JP4339969B2 - Manufacturing method of surface acoustic wave device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a surface acoustic NamiSo location such as a surface acoustic wave filters used in mobile communication devices such as mobile phones.
[0002]
BACKGROUND OF THE INVENTION
In recent years, many surface acoustic wave devices have been used as constituent elements such as filters, delay lines, and transmitters of electronic devices that use radio waves. In particular, surface acoustic wave filters that are small, lightweight, and have high steep cut-off performance as filters have come to be widely used as RF stage and IF stage filters for mobile terminal devices in the mobile communication field, and have low loss. There is also a demand for a surface acoustic wave filter having excellent attenuation characteristics outside the passband, high attenuation characteristics, and a wide bandwidth. With such an increase in demand, there is a demand for a method that can be manufactured with high performance and high yield.
[0003]
Conventionally, a surface acoustic wave filter is manufactured by sequentially performing the main steps shown in FIG. That is, a wafer process for forming fine electrodes on a piezoelectric substrate, wafer probing for selecting characteristics in the wafer state, a mounting process for cutting (dicing) the chip, mounting it on a ceramic package, and wire bonding, and a finished product It consists of characteristic inspection.
[0004]
Further, in the surface acoustic wave filter, in order to prevent electrostatic breakdown of fine electrodes due to the pyroelectric effect or electrostatic charging of the piezoelectric substrate, as shown in FIG. 11, the grounding electrode connected to the excitation electrode 56 on the wafer J is used. It is conceivable to connect the conductor pattern 53 to the dicing line 51 with a thin line 52. When the width A of the thin wire 52 is normalized by the electrode film thickness B, the A / B is set to about 25 or less, thereby preventing the resistance from becoming extremely large, thereby reducing the characteristics of the wafer state and after mounting the package after separation. Make it possible to correlate with characteristics.
[0005]
However, as shown in FIG. 12, if there are uncut portions 55 of the dicing lines 51 in the dicing step, the package mounting is performed by the grounded conductor pattern 53 of the piezoelectric substrate 57 and the uncut portions 55 of the dicing lines 51 that are individually separated. After that, there was a problem that the potential of the grounding electrode became constant and the high frequency characteristics deteriorated.
[0006]
The alignment between the dicing line 51 and the dicing blade (rotating blade) by the dicing apparatus is made by visual observation using a CCD camera, and the alignment error at this time is caused by the absence of the alignment mark. The uncut portion 55 is generated.
[0007]
As a result, as shown in FIG. 8, characteristic deterioration such as insufficient attenuation particularly in a high frequency region may be caused. In general, a ladder-type surface acoustic wave filter passes through an inductor 8 included in a bonding wire before conducting on a package, as shown by an equivalent circuit in FIG. In FIG. 9, 6 is a capacitive component, 7 is a surface acoustic wave resonator, 9 is an input terminal, 10 is an output terminal, 16 is a castellation of a package (such as a through-hole connecting the outer wall surface in a semi-cylindrical shape. For connecting the electrodes of each layer.)
[0008]
On the other hand, if the grounding conductor pattern is conductive on the chip, it becomes completely different in terms of an equivalent circuit as shown in FIG. In FIG. 10, the same members as those in FIG.
[0009]
In the ground-separated ladder circuit as shown in FIG. 9, the effect of the bonding wire inductor 8 entering the parallel resonator in series acts effectively, and between the capacitance component of the IDT electrode and the bonding wire inductor L. Resonance occurs, a resonance pole appears in the high frequency region, and attenuation is guaranteed. On the other hand, when the ground (grounding conductor pattern) is conductive as shown in FIG. 10, this influence becomes extremely small, and the position of the pole is lowered to the low frequency side.
[0010]
When such a surface acoustic wave filter is used in a mobile phone or the like, high-order noise generated in the IC cannot be suppressed, and thus the call quality is deteriorated. For this reason, the obtained chip is usually a defective product in the mounting process, which causes a decrease in yield.
[0011]
As one of the methods for preventing such uncut dicing lines, there is known a method of increasing the thickness of the blade and taking a thicker and larger cutting margin. Therefore, there is a problem that the effective use area in the chip is reduced, and for this reason, the number of chips that can be taken in one wafer is reduced.
