JP2005026847A - Method of manufacturing piezoelectric transducer element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a piezoelectric transducer element which copes with the miniaturization (thinning) and improves the yield. <P>SOLUTION: The method of manufacturing a piezoelectric transducer element having a thick-walled vibrating part having a thicker central portion than a peripheral edge of a piezoelectric substrate has a first etching step of etching first and second gaps after covering element regions of the large piezoelectric substrate, corresponding to the piezoelectric transducer elements, support regions adjacent to the element regions across the first gaps and frame regions adjacent to the support regions across the second gaps with a protective film; and a second etching step of etching the piezoelectric substrate after covering vibrating regions corresponding to the vibrating part, the support regions, and the frame regions with the protective film. After piercing the first gaps by the first and second etching steps with leaving narrow joints tying the element regions and the support regions, the joints are bent and broken to obtain individual piezoelectric transducer elements. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a piezoelectric vibration element used for a vibrator, a filter, or the like, and more particularly to a method for manufacturing a piezoelectric vibration element that solves various problems that occur in the electrode forming process of a thin piezoelectric vibration element.
[0002]
[Prior art]
Due to the rapid progress of price reduction and miniaturization accompanying the popularization of mobile communication devices such as mobile phones, there is an increasing demand for price reduction and miniaturization of crystal units used in these communication devices. Accordingly, the trend is toward higher frequency of the crystal resonator, that is, the thinner crystal resonator element.
[0003]
Hereinafter, a conventional crystal resonator (crystal resonator element) will be described.
There is a conventional crystal resonator as disclosed in, for example, Japanese Patent Laid-Open No. 8-330883, and FIG. 16 is a perspective view showing the configuration thereof.
The excitation electrode 102 formed on both main surfaces of the quartz substrate 101 and the extraction electrode 103 extending from the excitation electrode 102 are regarded as etching masks, and the excitation electrode 102 and the extraction electrode 103 are not formed on the surface 104 (the crystal is formed on the surface). Is a quartz resonator element 100 in which the thickness of the exposed portion is reduced by wet etching.
[0004]
In the method of manufacturing the quartz crystal resonator 100, the excitation electrode 102 is formed by vapor deposition (CVD and PVD) so as to face the central portions of both main surfaces of the quartz substrate 101 processed to a thickness corresponding to a desired resonance frequency. In addition, the extraction electrode 103 extending from each of the excitation electrodes 102 to end edges in opposite directions is formed. Then, the quartz crystal substrate 101 is immersed in an etching solution as it is. As an etching solution used for this kind of purpose, a saturated aqueous solution of hydrogen fluoride, ammonium fluoride or the like is known. In this way, the excitation electrode 102 and the extraction electrode 103 serve as a mask, and these electrode portions are not etched even when immersed in an etching solution. Therefore, only the non-formed portion 104 is etched, the thickness of the non-formed portion 104 is reduced, and a step is formed between the non-formed portion 104 and the formed portion of the electrode, and the work-affected layer (formed during thickness processing) is removed by etching. Thereby, good vibration characteristics can be obtained.
[0005]
[Patent Document] JP-A-8-330883.
[0006]
[Problems to be solved by the invention]
As shown in FIG. 17, a general method for manufacturing a crystal resonator element, in particular, a method for forming the excitation electrode and the extraction electrode, includes a crystal substrate 101 provided in an intermediate plate 111 having substantially the same thickness as the crystal substrate 101. The quartz substrate 101 is inserted into a plurality of through-holes that substantially match the planar outer shape, and the quartz substrate 101 and the upper plate 112 having openings corresponding to the excitation electrode pattern and the extraction electrode pattern formed on one main surface of the quartz substrate 101 The lower plate 113 having an opening corresponding to the excitation electrode pattern and the extraction electrode pattern formed on the other main surface of the substrate is disposed opposite to the intermediate plate 111, and then the intermediate plate 111, the upper plate 112, and the lower plate 113 are disposed. And the excitation electrode 102 and the extraction electrode 103 are formed by vapor deposition. However, since the thin quartz substrate 101 has low mechanical strength, the quartz substrate 101 may be damaged when the quartz substrate 101 is gripped and inserted into the through hole, and its handling is extremely difficult.
