JP2002205181A - Device and method for laser beam machining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for laser beam machining with which a work to be machined is precisely cut without a molten part or a crack which is deviated from a planned cutting line on the surface of the work to be machined. SOLUTION: The device is provided with a laser beam source 101 which emits a pulse laser beam of which pulse width is 1 μs smaller, a power adjustment part 401 which adjusts the magnitude of the power of the pulse laser beam, a lens selection mechanism 403 including a plurality of condenser lenses which condense the pulse laser beam so that the peak power density at the focal point P of the pulse laser beam becomes 1×108 (W/cm2) or larger, a Z-axis stage 113 with which the focal point P of the pulse laser beam condensed with the condenser lenses is positioned inside the work 1 to be machined, and an X (Y)-axis stages 109 (111) which relatively moves the focal point P along the planned cutting line 5 of the work 1 to be machined. The respective aperture numbers of optical system including the condenser lenses 105a to 105c are different from one another. The dimension of a property modification spot formed inside the work 1 to be machined is controlled by adjusting the aperture number and the magnitude of the power of the pulse laser beam. The dimension is displayed prior to the machining with the laser beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor material substrate,
The present invention relates to a laser processing apparatus and a laser processing method used for cutting a processing target such as a piezoelectric material substrate or a glass substrate.

[0002]

2. Description of the Related Art One of laser applications is cutting. A general cutting by a laser is as follows. For example, a portion to be cut of a processing object such as a semiconductor wafer or a glass substrate is irradiated with laser light having a wavelength that is absorbed by the processing object, and is directed from the front surface to the back surface of the processing object at a position where the cutting is performed by absorbing the laser light. The workpiece is cut by heating and melting. However, in this method, the periphery of a region to be cut on the surface of the workpiece is also melted. Therefore, when the object to be processed is a semiconductor wafer, of the semiconductor elements formed on the surface of the semiconductor wafer, there is a possibility that the semiconductor elements located around the above-mentioned region may be melted.

[0003]

As a method for preventing the surface of a workpiece from melting, for example, Japanese Patent Laid-Open No. 2000-21
There is a cutting method using a laser disclosed in JP-A-9528 and JP-A-2000-15467. In the cutting methods disclosed in these publications, a portion to be cut of a processing object is heated by a laser beam, and the processing object is cooled,
The object to be processed is cut by generating a thermal shock at a position where the object to be processed is cut.

However, according to the cutting methods disclosed in these publications, if the thermal shock generated on the object to be processed is large, the surface of the object to be processed may have cracks that deviate from the line to be cut or cracks up to a point not irradiated with laser. Unnecessary cracks such as may occur. Therefore, precision cutting cannot be performed by these cutting methods. In particular, the processing object is a semiconductor wafer,
In the case of a glass substrate on which a liquid crystal display device is formed and a glass substrate on which an electrode pattern is formed, the unnecessary chip may damage the semiconductor chip, the liquid crystal display device, and the electrode pattern. In addition, since these cutting methods have a large average input energy, thermal damage to semiconductor chips and the like is also large.

An object of the present invention is to provide a laser processing apparatus and a laser processing method that do not cause unnecessary cracks on the surface of a workpiece and do not melt the surface.

[0006]

According to the present invention, there is provided a laser processing apparatus which emits a pulse laser beam having a pulse width of 1 μs or less, and which emits a pulse laser beam based on an input of the power level of the pulse laser beam. Power adjusting means for adjusting the magnitude of the power of the pulsed laser light to be applied, and a peak power density at a focal point of the pulsed laser light emitted from the laser light source is 1 × 10 ⁸ (W / cm ² ) or more. A focusing means for focusing the pulsed laser light on the workpiece, a means for adjusting a focusing point of the pulsed laser light focused by the focusing means to the inside of the processing object, and a pulse along a line to cut the processing object. Moving means for relatively moving the focal point of the laser light,
The laser beam of one pulse is irradiated on the processing object by adjusting the focal point inside the processing object, thereby forming one modified spot inside the processing object, and adjusted by the power adjusting means. Correlation storage means for storing in advance the correlation between the magnitude of the power of the pulsed laser light and the size of the modified spot, and forming with the power of this magnitude based on the magnitude of the power of the input pulsed laser light The size of the modified spot to be selected is selected from the correlation storage means, and the dimension display means for displaying the dimension of the modified spot selected by the size selecting means is provided.

According to the laser processing apparatus of the present invention, the focal point of the pulse laser beam is adjusted to the inside of the object to be processed, and the peak power density at the focal point is 1 × 10 ⁸ (W / c).
m ² ) or more and the pulse width is 1 μs or less, the object to be processed can be irradiated with pulsed laser light. Therefore, when pulsed laser light is irradiated on a processing target using the laser processing apparatus according to the present invention, a phenomenon called multiphoton absorption occurs inside the processing target, thereby forming a modified region inside the processing target. Is done. If there is any starting point at the cutting position of the object, the object can be cut by relatively small force. Therefore, the object processed using the laser processing apparatus according to the present invention can be cut by breaking or breaking along the line to be cut starting from the modified region. Therefore, since the object to be processed can be cut with a relatively small force, the object to be processed can be cut without generating unnecessary cracks on the surface of the object to be cut off the line to be cut.

Further, according to the laser processing apparatus of the present invention, the modified region is formed by locally generating multiphoton absorption inside the object to be processed. Therefore, since the laser light is hardly absorbed on the surface of the processing object, the surface of the processing object does not melt. Note that the focal point is a point where the laser light is focused. The line to be cut may be a line actually drawn on the surface or inside of the object to be processed, or a virtual line. The above applies to the laser processing apparatus and the laser processing method to be described below.

According to the present inventor, it is possible to control the modified spot to be smaller when the power of the pulse laser beam is reduced, and to control the modified spot to be larger when the power of the pulse laser beam is increased. Do you get it. The modified spot is a modified portion formed by one pulse of the laser beam, and the modified spot is collected to form a modified region. Controlling the dimensions of the modification spot affects the cutting of the workpiece. That is, if the modified spot is too large, the accuracy of cutting along the line to cut the object to be processed and the flatness of the cut surface deteriorate. on the other hand,
If the modified spot is too small for a processing object having a large thickness, it becomes difficult to cut the processing object. ADVANTAGE OF THE INVENTION According to the laser processing apparatus which concerns on this invention, the size of a modified spot can be controlled by adjusting the magnitude of the power of a pulse laser beam.

Further, the laser processing apparatus according to the present invention comprises a correlation storage means for storing in advance the correlation between the magnitude of the power of the pulsed laser beam and the dimension of the modified spot.
The dimensions of the modified spot formed with the power of this magnitude are selected from the correlation storage means based on the magnitude of the power of the input pulsed laser light, and the dimensions of the selected modified spot are displayed. . Therefore, the dimension of the modified spot formed by the magnitude of the power of the pulsed laser beam input to the laser processing apparatus can be known before the laser processing.

A laser processing apparatus according to the present invention has a laser light source that emits a pulse laser light having a pulse width of 1 μs or less, and a peak power density of a focal point of the pulse laser light emitted from the laser light source is 1 × 10 ^8. regulation and (W / cm ²⁾ or greater in comprising as a condenser lens for the pulsed laser light is condensed, based on the input of the size of the aperture of the numerical aperture of the optical system including a lens for concentrating light size Means for adjusting the numerical aperture of the laser beam, means for adjusting the focal point of the pulsed laser beam focused by the focusing lens to the inside of the object, and focusing of the pulsed laser beam along a line to be cut of the object. Moving means for relatively moving the point, and irradiating the processing object with one pulse of pulsed laser light with the converging point set inside the processing object, thereby providing one modification inside the processing object. Quality spots are formed and the numerical aperture Correlation storage means in which the correlation between the size of the numerical aperture adjusted by the means and the size of the modified spot is stored in advance, and the numerical aperture of this size is formed based on the input numerical aperture. Dimension selection means for selecting the dimensions of the modified spot from the correlation storage means,
And dimension display means for displaying the dimension of the modified spot selected by the dimension selection means.

According to the present inventors, it has been found that the modified spot can be controlled to be small by increasing the numerical aperture of the optical system including the condenser lens, and that the modified spot can be controlled to be large by reducing the numerical aperture. Therefore, according to the laser processing apparatus of the present invention, the size of the modified spot can be controlled by adjusting the numerical aperture of the optical system including the condensing lens.

Further, the laser processing apparatus according to the present invention is provided with a correlation storage means for storing in advance the correlation between the size of the numerical aperture and the size of the modified spot. Based on the input numerical aperture, the dimensions of the modified spot formed with the numerical aperture of this size are selected from the correlation storage means, and the dimensions of the selected modified spot are displayed. Therefore, the dimension of the modified spot formed by the numerical aperture input to the laser processing apparatus can be known before the laser processing.

In the laser processing apparatus according to the present invention, a laser light source that emits a pulse laser beam having a pulse width of 1 μs or less, and a peak power density of a focal point of the pulse laser beam emitted from the laser light source is 1 × 10 ⁸ (W / cm ² ) or more, and a plurality of condenser lenses for condensing the pulsed laser light, and lens selecting means capable of selecting a plurality of condenser lenses. Each optical system has a different numerical aperture, means for adjusting the focal point of the pulsed laser light focused by the focusing lens selected by the lens selecting means to the inside of the processing object, and cutting of the processing object Moving means for relatively moving the focal point of the pulsed laser light along the line, and irradiating the object with one pulse of pulsed laser light by adjusting the focal point inside the object to be processed. Processing object Correlation storage means in which one modified spot is formed, in which a correlation between a size of a numerical aperture of an optical system including a plurality of condensing lenses and a dimension of the modified spot is stored in advance; A dimension selecting means for selecting, from the correlation storage means, a dimension of the modified spot formed with the numerical aperture of this size based on the magnitude of the numerical aperture of the optical system including the optical lens; And dimension display means for displaying the dimensions of the modified spot.

According to the laser processing apparatus of the present invention, the size of the modified spot can be controlled. Further, the size of the modified spot formed by the size of the numerical aperture of the optical system including the selected condensing lens can be known before laser processing.

A laser processing apparatus according to the present invention comprises a laser light source for emitting a pulse laser beam having a pulse width of 1 μs or less, and a pulse laser beam emitted from the laser light source based on an input of the power of the pulse laser beam. A power adjusting means for adjusting the magnitude of the power; and a peak power density at a focal point of the pulse laser light emitted from the laser light source is 1 ×
A condensing lens for condensing the pulsed laser beam so as to be 10 ⁸ (W / cm ² ) or more, and the numerical aperture of the optical system including the condensing lens based on the input of the numerical aperture Means for adjusting the numerical aperture, means for adjusting the focal point of the pulsed laser light condensed by the condenser lens to the inside of the object to be processed, and Moving means for relatively moving the focal point, and irradiating the processing object with one pulse of pulsed laser light by aligning the focal point inside the processing object, thereby providing one object inside the processing object. A modified spot is formed, and the correlation between the set of the magnitude of the power of the pulsed laser beam adjusted by the power adjusting means and the size of the numerical aperture adjusted by the numerical aperture adjusting means and the dimension of the modified spot is determined in advance. The stored correlation storage means; Dimension selection means for selecting the size of the modified spot formed with these magnitudes based on the magnitude of the power of the pulsed laser light and the magnitude of the input numerical aperture from the correlation storage means, And dimension display means for displaying the dimension of the modified spot selected by the dimension selection means.

