electrodes can be suppressed. In addition, the average layer thickness is 500 nm.
The following can prevent the characteristics of the surface acoustic wave device from deteriorating. In addition, the resistivity of the insulating layer is set to 1
By the 0 ⁶ [Omega] cm or more, in particular suppress a short circuit between the electrodes.

[0016] In the above SAW device, the insulating layer comprises:
It may be made of metal nitride or metal oxide. According to the above configuration, not only the pyroelectric breakdown of the electrodes but also the corrosion of the electrodes and the short circuit between the electrodes can be prevented.

Further, in the method of manufacturing a surface acoustic wave device according to the present invention, (a) forming a first comb-like electrode and a second comb-like electrode on a piezoelectric substrate so as to face each other. And (b) before or after the step (a), atoms, molecules and clusters are formed on the surface of the substrate between the first comb-shaped electrode and the second comb-shaped electrode. Forming a doping region on the surface of the substrate by doping a substance (which may be an ion or a radical) in at least one form selected from the group consisting of: According to the above manufacturing method, it is possible to manufacture a surface acoustic wave device in which discharge between the IDT electrodes hardly occurs and which has a good surface acoustic wave propagation characteristic.

In the above manufacturing method, the substance may be doped into a region within 50 nm from the surface of the substrate. According to the above configuration, a doping region having a depth of 50 nm or less can be formed.

In the above method, it is preferable that the doping region has a lower resistance than the inside of the substrate. In this case, the sheet resistance of the doping region may be in the range of 10 ⁸ Ω / □ to 10 ¹⁵ Ω / □.

In the above manufacturing method, the substance may be doped in an ionized state.

In the above manufacturing method, the dose of the substance may be 1 × 10 ¹³ ions / cm ² to 1 × 10 ¹⁷ ions.
/ Cm ² . 1 × 10 dose
^By setting it to ¹³ ions / cm ² or more, a doping region having a preferable sheet resistance can be formed. Further, by setting the dose to 1 × 10 ¹⁷ ions / cm ² or less, deterioration of the characteristics of the SAW device can be particularly suppressed.

In the above production method, the substance may be 0.01%
It may be doped with an energy in the range of keV to 10 keV. According to the above configuration, the depth of the doping region can be reduced to 50 nm or less, and deterioration of the characteristics of the SAW device can be particularly suppressed.

In the above method, the substance may be a reducing gas, silane, nitrogen, oxygen, argon, silicon, arsenic,
At least one selected from boron, phosphorus, tin, indium, chromium, tantalum, molybdenum, germanium, and nickel may be ionized.

In the above manufacturing method, the substance may be doped by at least one method selected from an ion implantation method, an ion doping method, a plasma doping method, a laser doping method, and a gas phase doping method.
According to the above configuration, the doping layer can be formed easily and with good controllability.

In the above manufacturing method, after the step (a), (c) doping the surface of the first and second comb-toothed electrodes with an impurity to thereby form the first and second comb-shaped electrodes. The method may further include a step of forming an insulating layer on the surface of the toothed electrode. According to the above configuration, a short circuit between the electrodes due to the conductive particles can be prevented.

In the above manufacturing method, the impurity may be equal to the substance, and the step (c) may be performed simultaneously with the step (b). According to the above configuration, the doping region and the insulating layer can be formed by a single doping.

In the above manufacturing method, the impurity may be oxygen or nitrogen.

In the above manufacturing method, the average thickness of the insulating layer may be in a range of 2 nm to 500 nm, and the resistivity of the insulating layer may be 10 ⁶ Ωcm or more.

Further, the second surface acoustic wave device of the present invention comprises a substrate having piezoelectricity, a first comb-shaped electrode and a second comb-shaped electrode formed on the substrate so as to face each other. A surface acoustic wave device comprising:
A plurality of conductive regions separated from each other are provided on a surface between the first comb-like electrode and the second comb-like electrode, and the first comb-like electrode is interposed via the conductive region. A tunnel current flows between the second comb-shaped electrode and the second comb-shaped electrode.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 In Embodiment 1, an example of a SAW device of the present invention will be described. FIG. 1A is a plan view of the SAW device 10 according to the first embodiment. FIG. 1B is a cross-sectional view taken along line XX.

Referring to FIG. 1, SAW device 10 includes:
The substrate includes a substrate 11, a pair of IDT electrodes 12 formed on the substrate 11, and a reflector 13 formed on the substrate 11. The pair of IDT electrodes 12 includes a first IDT electrode 12a and a second IDT electrode 12b facing each other. The substrate 11 includes a first IDT electrode 12a and a second IDT electrode 1
2b, and a substrate surface 11s between the IDT electrode 12 and the reflector 13 is provided with a doping region 11a. Note that the SAW device 10 includes electric wiring and pad electrodes as necessary. Further, the SAW device of the present invention may include a plurality of sets of IDT electrodes on a substrate.

As the substrate 11, a substrate having piezoelectricity and pyroelectricity can be used. Specifically, for example,
A substrate made of LiTaO ₃ or LiNbO ₃ can be used. More specifically, a 64 ° Y-cut LiNbO ₃ substrate that propagates in the X direction, a 39 ° Y-cut LiNb
A TaO ₃ substrate can be used.

