JP2007124529A - Surface acoustic wave element and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave element excellent in reliability by bringing it close to desired frequency characteristics, and consequently, by improving manufacturing efficiency in a manufacturing process of the surface acoustic wave element, and to provide a method of manufacturing the same. <P>SOLUTION: The surface acoustic wave element 1 has excitation electrodes 2 respectively provided with comb-like electrode fingers, pad electrode parts 4 respectively connected to each excitation electrode 2 via a conductive metal, a protection film 3 formed on the excitation electrodes 2 and the pad electrode parts 4. Each pad electrode part 4 has two window parts in which an electrode connected to the excitation electrode 2 is exposed by partially removing the protection film 3 and which respectively function as a probe pad electrode 41 for bringing a probe needle to input a signal into contact with it and a mounting pad electrode 42 for connecting to a mounting substrate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface acoustic wave element and a method for manufacturing the same, and more particularly to a surface acoustic wave element formed on a piezoelectric substrate used in mobile communication equipment such as a mobile phone.

  In recent years, a surface acoustic wave element mounted on a communication device such as a cellular phone has been further reduced in size, and is widely used in fields other than the field where the communication device is used. In addition to this miniaturization, with the increase in frequency of communication carriers, excitation electrodes that excite surface acoustic waves contained in the surface acoustic wave element have a narrow interval between the electrode fingers that form the excitation electrodes. The width of is narrow. For this reason, the excitation electrode included in the surface acoustic wave element is required to be processed based on a finer design as the output frequency becomes higher.

  As described above, surface acoustic wave elements having high-frequency communication carriers are manufactured based on a fine design. Therefore, a slight design produced in the final product of the surface acoustic wave element manufacturing process. Even the above variations can cause large fluctuations in the output frequency of each product. This varies, for example, in the line width of the excitation electrode, the thickness of the excitation electrode, the electrode finger pitch, the thickness of the protective film protecting the excitation electrode, the homogeneity of the crystal structure of the metal layer forming the excitation electrode, etc. This is considered to be due to variations in characteristics such as sound velocity of the surface acoustic wave generated on the piezoelectric substrate of each surface acoustic wave element. Therefore, as the frequency of the communication carrier increases, the surface acoustic wave element has a tendency that the frequency characteristics of the insertion loss easily fluctuate from a desired value, which may further reduce the yield and reliability.

For this reason, when forming a surface acoustic wave element, it is necessary to correct variations in frequency characteristics including the center frequency indicating the center frequency of the passband.
For example, Patent Document 1 proposes a method of manufacturing a layered surface acoustic wave device that can be adjusted to a desired center frequency by changing the thickness of a protective film on an excitation electrode.
In Patent Document 2, an etching process is added after an excitation electrode having a certain thickness is formed in order to obtain a desired center frequency by shifting the center frequency higher, and the excitation electrode is formed by this etching process. There has been proposed a method of manufacturing a surface acoustic wave device that is thinned and frequency-adjusted.
Japanese Patent Application Laid-Open No. 61-077407 Japanese Patent Laid-Open No. 03-241212 Japanese Patent Laid-Open No. 01-231212

  As one of methods for correcting the variation in frequency characteristics of the surface acoustic wave element as described above, as described in Patent Document 1, a material such as silicon dioxide is used on the surface of the piezoelectric substrate on which the excitation electrode is formed. Adjusting the center frequency of the passband of the surface acoustic wave element can be mentioned by adjusting the thickness of the protective film to be formed. This method of adjusting the center frequency of the pass band utilizes the fact that the sound velocity of the surface acoustic wave changes due to the mass effect caused by the difference in the thickness of the protective film. The mass effect indicates that the surface acoustic wave excited by the surface acoustic wave element changes depending on the thickness of the protective film, that is, the mass of the protective film formed on the piezoelectric substrate. For example, if the thickness of the protective film is reduced, the center frequency of the pass band of the surface acoustic wave element can be increased. Conversely, if the thickness of the protective film is increased, the center frequency of the pass band is increased. Can be lowered.

  At this time, even if the etching amount of the protective film is constant in the wafer-like mother substrate formed of the piezoelectric substrate, the center frequency generated by the surface acoustic wave element may vary from a desired value. Such variation in the center frequency of each surface acoustic wave element is considered to appear due to a process of batch processing or a slight difference in characteristics of the surface acoustic wave element for each mother substrate as a piezoelectric substrate.

