JP5363092B2 - Method of manufacturing composite substrate for surface acoustic wave filter and composite substrate for surface acoustic wave filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress chipping of an edge part of a piezoelectric substrate of a compound substrate formed by sticking the piezoelectric substrate and a support substrate together when a surface of the piezoelectric substrate is processed with polishing abrasive grains. <P>SOLUTION: A silicon substrate 12 is prepared, and also an LT substrate is prepared which has an external diameter taking of a margin corresponding to a position shift made in sticking into consideration for a length obtained by subtracting a beveled part from the external diameter of the silicon substrate 12 (Fig.5(a)). Then the LT substrate 10 has its backsides coated with an organic adhesive 13 and is stuck on the silicon substrate 12 to form a stuck substrate 16 (Fig.5(b)). Further, slurry containing polishing abrasive grains is supplied to between a surface of the LT substrate 10 and a polishing surface plate and the surface of the LT substrate 10 is polished by the polishing surface plate to polish the surface into a mirror plane while reducing the thickness of the LT substrate 10 (Fig.5(c)). <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for manufacturing a composite substrate and a composite substrate.

Conventionally, it is known to provide an acoustic wave element by providing an electrode on a composite substrate in which a support substrate and a piezoelectric substrate are bonded together. Here, the acoustic wave element is used, for example, as a band-pass filter in a communication device such as a mobile phone. A composite substrate using lithium niobate or lithium tantalate as a piezoelectric substrate and silicon or quartz as a supporting substrate is known (see Patent Document 1).
JP 2006-319679 A

  By the way, such a composite substrate is often manufactured by preparing a piezoelectric substrate and a supporting substrate, bonding these substrates together with an organic adhesive layer interposed therebetween, and then reducing the thickness of the piezoelectric substrate. Here, since the corner portion of the substrate hits something and breaks during handling, the piezoelectric substrate is usually chamfered. When the thickness of the piezoelectric substrate is reduced, polishing abrasive grains are interposed between the surface of the piezoelectric substrate and the polishing surface plate, and the surface of the piezoelectric substrate is polished by the polishing surface plate. However, in such a manufacturing method, when the piezoelectric substrate and the support substrate are bonded together, the edge portion is in a state where the piezoelectric substrate is separated from the organic adhesive layer by the amount of chamfering. Even when the bonding position is shifted, the edge portion of the piezoelectric substrate may be in a state of being separated from the organic adhesive layer. When the surface of the piezoelectric substrate is polished with a polishing surface plate in this state, there is a problem that many chips are generated starting from a portion apart from the edge.

  The present invention has been made in view of the above-described problems. For a composite substrate in which a piezoelectric substrate and a support substrate are bonded together, the edge portion of the piezoelectric substrate when the surface of the piezoelectric substrate is treated with abrasive grains. The main purpose is to suppress the occurrence of chipping.

  The present invention adopts the following means in order to achieve the above-mentioned object.

The method for producing the composite substrate of the present invention comprises:
(A) A piezoelectric substrate having an angled state in which the outer diameter is smaller than or the same as the diameter of the flat portion of the surface of the support substrate and at least the corner to be bonded to the support substrate is not chamfered Preparing a substrate;
(B) When forming the bonded substrate by bonding the front surface of the support substrate and the back surface of the piezoelectric substrate through an organic adhesive layer, the outer peripheral surface of the piezoelectric substrate is the same as the outer peripheral surface of the organic adhesive layer Bonding to be on the surface or located inside the outer peripheral surface of the organic adhesive layer; and
(C) Abrasive grains are interposed between the surface of the piezoelectric substrate and a polishing surface plate, and the surface of the piezoelectric substrate is polished by the polishing surface plate to reduce the thickness of the piezoelectric substrate and the piezoelectric substrate. Mirror polishing the surface of the substrate;
Is included.

