JP2011124628A - Composite piezoelectric chip and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite piezoelectric chip superior in reliability of stably maintaining electrical characteristics as a surface acoustic wave element without causing breaking/chipping or peeling at the piezoelectric material part of the composite piezoelectric chip even after heat treatment or a moisture resistance test, and a method of manufacturing the composite piezoelectric chip. <P>SOLUTION: For the composite piezoelectric chip 4, a composite piezoelectric substrate 3 which is obtained by sticking a piezoelectric substrate 1 on a support substrate 2 is subdivided. For the composite piezoelectric chip 4, the composite piezoelectric substrate 3 is subdivided after making a cut deeper than the thickness of the piezoelectric material part of the composite piezoelectric substrate 3, and surface roughness (Ra) of the piezoelectric material part side of the composite piezoelectric chip 4 is ≤0.15 μm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a composite piezoelectric chip (hereinafter referred to as a composite piezoelectric chip), and more particularly to a composite piezoelectric chip used for a surface acoustic wave device and a manufacturing method thereof.

  A surface acoustic wave (SAW) device in which a comb electrode for exciting a surface acoustic wave is formed on a piezoelectric substrate is used as a component for frequency adjustment / selection in high frequency communication such as a cellular phone.

The piezoelectric substrate material used for this has a high conversion efficiency from electrical signals to mechanical vibration (hereinafter referred to as electromechanical coupling coefficient), and the center of a filter or the like determined by the electrode spacing of the comb-shaped electrodes and the acoustic velocity of elastic waves. It is required that the frequency does not vary with temperature (hereinafter referred to as frequency-temperature characteristics).
In other words, it is preferable to have a piezoelectric substrate having both a large electromechanical coupling coefficient and a small frequency temperature coefficient. An example of a piezoelectric substrate that realizes such characteristics is a composite piezoelectric substrate in which a piezoelectric substrate and another substrate are bonded.

Here, in the composite piezoelectric chip obtained by subdividing the composite piezoelectric substrate, it is necessary to reduce the thickness of the piezoelectric body to 100 μm or less, preferably about 30 μm, in order to ensure the effect of improving the frequency temperature characteristics of the surface acoustic wave element. is there.
This composite piezoelectric chip is obtained by subdividing the composite piezoelectric substrate by a method such as cutting, but the chipping on the outer peripheral portion (side surface of the piezoelectric portion) of the composite piezoelectric chip should be minimized.
This is because the composite piezoelectric chip is deformed by the bimetal effect due to temperature change. However, if there is a crack on the outer periphery of the piezoelectric body of the composite piezoelectric chip, the heat cycle of the operating temperature of -40 ° C to 85 ° C is repeated, or the surface acoustic wave device This is because heating at about 260 ° C. is repeated at the time of mounting, so that stress concentrates around the chip of the composite piezoelectric chip and cracks occur in the piezoelectric portion.

  In order to solve such problems, Patent Documents 1 to 3 below disclose the inventions described below.

An example of a surface acoustic wave element using a composite piezoelectric substrate is disclosed in Patent Document 1.
In Patent Document 1, (a) a first substrate made of a piezoelectric material having a pair of comb-shaped electrodes formed on one main surface is laminated on a second substrate made of a material different from the first substrate. Forming a laminated substrate; (b) forming a groove in a portion of the laminated substrate around the comb-shaped electrode; and (c) forming a substantially central portion of the groove in the laminated substrate from the groove. And a method of manufacturing a surface acoustic wave device including a step of cutting with a narrow width.

  Patent Document 2 discloses a surface acoustic wave element including a laminated substrate in which a first substrate made of a piezoelectric material is laminated on a second substrate made of a material different from the first substrate, A stepped portion or a cutout portion is formed on a peripheral edge of the laminated substrate on the first substrate side, the stepped portion being formed on one main surface of the first substrate; A surface acoustic wave element is disclosed in which the portion or the notch is formed from the first substrate to the second substrate.

  Patent Document 1 and Patent Document 2 solve the problem that it is difficult to handle a surface acoustic wave element having a laminated structure in which a piezoelectric single crystal having a thickness of several tens of microns and a glass substrate are laminated. For example, when the surface acoustic wave element is mounted on a package, particularly when the surface acoustic wave element is picked up, cracks and cracks may occur in the piezoelectric single crystal layer (piezoelectric body portion). When the surface acoustic wave element is divided, if the cutting blade corresponding to the glass substrate is used for cutting, the piezoelectric single crystal portion is cracked or chipped at the time of cutting due to the difference in material characteristics.

  In Patent Document 1 and Patent Document 2, the piezoelectric crystal is ground (cut) by, for example, a thickness of 0.2 mm and an abrasive grain size of 8.5 ± 0.7 μm (at a cumulative height of 50%). Particle diameter: JIS R6001, ISO 8486-1, ISO 8486-2) cutting blades can be used.

  In addition, when the glass substrate is cut with the same cutting blade as the piezoelectric single crystal, the cutting blade is heavily worn, and the blade may be damaged due to clogging. In the process of cutting the glass substrate, Cutting with a cutting blade having a coarse abrasive grain diameter, for example, an abrasive grain diameter of about 24.0 ± 1.5 μm (particle diameter at 50% cumulative height) prolongs the life of the cutting blade. There is a description that it is preferable to be able to.

Next, in Patent Document 3, a single crystal piezoelectric substrate of lithium niobate or lithium tantalate (LT), a support substrate bonded to the piezoelectric substrate and made of a material having an expansion coefficient different from that of the piezoelectric substrate, A surface acoustic wave device comprising: a comb-shaped electrode configured to excite a surface acoustic wave disposed on a surface; and the width of the piezoelectric substrate being narrower than the width of the support substrate. Has been.
That is, in Patent Document 3, an input electrode made of an IDT electrode and an output are arranged on the upper surface of a lithium tantalate (LT) substrate, and the width of this LT substrate is narrower than the width of the corresponding support substrate. It has a structure. This is because, first, only the LT is divided with a rotary blade made of a material suitable for dividing LT, and then a rotary blade having a narrower width than the rotary blade for dividing LT with a material suitable for dividing the support substrate is used. It is described that it can be realized.