In the conventional etching of the protective film using the mass effect of the protective film, the thickness of the protective film is increased or decreased with respect to slight variations in the structure of the plurality of surface acoustic wave elements formed on the mother substrate. Therefore, it is difficult to obtain a desired frequency characteristic for the manufactured surface acoustic wave device.
Moreover, if the protective film is formed too thinly by increasing the center frequency, the protective film should maintain the film thickness necessary for protecting the excitation electrode from external factors such as conductive foreign matter and moisture. Thus, the protective film cannot play its original role of protecting various electrode patterns formed on the piezoelectric substrate.

Therefore, the passive frequency control method based on the process management as described in these patent documents only has a few options including the method of narrowing the in-process control value, and the rework of the process defect and the defect rate are reduced. It will cause an increase.
Therefore, in order to measure the frequency characteristics of the insertion loss of the surface acoustic wave element and to check whether the variation in the frequency characteristics is within an allowable range, an electrode needle for inspection (probe needle) is connected to the electrode on the surface acoustic wave element. ) To input the evaluation signal and measure the frequency characteristics of the insertion loss. Up to now, the mounting pad electrode used for bonding to the mounting substrate also served as the probe electrode, but the metal thin film that forms the mounting pad electrode by the stress applied when the probe needle is applied However, the mounting pad electrode may be damaged due to remaining probe marks.

  Therefore, it is conceivable to provide a probe pad electrode electrically connected to the mounting pad electrode as an electrode necessary for measuring the frequency characteristics of the insertion loss. This probe pad electrode removes the protective film formed on the probe pad electrode so as to have a larger area than the mounting pad electrode so that the probe needle can be easily applied when measuring the frequency characteristics of the insertion loss. . At this time, an etching process such as wet etching or dry etching is used to remove the protective film for forming various electrode patterns including these probe pad electrodes and mounting pad electrodes.

  When etching a predetermined portion of the protective film on various electrode patterns using wet etching, water is often used in the cleaning operation. In this cleaning operation, for example, when various electrode patterns are formed of a metal material mainly composed of Al, such as an Al—Cu alloy having excellent pressure resistance, various electrode patterns formed with this material and water for etching are used. And the local battery effect appears. In particular, a large probe pad electrode is easily corroded by this local battery effect. Further, the corrosion generated in the probe pad electrode spreads to the adjacent mounting pad electrode, and the filter characteristics of the surface acoustic wave element including the mounting pad electrode may be deteriorated.

On the other hand, when a predetermined portion of the protective film on various electrode patterns is etched using dry etching, a chlorine-based gas such as BCl ₃ is used as an etching gas. Then, after this etching process, water may be used in a dicing process or the like, but at this time, the probe pad electrode formed largely corrodes easily due to the influence of residual chlorine used in the etching. As a result, as in the case of wet etching, corrosion spreads to the mounting pad electrode, and the filter characteristics may be deteriorated.

Whichever etching is used, when the probe pad electrode is provided adjacent to the mounting pad electrode, the probe pad electrode having a larger area than the mounting pad electrode is likely to corrode. There is a possibility that the area may extend to the mounting pad electrode.
For this reason, defects are likely to occur in the connection between the corroded mounting pad electrode and the bump connection body or the wire bonding connection, which may cause a problem in reliability after mounting the surface acoustic wave element.

  Therefore, the present invention solves the above-described conventional problems, and can approximate the desired frequency characteristics in the manufacturing process of the surface acoustic wave device, thereby increasing the manufacturing efficiency and improving the reliability. An object of the present invention is to provide an excellent surface acoustic wave device and a method for manufacturing the same.

  A surface acoustic wave element for achieving the above object is a surface acoustic wave element that excites a surface acoustic wave by an excitation electrode formed on a main surface of a piezoelectric substrate, and has comb-like electrode fingers. The excitation electrode, a pad electrode portion connected to the excitation electrode, and a protective film formed on the excitation electrode and the pad electrode. The pad electrode portion includes one of the protective films. The two windows are formed by removing the part and exposing the electrodes. Each of the two windows is a probe pad electrode for contacting an electrode needle for inputting a signal and a mounting for connecting to a mounting substrate. It functions as a pad electrode.

  According to this configuration, the surface acoustic wave is formed by forming a probe pad electrode as an electrode for evaluation measurement for inputting a signal by applying an electrode needle for inputting a signal on the surface acoustic wave element. Since the frequency characteristic of the insertion loss of the element can be measured, for example, the etching amount of the protective film can be adjusted. In addition, by measuring the frequency characteristics of the insertion loss during the etching of the protective film, the amount of etching of the protective film thickness can be adjusted, thereby correcting the frequency characteristic variation that occurs during the production of the surface acoustic wave device. As a result, the yield of the surface acoustic wave device can be improved.