According to the laser processing apparatus of the present invention, since the adjustment of the power and the adjustment of the numerical aperture can be combined, it is possible to increase the types of sizes in which the dimensions of the modified spot can be controlled. Further, for the same reason as in the laser processing apparatus according to the present invention, the dimensions of the modified spot can be known before laser processing.

A laser processing apparatus according to the present invention includes a laser light source for emitting a pulse laser beam having a pulse width of 1 μs or less, and a pulse laser beam emitted from the laser light source based on an input of the power magnitude of the pulse laser beam. A power adjusting means for adjusting the magnitude of the power; and a peak power density at a focal point of the pulse laser light emitted from the laser light source is 1 ×
A plurality of condenser lenses for condensing the pulsed laser beam so as to be 10 ⁸ (W / cm ² ) or more, and a lens selecting means capable of selecting a plurality of condenser lenses; Each of the optical systems including the lens has a different numerical aperture, means for adjusting the focal point of the pulsed laser light focused by the focusing lens selected by the lens selecting means to the inside of the processing object, and Moving means for relatively moving the focal point of the pulsed laser light along the line to be cut, and irradiating the object with one pulse of pulsed laser light by adjusting the focal point inside the object to be processed As a result, one modified spot is formed inside the object to be processed, and the magnitude of the power of the pulse laser beam adjusted by the power adjusting means and the magnitude of the numerical aperture of the optical system including the plurality of focusing lenses Pairs and reforming spots A correlation storage unit that stores a correlation with the dimensions in advance, and a storage unit based on the magnitude of the power of the input pulse laser light and the magnitude of the numerical aperture of the optical system including the selected condenser lens. A dimension selecting means for selecting the dimension of the modified spot formed by the size from the correlation storage means, and dimension displaying means for displaying the dimension of the modified spot selected by the dimension selecting means, I do.

According to the laser processing apparatus of the present invention, for the same reason as the laser processing apparatus of the present invention, it is possible to increase the number of types in which the dimensions of the modified spot can be controlled, Can be known before laser processing.

The laser processing apparatus described above comprises an image creating means for creating an image of the modified spot having the dimension selected by the dimension selecting means, and an image display means for displaying the image created by the image creating means. Can be provided. According to this, the modified spot to be formed can be visually grasped before laser processing.

The laser processing apparatus according to the present invention comprises: a laser light source for emitting a pulse laser light having a pulse width of 1 μs or less; power adjusting means for adjusting the power of the pulse laser light emitted from the laser light source; Focusing means for focusing the pulsed laser light so that the peak power density of the focused point of the pulsed laser light emitted from the laser light source is 1 × 10 ⁸ (W / cm ² ) or more; Means for adjusting the focal point of the emitted pulse laser light to the inside of the processing object, and moving means for relatively moving the focal point of the pulsed laser light along a line to be cut of the processing object, One modified spot is formed inside the processing object by irradiating the processing object with a pulse laser beam of one pulse with the focal point adjusted inside the processing object, and the pulse is adjusted by the power adjusting means. Correlation storage means in which the correlation between the power of the laser beam and the dimension of the modified spot is stored in advance, and the magnitude of the power of the pulse laser beam that can be formed to this dimension based on the input of the dimension of the modified spot. Power selection means for selecting from the correlation storage means,
The power adjusting means adjusts the magnitude of the power of the pulse laser light emitted from the laser light source so as to have the magnitude of the power selected by the power selecting means.

According to the laser processing apparatus of the present invention, there is provided a correlation storage means for storing in advance the correlation between the magnitude of the power of the pulsed laser beam and the dimension of the modified spot.
Based on the input of the dimension of the modified spot, the magnitude of the power of the pulse laser beam that can be formed to this dimension is selected from the correlation storage means. The power adjusting means adjusts the magnitude of the power of the pulse laser light emitted from the laser light source so as to have the magnitude of the power selected by the power selecting means. Therefore, a modified spot having a desired size can be formed.

In the laser processing apparatus according to the present invention, a laser light source that emits a pulse laser beam having a pulse width of 1 μs or less, and a peak power density of a focal point of the pulse laser beam emitted from the laser light source is 1 × 10 ⁸ A condensing lens for condensing the pulsed laser light so as to be at least (W / cm ² ); a numerical aperture adjusting means for adjusting the numerical aperture of the optical system including the condensing lens; Means for adjusting the focal point of the pulsed laser light focused by the lens to the inside of the object to be processed, and moving means for relatively moving the focal point of the pulsed laser light along the line to cut the object to be processed A modified spot is formed inside the processing object by irradiating the processing object with a pulse laser beam of one pulse by adjusting the focal point inside the processing object, and the numerical aperture adjusting means Large numerical aperture to be adjusted And a correlation storage means for storing in advance a correlation between the size of the modified spot and a numerical aperture for selecting from the correlation storage means a size of a numerical aperture which can be formed in this dimension based on the input of the dimensions of the modified spot. Selecting means, and the numerical aperture adjusting means adjusts the numerical aperture of the optical system including the condensing lens so as to have the numerical aperture selected by the numerical aperture selecting means. .

According to the laser processing apparatus of the present invention, there is provided the correlation storage means for storing in advance the correlation between the size of the numerical aperture and the dimension of the modified spot. Based on the input of the dimension of the modified spot, the size of the numerical aperture that can be formed to this dimension is selected from the correlation storage means. The numerical aperture adjusting means adjusts the numerical aperture of the optical system including the condenser lens so as to have the numerical aperture selected by the numerical aperture selecting means. Therefore, a modified spot having a desired size can be formed.

In the laser processing apparatus according to the present invention, a laser light source that emits a pulse laser beam having a pulse width of 1 μs or less, and a peak power density of a focal point of the pulse laser beam emitted from the laser light source is 1 × 10 ⁸ (W / cm ² ) or more, and a plurality of condenser lenses for condensing the pulsed laser light, and lens selecting means capable of selecting a plurality of condenser lenses. Each optical system has a different numerical aperture, means for adjusting the focal point of the pulsed laser light focused by the focusing lens selected by the lens selecting means to the inside of the processing object, and cutting of the processing object Moving means for relatively moving the focal point of the pulsed laser light along the line, and irradiating the object with one pulse of pulsed laser light by adjusting the focal point inside the object to be processed. Processing object One modified spot is formed therein, and a correlation storage means in which the correlation between the size of the numerical aperture of the plurality of condensing lenses and the dimension of the modified spot is stored in advance. And a numerical aperture selecting means for selecting the size of the numerical aperture that can be formed to this size from the correlation storage means based on the numerical value. Selecting a focusing lens.

According to the laser processing apparatus of the present invention, the size of the numerical aperture that can be formed to this size is selected from the correlation storage means based on the input of the size of the modified spot. The lens selecting means selects a plurality of condensing lenses so as to have the size of the numerical aperture selected by the numerical aperture selecting means. Therefore, a modified spot having a desired size can be formed.

A laser processing apparatus according to the present invention comprises: a laser light source for emitting a pulse laser light having a pulse width of 1 μs or less; power adjusting means for adjusting the power of the pulse laser light emitted from the laser light source; A condensing lens for condensing the pulsed laser light so that the peak power density of the condensing point of the pulsed laser light emitted from the laser light source is 1 × 10 ⁸ (W / cm ² ) or more, and a condensing lens Numerical aperture adjusting means for adjusting the size of the numerical aperture of the optical system, including means for adjusting the focal point of the pulsed laser light focused by the focusing lens to the inside of the processing object, Moving means for relatively moving the focal point of the pulsed laser light along the line to be cut, and irradiating the object with one pulse of pulsed laser light by adjusting the focal point inside the object to be processed By machining One modified spot is formed inside the object, a set of the magnitude of the power of the pulsed laser beam adjusted by the power adjusting means, the set of the numerical aperture adjusted by the numerical aperture adjusting means, and the dimension of the modified spot. A correlation storage means in which a correlation between the power and the size of the power and the numerical aperture which can be formed in this dimension based on the input of the dimension of the modified spot is selected from the correlation storage means. And the power adjusting means and the numerical aperture adjusting means include a power magnitude of the pulse laser light emitted from the laser light source and a focusing lens so as to have the power and the numerical aperture selected by the set selecting means. The size of the numerical aperture of the optical system is adjusted.

According to the laser processing apparatus of the present invention, based on the input of the dimension of the modified spot, the combination of the magnitude of the power and the magnitude of the numerical aperture that can be formed to this dimension is selected from the correlation storage means. Then, the magnitude of the power of the pulse laser beam emitted from the laser light source and the magnitude of the numerical aperture of the optical system including the condensing lens are respectively set to the magnitude of the selected power and the magnitude of the numerical aperture. Adjust Therefore, a modified spot having a desired size can be formed. In addition, since the magnitude of the power and the magnitude of the numerical aperture are combined, it is possible to increase the types of sizes in which the dimensions of the modified spot can be controlled.

A laser processing apparatus according to the present invention comprises: a laser light source for emitting a pulse laser light having a pulse width of 1 μs or less; and a power adjusting means for adjusting the power of the pulse laser light emitted from the laser light source. And a plurality of condensing lenses for condensing the pulsed laser light so that the peak power density of the condensing point of the pulsed laser light emitted from the laser light source is 1 × 10 ⁸ (W / cm ² ) or more. Lens selecting means that can select the focusing lens of, the optical system including a plurality of focusing lenses have different numerical apertures,
Means for adjusting the focal point of the pulsed laser light condensed by the converging lens selected by the lens selecting means to the inside of the object to be processed, and condensing the pulsed laser light along a line to cut the object to be processed Moving means for relatively moving the point, and irradiating the processing object with one pulse of pulsed laser light by adjusting the focal point inside the processing object, thereby forming one modification inside the processing object. A correlation in which a spot is formed, and the correlation between the magnitude of the power of the pulsed laser beam adjusted by the power adjusting means and the set of the numerical apertures of the plurality of focusing lenses and the dimension of the modified spot is stored in advance. A relation storing means, and a set selecting means for selecting, from the correlation storing means, a set of power and numerical aperture size that can be formed in the dimension based on the input of the dimension of the modified spot, the power adjusting means and the lens The selecting means adjusts the magnitude of the power of the pulsed laser light emitted from the laser light source and selects a plurality of focusing lenses so as to have the power and the numerical aperture selected by the set selecting means. Features.

According to the laser processing apparatus of the present invention, based on the input of the dimension of the modified spot, a combination of the magnitude of the power and the magnitude of the numerical aperture that can be formed to this dimension is selected from the correlation storage means. The magnitude of the power of the pulse laser light emitted from the laser light source is adjusted and the plurality of focusing lenses are selected so that the magnitude of the selected power and the magnitude of the numerical aperture are obtained. Therefore, a modified spot having a desired size can be formed. In addition, since the magnitude of the power and the magnitude of the numerical aperture are combined, it is possible to increase the types of sizes in which the dimensions of the modified spot can be controlled.

In the laser processing apparatus according to the present invention, the display means for displaying the magnitude of the power selected by the power selection means, the display means for displaying the magnitude of the numerical aperture selected by the numerical aperture selection means, the group selection Display means for displaying the magnitude of the power and the magnitude of the numerical aperture of the set selected by the means may be provided. According to this, it is possible to know the power and the numerical aperture when the laser processing apparatus operates based on the input of the dimension of the modified spot.

In the laser processing apparatus according to the present invention, a plurality of modified spots can be formed inside the object along the line to be cut. A reforming area is defined by these reforming spots. The modified region is a crack region that is a region where a crack has occurred inside the processing object, a melt processing region that is a region that has been melt processed inside the processing object, and a region where the refractive index has changed inside the processing object. At least one of the refractive index change regions is included.