Further, when the substrate having LT and SiN ceramics bonded thereto is divided by the above method with the width difference of the rotary blades set to 50 μm, the LT chip can be divided into 10 μm or less and the ceramic chip can be divided into 10 μm or less. In addition, by suppressing chipping of the piezoelectric substrate, the piezoelectric substrate that contributes to the transmission and reception of surface acoustic waves can be divided without damaging it, and its frequency characteristics and temperature characteristics can be stabilized, as well as preventing deterioration in reliability due to chipping. It is disclosed that it is possible.
Moreover, although the said patent document 3 has mentioned as an example dividing | segmenting a piezoelectric substrate and a support substrate with the different rotary blades suitable for each material, it divides | segments a piezoelectric substrate with a laser or other methods, and then There is a description that the method of dividing the support substrate with a rotary blade and vice versa is equally effective in the method of dividing the piezoelectric substrate with the rotary blade and then dividing the support substrate with a laser or other method.

  However, in the composite piezoelectric chip, the composite piezoelectric chip can be obtained simply by forming a stepped portion or a notch in the periphery of the piezoelectric body of the composite piezoelectric chip, or by forming the piezoelectric substrate so that the width of the piezoelectric substrate is smaller than the width of the support substrate. Chip reliability was insufficient.

  Therefore, there is a demand for a composite piezoelectric chip that has excellent reliability in which electric characteristics as a surface acoustic wave element can be stably maintained without cracking or chipping or peeling in the piezoelectric body portion even after heat treatment or moisture resistance test.

JP 2001-60846 A JP 2009-118504 A JP 2009-94661 A

  The present invention has been made in view of the above-described problems, and does not cause cracks, burrs, or peeling in the piezoelectric body portion of the composite piezoelectric chip even after heat treatment or moisture resistance test, and has stable electrical characteristics as a surface acoustic wave element. An object of the present invention is to provide a composite piezoelectric chip excellent in reliability that can be maintained in the above and a manufacturing method thereof.

  In order to solve the above-described problems, the present invention provides a composite piezoelectric chip obtained by subdividing a composite piezoelectric substrate in which a piezoelectric substrate and a support substrate are bonded together, and the composite piezoelectric chip includes the composite piezoelectric substrate. The piezoelectric body portion is subdivided after being cut deeper than the thickness of the piezoelectric portion, and the surface roughness (Ra) of the piezoelectric portion side surface of the composite piezoelectric chip is 0.15 μm or less. A composite piezoelectric chip is provided.

  As described above, the composite piezoelectric chip is obtained by subdividing the composite piezoelectric substrate after cutting deeper than the thickness of the piezoelectric body portion of the composite piezoelectric substrate, so that all the thickness directions of the piezoelectric body portion of the composite piezoelectric substrate can be obtained. The surface roughness (Ra) of the piezoelectric body side surface of the composite piezoelectric chip is 0.15 μm or less and the smoothness of the side surface of the piezoelectric body portion is smooth at a level close to a mirror surface. As a result, there is no cracking, chipping or peeling in the piezoelectric body part even after heat treatment or moisture resistance test, and the electrical characteristics as a surface acoustic wave element are kept stable, resulting in a highly reliable composite piezoelectric chip. .

  Moreover, it is preferable that the surface roughness (Ra) of the piezoelectric body side surface of the composite piezoelectric chip is 0.10 μm or less.

  With such a composite piezoelectric chip having a surface roughness (Ra) on the side surface of the piezoelectric body portion of 0.10 μm or less, cracking, chipping or peeling occurs in the piezoelectric body portion even more reliably after heat treatment or moisture resistance test. not, the composite piezoelectric chip electrical characteristics as the surface acoustic wave device excellent in reliability to be kept stable.

  The composite piezoelectric substrate is cut using a blade having a particle size of 4.5 μm or less at a cumulative height of 50% defined by JIS R6001. Is preferred.

  In this way, the cutting of the composite piezoelectric substrate is made by using a blade having a particle size of 4.5 μm or less at a cumulative height of 50% defined by JIS R6001. Thus, a composite piezoelectric chip in which the surface roughness (Ra) of the piezoelectric body side surface of the composite piezoelectric chip is 0.15 μm or less can be obtained.

  The composite piezoelectric substrate preferably has a surface on which an electrode for detecting surface acoustic wave excitation is formed.

  As described above, the composite piezoelectric chip obtained from the composite piezoelectric substrate in which the surface acoustic wave excitation detection electrode is formed on the surface of the composite piezoelectric substrate can stably maintain the electrical characteristics as the surface acoustic wave element. The resulting composite piezoelectric chip has excellent reliability.

  Moreover, it is preferable that the composite piezoelectric chip is obtained by cutting the composite piezoelectric substrate into 5 μm to 20 μm deeper than the thickness of the piezoelectric portion of the composite piezoelectric substrate and then subdividing it.

  As described above, if the composite piezoelectric chip is obtained by cutting the composite piezoelectric substrate into 5 μm to 20 μm deeper than the thickness of the piezoelectric portion of the composite piezoelectric substrate, the piezoelectric body of the composite piezoelectric substrate can be used. The entire thickness direction of the portion is cut (subdivided) neatly, and the consumption of the blade (dicing blade) can be suppressed by limiting the amount of cutting into the lower portion of the composite piezoelectric substrate.

  The piezoelectric substrate preferably has a thickness of 100 μm or less.