Further, it is necessary to prepare the corresponding intermediate plate 111 for each thickness (resonance frequency) of the quartz substrate 101.
[0007]
There is a manufacturing method for obtaining a plurality of crystal resonator elements by adopting a large crystal substrate for batch processing in consideration of production efficiency, and dividing and dividing the crystal resonator elements partitioned on the large crystal substrate. . However, in order to obtain a resonance frequency of, for example, 100 MHz to 208 MHz in order to cope with a desired resonance frequency of the large quartz substrate, the thickness of the quartz substrate 101 is set to 16.7 to 8.03 μm (0.0167 to 0.0080 mm). In addition, in order to stabilize the oscillation waveform, it is extremely difficult to control the parallelism of both major surfaces of the large quartz substrate to be close to 0 (no variation).
Moreover, the large-sized quartz crystal substrate having a thin plate has a low mechanical strength, and a large-sized upper plate, a large-sized lower plate, and a large-sized frame plate (a large-sized middle plate are not required) for forming the electrode. Alternatively, the large crystal substrate may be damaged when it is removed or immersed in the etching solution, and handling of the thin large crystal substrate is extremely difficult.
Further, when the resist is coated with a spinner when the non-formed portion 104 is further processed, for example, when a step is formed by a photolithography process, the large quartz substrate is warped due to suction fixation by the spinner, and the resist film thickness is uneven. Therefore, there is a possibility that desired processing cannot be performed.
[0008]
SUMMARY An advantage of some aspects of the invention is that it provides a method for manufacturing a piezoelectric vibration element that can cope with downsizing (thinning) and improve yield.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention is a method of manufacturing a piezoelectric vibrating element in which the thickness of the central portion is made larger than the peripheral edge of the piezoelectric substrate and the pressed portion is used as a vibrating portion. An element region corresponding to the piezoelectric vibration element of a large piezoelectric substrate, a support region disposed with the element region separated from the first gap, and a support region disposed with the second gap disposed A first etching step of covering the frame region with a protective film and etching the gap of the piezoelectric substrate, and the vibration region corresponding to the vibrating unit, the support region, and the frame region with a protective film. And a second etching step for etching the piezoelectric substrate, and the first and second etching steps leave the narrow connection portion connecting the element region and the support portion region. After passing through the gap of 1, the connecting part is folded. Characterized in that to obtain a piezoelectric vibrating element of the individual pieces by dividing.
[0010]
According to a second aspect of the present invention, in the first aspect, the third etching step of covering one surface of the frame region with a protective film and etching the piezoelectric substrate, and the protective film in the third etching step The method includes a step of mounting an electrode mask on the piezoelectric substrate using the frame region covered with the substrate as a reference for alignment, and a film forming step of forming an electrode film through the electrode mask.
[0011]
According to a third aspect of the present invention, in the first aspect, a metal film is used as the protective film, and the metal film is left as a main electrode in the vibration region to remove another metal film, and a lead electrode mask And forming a lead electrode extending from the main electrode to the end of the element region by vapor deposition or sputtering.
[0012]
According to a fourth aspect of the present invention, in any one of the first to third aspects, the folding mask having an opening in the element region is located at an opening end portion at a connection portion between the element region and the connecting portion. As described above, the connecting portion is folded by being attached to the piezoelectric substrate.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on illustrated embodiments of the present invention.
[0014]
1A is a plan view of a crystal resonator element as a piezoelectric resonator element according to an embodiment of the present invention, FIG. 1B is a side view thereof, and FIG. 2A is an embodiment of the present invention. A top view showing a part of a large quartz substrate as a large piezoelectric substrate before folding (dividing into pieces) of the manufacturing method, and FIG.
A crystal resonator element 10 according to an embodiment of the present invention includes a substantially rectangular crystal resonator element body, for example, an AT-cut crystal, including a vibrating portion 1a and a thin stepped portion 1b surrounding the substantial center of the outer end surface of the vibrating portion 1a. A mesa-type crystal resonator element comprising a substrate 1, an excitation electrode 2 disposed substantially at the center of the vibration part 1a, and a lead electrode 3 extending from each of the excitation electrodes 2 to one end in the longitudinal direction. is there.
