JPH11355088A - Production of piezoelectric device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat device with satisfactory yield while facilitating handling even when a vibrating part is made thin by forming an exciting electrode at the vibrating part on the side of a first crystal plate before sticking first and second crystal plates, and grinding the first crystal plate into a prescribed thickness after sticking. SOLUTION: A first crystal plate 1 and a second crystal plate 2 previously sliced into prescribed thickness are prepared. A common electrode is formed with a laminated metal at a vibrating part 3 of the first crystal plate 1. By sticking the first and second crystal plates 1 and 2 and heating them for a fixed time, the crystal plates 1 and 2 are in tight contact. Next, the side of the first crystal plate 1 is mechanically ground until making the first crystal plate 1 into prescribed thickness. Next, the thickness of each element vibrating part is precisely adjusted by etching. At such a time, since a common electrode is previously formed between the first and second crystal plates 1 and 2, the thickness of the first crystal plate 1 can be easily measured while utilizing the reflection of laser light from the surface of the first crystal plate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a piezoelectric device such as a quartz oscillator or a quartz filter.

[0002]

2. Description of the Related Art Quartz resonators and quartz filters, which are piezoelectric devices, are obtained by slicing a quartz plate, which is a piezoelectric body, to a predetermined thickness and forming excitation electrodes serving as input / output electrodes on the front and back surfaces of a vibrating portion of the quartz plate. Thus, a specific frequency characteristic can be extracted between the input and output electrodes. Since the frequency at this time depends on the thickness of the quartz plate and the thickness of the input / output electrodes, the plate thickness has been adjusted by mechanical polishing in order to make the plate thickness of the quartz plate a predetermined thickness. .

At this time, when the oscillation frequency is in a high frequency region of 50 MHz or more, the thickness of the quartz plate needs to be 30 μm or less and handling becomes difficult. A frame structure that holds the vibrating portion may be bonded to the substrate, or a quartz plate and a reinforcing plate may be polished, and then the reinforcing plate side may be formed in the frame structure by etching. 7-
No. 74569), or a method in which a reinforcing plate is removed after polishing (see Japanese Patent Application Laid-Open No. 8-46475), or a recessed structure is etched by etching to reduce only a vibrating portion of a quartz plate having a certain thickness. (See JP-A-6-21740).

[0004]

However, when the above-mentioned frame-structured plate is polished, the vibrating portion is extremely thin, and the vibrating portion warps during polishing. The polishing finish was not flat, and the thickness of individual element portions in the substrate varied. Further, as shown in Japanese Patent Application Laid-Open No. 6-21740, when only the vibrating portion is cut out from a certain thickness by etching, the surface of the vibrating portion may be roughened by etching or may not be etched flat. is there.

In order to control the resonance frequency of the vibrating part of the quartz plate as disclosed in JP-A-7-74569 and JP-A-8-46475, an electrode and a reinforcing plate are previously provided on a quartz plate or a reinforcing plate. Must be formed in advance, and a step of removing the electrode for measuring the resonance frequency is required later.

According to the present invention, when manufacturing a piezoelectric device such as a quartz oscillator or a quartz filter, it is easy to handle even if the thickness of the vibrating portion is reduced, the vibrating portion is formed flat, and the vibration portion is formed in the substrate. Thickness variation of individual element parts is small, and through holes and slits can be easily formed in the vibrating part, even after polishing when joining the quartz plate and the reinforcing plate, without removing the electrode formed on the quartz plate, The object is to manufacture a piezoelectric device capable of oscillating a fundamental wave in a stable high-frequency region with a good yield up to the formation of electrodes on a wafer.

[0007]

According to the present invention, a first material substrate is polished to a certain thickness by polishing and then bonded to another second material substrate. At this time, between the first material substrate and the second material substrate, all or a part of one of the excitation electrodes is formed in the vibrating portion on the first material substrate side in advance. After this,
The first material substrate is polished to a predetermined thickness in a state where the first material substrate and the second material substrate are bonded to each other. After that, in the portion that becomes the element vibrating portion in the first material substrate, thickness variation occurs in the substrate, so that the vibrating portion of each element is individually etched to finely adjust the plate thickness. I do. During the etching, the plate thickness is measured by a laser microscope based on the eutectic point principle by utilizing the reflection from the excitation electrode formed between the first material substrate and the second material substrate from above the element.

Next, after one excitation electrode is formed on the surface of the first material substrate, the excitation electrode formed between the first material substrate and the second material substrate is pulled out. A through hole is formed in the portion. At the same time, a slit is formed in the first material substrate in order to reduce stress and spurious generated between the first material substrate and the second material substrate. next,
The second material substrate is hollowed by sandblasting, etching, or the like so that only the vibrating portion of the first material substrate remains. Furthermore, when only part of the excitation electrode formed between the first material substrate and the second material substrate is formed, the excitation electrode is formed from above. Finally, each element is divided to complete an element portion.