  As described above, when the thickness of the piezoelectric substrate is 100 μm or less, the warp due to heating is small and there is no crack, and the improvement effect of the frequency temperature characteristics of the surface acoustic wave element can be ensured reliably. .

The piezoelectric substrate is preferably made of either LiTaO ₃ or LiNbO ₃ .

Thus, if the piezoelectric substrate is made of either LiTaO ₃ or LiNbO ₃ , the electromechanical coupling coefficient is large, and the temperature fluctuation of the operating frequency is suppressed by the effect of the combined piezoelectric substrate. An inexpensive composite piezoelectric substrate can be provided.

  Further, the support substrate may be thermal expansion coefficient is assumed to be smaller than the thermal expansion coefficient of the piezoelectric substrate.

  Thus, by making the support substrate have a coefficient of thermal expansion smaller than that of the piezoelectric substrate, stress is generated in the piezoelectric substrate in accordance with the temperature change, and the frequency temperature characteristics are more reliably improved. Can do.

  Moreover, it is preferable that the said support substrate is ceramics.

  Thus, when the support substrate is ceramic, the thermal expansion coefficient can be made smaller than that of the piezoelectric substrate, and since ceramic is a material widely used as a packaging material, it is cheaper and has a frequency temperature characteristic. An improved high-performance composite piezoelectric chip can be obtained.

  The support substrate is preferably composed mainly of alumina.

  As described above, when a support substrate containing alumina as a main component is used, the amount of warpage after heat treatment can be further reduced, and an inexpensive composite piezoelectric substrate can be obtained.

  The support substrate is preferably an insulator.

  As described above, when the support substrate is an insulator, a composite piezoelectric chip is obtained in which the electrical characteristics of the surface acoustic wave element are more stably maintained.

  Further, the composite piezoelectric substrate may be a composite obtained by bonding the piezoelectric substrate and the support substrate through an adhesive.

  Thus, as long as it was bonded via an adhesive, a relatively inexpensive composite piezoelectric chip.

  Further, the composite piezoelectric substrate may be a composite in which the piezoelectric substrate and the support substrate are directly bonded at room temperature without using an inorganic thin film layer or an amorphous layer.

  Thus, even if the piezoelectric substrate and the support substrate are joined without using an inorganic thin film layer or an amorphous layer, the occurrence of warping can be reduced if the composite piezoelectric substrate is joined directly at room temperature. it can.

  Further, the support substrate is preferably resistivity of the silicon substrate over the P-type 1,000Ω · cm.

  Thus, a P-type silicon substrate is preferable because a high-resistance silicon substrate can be obtained at a relatively low cost by combining the CZ method and the FZ method. In addition, if the support substrate is a silicon substrate having a high resistance as described above, it is preferable because it improves the electrical insulation of the support substrate.

  The present invention also relates to a method of manufacturing a composite piezoelectric chip that subdivides a composite piezoelectric substrate in which a piezoelectric substrate and a support substrate are bonded together, and at least the composite piezoelectric substrate has a fine particle size defined by JIS R6001. Using a blade having a particle diameter of 4.5 μm or less at a cumulative height of 50%, a cut is made deeper than the thickness of the piezoelectric portion of the composite piezoelectric substrate, and then the composite piezoelectric substrate into which the cut has been made is subdivided. By providing the composite piezoelectric chip, a composite piezoelectric chip having a surface roughness (Ra) of 0.15 μm or less on the side surface of the piezoelectric body portion of the composite piezoelectric chip is provided.

  In this way, at least the composite piezoelectric substrate is formed by using the blade having a particle diameter of 4.5 μm or less at a cumulative height of 50% defined by JIS R6001 as the particle size of the polishing fine powder. The surface roughness (Ra) of the piezoelectric body portion side surface of the composite piezoelectric chip is 0.15 μm or less by making a cut deeper than the thickness of the body portion and then subdividing the composite piezoelectric substrate into which the cut has been made. Using the composite piezoelectric chip manufacturing method to obtain a composite piezoelectric chip is reliable because the piezoelectric part does not crack or peel even after heat treatment or moisture resistance test, and the electrical characteristics as a surface acoustic wave element are kept stable. A composite piezoelectric chip having excellent properties can be obtained.

  Further, the composite piezoelectric substrate is subdivided by using a blade having a coarser particle size of the abrasive powder than a blade used for making a cut deeper than the thickness of the piezoelectric body portion of the composite piezoelectric substrate. Is preferred.

  In this way, the composite piezoelectric substrate is subdivided by using a blade having a coarser finer particle size than the blade used for making a cut deeper than the thickness of the piezoelectric body portion of the composite piezoelectric substrate. makes it possible to life of the blade, in good productivity low cost can be obtained a composite piezoelectric chip.

  Moreover, it is preferable to obtain a composite piezoelectric chip having a surface roughness (Ra) of the piezoelectric body portion side surface of the composite piezoelectric chip of 0.10 μm or less.

  As described above, when a composite piezoelectric chip having a surface roughness (Ra) of the piezoelectric body portion side of the composite piezoelectric chip of 0.10 μm or less is obtained, it is more sure that the piezoelectric body section is cracked even after heat treatment and moisture resistance test. It is possible to obtain a composite piezoelectric chip excellent in reliability in which electrical characteristics as a surface acoustic wave element are stably maintained without causing any chipping or peeling.

  Further, the surface of the composite piezoelectric substrate, it is preferable to form the electrode of the surface acoustic wave excitation detection.

  In this way, by forming electrodes for detecting surface acoustic wave excitation on the surface of a composite piezoelectric substrate and subdividing the composite piezoelectric substrate, the electrical characteristics as a surface acoustic wave element can be maintained stably. A composite piezoelectric chip having excellent properties can be obtained.

