JP2013063455A - Laser machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser machining method capable of cutting a workpiece formed by crystalline quartz with good dimensional accuracy.SOLUTION: The modified region 7 including a plurality of modified spots S is formed in the workpiece 1 along a planned cutting line 5 by focusing a laser beam L onto the workpiece 1. At that time, the workpiece 1 and the laser beam L are relatively moved along the planned cutting line 5 while irradiating the workpiece 1 with the laser beam L, and two or more modified spots S1 positioning inside the workpiece 1 are formed along the planned cutting line 5. Further, the workpiece 1 and the laser beam L are relatively moved along the line 5 while irradiating the workpiece 1 with the laser beam L, and two or more modified spots S2 exposed to the surface 3 of the workpiece 1 are formed along the line 5 so that any crack exposed to the surface 3 is not formed.

Description

  The present invention relates to a laser processing method for cutting a workpiece.

  As a conventional laser processing method, there is a method of condensing a laser beam on a processing object, forming a modified region along the planned cutting line on the processing target, and cutting the processing target along the planned cutting line. It is known (see, for example, Patent Document 1). In such a laser processing method, a plurality of modified spots are formed along a planned cutting line, and a modified region is formed by the plurality of modified spots.

Japanese Patent Laid-Open No. 2006-108459

  Here, in the laser processing method as described above, when a workpiece to be formed of quartz is cut, for example, since a large crack is likely to occur, the size of the workpiece after cutting is controlled by controlling the crack. It is difficult to control accuracy (processing quality), and it is difficult to improve dimensional accuracy.

  Then, this invention makes it a subject to provide the laser processing method which can cut | disconnect the process target object formed with the quartz crystal with dimensional accuracy.

  In order to solve the above-described problems, a laser processing method according to the present invention is a laser processing method for cutting a processing object formed of crystal along a planned cutting line, and a laser beam is applied to the processing object. A modified region forming step is provided for forming a modified region including a plurality of modified spots on the workpiece along the planned cutting line by collecting light, and the modified region forming step is performed on the workpiece. A process of forming a plurality of first modified spots along the planned cutting line by moving the laser beam relatively along the planned cutting line while irradiating the laser beam; The plurality of second modified spots that are exposed on the laser light incident surface of the workpiece are cut so that cracks that are exposed on the laser light incident surface are not formed. Characterized in that it comprises a step of forming along down.

  When cutting a workpiece to be processed by this laser processing method, a plurality of first modified spots formed inside are easily cut along a planned cutting line and exposed to the laser light incident surface. The second modified spot acts as a so-called cut line, and the cutting is assisted by the plurality of second modified spots. Therefore, it is possible to cut the workpiece with high dimensional accuracy.

  Moreover, it is preferable to further include a cutting step of cutting the processing object using the modified region as a starting point of cutting by applying a force to the processing object from the outside along the scheduled cutting line. Thereby, it becomes possible to cut | disconnect a process target object along a cutting plan line reliably.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to cut | disconnect the processing target object formed with quartz with dimensional accuracy.

It is a schematic block diagram of the laser processing apparatus used for formation of a modification area | region. It is a top view of the processing target object used as the object of formation of a modification field. It is sectional drawing along the III-III line of the workpiece of FIG. It is a top view of the processing target after laser processing. It is sectional drawing along the VV line of the workpiece of FIG. It is sectional drawing along the VI-VI line of the processing target object of FIG. It is a schematic block diagram of the laser processing apparatus which concerns on this embodiment. It is a fragmentary sectional view of the reflection type spatial light modulator of the laser processing apparatus of FIG. It is a schematic block diagram of the other laser processing apparatus which concerns on this embodiment. It is a flowchart which shows the manufacturing process of the crystal oscillator which concerns on this embodiment. It is the schematic for demonstrating the process of cut | disconnecting a workpiece to a quartz chip. (A) is a photograph showing the surface of the object to be processed on which the second modified spot according to the present embodiment is formed, and (b) is a photograph corresponding to a cross section taken along line bb in FIG. 13 (a). FIG. It is a photograph figure which shows the surface of the process target object in which the 2nd modified spot which concerns on a comparative example was formed.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.

  In the laser processing method according to the present embodiment, the laser beam is focused on the object to be processed, and a modified region including a plurality of modified spots is formed along the planned cutting line. First, the formation of the modified region will be described with reference to FIGS.