The doping region 11a of the substrate 11 is a region doped with at least one material selected from atoms, molecules, and clusters. Note that the substance to be doped may be in an ion or radical state. The doping region 11a has a lower resistance than the inside of the substrate. That is, the doping region 11a has a lower resistance than the substrate before doping. Doping region 11
The resistivity and the depth of “a” are set to values that can suppress discharge between the first IDT electrode 12a and the second IDT electrode 12b. Substrate surface 11 of doping region 11a
The depth from s is preferably 50 nm or less,
More preferably, it is 10 nm or less.

The sheet resistance of the substrate surface 11s between the first IDT electrode 12a and the second IDT electrode 12b, that is, the sheet resistance of the doping region 11a is 10 ⁸ Ω / □.
Is preferably ~10 ¹⁵ Ω / □ in the range of 10 ¹²
More preferably, the sheet resistance is in the range of Ω / □ to 10 ¹⁴ Ω / □ (this sheet resistance is a value measured in an electric field of 10 ⁵ V / cm or less. The same applies to the following.). By setting the sheet resistance to 10 ⁸ Ω / □ or more, it is possible to suppress deterioration in characteristics of the SAW device 10 such as insertion loss.

The discharge at the IDT electrode 12 depends on the temperature of the substrate 11 during the process or during use, the rate of temperature change,
It depends on the state of gas in contact with the surface of the substrate 11 and the state of light applied to the substrate 11. The discharge also depends on the distance between two adjacent electrodes, the shape of the electrode end, the electrode area, and the like. Therefore, the sheet resistance of the doping region 11a is adjusted in consideration of the above conditions. The sheet resistance can be adjusted by changing the type and amount of the doping substance.

For a LiTaO ₃ substrate or a LiNbO ₃ substrate,
Without doping, the average electric field is 10 ⁵ V /
cm or less, the sheet resistance is about 10 ¹⁵ Ω / □ or more. As described above, the sheet resistance on the surface of the doping region 11a is lower than that inside the substrate.

As a substance to be doped into the doping region 11a, for example, a reducing gas, silane, nitrogen,
At least one ion species selected from oxygen, argon, silicon, arsenic, boron, phosphorus, tin, indium, chromium, tantalum, molybdenum, germanium, and nickel can be used. As the reducing gas, for example, hydrogen, carbon monoxide, nitrogen monoxide and the like can be used. Among them, it is particularly preferable to use nitrogen as the ionic species because the propagation characteristics of the surface acoustic wave are hardly reduced.

When a substrate made of an oxide such as LiTaO ₃ or LiNbO ₃ is used, it is effective to use a reducing gas as an ionic species. It is considered that the use of a reducing gas as an ion species effectively forms oxygen vacancies on the surface of the oxide substrate. That is, it is considered that such oxygen vacancies act as donors and reduce the surface resistance of the doping region 11a.
When the substrate is a LiTaO ₃ substrate, doping with carbon or nitrogen is also effective. In this case, since tantalum carbide or tantalum nitride, which is a compound having higher conductivity than LiTaO ₃ , is formed, the surface resistance of the doping region 11a decreases.

Similarly, even when a neutral gas such as Ar or nitrogen, a relatively heavy gas, or a metal is used as the ion species, it is considered that lattice defects are formed on the substrate surface. And such lattice defects act as trap centers, donors, or acceptors,
It is considered that the surface resistance of the doping region 11a is reduced.

In the case of doping by accelerating ions, for example, doping can be performed at an acceleration energy in the range of 0.01 keV to 10 keV. The dose in this case may be an amount capable of realizing the above-described sheet resistance. For example, the dose may be 1 × 10 ¹³ ions / cm ² to 1 × 1.
A dose in the range of 0 ¹⁷ ions / cm ² can be used.

Although FIG. 1 schematically shows the IDT electrode 12, the IDT electrode 12 actually has more branches, for example, 100 to 500 branches. ID
The T electrode 12 is made of Al, an Al alloy, or another metal. As the Al alloy, for example, an Al-Cu alloy or an Al-Cu-Si alloy can be used. ID
T electrode 12 may be formed of a single metal film, or may be formed of a plurality of metal films. The first I
The shortest distance between the DT electrode 12a and the second IDT electrode 12b varies depending on the sound speed determined by the frequency and the substrate material, but is, for example, in the range of 0.01 μm to 100 μm.

The reflector 13 is formed to suppress the leakage of the surface acoustic wave from the IDT electrode 12. Reflector 13
Are formed so as to sandwich the IDT electrode 12. Reflector 1
For 3, the same material as that of the IDT electrode 12 can be used.

The SAW device 10 is used alone or in a state sealed in a package. The SAW device 10 is connected to the package by wire bond mounting, flip chip mounting, or the like.

In FIG. 1, the doping region 11a
Is formed only between adjacent electrodes (including IDT electrodes and reflectors) on the substrate 11. However, as shown in FIG. 6D, the doping region may be formed on the entire surface of the substrate on which the IDT electrode is formed.

