JP2006203700A - Piezoelectric substrate manufacturing method, piezoelectric vibration element, piezoelectric vibrator, and piezoelectric oscillator - Google Patents

Abstract

[PROBLEMS] To solve the problem of variation in characteristics caused by burrs or defects on the cut surface of a diaphragm during batch processing.
SOLUTION: By providing a thin diaphragm 4 and a thick reinforcing portion 5 that integrally surrounds at least a part of the outer peripheral edge of the diaphragm, a concave portion 3 is provided on at least one main surface side. A method of manufacturing a piezoelectric substrate 2 having a formed configuration, the basic shape processing step of a piezoelectric substrate base material for manufacturing a piezoelectric substrate base material in which a plurality of piezoelectric substrates are connected in a sheet shape, and formation of a recessed portion of the piezoelectric substrate base material A masking process for masking the surface side and masking the back surface of the piezoelectric substrate base material on the surface excluding the elongated non-mask region provided along the boundary line of each piezoelectric substrate region, and the piezoelectric in the non-mask region Etching process to remove the substrate part by etching to form a through slit, mask removing process to remove the mask formed on both sides of the piezoelectric substrate base material, and a dividing process to divide the piezoelectric substrate into pieces along the through slit It consists of about.
[Selection] Figure 1

Description

  The present invention relates to a method for manufacturing a piezoelectric substrate having a structure in which at least a part of an ultrathin diaphragm is integrally surrounded and supported by a thick reinforcing portion, and a conductive pattern such as an excitation electrode on the piezoelectric substrate manufactured by the manufacturing method. In particular, a piezoelectric vibrator in which the piezoelectric vibrator is hermetically sealed in a package, and further improvement of a piezoelectric oscillator using the piezoelectric vibrator, especially for outputting a resonance frequency of 50 MHz or more. When a piezoelectric substrate having an ultra-thin diaphragm is formed by batch processing by forming a plurality of concave portions by etching a piezoelectric wafer having an area, the conventional work for separating the piezoelectric substrate base material into individual pieces is performed. The present invention relates to a technology that can solve a problem that has occurred due to mechanical cutting.

A surface-mount type piezoelectric device having a structure in which a piezoelectric vibration element is hermetically sealed in a package, such as a crystal resonator, is used as a reference frequency generation source in communication devices such as mobile phones and pagers, and electronic devices such as computers. Although used as a filter or the like, the piezoelectric devices are also required to be miniaturized in response to the miniaturization of these various devices.
In addition, a piezoelectric oscillator as a surface-mounting piezoelectric device has a recess in a state where a piezoelectric vibration element and a circuit component constituting an oscillation circuit are housed in a recess formed on an upper surface of a package body made of, for example, ceramic. The opening is sealed with a metal lid.
Conventionally, as a piezoelectric vibration element used in the piezoelectric device as described above, a concave portion is formed by excavating a part of one surface of a piezoelectric substrate so as to cope with a higher frequency of a fundamental wave frequency of 50 MHz or more. The bottom surface is an ultra-thin diaphragm with a thickness of about a dozen μm, and the piezoelectric substrate has a structure in which the periphery of the diaphragm is integrally surrounded by a thick reinforcing portion, and an input formed on both sides of the diaphragm. A piezoelectric vibration element including an output electrode and a ground electrode is known (Japanese Patent Laid-Open No. 9-55635).
In JP-A-2002-33640, two sides of a rectangular ultrathin diaphragm are supported by an L-shaped thick part, and the other two sides are not supported by a thick part and are free. Thus, there is disclosed a piezoelectric vibration element in which a chip is miniaturized. When mass-producing such a piezoelectric vibration element by batch processing using a large-area piezoelectric substrate base material, after performing a processing step of forming a recessed portion on each piezoelectric substrate piece by etching, In the final cutting process, it is necessary to mechanically cut an ultrathin diaphragm having a thickness of several tens of μm with a dicing saw. However, there is a possibility that burrs and defects are likely to occur at the cut portion along with this cutting work, and the sharpness of the cut surface is impaired and roughened, which may cause variations in characteristics.
Japanese Patent Laid-Open No. 9-55635 JP 2002-33640 A