  As shown in FIG. 1, a laser processing apparatus 100 includes a laser light source 101 that oscillates a laser beam L, a dichroic mirror 103 that is arranged so as to change the direction of the optical axis (optical path) of the laser beam L, and A condensing lens (condensing optical system) 105 for condensing the laser light L. Further, the laser processing apparatus 100 includes a support base 107 for supporting the workpiece 1 irradiated with the laser light L condensed by the condensing lens 105, and a stage 111 for moving the support base 107. , A laser light source control unit 102 for controlling the laser light source 101 to adjust the output, pulse width, pulse waveform, and the like of the laser light L, and a stage control unit 115 for controlling the movement of the stage 111.

  In this laser processing apparatus 100, the laser light L emitted from the laser light source 101 has its optical axis changed by 90 ° by the dichroic mirror 103, and the inside of the processing object 1 placed on the support base 107. The light is condensed by the condensing lens 105. At the same time, the stage 111 is moved, and the workpiece 1 is moved relative to the laser beam L along the planned cutting line 5. As a result, a modified region along the planned cutting line 5 is formed on the workpiece 1. Here, the stage 111 is moved in order to move the laser light L relatively, but the condensing lens 105 may be moved, or both of them may be moved.

  The processing object 1 is formed of quartz, and as shown in FIG. 2, a cutting line 5 for cutting the processing object 1 is set in the processing object 1. The planned cutting line 5 is a virtual line extending linearly. When the modified region is formed inside the workpiece 1, as shown in FIG. 3, the laser beam L is scheduled to be cut in a state where the focusing point (focusing position) P is aligned with the inside of the workpiece 1. It moves relatively along the line 5 (that is, in the direction of arrow A in FIG. 2). Thereby, as shown in FIGS. 4 to 6, the modified region 7 is formed inside the workpiece 1 along the planned cutting line 5, and the modified region 7 formed along the planned cutting line 5 is formed. It becomes the cutting start area 8.

  In addition, the condensing point P is a location where the laser light L is condensed. Further, the planned cutting line 5 is not limited to a straight line, but may be a curved line, a three-dimensional shape in which these lines are combined, or a coordinate designated. Further, the planned cutting line 5 is not limited to a virtual line but may be a line actually drawn on the surface 3 of the workpiece 1. The modified region 7 may be formed continuously or intermittently. Further, the modified region 7 may be in the form of a line or a dot. In short, the modified region 7 only needs to be formed at least inside the workpiece 1. In addition, a crack may be formed starting from the modified region 7, and the crack and the modified region 7 may be exposed on the outer surface (front surface 3, back surface 21, or outer peripheral surface) of the workpiece 1. Good. Further, the laser light incident surface when forming the modified region 7 is not limited to the front surface 3 of the workpiece 1 but may be the back surface 21 of the workpiece 1.

  Incidentally, the laser light L here passes through the workpiece 1 and is particularly absorbed near the condensing point inside the workpiece 1, thereby forming the modified region 7 in the workpiece 1. (Ie, internal absorption laser processing). Therefore, since the laser beam L is hardly absorbed by the surface 3 of the workpiece 1, the surface 3 of the workpiece 1 is not melted. In general, when a removed portion such as a hole or a groove is formed by being melted and removed from the front surface 3 (surface absorption laser processing), the processing region gradually proceeds from the front surface 3 side to the back surface side.

  By the way, the modified region formed in the present embodiment refers to a region where the density, refractive index, mechanical strength, and other physical characteristics are different from the surroundings. Examples of the reforming region include a melting treatment region (meaning at least one of a region once solidified after melting, a region in a molten state, and a region in a state of being resolidified from melting), a crack region, There are dielectric breakdown regions, refractive index change regions, and the like, and there are also regions where these are mixed. Furthermore, as the modified region, there are a region where the density of the modified region in the material of the workpiece is changed compared to the density of the non-modified region, and a region where lattice defects are formed. Also known as the metastatic region).

In addition, the area where the density of the melt-processed area, the refractive index changing area, the modified area is changed compared to the density of the non-modified area, or the area where lattice defects are formed is In some cases, cracks (cracks, microcracks) are included in the interface between the non-modified region and the non-modified region. The included crack may be formed over the entire surface of the modified region, or may be formed in only a part or a plurality of parts. As the processing object 1, quartz (SiO ₂ ) or a material containing quartz is used.