  In addition, since the probe pad electrode and the mounting pad electrode are electrically connected, the mounting pad can be measured even if the frequency characteristic of the insertion loss is measured by applying an electrode needle to the probe pad electrode and inputting a signal. Almost the same measurement result as when a signal is input to the electrode can be obtained. As a result, it is possible to measure the frequency characteristics of the insertion loss of the surface acoustic wave element before mounting without damaging the mounting pad electrode by the electrode needle, thereby reducing the bonding failure between the mounting pad electrode and the mounting substrate. Yield can be improved.

Note that one or more concave regions may be formed in the periphery of the pad electrode portion in plan view.
According to this configuration, the recessed portion region having a recessed shape can also act as a positioning marker for alignment, so in a bump forming process or a wire bonding process for forming a bump for bonding to a mounting substrate. The positioning accuracy by the sensor used can be improved. As a result, bumps, wire bonding, and the like can be formed almost as designed, so that the production yield of the surface acoustic wave element can be further improved.

In addition to arranging a plurality of concave portions in the periphery of the pad electrode portion, for example, it is arranged between the probe pad electrode and the mounting pad electrode, or the center of the probe pad electrode and the mounting pad electrode is arranged. Or can be placed on a line that passes through.
In addition, the concave portion region absorbs a force in a direction parallel to the main surface of the piezoelectric substrate. For this reason, when the concave portion region is provided in the vicinity of the probe pad electrode, the concave portion region can absorb the stress applied when the electrode needle is applied. Thereby, when an electrode needle is applied to the probe pad electrode, stress due to the application of the electrode needle is not easily transmitted to the mounting pad electrode, and therefore the mounting pad electrode is rarely damaged. Therefore, the durability of the surface acoustic wave element can be enhanced without weakening the bonding with the mounting substrate.

  In addition, it is preferable that the film thickness of the said protective film exists in the range of 5 nm-2.5 micrometers. As a result, the various electrode patterns formed on the main surface of the piezoelectric substrate 9 are protected from external factors such as conductive foreign matter and moisture as when the thickness of the protective film is less than 5 nm. The problem of being unable to do so can be solved. Further, as in the case where the protective film is formed in a thickness exceeding 2.5 μm, the protective film formation process takes a long time and does not become a practical process. The problem can be solved.

Further, the probe pad electrodes exposed by the window portion preferably has an area ranging from 5000 .mu.m ² of 20000μm ^2. As a result, it is possible to solve the problem that the electrode needle is difficult to hit, as in the case where the area is less than 5000 μm ² . On the other hand, since it has a shape that is not exposed beyond the region necessary for measuring the frequency characteristics of the insertion loss of the surface acoustic wave element, such as when having an area exceeding 20000 μm ² , when forming various electrode patterns, For example, the problem that the probe pad electrode corrodes due to the influence of residual chlorine in the etching process can be solved. For this reason, the corrosion region hardly spreads on the mounting pad electrode provided along with the probe pad electrode. As a result, it is possible to reduce defects in the bonding between the mounting pad electrode and the bump connection body on the mounting substrate and in the wire bonding, and as a result, the reliability after mounting the surface acoustic wave element is improved. Can do.

  A method of manufacturing a surface acoustic wave element for achieving the above object comprises preparing a piezoelectric substrate, an excitation electrode for exciting a surface acoustic wave on a main surface of the piezoelectric substrate, and a pad electrode connected to the excitation electrode. And a protective film is formed on the excitation electrode and the pad electrode part. An electrode needle for inputting a signal is applied to the pad electrode part by removing a part of the protective film. Forming two window portions each functioning as a probe pad electrode for contact and a mounting pad electrode for connecting to a mounting substrate, etching the protective film while contacting an electrode needle to the pad electrode portion, By measuring the frequency characteristics of the surface acoustic wave element, when the desired frequency characteristics are reached, or before the desired frequency characteristics are reached, the etching is terminated and a protective film having a desired thickness is formed. is there.