As an embodiment of the power adjusting means, there is an embodiment including at least one of an ND filter and a polarizing filter. In another embodiment, the laser light source includes an excitation laser, and the laser processing apparatus includes a drive current control unit that controls a drive current of the excitation laser. Thus, the magnitude of the power of the pulse laser light can be adjusted. Further, as an aspect of the numerical aperture adjusting means, for example, there is an aspect including at least one of a beam expander and an iris diaphragm.

In the laser processing method according to the present invention, the pulse laser light is focused on the inside of the object to be processed, and the object is irradiated with the pulsed laser beam, so that the line to be cut of the object to be processed is A first step of forming a modified region by multiphoton absorption along the inside of the object to be processed, adjusting the power of the pulsed laser light to be larger or smaller than the first step, and focusing the pulsed laser light By aligning the inside of the object to be processed and irradiating the object to be processed with pulsed laser light, another modified region due to multiphoton absorption is formed inside the object along another line to be cut of the object to be processed. And forming a second step.

Further, in the laser processing method according to the present invention, the focal point of the pulse laser light is adjusted to the inside of the object to be processed.
A first step of irradiating the processing object with a pulse laser beam to form a modified region by multiphoton absorption inside the processing object along a line to cut the processing object, and condensing the pulse laser beam Adjusting the numerical aperture of the optical system including the condensing lens to be larger or smaller than the first step,
In addition, by aligning the focal point of the pulsed laser light with the inside of the object to be processed and irradiating the object with the pulsed laser beam, the inside of the object to be machined is likely to be along the other to-be-cut line of the object to be machined. A second step of forming another modified region by photon absorption.

According to the laser processing method according to the present invention, for example, when there is a direction in which cutting is easy and a direction in which cutting is difficult due to the crystal orientation of the object to be processed, it is formed in a direction in which cutting is easy. The size of the modified spot forming the modified region is reduced, and the size of the modified spot forming another modified region formed in a direction in which cutting is difficult is increased. As a result, a flat cut surface can be obtained in a direction in which cutting is easy, and cutting can be performed in a direction in which cutting is difficult.

[0037]

Preferred embodiments of the present invention will be described below with reference to the drawings. In the laser processing method and the laser processing apparatus according to the present embodiment, the modified region is formed by multiphoton absorption. Multiphoton absorption is a phenomenon that occurs when the intensity of laser light is extremely increased. First, multiphoton absorption will be briefly described.

[0038] a band gap E photon energy hν than _G of absorption of the material is less optically clear. Therefore, a condition under which absorption occurs in the material is hv> E _G. However, even when optically transparent, increasing the intensity of the laser beam very Nhnyu> of E _G condition (n = 2, 3, 4, a, ...) absorbed in the material occurs. This phenomenon is called multiphoton absorption. In the case of a pulse wave, the intensity of the laser light is determined by the peak power density (W / cm ² ) at the focal point of the laser light. For example, when the peak power density is 1 × 10 ⁸ (W / cm ² ) or more, multiphoton Absorption occurs. The peak power density is obtained by (energy per pulse of laser light at a focal point) / (beam spot cross-sectional area of laser light × pulse width). In the case of a continuous wave, the intensity of the laser light is determined by the electric field intensity (W / cm ² ) at the focal point of the laser light.

The principle of laser processing according to the present embodiment utilizing such multiphoton absorption will be described with reference to FIGS. 1 is a plan view of the processing target 1 during laser processing, FIG. 2 is a cross-sectional view of the processing target 1 shown in FIG. 1 along line II-II, and FIG. 3 is a processing target after laser processing. Thing 1
FIG. 4 is a plan view of the workpiece 1 shown in FIG.
5 is a cross-sectional view of the processing target 1 shown in FIG. 3 along the line V-V, and FIG. 6 is a plan view of the processing target 1 shown in FIG.

As shown in FIG. 1 and FIG.
The surface 3 has a line 5 to be cut. The scheduled cutting line 5 is a virtual line extending linearly. In the laser processing according to the present embodiment, the laser light L is irradiated on the processing target 1 while adjusting the focal point P inside the processing target 1 under the condition where multiphoton absorption occurs, thereby forming the modified region 7. Note that the focal point is a point where the laser light L is focused.

The laser beam L is relatively moved along the line 5 to be cut (that is, along the direction of arrow A), so that the focal point P is moved along the line 5 to be cut. As a result, as shown in FIGS.
Are formed only inside the object 1 along the line 5 to be cut. The laser processing method according to the present embodiment does not form the modified region 7 by causing the processing target 1 to generate heat by absorbing the laser light L by the processing target 1. The modified region 7 is formed by transmitting the laser beam L to the processing target 1 and generating multiphoton absorption inside the processing target 1. Therefore, since the laser beam L is hardly absorbed by the surface 3 of the processing target 1, the surface 3 of the processing target 1 is not melted.

In the cutting of the object 1, if the starting point is located at a position to be cut, the object 1 is broken from the starting point, so that the object 1 can be cut with a relatively small force as shown in FIG. it can. Therefore, the surface 3 of the workpiece 1
The workpiece 1 can be cut without causing unnecessary cracks.

It should be noted that the following two types of cutting of the object to be processed starting from the modified region can be considered. One is a case where an artificial force is applied to the object to be processed after the modified area is formed, whereby the object to be processed is cracked starting from the modified area and the object to be processed is cut. This is, for example, cutting when the thickness of the processing target is large. An artificial force is applied when, for example, a bending stress or a shear stress is applied to a workpiece along a line to cut the workpiece, or a thermal stress is generated by giving a temperature difference to the workpiece. Or let them do that. The other is that, by forming the modified region, the fracture is naturally caused in the cross-sectional direction (thickness direction) of the object to be processed from the modified region as a starting point, resulting in the cutting of the object to be processed. It is. This is possible, for example, when the thickness of the object to be processed is small, even one modified area is provided,
When the thickness of the object to be processed is large, it becomes possible by forming a plurality of modified regions in the thickness direction. In addition, even if this cracks naturally, the crack does not advance to the surface on the portion where the modified region is not formed at the cutting position,
Since only the surface on the portion where the modified portion is formed can be cut, the cut can be controlled well. In recent years, the thickness of semiconductor wafers such as silicon wafers has tended to be reduced, and thus such a controllable cutting method is very effective.

The modified regions formed by multiphoton absorption in this embodiment include the following (1) to (3).

(1) In the case where the modified region is a crack region containing one or a plurality of cracks The laser beam is focused on the inside of the object to be processed (for example, a piezoelectric material made of glass or LiTaO ₃ ) by focusing. The electric field intensity at the light spot is 1 × 10 ⁸ (W / cm ² ) or more and the pulse width is 1
Irradiate under the condition of μs or less. The magnitude of this pulse width is
This is a condition under which a crack region can be formed only inside the object to be processed without causing unnecessary damage to the surface of the object to be processed while causing multiphoton absorption. As a result, a phenomenon called optical damage occurs due to multiphoton absorption inside the object to be processed. This optical damage induces thermal strain inside the object, thereby forming a crack region inside the object. The upper limit of the electric field strength is, for example, 1
× 10 ¹² (W / cm ² ). The pulse width is, for example, 1 ns to 2
00 ns is preferred. The formation of a crack region by multiphoton absorption is described in, for example, “Inside a Glass Substrate by Solid-State Laser Harmonics” on page 23 to page 28 of the 45th Meeting of the Laser Thermal Processing Society of Japan (December 1998). marking"
It is described in.

The present inventor has experimentally determined the relationship between the electric field strength and the crack size. The experimental conditions are as follows.

(A) Object to be processed: Pyrex glass (thickness: 700 μm) (B) Laser light source: Nd: YAG laser pumped by a semiconductor laser Wavelength: 1064 nm Laser beam spot cross section: 3.14 × 10 ⁻⁸ cm ² Oscillation form : Q switch pulse Repetition frequency: 100 kHz Pulse width: 30 ns Output: Output <1 mJ / pulse Laser beam quality: TEM ₀₀ Polarization characteristics: Linear polarization (C) Condensing lens Transmittance to laser beam wavelength: 60% (D) Processing Moving speed of the mounting table on which the object is mounted: 10
0 mm / sec The laser beam quality of TEM ₀₀ means that the laser beam has a high light-collecting property and can be focused to the wavelength of the laser beam.

FIG. 7 is a graph showing the results of the above experiment. The horizontal axis represents the peak power density. Since the laser light is a pulsed laser light, the electric field intensity is represented by the peak power density. The vertical axis indicates the size of a crack portion (crack spot) formed inside the object by one pulse of laser light. Crack spots gather to form a crack area. The size of the crack spot is the size of the portion having the maximum length in the shape of the crack spot. The data indicated by the black circles in the graph is the condenser lens (C)
Is 100 times and the numerical aperture (NA) is 0.80. On the other hand, data indicated by white circles in the graph are obtained when the magnification of the condenser lens (C) is 50 times and the numerical aperture (NA) is 0.55. From the peak power density of about 10 ¹¹ (W / cm ² ), it can be seen that a crack spot occurs inside the object to be processed, and the crack spot increases as the peak power density increases.

Next, in the laser processing according to the present embodiment, a mechanism of cutting an object to be processed by forming a crack region will be described with reference to FIGS. As shown in FIG. 8, the laser light L is irradiated on the processing target 1 by aligning the converging point P inside the processing target 1 under the condition where multiphoton absorption occurs, and a crack region is formed inside along the line to be cut. 9 is formed. The crack region 9 is a region including one or a plurality of cracks. Cracks further grow from the crack region 9 as shown in FIG. 9, and the cracks reach the front surface 3 and the back surface 21 of the processing object 1 as shown in FIG. 10, and as shown in FIG. The workpiece 1 is cut by breaking. Cracks that reach the front and back surfaces of the processing object may grow naturally, or may grow when a force is applied to the processing object.

(2) In the case where the modified region is a melt-processed region The laser beam is focused on the inside of the object to be processed (for example, a semiconductor material such as silicon), and the electric field intensity at the focused point is 1 × 10 ⁸ (W / cm ² ) or more and pulse width 1 μs
Irradiation is performed under the following conditions. Thereby, the inside of the object to be processed is locally heated by multiphoton absorption. By this heating, a melt processing area is formed inside the object to be processed. The melt-processed region means at least one of a region that has once been melted and re-solidified, a region in a molten state, and a region in a state of being re-solidified from melting. Further, the melt-processed region can also be referred to as a region where the phase has changed or a region where the crystal structure has changed. In addition, a melt-processed region can also be referred to as a region in which one structure is changed to another structure in a single crystal structure, an amorphous structure, or a polycrystalline structure. That is, for example, a region that has changed from a single crystal structure to an amorphous structure, a region that has changed from a single crystal structure to a polycrystalline structure, and a region that has changed from a single crystal structure to a structure that includes an amorphous structure and a polycrystalline structure. I do. When the object to be processed has a silicon single crystal structure, the melt processing region has, for example, an amorphous silicon structure. The upper limit of the electric field strength is, for example, 1 × 10 ¹² (W / cm ² ). The pulse width is preferably, for example, 1 ns to 200 ns.

The present inventor has confirmed through experiments that a melt processing region is formed inside a silicon wafer. The experimental conditions are as follows.