  Further, in the present embodiment, the modified region 7 is formed by forming a plurality of modified spots (processing marks) along the planned cutting line 5. The modified spot is a modified portion formed by one pulse shot of pulsed laser light (that is, one pulse of laser irradiation: laser shot). Examples of the modified spot include a crack spot, a melting treatment spot, a refractive index change spot, or a mixture of at least one of these.

  Considering the required cutting accuracy, required flatness of the cut surface, thickness of the workpiece, type, crystal orientation, etc., the size of the modified spot and the length of the crack to be generated are appropriately determined. It is preferable to control.

  Next, the laser processing apparatus according to this embodiment will be described.

  As shown in FIG. 7, the laser processing apparatus 200 includes a support base 201 that supports the plate-shaped workpiece 1, a laser light source 202 that emits laser light L, and laser light L emitted from the laser light source 202. A collection of the spatial light modulator 203 for correcting the aberration and the laser beam L corrected for aberration by the reflective spatial light modulator 203 inside the workpiece 1 supported by the support table 201. The optical optical system 204 and the control part (control means) 205 which controls at least the reflection type spatial light modulator 203 are provided. The laser processing apparatus 200 forms a modified region 7 including a plurality of modified spots along the planned cutting line 5 of the workpiece 1 by irradiating the workpiece 1 with the laser beam L.

  The reflective spatial light modulator 203 is installed in the housing 231, and the laser light source 202 is installed on the top plate of the housing 231. The condensing optical system 204 includes a plurality of lenses, and is installed on the bottom plate of the housing 231 via a drive unit 232 including a piezoelectric element and the like. And the laser engine 230 is comprised by the components installed in the housing | casing 231. FIG. Note that the control unit 205 may be installed in the housing 231 of the laser engine 230.

  The housing 231 is provided with a moving mechanism that moves the housing 231 in the thickness direction of the workpiece 1 (not shown). Thereby, since the laser engine 230 can be moved up and down according to the depth of the workpiece 1, the position of the condensing optical system 204 is changed, and the laser beam L is changed to a desired depth of the workpiece 1. It is possible to condense at this position. Instead of installing a moving mechanism in the housing 231, a moving mechanism that moves the supporting table 201 in the thickness direction of the workpiece 1 may be provided on the supporting table 201. Further, the condensing optical system 204 may be moved in the thickness direction of the workpiece 1 using an AF unit 212 described later. It is also possible to combine these.

  The control unit 205 controls the reflection type spatial light modulator 203 and also controls the entire laser processing apparatus 200. For example, when the control unit 205 forms the modified region 7, the condensing point P of the laser light L is located at a predetermined distance from the surface (laser light incident surface) 3 of the workpiece 1 and the laser light L The laser engine 230 including the condensing optical system 204 is controlled so that the condensing point P of the light beam moves relatively along the cutting scheduled line 5. The control unit 205 controls the support base 201 instead of the laser engine 230 including the condensing optical system 204 in order to move the condensing point P of the laser light L relative to the workpiece 1. Alternatively, both the laser engine 230 including the condensing optical system 204 and the support base 201 may be controlled.

  The laser light L emitted from the laser light source 202 is sequentially reflected by the mirrors 206 and 207 in the housing 231, and then reflected by the reflecting member 208 such as a prism and enters the reflective spatial light modulator 203. The laser beam L incident on the reflective spatial light modulator 203 is modulated by the reflective spatial light modulator 203 and emitted from the reflective spatial light modulator 203. The laser light L emitted from the reflective spatial light modulator 203 is reflected by the reflecting member 208 along the optical axis of the condensing optical system 204 in the housing 231 and sequentially passes through the beam splitters 209 and 210. Then, it enters the condensing optical system 204. The laser light L incident on the condensing optical system 204 is condensed by the condensing optical system 204 inside the workpiece 1 placed on the support table 201.

  In addition, the laser processing apparatus 200 includes a surface observation unit 211 for observing the surface 3 of the workpiece 1 in the housing 231. The surface observation unit 211 emits visible light VL reflected by the beam splitter 209 and transmitted through the beam splitter 210, collected by the condensing optical system 204, and reflected by the surface 3 of the workpiece 1. Is detected, an image of the surface 3 of the workpiece 1 is acquired.