According to this method, a desired frequency characteristic can be approximated in the manufacturing process of the surface acoustic wave element.
When measuring the frequency characteristics of the insertion loss of a surface acoustic wave device, connect the probe pad electrode to the probe pad electrode by using a device such as a network analyzer to measure the frequency characteristics of the insertion loss. The frequency characteristic of the insertion loss of the excitation electrode is measured. At this time, the protective film formed on the surface acoustic wave element can be etched to a suitable thickness, and a surface acoustic wave element having a desired frequency characteristic can be obtained. Thereby, manufacturing efficiency can be made high and the manufacturing method of the surface acoustic wave element excellent in reliability can be provided.

Hereinafter, the surface acoustic wave element of the present invention will be described in detail with reference to the accompanying drawings, taking a resonator type surface acoustic wave element as an example.
In addition, in drawing demonstrated below, the same code | symbol shall be attached | subjected to the same structure.
In addition, the size of each electrode, the distance between the electrodes, the number of electrode fingers, the interval, and the like are schematically illustrated for explanation.

FIG. 1 is a plan view of a main surface of a surface acoustic wave device according to an embodiment of the present invention.
In the present specification, the “main surface” is the surface of the plate-like piezoelectric substrate 9 and means an electrode forming surface on which various electrode patterns such as the excitation electrode 2 and the reflector electrode 8 are formed.
The surface acoustic wave element 1 includes a piezoelectric substrate 9, a comb-like excitation electrode 2 formed on the piezoelectric substrate 9, and a reflector electrode 8 (hereinafter, referred to as a propagation direction of the excited surface acoustic wave). And a pad electrode portion 4 provided on the main surface of the surface acoustic wave element 1.

The piezoelectric substrate 9 is formed of a material having a large pyroelectric property such as a lithium tantalate single crystal, a lithium niobate single crystal, a lithium single crystal, or a lithium tetraborate single crystal. Thereby, the piezoelectric substrate 9 can increase the electromechanical coupling coefficient and decrease the frequency temperature coefficient.
In addition, the piezoelectric substrate 9 may be obtained by reducing oxygen or dissolving a metal substance such as Fe in these piezoelectric single crystal materials. By performing these processes, pyroelectricity due to the piezoelectric substrate 9 can be suppressed. Thereby, pyroelectric breakdown with respect to the excitation electrode 2 and the reflector 8 formed with fine electrode fingers can be reduced, and as a result, the reliability of the surface acoustic wave element 1 can be improved satisfactorily.

  The thickness of the piezoelectric substrate 9 is preferably about 0.1 to 0.5 mm. Therefore, the piezoelectric substrate 9 does not become brittle as when the thickness is less than 0.1 mm, and conversely, when the thickness is greater than 0.5 mm. The material cost does not increase, and the dimension of the surface acoustic wave element 1 does not increase due to the increase in the thickness of the piezoelectric substrate 9.

  Various electrode patterns including the excitation electrode 2 and the reflector 8 of the surface acoustic wave element 1 are formed on the main surface of the piezoelectric substrate 9 by sputtering, vapor deposition, plating, or CVD (Chemical Vapor Deposition). And a metal material such as Al or Al alloy (for example, Al—Cu type or Al—Ti type). By setting the thicknesses of the various electrode patterns to about 0.1 to 0.5 μm, it is possible to excite surface acoustic waves satisfactorily and obtain suitable characteristics.

The excitation electrode 2 is connected to a pad electrode portion 4 for connecting to an external terminal via a wiring electrode. The pad electrode portion 4 is formed in substantially the same process as the excitation electrode 2 and the reflector 8. That is, it is formed on the main surface of the piezoelectric substrate 9 with a metal material such as Al or an Al alloy by using a thin film forming method such as sputtering, vapor deposition, plating, or CVD.
A semiconductor such as Si, SiO ₂ , SiN _x , or Al ₂ O _{3 is} formed on various electrode patterns such as the pad electrode portion 4, the excitation electrode 2, and the reflector 8 by using a thin film forming method such as a CVD method or a vapor deposition method. A protective film 3 made of a material or an insulator material is formed. Thereby, with respect to the various electrode patterns formed on the main surface of the surface acoustic wave element 1, it is possible to improve the prevention of energization by conductive foreign substances and the power durability. This protective film 3 can also adjust the center frequency by the mass effect by this film thickness.

  The protective film 3 preferably has a thickness in the range of 5 nm to 2.5 μm. As a result, the various electrode patterns formed on the main surface of the piezoelectric substrate 9 can be removed from external factors such as conductive foreign matter and moisture as when the thickness of the protective film 3 is less than 5 nm. The problem that it becomes impossible to protect can be solved. Further, as in the case where the thickness of the protective film 3 is formed in a range exceeding 2.5 μm, in the film forming process of the protective film 3, it takes a long time to form the protective film 3, and the practical process. The problem of not becoming can be solved.

