JP3417502B2 - Manufacturing method of surface acoustic wave device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an Al surface acoustic wave device.
The manufacturing method for preventing the corrosion of the Cu alloy electrode
To do.

[0002]

2. Description of the Related Art In recent years, as the frequency of surface acoustic wave devices has increased, finer electrode processing has been required, and dry etching has been used instead of wet etching for electrode processing. Further, in order to obtain a sufficient power withstanding life of the surface acoustic wave device, Al-
An alloy such as Cu is indispensable.

However, since chlorine-based gas is used for etching Al and Al alloy by dry etching, corrosion of electrodes after etching is a problem. A similar problem occurs when Al wiring of a semiconductor device is used. However, an Al alloy on a LiNbO ₃ or LiTaO ₃ substrate used in a surface acoustic wave device is more corroded than an SiO ₂ substrate used in a semiconductor device. Likely to happen.

In order to solve the above problems, in the field of semiconductors, as a method for preventing the corrosion, a method of substituting chlorine by plasma treatment with a fluorine-based gas after etching is disclosed in JP-A-5-36691, and after etching. A method of washing with an acid is disclosed in JP-A-2-148728, and a method of washing with an alkali after etching is disclosed in JP-A-3-14728.
No. 5728, a method of cleaning with an organic solvent after etching is disclosed in JP-A-3-180040, a method of cleaning with pure water after etching is disclosed in JP-A-3-166724, and a method of heating after etching is disclosed. Japanese Patent Laid-Open No. 3-2
No. 80535 and a method of supplying an inert gas heated after etching are disclosed in JP-A-63-53268.

However, these methods do not sufficiently prevent corrosion. Particularly, in the method of washing with water, Al
With Cu alloys, corrosion that newly occurs during washing with water poses a problem. This is because there is precipitation of CuAl ₂ phase in the Al-Cu alloy film, and when this CuAl ₂ phase raises the potential and dissolved oxygen exists in pure water, it acts as an oxidant and the condition of corrosion is satisfied. Because of the occurrence of corrosion. Therefore, a method of deoxidizing pure water to be washed with water to remove dissolved oxygen, which is one of the causes of corrosion, is an effective means for preventing corrosion.

As a typical prior art of the present invention, Japanese Patent Laid-Open No. 4-51521 (hereinafter referred to as Prior Art 1) will be described.

In FIG. 12, after being etched by a RIE (reactive ion etching) device 214, the heating device 215 heats the surface of the substrate with hot air, and then a water washing device 216 performs a water washing process.

In this water washing device 216, first, in FIG. 13, the ultrapure water introduced from the ultrapure water introducing pipe 237 is used for deoxidizing treatment together with the hydrogen gas introduced from the hydrogen gas introducing pipe 236. It is guided to a catalyst resin packed tower 240 filled with the catalyst 239.

Since oxygen in the ultrapure water reacts with hydrogen due to the catalytic action to become water as shown in the following formula,
Deoxidation treatment can be performed.

H ₂ + 1 / 2O ₂ → H ₂ O This reaction proceeds quantitatively, and by adding 1 ppm of H ₂ to H ₂ O containing 8 ppm of dissolved oxygen, almost all of the dissolved oxygen is removed. be able to. With this equipment, 20 pp of O ₂ can be stored even in low temperature water that is difficult to process mechanically and chemically.
It can be less than m, and the operation of the device is simple.

The ultrapure water 238 deoxidized by the catalyst resin packed tower 240 in this manner is introduced into the water washing container 232 through the introduction pipe 235, and is suction-rotated by the spinner 234 to wash the substrate 233 to be treated with water. .

In the above deoxidation treatment method, pure water and hydrogen are mixed, and dissolved oxygen in pure water is reacted with hydrogen using a catalyst to form water, whereby dissolved oxygen in pure water is removed. Since it is reduced and is washed with deoxidized water in this way, it is possible to form a good wiring pattern without being oxidized during the washing.

[0013]

However, in the electrode processing of the surface acoustic wave device, an Al-Cu alloy is used as an electrode material, and when this is dry-etched with a chlorine-based gas, after the etching, the Al-Cu alloy is used. Sufficient measures have not been taken against the corrosion that occurs and the corrosion that newly occurs when washing with water after etching.