  Further, the laser processing apparatus 200 performs AF for accurately aligning the condensing point P of the laser light L at a predetermined distance from the surface 3 even when the surface 3 of the workpiece 1 is wavy. A (autofocus) unit 212 is provided in the housing 231. The AF unit 212 emits AF laser light LB reflected by the beam splitter 210, and detects the AF laser light LB condensed by the condensing optical system 204 and reflected by the surface 3 of the workpiece 1. Thus, the displacement data of the surface 3 along the planned cutting line 5 is acquired using, for example, an astigmatism method. Then, the AF unit 212 drives the drive unit 232 based on the acquired displacement data when forming the modified region 7, so that the condensing optical system follows the undulation of the surface 3 of the workpiece 1. 204 is reciprocated in the optical axis direction to finely adjust the distance between the condensing optical system 204 and the workpiece 1.

  Here, the reflective spatial light modulator 203 will be described. The reflective spatial light modulator 203 corrects the aberration of the laser light L emitted from the laser light source 202, for example, a reflective liquid crystal on silicon (LCOS) spatial light modulator (SLM: Spatial Light). Modulator) is used. FIG. 8 is a partial cross-sectional view of the reflective spatial light modulator of the laser processing apparatus of FIG. As shown in FIG. 8, the reflective spatial light modulator 203 includes a silicon substrate 213, a drive circuit layer 914, a plurality of pixel electrodes 214, a reflective film 215 such as a dielectric multilayer mirror, an alignment film 999a, a liquid crystal layer 216, An alignment film 999b, a transparent conductive film 217, and a transparent substrate 218 such as a glass substrate are provided, and these are stacked in this order.

  The transparent substrate 218 has a surface 218 a along the XY plane, and the surface 218 a constitutes the surface of the reflective spatial light modulator 203. The transparent substrate 218 mainly contains a light transmissive material such as glass, for example, and the laser light L having a predetermined wavelength incident from the surface 218 a of the reflective spatial light modulator 203 is converted into the interior of the reflective spatial light modulator 203. To penetrate. The transparent conductive film 217 is formed on the back surface 218b of the transparent substrate 218, and mainly includes a conductive material (for example, ITO) that transmits the laser light L.

  The plurality of pixel electrodes 214 are two-dimensionally arranged according to the arrangement of the plurality of pixels, and are arranged on the silicon substrate 213 along the transparent conductive film 217. Each pixel electrode 214 is made of a metal material such as aluminum, for example, and the surface 214a is processed flat and smoothly. The plurality of pixel electrodes 214 are driven by an active matrix circuit provided in the drive circuit layer 914.

  The active matrix circuit is provided between the plurality of pixel electrodes 214 and the silicon substrate 213, and controls the voltage applied to each pixel electrode 214 in accordance with the optical image to be output from the reflective spatial light modulator 203. . Such an active matrix circuit includes, for example, a first driver circuit that controls the applied voltage of each pixel column arranged in the X-axis direction (not shown) and a first driver circuit that controls the applied voltage of each pixel column arranged in the Y-axis direction. And a predetermined voltage is applied to the pixel electrode 214 of the pixel designated by both of the driver circuits by the control unit 250.

  Note that the alignment films 999a and 999b are disposed on both end surfaces of the liquid crystal layer 216, and align liquid crystal molecule groups in a certain direction. The alignment films 999a and 999b are made of, for example, a polymer material such as polyimide, and the contact surface with the liquid crystal layer 216 is subjected to a rubbing process or the like.

  The liquid crystal layer 216 is disposed between the plurality of pixel electrodes 214 and the transparent conductive film 217, and modulates the laser light L according to the electric field formed by each pixel electrode 214 and the transparent conductive film 217. That is, when a voltage is applied to a certain pixel electrode 214 by the active matrix circuit, an electric field is formed between the transparent conductive film 217 and the pixel electrode 214.

  This electric field is applied to each of the reflective film 215 and the liquid crystal layer 216 at a rate corresponding to the thickness of each. Then, the alignment direction of the liquid crystal molecules 216a changes according to the magnitude of the electric field applied to the liquid crystal layer 216. When the laser light L passes through the transparent substrate 218 and the transparent conductive film 217 and enters the liquid crystal layer 216, the laser light L is modulated by the liquid crystal molecules 216 a while passing through the liquid crystal layer 216 and reflected by the reflective film 215. Then, the light is again modulated by the liquid crystal layer 216 and taken out. Then, an aberration correction (wavefront shaping) pattern for shaping (modulating) the beam wavefront of the laser light L is displayed on the liquid crystal layer 216, whereby the laser light L transmitted through the aberration correction pattern of the liquid crystal layer 216 Aberration is corrected by phase modulation according to the aberration correction pattern.