  The protective film 3 on the pad electrode part 4 formed on the main surface of the piezoelectric substrate 9 is provided with a window part through which the excitation electrode 2 and the metal thin film forming the pad electrode 4 are exposed. The window portion forms a probe pad electrode 41 provided for contact with the probe needle and a mounting pad electrode 42 connected via a bump for electrical connection with the mounting substrate. . The configuration of the pad electrode portion 4 will be described later.

A method for mounting the surface acoustic wave element 1 on the mounting substrate will be described below.
The surface acoustic wave element 1 has a rectangular frame-shaped annular electrode (not shown) on the main surface of the piezoelectric substrate 9 so as to surround various electrode patterns such as the excitation electrode 2, the reflector 8 and the pad electrode portion 4. Is formed.
A mounting substrate (not shown) for mounting the surface acoustic wave element 1 is disposed at a position facing the mounting pad electrode 42 included in the pad electrode portion 4 formed on the main surface of the piezoelectric substrate 9. Predetermined conductor pads (not shown) are provided. The mounting substrate is provided with a predetermined annular conductor (not shown) at a position facing the annular electrode of the piezoelectric substrate 9.

  The surface acoustic wave element 1 is mounted and fixed face-down with the main surface of the piezoelectric substrate 9 facing the mounting substrate. Then, using a meltable metal material such as solder, the predetermined conductor pad on the mounting substrate and the mounting pad electrode 42 are electrically and mechanically joined, and the predetermined annular conductor on the mounting substrate The annular electrode formed on the piezoelectric substrate 9 is mechanically joined. Various electrode patterns such as the excitation electrode 2 and the reflector 8 of the surface acoustic wave element 1 do not come into contact with the outside air due to the space formed by the main surface of the piezoelectric substrate 9, the mounting surface of the mounting substrate, and the annular electrode. It is sealed.

In addition, the mounting structure of the surface acoustic wave element 1 of the present invention is not limited to the aspect of the sealing structure surrounded by the annular electrode described above.
Below, the structure of the pad electrode part 4 is demonstrated.
2A is an enlarged view of the pad electrode portion 4 of the surface acoustic wave element 1, and FIG. 2B is a cross-sectional view taken along the line AA in FIGS. 1 and 2A.

  In the surface acoustic wave element 1, as shown in FIG. 2B, the protective film 3 is formed on the main surface of the piezoelectric substrate 9 including a part of the pad electrode portion 4. The protective film 3 is formed to protect various electrode patterns formed on the main surface of the piezoelectric substrate 9 and to adjust the frequency due to the mass effect of the protective film 3. As shown in the figure, the pad electrode portion 4 is formed on the same metal thin film from the window portion from which the protective film 3 is formed on the metal thin film made of a metal material such as Al, and the protective film 3 is removed. The probe pad electrode 41 and the mounting pad electrode 42 have a shape exposed separately.

Incidentally, the probe pad electrode 41 preferably has an area ranging from 5000 .mu.m ² of 20000μm ^2. Thereby, it is possible to solve the problem that it is difficult to apply the probe needle as in the case where the area is less than 5000 μm ² . On the other hand, since it has a shape that is not exposed beyond the region necessary for the measurement of the frequency characteristics of the insertion loss of the surface acoustic wave device 1 when it has an area exceeding 20000 μm ² , For example, the problem that the probe pad electrode 41 is corroded by the influence of residual chlorine in the dry etching process can be solved. For this reason, the corrosion area hardly spreads on the mounting pad electrode 42 provided along with the probe pad electrode 41. As a result, it is possible to reduce defects in the connection between the mounting pad electrode 42 and the bump connection body on the mounting substrate and the connection in the wire bonding, and as a result, the reliability after mounting the surface acoustic wave element is improved. be able to.

The probe pad electrode 41 is preferably rectangular. In consideration of the arrangement of the entire surface acoustic wave element, when the probe pad electrode 41 is formed in a rectangular shape, the size of the surface acoustic wave element can be reduced.
Below, the structure of the surface acoustic wave element of other embodiment is demonstrated.
FIG. 3 is a plan view of the main surface of a surface acoustic wave device 1a according to another embodiment of the present invention. FIG. 4 is an enlarged view of the pad electrode portion 4a of FIG.

