JP2011087079A - Surface acoustic wave device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a temperature coefficient of a frequency of a surface acoustic wave device using a propagation substrate of a piezoelectric single crystal. <P>SOLUTION: The surface acoustic wave device has a supporting substrate 1, a substrate 3A of a piezoelectric single crystal, an organic adhesive layer 2 having a thickness of 0.1 to 1.0 μm and bonding the supporting substrate 1 and the propagation substrate 3 made of a piezoelectric single crystal, and a surface acoustic wave filter provided on the propagation substrate 3A. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface acoustic wave element having good frequency temperature characteristics.

  Surface acoustic wave (Surface Acoustic Wave) elements are widely used as bandpass filters in communication devices such as mobile phones. Along with the improvement in performance of mobile phones and the like, higher performance is also required for filters using surface acoustic wave elements.

  However, the surface acoustic wave element has a problem that the pass band moves due to a temperature change. In particular, lithium niobate and lithium tantalate, which are widely used at present, have a large electromechanical coupling coefficient, and are advantageous for realizing broadband filter characteristics. However, lithium niobate and lithium tantalate are inferior in temperature stability.

  For example, the temperature coefficient of frequency change of lithium tantalate is −35 ppm / ° C., and the frequency variation is large in the temperature range of −30 to + 85 ° C. For this reason, it is necessary to reduce the temperature coefficient of the frequency change.

  Patent Document 1 (Japanese Patent Laid-Open No. 2001-53579) describes a device in which a SAW propagation substrate and a support substrate are bonded by an organic thin film layer. The propagation substrate is, for example, a lithium tantalate substrate having a thickness of 30 μm, and this is bonded to a glass substrate having a thickness of 300 μm with an organic adhesive having a thickness of 15 μm.

  Patent Document 2 (Japanese Patent Laid-Open No. 2006-42008) describes a SAW device in which a lithium tantalate substrate (thickness: 125 μm) and a quartz glass substrate (thickness: 125 μm) are bonded together with an adhesive. In particular, according to (0030), it is described that an adhesive layer is necessary because peeling or cracking occurs when the support substrate and the propagation substrate are directly bonded.

  Patent Document 3 (JP-A-6-326553), Patent Document 4 (Patent No. 3774782), and Patent Document 5 (US Pat. No. 7,105,980) also describe SAW devices in which a SAW propagation substrate and a support substrate are bonded.

  Further, in Patent Document 6 (Japanese Patent Application Laid-Open No. 2005-229455), an oxide layer having a thickness of 0.1 to 40 μm is formed on both surfaces of a silicon support substrate, and then a piezoelectric substrate is bonded onto the support substrate, and a SAW device is formed. Manufacturing is described. The Si oxide film is necessary for reducing the warp of the composite piezoelectric substrate 1.

  According to (0007) (0013) of Patent Document 7 (Japanese Patent Laid-Open No. 2002-135076), the surface roughness of the substrate is 10 μm, and it is difficult to make the thickness of the adhesive layer uniform.

  According to (0018) of Patent Document 8 (Japanese Unexamined Patent Publication No. 9-167936), even if the rotation angle θ of the propagation substrate, that is, the cut angle θ changes, for example, 36 ° Y, 40 ° Y, 42 ° Y, and 44 In any case of ° Y, substantially the same temperature characteristics are exhibited.

  FIG. 6 of Patent Document 9 (Japanese Patent Laid-Open No. 2-37815) describes temperature characteristics when the thickness of the electrode is changed. According to this, there is no influence on the frequency temperature characteristic by the electrode thickness.

  FIG. 4 of Patent Document 10 (Japanese Patent Application Laid-Open No. 2005-65160) uses a quartz substrate with Euler angles (0 °, 127 °, 90 °), a normalized electrode film thickness H / λ, and a frequency temperature coefficient at a reference temperature of 25 ° C. The relationship of TCF is shown.

  The thermal expansion coefficient and Young's modulus of lithium tantalate are described in (0021) of Patent Document 11 (Japanese Patent Application Laid-Open No. 2008-310666).

  Non-Patent Document 1 (“Picture Dissolving Material Mechanics Fundamental Kiso” Hirofumi Iyama, Nikkan Kogyo Shimbun, pages 43, 44, 36, 37) describes the relationship between the thermal expansion coefficient and Young's modulus of the bonded material. Yes.