  When forming the modified region 7, the control unit 205 inputs pattern information related to the aberration correction pattern to the reflective spatial light modulator 203 and displays a predetermined aberration correction pattern on the liquid crystal layer 216, thereby reflecting the reflective type. The aberration of the laser beam L emitted from the spatial light modulator 203 is controlled. Note that the pattern information input to the reflective spatial light modulator 203 may be input sequentially, or pattern information stored in advance may be selected and input.

  Strictly speaking, the laser light L whose aberration is corrected by the reflective spatial light modulator 203 changes its wavefront shape by propagating through the space. In particular, when the laser light L emitted from the reflective spatial light modulator 203 or the laser light L incident on the condensing optical system 204 is light having a predetermined spread (that is, light other than parallel light), the reflective light The wavefront shape in the spatial light modulator 203 and the wavefront shape in the condensing optical system 204 do not coincide with each other, and as a result, there is a possibility that the target precise internal processing may be hindered. Therefore, it is important to match the wavefront shape in the reflective spatial light modulator 203 with the wavefront shape in the condensing optical system 204. For this purpose, the change in the wavefront shape when the laser light L propagates from the reflective spatial light modulator 203 to the condensing optical system 204 is obtained by measurement or the like, and the pattern information of the aberration correction pattern in consideration of the change in the wavefront shape Is more preferably input to the reflective spatial light modulator 203.

  Alternatively, in order to make the wavefront shape in the reflective spatial light modulator 203 coincide with the wavefront shape in the condensing optical system 204, as shown in FIG. 9, the reflective spatial light modulator 203 and the condensing optical system 204 are used. The adjusting optical system 240 may be provided on the optical path of the laser light L traveling between the two. This makes it possible to accurately realize wavefront shaping.

  The adjustment optical system 240 has at least two lenses 241a and 241b. The lenses 241a and 241b are for making the wavefront shape in the reflective spatial light modulator 203 and the wavefront shape in the condensing optical system 204 similar. In the lenses 241a and 241b, the distance between the reflective spatial light modulator 203 and the lens 241a is the focal length f1 of the lens 241a, the distance between the condensing optical system 204 and the lens 241b is the focal length f2 of the lens 241b, and the lens 241a. And the lens 241b are disposed between the reflective spatial light modulator 203 and the reflective member 208 so that the lens 241a and the lens 241b form a double-sided telecentric optical system.

  By arranging in this way, even with the laser light L having a small divergence angle of about 1 ° or less, the wavefront in the reflective spatial light modulator 203 and the wavefront in the condensing optical system 204 can be matched. it can. The beam diameter of the laser light L is determined by the ratio of f1 and f2 (the beam diameter of the laser light L incident on the condensing optical system 204 is determined by the laser light L emitted from the reflective spatial light modulator 203. F2 / f1 times the beam diameter). Therefore, regardless of whether the laser light L is parallel light or light having a small spread, the laser incident on the condensing optical system 204 while maintaining the angle emitted from the reflective spatial light modulator 203. A desired beam diameter in the light L can be obtained.

  The adjustment optical system 240 preferably includes a mechanism for finely adjusting the positions of the lenses 241a and 241b independently. In order to effectively use the effective area of the reflective spatial light modulator 203, a beam expander may be provided on the optical path of the laser light L between the reflective spatial light modulator 203 and the laser light source 202. .

  Next, the laser processing method according to this embodiment will be described.

  The laser processing method of the present embodiment is used, for example, as a method for manufacturing a crystal unit for manufacturing a crystal unit, and laser processing is performed on a processing target 1 formed of crystal that is a hexagonal columnar crystal. The apparatus 200 cuts into a plurality of crystal chips. First, an overall manufacturing process flow of the crystal resonator will be described with reference to FIG.

  First, the raw quartz crystal is cut out by, for example, diamond grinding and processed into a rod-shaped body (lumbard) of a predetermined size (S1). Subsequently, the cutting angle corresponding to the temperature characteristic requirement of the crystal resonator is measured by X-rays, and the lambard is cut into a plurality of wafer-like workpieces 1 by wire saw processing based on this cutting angle (S2). The workpiece 1 here has a rectangular plate shape of 10 mm × 10 mm, and has a crystal axis inclined by 35.15 ° with respect to the thickness direction.

