JP2005142911A - Manufacturing method of surface acoustic wave chip, surface acoustic wave chip manufactured by the same manufacturing method and surface acoustic wave device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a surface acoustic wave chip which enhances frequency precision by enhancing process tolerance at the time of electrode pattern formation, a surface acoustic wave chip manufactured by the manufacturing method and a surface acoustic wave device. <P>SOLUTION: The manufacturing method of the surface acoustic wave chip is constituted so as to form metal film 18 on a piezoelectric substrate 24, to form insulation film 20 on the metal film 18 to be a surface acoustic wave propagation area, to perform dry etching to the metal film 18 and the insulation film 20, to terminate the dry etching based on plasma light emission intensity resulting from the metal film 18, to perform wet etching from a position where the dry etching is stopped to the surface of the piezoelectric substrate to be the surface acoustic wave propagation area and to form an electrode pattern. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a surface acoustic wave chip manufacturing method, a surface acoustic wave chip manufactured by the manufacturing method, and a surface acoustic wave device.

  A surface acoustic wave (hereinafter referred to as SAW) chip forms a pair of interdigital electrodes (hereinafter referred to as IDT) on the surface of a piezoelectric substrate made of a single crystal material having a piezoelectric effect, and this IDT. The main configuration is that reflectors are formed at both ends of the. The IDT and the reflector may be formed of an aluminum alloy or the like, or may be formed by forming an insulating film such as silicon oxide on the aluminum alloy or the like.

  Conventionally, this SAW chip uses a method in which an electrode material is formed on a piezoelectric substrate, a resist pattern is formed on the electrode material by a photolithography technique, and the electrode material is wet-etched to form an electrode pattern. It was. By the way, in recent years, since high frequency and high accuracy of the SAW chip have been achieved, a fine processing technique using a dry etching technique such as reactive ion etching has been applied (for example, see Patent Document 1). .

There is also a processing method in which dry etching is performed before reaching the surface of the piezoelectric substrate, and wet etching is performed from the position where dry etching is stopped to the surface of the piezoelectric substrate (see Patent Document 2 and Patent Document 3).
JP 2002-33633 A JP-A-62-71317 JP-A-10-135759

  However, when forming an electrode pattern using dry etching technology, the surface of the piezoelectric substrate is etched in order to reliably remove the electrode material, and the surface of the piezoelectric substrate is exposed to etching plasma to cause a crystalline state. Instead, it becomes amorphous. For this reason, there is a problem in that the propagation of the surface acoustic wave is affected, and in particular, the Q value is deteriorated and the resonance frequency is varied. In addition, the reliability of the SAW chip decreases due to the occurrence of corrosion due to etching gas such as chlorine remaining at the interface between the piezoelectric substrate and the electrode material or at the interface between the electrode material and the insulating film formed on the electrode material. There is a point.

  FIG. 8 is an explanatory diagram of the plasma emission intensity during dry etching. FIG. 8 shows the relationship between the emission intensity of aluminum detached from the metal film and time. And when etching of a metal film is complete | finished, it represents that emitted light intensity falls. FIG. 9 is an explanatory diagram of frequency distribution between wafers in the SAW chip. FIG. 9 shows the measurement of the resonance frequency of each SAW chip manufactured from one wafer, the average of the resonance frequencies to calculate the average resonance frequency of the wafer, and the average resonance frequency of a plurality of wafers. These distributions are examined. When an electrode pattern is formed by applying both dry etching and wet etching processes, dry etching is generally performed by time etching converted from a steady etching rate. By the way, in dry etching, the etching rate varies greatly depending on the state of the etching apparatus, for example, the gas flow rate, gas ratio, gas pressure supplied to the apparatus, and whether or not the apparatus is heated by plasma. For this reason, when dry etching is finished after a lapse of a certain time, there is a problem that the thickness variation of the metal film, that is, the remaining film thickness of the metal film after dry etching varies greatly.

  In the subsequent wet etching, the remaining film thickness of the metal film is etched, and at the same time, the side wall of the metal film is etched. In dry etching, the remaining film thickness of the metal film varies from wafer to wafer, so that the wet etching time varies depending on the remaining film thickness. For this reason, since the time for etching the side wall of the metal film is different, the width of the electrode pattern also varies. By the way, the resonance frequency fluctuates by changing the width of the electrode pattern. For this reason, as shown in FIG. 9, there is a problem that the obtained frequency characteristics are largely fluctuated at the wafer level due to processing variations in the lateral direction of wet etching.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a method for manufacturing a surface acoustic wave chip to obtain a constant frequency characteristic by increasing the processing accuracy of an electrode pattern, and a surface acoustic wave chip manufactured by the method. The purpose is to provide.
Another object of the present invention is to provide a surface acoustic wave device using a surface acoustic wave chip.

