JP5207239B2 - Method of forming crystal piece - Google Patents

Description

  The present invention relates to a crystal piece forming method for forming a crystal piece used in a crystal resonator and a crystal oscillator mounted on an electronic device.

  Conventionally, crystal resonators have been used in electronic devices. For example, a crystal piece in which an electrode is formed in a predetermined container is hermetically sealed and protected, and a terminal that is partially exposed to the outside of the container is connected to the electrode formed on the crystal piece through a wiring. This terminal can be connected to the outside. There are various shapes of crystal pieces used for such crystal elements (crystal elements). For example, plate-shaped crystal pieces such as a rectangular shape and a circular shape in plan view, and tuning-fork type crystal pieces are known.

  Such a quartz piece is formed, for example, by processing a quartz substrate having a side of about 100 mm. In this processing, a desired shape (for example, the shape of a tuning fork) is formed in a plurality of chip areas on a quartz substrate, and thereafter, each chip area is cut out (cut) to simultaneously form a plurality of crystal pieces. ing. In the above-described shape formation, the shape is formed by wet etching using a mask pattern formed by a well-known photolithography technique (see Patent Document 1).

  However, quartz is widely known as a material having an etching anisotropy having a different etching rate for each crystal axis, and this becomes a problem in the production of a crystal resonator. In the etching process described above, the etching progresses in the thickness direction of the quartz substrate according to the shape of the mask pattern. At this time, due to the anisotropy of the quartz crystal, the etching does not proceed perpendicular to the substrate plane, but proceeds in an oblique direction in cross section. For this reason, even if etching is completed in the thickness direction, a portion (etching residue) protruding from the mask pattern in a plan view is formed. In addition, since the etching progress direction differs depending on the direction of the crystal substrate plane (crystal direction), the above-described remaining etching state varies depending on the position of the edge of the crystal piece.

  Even after the etching in the thickness direction is completed, the etching residue can be reduced by further etching (over etching). However, by performing over-etching, an undercut phenomenon in which etching proceeds also under the mask pattern occurs. Although the etching residue of the portion protruding from the mask pattern in plan view decreases with the overetching time, the undercut increases accordingly.

  Since the etching residue affects the size of the crystal resonator to be formed, it is desirable to make it as small as possible. For example, the main factor that determines the frequency of a tuning fork type crystal resonator is the width of the legs that make up the tuning fork. Although the etching residue can be reduced by increasing the etching time of the crystal, as described above, the state of the etching residue varies depending on the location, and in addition, undercuts occur with the etching time, so it is easy to control the dimensions. is not. In particular, for a smaller tuning fork type crystal resonator, the influence of the dimensional error on the frequency becomes large, which becomes a problem that cannot be ignored.

  In order to prevent the above-described anisotropic etching due to wet etching, there is a technique for processing a crystal by a dry etching technique in which etching is performed with plasma or gas to manufacture a crystal resonator. However, in dry etching, when a resist pattern made of an organic material is used as a mask, the etching selection ratio between the resist and crystal cannot be increased, and the processable dimensions are limited. For this reason, when manufacturing a crystal resonator by processing crystal by dry etching, first, a metal film is formed on a crystal wafer, and this metal film is etched with a resist mask formed by a photolithography technique to form a metal mask. The crystal is processed using this metal mask.

  However, in dry etching, a processing container (vacuum container) that can obtain a predetermined reduced pressure environment is required, and in order to perform etching, first, the inside of the processing container is evacuated under reduced pressure, which requires more time for processing. There is a problem.

  In the processing by dry etching, the problem of etching anisotropy in the wet etching described above does not occur, but the use of the mask pattern is the same, and the point that the mask pattern is formed by over-etching is the same. It is. For this reason, the time management of the etching process is important.

JP 2007-150923 A

  As described above, in wet etching, dimensional control is not easy due to etching residue due to crystal anisotropy. In addition, by processing the crystal by dry etching, problems such as anisotropy and etching residue in wet etching can be solved, but more time is required, and dimensional control is not easy. It becomes. In any case, it is based on lithography technology and requires many complicated processes including the formation of a mask pattern that does not remain as a product, and there is a common problem that time efficiency for processing is low and wasteful. is there

  On the other hand, there is no need for processes such as mask pattern formation and removal, and techniques for forming in a shorter time include punching and cutting. However, the punching process cannot be applied in the formation of the quartz piece, and the production of a finely shaped quartz piece is not easy in the cutting process. As described above, there is a problem that it is not easy to form a crystal piece by processing a crystal substrate (wafer).

  The present invention has been made to solve the above-described problems, and an object of the present invention is to make it possible to form a crystal piece having a desired shape more easily.