  Moreover, it is preferable that the notch of the piezoelectric body part is cut by 5 μm to 20 μm deeper than the thickness of the piezoelectric part of the composite piezoelectric substrate, and then the composite piezoelectric substrate into which the cut is made is subdivided.

  In this way, a composite piezoelectric substrate is obtained by cutting the composite piezoelectric substrate 5 μm to 20 μm deeper than the thickness of the piezoelectric body portion of the composite piezoelectric substrate, and then subdividing the cut composite piezoelectric substrate to obtain a composite piezoelectric chip. The piezoelectric body part of the piezoelectric substrate can be cut (subdivided) cleanly in the thickness direction, and the consumption of the blade can be suppressed by limiting the cutting amount to the lower part of the composite piezoelectric substrate.

  As described above, according to the present invention, cracking and peeling are not generated in the piezoelectric body portion of the composite piezoelectric chip even after the heat treatment and the moisture resistance test, and the electrical characteristics as the surface acoustic wave element are stably maintained. A composite piezoelectric chip having excellent reliability can be obtained.

Is a process flow diagram showing an example of a composite piezoelectric chip and its manufacturing method of the present invention. It is a measurement result of the resonance characteristic (S11) before and behind the heat processing of the composite piezoelectric chip in Examples 1-6.

Hereinafter, the present invention will be described more specifically.
As mentioned above, there is no cracking or chipping in the piezoelectric part even after heat treatment or moisture resistance test, and the electrical characteristics as a surface acoustic wave element are kept stable. A piezoelectric chip and a manufacturing method thereof have been desired.

Conventionally, in a composite piezoelectric chip, a heat cycle of an operating temperature of −40 ° C. to 85 ° C. is repeated, or heating at about 260 ° C. is repeated when a surface acoustic wave element is mounted. Numerous inventions have been made for the problem of cracks in the body, as in Patent Documents 1 to 3 above.
However, as in the above invention, in the composite piezoelectric chip, a stepped part or a notch is formed around the piezoelectric body of the composite piezoelectric chip, or the width of the piezoelectric substrate is narrower than the width of the support substrate. However, the reliability of the composite piezoelectric chip was insufficient.

  Accordingly, the inventors of the present invention provide a composite piezoelectric chip obtained by subdividing a composite piezoelectric substrate in which a piezoelectric substrate and a support substrate are bonded to each other, and the composite piezoelectric chip includes the piezoelectric portion of the composite piezoelectric substrate. When the composite piezoelectric chip has a surface roughness (Ra) of 0.15 μm or less on the side surface of the piezoelectric body portion of the composite piezoelectric chip, the composite piezoelectric chip is subdivided after cutting deeper than the thickness of the composite piezoelectric chip. A surface acoustic wave device made of a piezoelectric chip does not cause cracking, chipping or peeling on the piezoelectric body even after heat treatment or moisture resistance test, and the electrical characteristics as a surface acoustic wave device are stable and excellent in reliability. I found out.

Hereinafter, the composite piezoelectric chip according to the present invention will be described in detail with reference to FIG. 1, but the present invention is not limited thereto.
A composite piezoelectric chip 4 according to the present invention is obtained by subdividing a composite piezoelectric substrate 3 obtained by bonding a piezoelectric substrate 1 and a support substrate 2 into a chip shape. The composite piezoelectric chip 4 of the present invention is obtained by subdividing the composite piezoelectric substrate 3 after making a cut 6 deeper than the thickness of the piezoelectric body portion 5 of the composite piezoelectric substrate 3. The composite piezoelectric chip 4 has a surface roughness (Ra) of the side surface 5 ′ of the body part of 0.15 μm or less.

  With such a composite piezoelectric chip 4, all the thickness direction of the piezoelectric body portion is cleanly cut (subdivided), and the smoothness of the side surface 5 'of the piezoelectric body portion of the composite piezoelectric chip 4 is close to a mirror surface. The smoothness at the level prevents cracks, burrs, and peeling in the piezoelectric part even after heat treatment and moisture resistance testing, and it is a highly reliable composite that maintains stable electrical characteristics as a surface acoustic wave device. The piezoelectric chip 4 is obtained.

  The surface roughness (Ra) of the side surface 5 ′ of the piezoelectric body portion of the composite piezoelectric chip 4 is more preferably a composite piezoelectric chip 4 having a surface roughness of 0.10 μm or less. Can be suppressed.

  Further, the surface roughness of the side surface 5 ′ of the piezoelectric portion of the composite piezoelectric chip 4 in the present invention is evaluated with a laser microscope (VK8700 manufactured by KEYENCE), and the definition of the surface roughness (Ra) by the laser microscope is JIS B. 0601-2001 (ISO 4287-1997 compliant) is calculated by accumulating data at a magnification of 1000 times and a height direction of 0.01 μm steps.

  Further, the notch 6 of the composite piezoelectric substrate can be formed using a blade having a particle size of 4.5 μm or less at a cumulative height of 50% defined by JIS R6001. The notch 6 is cut deeper by 5 μm to 20 μm than the thickness of the piezoelectric body portion 5 of the composite piezoelectric substrate 3 and then subdivided, so that the composite piezoelectric chip 4 can cleanly cut all the thickness directions of the piezoelectric body portion. Further, the wear of the blade can be suppressed by limiting the amount of cutting into the lower part of the composite piezoelectric substrate.