  In order to achieve the above object, a surface acoustic wave chip manufacturing method according to the present invention includes forming a metal film on a piezoelectric substrate, forming an insulating film on a metal film serving as a surface acoustic wave propagation region, and The metal film and the insulating film are dry-etched through a pattern mask formed on the film, the dry etching is terminated based on the change in the plasma emission intensity caused by the metal film, and the dry etching is stopped from the position. The electrode pattern is formed by wet etching up to the surface of the piezoelectric substrate which is a surface acoustic wave propagation region. In this case, the dry etching is preferably terminated when the plasma emission intensity is reduced by removing the metal film formed outside the surface acoustic wave propagation region. The plasma emission intensity is observed each time dry etching is performed, and the dry etching is terminated when the plasma emission intensity caused by the metal film decreases. Therefore, the same level of metal film is always etched regardless of the state of the dry etching equipment. can do. And since the metal film which always has the same film thickness is wet-etched, the etching time does not vary. And the width of the electrode pattern of the surface acoustic wave (SAW) chip obtained does not vary. Therefore, since the processing accuracy of the electrode pattern can be increased, the frequency accuracy of the SAW chip can be improved.

  Further, the dry etching is characterized in that it is terminated during the etching of the metal film formed in the surface acoustic wave propagation region. As a result, the surface acoustic wave propagation region is not exposed to the etching plasma, so that the crystal structure of the surface of the piezoelectric substrate changes and the Q value does not decrease. Therefore, a highly accurate SAW chip can be manufactured.

  The metal film is formed of aluminum or an aluminum-based alloy. Thereby, an electrode pattern can be processed with high precision in both dry etching and wet etching processes. Further, by using aluminum or an aluminum-based alloy, an anodized film can be formed on the metal film.

  The insulating film is an anodized film formed by anodizing the metal film. Thereby, even if a conductive foreign material falls on the electrode pattern, the electrode patterns are not short-circuited. Further, since the interface between the anodic oxide film and the metal film is continuous, no etching gas enters the interface and does not remain, so that no corrosion occurs. Therefore, a highly reliable SAW chip can be manufactured.

  The insulating film is formed by forming a silicon insulating film or an aluminum insulating film. Thereby, even if a conductive foreign material falls on the electrode pattern, the electrode patterns are not short-circuited. Therefore, a highly reliable SAW chip can be manufactured.

The surface acoustic wave chip according to the present invention is manufactured using the above-described manufacturing method. Thereby, a SAW chip having the above-described characteristics can be obtained.
A surface acoustic wave device according to the present invention includes the surface acoustic wave chip described above. Accordingly, the SAW chip having the above-described characteristics can be used for a SAW device such as a SAW vibrator, a SAW oscillator, or a SAW filter.

  Hereinafter, preferred embodiments of a surface acoustic wave chip manufacturing method, a surface acoustic wave chip manufactured by the manufacturing method, and a surface acoustic wave device according to the present invention will be described. FIG. 1 shows a cross-sectional view of an electrode pattern according to this embodiment. FIG. 1A is a cross-sectional view of an interdigital electrode and a reflector, and FIG. 1B is a cross-sectional view of a pad. FIG. 2 shows a plan view of the surface acoustic wave chip. The surface acoustic wave (SAW) chip 10 has a configuration in which an electrode pattern including interdigital electrodes 12 (IDTs 12), reflectors 14 and pads 16 is formed on the surface of a piezoelectric substrate 24 made of a material that generates a piezoelectric effect. .

  The IDT 12 has a plurality of electrode fingers, and the IDTs 12 are arranged by alternately engaging the electrode fingers. Reflectors 14 are formed on both sides of the IDT 12 in the meshing direction. A pad 16 is formed between the IDT 12 and the reflector 14 and the side of the piezoelectric substrate 24, and the pad 16 and the IDT 12 are conductively connected. The pad 16 serves as an electrode when wire bonding is performed or when flip chip bonding is performed.