Non-Patent Document 2 (“Science of Silicon”, USC Semiconductor Fundamental Technology Research Group, issued on June 28, 1996), pages 989 and 991, describe the thermal expansion coefficient and Young's modulus of silicon.
Non-Patent Document 3 (“Glass Optical Handbook”, published by Asakura Shoten, page 282, issued February 28, 1964) contains data on borosilicate glass.

  Patent Document 12 (Japanese Patent Application No. 2009-40947) is a related application of this patent application.

"Understanding material mechanics, the fundamental kiso" Hirofumi Iyama, published by Nikkan Kogyo Shimbun, pages 43, 44, 36, 37 "Science of Silicon" USC Semiconductor Technology Research Group edited on June 28, 1996, pages 989, 991 "Glass Optics Handbook", published by Asakura Shoten, issued February 28, 1964, page 792

JP2001-53579 JP2006-42008 JP-A-6-326553 Patent No. 3777482 US Pat. No. 7,105,980 JP2005-229455 JP2002-135076 JP-A-9167936 JP-A-2-37815 JP 2005-65160 A JP2008-301066 Japanese Patent Application No. 2009-40947

  However, none of the documents solves the problem of movement of the passband accompanying a change in temperature, but rather moves away from the solution.

  Patent Document 1 (0025) and (0037) describe the temperature coefficient of the frequency of a SAW device in which a lithium tantalate substrate is bonded to a support substrate. There is almost no improvement in properties. For example, in the case of a 2 GHz SAW filter, a shift of ± 4 MHz is observed in the temperature range of −30 to + 85 ° C. This corresponds to ± 7% of the required bandwidth. Therefore, it can be seen that when the adhesive layer is provided between the lithium tantalate propagation substrate and the glass supporting substrate, the temperature characteristic of the frequency is hardly improved.

  Patent Document 2 (0037) describes that “the frequency temperature characteristic of the surface acoustic wave element can be improved”, but no improved data is described.

  Even in the description of (0062) of Patent Document 3, it is specified that bonding the surface acoustic wave propagation substrate to the support substrate is not practical.

  Judging from the above, it is common sense that a surface acoustic wave substrate having a structure in which, for example, a lithium tantalate propagation substrate is bonded to a support substrate is constantly practical, and it is impossible to reduce the temperature coefficient of frequency in particular. is there.

  In Patent Document 6, it is necessary to flow an oxygen gas at a high temperature of, for example, about 1000 ° C. and leave the Si substrate for several tens of hours to form a surface oxide film. However, this method not only oxidizes the surface of the Si substrate, but also dissolves Si itself into SiO2. For this reason, a Si defect layer is generated at the interface between Si and SiO2, and the adhesive strength of this portion is lowered. In addition, the thickness of the adhesive layer between the Si support substrate and the piezoelectric substrate is all 3 μm in the examples, and when it is thinner than 1.5 μm, the adhesive force is insufficient, and peeling occurs at 250 ° C. (0028).

  An object of the present invention is to reduce the temperature coefficient of the frequency of a surface acoustic wave device using a piezoelectric single crystal propagation substrate.

The present invention
Support substrate,
Propagation substrate made of piezoelectric single crystal,
An elastic surface comprising: an organic adhesive layer having a thickness of 0.1 μm to 1.0 μm for bonding the support substrate and the propagation substrate; and a surface acoustic wave filter or a resonator provided on the propagation substrate. This relates to a wave element.

  Contrary to the common knowledge of those skilled in the art, the present inventor has continued research on a structure in which a propagation substrate of a piezoelectric single crystal, for example, a lithium tantalate single crystal, is bonded to a support substrate. Here, an attempt was made to reduce the thickness of the organic adhesive layer, which was conventionally overlooked. Such a trial has been denied from the description of (0062) of Patent Document 3, for example.