In this way, the steps up to the formation of the excitation electrodes on both surfaces of the first material substrate can be collectively performed in a wafer state, and the first material substrate and the second material substrate can be formed simultaneously. When the first material substrate is bonded, the excitation electrode formed first can be made thin, so that it is not necessary to form a concave portion on the first material substrate. The vibrating part is polished flat because it is pressed by the material substrate of the first material substrate, and the excitation electrode is formed between the first material substrate and the second material substrate. Can be easily measured with a laser microscope, enabling individual adjustment etching.
The thickness variation of the vibrating portion in the wafer is small, and the through-hole and the slit are formed in the vibrating portion of the first material substrate. This makes it possible to manufacture a piezoelectric device that oscillates with a fundamental wave with high yield.

[0010]

(Embodiment 1) FIG. 1 shows a structure of a quartz filter which is a piezoelectric device manufactured according to Embodiment 1 of the present invention, and FIG. 2 shows FIG. (Rear side). Reference numeral 1 denotes a first quartz plate, which is thin and has a thickness of 30 μm or less, and has divided electrodes 4 a and 4 b as excitation electrodes and a common electrode 5 formed on both surfaces of a vibrating part 3 surrounded by a dotted line. Further, extraction electrodes 7a, 7b, 7c, 7d for extracting the frequency signal of the vibration section 3 to the outside are formed. Reference numeral 2 denotes a second crystal plate, and a portion of the first crystal plate 1 corresponding to the vibrating portion 3 is cut out to form a frame structure for holding the vibrating portion 3. Further, the vibrating section 3 is provided with a through hole 6, and the common electrode 5 is drawn out through the through hole 6 to the same surface as the divided electrodes 4a and 4b. Next, the manufacturing process of the crystal filter will be described with reference to the drawings.

First, as shown in FIG. 3, a first crystal plate 1 and a second crystal plate 2 which have been sliced in advance to a predetermined thickness are prepared, and a vibrating portion 3 of the first crystal plate 1 is provided with a common electrode. 5 is made of a laminated metal made of Ti, Au or the like.
As shown in FIG.
By heating at a temperature of not less than ℃ for a certain period of time, these two quartz plates are completely adhered. At this time, if the thickness of the common electrode 5 is too large, the two quartz plates will not adhere to each other. Therefore, it is desirable to make the thickness sufficiently smaller than 100 °. May be formed on the common electrode 5 with the same material at the end of the present embodiment.

Next, as shown in FIG. 5, the first quartz plate 1 is mechanically polished until the first quartz plate 1 has a predetermined thickness. Next, fine adjustment of the thickness of each element vibrating portion is performed by etching. At this time, since the common electrode 5 is formed in advance between the first quartz plate 1 and the second quartz plate 2, the first quartz plate 1 is reflected from the surface of the first quartz plate 1 by the use of laser light. The thickness of the quartz plate 1 can be easily measured. By doing so, the vibrating part 3 of the first quartz plate 1 is held by the second quartz plate 2 from the back side, so that the thickness becomes flat even when polishing thinly, and the individual elements Even when the thickness of the vibrating section 3 is finely adjusted by etching, the thickness measurement of the vibrating section 3 becomes easy.

Next, as shown in FIG. 6, a mask 9 is applied to the surface B of the first quartz plate 1, and through holes 6 are formed in the vibrating portion 3 of the first quartz plate 1 by sandblasting, etching or the like.
At this time, the through holes 6 need only penetrate only the first quartz plate 1. By doing so, even when the first crystal plate 1 is thin, the second crystal plate 2 holds the through-holes 6 easily. 9 and 10, a slit 10 may be formed in the first quartz plate 1 at the same time by sandblasting or etching. The slit 10 is used to hold the vibrating portion 3 of the first quartz plate at four points, thereby forming the second quartz plate.
Of the crystal plate and the influence of the spurious.

Next, the mask 9 is peeled off, and as shown in FIGS. 7 and 8, the divided electrodes 4a and 4b serving as excitation electrodes and the extraction electrodes 7a, 7b, 7c and 7d are formed on the B surface of the first quartz plate 1. To form At this time, conduction between the common electrode 5 formed on the A surface of the vibrating portion 3 of the first quartz plate 1 and the extraction electrodes 7 b and 7 d is secured through the through-hole 6.