As the piezoelectric substrate 1 used for obtaining the composite piezoelectric chip 4 of the present invention, one made of LiTaO ₃ or LiNbO ₃ can be used. If the piezoelectric substrate 1 is either LiTaO ₃ or LiNbO ₃ , an inexpensive composite piezoelectric substrate having a large electromechanical coupling coefficient and suppressing temperature fluctuations in the operating frequency due to the effect of the composite piezoelectric substrate can be obtained. Can be provided.
Further, by setting the thickness of the piezoelectric substrate 1 to 100 μm or less, it is possible to reduce warping due to heating and to prevent cracking, and to ensure the frequency temperature characteristics of the surface acoustic wave element more reliably. In order to set the thickness of the piezoelectric substrate 1 within this range, for example, after the composite piezoelectric substrate 3 is formed, the piezoelectric substrate may be ground, lapped, polished (polished), or the like.

Further, as the support substrate 2 used for obtaining the composite piezoelectric chip 4 of the present invention, one having a thermal expansion coefficient smaller than that of the piezoelectric substrate 1 can be used. By making the support substrate 2 have a thermal expansion coefficient smaller than that of the piezoelectric substrate 1, stress is generated in the piezoelectric substrate in accordance with the temperature change, and the frequency temperature characteristics can be improved.
Moreover, the support substrate 2 can be made of ceramics. When the support substrate 2 is a ceramic, the thermal expansion coefficient can be made smaller than that of the piezoelectric substrate 1, and since the ceramic is a material widely used as a package material, the frequency temperature characteristics are improved at a lower cost. And a high-performance composite piezoelectric chip.

  Further, as the supporting substrate 2, those alumina of the main component, it is possible to use an insulating material. As described above, when a support substrate containing alumina as a main component is used, the amount of warpage after heat treatment can be further reduced, and an inexpensive composite piezoelectric substrate can be obtained. In addition, since the support substrate 2 is an insulator, a composite piezoelectric chip in which electrical characteristics as a surface acoustic wave element can be maintained more stably.

  The composite piezoelectric substrate 3 may be a composite of the piezoelectric substrate 1 bonded to the support substrate 2 via an adhesive. As long as it was bonded via the adhesive in this manner can be relatively inexpensive composite piezoelectric chip. Such a composite piezoelectric substrate via an adhesive can be produced, for example, by applying an adhesive to one or both of the piezoelectric substrate 1 and the support substrate 2 and bonding them firmly under vacuum to bond firmly. At this time, it is preferable to clean the surface of each substrate before bonding so that no foreign matter is mixed into the adhesive surface, and the surface is subjected to a hydrophilic treatment with an ammonia-hydrogen peroxide aqueous solution or a plasma treatment. Alternatively, the substrate may be heated to 100 ° C. and pretreated with short-wave UV light having a wavelength of 200 nm or less and high-concentration ozone to increase the adhesive force.

  And as an adhesive agent, if it is a photocuring adhesive agent which has an epoxy methacrylate as a main component, it can be easily made into a uniform adhesive layer by spin coating or other application methods. If such adhesive layer is uniform, it becomes composite piezoelectric chip 4 high quality, which is uniformly adhered. And since it is photocurable, the piezoelectric substrate 1 and the support substrate 2 can be firmly bonded and bonded by light irradiation at room temperature, and it is not necessary to raise the temperature. It is preferable for maintaining a flat shape at room temperature without deformation.

  Further, the composite piezoelectric substrate 3 can be a composite in which the piezoelectric substrate 1 and the support substrate 2 are directly bonded at room temperature without using an inorganic thin film layer or an amorphous layer. In this way, the composite piezoelectric substrate that is directly bonded at room temperature to be combined reduces the occurrence of warping even if the piezoelectric substrate and the supporting substrate are bonded without using an inorganic thin film layer or an amorphous layer. can do. At this time, it is particularly preferable to clean the surfaces of the substrates before bonding so that no foreign matter is mixed into the adhesive surface, and the surfaces are hydrophilized with an aqueous ammonia-hydrogen peroxide solution or plasma. Adhesion can be increased by treating or heating the substrate to 100 ° C. and pre-treating with short-wave UV light having a wavelength of 200 nm or less and high-concentration ozone.

  The support substrate 2 can be a P-type silicon substrate having a resistivity of 1,000 Ω · cm or more. Thus, a P-type silicon substrate is preferable because a high-resistance silicon substrate can be obtained at a relatively low cost by combining the CZ method and the FZ method. In addition, if the support substrate is a high-resistance silicon substrate, the electrical insulation of the support substrate can be improved, and the electrical property as a surface acoustic wave element can be achieved without using an inorganic thin film layer or an amorphous layer. The mechanical characteristics can be kept more stable.

A method for manufacturing a composite piezoelectric chip according to the present invention will be described with reference to FIG.
In the method of manufacturing the composite piezoelectric chip 4 of the present invention, the piezoelectric substrate 1 and the support substrate 2 are first bonded to obtain the composite piezoelectric substrate 3 (FIG. 1A). The piezoelectric substrate 1 and the supporting substrate 2 to be used, the bonding method, and the like can be performed in the same manner as described above.
Then, the piezoelectric body portion 5 of the composite piezoelectric substrate 3 is applied to the composite piezoelectric substrate 3 by using a blade having a particle size of 4.5 μm or less at a cumulative height of 50% defined by JIS R6001. By cutting a depth deeper than the thickness of the composite piezoelectric substrate (FIG. 1B) and then subdividing the composite piezoelectric substrate into which the cut was made (FIG. 1C), the side surface 5 of the piezoelectric portion of the composite piezoelectric chip 4 is obtained. A composite piezoelectric chip having a surface roughness (Ra) of 0.15 μm or less can be obtained.
In order to set the surface roughness (Ra) of the side surface 5 ′ of the piezoelectric body portion to 0.1 μm or less, it is only necessary to make a cut 6 using a blade having a smaller particle size of the polishing fine powder.

  It should be noted that the composite piezoelectric substrate 3 is subdivided by using a blade having a coarser finer particle size than the blade used for making the notch 6 deeper than the thickness of the piezoelectric body portion 5 of the composite piezoelectric substrate 3. By doing so, the life of the blade can be extended and the speed of subdivision can be increased, so that the composite piezoelectric chip 4 can be obtained with high productivity and low cost.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to this.