The composite substrate of the present invention is
A support substrate;
An outer diameter smaller than or equal to the diameter of the flat portion of the surface of the support substrate, and at least a corner of the side to be bonded to the support substrate is not chamfered;
An organic adhesive layer for bonding the piezoelectric substrate and the support substrate;
With
The outer peripheral surface of the piezoelectric substrate is on the same plane as the outer peripheral surface of the organic adhesive layer or is located on the inner side of the outer peripheral surface of the organic adhesive layer.

  According to the method for manufacturing a composite substrate of the present invention, when the step (c) is performed, the piezoelectric substrate has an outer diameter smaller than or equal to the diameter of the flat portion of the surface of the support substrate and is attached to at least the support substrate. The corners on the mating side are not chamfered and are in a standing state. In addition, the surface of the support substrate and the back surface of the piezoelectric substrate are arranged such that the outer peripheral surface of the piezoelectric substrate is flush with the outer peripheral surface of the organic adhesive layer or is located inside the outer peripheral surface of the organic adhesive layer. It is bonded through an organic adhesive layer. For this reason, the edge of the piezoelectric substrate is not separated from the organic adhesive layer, as compared to the case where the edge of the piezoelectric substrate is separated from the organic adhesive layer due to misalignment or chamfering when bonded. As a result, chipping hardly occurs. Therefore, it is possible to suppress the occurrence of chipping at the edge of the piezoelectric substrate when the surface of the piezoelectric substrate is treated with the abrasive grains for the composite substrate in which the piezoelectric substrate and the support substrate are bonded together. The reason for this is that when the edge of the piezoelectric substrate is separated from the organic adhesive layer, when the surface of the piezoelectric substrate is polished, the edge becomes a sharp edge, which is due to the force acting in the thickness direction of the piezoelectric substrate during polishing. This is probably because the chipping is not easily caused when the edge of the piezoelectric substrate is not separated from the organic adhesive layer.

  In the method for producing a composite substrate of the present invention, in step (a), the outer diameter is smaller than or equal to the diameter of the support substrate and the flat portion of the surface of the support substrate, and at least the side to be bonded to the support substrate And a piezo-electric substrate in an angled state in which the corners are not chamfered. Here, examples of the piezoelectric substrate include a substrate capable of propagating an elastic wave (particularly, a surface acoustic wave). The material of the piezoelectric substrate is lithium tantalate, lithium niobate, lithium niobate-lithium tantalate solid solution. Single crystal, lithium borate, langasite, crystal and the like can be mentioned. This piezoelectric substrate is in an angled state where the corner on the side to be bonded to the support substrate is not chamfered. Further, the corner of the piezoelectric substrate opposite to the side to be bonded to the support substrate may be chamfered in advance. Even if the chamfered part hits something, it is hard to chip. Here, the chamfering may be a C chamfer in which an intersection (ridge) between two surfaces is cut at a predetermined angle, or an R chamfer cut so that the ridge has a predetermined radius of curvature. It may be. For example, a metal or silicon dioxide layer having a thickness of 0.1 to 5 μm may be provided on the back surface of the piezoelectric substrate. The supporting substrate is made of silicon, sapphire, aluminum nitride, alumina, borosilicate glass, quartz glass, lithium tantalate, lithium niobate, lithium niobate-lithium tantalate solid solution single crystal, lithium borate, langasite. And crystal. The support substrate may also be chamfered in advance. Further, when the corner of the support substrate to be bonded to the piezoelectric substrate is chamfered, the diameter of the flat portion on the surface of the support substrate is obtained by removing the chamfered portion from the outer diameter of the support substrate.