Further, in the method of the prior art example 1, since hydrogen is used, it is necessary to handle it with care, and also a catalyst is used, which requires a large apparatus and is expensive. Furthermore, since the dissolved oxygen can be reduced to only about 20 ppm by the method of Prior Art 1, deoxidation treatment for corrosion resistance is insufficient.

In order to solve the above problems, the present invention is based on Al-
An object of the present invention is to provide a water washing method for preventing corrosion in the atmosphere after performing ashing in succession to etching as a method for preventing corrosion when performing a chlorine-based gas plasma etching process on a Cu alloy electrode. To do. Another object of the present invention is to provide a water washing method that prevents corrosion that newly occurs during water washing.

[0016]

A method of manufacturing a surface acoustic wave device according to the present invention comprises a step of forming an Al--Cu alloy electrode of a surface acoustic wave device by plasma etching with a chlorine-based gas, and a step of resist ashing. And a step of cleaning the substrate with deoxidized ultrapure water after the resist ashing, the method of manufacturing a surface acoustic wave device.

Further, the method for manufacturing a surface acoustic wave device is characterized in that the ultrapure water is deoxidized by N ₂ gas bubbling.

Further, the method of manufacturing a surface acoustic wave device is characterized in that ultrapure water is deoxidized by CO ₂ gas bubbling.

Further, a step of forming an Al--Cu alloy electrode of the surface acoustic wave device by plasma etching of chlorine-based gas, a step of resist ashing, and a step of removing the substrate from the high vacuum chamber to the atmosphere after the resist ashing. A method of manufacturing a surface acoustic wave device, comprising: a step of cleaning with deoxygenated ultrapure water. 1) after removing the substrate from the high vacuum chamber into the atmosphere
The method for producing a surface acoustic wave device is characterized in that the washing is performed in the next washing step within a minute.

Further, a step of forming an Al--Cu alloy electrode of the surface acoustic wave device by plasma etching of chlorine-based gas, a step of resist ashing, and taking out the substrate from the high vacuum chamber into the atmosphere after the resist ashing. In the method of manufacturing a surface acoustic wave device, which comprises a step of cleaning with deoxygenated ultrapure water, the atmosphere in the atmosphere until the substrate is taken out of the high vacuum chamber into the atmosphere and cleaned in the cleaning step is , Relative humidity 30
% Or less, is a method of manufacturing a surface acoustic wave device.

Further, in the method of manufacturing the surface acoustic wave device, the atmosphere until the substrate is taken out from the high vacuum chamber and cleaned in the cleaning step is a dry N 2 atmosphere.

Further, the Al--Cu alloy electrode is 0.5
A method of manufacturing a surface acoustic wave device comprising an Al-Cu alloy electrode containing Cu to 2.0 wt%.

According to the present invention, an electrode is formed by etching and ashing, and then N ₂ gas or CO ₂ gas is bubbled to remove dissolved oxygen and rinsed with deoxygenated ultrapure water. Rinse with deoxygenated ultrapure water within the incubation period until corrosion of the Al-Cu alloy electrode is generated.
The surface acoustic wave according to the present invention is obtained by rinsing with deoxygenated ultrapure water in an atmosphere having a long incubation period until the occurrence of corrosion and a relative humidity of 30% or less or in a dry N ₂ atmosphere. The above object of the method for manufacturing the device is achieved.

[0024]

[Function] Corrosion that occurs when the Al alloy film is plasma-etched with chlorine gas and washed with pure water is pitting corrosion in electrochemical theory, and pitting corrosion occurs only when the following four conditions are met. To do.

Presence of passivation film Local breakdown of passivation film Increase in potential Existence of oxidizing agent If dissolved oxygen exists in the ultrapure water used for washing with water, this dissolved oxygen acts as an oxidizing agent to deprive Al valence electrons. Therefore, pitting corrosion occurs in the next reaction.

[0026] _{H 2 O + O 2 + e} - → OH - ··· 1 Al → Al 3+ + e - In accordance with claim 1, 2, 3 ... 2 invention, ultrapure water By removing the dissolved oxygen, it is possible to remove one of the pitting corrosion conditions, the movement of e ^{− in} the above equations 1 and 2 is prevented, and the corrosion (pitting corrosion) at the time of washing with water is prevented.