  The present invention has been made in view of the above, and manufactures a piezoelectric substrate including an ultrathin diaphragm capable of outputting a resonance frequency of 50 MHz or more and a thick portion supporting at least a part of the diaphragm. In the case of performing batch processing in which the individual region on the piezoelectric substrate base material is processed into a predetermined shape by etching or the like and then cut along the peripheral portion of the diaphragm of the piezoelectric substrate piece, A method of manufacturing a piezoelectric substrate, a piezoelectric vibration element, a piezoelectric vibrator, and a piezoelectric oscillator that can eliminate the problem of variation in characteristics caused by burrs or defects on the cut surface or roughening the surface. The purpose is to provide.

In order to solve the above-described problem, the thin diaphragm according to claim 1 and a thick reinforcing part integrated with the outer peripheral edge of the diaphragm are provided, so that a recess is formed on at least one main surface side. A method of manufacturing a piezoelectric substrate having a formed configuration, the basic shape processing step of a piezoelectric substrate base material for manufacturing a piezoelectric substrate base material in which a plurality of piezoelectric substrates are connected in a sheet shape, and the recessed portion of the piezoelectric substrate base material A masking step of masking the formation surface side, and masking the back surface of the piezoelectric substrate base material on a surface excluding the elongated non-mask region provided along the boundary line of each piezoelectric substrate region; An etching step of removing a piezoelectric substrate portion in a non-mask region on the back surface of the material by etching to form a through slit; a mask removing step of removing the mask formed on both sides of the piezoelectric substrate base material; Characterized in that it consists of a dividing step of dividing the piezoelectric substrate pieces, along Tsu bets.
According to a second aspect of the present invention, in the first aspect, the basic shape processing step of the piezoelectric substrate base material includes a metal mask forming step of covering both front and back surfaces of the piezoelectric substrate base material with a metal mask, and a surface of the piezoelectric substrate base material. A pattern forming step of forming a recess portion forming pattern of the piezoelectric substrate pieces and an outer shape pattern along a boundary line between the piezoelectric substrate pieces using a resist film formed in a predetermined pattern on the side metal mask; An exposed piezoelectric substrate using a metal mask removing process for removing the metal mask exposed from the resist film, a resist film removing process for removing the resist film, and a metal mask pattern remaining after removing the resist film By etching the surface of the base material, the concave portions of the piezoelectric substrate pieces and the piezoelectric substrate base material surface corresponding to the boundary line between the piezoelectric substrate pieces are dug to the required depth. A recessing process for forming a thin portion on the bottom surface of each recess, a metal mask removing process for removing the metal mask remaining on both the front and back surfaces of the base material of the piezoelectric substrate, and an inner bottom surface of the recess portion of each piezoelectric substrate piece And a frequency fine adjustment step of finely adjusting the resonance frequency of the diaphragm located at the position.
A piezoelectric vibration element according to a third aspect of the invention is manufactured by the manufacturing method according to any one of the first and second aspects, and on both the front and back surfaces of the vibration plate of the piezoelectric substrate. It is characterized by comprising excitation electrodes formed respectively and lead electrodes drawn out from the respective excitation electrodes to the reinforcing portion of the piezoelectric substrate.
According to a fourth aspect of the present invention, a piezoelectric vibrator includes the piezoelectric vibration element according to the third aspect and a package in which the piezoelectric vibration element is hermetically sealed.
A piezoelectric oscillator according to a fifth aspect of the invention includes the piezoelectric vibration element according to the third aspect, or the piezoelectric vibrator according to the fourth aspect, and an oscillation circuit.