[0012]
In addition, a method has been proposed in which grounding conductor patterns having serpentine ends are connected directly and dicing is performed at this location. Then, an inductor component enters the ground electrode, and the characteristics at the time of the wafer probe change, and there is a problem that it is difficult to correlate the characteristics with the finished product (see, for example, JP-A-11-127051).
[0013]
That is, when the inductance enters the ground electrode, the attenuation curve of the high-frequency portion changes. However, in the wafer state, the inductance is usually small, and the amount of high-frequency attenuation changes when the inductance of the bonding wire enters after packaging. By predicting this, inspection in the wafer state becomes possible. However, if the wafer already has a frequency characteristic that is greatly affected by the inductance, the change is further increased after the package is mounted, and it becomes difficult to predict the characteristic after the package is mounted. As a result, it is difficult to predict the quality after package mounting in advance in the wafer state and check the non-defective product / defective product.
[0014]
Therefore, the present invention enables highly accurate alignment between the dicing blade and the wafer in the dicing process, and eliminates uncut uncut dicing lines, thereby preventing a high yield with no deterioration in attenuation in the high frequency region. and to provide an excellent surface acoustic NamiSo location method of manufacturing.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, a method for manufacturing a surface acoustic wave device according to the present invention includes a first surface acoustic wave element region having a first grounding conductor pattern, and adjacent to the first surface acoustic wave element region. And a second surface acoustic wave element region having a second grounding conductor pattern, and a linear line for dicing that separates the first surface acoustic wave element region and the second surface acoustic wave element region. A method of manufacturing a surface acoustic wave device, comprising: a step of preparing a piezoelectric wafer including a pattern; and a step of pre-cutting the piezoelectric wafer along a linear pattern with a dicing blade. The first grounding conductor pattern has a first extending region extending toward the second surface acoustic wave element region so as to be connected to the linear pattern. The first extending region has a periodic shape, and the second grounding conductor pattern extends to the first surface acoustic wave element region so as to be connected to the linear pattern. together with the extending region has a periodic structure that extended region of the second consists of the same shape as the first extension region, before after the step of performing Kipu re-cut, the precut portion of wherein the first extension region of the periodic structure remaining on both sides and said second extension region of the periodic structure further comprises a step of aligning the dicing blade to be identical.
[0016]
In the method for manufacturing a surface acoustic wave device according to the present invention, the first extending region has a portion that enters the second surface acoustic wave element region, and the second extending region is the first extending region. It has the part which penetrates to a surface acoustic wave element area | region.
[0017]
The surface acoustic wave device manufacturing method of the present invention is characterized in that the periodic shape of the first extending region is stepped .
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0019]
FIG. 1 is a plan view schematically showing a surface of the surface acoustic wave device (ladder type surface acoustic wave filter) S according to the present invention except for a cover, and FIG. 2 shows a surface acoustic wave element constituting the surface acoustic wave device S. The electrode pattern of K is typically shown. In FIG. 2, a part of the grounding conductor pattern is omitted for simplicity.
[0020]
The surface acoustic wave device S is a ceramic package 20 in which a surface acoustic wave element K is accommodated. The surface acoustic wave element K is connected to an excitation electrode 15 on a piezoelectric substrate 21 and the excitation electrode 15. The grounding conductor pattern 3 and the like are arranged.
[0021]
Here, on the piezoelectric substrate 21, a plurality of surface acoustic wave resonators 17 including excitation electrodes 14 and reflectors 15 and a grounding conductor pattern 3 connected to each surface acoustic wave resonator 17 are arranged. At the same time, each grounding conductor pattern 3 is formed so as to reach the side end of the piezoelectric substrate 21, and the side end of the piezoelectric substrate 21 is cut along the outer shape of each grounding conductor pattern 3. Note that 9 is an input terminal, 10 is an output terminal, and 11 is a ground terminal formed on the package 20. Further, the upper surface 20a of the package 20 is hermetically sealed with a lid (not shown).