  Subsequently, lapping is performed on the front surface 3 and the back surface 21 of the workpiece 1 and the thickness is set to a predetermined thickness (S3). Subsequently, the cutting angle is measured by X-rays at a minute angle level, and after selecting and classifying the workpiece 1, lapping processing similar to the above S3 is performed again on the front surface 3 and the back surface 21 of the workpiece 1. Then, the thickness of the workpiece 1 is finely adjusted to, for example, about 100 μm (S4, S5).

  Then, as the cutting process and the outer shape process, the modified region 7 is formed in the workpiece 1, and the workpiece 1 is cut along the planned cutting line 5 using the modified region 7 as a starting point for cutting (S6: , Described later). As a result, a plurality of crystal chips having external dimensions with a dimensional accuracy of ± several μm or less are obtained. In the present embodiment, the line 5 to be cut is set in the processing object 1 in a lattice shape when viewed from the front surface 3, and the processing object 1 is cut as a rectangular plate-shaped crystal chip of 1 mm × 0.5 mm.

  Subsequently, the quartz chip is subjected to chamfering (convex machining) so as to have a predetermined frequency, and the thickness of the quartz chip is adjusted by etching so as to have a predetermined frequency (S7, S8). Thereafter, the crystal chip is assembled as a crystal resonator (S9). Specifically, an electrode is formed on the crystal chip by sputtering, this crystal chip is mounted in the mounter, heat-treated in a vacuum atmosphere, and then the crystal chip electrode is shaved by ion etching to adjust the frequency. Seal the seam. Thereby, the manufacture of the crystal unit is completed.

  FIG. 8 is a schematic diagram for explaining a process of cutting a workpiece into a quartz chip. In the drawing, for convenience of explanation, the cutting along one cutting scheduled line 5 is illustrated as an example. In S6 for cutting the workpiece 1 into a crystal chip, first, the expanded tape 31 is attached to the back surface 21 of the workpiece 1 and the workpiece 1 is placed on the support table 201 (see FIG. 7). .

  Subsequently, the control unit 205 controls the laser engine 230 and the reflective spatial light modulator 203, and appropriately converges the laser beam L on the workpiece 1 along the scheduled cutting line 5, so that a plurality of modified spots S are obtained. The modified region 7 including the material is formed (modified region forming step).

Specifically, as shown in FIG. 11 (a), while irradiating the laser beam L from the surface 3 side with an output of 0.03 W, a repetition frequency of 15 kHz, and a pulse width of 500 picoseconds to 640 picoseconds, for example, L is relatively moved along the planned cutting line 5, and a plurality of first modified spots S1 located only inside the workpiece ₁ are formed in a line along the planned cutting line 5 (first scan).

Subsequently, as shown in FIG. 11B, while irradiating the laser beam L from the surface 3 side with an output of 0.03 W, a repetition frequency of 15 kHz, and a pulse width of 500 picoseconds to 640 picoseconds, It is relatively moved along the line to cut 5, a plurality of the second reforming spot S ₂ a row formed along the line to cut 5 exposed to the surface 3 of the object 1 (second scan).

Here, during the second reforming to form a spot S ₂ the second scan exposed on the surface 3 of the laser light entrance surface, instead of being focused solely on the surface 3 of the object 1 with laser light L When the aberration of the laser beam L is corrected so that the focal point is positioned near the surface 3 in the workpiece 1, the so-called idling phenomenon (the modified spot S even if the laser beam L is condensed on the workpiece 1). It is found that the occurrence of a phenomenon in which no is formed can be suppressed.

  In the second scan, therefore, a predetermined aberration correction pattern for correcting the aberration of the laser beam L so that the condensing point of the laser beam L is positioned in the vicinity of the surface 3 in the workpiece 1 is reflected by spatial reflection light modulation. The image is displayed on the liquid crystal layer 216 of the vessel 203. At the same time, the focal point of the condensing optical system 204 is positioned on the surface 3 of the workpiece 1. In this state, the laser beam L is irradiated from the surface 3 side, that is, the laser beam L whose aberration is corrected so that the focal point is located near the surface 3 in the workpiece 1 is a surface as a laser beam incident surface. 3 to collect light.