(Examples 1-5)
As a support substrate, the diameter is 4 inches (100 mm), the thickness is 215 μm, the surface roughness Ra of the bonded surface and the opposite surface is both 0.3 μm, the Young's modulus is 340 GPa, and the resistivity is 10 ¹⁵ Ω · An alumina substrate having a size of cm was prepared.
Moreover, as a piezoelectric substrate, the electrical conductivity is 2 × 10 ⁻¹¹ [Ω ⁻¹ · cm ⁻¹ ], and the diameter is 4 inches (100 mm) and rotated by 36 ° Y-cut lithium tantalate (LiTaO ₃ , hereinafter also referred to as LT). A substrate was prepared and finished so that the roughness of the front and back surfaces was 0.13 μm by double-sided rough polishing so that the thickness of the piezoelectric substrate was 160 μm.

And the ultraviolet curing adhesive which has an epoxy as a main component on the said alumina substrate was apply | coated uniformly on the bonding surface by spin coating.
Further, the bonding surface of the LiTaO ₃ substrate was washed, and the above-described adhesive was applied in the same manner, and the adhesive application surface of the alumina substrate and the adhesive application surface of the LiTaO ₃ substrate were bonded together.

Next, the bonded composite piezoelectric substrate was irradiated with ultraviolet rays having an illuminance of 50 mW / cm ² for 5 minutes to cure the adhesive. At this time, the thickness of the adhesive layer was uniformly 5 μm within the bonded substrate surface.
Then, after chamfering the composite piezoelectric substrate, the bonded substrate was cured at a temperature of 120 ° C. for 2 hours. Further, the thickness of the LiTaO ₃ substrate was set to 30 μm by polishing.

  When the warpage of the composite piezoelectric substrate was measured in an atmosphere at an ambient temperature of 23 ° C., it was 30 μm.

Next, the composite piezoelectric substrate was cut into a 1 mm square by a depth of 40 μm from the surface of the LiTaO ₃ substrate using dicing blades having various abrasive particle diameters shown in Table 1 having a tooth thickness of 0.15 mm.
Then, the tooth thickness is 0.13 mm, and the particle diameter of the abrasive grains is 48.0 ± 3 μm (particle diameter at 50% cumulative height: JIS R6001) with a dicing blade of 320 μm from the surface of the LiTaO ₃ substrate side. A 1 mm square composite piezoelectric chip was obtained.
When the shape of the composite piezoelectric chip was observed, there was no clear stepped portion or notch in the peripheral portion on the substrate side, and it was cut almost straight.

The produced 1 mm square composite piezoelectric chip was evaluated with a laser microscope (VK8700 manufactured by KEYENCE) for the chipping of the end face of the piezoelectric part and the surface roughness of the side face of the piezoelectric part.
After that, various subdivided composite piezoelectric chips were passed through 260 ° C reflow three times, and -40 ° C and 125 ° C were alternately applied for 100 cycles, and the composite piezoelectric chip was observed for cracks using a microscope. did. The number of samples is 500 chips for each cutting method. The observation results are shown in Table 1. Moreover, even if the chip shown in Table 1 is further exposed to an environment of 85 ° C./85% RH (relative humidity) · 1000 hours, 125 ° C. · 1000 hours, 121 ° C./100% RH · 100 hours, cracks and peeling will not occur in LT. Did not occur.

In addition, a surface acoustic wave resonator is formed on the composite piezoelectric substrate, and the composite piezoelectric chip that is subdivided in the same manner as described above is used to determine the electrical characteristics after the heat treatment by a network analyzer via a microwave prober. The result of measuring (S11) is shown in FIG. The surface acoustic wave resonator characteristics of the composite piezoelectric chip before the heat treatment were the same as those in FIG.
Further, when the temperature dependence of the antiresonance frequency of the resonator comprising the composite piezoelectric chip of the present invention was measured at 25 ° C. and 85 ° C., the frequency temperature coefficient was −28 ppm / ° C.

(Example 6)
A P-type silicon substrate having a diameter of 4 inches (100 mm), a thickness of 210 μm, and a resistivity of 1000 Ω · cm was prepared as a support substrate.
Moreover, as a piezoelectric substrate, the electrical conductivity is 2 × 10 ⁻¹¹ [Ω ⁻¹ · cm ⁻¹ ], and the diameter is 4 inches (100 mm) and rotated by 36 ° Y-cut lithium tantalate (LiTaO ₃ , hereinafter also referred to as LT). A substrate was prepared, and the thickness was adjusted by double-side polishing so that the thickness of the piezoelectric substrate was 160 μm.

Then, the cleanly washed P-type silicon substrate and the LiTaO ₃ substrate are arranged facing each other under reduced pressure plasma with a distance of about 5 mm, and after the plasma treatment, directly bonded at room temperature with reduced pressure, and then atmospheric pressure The base material of the composite piezoelectric substrate was obtained.
The composite piezoelectric substrate was chamfered. Further, the thickness of the LiTaO ₃ substrate was set to 30 μm by polishing. This bonded substrate was heat-treated at a temperature of 200 ° C. for 2 hours. When the warpage of the composite piezoelectric substrate was measured in an atmosphere at an ambient temperature of 23 ° C., it was 30 μm.