(A) Object to be processed: Silicon wafer (thickness: 350 μm, outer diameter: 4 inches) (B) Laser light source: Semiconductor laser pumped Nd: YAG laser Wavelength: 1064 nm Laser light spot cross section: 3.14 × 10 ^{− 8} cm ² oscillation form: Q switch pulse Repetition frequency: 100 kHz Pulse width: 30 ns Output: 20 μJ / pulse Laser light quality: TEM ₀₀ Polarization characteristics: linearly polarized light (C) Condensing lens Magnification: 50 times NA: 0.55 Laser Transmittance with respect to light wavelength: 60% (D) Moving speed of the mounting table on which the workpiece is mounted: 10
FIG. 12 is a view showing a photograph of a cross section of a part of the silicon wafer cut by the laser processing under the above conditions. A melt processing area 13 is formed inside the silicon wafer 11. The size in the thickness direction of the melt processing region formed under the above conditions is about 100 μm.

The fact that the melt processing region 13 is formed by multiphoton absorption will be described. FIG. 13 is a graph showing the relationship between the wavelength of the laser beam and the transmittance inside the silicon substrate. However, the reflection components on the front side and the back side of the silicon substrate are removed, and the transmittance is shown only inside. The thickness t of the silicon substrate is 50 μm, 100 μm, 200 μm,
The above relationship was shown for each of 500 μm and 1000 μm.

For example, the wavelength 106 of the Nd: YAG laser
At 4 nm, when the thickness of the silicon substrate is 500 μm or less, 80% or more of the laser light is transmitted inside the silicon substrate. Silicon wafer 11 shown in FIG.
Has a thickness of 350 μm, so that the melted region by multiphoton absorption is formed near the center of the silicon wafer, that is, at a portion 175 μm from the surface. The transmittance in this case is
Referring to a silicon wafer having a thickness of 200 μm, 90
% Or more, the laser light is slightly absorbed inside the silicon wafer 11 and almost all is transmitted. This means that the laser beam is absorbed inside the silicon wafer 11 and the melting region is not formed inside the silicon wafer 11 (that is, the melting region is formed by normal heating by the laser beam). It means that the processing region was formed by multiphoton absorption. The formation of the melt processing region by multiphoton absorption is described in, for example, “Evaluation of Silicon Processing Characteristics by Picosecond Pulsed Laser” on pages 72 to 73 of the 66th Annual Meeting of the Japan Welding Society (April 2000).
It is described in.

Incidentally, the silicon wafer is cracked in the cross-section direction starting from the melt processing region and reaches the front and back surfaces of the silicon wafer, resulting in cutting. The cracks reaching the front and back surfaces of the silicon wafer may grow spontaneously or may grow when a force is applied to the workpiece. The cracks naturally grow on the front and back surfaces of the silicon wafer from the melt processing area when the cracks grow from the area once re-solidified after melting, or when the cracks grow from the melted area. And at least one of the cases where cracks grow from a region in a state of being re-solidified from melting. In each case, the cut surface after cutting is shown in FIG.
As shown in FIG. 2, a melt processing region is formed only inside.
In the case of forming a melt-processed area inside the object to be processed, at the time of cutting, unnecessary cracks deviating from the line to be cut hardly occur, so that the cutting control is facilitated.

(3) When the Modified Area is a Refractive Index Change Area When the laser beam is focused on the inside of the object to be processed (eg, glass), the electric field intensity at the focused point is 1 × 10 ⁸ (W / c
Irradiation is performed under the condition of not less than m ² ) and a pulse width of 1 ns or less.
When the pulse width is extremely short and multi-photon absorption occurs inside the object, the energy due to multi-photon absorption does not convert to heat energy. Alternatively, a permanent structural change such as polarization orientation is induced to form a refractive index change region. The upper limit of the electric field strength is, for example, 1 × 10 ¹² (W / cm ² ). The pulse width is, for example, preferably 1 ns or less, and more preferably 1 ps or less. The formation of the refractive index change region by multiphoton absorption is
For example, the 42nd Laser Thermal Processing Research Group Transactions (1997)
Year. (November), pp. 105-111, "Formation of Photo-Induced Structure Inside Glass by Femtosecond Laser Irradiation".

As described above, according to the present embodiment, the modified region is formed by multiphoton absorption. In the present embodiment, by adjusting the magnitude of the power of the pulse laser light and the magnitude of the numerical aperture of the optical system including the condenser lens,
The size of the reforming spot is controlled. The modified spot is a modified portion formed by a one-pulse shot of the pulsed laser light (that is, one-pulse laser irradiation), and becomes a modified region by collecting the modified spots. The necessity of controlling the size of the modified spot will be described using a crack spot as an example.

If the crack spot is too large, the accuracy of cutting the object along the line to be cut is reduced, and the flatness of the cut surface is deteriorated. About this
This will be described with reference to FIG. FIG. 14 is a plan view of the processing target 1 when a crack spot is formed relatively large using the laser processing method according to the present embodiment. FIG. 15 is a sectional view taken along the line XV-XV on the cutting line 5 in FIG. 16, FIG. 17, and FIG.
XVI-XVI, XVII-XVII, orthogonal to the line 5 to be cut
It is sectional drawing cut | disconnected along XVIII-XVIII. As can be seen from these figures, if the crack spot 90 is too large, the variation in the size of the crack spot 90 increases. Therefore, as shown in FIG.
Accuracy of the cutting of the processing object 1 along the distance becomes worse. Also,
Since the unevenness of the cut surface 43 of the processing object 1 becomes large, the flatness of the cut surface 43 is deteriorated. On the other hand, as shown in FIG. 20, when the crack spot 90 is formed relatively small (for example, 20 μm or less) using the laser processing method according to the present embodiment, the crack spot 90 can be formed uniformly and the crack spot 90 can be formed. Can be suppressed from spreading in the direction deviating from the direction of the line to be cut. Therefore, as shown in FIG. 21, it is possible to improve the accuracy of cutting the workpiece 1 along the line to cut 5 and the flatness of the cut surface 43.

If the crack spot is too large as described above, it is impossible to perform a precise cutting along a line to be cut or a cutting to obtain a flat cut surface. However, if the crack spot is too small for the workpiece having a large thickness, it becomes difficult to cut the workpiece.

According to the present embodiment, the fact that the size of the crack spot can be controlled will be described. As shown in FIG. 7, when the peak power density is the same, the size of the crack spot when the magnification of the condensing lens is 100 and the NA is 0.8 is the crack when the magnification of the condensing lens is 50 and the NA is 0.55. It becomes smaller than the size of the spot. As described above, the peak power density is proportional to the energy per one pulse of the laser light, that is, the power of the pulsed laser light. Therefore, the same peak power density means that the power of the laser light is the same. Thus, when the laser beam power is the same and the beam spot cross-sectional area is the same,
As the numerical aperture of the condenser lens increases (decreases), the size of the crack spot can be controlled to decrease (increase).

Even if the numerical aperture of the condensing lens is the same,
If the power (peak power density) of the laser beam is reduced, the size of the crack spot can be controlled to be small, and if the power of the laser beam is increased, the size of the crack spot can be controlled to be large.

Therefore, as can be seen from the graph shown in FIG. 7, the size of the crack spot can be controlled to be small by increasing the numerical aperture of the condensing lens or reducing the power of the laser beam. Conversely, the size of the crack spot can be controlled to be large by reducing the numerical aperture of the condenser lens or increasing the power of the laser beam.

The dimensional control of the crack spot will be further described with reference to the drawings. The example shown in FIG. 22 is a cross-sectional view of the processing target object 1 in which the pulse laser light L is focused using a focusing lens having a predetermined numerical aperture. Area 4
Reference numeral 1 denotes a region where the electric field intensity is equal to or higher than a threshold value that causes multiphoton absorption by the laser irradiation. FIG.
FIG. 4 is a cross-sectional view of a crack spot 90 formed due to multiphoton absorption due to irradiation of the laser light L. On the other hand, FIG.
The example shown in FIG. 4 is a cross-sectional view of the processing target 1 in which the pulse laser beam L is focused using a focusing lens having a larger numerical aperture than the example shown in FIG. FIG. 25 is a cross-sectional view of a crack spot 90 formed due to the multiphoton absorption due to the irradiation of the laser light L. Crack spot 9
0 depends on the dimension of the region 41 in the thickness direction of the workpiece 1, and the width w of the crack spot 90 is
It depends on the dimension of the workpiece 1 in the direction perpendicular to the thickness direction. That is, the height h and the width w of the crack spot 90 can be reduced by reducing these dimensions of the region 41, and the height of the crack spot 90 can be reduced by increasing these dimensions.
h and width w can be increased. As is apparent from a comparison between FIG. 23 and FIG. 25, when the power of the laser beam is the same, the size of the height h and the width w of the crack spot 90 is increased by increasing (decreasing) the numerical aperture of the focusing lens. Can be controlled to be small (large).

Further, the example shown in FIG. 26 is a cross-sectional view of the object 1 in which the pulse laser beam L having a smaller power than the example shown in FIG. 22 is focused. In the example shown in FIG. 26, the area of the region 41 is smaller than the region 41 shown in FIG. FIG.
FIG. 4 is a cross-sectional view of a crack spot 90 formed due to multiphoton absorption due to irradiation of the laser light L. FIG.
27 and FIG. 27, when the numerical aperture of the condensing lens is the same, the power of the laser beam is reduced (increased).
Then, the size of the height h and the width w of the crack spot 90 can be controlled to be small (large).

Further, the example shown in FIG. 28 is a cross-sectional view of the workpiece 1 in which the pulse laser beam L having a smaller power than the example shown in FIG. 24 is focused. FIG. 29 is a cross-sectional view of a crack spot 90 formed due to multiphoton absorption due to the irradiation of the laser beam L. FIG. 23 and FIG. 29
As can be seen from the comparison of the above, when the numerical aperture of the condensing lens is increased (decreased) and the power of the laser beam is decreased (increased), the height h and width w of the crack spot 90 are controlled to be decreased (increased). it can.

The reason why the region 41 indicating the region where the electric field intensity is equal to or higher than the threshold value of the electric field intensity at which the crack spot can be formed is limited to the light converging point P and its vicinity is as follows. . In the present embodiment, since a laser light source with high beam quality is used, the light collecting property of the laser light is high, and the light can be collected to a wavelength of the laser light. For this reason, since the beam profile of this laser beam has a Gaussian distribution, the electric field intensity is strongest at the center of the beam,
The distribution is such that the intensity decreases as the distance from the center increases. In the process of actually condensing the laser light by the condensing lens, the laser light is basically condensed in a Gaussian distribution state. Therefore, the area 41
Is limited to the converging point P and its vicinity.

As described above, according to the present embodiment, the size of the crack spot can be controlled. The size of the crack spot is determined in consideration of the requirement for the degree of precise cutting, the requirement for the degree of flatness on the cut surface, and the thickness of the workpiece. Further, the size of the crack spot can be determined in consideration of the material of the object to be processed. According to this embodiment, since the dimensions of the modified spot can be controlled, for a processing object having a relatively small thickness, by reducing the modified spot, it is possible to cut precisely along the planned cutting line, and It is possible to perform cutting with good flatness of the cut surface. Also, by increasing the modification spot,
It is possible to cut even a processing object having a relatively large thickness.

Further, there are cases where the object to be processed has a direction in which cutting is easy and a direction in which cutting is difficult due to the crystal orientation of the object. In cutting such an object to be processed, for example, as shown in FIGS. 20 and 21, the size of a crack spot 90 formed in a direction in which cutting is easy is reduced. On the other hand, as shown in FIGS. 21 and 30, when the direction of the planned cutting line orthogonal to the planned cutting line 5 is a direction in which cutting is difficult, the size of the crack spot 90 formed in this direction is increased. As a result, a flat cut surface can be obtained in a direction in which cutting is easy, and cutting can be performed in a direction in which cutting is difficult.