A large-sized quartz substrate 21 (partially shown) in which a plurality of quartz resonator elements 10 are partitioned is extended outward from the approximate center of the quartz resonator element 10 and the short side ends of the quartz resonator element 10 facing each other. The connecting portion 22, the frame portion 23 mechanically connected to the connecting portion 22, and a part of the frame portion 23, for example, if the large crystal substrate 21 is substantially rectangular, are arranged diagonally and opposite to each other A protrusion 23 a formed on the main surface, a support portion 24 formed substantially at the center of each connecting portion 22 and having substantially the same length as the short side of the crystal resonator element 10, and other adjacent to the crystal resonator element 10 And a gap (through between both main surfaces) 25 to a quartz crystal vibration element (not shown). The frame part 23 excluding the vibration part 1a, the support part 24, and the protrusion part 23a has the same thickness, and the connecting part 22 is thinner than the step part 1b. In FIG. 2B, one main surface (upper surface) of the right projection portion 23a is thicker upward (the lower surface substantially coincides with the lower surface of the support portion 24), and the other main surface of the left projection portion 23a ( The lower surface is thicker downward (the upper surface substantially coincides with the upper surface of the support portion 24).
[0015]
Hereinafter, a method for manufacturing a crystal resonator according to an embodiment of the present invention will be described based on FIGS. 3 to 15 with reference to FIGS.
As shown in FIG. 3, a gold / chrome metal film is attached to both main surfaces of a polished large crystal substrate 31 by vacuum deposition. Using a photolithographic process on each of the metal films, etching is performed on a portion to be the crystal resonator element 10 (element region 10z) and an etching mask pattern 32a and a portion to be the frame portion 23 (frame portion region 23z). The mask pattern 32b for etching and the mask pattern 32c for etching are formed in the portion (projection region 23az) that becomes the projection 23a and the mask pattern 32d for etching is formed in the portion (support region 24z) that becomes the support 24. That is, the metal film of the connecting portion 22 and the portion (the connecting portion region 22z and the gap region) that becomes the gap (not shown) is removed.
Next, the mask pattern 32a of the portion (stepped portion region 1bz) that becomes the stepped portion 1b on both main surfaces, the mask pattern 32c on the one main surface (upper surface) side on the right side in the drawing, and the other on the left side in the drawing A first photoresist (photosensitive resin) 33 coated with a spinner or the like is applied to the mask pattern 32c on the main surface (lower surface) side. Further, a second photoresist (photosensitive resin) coated with a spinner or the like on the mask pattern 32a and the mask patterns 32b to d of the part (vibration part region 1az) exposed on each of the main surfaces to become the vibration part 1a. ) 34 (protective film forming step), that is, the first photoresist 33 deposited on the stepped portion region 1bz on both main surfaces, the coupling portion region 22z, and the crystal plane of the gap region are exposed. It becomes a large crystal substrate.
[0016]
As shown in FIG. 4, the crystal surface exposed on both main surfaces, that is, the connecting portion region 22z and the gap region (not shown) are etched (first crystal etching step).
As shown in FIG. 5, the first photoresist 33 exposed on both main surfaces (attached to the stepped region 1bz) is removed (first photoresist removing step).
As shown in FIG. 6, etching is performed on a mask pattern (a part of the mask pattern 32 a) exposed on both main surfaces by removing the first photoresist 33 (first mask pattern etching step). Thus, the large crystal substrate in which the crystal surfaces of the coupling region 22z, the step region 1bz, and the gap region (not shown) on both main surfaces are exposed is obtained.
[0017]
As shown in FIG. 7, further etching is performed on the crystal surfaces (the coupling portion region 22z, the step portion region 1bz, and the gap region) exposed on both main surfaces (second crystal etching step).
As shown in FIG. 8, a part of the mask pattern 32a, the mask pattern 32b, and the mask pattern 32d are removed by stripping the second photoresist 34 (second photoresist stripping step). The mask pattern 32c on the lower surface side on the right side, the mask pattern 32c on the upper surface side on the left side in the drawing, the crystal surface of the coupling region 22z, the gap region and the step region 1bz on both main surfaces, and the mask pattern 32c. Thus, a large quartz substrate is obtained in which the first photoresist 33 and the mask patterns 32c and 32d deposited thereon are exposed.
[0018]
As shown in FIG. 9, the mask pattern exposed on both main surfaces is etched (second mask pattern etching step), in other words, the mask pattern 32c deposited on the projection region 23az and the mask pattern 32c. Only the first photoresist 33 is left.