  In particular, in the second scan of the present embodiment, a predetermined aberration correction pattern for positioning the focal point at a position 1 μm to 2 μm inside from the surface 3 in the workpiece 1 is displayed on the liquid crystal layer 216. Thus, the laser beam L whose aberration is corrected so that the condensing point is located at a position 1 μm to 2 μm inside from the surface 3 in the workpiece 1 is condensed on the surface 3.

As a result, as shown in FIG. 13, it is possible to suppress the occurrence of a so-called idling phenomenon, and to form a plurality of second modifications exposed on the surface 3 without forming a half cut that is a crack exposed on the surface 3. Only the spot S ₂ (that is, the modified region 7 intermittently exposed from the surface 3) can be continuously formed cleanly along the planned cutting line 5.

  Subsequently, after the first and second scans are performed for all the planned cutting lines 5, as shown in FIG. 12A, the workpiece 1 is cut from the back surface 21 side through the expanded tape 31. The knife edge 32 is pressed along the planned line 5 and a force is applied to the workpiece 1 from the outside along the planned cutting line 5 (cutting process).

Thus, reforming spots with first reforming spots S ₁ more acts primarily as contributing reforming spot cutting, as intermittent surface dents which second reforming spots S ₂ multiple assists the cutting The workpiece 1 is cut into a plurality of quartz chips using the modified region 7 as a starting point for cutting. Then, as shown in FIG. 12B, the expanding tape 31 is expanded to ensure a chip interval. Thus, the workpiece 1 is cut as a plurality of crystal chips 10.

As described above, in the present embodiment, a plurality of first modified spots S ₁ positioned inside the workpiece ₁ are formed along the planned cutting line 5 and a plurality of second modified spots exposed on the surface 3. spot S ₂ is formed along the line to cut 5. Therefore, the object 1 is easily cut along the line to cut 5 by a plurality of first reforming spots S _1, and the second reforming spots S ₂ more exposed on the surface 3 is a so-called tear-off line act so, such cutting is to be assisted by the second reforming spots S ₂ of the plurality. Therefore, the workpiece 1 can be cut with high dimensional accuracy, and the processing quality can be improved.

In particular, when a half-cut is generated in the workpiece 1 formed of quartz, the half-cut is easy to meander due to the processing characteristics of the quartz, for example, so that the dimensional accuracy of the workpiece 1 after cutting is controlled. It is not easy to do. In this regard, in the present embodiment, as described above, since the half-cut may be laser processing so as not to be formed from the second reforming spots S _2, the workpiece 1 can be cut more dimensional accuracy.

  Further, in the present embodiment, as described above, external stress is applied to the workpiece 1 along the planned cutting line 5 using the knife edge 32, and the workpiece 1 is set with the modified region 7 as a starting point of cutting. doing. Thereby, even if it is the process target object 1 formed with the crystal which is hard to cut | disconnect, it becomes possible to cut | disconnect the process target object 1 accurately along the cutting scheduled line 5 reliably.

When forming the second modified spot S ₂ exposed on the surface 3, the laser beam L corrected for aberration so that the focal point is located at a position less than 1 μm from the surface 3 in the workpiece 1 is applied to the surface 3. When condensing, and when condensing the laser beam L corrected for aberration so that the condensing point is located at a position more than 2 μm away from the surface 3, a so-called idling phenomenon is likely to occur. Therefore, in these cases, the processing quality is degraded.

FIG. 14 is a photographic diagram showing the surface of the workpiece on which the second modified spot according to the comparative example is formed. In the figure, the laser beam L whose aberration has been corrected so that the focal point is located at a position 3 to 6 μm inside from the surface 3 in the workpiece 1 is condensed on the surface 3 to form the second modified spot S ₂ . Forming. As shown in FIG. 14, when the second modified spot S ₂ exposed on the surface 3 is formed, aberration correction is performed so that the condensing point is located deep from the surface 3, and the laser light L is collected on the surface 3. When light is applied, it can be seen that an idling phenomenon has occurred (see the frame in the figure).