The controllability of the dimension of the modified spot has been described in the case of the crack spot. However, the same can be said for the melting spot and the refractive index change spot. The power of the pulsed laser light can be represented by, for example, the energy per pulse (J) or the average power (W) which is a value obtained by multiplying the energy per pulse by the frequency of the laser light.

Next, a specific example of this embodiment will be described.

[First Example] A laser processing apparatus according to a first example of the present embodiment will be described. FIG. 31 is a schematic configuration diagram of the laser processing apparatus 400. Laser processing device 400
Is a laser light source 101 that generates a laser light L, a laser light source control unit 102 that controls the laser light source 101 to adjust the power and pulse width of the laser light L, and a laser light L emitted from the laser light source 101. And a power adjusting unit 401 for adjusting the power of the power supply.

The power adjustment unit 401 includes, for example, a plurality of NDs.
(neutral density) The filter and each ND filter are moved to a position perpendicular to the optical axis of the laser
Or a mechanism for moving the optical path out of the optical path. An ND filter is a filter that reduces the intensity of light without changing the relative spectral distribution of energy. The plurality of ND filters have different dimming rates. The power adjustment unit 401 includes a plurality of
The power of the laser light L emitted from the laser light source 101 is adjusted by any one of the ND filters or a combination thereof. Note that the laser light emitted from the laser light source 101 was obtained by changing the number of ND filters to be moved to a position perpendicular to the optical axis of the laser light L by the power adjusting unit 401 with the same dimming rate of the plurality of ND filters. The power of the laser light L can also be adjusted.

The power adjusting unit 401 rotates the polarization filter disposed perpendicular to the optical axis of the linearly polarized laser light L and the polarization filter by a desired angle about the optical axis of the laser light L. And a mechanism. By rotating the polarization filter by a desired angle about the optical axis in the power adjustment unit 401, the laser light source 10
The power of the laser light L emitted from 1 is adjusted.

The drive current of the semiconductor laser for excitation of the laser light source 101 is controlled by a laser light source control unit 102 which is an example of drive current control means, so that the laser light source 1
It is also possible to adjust the power of the laser light L emitted from 01. Therefore, the power of the laser light L can be adjusted by at least one of the power adjustment unit 401 and the laser light source control unit 102. If the dimension of the modified region can be set to a desired value only by adjusting the power of the laser beam L by the laser light source control unit 102, the power adjustment unit 40
1 is unnecessary. The power adjustment described above is performed by the operator of the laser processing apparatus by inputting the magnitude of the power to the overall control unit 127 described later using a keyboard or the like.

The laser processing apparatus 400 further includes a dichroic mirror 103 arranged so that the laser beam L whose power has been adjusted by the power adjusting unit 401 is incident thereon and the direction of the optical axis of the laser beam L is changed by 90 °. A lens selection mechanism 403 including a plurality of condenser lenses for condensing the laser light L reflected by the mirror 103 and a lens selection mechanism control unit 405 for controlling the lens selection mechanism 403 are provided.

The lens selecting mechanism 403 includes the condensing lens 10
5a, 105b, and 105c, and a support plate 407 that supports them. The numerical aperture of the optical system including the condenser lens 105a, the numerical aperture of the optical system including the condenser lens 105b, and the numerical aperture of the optical system including the condenser lens 105c are different from each other. The lens selection mechanism 403 rotates the support plate 407 based on a signal from the lens selection mechanism control unit 405, so that the condenser lenses 105a, 105b,
A desired condensing lens is arranged on the optical axis of the laser beam L from among the lenses 105c. That is, the lens selection mechanism 403 is a revolver type.

The number of condensing lenses attached to the lens selecting mechanism 403 is not limited to three, but may be another number. The operator of the laser processing apparatus inputs an instruction to select the size of the numerical aperture or any one of the condensing lenses 105a, 105b, and 105c to the overall control unit 127 described later using a keyboard or the like. The selection of the focusing lens, that is, the selection of the numerical aperture is performed.

The laser processing apparatus 400 further includes a processing object 1 to which the laser light L focused by the focusing lens arranged on the optical axis of the laser light L among the focusing lenses 105a to 105c is irradiated. And an X-axis stage 109 for moving the mounting table 107 in the X-axis direction.
A Y-axis stage 111 for moving the mounting table 107 in the Y-axis direction orthogonal to the X-axis direction; and a Z-axis stage for moving the mounting table 107 in the Z-axis direction orthogonal to the X-axis and Y-axis directions. 113 and these three stages 109, 111,
And a stage control unit 115 that controls the movement of the 113.

Since the Z-axis direction is a direction orthogonal to the surface 3 of the object 1, it is the direction of the depth of focus of the laser light L incident on the object 1. Therefore, by moving the Z-axis stage 113 in the Z-axis direction, the focal point P of the laser beam L can be adjusted inside the object 1 to be processed. The movement of the converging point P in the X (Y) axis direction is performed by moving the processing target 1 in the X (Y) axis direction by the X (Y) axis stage 109 (111). The X (Y) axis stage 109 (111) is an example of a moving unit.

The laser light source 101 is a Nd: YAG laser that generates a pulse laser beam. Other lasers that can be used for the laser light source 101 include Nd: YVO ₄ laser and Nd:
There are YLF laser and titanium sapphire laser. When forming a crack region or a melt processing region, an Nd: YAG laser, N
It is preferable to use a d: YVO ₄ laser and a Nd: YLF laser.
When forming the refractive index change region, it is preferable to use a titanium sapphire laser.

In the first example, a pulse laser beam is used for processing the processing object 1. However, a continuous wave laser beam may be used as long as multiphoton absorption can be caused. Condensing lens 10
5a to 105c are examples of the light collecting means. The Z-axis stage 113 is an example of a unit that adjusts the focal point of the laser beam to the inside of the processing target. Condensing lenses 105a to 105c
Is moved in the Z-axis direction, the focusing point of the laser beam can be adjusted to the inside of the object to be processed.

The laser processing apparatus 400 further includes the mounting table 1
07, an observation light source 117 that generates visible light to illuminate the processing target 1 with visible light, and a visible light arranged on the same optical axis as the dichroic mirror 103 and the condenser lens 105. Beam splitter 119
And. The dichroic mirror 103 is arranged between the beam splitter 119 and the condenser lens 105. The beam splitter 119 has a function of reflecting about half of visible light and transmitting the other half, and is arranged so as to change the direction of the optical axis of visible light by 90 °. About half of the visible light generated from the observation light source 117 is reflected by the beam splitter 119, and the reflected visible light is converted to the dichroic mirror 103 and the condenser lens 105.
To illuminate the surface 3 of the object 1 including the line 5 to be cut.

The laser processing device 400 further includes an image pickup device 12 arranged on the same optical axis as the beam splitter 119, the dichroic mirror 103, and the condensing lens 105.
1 and an imaging lens 123. As the imaging element 121, for example, there is a charge-coupled device (CCD) camera.
The reflected light of visible light illuminating the surface 3 including the line to be cut 5 and the like passes through the condenser lens 105, the dichroic mirror 103, and the beam splitter 119, is imaged by the imaging lens 123, and is imaged by the image sensor 121. And becomes image pickup data.

The laser processing apparatus 400 further includes an imaging data processing section 125 to which the imaging data output from the imaging element 121 is input, an overall control section 127 for controlling the entire laser processing apparatus 400, and a monitor 129. . The imaging data processing unit 125 calculates focus data for adjusting the focus of the visible light generated by the observation light source 117 on the surface 3 based on the imaging data. The stage controller 115 controls the movement of the Z-axis stage 113 based on the focus data so that the visible light is focused on the surface 3. Therefore, the imaging data processing unit 125 functions as an autofocus unit. The imaging data processing unit 125 calculates image data such as an enlarged image of the front surface 3 based on the imaging data. The image data is sent to the overall control unit 127, where various processes are performed, and the image data is sent to the monitor 129. As a result, an enlarged image or the like is displayed on the monitor 129.

The overall control unit 127 includes the stage control unit 1
15 and the image data from the imaging data processing unit 125, and the laser processing apparatus 102 controls the laser light source control unit 102, the observation light source 117, and the stage control unit 115 based on these data. 400 overall control. Therefore, the overall control unit 127 functions as a computer unit. The overall control unit 127 is electrically connected to the power adjustment unit 401. FIG.
Is omitted from this drawing. When the magnitude of the power is input to the overall control unit 127, the overall control unit 127 controls the power adjustment unit 401, whereby the power is adjusted.

FIG. 32 is a block diagram showing a part of an example of the overall control unit 127. The overall control unit 127 includes a dimension selection unit 411, a correlation storage unit 413, and an image creation unit 41.
5 is provided. The operator of the laser processing apparatus inputs the magnitude of the power of the pulsed laser light and the magnitude of the numerical aperture of the optical system including the condensing lens into the dimension selection unit 411 by using a keyboard or the like. In this example, instead of directly inputting the size of the numerical aperture, the condenser lenses 105a, 105b,
An input for selecting any one of 5c may be used. In this case, the converging lenses 105a and 105
The numerical apertures b and 105c are registered in advance, and the numerical aperture data of the optical system including the selected condensing lens is automatically input to the dimension selection unit 411.

The correlation storage unit 413 stores in advance the correlation between the set of the magnitude of the power and the numerical aperture of the pulse laser beam and the dimension of the modified spot. FIG.
Is an example of a table showing this correlation. In this example, in the column of numerical aperture, the condenser lenses 105a, 105b,
For each of 105c, the numerical aperture of the optical system including them is registered. In the column of power, the magnitude of the power of the pulse laser beam adjusted by the power adjustment unit 401 is registered. In the dimension column, the dimension of the modified spot formed by the combination of the power and the numerical aperture of the corresponding set is registered. For example, the power is 1.24 × 10 ¹¹ (W / cm ² )
The dimension of the modified spot formed when the numerical aperture is 0.55 is 120 μm. The data for this correlation is
For example, it can be obtained by performing the experiment described in FIGS. 22 to 29 before laser processing.

When the magnitude of the power and the magnitude of the numerical aperture are input to the dimension selection section 411, the dimension selection section 41
1 selects a set of the same values as these magnitudes from the correlation storage unit 413 and sends data of the dimensions corresponding to the set to the monitor 129. As a result, the monitor 129 displays the size of the reformed spot formed based on the magnitude of the input power and the magnitude of the numerical aperture. If there is no set of values equal to these magnitudes, the dimensional data corresponding to the closest set of values is sent to the monitor 129.

The data of the dimension corresponding to the set selected by the dimension selecting section 411 is transmitted from the dimension selecting section 411 to the image creating section 4.
15 The image creation unit 415 creates image data of the modified spot of this size based on the data of this size, and sends it to the monitor 129. Thereby, the monitor 129
Also displays an image of the modified spot. Therefore, the dimensions of the modified spot and the shape of the modified spot can be known before the laser processing.

It is also possible to fix the magnitude of the power and make the magnitude of the numerical aperture variable. The table in this case is shown in FIG.
As shown in FIG. For example, if the power is 1.49 × 10
The dimension of the modified spot formed when the numerical aperture is fixed at ¹¹ (W / cm ² ) and the numerical aperture is 0.55 is 150 μm. Further, the magnitude of the numerical aperture can be fixed and the magnitude of the power can be made variable. The table in this case is as shown in FIG. For example, the numerical aperture is fixed at 0.8 and the power is 1.1
The dimension of the modified spot formed at 9 × 10 ¹¹ (W / cm ² ) is 30 μm.