  In the method for producing a composite substrate of the present invention, in the step (b), when the bonded substrate is formed by bonding the front surface of the support substrate and the back surface of the piezoelectric substrate through an organic adhesive layer, Bonding is performed so that the outer peripheral surface is flush with the outer peripheral surface of the organic adhesive layer or is located on the inner side of the outer peripheral surface of the organic adhesive layer. For example, an organic adhesive is uniformly applied to one or both of the front surface of the support substrate and the back surface of the piezoelectric substrate, and the bonded substrate is formed by solidifying the organic adhesive in a state where both are overlapped. In particular, it is preferable that an organic adhesive is applied to the back surface of the piezoelectric substrate, the piezoelectric substrate and the support substrate are bonded together, and the organic adhesive is solidified to form an organic adhesive layer. In this way, since there is no organic adhesive layer outside the outer peripheral surface of the piezoelectric substrate, the organic adhesive layer is peeled off when polishing the surface of the piezoelectric substrate, and becomes attached to the surface of the piezoelectric substrate or finishes the surface. Can be prevented from adversely affecting. Here, examples of the method for applying the organic adhesive include spin coating and printing. Examples of the organic adhesive include an epoxy adhesive and an acrylic adhesive. Further, when a support substrate having a smaller thermal expansion coefficient than that of the piezoelectric substrate is prepared in the step (a), the thickness of the organic adhesive layer formed by heating is preferably 0.1 to 1.0 μm. . In such a case, for example, the piezoelectric substrate is made of a material selected from the group consisting of lithium tantalate, lithium niobate and lithium niobate-lithium tantalate solid solution, lithium borate, langasite, and quartz. The support substrate may be made of a material selected from the group consisting of silicon, sapphire, aluminum nitride, alumina, borosilicate glass, and quartz glass. In this way, when a surface acoustic wave element is manufactured using the finally manufactured composite substrate, an element in which a change in frequency characteristics with respect to a temperature change is relatively suppressed can be manufactured. If the thickness of the organic adhesive layer exceeds 1.0 μm, the difference in thermal expansion coefficient between the piezoelectric substrate and the support substrate is absorbed by the organic adhesive layer, and the effect of suppressing the change in frequency characteristics with respect to temperature change is not obtained. Absent. Moreover, when the thickness of the organic adhesive layer is less than 0.1 μm, it is not preferable because the effect of suppressing the change of the frequency characteristic with respect to the temperature change cannot be obtained due to the influence of the void.

  In the composite substrate manufacturing method of the present invention, in step (c), polishing abrasive grains are interposed between the surface of the piezoelectric substrate and the polishing surface plate, and the surface of the piezoelectric substrate is polished by the polishing surface plate. Thus, the thickness of the piezoelectric substrate is reduced and the surface of the piezoelectric substrate is mirror-polished. As an apparatus used at a process (c), a common grinder is mentioned. For example, in a polishing machine that polishes one side of a bonded substrate, first, the bonded substrate to be polished is pressed between the pressure plate and the polishing surface plate, and then polished between the bonded substrate and the polishing surface plate. The piezoelectric substrate is thinned by applying a rotational motion to the pressure plate while supplying slurry containing abrasive grains. Subsequently, the surface of the piezoelectric substrate is mirror-finished by changing the polishing surface plate to a higher one and giving the rotation and revolution motion to the pressure plate. Grind. In the bonded substrate provided in this step (c), since the edge portion of the piezoelectric substrate is not separated from the organic adhesive layer, the edge portion is organic when the surface of the piezoelectric substrate is treated with abrasive grains. Compared with a substrate separated from the adhesive layer (for example, a bonded substrate in which all the corners are chamfered and a substrate having the same size and a support substrate are bonded), chipping at the edge of the piezoelectric substrate is less likely to occur. .