[0022]
In addition, the grounding conductor patterns 13 that are individually divided are connected to the electrode pads 11 formed on the package 20 by the bonding wires 12, so that the grounding conductors are electrically connected in the package 20.
[0023]
Note that the grounding conductor patterns 3 connected to the parallel resonators are not combined into one, but are separately distributed and connected to the ground terminal 11 on the package 20 side. This is done to control the pole of the internal attenuation.
[0024]
Next, a method for manufacturing the surface acoustic wave element K will be described.
[0025]
As shown in FIGS. 3 and 4, in the manufacturing method of the present invention, a plurality of surface acoustic wave element regions in which excitation electrodes 14 and grounding conductor patterns 3 connected thereto are arranged on a piezoelectric wafer W are provided. The piezoelectric wafer W is separated into individual surface acoustic wave element regions, and a plurality of surface acoustic wave devices S are obtained.
[0026]
Specifically, first, as shown in FIG. 3, a plurality of surface acoustic wave element regions (regions including the excitation electrodes 14) and dicing lines that divide individual surface acoustic wave element regions on the piezoelectric wafer W. The step of forming the pattern 1 so that a part of the grounding conductor pattern 3 in each surface acoustic wave element region is connected to the linear pattern 1 is performed.
[0027]
Next, a process of cutting the piezoelectric wafer W along the linear pattern 1 is performed using the connecting portion 2 between the linear pattern 1 and the grounding conductor pattern 3 as a marker. As a result, as shown in FIG. 4, the desired surface acoustic wave device S can be obtained by being divided into the respective surface acoustic wave element regions.
[0028]
Here, a region extending from each grounding conductor pattern with respect to the dicing wire 1 is formed in, for example, a stepped step. In this case, dicing (pre-cut) for one line is first performed, and the stepped portion is confirmed with a CCD camera. By this dicing, a normal dicing line is cut off, but the stepped portion remains after dicing and can be confirmed by a CCD camera. By re-aligning so that the step shapes remaining on both sides of the dicing mark are the same, the center of the dicing line can be cut, and cutting can be performed accurately and reliably. If further accuracy is required, this step is made small and fine, the CCD camera and the display are made high definition, and the design of this part is changed according to the required dicing accuracy.
[0029]
In FIG. 4, the width d1 (width / thickness of the pattern) of the narrow portion, the width d2 of the wide portion, and the length of the extension portion of the extended portion of the grounding conductor pattern 3 normalized by the pattern thickness. The relationship of d3 is as follows. That is, (1) d2 / 2>d1> 250, (2) d2> 600, and (3) d3> 1300. This is because an inductance is generated in the ground if the width is less than the condition of (1) and (2), and sufficient high-frequency attenuation cannot be secured, and a capacitance is generated in the ground if the width is less than the condition of (3). This is because a sufficient amount of high-frequency attenuation cannot be ensured.
[0030]
A part of the grounding conductor pattern 3 (connecting portion 2) led out to the side end portion of each separated piezoelectric substrate 31 has a periodic shape. For example, FIG. By providing a stepped step on one side of the grounding conductor pattern 3 as in a), it is possible to know how far the target has deviated from the target by counting the number of steps. Further, as shown in FIG. 5B, the number of steps can be counted more easily than in FIG. 5A by providing stepped steps on both sides. Moreover, as shown in FIG.5 (c), it can also make it easy to distinguish by lengthening a projection part. Further, as shown in FIG. 5D, unevenness may be provided on both sides of the grounding conductor pattern 3. In addition, as shown in FIG. 5E, it is easy to detect the angular deviation by providing triangular irregularities on both sides. Further, as shown in FIG. 5 (f), a part of the grounding conductor pattern 3 may be triangular (inclined), and irregularities may be provided in the middle thereof. Furthermore, as shown in FIG. 5 (g), it is possible to make the protrusion part into an arc shape, and by making it curved like this, it can withstand the water flow during dicing and be resistant to peeling due to this. it can. Thus, a part of the grounding conductor pattern 3 is a characteristic pattern that can be used instead of the scale.