  However, contrary to expectations, it has been found that the propagation substrate adheres well to the support substrate and the temperature coefficient of frequency is significantly reduced. That is, when the thickness of the organic adhesive is 0.1 to 1.0 μm, the temperature characteristics due to the difference in thermal expansion coefficient between the propagation substrate and the support substrate are considerably improved. On the other hand, when the thickness of the adhesive is greater than 1 μm, the stress due to the difference in thermal expansion coefficient between the propagation substrate and the support substrate is absorbed by the organic adhesive, and the effect of improving the temperature characteristics cannot be obtained. . In addition, when the thickness of the adhesive layer is less than 0.1 μm, the frequency characteristic of the frequency seems to deteriorate again due to the influence of the void, and the temperature characteristic is not improved as the adhesive layer becomes thinner. It was confirmed.

(A), (b), (c), (d) is typical sectional drawing which shows the manufacturing process of the adhesive body for surface acoustic wave elements. FIG. 2A is a cross-sectional view schematically showing the surface acoustic wave element 6, and FIG. 2B is a plan view schematically showing the surface acoustic wave element 6. (A) is a top view which shows a resonance-type surface acoustic wave element, (b) is the sectional view on the A-A 'line of (a). It is a graph which shows the relationship between the thickness of an adhesive bond layer, a thermal expansion coefficient, and the temperature characteristic of a frequency. It is a graph which shows the relationship between the thickness of an adhesive bond layer, and the temperature characteristic of a frequency. It is a graph which shows the relationship between the thickness of an adhesive bond layer, and the temperature characteristic of a frequency. It is a graph which shows the relationship between the thickness of an adhesive bond layer, and the temperature characteristic of a frequency. It is a graph which shows the relationship between the thickness of an adhesive bond layer, and the temperature characteristic of a frequency. It is a graph which shows the relationship between the thickness of an adhesive bond layer, and the temperature characteristic of a frequency. It is a graph which shows the relationship between the thickness of an adhesive bond layer, and the temperature characteristic of a frequency. It is a graph which shows the relationship between the thickness of an adhesive bond layer, and the temperature characteristic of a frequency. It is a graph which shows the relationship between the thickness of an adhesive bond layer, and the temperature characteristic of a frequency. It is a graph which shows the change of the temperature characteristic of a frequency when producing a support substrate with silicon and borosilicate glass and changing the ratio of the thickness of a support substrate and the thickness of a piezoelectric substrate.

  The surface acoustic wave device of the present invention includes a surface acoustic wave filter or a resonator. The surface acoustic wave filter is a band pass filter as described later. The resonator is a surface acoustic wave oscillation element, and includes both a 1-port type and a 2-port type.

In the present invention, the material of the support substrate is preferably a material selected from the group consisting of silicon, sapphire, aluminum nitride, alumina, borosilicate glass, and quartz glass. Preferably, the support substrate is made of silicon or borosilicate glass, particularly preferably silicon. By adopting these, it is possible to reduce the difference in thermal expansion from the propagation substrate and further improve the temperature characteristics of the frequency.

Preferably, an oxide film is not formed on the surface of the support substrate, whereby the adhesive force between the support substrate and the propagation substrate is increased, and peeling and cracking of the support substrate and the propagation substrate can be prevented even at high temperatures. From this point of view, it is preferable that the support substrate is made of silicon, and there is no silicon oxide film on the surface. In addition, the presence or absence of the surface oxide film on the support substrate is determined using a transmission electron microscope (TEM: Transmission).
The cross section is observed with an Electron Microscope.

  In the present invention, the material of the propagation substrate is preferably selected from the group consisting of lithium niobate having a large electromechanical coupling constant, lithium tantalum, and lithium niobate-lithium tantalate solid solution single crystal. Preferably, the piezoelectric single crystal is made of lithium tantalate.

  Preferably, the surface acoustic wave propagation direction in the propagation substrate is the X direction, and the cutting angle is a rotated Y-cut plate. Particularly preferably, the propagation substrate is a 36-47 ° Y-cut plate.

  The material of the organic adhesive layer that bonds the support substrate and the propagation substrate is not limited, but an acrylic resin or an epoxy resin is preferable.

  In the present invention, the thickness t of the organic adhesive layer is set to 0.1 μm or more and 1.0 μm or less. From the viewpoint of further improving the temperature characteristics of the frequency of the surface acoustic wave device, the thickness of the organic adhesive layer is preferably 0.1 μm or more, and preferably 0.8 μm or less.