In the surface acoustic wave element 1a, the excitation electrode 2, the reflector 8, and the pad electrode portion 4a are formed on the main surface of the piezoelectric substrate 9, as in the surface acoustic wave element 1 shown in FIG.
In the pad electrode portion 4a, a probe pad electrode 41 connected to the excitation electrode 2 and a mounting pad electrode 42 provided adjacent to the probe pad electrode 41 are formed through a metal thin film.

In addition to the above, a concave portion region 43 is formed in the peripheral portion of the pad electrode portion 4a as shown in FIG.
Since the recessed portion region 43 can also act as a positioning marker for alignment, it improves the positioning accuracy of a sensor used in a bump forming process or a wire bonding process for forming a bump for bonding to a mounting substrate. be able to. As a result, bumps, wire bonding, and the like can be formed almost as designed, so that the production yield of the surface acoustic wave device 1a can be further improved.

Further, as shown in FIG. 4, a plurality of the concave portion regions 43 are arranged around the pad electrode portion 4a. However, in addition to this arrangement, the concave portion region 43 is arranged between the probe pad electrode 41 and the mounting pad electrode. Or arranged on a line passing through the center of the probe pad electrode 41 and the mounting pad electrode 42.
Further, since the concave shape has a shape that easily absorbs the force parallel to the main surface of the piezoelectric substrate 9, the concave portion region 43 is provided in the peripheral portion of the probe pad electrode 41. The concave portion region 43 can absorb the stress applied when the probe needle is applied. Thereby, when the probe needle is applied to the probe pad electrode 41, the stress due to the application of the probe needle is difficult to be transmitted to the mounting pad electrode 42, so that the mounting pad electrode 42 is hardly damaged, and as a result, the mounting substrate The durability of the surface acoustic wave element 1a can be increased without weakening the bonding with the.

In addition, although the recessed part area | region 43 as a positioning marker has a recessed shape with respect to the main surface of the piezoelectric substrate 9, devices, such as a sensor, like a concavo-convex shape are recognized besides this shape. Any shape can be used.
FIG. 5A is a plan view showing the surface acoustic wave element 1 formed on the mother substrate 19, and FIG. 5B is a cross-sectional view taken along the line BB in FIG. 5A on the mother substrate 19. It is sectional drawing in a line.

The mother substrate 19 is a substrate which is formed of a pyroelectric piezoelectric substrate and on which a plurality of surface acoustic wave elements 1 having various electrode patterns such as the excitation electrodes 2 formed on the mother substrate 19 are formed. .
In each surface acoustic wave element 1 formed on the mother substrate 19, as shown in FIG. 5B, the protective film 3 on the metal thin film that forms the pad electrode portion 4 is removed using an etching method. Yes. A probe pad electrode 41 (see FIG. 1) for contact with the probe needle 11 is formed.

  The measurement of the frequency characteristics of the insertion loss of the surface acoustic wave element 1 formed on the mother substrate 19 is first performed as shown in FIG. 5B, with a plurality of surface acoustic wave elements formed on the mother substrate 19. The probe needle 11 is applied to the probe pad electrode 41 using one of the samples as a sample. Then, the frequency characteristic of the insertion loss of the surface acoustic wave device 1 connected to the probe pad electrode 41 is measured by using a device that measures the frequency characteristic of the insertion loss, such as a network analyzer. While performing this measurement, the protective film 3 formed on the mother substrate 19 is etched to a suitable film thickness until the surface acoustic wave element 1 has a desired frequency characteristic. Thereby, the surface acoustic wave element 1 having a desired frequency characteristic can be obtained by dicing (cutting) along the dicing line L as shown in FIG.

  As described above, the surface acoustic wave element 1 is formed on the surface acoustic wave element 1 by applying the probe needle 11 to form the probe pad electrode 41 as a pad electrode for evaluation measurement for inputting a signal. For example, the degree of etching of the protective film 3 can be adjusted while measuring the frequency characteristics of the insertion loss. Further, the frequency generated in the surface acoustic wave element 1 that occurs during the production of the surface acoustic wave element 1 by adjusting the etching amount of the film thickness of the protective film 3 while measuring the probe while etching the protective film 3 Variations in characteristics can be corrected, and as a result, the yield of the surface acoustic wave element 1 can be improved.