The SAW device according to the present invention has an IDT
An insulating layer may be provided on the surface of the electrode. Such a SAW
FIG. 2 is a cross-sectional view illustrating an example of the device 20. S
In the AW device 20, only the IDT electrode and the reflector are S
Since the AW device 10 is different from the AW device 10, duplicate description will be omitted.

The SAW device 20 has an IDT electrode 22 and a reflector 23 formed on the substrate 11. ID
The T electrode 22 includes a first IDT electrode 22a and a second IT electrode 22a.
It is composed of a DT electrode 22b. The first IDT electrode 22a and the second IDT electrode 22b are respectively connected to the first IDT electrode 22b.
An insulating layer 24 is formed on the surfaces of the electrode 12a and the second IDT electrode 12b. That is, the IDT electrode 2
2 has an insulating layer 24 on its surface. In addition, reflector 2
3 has an insulating layer 25 on its surface. The resistivity of the insulating layers 24 and 25 is, for example, 10 ⁶ Ωcm or more. Insulating layers 24 and 25 are made of, for example, metal nitride or metal oxide. For example, for the insulating layers 24 and 25, aluminum nitride or aluminum oxide can be used. The thickness of the insulating layers 24 and 25 is
The film thickness is preferably 2 nm to 500 nm, and 2n
More preferably, it is from m to 10 nm. Insulating layer 24
Can be formed by doping the surface of an IDT electrode made of a metal with an impurity that forms an insulator with the metal. Similarly, the insulating layer 25 can be formed by doping a reflector made of metal with an impurity. Examples of the impurities include nitrogen and oxygen. The doping of the impurity can be performed by the method described in the second embodiment, similarly to the doping region 11a.

The SAW device according to the first embodiment can be manufactured by the manufacturing method described in the second embodiment.

In the SAW device according to the first embodiment, a doping region 11a is formed on the substrate surface 11s. Therefore, according to this SAW device, it is possible to prevent discharge from occurring between the electrodes during and after manufacturing. Further, since the doping region 11a is formed only on the surface of the substrate 11, the propagation characteristics of the surface acoustic wave are good.

Further, the SAW device according to the first embodiment
Unlike a conventional SAW device in which metal electrodes are connected between DT electrodes, there is no need to form a metal electrode for connection, so that miniaturization is possible.

Embodiment 2 In Embodiment 2, a method for manufacturing a SAW device according to the present invention will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description will be omitted.

The manufacturing method of the second embodiment includes the step of (a) forming a first IDT electrode and a second IDT electrode on a piezoelectric substrate so as to face each other. Hereinafter, this step may be referred to as step (a).

Further, in this manufacturing method, before or after the steps (b) and (a), the first IDT electrode and the second IDT
Forming a doping region on the substrate surface by doping the substrate surface between the electrodes with at least one form of a substance selected from atoms, molecules and clusters. Hereinafter, this step may be referred to as step (b). Note that in the step (b), the state of the substance to be doped may be an ion or a radical.

Hereinafter, an example of the manufacturing method of Embodiment 2 will be described with reference to FIG. In the drawings of the manufacturing process described below, only a part of the substrate is shown. In an actual manufacturing process, a plurality of elements are formed on one substrate and divided as necessary.

In this manufacturing method, first, a pair of IDT electrodes 12 and a reflector 13 are formed on a substrate 31, as shown in FIG. The first IDT electrode 12a and the second IDT electrode 12b are arranged to face each other. The substrate 31 is a substrate that becomes the substrate 11. The IDT electrode 12 can be formed by a photolithographic etching method or a lift-off method.

Thereafter, as shown in FIG. 3B, at least the first IDT electrode 12a and the second IDT electrode 12b
Are formed on the substrate surface 11s between the IDT electrode 12 and the reflector 13. The doping region 11a is formed by doping the substrate surface 11s with at least one form of a substance selected from atoms, molecules, and clusters (hereinafter, may be referred to as an additive substance). Thus, the substrate 11
Can be manufactured.

The additive substance is 50 nm from the substrate surface 11 s.
The doping is preferably performed to a depth within (more preferably, 10 nm). That is, the doping region 11
The depth a is preferably not more than 50 nm. The doping region 11a has a lower resistance than the inside of the substrate. The sheet resistance of the substrate surface 11s, that is, the doping region 11a is preferably in the range of 10 ⁸ Ω / □ to 10 ¹⁵ Ω / □, and is preferably in the range of 10 ¹² Ω / □ to 10 ¹⁴ Ω / □. Is more preferred.

The additional substance may be doped in an ionized state. In this case, the ion dose amount may be an amount that can realize the above-described sheet resistance.
1 × 10 ¹³ ions / cm ² to 1 × 10 ¹⁷ ions / c
m ² . When doping by accelerating ions, for example, 0.01 keV to 10 keV
Doping with the acceleration energy of In particular, when doping with nitrogen ions, 0.05 k
The doping is preferably performed at an acceleration energy of eV to 0.3 keV.