FIG. 1 is a cross-sectional view schematically showing a manufacturing process of an adhesive for a surface acoustic wave device.
As shown in FIG. 1A, a support substrate 1 is prepared. As shown in FIG. 1B, an organic adhesive 2 is applied to the surface of the support substrate 1, and a substrate 3 made of a piezoelectric single crystal is bonded as shown in FIG. Next, as shown in FIG. 1D, the substrate 3 is processed and thinned to obtain a propagation substrate 3A having a thickness T2.

  Next, as shown in FIGS. 2A and 2B, the input electrode 4 and the output electrode 5 are formed on the propagation substrate 3 </ b> A to obtain the transversal surface acoustic wave element 6. A surface acoustic wave propagates from the input electrode 4 toward the output electrode 5 as indicated by an arrow 7. This portion becomes a surface acoustic wave filter.

  In a surface acoustic wave filter for a mobile phone, a resonance type surface acoustic wave element is mainly used. 3A and 3B relate to this example. FIG. 3A is a plan view showing an electrode pattern of a resonance type surface acoustic wave element, and FIG. 3B is a cross-sectional view taken along line A-A ′ of FIG.

  Electrodes 16, 17, and 18 are formed on the propagation substrate 10 to obtain a resonant surface acoustic wave device. In this example, the propagation substrate 10 is bonded onto the support substrate 12 via the organic adhesive layer 14. As described above, the support substrate 12, the adhesive layer 14, and the propagation substrate 10 are configured according to the present invention.

  Although the formation method of an organic adhesive layer is not limited, Printing and spin coating can be illustrated.

The material constituting the surface acoustic wave filter or the resonator is preferably aluminum, an aluminum alloy, copper, or gold, and more preferably aluminum or an aluminum alloy. As the aluminum alloy, it is preferable to use Al mixed with 0.3 to 5% by weight of Cu.
In this case, Ti, Mg, Ni, Mo, Ta may be used instead of Cu.

  The ratio (t / λ) of the thickness t of the surface acoustic wave filter or resonator to the surface acoustic wave wavelength λ is preferably 3 to 15%, more preferably 5% or more, and 15%. More preferably, it is as follows.

  The thickness T1 of the support substrate 1 is preferably 100 μm or more, more preferably 150 μm or more, and even more preferably 200 μm or more from the viewpoint of improving temperature characteristics. T1 is preferably 500 μm or less from the viewpoint of product size reduction.

  The thickness T2 of the propagation substrate 3A is preferably 10 to 50 μm, more preferably 10 to 40 μm, and particularly preferably 10 to 30 μm from the viewpoint of improving the frequency temperature characteristics.

Example 1
According to the manufacturing method shown in FIG. 1, a surface acoustic wave element 6 as shown in FIG. 2 was produced.
However, the substrate 3 was a 36 ° Y-cut X-propagating lithium tantalate substrate in which the SAW propagation direction was X and the cutting angle was a rotating Y-cut plate. The linear expansion coefficient in the SAW propagation direction X is 16 ppm / ° C. A single crystal silicon substrate was used as the support substrate 1. The linear expansion coefficient in the SAW propagation direction X of the support substrate 1 is 3 ppm / ° C. The thickness T1 of the support substrate 1 was 350 μm, the thickness of the piezoelectric single crystal substrate 3 was 350 μm, and the substrates were bonded to each other at 180 ° C. using an organic adhesive (acrylic). Next, the thickness of the piezoelectric single crystal substrate 3 was reduced to 30 μm by grinding. An input electrode 4 and an output electrode 5 made of metal aluminum having a thickness of 0.14 μm were formed on the obtained propagation substrate 3A. Electrode thickness t / surface acoustic wave wavelength λ = 7%.

  However, the thickness t of the organic adhesive layer 2 was variously changed from 0.05 μm to 15 μm. For each element, the thermal expansion coefficient of the surface acoustic wave element and the frequency temperature characteristic (Temperature Coefficient of Frequency) at the resonance point were measured and are shown in Table 2 and FIG.

  As can be seen from this result, it was found that the frequency temperature characteristic (Temperature Coefficient of Frequency) is significantly improved significantly by setting the thickness of the organic adhesive layer to 0.1 to 1.0 μm.