  The IDT 12, the reflector 14, and the pad 16 are formed from a metal film 18 such as aluminum or an aluminum alloy. The aluminum alloy is, for example, an aluminum / copper alloy or an aluminum / silicon alloy. Further, an insulating film 20 is formed on the metal film 18 that becomes the IDT 12 and the reflector 14. The insulating film 20 is formed by forming an anodic oxide film formed by anodizing the surface of the metal film 18 or an insulating material such as silicon oxide, silicon nitride, or aluminum oxide on the metal film 18. A silicon insulating film or an aluminum insulating film.

  The film thickness of the anodized film formed by anodization depends on the voltage at the time of anodization and can be controlled with high accuracy. In the anodic oxidation, oxygen and metal ions are combined on the surface of the metal film 18 and the oxidation proceeds. Therefore, atoms at the interface between the metal film 18 and the anodic oxide film are combined with each other, and the interface is continuous.

  When an electric signal is applied to the IDT 12 of the SAW chip 10 through the pad 16, a periodic distortion is generated between the electrode fingers due to the piezoelectric effect of the piezoelectric substrate 24, and the surface acoustic wave is excited to engage the electrode fingers. Propagated along the direction. The propagated surface acoustic wave is reflected by the reflector 14. For this reason, the surface acoustic wave is propagated between the reflectors 14 via the IDT 12, and the piezoelectric substrate 24 in the portion where the IDT 12 and the reflector 14 are formed becomes the surface acoustic wave propagation region.

  Next, a method for manufacturing the SAW chip 10 will be described. First, a dry etching apparatus used for manufacturing the SAW chip 10 will be described. FIG. 3 is an explanatory diagram of the dry etching apparatus. The dry etching apparatus 30 has a configuration in which a chamber 32 for mainly performing dry etching and a plasma emission spectrum monitor 34 for observing an emission spectrum of plasma generated in the chamber 32 are provided. A plate-like lower electrode 36 is provided in the lower part of the chamber 32, and a piezoelectric wafer 50 to be dry-etched is placed on the lower electrode 36. A plate-like upper electrode 38 is provided on the upper part. The lower electrode 36 and the upper electrode 38 are connected to a high frequency power source (not shown) and generate plasma as a capacitive coupling type. A gas supply unit 40 for supplying an etching gas such as chlorine or boron chloride is connected to the chamber 32. Further, a light receiving portion 42 for receiving plasma light is provided on the side surface of the chamber 32. An amplification processing unit 44 and a display unit 46 are connected to the light receiving unit 42 in series. The light receiving unit 42, the amplification processing unit 44, and the display unit 46 constitute a plasma emission spectrum monitor 34. The plasma emission spectrum monitor 34 outputs the light received by the light receiving unit 42 to the amplification processing unit 44, and the amplification processing unit 44 44, the light is amplified and spectrum analysis is performed, the analysis result is output to the display unit 46, and the display unit 46 displays the spectrum. The plasma emission spectrum monitor 34 is used for detecting the etching end point.

  Next, the first manufacturing method will be described. FIG. 4 is an explanatory view of the first manufacturing method. In FIG. 4, the diagram shown on the right side is a plan view of the SAW chip formed on the piezoelectric wafer 50, the diagram shown in the center is a cross-sectional view along the line YY ′, and the diagram shown on the left side is along the line XX ′. It is sectional drawing. FIG. 5 is an explanatory diagram of the plasma emission intensity during dry etching. First, a metal film 18 such as aluminum or aluminum alloy is formed on the entire surface of the piezoelectric wafer 50 by using a film forming method such as sputtering or vapor deposition (S110). A photoresist is applied on the metal film 18, exposed and developed to form a first resist mask 52 other than the portion that becomes the surface acoustic wave propagation surface of the SAW chip 10 (S120). Then, the surface of the metal film 18 which becomes the surface acoustic wave propagation surface is anodized to form the anodized film 22 (S130).

  Next, after peeling off the first resist mask 52, a photoresist is applied onto the metal film 18 and the anodic oxide film 22, exposed and developed, and the second resist mask 54 is formed at a position where an electrode pattern is formed. Is formed (S140). The portions other than the electrode pattern are dry-etched to remove the metal film 18 formed outside the surface acoustic wave propagation region, and the anodic oxide film 22 and the metal film 18 formed above the surface acoustic wave propagation region are removed. It is removed (S150).