Examples of the additives include reducing gas, silane, nitrogen, oxygen, argon, silicon, arsenic, boron, phosphorus, tin, indium, Cr, Ta, Mo, and G.
A material obtained by ionizing at least one selected from e and Ni can be used. As the reducing gas,
For example, hydrogen, carbon monoxide, nitric oxide, or the like can be given. Further, a nitrogen radical or an oxygen radical can be used as an atom to be doped.

When a substrate made of an oxide such as LiTaO ₃ or LiNbO ₃ is used, it is effective to use a reducing gas as an ionic species. Similarly, it is also effective to use a neutral gas such as Ar or nitrogen, a gas having a relatively heavy mass, or a metal ion as the ion species.

The doping of the additive is performed by ion implantation,
It can be performed by at least one method selected from an ion doping method, an ion doping method, a plasma doping method, a laser doping method, and a gas phase doping method. The ion implantation method is a method of accelerating ions generated in plasma and further performing mass separation for doping. The ion doping method is a method of accelerating ions generated in plasma and performing doping without mass separation. The plasma doping method is a method in which a substrate is exposed to plasma to perform doping. The laser doping method is a method in which doping is performed by irradiating a substrate surface with a laser while exposing the substrate to a gas containing atoms to be doped. The gas phase doping method is a method in which a substrate is exposed to a gas containing atoms to be doped, and then heat treatment is performed to dope. Among the above methods, the plasma doping method is a low-temperature and low-energy process, so that a shallow doping region can be easily formed.

FIG. 4 schematically shows an example of a plasma doping apparatus. The doping device 40
The apparatus includes a chamber 41 and a substrate stage 42 arranged in the chamber 41. The chamber 41 has a gas supply pipe (not shown) and an exhaust pipe (not shown).
Are connected. Immediately above the substrate stage 42, a plasma 43 is formed. Substrate 44 on substrate stage 42
Is exposed to the plasma 43, and radicals and ions in the plasma 43 are doped into the substrate 44. In addition,
The plasma 43 is formed by an RF electrode (not shown) installed in the chamber 41.

FIG. 5 schematically shows an example of an ion implantation apparatus. The ion implanter 50 includes a chamber 51, a mass separator 52 connected to the chamber 51,
And a substrate stage 53. A gas supply pipe (not shown) and an exhaust pipe (not shown) are connected to the chamber 51. Further, an ion extraction electrode 54 is provided outside the chamber 51. The chamber 51, the mass separator 52, and the substrate stage 53 are arranged in a substantially vacuum. The substrate stage 53 is movable. On the substrate stage 53, a substrate 56 is arranged. In the chamber 51, a plasma 55 is formed. The ions generated in the plasma 55 are extracted out of the chamber by the ion extraction electrode 54, separated by the mass separator 52, and further accelerated or decelerated by the post-accelerator as necessary, and implanted into the substrate 56. . Note that the plasma 55 is formed by an RF electrode installed in the chamber 51.

When mounting the SAW device 10,
The mounting can be performed as shown in FIG. In the mounting process, first, after cutting the substrate 11 for each element,
It is fixed to the mounting board 33 using the resin 32. Then, wire bonding is performed using the bonding wire 34, and seam welding is performed in a nitrogen atmosphere. In this mounting process,
Although the substrate 11 is heated, since the substrate 11 includes the doping region 11a, discharge between the electrodes can be prevented.

In the above manufacturing method, when the step (b) is performed before the step (a), the doping region is etched by a process (eg, dry etching) for forming the IDT electrode 12. There is.
Therefore, in this case, the process conditions for forming the IDT electrode are limited. On the other hand, when the step (b) is performed after the step (a), there is no such limitation.

When the step (b) is performed after the step (a), there is an advantage that equipment and raw materials can be shared with apparatuses used in other steps. Devices used in other processes include a sputter cleaning device, a dry etching device, and a resist ashing device. The devices that can be shared include a chamber, an ionization device, an exhaust device, and a gas pipe. In particular, when ions are doped by a plasma doping method, the ions can be doped using a dry etching apparatus. In this case, the dry etching step and the plasma doping step can be continuously performed using the same chamber or another clustered chamber. As described above, by performing the step (b) after the step (a), a SAW device can be manufactured with high yield and reliability.

In the case of manufacturing the SAW device 20 described in the first embodiment, the manufacturing method of the present invention comprises, after the step (a), doping the surfaces of the IDT electrode 12 and the reflector 13 with impurities. Accordingly, a step of forming the insulating layers 24 and 25 may be included. Hereinafter, this step may be referred to as step (c).

The formation of the insulating layers 24 and 25 can be performed after removing the resist on the electrodes. Specifically, it can be performed before the step (b), simultaneously with the step (b), or after the step (b).

The impurity in the step (c) is changed to the step (b)
In the case where it is equal to the additive substance in the above, step (b) and step (c) can be performed simultaneously in one doping step. Specifically, when the IDT electrode 12 and the reflector 13 are made of a metal containing Al, the substrate 31, the IDT electrode 12 and the reflector 13 may be doped with nitrogen or oxygen. At this time, the insulating layer can be particularly effectively formed by doping nitrogen radicals or oxygen radicals.