Finally, the second quartz plate 2 is placed on the mask A by the mask 11 so that only the vibrating portion 3 of the first quartz plate 1 is left.
And the cavity portion 12 is removed by sandblasting or etching. Also, as described above, if the thickness of the common electrode 5 provided first is too small, an electrode having a predetermined thickness is further formed on the common electrode 5 as reinforcement. Finally, each element is divided to complete an element portion.

In this embodiment, by using the same material of quartz as the first material substrate and the second material substrate in this manner, oscillation is performed in a stable high-frequency region with excellent temperature characteristics. The crystal filter can be manufactured in a batch in the state of a wafer.

The order of forming the through holes 6 and the slits 10 and the divided electrodes 4a and 4b may be reversed, but in this case, after the through holes 6 and the slits 10 are formed, the conductive reinforcement around the through holes 6 is formed. It is desirable to form a reinforcing electrode. Thus, even when the divided electrodes 4a and 4b are formed by photolithography, the through holes 6 and the slits 10 do not hinder the formation of the resist for photolithography, and the divided electrodes 4a and 4b are easily formed. Will be able to do it.

In this embodiment, an example is shown in which quartz is used as the first material substrate. However, it is not particularly necessary to use quartz, and a material having piezoelectric characteristics such as a lithium tantalate substrate and a lithium niobate substrate is used. If applicable.

(Embodiment 2) Next, Embodiment 2 will be described with reference to FIGS. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Embodiment 2 differs from Embodiment 1 in that FIG.
Is replaced with the glass plate 22 as shown in FIG.
By doing so, since the etching rate of glass and quartz with respect to an etching solution such as hydrofluoric acid is completely different, the glass plate 2 has a structure for holding the vibrating portion 3 of the first quartz plate 1.
2 becomes easier. When the difference in the coefficient of thermal expansion between the first quartz plate 1 and the glass plate 22 affects the characteristics, the slits 10 are formed at the same time as the formation of the through holes 6, and the glass plate 22 is etched away. Later,
Since the vibrating portion 3 of the first crystal plate 1 is supported at four points, a crystal filter that is less affected by temperature distortion and spurious due to a difference in thermal expansion coefficient can be provided.

In the step of heating after bonding the glass and the crystal, it is desirable to perform heating at a low temperature of about 200 ° C. for a long time. This is because if performed at an excessively high temperature, damage may occur due to the difference in the coefficient of thermal expansion between quartz and glass.

In this embodiment, an example in which a quartz plate is used as the first material substrate has been described. However, it is not necessary to use a quartz crystal in particular, and a substrate exhibiting piezoelectric characteristics such as a lithium tantalate substrate or a lithium niobate substrate If applicable. Also in this case, the frame structure can be easily formed on the glass side by utilizing the difference in the etching rate between the glass and the piezoelectric substrate.

(Embodiment 3) Although Embodiments 1 and 2 have described a quartz filter, the present invention is also applicable to a quartz resonator. Next, a brief description will be given of a method of manufacturing the crystal resonator. FIG. 13 and FIG. 14 are views of the crystal resonator according to the present embodiment. In the first embodiment, 31 is a first crystal plate as the first material substrate, and 32 is a second crystal plate as the second material substrate. An excitation electrode 34 is formed on the vibrating part 33 of the first quartz plate 31,
The excitation electrode 35 on the back surface is connected to the excitation electrode 34 through the through hole 36.
Has been pulled out on the same side as. Further, since the slit 38 is formed and the vibrating portion 33 is cantilevered, the influence of the stress distortion with the second quartz plate 32 is reduced. The second crystal plate 32 has a structure in which a portion of the first crystal plate 31 corresponding to the vibrating portion 33 is hollowed out to hold the vibrating portion 33. 37a,
Reference numeral 37b denotes an extraction electrode for extracting a signal from the vibration section 33 to the outside.

Further, the second quartz plate 32 may be made of glass. In this case, the portion of the quartz plate 31 corresponding to the vibrating portion 33 can be easily etched and etched.

In the present embodiment, an example in which quartz is used as the first material substrate has been described. However, it is not necessary to use quartz in particular, and a material having piezoelectric characteristics such as a lithium tantalate substrate or a lithium niobate substrate is used. If applicable.

[0025]

According to the present invention, after a first material substrate is polished to a certain thickness by polishing, it is bonded to another second material substrate, and the surface of the first material substrate is mechanically polished to a predetermined thickness. When the first material substrate and the second material substrate are polished, one excitation electrode is thin enough between the first material substrate and the second material substrate in advance so that the first material substrate and the second material substrate can be subjected to atomic bonding. By forming it on the vibrating part of the material substrate, the first material substrate can be joined without forming a concave portion.
Since the vibrating part is held down by the second quartz plate, the vibrating part is polished flat and the thickness of each element part can be easily measured by a method such as a laser microscope. Makes it possible to reduce the thickness variation of the vibrating part in the wafer,
Further, even when a through hole and a slit are formed in the vibrating portion of the first material substrate, the second material substrate is pressed down, and the through hole and the slit can be easily formed. Thus, a piezoelectric device that oscillates with a stable fundamental wave even in a high-frequency region can be manufactured on a wafer at a time with a high yield.