As shown in FIG. 10, the crystal surface exposed by the previous process is further etched (third crystal etching process) to process the vibration region 1az to a thickness corresponding to a desired resonance frequency, and the gap The crystal in the region (not shown) is removed.
As shown in FIG. 11, the first photoresist 33 is stripped (third photoresist stripping step).
As shown in FIG. 12, the protrusion 23a is formed by etching the mask pattern 32c (third mask pattern etching step), and has the same shape as the large crystal substrate shown in FIG. Thus, a large quartz substrate (40) in which the excitation electrode and the lead electrode are not formed is completed.
[0019]
As shown in FIG. 13, the excitation electrode pattern is located at a position corresponding to a plurality of the quartz substrates 41 (the quartz oscillation element 10 in which the excitation electrodes and the lead electrodes are not formed) partitioned on the large quartz substrate 40. And a large vapor deposition mask 45 having an opening corresponding to the lead electrode pattern is placed on both main surfaces of the large quartz substrate 40, and the planar direction is based on the protrusion 23a and the thickness direction is based on the support 24. Position. The large vapor deposition masks 45 are fixed to each other by inserting a magnet (not shown) in any gap (fixing the inner main surfaces of the large vapor deposition mask 45 with the magnet interposed therebetween) or the arbitrary support portion 24. It becomes possible by placing the magnet 46 on the outer main surface of the large evaporation mask 45 located in the vicinity of (fixing the inner main surfaces of the large evaporation mask 45 with the support portion interposed therebetween) (deposition mask mounting step). ).
As shown in FIG. 14, a metal thin film 43 is deposited on both main surfaces (crystal surface) of the large quartz substrate 40 exposed from the large vapor deposition mask 45 simultaneously or by vapor deposition on both main surfaces (electrodes). Thus, the plurality of crystal resonator elements 10 (including the large crystal substrate 40) in which the excitation electrodes and the lead electrodes are formed on both main surfaces of each crystal substrate 41, that is, a plurality of crystal resonator elements 10 connected in series are formed.
[0020]
As shown in FIG. 15 (a), the large-sized vapor deposition mask is removed, and each crystal resonator of the crystal resonator element group 51 arranged in a line in the short direction of the plurality of crystal resonator elements included in the crystal substrate is arranged. A folding mask 50 is placed in alignment with the boundary between the end portion in the longitudinal direction and the connecting portion 22 mechanically connected to each of the end portions, and as shown in FIG. A plurality of the crystal resonator elements 10 can be obtained by repeating the folding operation (folding step).
[0021]
In the method of simultaneously forming the excitation electrode and the lead electrode through the large evaporation mask 45, the positional error between the excitation electrodes that affect the vibration characteristics of the mesa-type crystal resonator element is caused by the processing accuracy of the large evaporation mask. Depending on the accuracy of mounting on a large quartz substrate, there is a risk of increased manufacturing variation (deteriorating yield). Therefore, a large photomask having an opening corresponding to at least the excitation electrode pattern is placed at a position corresponding to the plurality of quartz substrates 41 that are partitioned and formed on the large quartz substrate 40 with the large quartz substrate interposed therebetween. Each main surface is individually subjected to a photolithography process to form the excitation electrode, thereby suppressing manufacturing variations (position error) of the excitation electrode, and forming lead electrodes that do not affect the vibration characteristics by vapor deposition. Can be improved.
[0022]
Although the present invention has been described using an AT-cut crystal resonator element (quartz substrate), the present invention is not limited to the AT-cut, and cut angles such as BT-cut, CT-cut, DT-cut, SC-cut, and GT-cut are used. Needless to say, it can be applied to a quartz substrate.
[0023]
Needless to say, the present invention is not limited to a quartz resonator element (quartz substrate), and can be applied to a piezoelectric resonator element such as langasite, lithium tetragonal acid, lithium tantalate, lithium niobate, or the like.
[0024]
【The invention's effect】
According to the present invention, it is possible to obtain a method of manufacturing a piezoelectric vibration element that can cope with downsizing (thinning) and improve the yield.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a crystal resonator element according to an embodiment of the invention.
(A) Top view.
(B) Side view.