According to the manufacturing method of the second embodiment, the ID
It is possible to manufacture a SAW device in which discharge between the T electrodes hardly occurs and which has a good surface acoustic wave propagation characteristic. Further, in the manufacturing method according to the second embodiment, since a discharge during the manufacturing process can be suppressed, a SAW device can be manufactured with high yield.

[0071]

The present invention will be described in more detail with reference to the following examples. Examples 1 to 4 show possible examples. Example 5 shows an example of actual implementation. Although the SAW device of the following embodiment does not have a reflector, a reflector may be formed.

(Embodiment 1) In Embodiment 1, the SA of the present invention is used.
An example of a method for manufacturing a W device will be described. FIG. 6 shows the manufacturing process of the first embodiment.

First, as shown in FIG.
A substrate 61 made of O ₃ is prepared and its surface is cleaned.
Then, as shown in FIG. 6B, a doping region 61 a having a surface sheet resistance in the range of 10 ⁸ Ω / □ to 10 ¹⁵ Ω / □ is formed on the substrate 61. Doping area 6
1a can be formed by plasma doping the substrate 61 with B ions. B ion doping is performed at an implantation energy of 700 eV and a dose of 1 × 10 ¹⁶ io.
It can be performed under the condition of ns / cm ² .

Next, as shown in FIG.
On top of this, a metal film 62 made of aluminum (film thickness 800n)
m) is formed by a sputtering method.

Next, as shown in FIG.
Unnecessary portions of 2 are removed to form IDT electrodes 63a and 63b. In forming the IDT electrode, first, a resist film (thickness: 1 μm) is formed on the metal film 62, and a predetermined pattern is formed by photolithography. Next, the metal film 6 is dry-etched using a chlorine-based gas.
Unnecessary parts of 2 are removed. Finally, the resist film is ashed by using oxygen plasma to complete the formation of the IDT electrode.

After that, the SAW device is mounted. Specifically, first, the substrate 61 is diced to divide each element. Next, the substrate 61 is die-bonded to the mounting substrate at a temperature of 180 ° C. using a silicon resin. next,
Wire bonding is performed on the IDT electrodes 63a and 63b. Finally, seam welding is performed in a nitrogen atmosphere.

As described above, in the manufacturing method of the first embodiment,
Ion implantation is performed before forming the IDT electrode. According to the SAW device obtained by the manufacturing method of Embodiment 1, discharge between the electrodes can be prevented.

The ion species is 0.1 vol% or less.
Nitrogen gas containing 5 vol% hydrogen, or 0.1 vol
Helium gas containing hydrogen of 5% to 5% by volume may be used. In this case, for example, implantation energy: 700e
Plasma doping can be performed under the conditions of V and a dose of 1 × 10 ¹⁶ ions / cm ² .

(Embodiment 2) In Embodiment 2, another example of a method for manufacturing a SAW device will be described. Example 2
7 is shown in FIG.

First, as shown in FIG.
A substrate 71 made of O ₃ is prepared, and its surface is cleaned.

Next, as shown in FIG. 7B, an IDT electrode 73 composed of IDT electrodes 73a and 73b is formed. These are formed as follows. First, a metal film made of aluminum (film thickness 200 n) is formed on a substrate 71.
m), and a resist film (thickness: 1 μm) having a predetermined pattern is formed on the metal film. Next, unnecessary portions of the metal film are removed by dry etching using a chlorine-based gas. Finally, the resist film is ashed by using oxygen plasma to complete the formation of the IDT electrode.

Next, as shown in FIG. 7C, an insulating layer 74 is formed on the surfaces of the IDT electrodes 73a and 73b.
At this time, the IDT electrode 73a and the IDT electrode 73 are simultaneously
b, a sheet resistance of 10 ⁸ Ω /
Doping region 71a in the range of □ -10 ¹⁵ Ω / □
To form Insulating layer 74 and doping region 71a
Is formed by plasma doping oxygen ions. Doping of oxygen ions is performed at an implantation energy of 5000 eV and a dose of 1 × 10 ¹⁷ ions / c.
under the conditions of m ^2.

Finally, in the same manner as in Embodiment 1,
The SAW device is mounted on the mounting board.

As described above, in the manufacturing method of the second embodiment,
After the IDT electrode is formed and the resist film is removed, ions are implanted. According to the SAW device obtained by the manufacturing method of the second embodiment, discharge between the electrodes can be prevented. In the manufacturing method according to the second embodiment, by forming the insulating layer on the surface of the electrode, a short circuit caused by the adhesion of the conductive particles during the process can be suppressed. Further, according to the SAW device obtained by the manufacturing method of the second embodiment, it is possible to suppress corrosion of the electrode and stress migration.

Embodiment 3 In Embodiment 3, another example of a method for manufacturing a SAW device will be described. Example 3
8 is shown in FIG.

First, as shown in FIG.
A substrate 81 made of O ₃ is prepared, and its surface is cleaned.

Next, as shown in FIG. 8B, an IDT electrode 83 including IDT electrodes 83a and 83b is formed. These are formed in the same manner as in the second embodiment.