If the Al-Cu alloy electrode is plasma-etched with a Cl-based gas and then taken out into the atmosphere, moisture in the atmosphere acts and corrosion occurs.

[0028] _{Cl 2 + H 2 O → Cl} - + H + + O ··· 3 Al + H 2 O + O 2 → Al 3+ + OH - ··· 4 Al 3+ + Cl - → AlCl 3 · .. 5 A certain predetermined reaction time (latency period) is required for the corrosion reaction of the above equations 3, 4, and 5 to occur. According to the fourth aspect of the present invention, by washing with deoxygenated ultrapure water to remove Cl and O within this incubation period, it is possible to remove the pitting corrosion condition and prevent corrosion. To be done.

According to the fifth and sixth aspects of the present invention, after etching and ashing, washing with deoxygenated ultrapure water is performed in the atmosphere having a relative humidity of 30% or less or in a dry N ₂ atmosphere to wash with water. , The reaction of equation 5 is suppressed, and one of the pitting conditions is removed, and corrosion is prevented.

According to the seventh aspect of the present invention, by setting the mass ratio of Cu in the Al--Cu alloy electrode to 0.5 to 2.0 wt%, the power withstanding life of the surface acoustic wave device is extended and the reliability is improved. Can be increased.

[0031]

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

Embodiment 1 FIGS. 1 (a) to 1 (d) show sectional views in order of steps in an embodiment of the present invention. In this embodiment, 11 is a piezoelectric single crystal substrate, 1
2 is an Al-Cu electrode layer, and 13 is a photoresist.

On the piezoelectric single crystal substrate (LiNbO ₃ substrate or LiTaO ₃ substrate) 11, for example, a sputtered film of Al-0.5 wt% Cu alloy having a thickness of 0.15 μm is formed (FIG. 1A). Next, by photolithography,
For example, a resist pattern of a surface acoustic wave filter is formed (FIG. 1 (b)), and thereafter, by using magnetron RIE (reactive ion etching) using a mixed gas of Cl ₂ and BCl ₃ , Al-using the resist pattern as a mask.
The 0.5 wt% Cu alloy film is plasma-etched to form an electrode of the surface acoustic wave filter (FIG. 1 (c)).

At this time, it has been confirmed by SEM (scanning electron microscope) that deposits are present on the substrate around the Al--Cu alloy electrode. Further, it has been confirmed by SEM that these deposits increase as the over-etching time increases, and that they are resist residues due to etching.

After that, the substrate is transferred to another chamber while maintaining a high vacuum, and the resist pattern is ashed and removed by microwave downflow plasma using a mixed gas of O ₂ and CF ₄ (FIG. 1 (d)). However, it has been confirmed by SEM that the ashing does not remove the deposits as etching residues. EPMA indicates that the deposit contains F, C, O and Cl.
(Electron probe X-ray micro analyzer).

Next, after taking out the LiNbO ₃ substrate to which the deposit containing Cl, F, C and O adheres to the atmosphere,
The substrate is cleaned in the substrate cleaning tank shown in FIG. 2 within 1 minute.

The structure of the substrate cleaning tank and the results of the practice of the present invention will be described below. FIG. 2 shows the structure of the substrate cleaning tank in the embodiment of the present invention. In this embodiment, 21 is a washing tank, 22 is a synthetic resin porous plate having a large number of holes, and 23
Is a substrate holder, and 24 is a substrate. The cleaning tank 21 has, for example, a rectangular parallelepiped shape with a volume of 5 liters, and a bottom portion of the cleaning tank 21 is provided with a perforated plate 22 provided with a large number of small holes having a diameter of about 1 mm on a resin plate, for example, about 5 mm above the bottom of the cleaning tank 21. There is. The cleaning tank 21 is filled with ultrapure water and the pressure is about 0.5.
N ₂ gas of kg / cm ² is introduced between the cleaning tank 21 and the perforated plate 22, the N ₂ gas is blown into the ultrapure water through the holes of the perforated plate 22, and the ultrapure water is bubbled for 3 minutes or more. . Thereby, as shown below, dissolved oxygen in the ultrapure water is removed.