When the bonding surface of the composite piezoelectric substrate was observed with a transmission electron microscope, an inorganic thin film layer and an amorphous layer were not observed.
Next, the composite piezoelectric substrate has a tooth thickness of 0.15 mm from the surface side of the LiTaO ₃ substrate, and the particle size of the fine powder is 3.0 ± 0.00 mm at the cumulative height of 50% defined by JIS R6001. A dimming blade of 4 μm was cut into a 1 mm square by a depth of 40 μm at a speed of 1 mm / s. Subsequently, the same part as the above-mentioned cut portion was removed from the surface of the LiTaO ₃ substrate with a dicing blade having a tooth thickness of 0.13 mm and a particle size of 48.0 ± 3 μm at a cumulative height of 50%. A 1 mm square composite piezoelectric chip having a depth of 320 μm was cut into 1 mm square and subdivided.

When the shape of the obtained composite piezoelectric chip was observed, there was no clear stepped portion or notched portion at the peripheral portion on the substrate side, and it was cut almost straight.
Further, the chipping of the end face of the piezoelectric portion of the obtained composite piezoelectric chip was 4 μm at maximum. Further, when the surface roughness of the side surface of the piezoelectric body portion of the composite piezoelectric chip was evaluated with a laser microscope (VK8700 manufactured by KEYENCE), Ra was 0.03 μm, which was almost close to a mirror surface.
After that, the composite piezoelectric chip obtained by subdivision was passed through 260 ° C. reflow three times, and -40 ° C. and 125 ° C. were alternately applied for 100 cycles, and the composite piezoelectric chip was observed for occurrence of cracks with a microscope. did. The number of samples is 500 chips. As a result, no cracks or peeling occurred in LT.

Further, even when the composite piezoelectric chip was further exposed to an environment of 85 ° C./85% RH · 1000 hours, 125 ° C. · 1000 hours, 121 ° C./100% RH · 100 hours, LT did not crack or peel.
In addition, a surface acoustic wave resonator is formed on the composite piezoelectric substrate, and the electrical characteristics before and after the heat treatment of the composite piezoelectric chip cut in the same manner as described above are measured with a network analyzer through a microwave prober. The measurement result was the same as in FIG.
Further, when the temperature dependence of the antiresonance frequency of the resonator comprising the composite piezoelectric chip of the present invention was measured at 25 ° C. and 85 ° C., the frequency temperature coefficient was −25 ppm / ° C.

(Comparative Examples 1-4)
In the same manner as in Examples 1 to 5, the prepared composite piezoelectric substrate had a tooth thickness of 0.15 mm from the LiTaO ₃ substrate side and a depth of 40 μm with a dicing blade having various abrasive particle diameters shown in Table 2. Only 1mm square was cut. After that, a 1 mm square composite piezoelectric chip is prepared by subdividing in the same procedure as in the example, and then various composite piezoelectric chips are passed through 260 ° C. reflow three times, and then −40 ° C. and 125 ° C. alternately. Over 100 cycles, the composite piezoelectric chip was observed for occurrence of cracks with a microscope. The number of samples is 500 chips for each cutting method. The observation results are shown in Table 2.

その結果、前記複合圧電チップの圧電体部側面の面粗さ（Ｒａ）が、０．１５μｍより大きい複合圧電チップは、熱処理後に多数のチップのＬＴにワレが生じた。

As a result, in the composite piezoelectric chip having a surface roughness (Ra) of the side surface of the piezoelectric body of the composite piezoelectric chip larger than 0.15 μm, cracks occurred in the LT of many chips after the heat treatment.

(Comparative Example 5)
In the same manner as in Example 6, a composite P-type silicon and LiTaO ₃ substrate was obtained.
Next, the composite piezoelectric substrate has a tooth thickness of 0.15 mm from the surface side of the LiTaO ₃ substrate, and the particle size at the 50% cumulative height defined by JIS R6001 is 14.0 ± 1. A 1 mm square was cut at a depth of 40 μm with a dimming blade of 0 μm at a speed of 5 mm / s.
Subsequently, with a dicing blade having a tooth thickness of 0.13 mm and a particle size of 48.0 ± 3 μm at a 50% cumulative height, the same part as the incised portion was removed from the surface of the LiTaO ₃ substrate. A 1 mm square composite piezoelectric chip having a depth of 320 μm was cut into 1 mm square and subdivided.
When the shape of the chip was observed, the peripheral edge on the substrate side had no clear stepped portion or notched portion, and was cut almost straight. The maximum chipping of the piezoelectric body end face of the composite piezoelectric chip was 20 μm.

  Moreover, when the surface roughness of the side surface of the piezoelectric body portion of the composite piezoelectric chip was evaluated with a laser microscope (VK8700, manufactured by KEYENCE), Ra was 0.65 μm. Thereafter, the composite piezoelectric chip obtained by cutting was subjected to 260 ° C. reflow three times, and then alternately subjected to 100 cycles of −40 ° C. and 125 ° C., and the occurrence of cracks was observed with a microscope with respect to the composite piezoelectric chip. . The number of samples is 500 chips. As a result, cracks occurred in LT of 13% of the composite piezoelectric chip.

(Comparative Example 6)
In the same manner as in Example 1, a composite alumina / LiTaO ₃ bonded substrate was obtained. Next, this composite piezoelectric substrate has a tooth thickness of 0.15 mm from the surface of the LiTaO ₃ substrate side, and the particle size at a cumulative height of 50% defined by JIS R6001 is 3.0 ± 0. A 1 mm square was cut by a depth of 20 μm from the surface of the LiTaO ₃ substrate at a speed of 1 mm / s with a 4 μm dicing blade.
Subsequently, the same portion as the cut portion is 320 μm from the surface of the LiTaO ₃ substrate on the surface with a dicing blade having a tooth thickness of 0.10 mm and a particle size of 48.0 ± 3 μm when the particle size of the abrasive fine powder is 50% cumulative. Was cut into 1 mm squares to obtain 1 mm square composite piezoelectric chips. When the shape of the chip was observed, a step portion of LiTaO ₃ was formed at the peripheral portion on the substrate side.