Next, a laser processing method according to a first example of the present embodiment will be described with reference to FIGS. FIG.
Is a flowchart for explaining this laser processing method. The processing object 1 is a silicon wafer.

First, the light absorption characteristics of the object 1 are measured by a spectrophotometer (not shown) or the like. Based on the measurement result, a laser light source 101 that generates a laser beam L having a wavelength that is transparent or has a small absorption with respect to the workpiece 1 is selected (S101). Next, the thickness of the workpiece 1 is measured. Based on the thickness measurement result and the refractive index of the object 1, the moving amount of the object 1 in the Z-axis direction is determined (S10).
3). This is because the focal point P of the laser light L is located inside the processing target 1, so that the processing target 1 based on the focal point of the laser light L located on the surface 3 of the processing target 1 is referred to. This is the amount of movement in the Z-axis direction. This movement amount is input to the overall control unit 127.

The object to be processed 1 is mounted on the mounting table 107 of the laser processing apparatus 400. Then, the processing target 1 is illuminated by generating visible light from the observation light source 117 (S10).
5). Workpiece 1 including illuminated scheduled cutting line 5
Is imaged by the image sensor 121. This imaging data is sent to the imaging data processing unit 125. On the basis of the image data, the image data processor 125 sets the observation light source 1
The focus data is calculated such that the focus of the visible light 17 is located on the surface 3 (S107).

The focus data is sent to the stage control unit 115. The stage control unit 115 moves the Z-axis stage 113 in the Z-axis direction based on the focus data (S
109). Thereby, the focus of the visible light of the observation light source 117 is located on the surface 3. Note that the imaging data processing unit 125
Calculates enlarged image data of the front surface 3 of the workpiece 1 including the line 5 to be cut based on the imaging data. The enlarged image data is transmitted to the monitor 129 via the overall control unit 127.
Is sent to the monitor 129 and the line 5 to be cut
A nearby enlarged image is displayed.

Step S10 is performed in advance by the general control unit 127.
The movement amount data determined in step 3 is input, and the movement amount data is sent to the stage control unit 115. The stage control unit 115 moves the processing target 1 in the Z-axis direction by the Z-axis stage 113 to a position where the focal point P of the laser light L is inside the processing target 1 based on the movement amount data ( S111).

Next, the power and the size of the numerical aperture are input to the overall control unit 127 as described above. The power of the laser beam L is adjusted by the power adjustment unit 401 based on the input power data. Based on the input numerical aperture data, the numerical aperture is determined by the lens selection mechanism controller 4.
Adjustment is performed by the lens selection mechanism 403 selecting a condensing lens via the line 05. These data are input to the dimension selection unit 411 (FIG. 32) of the overall control unit 127. As a result, the size of the fusion processing spot and the shape of the fusion processing spot formed inside the processing target object 1 by irradiation of the laser light L of one pulse are displayed on the monitor 129 (S112).

Next, a laser beam L is generated from the laser light source 101, and the laser beam L is irradiated to the line 5 to be cut on the surface 3 of the object 1. Since the focal point P of the laser beam L is located inside the processing target 1, the melt processing region is formed only inside the processing target 1. Then, the X-axis stage 109 and the Y-axis stage 1 are arranged along the line 5 to be cut.
11 is moved to form a melt-processed area inside the object 1 along the line 5 to be cut (S11).
3). Then, the object 1 is cut by bending the object 1 along the cutting line 5 (S11).
5). As a result, the workpiece 1 is divided into silicon chips.

The effect of the first example will be described. According to this,
The pulse laser beam L is applied to the line 5 to be cut under the condition that multiphoton absorption is caused and the focusing point P is set inside the object 1 to be processed. Then, by moving the X-axis stage 109 and the Y-axis stage 111, the focal point P is moved along the line 5 to be cut. This allows
A modified region (for example, a crack region, a melt processing region, a refractive index change region) is formed inside the processing target object 1 along the cut line 5. If there is any starting point at the cutting position of the object, the object can be cut by relatively small force. Therefore, the work 1 can be cut with a relatively small force by breaking the work 1 along the scheduled cutting line 5 with the modified region as a starting point. Thereby, the object 1 can be cut without generating unnecessary cracks off the cutting line 5 on the surface 3 of the object 1.

Further, according to the first example, the pulse laser beam L is cut on the line 5 to be cut under the condition that multi-photon absorption occurs in the object 1 and the focusing point P is set inside the object 1. Irradiation. Therefore, the pulse laser beam L is transmitted through the object 1 and the pulse laser beam L is hardly absorbed on the surface 3 of the object 1. Therefore, the surface 3 may be damaged such as melting due to the formation of the modified region. There is no.

As described above, according to the first example, it is possible to cut the object 1 without causing unnecessary cracks or melting off the cutting line 5 on the surface 3 of the object 1. it can. Therefore, when the processing target 1 is, for example, a semiconductor wafer, the semiconductor chip can be cut out of the semiconductor wafer without causing unnecessary cracks or melting of the semiconductor chip off the line to be cut. The same applies to a processing object having an electrode pattern formed on the surface, or a processing object having an electronic device formed on the surface, such as a glass substrate on which a display device such as a piezoelectric element wafer or a liquid crystal is formed. Therefore, according to the first example, it is possible to improve the yield of products (for example, display devices such as semiconductor chips, piezoelectric device chips, and liquid crystals) manufactured by cutting an object to be processed.

Further, according to the first example, the line 5 to be cut on the surface 3 of the workpiece 1 does not melt, so that the width of the line 5 to be cut (this width is, for example, a semiconductor chip in the case of a semiconductor wafer). This is the distance between the regions.). Thereby, the number of products manufactured from one processing target object 1 increases, and the productivity of the products can be improved.

Further, according to the first example, since the laser beam is used for cutting the object to be processed 1, more complicated processing can be performed than dicing using a diamond cutter. For example, as shown in FIG. 37, even if the line 5 to be cut has a complicated shape, cutting can be performed according to the first example. These effects are the same in the example described later.

[Second Example] Next, a second example of the present embodiment will be described focusing on differences from the first example. FIG. 38 is a schematic configuration diagram of the laser processing apparatus 500. Among the components of the laser processing device 500, the same components as those of the laser processing device 400 according to the first example shown in FIG.

The laser processing apparatus 500 includes a power adjusting unit 4
01 between the laser beam L and the dichroic mirror 103
A beam expander 501 is arranged on the optical axis of the optical disk. The beam expander 501 is variable in magnification, and is adjusted by the beam expander 501 so that the beam diameter of the laser light L is increased. Beam expander 501
Is an example of a numerical aperture adjusting means. Further, the laser processing apparatus 500 includes one condensing lens 105 instead of the lens selecting mechanism 403.

The operation of the laser processing apparatus 500 differs from the operation of the laser processing apparatus of the first example in the adjustment of the numerical aperture based on the numerical aperture inputted to the overall control unit 127. Hereinafter, this will be described. The overall control unit 127 is electrically connected to the beam expander 501.
FIG. 38 omits this illustration. When the size of the numerical aperture is input to the overall control unit 127, the overall control unit 1
27 controls the magnification of the beam expander 501 to be changed. Thereby, the magnification of the beam diameter of the laser beam L incident on the condenser lens 105 is adjusted. Therefore, even when the number of the condensing lens 105 is one, it is possible to adjust the numerical aperture of the optical system including the condensing lens 105 to be large. This will be described with reference to FIGS. 39 and 40.

FIG. 39 is a diagram showing the focusing of the laser beam L by the focusing lens 105 when the beam expander 501 is not provided. On the other hand, FIG. 40 is a diagram illustrating the focusing of the laser beam L by the focusing lens 105 when the beam expander 501 is provided. FIG.
40 and FIG. 40, as can be seen, the condensing lens 10 when the beam expander 501 is not disposed.
With reference to the numerical aperture of the optical system including 5, in the second example, the numerical aperture can be adjusted so as to increase.

[Third Example] Next, a third example of the present embodiment will be described focusing on differences from the previous examples. FIG. 41 is a schematic configuration diagram of the laser processing apparatus 600. Of the components of the laser processing apparatus 600, the same elements as those of the laser processing apparatus according to the above examples are denoted by the same reference numerals, and the description thereof will be omitted.

In the laser processing apparatus 600, an iris diaphragm 601 is arranged on the optical axis of the laser light L between the dichroic mirror 103 and the condenser lens 105, instead of the beam expander 501. By changing the size of the aperture of the iris diaphragm 601, the effective diameter of the condenser lens 105 is adjusted. The iris diaphragm 601 is an example of a numerical aperture adjusting unit. Also, the laser processing apparatus 600 controls an iris diaphragm control unit 603 for controlling the size of the aperture of the iris diaphragm 601.
Is provided. The iris diaphragm control unit 603 is controlled by the general control unit 127.

The operation of the laser processing apparatus 600 is different from the operation of the laser processing apparatus in the previous examples in that
The adjustment of the numerical aperture based on the size of the numerical aperture input to 27. The laser processing device 600 changes the size of the aperture of the iris diaphragm 601 based on the size of the input numerical aperture to adjust the effective diameter of the condenser lens 105 to be reduced. Thus, even when the number of the condensing lens 105 is one, it is possible to adjust the numerical aperture of the optical system including the condensing lens 105 to be small. This will be described with reference to FIGS. 42 and 43.

FIG. 42 is a diagram showing the focusing of the laser beam L by the focusing lens 105 when no iris diaphragm is arranged. On the other hand, FIG. 43 is a diagram illustrating focusing of the laser beam L by the focusing lens 105 when the iris diaphragm 601 is arranged. As can be seen by comparing FIGS. 42 and 43, when the numerical aperture of the optical system including the condensing lens 105 when the iris diaphragm is not disposed is set as a reference,
In the example, the numerical aperture can be adjusted to be small.

Next, a modification of this embodiment will be described. FIG. 44 is a block diagram of an overall control unit 127 provided in a modified example of the laser processing apparatus of the present embodiment. Overall control unit 1
27 includes a power selection unit 417 and a correlation storage unit 413. Correlation data shown in FIG. 35 is stored in the correlation storage unit 413 in advance. The operator of the laser processing apparatus inputs a desired dimension of the modified spot to the power selection unit 417 using a keyboard or the like. The dimensions of the reforming spot are determined in consideration of the thickness, material, and the like of the workpiece.
In response to this input, the power selection unit 417 selects a power corresponding to a dimension having the same value as this dimension from the correlation storage unit 413, and sends data of the power to the power adjustment unit 401. Therefore, it is possible to form a modified spot having a desired size by performing laser processing with a laser processing apparatus adjusted to the magnitude of the power. The power magnitude data is also sent to the monitor 129, and the power magnitude is displayed. In this example, the numerical aperture is fixed and the power is variable. When the dimension having the same value as the input dimension is not stored in the correlation storage unit 413, the power data corresponding to the dimension having the closest value is stored in the power adjustment unit 401.
And sent to the monitor 129. This is the same in the modified examples described below.

FIG. 45 is a block diagram of an overall control unit 127 provided in another modification of the laser processing apparatus of the present embodiment. The overall control unit 127 includes a numerical aperture selection unit 419 and a correlation storage unit 413. The difference from the modification of FIG. 44 is that the numerical aperture is selected instead of the power. The data shown in FIG. 34 is stored in the correlation storage unit 413 in advance. The operator of the laser processing apparatus inputs a desired size of the modified spot to the numerical aperture selection unit 419 using a keyboard or the like. Accordingly, the numerical aperture selection unit 419 selects a numerical aperture corresponding to a dimension having the same value as this dimension from the correlation storage unit 413, and transmits the numerical aperture data to the lens selection mechanism control unit 405, the beam expander 501, or This is sent to the iris diaphragm control unit 603. Therefore, it is possible to form a modified spot having a desired size by performing laser processing with a laser processing apparatus adjusted to the size of the numerical aperture. The data of the numerical aperture is also sent to the monitor 129, and the numerical aperture is displayed. In this example, the power is fixed and the numerical aperture is variable.