FIG. 3 is a correlation diagram between the N ₂ gas bubbling time and the amount of dissolved oxygen in ultrapure water. FIG. 3 shows the correlation between the N ₂ gas bubbling time and the amount of dissolved oxygen in the ultrapure water when the ultrapure water with which the cleaning tank 21 is filled is made to be running water or accumulated water. The N ₂ gas pressure used here is 0.5 kg / cm ² which is the same as that described in FIG. In the case of running water, ultrapure water is introduced from the upper part of the cleaning tank 21 and overflowed. As a result, when the flow rate of ultrapure water was other than high (B in FIG. 3), the amount of dissolved oxygen was 0.2 to 0.3 ppm or less in about 3 minutes of N ₂ gas bubbling time.

The ultrapure water cleaning tank 21 from which the dissolved oxygen has been removed is used as the first tank, and a similar tank is separately provided as the second tank. The LiNbO ₃ taken out into the atmosphere
The substrate is placed in the first tank of the cleaning tank 21 for a short time, for example, 3
After soaking for 0 second to wash, continue to the second tank with, for example, 1
By soaking for more than a minute and cleaning, Cl, F,
SE removes the deposits on the substrate containing C and O.
Confirmed by M.

FIG. 4 is a diagram showing a corrosion occurrence state during the cleaning time. In FIG. 4, when a substrate is cleaned using conventional ultrapure water containing dissolved oxygen and ultrapure water from which dissolved oxygen has been removed by N ₂ gas bubbling according to the present invention, corrosion of the Al—Cu alloy electrode occurs depending on the cleaning time. Indicates the status.
When the substrate is cleaned with conventional ultrapure water containing a large amount of dissolved oxygen, if the substrate is immersed in ultrapure water for 1 minute or longer, Al-0.5
Corrosion occurred in the wt% Cu electrode, while dissolved oxygen was changed from 0.2 to 0.2 by the N ₂ gas bubbling according to the present invention.
When the substrate was washed with ultrapure water removed to 3 ppm or less, no corrosion occurred on the electrode even if the substrate was immersed in ultrapure water for 10 minutes or longer.

FIG. 5 is an SEM photograph of the electrode after cleaning.
FIG. 5 shows the corrosion occurrence state of each electrode when washed with pure water and N ₂ gas bubbling pure water for 10 minutes each. Here, when cleaning is performed with pure water containing dissolved oxygen without N ₂ bath bubbling (FIG. 5A), it can be clearly confirmed that the electrodes are corroded. Further, it can be confirmed that the pure water bubbling with N ₂ gas (FIG. 5B) does not cause corrosion.

Here, in the case of cleaning with pure water (FIG. 5A), the electrode is corroded because the passivation film destruction anion Cl ⁻ caused by the etching gas Cl ₂ causes the passivation film on the electrode pattern side ( Al ₂ O ₃ ) is locally destroyed,
When immersed in pure water containing dissolved oxygen (the amount of dissolved oxygen in the pure water used in the experiment was 6.8 mg / l), this dissolved oxygen acts as an oxidizer and the pitting corrosion condition is satisfied, so that the pores in the passivated film breakage part are filled. This is due to the progress of food and corrosion.

Further, FIG. 6 is a correlation diagram between the oxygen content in the bubbling gas and the number of corrosion occurrences. In FIG. 6, the O ₂ content in the bubbling gas N ₂ and Al-0.5 wt when the substrate was cleaned with pure water bubbling with these gases
The correlation with the number of corrosion occurrences of the% Cu alloy electrode is shown. Bubbling with each gas was performed for 5 minutes, and substrate cleaning was performed for 5 minutes. The number of corrosions generated was counted using an optical microscope. The smaller the oxygen content, the smaller the number of corrosion occurrences. Corrosion did not occur at all in the gas having an oxygen content of 0%. Also in this case, Al-
It is shown that the corrosion of the Cu electrode is pitting corrosion, and the corrosion can be prevented by removing the oxidizing agent (oxygen) which is one factor necessary for the occurrence of pitting corrosion.

The Al-0.5 wt% Cu electrode, which has been washed with the N ₂ gas bubbling ultrapure water according to the present invention and then dried by an N ₂ blow dryer, is not corroded even if left in the atmosphere for 1 month or more. Did not occur. This is because by washing with water, the deposits on the substrate containing a large amount of Cl and O, which act on the moisture in the atmosphere and cause corrosion, are removed, and at the same time, Cl and O are also removed, so that corrosion occurs. It depends on what you do not do.