Forming method of the crystal element according to the present invention, the pulse width in the range of 10 ^-10 to 10 ^-12 second, also, 1 .mu.J 266 nm, 355 nm, 532 nm, and 1064nm pulse energy at a selected oscillation wavelength from among picosecond laser beam range with ～300MyuJ, along the shape of the quartz piece on the desired machining speed to form a cut groove by irradiating the quartz substrate at 0.5 mm / sec, to form a cutting groove after a method to so that to obtain a crystal element by cutting a quartz substrate by taking folded along the cutting groove.

In the method of forming a quartz piece, the picosecond laser beam is irradiated from the normal direction of the plane of the quartz substrate.

According to the present invention, the pulse width ranges from 10 ⁻¹⁰ to 10 ⁻¹² seconds, and the pulse energy ranges from 1 μJ to 300 μJ at an oscillation wavelength selected from 266 nm, 355 nm, 532 nm, and 1064 nm. picosecond laser beam, along the shape of the crystal piece to the desired, since the machining speed so as to irradiate the quartz substrate at 0.5 mm / sec, more easily so that the crystal piece of the desired shape can be formed An excellent effect is obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1A to 1F are process diagrams and explanatory views for explaining a method of forming a crystal piece according to an embodiment of the present invention. First, as shown in FIG. 1A, for example, a quartz substrate 101 having a plate thickness of 0.03 to 0.10 mm is prepared, and a virtual cutting line 111 is formed on one surface (main surface) of the quartz substrate 101. The laser beam is irradiated (scanned). The cutting line 111 has a shape of a crystal piece to be formed, for example, a tuning fork type crystal resonator.

  For example, by using the laser processing apparatus illustrated in the perspective view of FIG. The laser beam 205 condensed in (1) is irradiated from the normal direction of the crystal substrate 101 plane. The laser oscillation unit 202 is composed of, for example, a YAG laser.

  The scanning with the laser beam 205 may be performed, for example, by moving the stage 201 on which the crystal substrate 101 is placed (fixed) within the plane of the stage 201 by the stage driving system 208. In this case, the locus of movement of the stage 201 becomes a virtual cutting line 111.

Here, the laser beam is a pulsed laser beam having a wavelength of 1064 nm (picosecond laser) with a pulse width and a pulse interval of 15 pico (10 ⁻¹² ) seconds, and this picosecond laser is processed at a processing speed of 0.5 mm / second. The quartz substrate 101 is irradiated while being moved relatively. Here, in the above-described embodiment, the stage 201 is moved relatively, but the present invention is not limited to this. For example, the relative movement may be realized by moving the condensing optical system 204. Alternatively, relative movement may be realized by scanning the laser beam 205 using a movable mirror.

The pulse interval may be in the range of 10 ⁻¹⁰ to 10 ⁻¹⁵ seconds. As the pulse interval in this range, the pulse energy may be in the range of 1 μJ to 300 μJ. This pulse energy is a value obtained by dividing the average frequency of the laser by the repetition frequency. It has been confirmed that when the wavelength (source oscillation) of the laser used is larger than 1064 nm, chipping or other chipping occurs on the cut surface (side) of the crystal piece to be formed. Accordingly, the laser wavelength should be 1064 nm or less.

  By irradiating the laser along the cutting line 111 under the above-described conditions, as shown in FIG. 1C, a cutting kerf 112 having a width of about 0.015 mm is formed on the quartz substrate 101, and the frame portion 102, the element portion 103, And the element outside crystal piece 104 is formed. Next, when the out-of-element crystal piece 104 is separated from the crystal substrate 101, the frame portion 102 of the crystal substrate 101 is provided with a plurality of element portions 103 as shown in FIG. 1D.

  Next, as shown in FIG. 1E, a laser beam is irradiated (scanned) along a virtual cutting line 113 for separating each element portion 103 and the frame portion 102, and as shown in FIG. 114 is formed. For example, as the groove is formed deeper, by gradually increasing the number of pulses and irradiating with a laser beam, the cut groove 114 having a step-like cross-sectional oblique shape when viewed microscopically can be formed.

  After the cutting groove 114 is formed as described above, the tuning fork crystal piece 131 is obtained as shown in FIGS. 2A and 2B by breaking each element portion 103 along the cutting groove 114. The crystal piece 131 includes a base portion 132 and two leg portions 133. In the present embodiment, the cut surface 134 formed by laser processing is formed at an angle larger than 90 ° with respect to the plane of the crystal piece 131.

  In the present embodiment described above, the quartz substrate is cut by laser beam irradiation to form a quartz piece, so that it is not necessary to form a mask pattern or the like, and there are etching residues and dimensional errors due to etching. Does not occur. Thus, according to the present embodiment, it is possible to form a crystal piece having a desired shape more easily than the formation of a crystal piece by etching.