  Incidentally, since the etching rates of the metal film 18 and the anodic oxide film 22 are different, the metal film 18 is etched faster than the anodic oxide film 22. For this reason, even if the etching of the metal film 18 formed outside the surface acoustic wave propagation region is finished, the etching of the metal film 18 formed in the surface acoustic wave propagation region is not finished. At this time, when the emission spectrum (wavelength: 396 nm) of aluminum that has been etched away from the metal film 18 is observed by the plasma emission spectrum monitor 34, the etching of the metal film 18 formed outside the surface acoustic wave propagation region is completed. The light emission intensity of aluminum decreases. When this decrease in emission intensity is detected, this is the first end point for ending dry etching (see FIG. 5). At this time, if the overetching is performed after the emission intensity is reduced, the metal film 18 is surely removed. Therefore, the first end point may be after the overetching.

  If dry etching is further continued thereafter, the metal film 18 formed in the surface acoustic wave propagation region is removed, and light emission of aluminum is not observed. This is the second end point (see FIG. 5). Therefore, when the plasma emission spectrum monitor 34 observes the emission intensity of aluminum during dry etching, and the dry etching is terminated when the emission intensity decreases (detects the first end point), the metal film 18 other than the surface acoustic wave propagation region. Is removed, and the upper side of the metal film 18 in the surface acoustic wave propagation region is removed.

  Further, the larger the region of the metal film 18 formed on the piezoelectric wafer 50 and exposed on the surface, that is, the portion other than the surface acoustic wave propagation surface, the larger the amount of change in the light emission intensity of aluminum at the first end point. The amount of change in light emission intensity at the second end point becomes small. As the number of electrode patterns formed on the piezoelectric wafer 50 increases, the amount of change in the light emission intensity of aluminum at the first end point decreases, and the amount of change in the light emission intensity at the second end point increases.

Further, by changing the film thickness of the anodic oxide film 22, the etched thickness of the metal film 18 on the surface acoustic wave propagation surface and the etched thickness of the metal film 18 on the surface other than the surface acoustic wave propagation surface can be changed. . Therefore, when the thickness of the anodic oxide film 22 is increased, the difference between the thickness of the metal film 18 on the surface acoustic wave propagation surface and the thickness of the metal film 18 on the surface other than the surface acoustic wave propagation surface increases.
As a method for generating plasma when performing dry etching, an inductive coupling type, an electron cyclotron resonance method, or the like may be used.

  Next, after the first end point is detected and dry etching is completed, the piezoelectric wafer 50 is immersed in an etching solution such as phosphoric acid, and wet etching is performed from the position where dry etching is completed to the surface of the piezoelectric wafer 50. Then, the metal film 18 formed in the surface acoustic wave propagation region is removed (S160). The etching solution is not limited to a phosphoric acid-based etching solution as long as it is a selective solution that etches the metal film 18 but does not etch the piezoelectric wafer 50. Thereafter, when the second resist mask 54 is peeled off, a plurality of electrode patterns are formed on the piezoelectric wafer 50 (S170). Finally, each SAW chip 10 is manufactured by dicing the piezoelectric wafer 50 (S180).

  In such a manufacturing method, since the surface of the piezoelectric wafer 50 other than the surface acoustic wave propagation region is exposed to the etching plasma, the surface of the piezoelectric wafer 50 becomes amorphous, but the surface of the piezoelectric wafer 50 in the surface acoustic wave propagation region is Since it is not exposed to the etching plasma, the crystal structure is maintained.

  Next, the second manufacturing method will be described. FIG. 6 shows an explanatory diagram of the second manufacturing method. In FIG. 6, the diagram shown on the right side is a plan view of the SAW chip formed on the piezoelectric wafer 50, the diagram shown in the center is a cross-sectional view along the line YY ′, and the diagram shown on the left side is along the line XX ′. It is sectional drawing. First, a metal film 18 such as aluminum or aluminum alloy is formed on the entire surface of the piezoelectric wafer 50 by using a film forming method such as sputtering or vapor deposition (S210). An insulating film 20 such as silicon oxide is formed on the entire surface of the metal film 18 by using a film forming method such as sputtering, vapor deposition, or vapor deposition (S220). A photoresist is applied on the insulating film 20, exposed, and developed to form a first resist mask 52 on the SAW chip 10 at a portion to be a surface acoustic wave propagation surface (S230). The insulating film 20 formed outside the surface acoustic wave propagation region is removed by dry etching or wet etching to expose the metal film 18 (S240).

  Next, after removing the first resist mask 52, a second resist mask 54 is formed at a position where the electrode pattern of the SAW chip 10 is formed (S250). The portions other than the electrode pattern are dry-etched to remove the metal film 18 formed outside the surface acoustic wave propagation region, and the insulating film 20 and the upper side of the metal film 18 formed in the surface acoustic wave propagation region are removed. (S260). The dry etching process of S260 may be performed in the same manner as the dry etching process of S150 in the first manufacturing method.