As described above, the method of cleaning with ultrapure water from which dissolved oxygen has been removed by bubbling with N ₂ gas is Al--C.
A sufficient effect was obtained on the corrosion resistance of the u alloy electrode.

It has been confirmed that the same effect can be obtained when CO ₂ gas is used instead of N ₂ gas.

FIG. 7 shows the type of bubbling gas and the corrosion resistance. FIG. 7 shows electrode corrosion states when N ₂ gas bubbling and CO ₂ gas bubbling were used to remove dissolved oxygen in ultrapure water and when ultrapure water that did not remove dissolved oxygen was used.

In the case of CO ₂ gas bubbling, the dissolved oxygen content is 0.2 to 0.3 ppm as in the case of N ₂ gas bubbling.
No corrosion occurred on the electrodes when CO
_In the case of ₂ gas bubbling, the dissolved oxygen in the ultrapure water is 0.
No corrosion was observed on the electrode even at 8 to 1.2 ppm.
This is because when the CO ₂ gas is dissolved in ultrapure water, carbonic acid is generated, the pH is lowered, the pH enters the general corrosion area of Al, and the corrosion of the electrode is not confirmed. The electrode corrosion that can be confirmed is pitting corrosion, and pitting corrosion does not occur in the general corrosion area of Al.

In this embodiment, the pH of ultrapure water in the case of CO ₂ is
3.8 to 4.3, and the general corrosion area of Al is pH
Since the pH is about 4 or less and the pH is about 8 or more, the CO ₂ of this example is considered to be within the general corrosion region.

When dissolved oxygen is removed by CO ₂ gas bubbling, no observable corrosion (pitting corrosion) occurs in the electrode, but the entire electrode is uniformly corroded and the electrode remains corroded.

However, since the overall corrosion rate of the electrode was small, CO ₂ gas was also effective as a dissolved oxygen removing gas.

In addition to N ₂ gas and CO ₂ gas, there are Ar, H _{2 and the} like as dissolved oxygen removing gases, but none of them is practical in terms of price, efficiency and safety.

Example 2 The same LiNbO ₃ substrate as in Example 1 and the same Al-0.5 were used.
After forming the surface acoustic wave filter electrode of the wt% Cu alloy by the same etching / ashing, the substrate was taken out of the high vacuum chamber into the atmosphere, and after 2 minutes or more, N ₂ was removed in the same manner as in Example 1. When washed with ultrapure water from which dissolved oxygen was removed by gas bubbling, Al-Cu
Some corrosion was observed on the alloy electrode.

This is one in which the substrate was taken out from the high vacuum chamber, and was corroded in the atmosphere until it was washed with ultrapure water from which dissolved oxygen was removed by bubbling with N ₂ gas, that is, the corrosion generation latent period or more. It can be confirmed that it was corroded in the atmosphere before cleaning because it was left in the atmosphere containing water for a long time, and it was not the corrosion that occurred during or after washing with water.

FIG. 8 is a diagram showing the latent period for corrosion occurrence with respect to the content of Al--Cu alloy. FIG. 8 shows a state in which corrosion of the electrodes occurs due to the time of standing in the atmosphere (relative humidity 50 to 60%) after etching / ashing when the Cu contents are 0.5 wt% and 3.0 wt%. Al-C
In the u alloy, when the Cu content is 0.5 wt%,
It can be confirmed that the latent period for corrosion occurrence is within 1 minute. Further, it can be confirmed that when the Cu content is 3.0 wt%, the corrosion generation latent period is within 5 seconds.

Example 3 A LiNbO ₃ substrate similar to that of Example 1 was formed on the same Al-0.5 substrate.
After forming a surface acoustic wave filter electrode of wt% Cu alloy by the same etching / ashing, the substrate was taken out from the high vacuum chamber into the atmosphere with a relative humidity of 30% or less, and the same was performed in an atmosphere with a relative humidity of 30% or less. As in Example 1, cleaning was performed with ultrapure water from which dissolved oxygen was removed by N ₂ gas bubbling.

In this case, the electrodes did not corrode even if the substrate was taken out from the high-vacuum chamber and cleaned for 15 minutes or more.

This is because the water content in the atmosphere, which is involved in the corrosion of the Al--Cu alloy electrode, is extremely small, and the corrosion incubation period in an atmosphere containing no water is semipermanently long, and the corrosion is extremely large. This is because it is less likely to occur.