As described above, when a laser beam is irradiated onto the quartz substrate with a pulse width in the range of 10 ⁻¹⁰ to 10 ⁻¹⁵ seconds, a large number of condensed photons are collected at the condensing point of the laser beam transmitted through the quartz. It is known to interact with crystals and become absorbed. This phenomenon is called multiphoton absorption. Here, when the pulse width is longer than picoseconds, a part of the light energy absorbed by the phenomenon of multiphoton absorption is converted to heat, so that the crystal at the spot irradiated with the laser beam is dissolved. It is thought to become. Among them, the pulse width is set in the range of 10 ⁻¹⁰ to 10 ⁻¹⁵ seconds, and the pulse energy is set in the range of 1 μJ to 300 μJ. It is considered that the quartz substrate can be cut without causing the cut surface to be wavy by moving it in a moving manner.

  Note that according to the method for forming a crystal piece in the present embodiment, not only the tuning-fork type crystal piece described above, but also, for example, the notch 332 provided at two corners of four corners as shown in FIG. 3A. It is also possible to form a rectangular crystal piece 331. For example, by providing the notch 332, the electrode can be easily routed to the back surface side. In this case, as shown in FIG. 3B, a cutting kerf 312 is formed on the quartz crystal substrate 301 by scanning laser irradiation, and a cutting groove 314 is formed by scanning laser irradiation with an angle, along the cutting groove 314. Then, the crystal piece 331 can be formed by breaking each element portion 303. The formation of the cutting kerf 312 and the cutting groove 314 by laser irradiation is the same as the formation of the cutting kerf 112 and the cutting groove 114 described above.

  Further, according to the forming method of the present embodiment, it is also easy to form a rectangular crystal piece 401 as shown in FIG. 4 and a rectangular crystal piece 501 whose four corners are chamfered as shown in FIG. . Of course, a crystal piece having a circular shape in plan view can be formed in the same manner. In addition, as shown in FIGS. 6A and 6B, a crystal piece 601 including a bevel portion 602 can be formed. Similar to the formation of the cutting groove described above, for example, as the groove is formed deeper, by gradually increasing the number of pulses and irradiating the laser beam, when viewed microscopically, a stepwise cross-sectional oblique shape It is possible to form the bevel portion 602.

It is process drawing for demonstrating the formation method of the crystal piece in embodiment of this invention. It is explanatory drawing for demonstrating the formation method of the crystal piece in embodiment of this invention. It is process drawing for demonstrating the formation method of the crystal piece in embodiment of this invention. It is process drawing for demonstrating the formation method of the crystal piece in embodiment of this invention. It is process drawing for demonstrating the formation method of the crystal piece in embodiment of this invention. It is process drawing for demonstrating the formation method of the crystal piece in embodiment of this invention. It is a top view which shows the structure of the tuning fork type crystal piece produced by the formation method of the crystal piece in embodiment of this invention. It is sectional drawing which shows the structure of the tuning fork type crystal piece produced by the formation method of the crystal piece in embodiment of this invention. It is a top view which shows the structure of the other crystal piece produced by the formation method of the crystal piece in embodiment of this invention. It is explanatory drawing explaining the formation method of the other crystal piece in embodiment of this invention. It is a top view which shows the structure of the crystal piece produced by the formation method of the crystal piece in embodiment of this invention. It is a top view which shows the structure of the crystal piece produced by the formation method of the crystal piece in embodiment of this invention. It is a top view which shows the structure of the crystal piece produced by the formation method of the crystal piece in embodiment of this invention. It is sectional drawing which shows the structure of the crystal piece produced by the formation method of the crystal piece in embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 ... Quartz substrate, 102 ... Frame part, 103 ... Element part, 104 ... Outer element crystal piece, 111 ... Cutting line, 112 ... Cutting kerf, 113 ... Cutting line, 114 ... Cutting groove.

Claims (2)

A picosecond laser beam having a pulse width in a range of 10 ⁻¹⁰ to 10 ⁻¹² seconds and a pulse energy of 1 μJ to 300 μJ at an oscillation wavelength selected from 266 nm, 355 nm, 532 nm, and 1064 nm, along the shape of the crystal piece to the desired, by irradiating the quartz substrate at a machining speed of 0.5 mm / sec to form a cut groove, after forming the cutting grooves, take folding along the cutting groove A method of forming a crystal piece, comprising: cutting the crystal substrate to obtain the crystal piece. In the formation method of the crystal piece of Claim 1,
The method for forming a quartz piece, wherein the picosecond laser beam is irradiated from a normal direction of a plane of the quartz substrate.

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