  Next, wet etching is performed from the position where dry etching is completed to the surface of the piezoelectric wafer 50 to remove the metal film 18 formed in the surface acoustic wave propagation region (S270). The wet etching process in S270 may be performed in the same manner as the wet etching process in S160 in the first manufacturing method. Thereafter, when the second resist mask 54 is peeled off, a plurality of electrode patterns are formed on the piezoelectric wafer 50 (S280). Finally, the piezoelectric wafer 50 is diced to manufacture each SAW chip 10 (S290).

  Next, the frequency distribution between wafers of the SAW chip 10 manufactured as described above was examined. First, the resonance frequency of each SAW chip 10 manufactured from one wafer is measured, and the average resonance frequency of the wafer is calculated by averaging the resonance frequencies. The average resonance frequency was calculated for a plurality of wafers, and their distribution was examined. FIG. 7 is an explanatory diagram of frequency distribution between wafers. The vertical axis in FIG. 7 represents the average resonance frequency, and the horizontal axis represents the frequency. FIG. 7 shows that the frequency distribution is distributed in a narrow range with a certain average resonance frequency as a maximum. Thereby, even if the SAW chip 10 manufactured using the manufacturing method according to the present embodiment is manufactured from different wafers, the resonance frequency hardly varies and the SAW chip 10 is manufactured with high accuracy. Understand.

  When the SAW chip 10 according to the present embodiment is mounted on a package, a SAW resonator is formed, and when the SAW chip 10 and an oscillation circuit are mounted on the package, a SAW oscillator is formed. Further, the SAW chip 10 according to the present embodiment can be used as a SAW filter. In this way, a SAW device is formed.

  The electrode pattern of the SAW chip 10 has a configuration in which the metal film 18 and the insulating film 20 are formed in the surface acoustic wave propagation region, and only the metal film 18 is formed outside the surface acoustic wave propagation region. When dry etching is performed during the formation of this electrode pattern, the metal film 18 outside the surface acoustic wave propagation region is removed first, and the lower part of the metal film 18 in the surface acoustic wave propagation region remains. At this time, when the emission intensity of aluminum constituting the metal film 18 is observed in the plasma emission spectrum monitor 34, a decrease in the emission intensity can be observed. When the decrease in the emission intensity is observed as the etching end point detection point, the metal film 18 in the surface acoustic wave region can always be left to the same extent even when the etching conditions, that is, the state of the dry etching apparatus changes. Further, by observing the decrease in the emission intensity and then performing overetching, no etching residue is generated in the metal film 18 outside the surface acoustic wave propagation region.

  Since the metal film 18 that always has the same film thickness is wet-etched, there is no variation in etching time. By the way, since the wet etching is isotropic etching, the metal film 18 is etched and the electrode pattern is also etched. For this reason, if the film thickness of the metal film 18 remaining in the surface acoustic wave propagation region varies as in the manufacturing method according to the prior art, the amount of etching of the electrode pattern varies from wafer to wafer, resulting in variations in the resonance frequency. . However, in the manufacturing method according to the present embodiment, there is no variation in the etching amount during dry etching. Therefore, the wet etching always has the same etching amount, and the resonance frequency does not vary. Therefore, it is possible to manufacture the SAW chip 10 that always has the same resonance frequency.

  If the electrode pattern formed on the surface acoustic wave propagation surface is composed of a metal film 18 and an anodized film 22 obtained by anodizing the surface of the metal film 18, the interface between the metal film 18 and the anodized film 22 is continuous. Therefore, an etching gas such as chlorine does not enter the interface and remain. For this reason, since corrosion does not occur in the electrode pattern, a highly reliable SAW chip 10 can be manufactured.

  Further, when etching the electrode pattern on the surface acoustic wave propagation surface, the structure is such that dry etching is performed halfway through the electrode pattern and wet etching is performed from the position where the dry etching is stopped to the surface of the piezoelectric substrate 24. The surface is not exposed to the etching plasma. For this reason, the Q value of the SAW chip 10 does not deteriorate. Further, since the etching gas does not enter and remain at the interface between the piezoelectric substrate 24 and the electrode pattern, corrosion does not occur. Therefore, the SAW chip 10 with high accuracy and high reliability can be manufactured.