  According to the present invention, since the piezoelectric substrate piece is separated from the piezoelectric substrate base material by etching using a photolithography technique, burrs and defects are not formed on the substrate end surface, and the edge of the diaphragm is formed sharply. it can. In addition, since the outer dimensions of the chip can be formed with high accuracy by the photolithography technique, variation in characteristics can be suppressed. Further, according to the photolithography technique, it is possible to manufacture a quartz substrate having a shape that is difficult to achieve by mechanical cutting.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
FIG. 1A is a perspective view of a concave portion side of a crystal resonator element 1 made of an AT cut crystal as an example of a piezoelectric resonator element according to an embodiment of the present invention.
The quartz crystal vibration element (piezoelectric vibration element) 1 includes a thin vibration plate 4 and a thick portion 5 that integrally supports at least a part of the outer peripheral edge of the vibration plate 4 (three sides of the rectangular vibration plate in this example). The quartz substrate (piezoelectric substrate) 2 having a configuration in which the concave portion 3 is formed on at least one main surface side, excitation electrodes 10a and 10b formed on the quartz substrate 2, lead electrodes 11a and 11b, It has.
More specifically, the crystal resonator element 1 includes a crystal substrate 2 made of an AT-cut crystal as a piezoelectric crystal material having thickness-shear vibration characteristics, and excitation electrodes 10a and 10b formed on both main surfaces of the crystal substrate 2, respectively. And lead electrodes 11a and 11b extending from the excitation electrodes 10a and 10b, respectively, and connection pads 12a and 12b at the end portions of the lead electrodes. Each electrode and pad is a conductor film formed on the piezoelectric substrate by vapor deposition using a mask, sputtering, or the like so as to obtain a predetermined shape.

The quartz crystal substrate 2 according to this embodiment has a rectangular flat plate-like substrate body that is long in, for example, the x-axis direction among the biaxial directions x and z ′ (axis rotated at 35 ° 15 ′ with respect to the crystal axis z). The concave portion 3 is formed by etching on one main surface of the main surfaces with the y ′ axis (axis rotated by 35 ° 15 ′ with respect to the crystal axis y) as a normal line. The ultrathin diaphragm 4 is positioned on the inner bottom surface, the three sides of the outer peripheral edge of the diaphragm 4 are integrally held by the thick portion 5, and one side of the diaphragm 4 is thick. This is a structure in which the outer peripheral portion is etched and dug out so that the recessed portion 3 is opened without any portion. The illustrated quartz substrate is merely an example, and the side where the electrode pads 12a and 12b of the diaphragm are located and the side adjacent to the side (two in total) as in the quartz substrate disclosed in JP-A-2002-33640. A configuration in which only the L-shaped side consisting of the sides) is supported by the thick portion may be applied by the die cutting by etching as in the present embodiment.
When the diaphragm 4 of the crystal resonator element 1 outputs a resonance frequency of 50 MHz, for example, the thickness of the diaphragm 4 is about several tens of μm.
FIG. 1B shows a quartz substrate base material in a state (before division) in which a large number of quartz substrates are connected vertically and horizontally. In the method of the present invention, the crystal substrate pieces shown by hatching are elongated and penetrated by etching so that the pieces are obtained. Conventionally, cutting was performed with a dicing saw along the boundary line between the individual pieces, so when cutting to remove the thick portion from one end edge of the diaphragm 4, burrs were slightly generated on the cut surface of the diaphragm. However, the sharpness of the cut surface is impaired and the surface is roughened, causing variations in characteristics. However, the present invention is characterized in that mechanical cutting is not performed.

Hereinafter, a method for mass-producing a quartz crystal substrate (piezoelectric substrate) 2 according to an embodiment of the present invention without changing characteristics by separating a quartz substrate matrix (piezoelectric substrate matrix) 20 having a large area by etching will be described. To do.
2A to 2J are views showing an example of the manufacturing process of the quartz crystal substrate (piezoelectric substrate) of the present invention.
In this method of manufacturing a quartz substrate, a plurality of concave portions 3 are formed on a single quartz wafer, and a basic shape of a quartz substrate base material 20 in which a plurality of quartz substrates 2 are connected in a sheet shape is manufactured. The basic shape processing steps (a) to (g) and the metal mask 50 are applied to the recessed portion forming surface (front surface) side of the crystal substrate base material 20 on which the basic shape has been formed. A masking step (h) for applying a metal mask 50 to the surface excluding the elongated non-mask region 51 provided along the boundary line of the region of each crystal substrate 2, and the crystal in the non-mask region 51 on the back surface of the crystal substrate base material An etching process (i) for removing the substrate portion by etching to form the through slit 21; a mask removing process (i) for removing the metal mask 50 formed on the front and back surfaces of the quartz substrate base material; Each water that composes A metal pattern formation (electrode film formation) step (j) in which the excitation electrodes 10a and 10b, the lead electrodes 11a and 11b, and the connection pads 12a and 12b are formed by vapor deposition or sputtering on the substrate piece, and along the through slit And a dividing step (not shown) for dividing the crystal line into individual quartz substrate pieces.
In the present embodiment, the through slits are formed by etching along the boundary lines between the individual quartz substrates 2 constituting the quartz substrate base material 20, thereby separating the individual pieces without using cutting means. Is possible.