Next, as shown in FIG. 8C, the substrate surface 81s between the IDT electrode 83a and the IDT electrode 83b.
Then, a doping region 81a having a sheet resistance in the range of 10 ⁸ Ω / □ to 10 ¹⁵ Ω / □ is formed. The doping region 81a can be formed by plasma doping the substrate 81 with B ions. B ion doping is performed at an implantation energy of 700 eV and a dose of 1 × 10
It is performed under the condition of ¹⁶ ions / cm ² . When B ions are implanted, B ions are also implanted into the IDT electrode.
It does not affect the electrical characteristics of the AW device.

Finally, by the same method as in the first embodiment,
The SAW device is mounted on the mounting board.

As described above, in the manufacturing method of the third embodiment,
After the IDT electrode is formed, ions are implanted. According to the SAW device obtained by the manufacturing method of the third embodiment, discharge between the electrodes can be prevented.

The ionic species is 0.1 vol% or less.
Nitrogen gas containing 5 vol% hydrogen, or 0.1 vol
Helium gas containing hydrogen of 5% to 5% by volume may be used. In this case, for example, implantation energy: 700e
Plasma doping can be performed under the conditions of V and a dose of 1 × 10 ¹⁶ ions / cm ² .

Fourth Embodiment In a fourth embodiment, another example of a method for manufacturing a SAW device will be described. Example 4
9 is shown in FIG.

First, as shown in FIG.
A substrate 91 made of O ₃ is prepared and its surface is cleaned.

Next, as shown in FIG. 9B, an IDT electrode 93 including IDT electrodes 93a and 93b is formed. These are formed in the same manner as in the second embodiment.

Next, as shown in FIG. 9C, an insulating layer 94 is formed on the surfaces of the IDT electrodes 93a and 93b.
At this time, the IDT electrode 93a and the IDT electrode 93 are simultaneously
A doping region 91a is formed on the substrate surface 91s between the region b and the region b. Insulating layer 94 and doping region 91a
Is formed by plasma doping oxygen ions. Doping of oxygen ions is performed at an implantation energy of 5000 eV and a dose of 1 × 10 ¹⁷ ions / c.
under the conditions of m ^2.

Next, as shown in FIG. 9D, the doping region 91a is plasma-doped with B ions to form a doping region 91b having a lower resistance than the doping region 91a.
To form The sheet resistance of the doping region 91b is 10
It is in the range of ⁸ Ω / □ to 10 ¹⁵ Ω / □. B ion doping is performed at an implantation energy of 700 eV and a dose of:
It can be performed under the condition of 1 × 10 ¹⁶ ions / cm ² .

Finally, in the same manner as in Example 1,
The SAW device is mounted on a mounting board.

According to the manufacturing method of the fourth embodiment, the same effect as that of the manufacturing method of the second embodiment can be obtained. Further, in the manufacturing method according to the fourth embodiment, the control of the sheet resistance of the doping region 91b becomes easy.

(Embodiment 5) In Embodiment 5, the SA of the present invention is used.
An example in which a SAW device is actually manufactured by a W device manufacturing method will be described. FIG. 10 shows a manufacturing process of the manufacturing method of the fifth embodiment.

First, as shown in FIG.
A substrate 101 made of aO ₃ was prepared, and the surface was cleaned.

Next, as shown in FIG.
IDT electrode 103 composed of electrodes 103a and 103b
Was formed. These were formed as follows. First, an Al-Cu alloy (Al: Cu
= 99.5: 0.5) (film thickness 200n)
m) was formed, and a resist film (thickness: 1.5 μm) having a predetermined pattern was formed on the metal film. At this time, a positive resist was used for the resist film. Next, BCl ₃ and C
to remove unnecessary portions of the metal film by dry etching using a mixed gas of l _2. Finally, the resist film was ashed by using oxygen plasma to form an IDT electrode.

Next, as shown in FIG.
Substrate surface 1 between electrode 103a and IDT electrode 103b
01s, a doping region 101a was formed. The doping region 101a was formed by doping nitrogen ions by an ICP plasma doping method. At this time, three types of SAW devices were formed under different doping conditions. For these three types of SAW devices, a heating test and evaluation of RF characteristics were performed. As a comparative example, SAW without nitrogen ion doping was used.
A similar test was performed on the device. Table 1 shows the doping conditions and test results for the above samples.
Shown in

[0103]

[Table 1]

The heating test was performed for each sample.
00 pieces were heated to 50 ° C. on a hot plate, and the number of the devices destroyed by the discharge was measured. The numbers in Table 1 are the number of destroyed devices out of 100 devices.
For the RF characteristics, the center frequency and the band were measured using a network analyzer.

As is evident from Table 1, pyroelectric breakdown due to heating was suppressed in Samples 1 to 3 of the present invention as compared with the comparative sample. In sample 3 among samples 1 to 3, there was no loss.

(Embodiment 6) Two examples of another SAW device of the present invention for preventing pyroelectric breakdown will be described below. FIG. 11A is a cross-sectional view of the first SAW device 200. Also, the second SAW device 2
FIG. 11B shows a cross-sectional view of No. 10.