Example 4 The same LiNbO ₃ substrate as in Example 1 was used, and the Cu content was 0.5.
Wt%, 1.0 wt%, 2.0 wt%, and 3.0 wt% Al-Cu alloy surface acoustic wave filter electrodes were formed by similar etching / ashing, and then taken out from the high vacuum chamber into the atmosphere. Within minutes, the number of corrosion occurrences was counted.

FIG. 9 is a diagram showing the correlation between the Cu content of the Al—Cu alloy film and the corrosion occurrence rate. In addition, FIG. 10 is an SEM photograph of corrosion that occurred for each Cu content in FIG. 9. In FIGS. 9 and 10, it can be seen that as the Cu content increases, the occurrence rate of corrosion dramatically increases. This is because the CuAl ₂ phase, which is one of the factors causing corrosion, increases as the Cu content increases, which leads to promotion of corrosion generation. CuAl ₂ phase is Al-Cl
Since the natural electrode potential is higher than that of the Cu solid solution phase in the grains, it causes the migration of Al valence electrons and causes the migration of Al valence electrons.
Corrode. (Increase in Potential Caused by Pitting Corrosion) FIG. 11 is a diagram showing the power withstanding life of pure Al and 0.5 wt% Cu alloy electrodes formed by vapor deposition and sputtering. In FIG. 11, in the case of pure Al,
It can be seen that the power withstanding life of both vapor deposition and sputtering is as low as 1 month and 4 months, while that of the Al-0.5 wt% Cu alloy sputter electrode is as long as 10 years.

As described above, it has been shown that the higher the Cu content, the longer the power withstanding life, and the lower the Cu content, the less the occurrence of corrosion. Therefore, the withstand power life is 1
When an Al-0.5 wt% Cu sputtered electrode having a long period of 0 years is adopted, as shown in Examples 1 and 2, N ₂ according to the present invention is used within a corrosion generation latent period of 1 minute.
By rinsing with gas bubbling ultrapure water, corrosion is prevented, and it is possible to obtain a surface acoustic wave device having a high power durability and high reliability. In addition, 1.0 to 2.0 wt% Cu whose power withstanding life is expected to be 10 years or more
When the containing electrode is adopted, as shown in Example 3 according to the present invention, the relative humidity is 30% or less in the air or in dry N.
It is presumed that by cleaning with N ₂ gas bubbling ultrapure water in _two atmospheres, corrosion can be prevented, and it is possible to obtain a surface acoustic wave device with high reliability and a longer withstand power life.

Needless to say, the material of the substrate, the material of the electrode and the structure of the cleaning tank used in the above embodiment are not limited to these.

[0063]

As described above, according to the present invention, Cl, O, which is a factor that reacts with moisture in the atmosphere and induces corrosion of the electrode, is removed from the substrate, and the corrosion generated in the atmosphere is removed. By using ultrapure water from which dissolved oxygen has been removed by N ₂ gas bubbling or CO ₂ gas bubbling, corrosion that newly occurs during water washing can also be prevented by performing water washing for preventing the above.

Further, according to the present invention, the substrate taken out into the atmosphere is cleaned with the ultrapure water within the latent period for corrosion generation, or the substrate is dried in the atmosphere with a relative humidity of 30% or less or in a dry N 2 atmosphere.
₂ Corrosion of electrodes is prevented by cleaning with ultrapure water in an atmosphere.

By this method, it is possible to obtain a highly reliable electrode pattern of the surface acoustic wave device. Further, since expensive gas, catalyst, chemicals, etc. are not used and a simpler device is sufficient, it is possible to improve efficiency and reduce manufacturing cost.

[Brief description of drawings]

FIG. 1 is a sectional view showing a process of an embodiment of the present invention.

FIG. 2 is an explanatory view of a cleaning tank.

FIG. 3 is a correlation diagram between N2 gas bubbling time and the amount of dissolved oxygen in ultrapure water.

FIG. 4 is a diagram showing a corrosion occurrence state during a cleaning time.

FIG. 5 is a SEM photograph of the electrode after cleaning.

FIG. 6 is a correlation diagram between the oxygen content in the bubbling gas and the number of corrosion occurrences.