  Further, since the probe pad electrode 41 and the mounting pad electrode 42 are electrically connected, a signal is input to the mounting pad electrode 42 by inputting the signal by applying the probe needle 11 to the probe pad electrode 41. As a result, it is possible to obtain the measurement result of the frequency characteristic of the insertion loss which is almost the same as that of the case. Accordingly, the frequency characteristics of the insertion loss of the surface acoustic wave element 1 can be measured before mounting without leaving a probe mark due to the probe needle 11 on the mounting pad electrode 42. Therefore, the mounting pad electrode 42 and the mounting substrate It is possible to reduce defects in bonding with the conductor pads and improve the yield.

  Furthermore, the probe pad electrode 41 has a shape that is not exposed beyond the region necessary for measuring the frequency characteristics of the insertion loss of the surface acoustic wave element 1. For this reason, the problem that the probe pad electrode 41 corrodes due to the influence of residual chlorine in, for example, a dry etching process when various electrode patterns are formed can be reduced. For this reason, the corrosion area hardly spreads on the mounting pad electrode 42 provided along with the probe pad electrode 41. Thereby, it is possible to reduce defects in the connection between the mounting pad electrode 42 and the bump connection body on the mounting substrate and the connection in wire bonding. Therefore, the reliability after mounting the surface acoustic wave element 1 can be improved.

In addition, various design changes can be made within the scope of matters described in the claims.
Below, each process which manufactures the surface acoustic wave element 1 is demonstrated, measuring the frequency characteristic of the insertion loss of the surface acoustic wave element 1. FIG.

FIGS. 6A to 6G are views for explaining each process of manufacturing the surface acoustic wave device 1 while measuring the frequency characteristics of the insertion loss of the excitation electrode 2 through the probe pad electrode 41. FIG. It is sectional drawing in the BB line of a).
The illustrated white arrow indicates the direction of etching.
In the manufacturing process of the surface acoustic wave device 1 shown in FIG. 6, as shown in FIG. 1, a plurality of various electrode patterns including the excitation electrode 2 and the probe pad electrode 41 are formed on the mother substrate 19 in a lattice shape. .

First, as the mother substrate 19 formed of the piezoelectric substrate of the surface acoustic wave element 1, a 38.7 ° Y-cut X-propagation LiTaO ₃ single crystal was used. An Al alloy metal thin film was formed on the main surface of the mother substrate 19 by sputtering. Then, various electrode patterns such as the excitation electrode 2, the pad electrode portion 4, and the reflector 8 (not shown in FIG. 6) are patterned by using a photolithography technique, and Cl ₂ , BCl _3, and N ₂ are reacted with the reaction gas. The shapes of these various electrode patterns were formed using a dry etching method that adjusts etching conditions such as gas flow rate, pressure, and applied power.

Next, as shown in FIG. 6A, the protective film 3 was formed on the surface of the mother substrate 19 on which various electrode patterns were formed with SiO ₂ by using the CVD method.
Next, as shown in FIG. 6B, a photoresist film 5 was formed on the protective film 3 of the mother substrate 19 using a spin coater. Thereafter, as shown in FIG. 6C, development is performed using a photolithography method to remove a part of the photoresist film 5 formed on the pad electrode portion 4 and to form two windows. did.

Next, as shown in FIG. 6D, the protective film 3 exposed from the two windows from which the photoresist film 5 was removed was etched and removed using a dry etching method. Then, in one pad electrode portion 4, a predetermined portion of the metal thin film on which the probe pad electrode 41 and the mounting pad electrode 42 are formed is exposed.
Next, as shown in FIG. 6E, the photoresist film 5 covering the protective film 3 was removed using a lift-off method. Then, by applying the probe needle 11 to the probe pad electrode 41 and inputting a signal from the probe needle 11, while measuring the frequency characteristic of the insertion loss of the excitation electrode 2 during the etching process of the protective film 3, The protective film 3 formed on was etched.

Then, as shown in FIG. 6 (f), when the signal is input from the probe needle 11 and the frequency characteristic of the insertion loss having the center frequency of the desired pass band is obtained, the etching process of the protective film 3 is finished. . Then, as shown in FIG. 6G, the mother substrate 19 was diced along the dicing line L, whereby the surface acoustic wave element 1 was manufactured.
In this way, the surface acoustic wave element 1 could be manufactured while adjusting the etching amount of the protective film 3 according to the frequency characteristics of the insertion loss of the surface acoustic wave element 1 formed on the mother substrate 19. . This makes it possible to correct the center frequency of the pass band due to slight variations occurring in each cut out mother board 19, and to bring the surface acoustic wave element 1 closer to have a desired frequency characteristic, thereby improving the product yield. I was able to improve.