Next, the basic shape processing step of the quartz substrate base material will be described.
In the basic shape processing step of the quartz substrate base material, first, a metal mask forming step (a) for covering the front and back surfaces of the quartz substrate base material 20 in a wafer state with the metal mask 30 is performed. In this example, a laminated body in which a chromium Cr layer and a gold Au layer are sequentially formed by vapor deposition is used as the metal mask 30.
Next, a metal mask of a portion for forming a recess portion forming pattern of the crystal substrate piece on the surface side of the crystal substrate base material 20 and an outer shape pattern along a boundary line between the pieces of the crystal substrate 2 using the photolithography technique The pattern formation process (b) which removes 30 is implemented. In this process, the photoresist film 31 is uniformly coated on the entire surface of the metal mask 30 on the surface side, and then the portions other than the above-described desired pattern are covered with an exposure mask (not shown) (when the photoresist is a positive type). Thereafter, the exposed photoresist portion is removed to remove the exposed photoresist portion, and the outer pattern portion (recess 36 to be described later) along the boundary line between the recessed portion forming portion (a portion to be a thin portion 35 described later) and the quartz substrate piece. The metal mask 30 is exposed. Next, a metal mask removing process for removing the exposed surface-side metal mask 30 by etching is performed to obtain the state shown in FIG.
Next, a resist film removing step for removing the remaining unexposed resist film 31 is performed.

Next, by using the surface-side metal mask pattern 30a remaining after removing the resist film 31, the surface of the crystal substrate base material 20 exposed in the opening of the surface-side metal mask pattern 30a is etched, so A concave portion of each piece and a quartz substrate base material surface portion corresponding to a boundary line between each quartz substrate piece are dug down to a required depth to form concave portions 35 and 36 communicating with each other, and a thin portion is formed on the bottom surface of each concave portion A drilling step (c) for forming 35a and 36a is performed. The right view of FIG. 2C is a plan view, and a wall portion 37 that becomes the thick portion 5 is formed between the recesses 35 and 36.
In the subsequent metal mask peeling step (d), the surface-side metal mask pattern 30a remaining on the front surface side and the metal mask 30 on the back surface side are removed.
Thereafter, frequency fine adjustment steps (e), (f), and (g) for finely adjusting the resonance frequency of the thin portion (diaphragm) 35a located on the inner bottom surface of the recessed portion 35 of each quartz substrate piece are performed. In this frequency fine adjustment step, first, in the frequency measurement step (e), the thin portion 35a (corresponding to the diaphragm 4) formed in the step (d) is formed thicker than the target value, and the thin portion 35a By measuring the resonance frequency by bringing the probe of the frequency measuring device into contact with each other, it is determined how thick each thin portion 35a is than the target value.
In the subsequent fine etching step (f), the etching guide 39 is stacked on the outer wall 38 surrounding the recesses 35 and 36 to form a dam, and the etching guide 39 is filled with an etching solution in the state where each dam is formed. When the time required for the thin portions 35a and 36a to reach the target value has elapsed, the etching solution is washed and the etching guide 39 is removed.
Thereafter, in step (g), the final resonance frequency is confirmed using a frequency measuring device, thereby completing the basic shape processing step of the quartz substrate base material. At this time, the thin portion 35 a becomes the diaphragm 4. The thin portion 36a is utilized as a region for forming the through slit 21 in an etching step (i) described later.