(Example 2)
Next, the surface acoustic wave element shown in FIG. 3 was produced in the same manner as in Example 1. When the same experiment as Example 1 was conducted about the obtained element, the temperature-temperature characteristic (Temperature Coefficient of Frequency) was critical by setting the thickness of the organic adhesive layer to 0.1 to 1.0 μm. It was confirmed that it was significantly improved.

(Example 3)
In the same manner as in Example 1, a surface acoustic wave device as shown in FIG. 3 was produced according to the manufacturing method shown in FIG.
However, as the propagation substrate 10, a SAW propagation direction is X, and a 36 ° Y-cut X-propagation lithium tantalate substrate whose cutting angle is a rotating Y-cut plate is used. A single crystal silicon substrate was used as the support substrate 12. The thickness T1 of the support substrate 12 was 200 μm. The thickness of the propagation substrate 10 was 30 μm. On the propagation substrate 10, electrodes 16, 17 and 18 made of metal aluminum having a thickness of 0.14 μm were formed. Electrode thickness t / surface acoustic wave wavelength λ = 7%.

  However, the thickness t of the organic adhesive layer 2 was variously changed from 0.05 μm to 15 μm. For each element, the temperature temperature characteristic (Temperature Coefficient of Frequency) at the resonance point of the surface acoustic wave element was measured and shown in Table 3 in FIG.

Example 4
In the same manner as in Example 1, a surface acoustic wave device as shown in FIG. 3 was produced according to the manufacturing method shown in FIG.
However, the propagation substrate 10 was a 47 ° Y-cut X-propagation lithium tantalate substrate in which the SAW propagation direction was X and the cutting angle was a rotating Y-cut plate. A single crystal silicon substrate was used as the support substrate 12. The thickness T1 of the support substrate 12 was 350 μm, and the thickness of the propagation substrate 10 was 30 μm. On the obtained propagation substrate 10, electrodes 16, 17, and 18 made of metal aluminum having a thickness of 0.14 μm were formed. Electrode thickness t / surface acoustic wave wavelength λ = 7%.

  However, the thickness t of the organic adhesive layer 2 was variously changed from 0.05 μm to 15 μm. For each element, the frequency temperature characteristic (Temperature Coefficient of Frequency) at the resonance point of the surface acoustic wave element was measured and shown in FIG.

(Example 5)
In the same manner as in Example 1, a surface acoustic wave device as shown in FIG. 3 was produced according to the manufacturing method shown in FIG.
However, the propagation substrate 10 was a 47 ° Y-cut X-propagation lithium tantalate substrate in which the SAW propagation direction was X and the cutting angle was a rotating Y-cut plate. A single crystal silicon substrate was used as the support substrate 12. The thickness T1 of the support substrate 12 was 350 μm, and the thickness of the propagation substrate was 30 μm. On the obtained propagation substrate 10, electrodes 16, 17, and 18 made of aluminum alloy (Al-1% Cu) having a thickness of 0.14 μm were formed. Electrode thickness t / surface acoustic wave wavelength λ = 7%.

  However, the thickness t of the organic adhesive layer 2 was variously changed from 0.05 μm to 15 μm. For each element, the frequency temperature characteristic (Temperature Coefficient of Frequency) at the resonance point of the surface acoustic wave element was measured and is shown in FIG.

(Example 6)
In the same manner as in Example 1, a surface acoustic wave device as shown in FIG. 3 was produced according to the manufacturing method shown in FIG.
However, the propagation substrate 10 was a 47 ° Y-cut X-propagation lithium tantalate substrate in which the SAW propagation direction was X and the cutting angle was a rotating Y-cut plate. A single crystal silicon substrate was used as the support substrate 12. The thickness T1 of the support substrate 12 was 350 μm, and the thickness of the propagation substrate was 30 μm. On the obtained propagation substrate 10, metal aluminum electrodes 16, 17, and 18 having a thickness of 0.06 μm were formed. Electrode thickness t / surface acoustic wave wavelength λ = 3%.

  However, the thickness t of the organic adhesive layer 2 was variously changed from 0.05 μm to 15 μm. For each element, the frequency temperature characteristic (Temperature Coefficient of Frequency) at the resonance point of the surface acoustic wave element was measured and shown in FIG.