  As shown in FIGS. 3 and 4, by providing a concave portion region 43 in the peripheral portion of the pad electrode portion 4, the minimum portion necessary for measuring the frequency characteristics of the insertion loss of the surface acoustic wave element 1 is exceeded. Even if the probe pad electrode 41 is not exposed, the probe needle 11 can be applied to the probe pad electrode 41 almost accurately. As a result, the area of the probe pad electrode 41 is not increased more than necessary, so that the mounting pad electrode 42 is corroded due to the corrosion of the probe pad electrode 41 due to the influence of residual chlorine in the dry etching process during electrode pattern formation. Corrosion can be reduced.

  In addition, after measuring the frequency characteristics of the insertion loss before forming the protective film 3, as shown in FIG. 6A, the film thickness of the protective film 3 is slightly thicker than the film thickness for obtaining the desired frequency characteristic. After the formation, the thickness of the protective film 3 can be reduced little by little while measuring the frequency characteristic of the insertion loss of the surface acoustic wave element 1 by reducing the etching speed of the film thickness of the protective film 3 by etching. Can be fine tuned. As a result, the center frequency can be increased to the high frequency side almost certainly, so that the surface acoustic wave device 1 having a desired frequency characteristic can be obtained almost certainly. For this reason, it can prevent that the film thickness of the protective film 3 becomes too thin rather than the film thickness which obtains a predetermined frequency characteristic, and it becomes impossible to adjust a frequency, and the yield of a manufacturing process improves.

It is a top view of the main surface of the surface acoustic wave element concerning one embodiment of the present invention. (A) is an enlarged view of the pad electrode part of a surface acoustic wave element, (b) is sectional drawing of the AA line in FIG. 1 and FIG. 2 (a). It is a top view of the main surface of the surface acoustic wave element of other embodiments concerning the present invention. It is an enlarged view of the pad electrode part of FIG. (A) is a top view for showing the surface acoustic wave element formed on a mother board, (b) is a sectional view in the BB line of (a) on a mother board. FIGS. 5A to 5G are cross-sectional views taken along line BB in FIG. 5A for explaining a method of manufacturing a surface acoustic wave element while measuring the frequency characteristics of the insertion loss of the excitation electrode through the probe pad electrode. It is sectional drawing in a line.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a Surface acoustic wave element 2 Excitation electrode 3 Protective film 4, 4a Pad electrode part 41 Probe pad electrode 42 Mounting pad electrode 43 Recessed part area | region 8 Reflector electrode 9 Piezoelectric substrate 11 Probe needle (electrode needle)

Claims (5)

A surface acoustic wave element that excites a surface acoustic wave by an excitation electrode formed on a main surface of a piezoelectric substrate,
The excitation electrode having comb-like electrode fingers;
A pad electrode portion connected to the excitation electrode;
A protective film formed on the excitation electrode and the pad electrode,
The pad electrode portion is formed with two windows from which part of the protective film is removed and the electrode is exposed,
Each of the two windows is
A probe pad electrode for contacting an electrode needle for inputting a signal; and
A surface acoustic wave element that functions as a mounting pad electrode for connecting to a mounting substrate.   The surface acoustic wave device according to claim 1, wherein one or more concave regions are formed in a plan view in a peripheral portion of the pad electrode portion.   The surface acoustic wave device according to claim 1, wherein the protective film has a thickness in a range of 5 nm to 2.5 μm. 4. The surface acoustic wave device according to claim 1, wherein the probe pad electrode exposed by the window has an area in a range of 5000 μm ² to 20000 μm ^{2. 5} . Prepare a piezoelectric substrate,
Forming on the main surface on the piezoelectric substrate an excitation electrode for exciting a surface acoustic wave, and a pad electrode portion connected to the excitation electrode,
Forming a protective film on the excitation electrode and the pad electrode portion;
In the pad electrode portion, a part of the protective film is removed, and two probe pads each functioning as a probe pad electrode for contacting an electrode needle for inputting a signal and a mounting pad electrode for connecting to a mounting substrate. Forming windows,
Etching the protective film while contacting the electrode needle to the pad electrode part,
Measure the frequency characteristics of the surface acoustic wave element,
A method for manufacturing a surface acoustic wave device, wherein the etching is terminated when a desired frequency characteristic is reached or before the desired frequency characteristic is reached, and a protective film having a desired thickness is formed.

Images