In the masking step (h) following the basic shape processing step of the quartz substrate base material, the concave portion forming surface (front surface side and back surface side) of the quartz substrate base material 20 on which the basic shape has been formed is entirely covered by the metal mask 50. After the coating, the back surface of the quartz substrate base material 20 is stripped by removing the metal mask 50 so that the quartz surface of the portion along the boundary line (recess 36) of each quartz substrate region is exposed by photolithography. A non-mask region 51 is formed. The metal mask 50 is a laminated body in which a chromium Cr layer and a gold Au layer are sequentially formed by vapor deposition, and the metal mask 50 is also applied to a position to be a connecting portion described later.
In the subsequent etching step (i), in the state where the metal mask 50 is applied by the masking step (h), the quartz substrate portion in the non-mask region 51 on the back surface of the quartz substrate base material is removed by etching, and the through slit 21 is formed. Form.
After the through slit 21 is formed, the metal mask 50 on both the front and back surfaces is removed.
Subsequently, in the metal pattern forming step (j), the excitation electrodes 10a and 10b, the lead electrodes 11a and 11b, and the connection pads 12a and 12b are respectively masked on the front and back surfaces of each quartz substrate piece so as to obtain a predetermined electrode shape. It is formed by vapor deposition using sputtering and sputtering.
At the stage where the basic shape processing process of the quartz substrate base material is completed, the thickness adjustment (frequency adjustment) of the diaphragm 4 of each crystal substrate piece constituting the quartz substrate base material 20 is completed. Yes.
Finally, the quartz substrate 2 can be obtained by carrying out a dividing step of dividing the quartz substrate into pieces from the line along the through slit 21.

The through-slit 21 of this embodiment consists of two parts, a U-shaped part and a linear part, so that the quartz crystal substrate 2 does not fall off before the dividing step, and both parts are separated from each other. In the state in which the slit is formed, the quartz substrate piece located inside the through slit is still connected to the base material. Therefore, what is necessary is just to divide from the connection part between each through slit in order to isolate | separate completely.
By completing the etching so as to surround each piece by such a discontinuous through slit, the state in which the pieces are connected to each other may be maintained at the time when the etching is completed, or continuous. The etching may be performed so that the individual pieces are surrounded by the annular through slit so that all the individual pieces are separated at the end of the etching.
In the above embodiment, the method of separating the quartz substrate of the type in which at least one side of the diaphragm is not supported by the thick portion from the quartz substrate base material by etching is described. In the case of separating the quartz substrate of the type surrounded by the base material from the base material, it can be separated by forming the through slit as described above along the boundary line of the quartz substrate.
Thus, according to the present invention, since the individual pieces are separated from the base material by etching, burrs and defects are not formed on the end face of the substrate, and the edge of the diaphragm can be formed sharply. In addition, since the outer dimensions of the chip can be formed with high accuracy by the photolithography technique, variation in characteristics can be suppressed. Further, according to the photolithography technique, it is possible to manufacture a quartz substrate having a shape that is difficult to achieve by mechanical cutting.

Next, FIG. 3 is a cross-sectional view of a crystal resonator (piezoelectric vibration element) as a surface-mount piezoelectric device using the crystal vibration element (piezoelectric vibration element) 1 according to each of the above embodiments. Has a configuration in which the crystal resonator element 1 is hermetically sealed in the package 61. The package 61 is sealed with a metal lid 66 in a state where the crystal resonator element 1 is mounted in the recess of the container body 62 made of an insulating material. A connection pad 63 is provided on the inner bottom surface of the recess of the container body 62, and an external electrode 64 is provided on the outer bottom surface. The connection pads 12 a and 12 b are fixed on the connection pad 63 using a conductive adhesive 65.
FIG. 4 is a cross-sectional view of a crystal oscillator (piezoelectric oscillator) as a surface-mount type piezoelectric device using the crystal resonator element (piezoelectric resonator element) 1 according to each of the above embodiments. The quartz resonator element 1 and a circuit component 72 constituting an oscillation circuit and the like are accommodated therein.
In the above embodiment, quartz is exemplified as the piezoelectric crystal material. However, this is only an example, and the present invention can be applied to a quartz crystal vibration element made of any piezoelectric crystal material.