Incidentally, since a crystal resonator is a device that uses the characteristics of the crystal material itself, the dimensional accuracy of a crystal chip for a crystal resonator greatly affects temperature characteristics and resonator characteristics. In this respect, the present embodiment that can cut the workpiece 1 with high dimensional accuracy as a quartz chip is particularly effective. Further, even if the second reforming spots S ₂ remained (exposed) on the surface 3, it is small effect on the temperature characteristics and the transducer characteristics of the crystal chip. Further, simply increasing the processing point output of the laser beam L is not preferable because it is difficult not only to suppress the so-called idling phenomenon but also to easily cause burns and scratches on the surface 3.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. The present invention can be modified without departing from the scope described in the claims or applied to other embodiments. May be.

  For example, although the LCOS-SLM is used as the reflective spatial light modulator 203 in the above embodiment, a MEMS-SLM, a DMD (deformable mirror device), or the like may be used. Although the reflective spatial light modulator 203 of the above embodiment includes the dielectric multilayer mirror, the reflection of the pixel electrode of the silicon substrate may be used. Furthermore, although the reflective spatial light modulator 203 is used in the above embodiment, a transmissive spatial light modulator may be used. Examples of the spatial light modulator include a liquid crystal cell type and an LCD type.

Moreover, in the said embodiment, it is made to 2nd by condensing on the said laser beam L surface 3 in the state which correct | amended the aberration of the laser beam L so that a condensing point may be located in the surface 3 vicinity in the workpiece 1. FIG. While forming the modified spots S _2, is not limited to this, short, it is sufficient form to a second reforming spots exposed to the laser light entrance surface of the half-cutting does not occur. For example, the control unit 205 may form a second reformed spot S ₂ by appropriately controlling the laser processing apparatus 200.

Further, in the above embodiment, to form a second reformed spots S ₂ after forming the first modified spots S _1, the first reforming spots S ₁ after forming the second modified spots S ₂ May be formed. When a plurality of rows of modified regions 7 having different positions in the thickness direction are formed on the workpiece 1, the order of forming these modified regions 7 is in no particular order.

  In the above, each numerical value relating to aberration correction allows errors in processing, manufacturing, design, and the like. The present invention can also be regarded as a crystal resonator manufacturing method or manufacturing apparatus for manufacturing a crystal resonator by the laser processing method described above, but is not limited to a crystal resonator manufacturing method and is formed of crystal. The present invention can be applied to various methods or apparatuses for cutting a workpiece.

1 ... workpiece, 5 ... line to cut 7 ... modified region, L ... laser light, S ... modified spot, S 1 _... first modified spot, S 2 _... second modified spots.

It is a schematic block diagram of the laser processing apparatus used for formation of a modification area | region. It is a top view of the processing target object used as the object of formation of a modification field. It is sectional drawing along the III-III line of the workpiece of FIG. It is a top view of the processing target after laser processing. It is sectional drawing along the VV line of the workpiece of FIG. It is sectional drawing along the VI-VI line of the processing target object of FIG. It is a schematic block diagram of the laser processing apparatus which concerns on this embodiment. It is a fragmentary sectional view of the reflection type spatial light modulator of the laser processing apparatus of FIG. It is a schematic block diagram of the other laser processing apparatus which concerns on this embodiment. It is a flowchart which shows the manufacturing process of the crystal oscillator which concerns on this embodiment. It is the schematic for demonstrating the process of cut | disconnecting a workpiece to a quartz chip. It is another schematic diagram for demonstrating the process of cut | disconnecting a workpiece to a quartz chip. The (A) is a photograph showing the surface of the object to be processed on which the second modified spot according to the present embodiment is formed, and (b) is a photograph corresponding to a cross section taken along line bb in FIG. 13 (a). FIG. It is a photograph figure which shows the surface of the process target object in which the 2nd modified spot which concerns on a comparative example was formed.

Claims (2)

A laser processing method for cutting a processing object formed of crystal along a planned cutting line,
A focused region forming step of forming a modified region including a plurality of modified spots on the workpiece along the planned cutting line by condensing a laser beam on the workpiece;
The modified region forming step includes
While irradiating the laser beam to the object to be processed, the object is relatively moved along the planned cutting line, and a plurality of first modified spots located inside the processing object are formed along the planned cutting line. Process,
A plurality of second modified spots exposed to the laser beam incident surface of the workpiece are moved relative to each other along the planned cutting line while irradiating the laser beam to the workpiece, and the laser beam incident surface Forming along the planned cutting line so as not to form a crack exposed to the surface.   The method further comprises a cutting step of cutting the workpiece from the modified region as a starting point by applying a force to the workpiece from the outside along the planned cutting line. The laser processing method according to 1.