FIG. 46 is a block diagram of an overall control unit 127 provided in still another modification of the laser processing apparatus of the present embodiment. The overall control unit 127 includes a group selection unit 421 and a correlation storage unit 413. The difference from the examples of FIGS. 44 and 45 is that both power and numerical aperture are selected. In the correlation storage unit 413, data of the correlation between the set of the power and the numerical aperture of FIG. 33 and the dimensions is stored in advance. The operator of the laser processing apparatus inputs a desired dimension of the modified spot to the group selecting section 421 using a keyboard or the like. As a result, the pair selection unit 421 sets the correlation storage unit 4
13, a set of power and numerical aperture corresponding to a dimension having the same value as this dimension is selected. The data of the selected set of power is sent to the power adjustment unit 401. On the other hand, data on the selected set of numerical apertures is sent to the lens selection mechanism control unit 405, the beam expander 501, or the iris diaphragm control unit 603. Therefore, by laser processing with a laser processing device adjusted to the magnitude of the power and numerical aperture of this set,
It is possible to form a modified spot having a desired size. The data of the power and numerical aperture size of this set is also sent to the monitor 129, and the power and numerical aperture size are displayed.

According to these modifications, the size of the modified spot can be controlled. Therefore, by reducing the size of the modified spot, it is possible to cut precisely along the line to cut the object to be processed, and to obtain a flat cut surface. When the thickness of the processing target is large, the processing target can be cut by increasing the dimension of the modified spot.

[0115]

According to the laser processing apparatus and the laser processing method according to the present invention, the object to be processed can be cut without melting or cracking off the line to be cut on the surface of the object to be processed. Therefore, the yield and productivity of a product (for example, a display device such as a semiconductor chip, a piezoelectric device chip, or a liquid crystal) manufactured by cutting an object to be processed can be improved.

According to the laser processing apparatus and the laser processing method according to the present invention, the dimensions of the modified spot can be controlled. Therefore, the object to be processed can be cut precisely along the line to be cut, and a flat cut surface can be obtained.

According to the laser processing apparatus of the present invention, the size of the modified spot formed under these conditions is displayed on the display means based on at least one of the power and the numerical aperture. Will be displayed. Therefore, the dimensions of the modified spot can be known before the laser processing.

According to the laser processing apparatus of the present invention, at least one of the magnitude of the power and the magnitude of the numerical aperture is adjusted based on the input of the dimension of the modified spot so that the modified spot has this dimension. Adjust one. Therefore, a modified spot having a desired size can be formed.

[Brief description of the drawings]

FIG. 1 is a plan view of an object to be processed during laser processing by a laser processing method according to an embodiment.

FIG. 2 is a cross-sectional view of the object illustrated in FIG. 1 taken along the line II-II.

FIG. 3 is a plan view of a processing target after laser processing by the laser processing method according to the embodiment.

FIG. 4 is a cross-sectional view of the object shown in FIG. 3, taken along line IV-IV.

FIG. 5 is a cross-sectional view of the processing target object shown in FIG. 3 taken along line VV.

FIG. 6 is a plan view of a processing object cut by the laser processing method according to the embodiment.

FIG. 7 is a graph showing a relationship between electric field intensity and crack size in the laser processing method according to the embodiment.

FIG. 8 is a sectional view of an object to be processed in a first step of the laser processing method according to the embodiment.

FIG. 9 is a cross-sectional view of a processing target in a second step of the laser processing method according to the embodiment.

FIG. 10 is a sectional view of an object to be processed in a third step of the laser processing method according to the embodiment.

FIG. 11 is a sectional view of an object to be processed in a fourth step of the laser processing method according to the embodiment.

FIG. 12 is a diagram showing a photograph of a cross section of a part of the silicon wafer cut by the laser processing method according to the embodiment.

FIG. 13 is a graph showing the relationship between the wavelength of laser light and the transmittance inside a silicon substrate in the laser processing method according to the present embodiment.

FIG. 14 is a plan view of a processing target when a crack spot is formed relatively large using the laser processing method according to the present embodiment.

15 is a cross-sectional view taken along line XV-XV on the line to be cut shown in FIG. 14;

16 is an XVI-axis orthogonal to the line to be cut shown in FIG.
It is sectional drawing cut | disconnected along XVI.

17 is an XVII orthogonal to the line to be cut shown in FIG.
It is sectional drawing cut | disconnected along -XVII.

18 is an XVII orthogonal to the line to be cut shown in FIG.
It is sectional drawing cut | disconnected along I-XVIII.

19 is a plan view of the object shown in FIG. 14 cut along a line to cut.

FIG. 20 is a cross-sectional view of an object to be processed along a line to be cut when a crack spot is formed relatively small using the laser processing method according to the present embodiment.

21 is a plan view of the object shown in FIG. 20 cut along a line to cut.

FIG. 22 is a cross-sectional view of a processing object showing a state in which pulse laser light is focused inside the processing object using a condensing lens having a predetermined numerical aperture.

23 is a cross-sectional view of a processing target including a crack spot formed due to multiphoton absorption due to laser light irradiation shown in FIG.

FIG. 24 is a cross-sectional view of a processing object when a condensing lens having a larger numerical aperture than the example shown in FIG. 22 is used.

25 is a cross-sectional view of a processing target including a crack spot formed due to multiphoton absorption due to laser light irradiation shown in FIG.

26 is a cross-sectional view of an object to be processed when a pulse laser beam having a smaller power than the example shown in FIG. 22 is used.

27 is a cross-sectional view of a processing target including a crack spot formed due to multiphoton absorption due to laser light irradiation shown in FIG. 26.

FIG. 28 is a cross-sectional view of a processing target when a pulse laser beam having a smaller power than the example shown in FIG. 24 is used.

29 is a cross-sectional view of a processing target including a crack spot formed due to multiphoton absorption due to laser light irradiation shown in FIG.

30. XXX- orthogonal to the line to be cut shown in FIG.
It is sectional drawing cut | disconnected along XXX.

FIG. 31 is a schematic configuration diagram of a laser processing apparatus according to a first example of the present embodiment.

FIG. 32 is a block diagram illustrating a part of an example of an overall control unit provided in the laser processing apparatus according to the embodiment.

FIG. 33 is a diagram illustrating an example of a table of a correlation storage unit included in the overall control unit of the laser processing apparatus according to the embodiment.

FIG. 34 is a diagram showing another example of the table of the correlation storage unit included in the overall control unit of the laser processing apparatus according to the embodiment.

FIG. 35 is a diagram showing still another example of the table of the correlation storage unit included in the overall control unit of the laser processing apparatus according to the embodiment.

FIG. 36 is a flowchart illustrating a laser processing method according to a first example of the embodiment.

FIG. 37 is a plan view of a processing object for explaining a pattern that can be cut by the laser processing method according to the first example of the embodiment.

FIG. 38 is a schematic configuration diagram of a laser processing apparatus according to a second example of the present embodiment.

FIG. 39 is a diagram illustrating focusing of laser light by a focusing lens when no beam expander is provided.

FIG. 40 is a diagram showing the focusing of laser light by a focusing lens when a beam expander is arranged.

FIG. 41 is a schematic configuration diagram of a laser processing apparatus according to a third example of the present embodiment.

FIG. 42 is a diagram illustrating focusing of laser light by a focusing lens when no iris diaphragm is arranged.

FIG. 43 is a diagram illustrating focusing of laser light by a focusing lens when an iris diaphragm is arranged.

FIG. 44 is a block diagram of an example of an overall control unit provided in a modified example of the laser processing apparatus of the present embodiment.

FIG. 45 is a block diagram of another example of the overall control unit provided in a modified example of the laser processing apparatus of the present embodiment.

FIG. 46 is a block diagram of still another example of the overall control unit provided in a modification of the laser processing apparatus of the present embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Processing object, 3 ... Surface, 5 ... Cut line, 7 ... Modification area, 9 ... Crack area, 1
1 ... silicon wafer, 13 ... melt processing area, 4
1 ... region, 43 ... cut surface, 90 ... crack spot, 101 ... laser light source, 105, 105a,
105b, 105c: Condensing lens, 109: X
Axis stage, 111 ... Y axis stage, 113 ... Z
Axis stage, 400 ... laser processing device, 401 ...
-Power adjustment unit, 403: Lens selection mechanism, 411
... Dimension selection unit, 413, correlation storage unit, 41
5 ... image creation unit, 417 ... power selection unit, 41
9 ... numerical aperture selection unit, 421 ... group selection unit, 500
・ ・ ・ Laser processing equipment, 501 ・ ・ ・ Beam expander, 600 ・ ・ ・ Laser processing equipment, 601 ・ ・ ・ Iris diaphragm, P ・ ・ ・ Condensing point

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) B23K 26/06 B23K 26/06 Z C03B 33/08 C03B 33/08 (72) Inventor Naoki Uchiyama Ichinomachi, Hamamatsu-shi, Shizuoka 1126 No. 1 in Hamamatsu Photonics Co., Ltd. (72) Inventor Toshimitsu Wakuda 1126 No. 1-cho, Hamamatsu-shi, Shizuoka Pref. 4G015 FA06 FB02 FB03 FC02 FC10 FC14

Claims (17)