The SAW device 200 includes a substrate 201 made of a piezoelectric material and an IDT electrode 202 formed on the substrate 201. The IDT electrode 202 includes a pair of IDT electrodes 202a and 202b facing each other. The IDT electrode 202 is the same as the IDT electrode 12 described in the first embodiment.

In the SAW device 200, at least I
A plurality of dot-shaped metals 203 are formed on the substrate surface between the DT electrode 202a and the IDT electrode 202b.
The metal 203 is arranged at such a distance that a tunnel current flows between adjacent metals 203. Specifically, the metal 203 is formed on the substrate surface at a density of 10 pieces / μm ² or more. The metal 203 can be formed, for example, by performing a sensitizing process and an activating process, which are pre-processes of electroless plating. Specifically, as the sensitizing treatment, a treatment aqueous solution (SnCl ₂ :
The substrate 201 is treated with 10 g / l, HCl: 40 ml / l, 323K). Further, as an activation treatment, a treatment aqueous solution (PdCl ₂ : 0.2 g / l, HC
l: 20 ml / l, 323 K). In this way, a dot-shaped metal made of palladium can be formed.

In the SAW device 200, when a high voltage is applied between the electrodes, a tunnel current flows through the metal 203, so that discharge between the electrodes can be prevented. Therefore, according to the SAW device 200, discharge breakdown during and after the manufacturing process can be prevented. Further, since the metal 203 is insulated, there is no adverse effect on the characteristics of the device. Further, the SAW device 200 is not affected by environmental changes such as repetitive stress and has high reliability.

The dot-shaped metal 203 can be formed by another method, for example, by utilizing the initial state (metal in an island) in metal deposition.

The SAW device 210 includes a substrate 211 made of a piezoelectric material and an IDT electrode 212 formed on the substrate 211. The IDT electrode 212 is the same as that of the first embodiment.
This is the same as the IDT electrode 12 described above.

The substrate 211 has a doping region 211a formed in a stripe shape. Note that the doping region may be formed in a mesh shape. The doping region 211a is formed by doping a substrate with at least one form of a substance selected from atoms, molecules, and clusters.

In the SAW device 210, when a high voltage is applied between the electrodes, a tunnel current flows through the doping region 211a, so that discharge between the electrodes can be prevented. Therefore, according to the SAW device 210, the same effect as the SAW device 200 can be obtained. Further, in the SAW device 210, since the doping region 211a is formed in a stripe shape, the DC resistance is low and the high-frequency resistance is high. Therefore, the SAW device 2
According to No. 10, discharge between the electrodes can be prevented, and the same characteristics as those of a normal SAW device can be obtained.

Although the embodiments of the present invention have been described above by way of examples, the present invention is not limited to the above embodiments, but can be applied to other embodiments based on the technical idea of the present invention. .

[0115]

As described above, according to the SAW device and the method for manufacturing the SAW device of the present invention, the ID
Discharge between the T electrodes hardly occurs, and a surface acoustic wave device having good SAW propagation characteristics can be easily obtained. INDUSTRIAL APPLICABILITY The present invention is useful for various SAW devices such as a ladder type or traveling wave type SAW filter and a SAW resonator.

[Brief description of the drawings]

1A and 1B are a plan view and a cross-sectional view of an example of a SAW device according to the present invention.

FIG. 2 is a cross-sectional view showing another example of the SAW device of the present invention.

FIG. 3 is a process chart showing an example of a method for manufacturing a SAW device of the present invention.

FIG. 4 is a diagram schematically illustrating an example of a plasma doping apparatus used in the method for manufacturing a SAW device according to the present invention.

FIG. 5 is a diagram schematically illustrating an example of an ion implantation apparatus used in the method for manufacturing a SAW device according to the present invention.

FIG. 6 is a process chart showing another example of the method for manufacturing a SAW device of the present invention.

FIG. 7 is a process chart showing another example of the method for manufacturing a SAW device of the present invention.

FIG. 8 is a process chart showing another example of the method for manufacturing a SAW device of the present invention.

FIG. 9 is a process chart showing another example of the method for manufacturing a SAW device of the present invention.

FIG. 10 is a process chart showing another example of the method for manufacturing a SAW device of the present invention.

FIG. 11 shows another SAW device of the present invention.
(A) is sectional drawing which shows an example and (B) another example.

FIG. 12 is a plan view showing an example of a conventional SAW device.