  The cross section of the specific example of the composite substrate manufactured by the manufacturing method of the composite substrate mentioned above is shown in FIGS. In the figure, the part surrounded by the alternate long and short dash line indicates the part removed by polishing in the step (c). FIG. 1 shows that a piezoelectric substrate having an outer diameter smaller than the diameter of the flat portion on the surface of the support substrate and having a corner not chamfered, and the support substrate, and an organic adhesive on the back surface of the piezoelectric substrate. Was applied to form a bonded substrate so that the outer peripheral surface of the piezoelectric substrate was flush with the outer peripheral surface of the organic adhesive layer (see the parentheses), and then the piezoelectric substrate was polished. It is a composite substrate. 1 indicates the bonded substrate obtained in the step (b). In FIG. 2, first, a piezoelectric substrate in a state where the outer diameter is smaller than the diameter of the flat portion of the surface of the support substrate and the corners are not chamfered, and the support substrate are bonded to the surface of the support substrate with an organic adhesive. The composite substrate is obtained by coating the substrate so that the outer peripheral surface of the piezoelectric substrate is positioned inside the outer peripheral surface of the organic adhesive layer to form a bonded substrate, and then polishing the piezoelectric substrate. In FIG. 3, first, a piezoelectric substrate having an outer diameter smaller than the diameter of the flat portion on the surface of the support substrate and having a corner that is not chamfered on the side to be bonded to the support substrate, and the support substrate are An organic adhesive is applied to the back surface of the substrate and bonded so that the outer peripheral surface of the piezoelectric substrate is flush with the outer peripheral surface of the organic adhesive layer to form a bonded substrate, and then the piezoelectric substrate is polished. Composite substrate. FIG. 4 is a plan view of supporting a support substrate and a piezoelectric substrate in a standing state in which the diameter of the flat portion on the surface of the support substrate is the same as the outer diameter and the corner on the side to be bonded to the support substrate is not chamfered. An organic adhesive is applied to one or both of the front surface of the substrate and the back surface of the piezoelectric substrate, and bonded so that the outer peripheral surface of the piezoelectric substrate is flush with the outer peripheral surface of the organic adhesive layer to form a bonded substrate. Thereafter, the composite substrate obtained by polishing the piezoelectric substrate. Since any composite substrate is manufactured by the above-described manufacturing method, the edge portion of the piezoelectric substrate is less chipped. In addition, since the organic adhesive layer does not exist outside the outer peripheral surface of the piezoelectric substrate in the composite substrate of FIGS. 1, 3, and 4, when the surface of the piezoelectric substrate is polished, the organic adhesive layer is peeled off to become dust, and the piezoelectric substrate It does not adhere to the surface or adversely affect the finish of the surface.

  Further, the composite substrate of the present invention has an outer diameter smaller than or equal to the diameter of the support substrate and the flat portion of the surface of the support substrate, and at least the corner on the side to be bonded to the support substrate is not chamfered. A piezoelectric substrate in an angled state, and an organic adhesive layer that bonds the piezoelectric substrate and the support substrate, and whether the outer peripheral surface of the piezoelectric substrate is flush with the outer peripheral surface of the organic adhesive layer Or it is located inside the outer peripheral surface of the organic adhesive layer. Such a composite substrate can be manufactured, for example, by the above-described composite substrate manufacturing method.