[0031]
Thus, according to the present invention, since the ground portion is always separated, a pole is formed by the inductor of the bonding wire that is serially connected to the parallel resonator, and a problem such as deterioration of attenuation in the high frequency region is prevented as much as possible. be able to. In addition, since the grounding conductor patterns are connected in a wafer state, electrode destruction due to static electricity generated during electrode patterning does not occur.
[0032]
【Example】
Next, an example in which a ladder-type surface acoustic wave filter according to the present invention is prototyped will be described.
[0033]
A fine electrode pattern made of an Al (98 wt.%)-Cu (2 wt.%) Alloy film was formed on a substrate made of 42 ° Y-cut LiTaO ₃ single crystal. For pattern production, photolithography was performed using a reduction projection exposure machine (stepper) and an RIE (Reactive Ion Etching) apparatus. First, the substrate material was subjected to ultrasonic cleaning with acetone / IPA or the like to remove organic components. Next, the substrate was sufficiently dried by a clean oven, and then an electrode was formed.
[0034]
For the electrode film formation, a sputtering apparatus was used to form the material made of the Al—Cu alloy. The electrode film thickness was about 2000 mm. Next, a resist was spin-coated to a thickness of about 0.5 μm, and desired patterning was performed by a reduction projection exposure apparatus (stepper). The stepper requires a reticle as a patterning original. However, since the image is reduced and projected to 1/5 by the optical system of the stepper itself, the size may be 5 times the actual pattern. For this reason, on the contrary, a resolution five times higher than that of the conventional contact aligner can be obtained.
[0035]
Next, an unnecessary portion of the resist was dissolved with an alkaline developer by a developing device to reveal a desired pattern, and then the Al—Cu electrode was etched by the RIE device to complete the patterning.
[0036]
Thereafter, a protective film is produced. A film of SiO ₂ was formed by a sputtering apparatus, followed by resist patterning by photolithography, and etching of a wire bonding window opening portion by an RIE apparatus or the like to complete a protective film pattern.
[0037]
Next, the substrate was diced along dicing lines and divided into chips. At this time, only two or three pieces were first cut and the alignment was accurately performed to such an extent that the amount of deviation did not reach the step of the present invention. For this reason, there was no uncut portion of the grounding electrode after dicing. Then, each chip was picked up by a die bonding apparatus and adhered to the SMD package with a die bonding resin containing Si resin as a main component. Thereafter, a temperature of about 160 ° C. was applied to dry and cure. The SMD package has a 3 mm square laminated structure. Next, 30 μφ Au wire was ball-bonded on the pad part of the SMD package and the Al pad on the chip, and then the lid was placed on the package and sealed by a sealing machine. The grounding electrode patterns on the chip were separated and wired, and the ground pads on the package were bonded by Au ball bonding.
[0038]
The surface acoustic wave resonator constituting the ladder type surface acoustic wave filter has 40 to 120 pairs of logarithms (1/2 of the number) of IDT electrodes (excitation electrodes) and a crossing width of 10 to 30λ (λ is a surface acoustic wave). The wavelength λ of the surface acoustic wave is different between the series and the parallel, but is approximately 2 μm. Here, the number of reflector electrodes is 20 for both the series resonator and the parallel resonator. The electrode configuration is as shown in FIG. 6, and the same components as those in FIG. Thus, a 2.5-stage T-type including three series resonators and two parallel resonators was used.
[0039]
As shown in FIG. 7, the filter characteristics obtained when a filter having no dicing line not cut using the present invention was obtained. For this measurement, a network analyzer was used to measure S21 as transmission characteristics. A dedicated test fixture was used to measure the filter characteristics.
[0040]
Incidentally, in the case of the electrode pattern in which the dicing line is left uncut as a comparison with the present embodiment, the potential of the grounding conductor pattern becomes the same after dicing, and the filter characteristics are as shown in FIG.
[0041]
As described above, in the embodiment of the present invention, the amount of attenuation is particularly large in a high frequency region of 3 GHz or more, and there is a difference close to 20 dB at the maximum. In addition, when dicing was performed using the electrode pattern of the present invention, the occurrence ratio of insufficient out-of-band attenuation due to uncut dicing lines could be reduced to 0%, which was about 33% in the past. . Furthermore, since the grounding electrodes are connected in the wafer process, discharge is not caused between adjacent patterns or between IDT electrodes even under a temperature rising / falling condition, and electrode destruction can be prevented.