(Example 7)
In the same manner as in Example 1, a surface acoustic wave device as shown in FIG. 3 was produced according to the manufacturing method shown in FIG.
However, the propagation substrate 10 was a 47 ° Y-cut X-propagation lithium tantalate substrate in which the SAW propagation direction was X and the cutting angle was a rotating Y-cut plate. A single crystal silicon substrate was used as the support substrate 12. The thickness T1 of the support substrate 12 was 350 μm, and the thickness of the propagation substrate was 30 μm. On the obtained propagation substrate 10, metal aluminum electrodes 16, 17 and 18 having a thickness of 0.3 μm were formed. Electrode thickness t / surface acoustic wave wavelength λ = 15%.

  However, the thickness t of the organic adhesive layer 2 was variously changed from 0.05 μm to 15 μm. For each element, the frequency temperature characteristic (Temperature Coefficient of Frequency) at the resonance point of the surface acoustic wave element was measured and shown in FIG.

(Example 8)
In the same manner as in Example 1, a surface acoustic wave device as shown in FIG. 3 was produced according to the manufacturing method shown in FIG.
However, as the propagation substrate 10, a SAW propagation direction is X, and a 36 ° Y-cut X-propagation lithium tantalate substrate whose cutting angle is a rotating Y-cut plate is used. A single crystal silicon substrate was used as the support substrate 12. The thickness T1 of the support substrate 12 was 500 μm, and the thickness of the propagation substrate was 10 μm. On the obtained propagation substrate 10, electrodes 16, 17, and 18 made of metal aluminum having a thickness of 0.14 μm were formed. Electrode thickness t / surface acoustic wave wavelength λ = 7%.

  However, the thickness t of the organic adhesive layer 2 was variously changed from 0.05 μm to 15 μm. For each element, the frequency temperature characteristic (Temperature Coefficient of Frequency) at the resonance point of the surface acoustic wave element was measured and shown in FIG.

Example 9
In the same manner as in Example 1, a surface acoustic wave device as shown in FIG. 3 was produced according to the manufacturing method shown in FIG.
However, as the propagation substrate 10, a SAW propagation direction is X, and a 36 ° Y-cut X-propagation lithium tantalate substrate whose cutting angle is a rotating Y-cut plate is used. A single crystal silicon substrate was used as the support substrate 1. The thickness T1 of the support substrate 12 was 150 μm, and the thickness of the propagation substrate was 25 μm. On the obtained propagation substrate 10, electrodes 16, 17, and 18 made of metal aluminum having a thickness of 0.14 μm were formed. Electrode thickness t / surface acoustic wave wavelength λ = 7%.

  However, the thickness t of the organic adhesive layer 2 was variously changed from 0.05 μm to 15 μm. And about each element, the frequency temperature characteristic (Temperature Coefficient of Frequency) in the resonance point of a surface acoustic wave element was measured, and it shows in FIG.

(Example 10)
In the same manner as in Example 1, a surface acoustic wave device as shown in FIG. 3 was produced according to the manufacturing method shown in FIG.
However, as the propagation substrate 10, a SAW propagation direction is X, and a 36 ° Y-cut X-propagation lithium tantalate substrate whose cutting angle is a rotating Y-cut plate is used. A single crystal silicon substrate was used as the support substrate 12. The thickness T1 of the support substrate 12 was 300 μm, and the thickness of the propagation substrate was 40 μm. On the obtained propagation substrate 10, electrodes 16, 17, and 18 made of metal aluminum having a thickness of 0.14 μm were formed. Electrode thickness t / surface acoustic wave wavelength λ = 7%.

  However, the thickness t of the organic adhesive layer 2 was variously changed from 0.05 μm to 15 μm. For each element, the frequency temperature characteristic (Temperature Coefficient of Frequency) at the resonance point of the surface acoustic wave element was measured and shown in FIG.