[Explanation of symbols]

10, 20 Surface acoustic wave device (SAW device) 11, 61, 71, 81, 91, 101 Substrate 11a, 61a, 71a, 81a, 91a, 91b, 1
01a Doping region 11s, 71s, 81s, 91s, 101s Substrate surface 12, 22, 63, 73, 83, 93, 103 Comb-shaped electrode (IDT electrode) 12a, 22a, 63a, 73a, 83a, 93a, 1
03a First comb-shaped electrode 12b, 22b, 63b, 73b, 83b, 93b, 1
03b Second comb-shaped electrode 13, 23 Reflector 24, 25, 74, 94 Insulating layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H03H 9/145 H01L 41/18 101A 41/22 Z (72) Inventor Tetsuhisa Yoshida 1006 Kadoma Kadoma, Kadoma, Osaka Address Matsushita Electric Industrial Co., Ltd. (72) Inventor Kentaro Seto 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Kozo Murakami 1006 Kadoma, Kazuma, Kadoma, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Kunihiro Fujii 1006 Kadoma, Kazuma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 5J097 AA01 AA32 GG03 GG04 HA03

Claims (22)

[Claims] 1. A surface acoustic wave device comprising: a substrate having piezoelectricity; a first comb-shaped electrode and a second comb-shaped electrode formed on the substrate so as to face each other; A substrate having a doping region on a surface between the first comb-shaped electrode and the second comb-shaped electrode, doped with at least one material selected from atoms, molecules, and clusters; Surface wave device. 2. The doping region has a depth of 50 nm.
The surface acoustic wave device according to claim 1, wherein: 3. The surface acoustic wave device according to claim 1, wherein the doping region has a lower resistance than inside the substrate. 4. The sheet resistance of the doping region is 1
^{0 8 Ω / □ ~10 15 Ω} / □ surface acoustic wave device according to claim 3 in the range of. 5. The method according to claim 1, wherein the substance is a reducing gas, silane, nitrogen, oxygen, argon, silicon, arsenic, boron, phosphorus,
The surface acoustic wave device according to claim 1, wherein at least one selected from tin, indium, chromium, tantalum, molybdenum, germanium, and nickel is ionized. 6. The surface acoustic wave device according to claim 1, wherein the first and second comb-shaped electrodes have an insulating layer on a surface. 7. An average thickness of the insulating layer is 2 nm to 50 nm.
0 nm, and the resistivity of the insulating layer is 10 ⁶ Ω.
7. The surface acoustic wave device according to claim 6, wherein 8. The surface acoustic wave device according to claim 6, wherein the insulating layer is made of a metal nitride or a metal oxide. 9. A method for manufacturing a surface acoustic wave device, comprising: (a) forming a first comb-shaped electrode and a second comb-shaped electrode on a substrate having piezoelectricity so as to face each other. And (b) before or after the step (a), on the surface of the substrate between the first comb-shaped electrode and the second comb-shaped electrode, from atoms, molecules and clusters. By doping at least one form of the substance selected,
Forming a doping region on the surface of the substrate. 10. The method according to claim 1, wherein the substance is located 50 meters from the surface of the substrate.
The method for manufacturing a surface acoustic wave device according to claim 9, wherein a region within nm is doped. 11. The method according to claim 9, wherein the doping region has a lower resistance than the inside of the substrate. 12. The sheet resistance of the doping region is:
12. The resistance within the range of 10 ⁸ Ω / □ to 10 ¹⁵ Ω / □.
3. The method for manufacturing a surface acoustic wave device according to 1. 13. The method for manufacturing a surface acoustic wave device according to claim 9, wherein the substance is doped in an ionized state. 14. A dose of the substance is 1 × 10 ¹³ i.
The method for manufacturing a surface acoustic wave device according to claim 13, wherein the surface acoustic wave device is in a range of ons / cm ² to 1 × 10 ¹⁷ ions / cm ² . 15. The method according to claim 11, wherein the substance is 0.01 keV to 10 kV.
2. Doping with an energy in the range of eV.
4. The method for manufacturing a surface acoustic wave device according to 3. 16. The method according to claim 16, wherein the substance is a reducing gas, silane, nitrogen, oxygen, argon, silicon, arsenic, boron, phosphorus,
The method for manufacturing a surface acoustic wave device according to claim 13, wherein at least one selected from tin, indium, chromium, tantalum, molybdenum, germanium, and nickel is ionized. 17. The surface acoustic wave according to claim 9, wherein the substance is doped by at least one method selected from an ion implantation method, an ion doping method, a plasma doping method, a laser doping method, and a gas phase doping method. Device manufacturing method. 18. After the step (a), (c) doping impurities on the surfaces of the first and second comb-tooth electrodes to thereby form the first and second comb-tooth electrodes. The method for manufacturing a surface acoustic wave device according to claim 9, further comprising a step of forming an insulating layer on the surface of the surface acoustic wave device. 19. The method of manufacturing a surface acoustic wave device according to claim 18, wherein the impurity is equal to the substance, and the step (c) is performed simultaneously with the step (b). 20. The method according to claim 18, wherein the impurity is oxygen or nitrogen. 21. An insulating layer having an average thickness of 2 nm to 5 nm.
00 nm, and the resistivity of the insulating layer is 10 ⁶
The method for manufacturing a surface acoustic wave device according to claim 18, wherein the surface acoustic wave device is not less than Ωcm. 22. A substrate having a piezoelectric property, a first comb-shaped electrode formed on the substrate, and a second comb-shaped electrode formed on the substrate.
A surface acoustic wave device comprising: a plurality of conductive electrodes separated from each other on a surface between the first comb-shaped electrode and the second comb-shaped electrode; A surface acoustic wave device comprising a conductive region, wherein a tunnel current flows between the first comb-shaped electrode and the second comb-shaped electrode via the conductive region.