The maximum chipping of the upper end portion of the LiTaO ₃ of the composite piezoelectric chip was 5 μm. However, the maximum chipping at the lower part of the LiTaO ₃ step was about 100 μm.
Further, when the surface roughness of the side surface of the stepped portion of the LiTaO ₃ of the composite piezoelectric chip was evaluated with a laser microscope (VK8700 manufactured by KEYENCE Corp.), Ra was 0.04 μm.
Thereafter, the composite piezoelectric chip obtained by the above cutting method was passed through 260 ° C. reflow three times, and then -40 ° C. and 125 ° C. were alternately applied for 100 cycles. Observed. The number of samples is 500 chips. As a result, cracks occurred in LT of 19% of the composite piezoelectric chip.

  Compared with Examples 1-5, the comparative example 6 has a stepped portion on the side surface of the piezoelectric body portion, and the surface roughness of the entire side surface of the piezoelectric body portion of the piezoelectric chip is not less than 0.15 μm. It was found that the body part would crack. On the other hand, as in Examples 1 to 5, it was found that if the surface roughness of the entire side surface of the piezoelectric portion of the piezoelectric chip was 0.15 μm or less, no cracks were generated.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

  DESCRIPTION OF SYMBOLS 1 ... Piezoelectric substrate, 2 ... Support substrate, 3 ... Composite piezoelectric substrate, 4 ... Composite piezoelectric chip, 5 ... Piezoelectric body part of a composite piezoelectric substrate, 5 '... Side surface of the piezoelectric body part of a composite piezoelectric chip, 6 ... Cutting.

Claims (19)

  A composite piezoelectric chip obtained by subdividing a composite piezoelectric substrate obtained by bonding a piezoelectric substrate and a support substrate, wherein the composite piezoelectric chip cuts the composite piezoelectric substrate deeper than a thickness of a piezoelectric portion of the composite piezoelectric substrate. A composite piezoelectric chip, which is subdivided after being inserted, and has a surface roughness (Ra) of a side surface of the piezoelectric body of the composite piezoelectric chip of 0.15 μm or less.   2. The composite piezoelectric chip according to claim 1, wherein a surface roughness (Ra) of a side surface of the piezoelectric body portion of the composite piezoelectric chip is 0.10 μm or less.   The composite piezoelectric substrate is cut using a blade having a particle size of 4.5 μm or less at a cumulative height of 50% defined by JIS R6001. The composite piezoelectric chip according to claim 1 or 2.   4. The composite piezoelectric chip according to claim 1, wherein an electrode for detecting surface acoustic wave excitation is formed on the surface of the composite piezoelectric substrate. 5.   5. The composite piezoelectric chip according to claim 1, wherein the composite piezoelectric substrate is obtained by cutting the composite piezoelectric substrate into 5 μm to 20 μm deeper than a thickness of a piezoelectric body portion of the composite piezoelectric substrate. The composite piezoelectric chip according to any one of the above.   The composite piezoelectric chip according to claim 1, wherein the piezoelectric substrate has a thickness of 100 μm or less. The composite piezoelectric chip according to claim 1, wherein the piezoelectric substrate is made of any one of LiTaO ₃ and LiNbO ₃ .   The composite piezoelectric chip according to claim 1, wherein the support substrate has a thermal expansion coefficient smaller than that of the piezoelectric substrate.   The composite piezoelectric chip according to claim 1, wherein the support substrate is ceramic.   The composite piezoelectric chip according to any one of claims 1 to 9, wherein the support substrate is mainly composed of alumina.   The composite piezoelectric chip according to claim 1, wherein the support substrate is an insulator.   12. The composite piezoelectric substrate according to claim 1, wherein the piezoelectric substrate and the support substrate are bonded together with an adhesive to form a composite. Composite piezoelectric chip.   12. The composite piezoelectric substrate is obtained by combining the piezoelectric substrate and the support substrate by directly bonding them at room temperature without using an inorganic thin film layer or an amorphous layer. The composite piezoelectric chip according to any one of the above.   The composite piezoelectric chip according to claim 13, wherein the support substrate is a P-type silicon substrate having a resistivity of 1,000 Ω · cm or more.   A method of manufacturing a composite piezoelectric chip for subdividing a composite piezoelectric substrate obtained by bonding a piezoelectric substrate and a support substrate, wherein at least the composite piezoelectric substrate has a cumulative height of 50% as defined by JIS R6001 for the fine particle size of polishing fine powder. By using a blade having a particle diameter at a point of 4.5 μm or less to make a cut deeper than the thickness of the piezoelectric body portion of the composite piezoelectric substrate, and then subdividing the composite piezoelectric substrate into which the cut has been made, A method of manufacturing a composite piezoelectric chip, comprising obtaining a composite piezoelectric chip having a surface roughness (Ra) of a piezoelectric body portion side surface of the composite piezoelectric chip of 0.15 μm or less.   The composite piezoelectric substrate is subdivided by using a blade having a coarser particle size of the abrasive powder than a blade used for making a cut deeper than the thickness of the piezoelectric body portion of the composite piezoelectric substrate. The method for producing a composite piezoelectric chip according to claim 15.   17. The method of manufacturing a composite piezoelectric chip according to claim 15, wherein a surface roughness (Ra) of a side surface of the piezoelectric body portion of the composite piezoelectric chip is 0.10 μm or less. 17. .   18. The method of manufacturing a composite piezoelectric chip according to claim 15, wherein an electrode for detecting surface acoustic wave excitation is formed on a surface of the composite piezoelectric substrate. The cutting of the piezoelectric part is performed by making a notch 5 to 20 μm deeper than the thickness of the piezoelectric part of the composite piezoelectric substrate, and then subdividing the composite piezoelectric substrate into which the cut has been made. The method for manufacturing a composite piezoelectric chip according to claim 18.

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