[Brief description of the drawings]

FIG. 1 is a perspective view of a crystal filter according to a first embodiment of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a sectional view of the first embodiment before the first and second quartz plates are bonded together.

FIG. 4 is a cross-sectional view when these are laminated.

FIG. 5 is a cross-sectional view when the first quartz plate is polished.

FIG. 6 is a cross-sectional view when a mask for a through hole is applied to the first quartz crystal plate side.

FIG. 7 is a cross-sectional view in which a division electrode and an extraction electrode are formed on a first quartz plate, and a mask for forming a cavity is formed on a second quartz plate.

FIG. 8 is a sectional view in which a cavity is formed in a second quartz plate.

FIG. 9 is a perspective view of another crystal filter according to the first embodiment of the present invention.

FIG. 10 is a plan view of the same.

FIG. 11 is a perspective view of a crystal filter according to a second embodiment of the present invention.

FIG. 12 is a plan view of the same.

FIG. 13 is a perspective view of a crystal resonator according to a third embodiment of the present invention.

FIG. 14 is a plan view of the same.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st quartz plate 2 2nd quartz plate 3 vibrating part 4a, 4b excitation (division) electrode 5 common electrode 6 through-hole 7a, 7b, 7c, 7d extraction electrode 10 slit

Claims (8)

[Claims] A step of polishing the first piezoelectric substrate to a predetermined thickness in a state where a first piezoelectric substrate having a vibrating portion and a second piezoelectric substrate holding the vibrating portion are bonded to each other; Forming a frame structure supporting the vibrating portion by removing a portion of the second piezoelectric substrate corresponding to the vibrating portion, the first piezoelectric substrate and the second piezoelectric substrate A method for manufacturing a piezoelectric device, comprising: forming all or a part of one of input and output electrodes of an element on a first piezoelectric substrate before bonding the elements. 2. After the first piezoelectric substrate and the second piezoelectric substrate are bonded to each other, and before the frame structure is formed on the second piezoelectric substrate, the vibrating portion of the first piezoelectric substrate is used. The method for manufacturing a piezoelectric device according to claim 1, wherein the through-hole is provided by sandblasting or etching. 3. After the first piezoelectric substrate and the second piezoelectric substrate are bonded to each other, and before the frame structure is formed on the second piezoelectric substrate, the vibrating portion of the first piezoelectric substrate is applied to the first piezoelectric substrate. 2. The method according to claim 1, wherein the slit is formed by sandblasting or etching. 4. A step of polishing a piezoelectric substrate to a predetermined thickness in a state where a piezoelectric substrate having a vibrating part and a glass substrate holding the vibrating part are bonded to each other, and Forming a frame structure that supports the vibrating section by removing a portion to be formed, and before bonding the piezoelectric substrate and the glass substrate, all or one of the input / output electrodes of the element or A method for manufacturing a piezoelectric device, wherein a part of the electrode is formed on a piezoelectric substrate, and the thickness of the electrode formed at this time is reduced so that the piezoelectric substrate and the glass substrate are completely adhered to each other. 5. A through hole is provided in a vibrating portion of the piezoelectric substrate by sandblasting or etching before the frame structure is formed on the glass substrate after the piezoelectric substrate and the glass substrate are bonded to each other. Item 5. The method for manufacturing a piezoelectric device according to Item 4. 6. A slit is formed in the vibrating part of the piezoelectric substrate by sandblasting or etching before the frame structure is formed on the glass substrate after the piezoelectric substrate and the glass substrate are bonded to each other. 5. The method for manufacturing a piezoelectric device according to item 4. 7. When the thickness of the vibrating portion of the first piezoelectric substrate is finely adjusted by polishing or etching, an excitation electrode formed between the first piezoelectric substrate and the second piezoelectric substrate is formed. 2. The method for manufacturing a piezoelectric device according to claim 1, wherein the thickness of the vibrating portion is measured by using a part thereof. 8. When finely adjusting the thickness of the vibrating portion of the piezoelectric substrate by polishing or etching, a part of an excitation electrode formed between the piezoelectric substrate and the glass substrate is used.
5. The method according to claim 4, wherein the thickness of the vibrating part is measured.