FIG. 2 is a configuration diagram of a large crystal substrate according to an embodiment of the present invention.
(A) Top view.
(B) AA longitudinal cross-sectional view.
FIG. 3 is an explanatory view of a protective film forming step according to the manufacturing method of the present invention.
FIG. 4 is an explanatory view of a first crystal etching process according to the manufacturing method of the present invention.
FIG. 5 is an explanatory diagram of a first photoresist stripping process according to the manufacturing method of the present invention.
FIG. 6 is an explanatory diagram of a first mask pattern etching process according to the manufacturing method of the present invention.
FIG. 7 is an explanatory diagram of a second crystal etching process according to the manufacturing method of the present invention.
FIG. 8 is an explanatory diagram of a second photoresist stripping process according to the manufacturing method of the present invention.
FIG. 9 is an explanatory diagram of a second mask pattern etching process according to the manufacturing method of the present invention.
FIG. 10 is an explanatory diagram of a third crystal etching process according to the manufacturing method of the present invention.
FIG. 11 is an explanatory diagram of a third photoresist stripping process according to the manufacturing method of the present invention.
FIG. 12 is an explanatory diagram of a third mask pattern etching process according to the manufacturing method of the present invention.
FIG. 13 is an explanatory diagram of a deposition mask mounting process according to the manufacturing method of the present invention.
FIG. 14 is an explanatory diagram of an electrode forming process according to the manufacturing method of the present invention.
FIG. 15 is an explanatory diagram of a folding process according to the manufacturing method of the present invention.
(A) Folding mask placement work.
(B) Folding work.
FIG. 16 is a perspective view of a conventional crystal resonator element.
FIG. 17 is a longitudinal sectional view for explaining a conventional electrode forming step.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Quartz substrate 1a ... Vibrating part 1b ... Step part 2 ... Excitation electrode 3 ... Lead electrode 10 ... Quartz vibrating element 21 ... Large crystal substrate 22 ... Connection part 23 ... Frame part 23a ... Protrusion part 24 ... Support part 25 ... Gap 31 ... large crystal substrates 32a to 32d ... mask pattern 33 ... first photoresist 34 ... second photoresist 40 ... large crystal substrate 43 ... metal thin film 45 ... large vapor deposition mask 46 ... magnet 50 ... folding mask 100 ... crystal Vibration element 101 ... Quartz substrate 102 ... Excitation electrode 103 ... Extraction electrode 104 ... Non-formed part 111 ... Inner plate 112 ... Upper plate 113 ... Lower plate 114 ... Frame plate

Claims (4)

A method for manufacturing a piezoelectric vibration element in which the thickness of the central portion is made larger than the peripheral edge of the piezoelectric substrate and the thick portion is used as a vibration portion,
An element region corresponding to the piezoelectric vibration element of a large-sized piezoelectric substrate, a support region disposed with the element region separated from the first gap, and a frame portion disposed with the support region separated from the second gap A first etching step of covering the region with a protective film and etching the gap of the piezoelectric substrate;
A second etching step of covering the vibration area corresponding to the vibration section, the support section area and the frame section area with a protective film, and etching the piezoelectric substrate;
Have
After the first and second etching steps pass through the first gap leaving a narrow connecting portion connecting the element region and the supporting portion region, the connecting portion is broken to divide the piece. A method of manufacturing a piezoelectric vibration element, comprising obtaining a piezoelectric vibration element. A third etching step of covering one surface of the frame region with a protective film and etching the piezoelectric substrate;
Attaching the electrode mask to the piezoelectric substrate using the frame region covered with the protective film in the third etching step as a reference for alignment;
A film forming step of forming an electrode film through an electrode mask;
The method for manufacturing a piezoelectric vibration element according to claim 1, comprising: Using a metal film as the protective film, leaving the metal film as a main electrode in the vibration region, and removing other metal films;
Forming a lead electrode extending from the main electrode to the end of the element region by vapor deposition or sputtering using a lead electrode mask;
The method for manufacturing a piezoelectric vibration element according to claim 1, comprising: A folding mask having an opening in the element region is attached to a piezoelectric substrate so that an opening end is located at a connection portion between the element region and the connecting portion, and the connecting portion is folded. The method for manufacturing a piezoelectric vibration element according to claim 1.

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