[0042]
【The invention's effect】
As described above, according to the present invention, the dicing blade and the wafer can be aligned with high accuracy in the dicing process, so that there is no uncut dicing line, and therefore there is insufficient attenuation in the high frequency region. It is possible to reduce the characteristic defects due to the high yield.
[0043]
In addition, since the grounding conductor patterns are connected in the wafer process, there is no discharge between adjacent patterns or between excitation electrodes even under elevated temperature conditions, and electrode destruction can be prevented as much as possible. .
[0044]
As a result, a surface acoustic wave device having excellent characteristics and extremely high reliability can be provided.
[Brief description of the drawings]
FIG. 1 is a plan view schematically illustrating an embodiment of a surface acoustic wave device according to the present invention.
FIG. 2 is a plan view schematically showing an electrode pattern configuration of a surface acoustic wave device according to the present invention.
FIG. 3 is a plan view schematically showing a state of a wafer before dicing according to the present invention.
FIG. 4 is a plan view schematically showing a state of a separated piezoelectric substrate after dicing according to the present invention.
FIGS. 5A to 5G are plan views showing examples of extending portions of a grounding conductor pattern according to the present invention. FIG.
FIG. 6 is a plan view schematically showing an electrode pattern configuration of another surface acoustic wave device according to the present invention.
FIG. 7 is a diagram showing a transmission characteristic S21 of the surface acoustic wave filter according to the present invention.
FIG. 8 is a diagram showing a transmission characteristic S21 of a conventional surface acoustic wave filter.
FIG. 9 is an equivalent circuit diagram of a general ladder-type surface acoustic wave filter.
FIG. 10 is an equivalent circuit diagram of a ladder-type surface acoustic wave filter when a dicing line is left uncut.
FIG. 11 is a plan view schematically showing a state of a conventional wafer before dicing.
FIG. 12 is a plan view schematically showing a state of a separated piezoelectric substrate after conventional dicing.
FIG. 13 is a diagram showing a production process of a surface acoustic wave filter.
[Explanation of symbols]
1: Dicing wire 2: Connection portion 3: Grounding conductor pattern 4: Trace after dicing 8: Inductor 9: Input electrode 10: Output electrode 11: Grounding electrode 12: Wire 14: Excitation electrode 15: Reflector 17: Surface acoustic wave resonator 20: package 21, 31: piezoelectric substrate K: surface acoustic wave element S: surface acoustic wave device W: piezoelectric wafer

Claims (3)

A first surface acoustic wave element region having a first grounding conductor pattern, and a second surface acoustic wave element region adjacent to the first surface acoustic wave element region and having a second grounding conductor pattern And a step of preparing a piezoelectric wafer comprising: a linear pattern for dicing that separates the first surface acoustic wave element region and the second surface acoustic wave element region;
Pre-cutting the piezoelectric wafer with a dicing blade along the linear pattern, and a method of manufacturing a surface acoustic wave device,
In the step of preparing the piezoelectric wafer, the first grounding conductor pattern has a first extension region extending toward the second surface acoustic wave element region so as to be connected to the linear pattern. In addition, the first extension region has a periodic shape, and the second grounding conductor pattern extends toward the first surface acoustic wave element region so as to be connected to the linear pattern. Two extending regions, and the second extending region has a periodic shape having the same shape as the first extending region,
Before after the step of performing Kipu re-cut, the precut portion both sides remaining the first extended region of the periodic structure and the second extending region the dicing blade so that the periodic structure is the same for A method for manufacturing a surface acoustic wave device, further comprising the step of performing positioning.   The first extending region has a portion that enters the second surface acoustic wave element region, and the second extending region has a portion that extends to the first surface acoustic wave element region. Item 2. A method for manufacturing a surface acoustic wave device according to Item 1.   The method for manufacturing a surface acoustic wave device according to claim 1, wherein a periodic shape of the first extending region is stepped.

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