  In addition, since the insulating film 20 is formed on the surface of the electrode pattern formed on the surface acoustic wave propagation surface, the electrode pattern will not be short-circuited even if conductive foreign matter adheres to the electrode pattern. Therefore, the highly reliable SAW chip 10 can be manufactured.

  In the present embodiment, the insulating film 20 is formed on the metal film 18 in the surface acoustic wave propagation region, and the etching can be made different from the metal film 18 outside the surface acoustic wave propagation region. While the metal film 18 is being formed thereon, a mask that covers the peripheral edge of the wafer may be covered, and a step may be provided on the metal film 18 at the center and peripheral edge of the wafer. With this configuration, when the dry etching is performed, the metal film 18 at the peripheral portion is removed first, and this time can be set as the first end point. Therefore, it is not necessary to form the insulating film 20 on the metal film 18 as in the present embodiment.

Instead of covering the mask in the middle of the film formation, the metal film 18 on the peripheral edge of the wafer may be etched to provide a step.
In the present embodiment, the reflectors 14 are provided at both ends of the IDT 12, but the reflectors may be omitted. In this case, the electrode pattern is composed of an IDT and a pad.

  Note that the surface of the piezoelectric substrate other than the surface acoustic wave propagation surface in the SAW chip 10 according to the present embodiment has an amorphous structure, and the surface acoustic wave propagation surface maintains the crystal structure of the piezoelectric substrate. This can be confirmed by observing the crystal structure with a transmission electron microscope. The appearance of the electrode pattern in the SAW chip 10 according to this embodiment is different between the surface acoustic wave propagation surface and the surface acoustic wave propagation surface, that is, the IDT, the reflector, and the pad. This can be confirmed by observing the appearance with a scanning electron microscope or the like. Therefore, by observing the SAW chip, it can be confirmed whether or not the SAW chip is manufactured by the method for manufacturing the SAW chip 10 according to the present embodiment.

It is sectional drawing of the electrode pattern which concerns on this embodiment. It is a top view of the surface acoustic wave chip concerning this embodiment. It is explanatory drawing of a dry etching apparatus. It is explanatory drawing of the 1st manufacturing method of a surface acoustic wave chip. It is explanatory drawing of the plasma luminescence intensity at the time of dry etching concerning this embodiment. It is explanatory drawing of the 2nd manufacturing method of a surface acoustic wave chip | tip. It is explanatory drawing of the frequency distribution between the wafers in the surface acoustic wave chip concerning this embodiment. It is explanatory drawing of the plasma emission intensity at the time of dry etching concerning a prior art. It is explanatory drawing of the frequency distribution between the wafers in the surface acoustic wave chip concerning a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ......... Surface acoustic wave (SAW) chip | tip, 12 ......... Interdigital electrode (IDT), 14 ......... Reflector, 16 ......... Pad, 18 ......... Metal film, 20 ...... Insulating film, 24... Piezoelectric substrate, 30... Dry etching apparatus, 32... Chamber, 34.

Claims (8)

  A metal film is formed on the piezoelectric substrate, an insulating film is formed on the metal film serving as a surface acoustic wave propagation region, and the metal film and the insulating film are dry-etched through a mask of a pattern formed on the insulating film. Then, dry etching is completed based on the change in plasma emission intensity caused by the metal film, and the electrode pattern is formed by wet etching from the position where dry etching is stopped to the surface of the piezoelectric substrate that is the surface acoustic wave propagation region. A method of manufacturing a surface acoustic wave chip.   2. The method of manufacturing a surface acoustic wave chip according to claim 1, wherein the dry etching is terminated when the metal film formed outside the surface acoustic wave propagation region is removed and the plasma emission intensity decreases.   3. The method of manufacturing a surface acoustic wave chip according to claim 1, wherein the dry etching is terminated during the etching of the metal film formed in the surface acoustic wave propagation region.   4. The method for manufacturing a surface acoustic wave chip according to claim 1, wherein the metal film is formed of aluminum or an aluminum-based alloy.   5. The method for manufacturing a surface acoustic wave chip according to claim 1, wherein the insulating film is an anodized film formed by anodizing the metal film.   5. The method for manufacturing a surface acoustic wave chip according to claim 1, wherein the insulating film is formed by forming a silicon insulating film or an aluminum insulating film.   A surface acoustic wave chip manufactured using the method for manufacturing a surface acoustic wave chip according to claim 1. A surface acoustic wave device comprising the surface acoustic wave chip according to claim 7.

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