[Example 1]
FIG. 5 is a cross-sectional view schematically showing the manufacturing process of the composite substrate of this example. First, a silicon substrate 12 having an orientation flat portion (OF portion), a diameter of 100 mm (4 inches), and a thickness of 350 μm was prepared as a support substrate. In addition, a lithium tantalate substrate (LT substrate) 10 having an OF portion, a diameter of 98 mm, and a thickness of 250 μm was prepared as a piezoelectric substrate (FIG. 5A). Here, the corners of the silicon substrate 12 are chamfered. FIG. 6 is a partial cross-sectional view for explaining the chamfered portion. As shown in the drawing, chamfering starts from a position 300 μm inside from the outer peripheral surface of the silicon substrate 12, and the chamfering angle at this position is 20 °. The LT substrate 10 is a 36 ° Y-cut X-propagation LT substrate in which the propagation direction of surface acoustic waves (SAW) is X and the cutting angle is a rotating Y-cut plate. The outer diameter of the LT substrate 10 is obtained by subtracting the chamfered portion (0.6 mm) from the outer diameter (100 mm) of the silicon substrate 12 to obtain the diameter of the flat portion on the surface of the silicon substrate 12, and this diameter (99.4 mm). In addition, the margin corresponding to the maximum amount of positional deviation assumed at the time of bonding is set to 98 mm. In addition, the LT substrate 10 was prepared in a state where the chamfered portion of the chamfered substrate was cut off so that all corners were not chamfered. Next, the epoxy adhesive 13 is applied to the LT substrate 10 by spin coating, the silicon substrate 12 is pasted and heated to 180 ° C., and the thickness of the organic adhesive layer 14 (the layer in which the epoxy adhesive 13 is solidified) is 0. A bonded substrate 16 having a thickness of 3 μm was formed (FIG. 5B). At this time, after bonding, the outer peripheral surface of the LT substrate 10 and the outer peripheral surface of the organic adhesive layer 14 were on the same plane.

  Subsequently, it grind | polished until the thickness of LT board | substrate 10 was set to 30 micrometers with the grinder (FIG.5 (c)). As the polishing machine, a machine that performs mirror polishing after reducing the thickness as follows was used. That is, when the thickness is reduced, the bonded substrate 16 is sandwiched between the polishing platen and the pressure plate, and a slurry containing abrasive grains is supplied between the bonded substrate 16 and the polishing platen. A pressure plate was used to rotate the pressure plate while pressing the laminated substrate 16 against the surface plate using a plate. Subsequently, when performing mirror polishing, the polishing surface plate is assumed to have a pad attached to the surface and the abrasive grains are changed to a high count, and by giving rotation and revolution motion to the pressure plate, A piezoelectric substrate whose surface was mirror-polished was used. First, the surface of the LT substrate of the bonded substrate 16 was pressed against the surface of the platen, and the rotation was performed at a rotation speed of 100 rpm and the polishing duration was 60 minutes. Subsequently, the polishing surface plate is assumed to have a pad attached to the surface, and the abrasive grains are changed to a higher one, the pressure for pressing the bonded substrate 16 against the surface plate is 0.2 MPa, rotation of rotation Mirror polishing was performed with a speed of 100 rpm, a revolution speed of 100 rpm, and a polishing duration of 60 minutes.

  FIG. 7 shows a state in which the edge of the LT substrate 10 is chipped when five composite substrates are manufactured in the same manufacturing process. FIG. 7 is a sketch created by visually confirming the chipping of the edge of the LT substrate 10. As shown in the drawing, no chipping was observed in the first to fifth composite substrates.

[Comparative Example 1]
A composite substrate was fabricated in the same manner as in Example 1 except that an LT substrate having the same outer diameter as that of the silicon substrate 12 and a chamfered corner to be bonded to the silicon substrate 12 was prepared. FIG. 8 shows a state in which the edge of the LT substrate 10 is chipped when five composite substrates are manufactured in the same manufacturing process. FIG. 8 is a sketch created by visually confirming the state of the chipping of the edge of the LT substrate 10. In the figure, the shaded portion is a portion where the LT substrate 10 is missing. As shown in the figure, for the first to fifth composite substrates, large chips were observed at a plurality of locations.

  From the results of Example 1 and Comparative Example 1, it was found that in Example 1, the occurrence of chipping of the LT substrate 10 during polishing was suppressed as compared with Comparative Example 1.

[Example 2]
A composite substrate was produced in the same manner as in Example 1 except that the thickness of the organic adhesive layer 14 was changed as shown in Table 1. Then, an input electrode and an output electrode made of metal aluminum were formed on the surface of the LT substrate on the prepared composite substrate to produce a SAW filter, and its thermal expansion coefficient and frequency temperature characteristics were measured. The measurement results are shown in Table 1. Here, the linear thermal expansion coefficient in the propagation direction X of the SAW of the LT substrate is 16 ppm / ° C. The linear expansion coefficient in the SAW propagation direction X of the single crystal silicon substrate is 3 ppm / ° C. As is apparent from the results in Table 1, it was found that the frequency temperature characteristics (temperature characteristics) are significantly improved by setting the thickness of the organic adhesive layer to 0.1 to 1.0 μm.