(Example 11)
In the same manner as in Example 1, a surface acoustic wave device as shown in FIG. 3 was produced according to the manufacturing method shown in FIG.
However, as the propagation substrate 10, a SAW propagation direction is X, and a 36 ° Y-cut X-propagation lithium tantalate substrate whose cutting angle is a rotating Y-cut plate is used. As the support substrate 12, a single crystal silicon substrate or a borosilicate glass substrate was used. The thickness of the propagation substrate was 30 μm, and the thickness of the adhesive layer was 0.3 μm. On the obtained propagation substrate 10, electrodes 16, 17, and 18 made of metal aluminum having a thickness of 0.14 μm were formed. Electrode thickness t / surface acoustic wave wavelength λ = 7%.

  However, the thickness T1 of the support substrate 1 was varied from 100 to 500 μm. And about each element, the frequency temperature characteristic (Temperature Coefficient of Frequency) in the resonance point of a surface acoustic wave element was measured, and it shows in FIG.

  As can be seen from this result, the temperature characteristic of the frequency is almost proportional to the ratio of the support substrate to the piezoelectric substrate over the thickness of the support substrate of 100 to 500 μm, regardless of whether the silicon substrate or the borosilicate glass is used. , It was very low value.

(Example 12)
A surface acoustic wave element 6 as shown in FIG.
However, the organic adhesive layer was an epoxy adhesive. Otherwise, the test was performed under the same conditions as in Example 1. The thickness t of the organic adhesive layer 2 was variously changed from 0.05 μm to 15 μm, and the thermal expansion coefficient of the surface acoustic wave element and the frequency temperature characteristic at the resonance point (Temperature Coefficient of Frequency) were measured for each element. The same result as in the example was obtained.

(Example 13)
The relationship between the adhesive strength (compression shear) between the 36 ° Y-cut X-propagating lithium tantalate substrate and the silicon substrate was examined by changing the thickness of the organic adhesive layer. The shape of the lithium tantalate substrate and the silicon substrate is 5 × 5 × 1 mm.
Organic adhesive layer thickness: 0.02μm ―――――― Adhesive strength (kgf / cm2): 25
Organic adhesive layer thickness: 0.05μm ----- Adhesive strength (kgf / cm2): 40
Organic adhesive layer thickness: 0.1 μm ------------------------- Adhesive strength (kgf / cm2)
Organic adhesive layer thickness: 0.2μm ----- Adhesive strength (kgf / cm2): 200

  From this result, it can be seen that it is preferable that the thickness of the organic adhesive layer is 0, 1 μm or more because a target adhesive strength of 60 kgf / cm 2 or more can be achieved. The surface roughness of the bonding surface between the lithium tantalate substrate and the silicon substrate is preferably 0.1 μm or less.

Claims (12)

Support substrate,
Propagation substrate made of piezoelectric single crystal,
An organic adhesive layer having a thickness of 0.1 μm to 1.0 μm for bonding the support substrate and the propagation substrate, and a surface acoustic wave filter or a resonator provided on the propagation substrate. , Surface acoustic wave element.   2. The element according to claim 1, wherein the piezoelectric single crystal is selected from the group consisting of lithium niobate, lithium tantalate, and lithium niobate-lithium tantalate solid solution single crystal.   The element according to claim 2, wherein the piezoelectric single crystal is made of lithium tantalate.   4. The element according to claim 2, wherein the surface acoustic wave propagation direction in the propagation substrate is an X direction, and the propagation substrate is a 36-47 [deg.] Y cut plate.   5. The element according to claim 4, wherein the surface acoustic wave filter or resonator is made of aluminum or an aluminum alloy.   The ratio (t / λ) of the thickness t of the surface acoustic wave filter or the resonator to the surface acoustic wave wavelength λ is 3 to 15%. The element according to item.   The device according to claim 1, wherein the propagation substrate has a thickness of 10 to 40 μm.   The element according to claim 1, wherein the support substrate has a thickness of 150 to 500 μm.   The said support substrate consists of material chosen from the group which consists of a silicon | silicone, a sapphire, an aluminum nitride, an alumina, a borosilicate glass, and quartz glass, The claim any one of Claims 1-8 characterized by the above-mentioned. Elements.   The device according to claim 9, wherein the support substrate is made of silicon or borosilicate glass.   The device according to claim 10, wherein the support substrate is made of silicon. The element according to claim 1, wherein an oxide film is not formed on a surface of the support substrate.

Images