FIG. 7 is a diagram showing types of bubbling gas and corrosion resistance.

FIG. 8 is a diagram showing the corrosion incubation period with respect to the Cu content of the Al—Cu alloy film.

FIG. 9 is a correlation diagram between the Cu content and the corrosion occurrence rate of the Al—Cu alloy film.

FIG. 10 is an SEM photograph showing the Cu content and the corrosion occurrence state of the Al—Cu alloy film.

FIG. 11 is a diagram showing the power resistance of the electrode according to the film quality and the film forming method.

FIG. 12 is a diagram of a conventional example of a surface treatment apparatus.

FIG. 13 is a view of a conventional example of a water washing device.

[Explanation of symbols]

11--Piezoelectric single crystal substrate 12 --- Al-Cu alloy electrode layer 13 --- Photoresist pattern 21 ── Washing tank 22 ── Perforated plate 23 --- Substrate holder 24 ── Piezoelectric single crystal substrate

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshikazu Narimiya               1-13-1, Nihonbashi, Chuo-ku, Tokyo               -In DC Inc.                (56) Reference JP-A-6-61774 (JP, A)                 JP-A-5-291863 (JP, A)                 Japanese Patent Laid-Open No. 2-312308 (JP, A)                 JP-A-2-206214 (JP, A)                 JP-A-2-94911 (JP, A)                 JP-A-1-259611 (JP, A)                 JP-A-7-45569 (JP, A)                 63-162526 (JP, U)

Claims (7)

(57) [Claims] 1. A step of forming an Al—Cu alloy electrode on a piezoelectric substrate for a surface acoustic wave device by plasma etching of chlorine-based gas, a step of resist ashing, and a piezoelectric element for a surface acoustic wave device after the resist ashing. It occurs when the deoxidation treatment is not carried out by including the step of washing the substrate with ultrapure water that has been deoxidized.
A method for manufacturing a surface acoustic wave device, characterized in that corrosion of an Al-Cu alloy electrode is suppressed . 2. The method of manufacturing a surface acoustic wave device according to claim 1, wherein the deoxidation treatment of ultrapure water is performed by N ₂ gas bubbling. 3. The method of manufacturing a surface acoustic wave device according to claim 1, wherein the deoxygenation treatment of ultrapure water is performed by CO 2 gas bubbling. By plasma etching of 4. A chlorine-based gas, and forming a Al-Cu alloy electrode on the piezoelectric substrate for a surface acoustic wave device, a step of resist ashing while continuing keeping the high vacuum, the after the resist ashing
It occurs when deoxidation treatment is not performed by having a step of removing the piezoelectric substrate for surface acoustic wave from the high vacuum chamber to the atmosphere and cleaning it with ultrapure water that has been deoxidized.
In the method of manufacturing a surface acoustic wave device for suppressing the corrosion of an Al-Cu alloy electrode , the following step is performed within 1 minute after the piezoelectric substrate for the surface acoustic wave device is taken out of the high vacuum chamber into the atmosphere. A method of manufacturing a surface acoustic wave device, which comprises cleaning in a cleaning step. 5. A step of forming an Al--Cu alloy electrode on a piezoelectric substrate for a surface acoustic wave device by plasma etching with a chlorine-based gas, a step of successively performing resist ashing while maintaining a high vacuum, and a step of performing the resist ashing after the resist ashing.
By removing the piezoelectric substrate for the surface acoustic wave device into the atmosphere from the high vacuum chamber and cleaning it with deionized ultrapure water, it is possible to generate the piezoelectric substrate when deoxidation is not performed.
In a method of manufacturing a surface acoustic wave device for suppressing corrosion of a generated Al-Cu alloy electrode, the surface acoustic wave device piezoelectric substrate is taken out of the high vacuum chamber into the atmosphere and cleaned in the cleaning step. Atmosphere until the relative humidity is 30
% Or less, a method of manufacturing a surface acoustic wave device. 6. The atmosphere until the substrate is taken out of the high vacuum chamber and washed in the washing step is dry N.
_The method for manufacturing a surface acoustic wave device according to claim 5, wherein the atmosphere is _two atmospheres. 7. The method of manufacturing a surface acoustic wave device according to claim 1, wherein the Al—Cu alloy electrode contains Cu of 0.5 to 2.0 wt%.