(A) is a concave side perspective view of a quartz resonator element made of an AT-cut quartz crystal as an example of a piezoelectric resonator element according to an embodiment of the present invention, and (b) is a configuration explanatory view of a quartz wafer. (A) thru | or (j) is a figure which shows an example of the manufacturing process of the quartz substrate (piezoelectric substrate) of this invention. Sectional drawing of the crystal oscillator (piezoelectric vibration element) as a surface mount-type piezoelectric device using the crystal vibration element (piezoelectric vibration element) which concerns on each embodiment. Sectional drawing of the crystal oscillator (piezoelectric oscillator) as a surface mount-type piezoelectric device using the crystal oscillator (piezoelectric oscillator) which concerns on each embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Quartz vibration element (piezoelectric vibration element), 2 Quartz substrate (piezoelectric board | substrate), 3 Recessed part, 4 Vibration plate, 5 Thick part, 10a, 10b Excitation electrode, 11a, 11b Lead electrode, 12a, 12b Connection pad, 20 Quartz substrate base material (piezoelectric substrate base material), 21 through slit (through hole) 30 metal mask, 31 photoresist film, 35, 36 recess, 35a, 36a thin part, 38 outer wall, 39 etching guide, 50 metal mask, 51 Non-mask area, 60 Crystal oscillator (piezoelectric oscillator), 61 package, 62 Container body, 63 Connection pad, 64 External electrode, 65 Conductive adhesive, 70 Crystal oscillator (piezoelectric oscillator), 71 package, 72 Circuit parts .

Claims (5)

A method of manufacturing a piezoelectric substrate having a configuration in which a concave portion is formed on at least one main surface side by providing a thin diaphragm and a thick reinforcing portion integrated with an outer peripheral edge of the diaphragm. ,
A basic shape processing step of a piezoelectric substrate base material for manufacturing a piezoelectric substrate base material in which a plurality of piezoelectric substrates are connected in a sheet shape;
A mask is formed on the surface of the piezoelectric substrate base material except the elongated non-mask region provided along the boundary line of each piezoelectric substrate region. Masking process to be applied;
An etching step of removing the piezoelectric substrate portion in the non-mask region on the back surface of the piezoelectric substrate base material by etching to form a through slit;
A mask removing step of removing the mask formed on both sides of the piezoelectric substrate base material;
And a dividing step of dividing the piezoelectric substrate into pieces along the through slit. The basic shape processing step of the piezoelectric substrate base material is:
A metal mask forming step of covering both front and back surfaces of the piezoelectric substrate base material with a metal mask;
Using a resist film formed in a predetermined pattern on a metal mask on the surface side of the piezoelectric substrate base material, a pattern for forming a concave portion of the piezoelectric substrate piece and an outline pattern along the boundary line between the piezoelectric substrate pieces are formed. A pattern forming step to be formed;
A metal mask removing step of removing the metal mask exposed from the resist film;
A resist film removing step for removing the resist film;
Using the metal mask pattern that remains after removing the resist film, the exposed piezoelectric substrate base material surface is etched to correspond to the recesses of the piezoelectric substrate pieces and the boundary lines between the piezoelectric substrate pieces. Digging the piezoelectric substrate base material surface to the required depth to make a recess, and digging process to form a thin portion on the bottom surface of each recess,
A metal mask removing process for removing the metal mask remaining on the front and back surfaces of the piezoelectric substrate base material, respectively;
The method for manufacturing a piezoelectric substrate according to claim 1, further comprising: a frequency fine adjustment step of finely adjusting a resonance frequency of the diaphragm located on the inner bottom surface of the recessed portion of each piezoelectric substrate piece.   A piezoelectric substrate manufactured by the manufacturing method according to claim 1, an excitation electrode formed on each of the front and back surfaces of the diaphragm of the piezoelectric substrate, and a piezoelectric substrate formed from each excitation electrode. A piezoelectric vibration element comprising: a lead electrode drawn out to a reinforcing portion of the substrate.   A piezoelectric vibrator comprising the piezoelectric vibration element according to claim 3 and a package in which the piezoelectric vibration element is hermetically sealed.   A piezoelectric oscillator comprising the piezoelectric vibration element according to claim 3 or the piezoelectric vibrator according to claim 4 and an oscillation circuit.

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