It is sectional drawing of the composite substrate manufactured with the manufacturing method of the composite substrate of this invention. It is sectional drawing of the composite substrate manufactured with the manufacturing method of the composite substrate of this invention. It is sectional drawing of the composite substrate manufactured with the manufacturing method of the composite substrate of this invention. It is sectional drawing of the composite substrate manufactured with the manufacturing method of the composite substrate of this invention. It is sectional drawing which shows the manufacturing process of a composite substrate typically. It is a fragmentary sectional view explaining a chamfer part. It is a sketch figure showing the mode of the chip of the edge of the LT substrate of an example. It is a sketch figure showing the mode of the edge notch of the LT board of a comparative example.

Explanation of symbols

  10 Lithium tantalate substrate (LT substrate), 12 Silicon substrate, 13 Organic adhesive, 14 Organic adhesive layer, 16 Bonded substrate.

Claims (4)

(A) A support substrate having a flat portion with a diameter smaller than the outer diameter on the surface, and an outer diameter smaller than or equal to the diameter of the flat portion, and at least a corner to be bonded to the support substrate is chamfered. A step of preparing a piezoelectric substrate in a non-square state;
(B) When forming the bonded substrate by bonding the front surface of the support substrate and the back surface of the piezoelectric substrate through an organic adhesive layer, the outer peripheral surface of the piezoelectric substrate is the same as the outer peripheral surface of the organic adhesive layer Bonding to be on the surface or located inside the outer peripheral surface of the organic adhesive layer; and
(C) Abrasive grains are interposed between the surface of the piezoelectric substrate and a polishing surface plate, and the surface of the piezoelectric substrate is polished by the polishing surface plate to reduce the thickness of the piezoelectric substrate and the piezoelectric substrate. Mirror polishing the surface of the substrate;
Including
In the step (a), a support substrate having a thermal expansion coefficient smaller than that of the piezoelectric substrate is prepared,
In the step (b), the organic adhesive layer has a thickness of 0.1 to 1.0 μm.
Manufacturing method of composite substrate for surface acoustic wave filter. In the step (b), an organic adhesive is applied to the back surface of the piezoelectric substrate, the piezoelectric substrate and the support substrate are bonded together, and the organic adhesive is solidified to form the organic adhesive layer.
The manufacturing method of the composite substrate for surface acoustic wave filters of Claim 1. The piezoelectric substrate is made of a material selected from the group consisting of lithium tantalate, lithium niobate and lithium niobate-lithium tantalate solid solution, lithium borate, langasite, crystal,
The support substrate is made of a material selected from the group consisting of silicon, sapphire, aluminum nitride, alumina, borosilicate glass, and quartz glass.
The manufacturing method of the composite substrate for surface acoustic wave filters of Claim 1 or 2. A support substrate;
An outer diameter smaller than or equal to the diameter of the flat portion of the surface of the support substrate, and at least a corner of the side to be bonded to the support substrate is not chamfered;
An organic adhesive layer for bonding the piezoelectric substrate and the support substrate;
With
The outer peripheral surface of the piezoelectric substrate is on the same plane as the outer peripheral surface of the organic adhesive layer or is located on the inner side of the outer peripheral surface of the organic adhesive layer,
The support substrate has a smaller coefficient of thermal expansion than the piezoelectric substrate , the diameter of the flat portion is smaller than the outer diameter of the support substrate,
The organic adhesive layer has a thickness of 0.1 to 1.0 μm.
Composite substrate for surface acoustic wave filter.

Images