[Claims] 1. A laser light source for emitting a pulse laser beam having a pulse width of 1 μs or less, and a power level of the pulse laser beam emitted from the laser light source is adjusted based on an input of a power level of the pulse laser beam. Power adjusting means for focusing, and focusing means for focusing the pulsed laser light so that the peak power density of the focused point of the pulsed laser light emitted from the laser light source is 1 × 10 ⁸ (W / cm ² ) or more Means for adjusting the focal point of the pulsed laser light focused by the focusing means to the inside of the object to be processed; and Moving means for moving the laser beam to the processing object, and irradiating the processing object with one pulse of pulsed laser light with the converging point adjusted to the inside of the processing object, whereby
Two modified spots are formed, a correlation storage unit that stores in advance a correlation between the magnitude of the power of the pulse laser beam adjusted by the power adjustment unit and the dimension of the modified spot, and the input pulsed laser beam. Size selecting means for selecting the size of the modified spot formed with the power of this magnitude from the correlation storage means, based on the magnitude of the power of the size, and the dimension of the modified spot selected by the size selecting means A laser processing apparatus, comprising: dimension display means for displaying 2. A laser light source for emitting a pulse laser beam having a pulse width of 1 μs or less, and a peak power density of a focal point of the pulse laser beam emitted from the laser light source is 1 × 10 ⁸ (W / cm ² ). A condensing lens for condensing the pulse laser light as described above, and a numerical aperture adjusting means for adjusting the numerical aperture of the optical system including the condensing lens based on the input of the numerical aperture Means for adjusting the focal point of the pulsed laser light focused by the focusing lens to the inside of the object to be processed; and relative the focal point of the pulsed laser light along a line to be cut of the object to be processed. A moving means for moving the object, and irradiating the processing object with one pulse of pulsed laser light with the converging point in the inside, whereby 1
Two modification spots are formed, a correlation storage unit in which a correlation between the size of the numerical aperture adjusted by the numerical aperture adjustment unit and the size of the modification spot is stored in advance, and the size of the input numerical aperture Dimension selecting means for selecting the dimension of the modified spot formed with the numerical aperture of this size from the correlation storage means based on the following: Dimension for displaying the dimension of the modified spot selected by the dimension selecting means A laser processing apparatus comprising: a display unit. 3. A laser light source for emitting pulse laser light having a pulse width of 1 μs or less, and a peak power density of a focal point of the pulse laser light emitted from the laser light source is 1 × 10 ⁸ (W / cm ² ). An optical system including a plurality of condensing lenses for condensing the pulsed laser light and selecting the plurality of condensing lenses as described above; and an optical system including the plurality of condensing lenses. Means for adjusting the focal point of the pulsed laser beam focused by the focusing lens selected by the lens selecting means to the inside of the processing object, and a line to cut the processing object Moving means for relatively moving the focal point of the pulsed laser light along, and irradiating the processing object with one pulse of the pulsed laser light by adjusting the focal point to the inside thereof, 1 inside
Correlation modification means in which a correlation between the size of the numerical aperture of the optical system including the plurality of condenser lenses and the dimension of the modification spot is stored in advance, and the selected condensing spot is formed. Based on the size of the numerical aperture of the optical system including the lens for use, a dimension selecting means for selecting the dimension of the modified spot formed with the numerical aperture of this size from the correlation storage means, and A laser processing apparatus, comprising: dimension display means for displaying a dimension of a selected modified spot. 4. A laser light source that emits a pulse laser beam having a pulse width of 1 μs or less, and a power level of the pulse laser beam emitted from the laser light source is adjusted based on an input of a power level of the pulse laser beam. Power adjusting means for converging the pulse laser light so that the peak power density of the converging point of the pulse laser light emitted from the laser light source is 1 × 10 ⁸ (W / cm ² ) or more. A lens; a numerical aperture adjusting means for adjusting a numerical aperture of the optical system including the condensing lens based on an input of the numerical aperture; and a pulsed laser beam condensed by the condensing lens Means for adjusting the focal point of the laser beam to the inside of the object to be processed; and moving means for relatively moving the focal point of the pulsed laser light along the line to cut the object to be processed. Adjust the light spot By irradiating one pulse of the pulsed laser light to the processing object, 1 to the internal
And a set of the magnitude of the power of the pulsed laser beam adjusted by the power adjusting means and the set of the numerical aperture adjusted by the numerical aperture adjusting means and the size of the modified spot. A correlation storage means for storing the relationship in advance; and a dimension of the modified spot formed with these magnitudes based on the magnitude of the power of the inputted pulsed laser beam and the magnitude of the inputted numerical aperture. A laser processing apparatus, comprising: a dimension selecting unit that selects from the correlation storage unit; and a dimension displaying unit that displays a dimension of the modified spot selected by the dimension selecting unit. 5. A laser light source for emitting a pulse laser beam having a pulse width of 1 μs or less, and adjusting the power of the pulse laser beam emitted from the laser light source based on an input of the power of the pulse laser beam. Power adjusting means for converging the pulse laser light so that the peak power density of the converging point of the pulse laser light emitted from the laser light source is 1 × 10 ⁸ (W / cm ² ) or more. Lens selecting means including a plurality of lenses and capable of selecting the plurality of condensing lenses, wherein the optical systems including the plurality of condensing lenses have different numerical apertures, and are selected by the lens selecting means. Means for adjusting the focal point of the pulsed laser light focused by the focusing lens to the inside of the object to be processed, and a relative point of focus of the pulsed laser light along a line to be cut of the object to be processed. Moving means for moving the object to be processed, and irradiating the object to be processed with one pulse of pulsed laser light with the converging point adjusted to the inside, whereby the inside of the object is
Two modified spots are formed, a set of the magnitude of the power of the pulsed laser light adjusted by the power adjusting means, the numerical aperture of the optical system including the plurality of condensing lenses, and the dimension of the modified spot. Correlation storage means pre-stored the correlation with, based on the magnitude of the power of the input pulsed laser light and the magnitude of the numerical aperture of the optical system including the selected condensing lens, Dimension selecting means for selecting the dimension of the modified spot formed with these sizes from the correlation storage means, and dimension displaying means for displaying the dimension of the modified spot selected by the dimension selecting means. , Laser processing equipment. 6. An image creating means for creating an image of a modified spot having a dimension selected by the dimension selecting means, and an image display means for displaying an image created by the image creating means. The laser processing apparatus according to any one of claims 1 to 5. 7. A laser light source for emitting a pulse laser beam having a pulse width of 1 μs or less, power adjusting means for adjusting the magnitude of power of the pulse laser beam emitted from the laser light source, and a laser beam emitted from the laser light source. Focusing means for focusing the pulsed laser light so that the peak power density of the focused point of the pulsed laser light is 1 × 10 ⁸ (W / cm ² ) or more; and pulses focused by the focusing means Means for adjusting the focal point of the laser light to the inside of the object to be processed; and moving means for relatively moving the focal point of the pulsed laser light along a line to cut the object to be processed; By irradiating the object with one pulse of pulsed laser light with the focusing point set at
Correlation modifying means in which a correlation between the magnitude of the power of the pulsed laser beam adjusted by the power adjusting means and the dimension of the modified spot is stored in advance, and the dimension of the modified spot is input. And a power selecting unit that selects the magnitude of the power of the pulse laser light that can be formed to this size from the correlation storage unit, based on the above, wherein the power adjusting unit has a power of the power selected by the power selecting unit. A laser processing apparatus that adjusts the magnitude of the power of the pulsed laser light emitted from the laser light source so as to have a magnitude. 8. A laser light source that emits a pulse laser beam having a pulse width of 1 μs or less, and a peak power density of a focal point of the pulse laser beam emitted from the laser light source is 1 × 10 ⁸ (W / cm ² ). A condensing lens for condensing the pulsed laser light as described above; a numerical aperture adjusting means for adjusting the size of the numerical aperture of the optical system including the condensing lens; Means for adjusting the focal point of the pulsed laser light to the inside of the object to be processed; and moving means for relatively moving the focal point of the pulsed laser light along a line to cut the object to be processed. By irradiating the object with a pulse laser beam of one pulse with the converging point adjusted inside,
Two modified spots are formed, a correlation storage unit storing in advance a correlation between the size of the numerical aperture adjusted by the numerical aperture adjusting unit and the dimension of the modified spot, and based on the input of the dimension of the modified spot. And a numerical aperture selecting means for selecting the size of the numerical aperture that can be formed in this dimension from the correlation storage means. The numerical aperture adjusting means includes a numerical aperture selected by the numerical aperture selecting means. A laser processing apparatus for adjusting the size of the numerical aperture of an optical system including the condensing lens so that 9. A laser light source for emitting a pulse laser beam having a pulse width of 1 μs or less, and a peak power density of a focal point of the pulse laser beam emitted from the laser light source is 1 × 10 ⁸ (W / cm ² ). An optical system including a plurality of condensing lenses for condensing the pulsed laser light and selecting the plurality of condensing lenses as described above; and an optical system including the plurality of condensing lenses. Each has a different numerical aperture, a means for adjusting the focal point of the pulsed laser beam focused by the focusing lens selected by the lens selecting means to the inside of the processing object, and the cutting of the processing object Moving means for relatively moving the focal point of the pulsed laser light along the line, and irradiating the processing object with one pulse of the pulsed laser light by adjusting the focal point to the inside thereof, The inside 1
Two modified spots are formed, and a correlation storage unit in which a correlation between the size of the numerical aperture of the plurality of condenser lenses and the dimension of the modified spot is stored in advance, based on the input of the dimension of the modified spot. And a numerical aperture selecting means for selecting the size of the numerical aperture that can be formed in this dimension from the correlation storage means. The lens selecting means has the numerical aperture selected by the numerical aperture selecting means. A laser processing apparatus for selecting the plurality of focusing lenses as described above. 10. A laser light source for emitting a pulsed laser beam having a pulse width of 1 μs or less; power adjusting means for adjusting the magnitude of power of the pulsed laser beam emitted from the laser light source; A condensing lens for condensing the pulsed laser beam so that the peak power density of the condensed point of the pulsed laser beam is 1 × 10 ⁸ (W / cm ² ) or more, and an optical system including the condensing lens Numerical aperture adjusting means for adjusting the size of the numerical aperture, means for adjusting the focal point of the pulsed laser light focused by the focusing lens to the inside of the processing object, and cutting of the processing object Moving means for relatively moving the focal point of the pulsed laser light along the line, and irradiating the processing object with one pulse of the pulsed laser light by adjusting the focal point to the inside thereof, The inside 1
And a set of the magnitude of the power of the pulsed laser beam adjusted by the power adjusting means and the set of the numerical aperture adjusted by the numerical aperture adjusting means and the size of the modified spot. A correlation storage unit in which the relationship is stored in advance; and a pair selection unit for selecting a set of power and numerical aperture size that can be formed in this size from the correlation storage unit based on input of a dimension of the modified spot; The power adjustment means and the numerical aperture adjustment means, the magnitude of the power of the pulse laser light emitted from the laser light source so as to be the power and the numerical aperture selected by the set selection means, and A laser processing apparatus for adjusting the numerical aperture of an optical system including a condensing lens. 11. A laser light source for emitting a pulse laser beam having a pulse width of 1 μs or less; power adjusting means for adjusting the magnitude of the power of the pulse laser beam emitted from the laser light source; And a plurality of condensing lenses for condensing the pulsed laser light so that the peak power density at the converging point of the pulsed laser light is 1 × 10 ⁸ (W / cm ² ) or more. An optical system including the plurality of focusing lenses, each having a different numerical aperture, and a pulse laser focused by the focusing lens selected by the lens selecting unit. Means for adjusting the focal point of light to the inside of the object to be processed; and moving means for relatively moving the focal point of the pulsed laser light along a line to cut the object to be processed; By irradiating the pulse laser beam of one pulse with its focusing point on the workpiece, the internal 1
And a correlation between a set of the magnitude of the power of the pulsed laser beam adjusted by the power adjusting means and the magnitude of the numerical aperture of the plurality of focusing lenses and the dimension of the modified spot. Correlation storage means in which is stored in advance; and a set selection means for selecting, from the correlation storage means, a set of power and numerical aperture size that can be formed in this dimension based on the input of the dimension of the modified spot, The power adjusting unit and the lens selecting unit are configured to adjust the magnitude of the power of the pulsed laser light emitted from the laser light source so as to have the magnitude of the power and the numerical aperture selected by the set selecting unit, and A laser processing device that selects a plurality of focusing lenses. 12. The apparatus according to claim 7, further comprising a display unit for displaying the magnitude of the power selected by said power selection unit.
The laser processing apparatus according to the above. 13. A display unit for displaying a size of a numerical aperture selected by the numerical aperture selection unit.
Or the laser processing apparatus according to 9. 14. The laser processing apparatus according to claim 10, further comprising display means for displaying the magnitude of the power and the magnitude of the numerical aperture of the set selected by said set selecting means. 15. A modified region is defined by the plurality of modified spots formed inside the processing object along the line to be cut, and the modified region has a crack in the interior. The crack region which is a region, including at least one of a refractive index change region which is a region where a refractive index has changed in the inside and a melt processing region which is a region where a melt process has been performed in the inside, The laser processing apparatus according to any one of the above. 16. A method according to claim 1, further comprising: irradiating the processing object with the pulsed laser beam while adjusting a focal point of the pulse laser light to the inside of the processing object, thereby cutting the processing object along a line to cut the processing object. A first step of forming a modified region by multiphoton absorption inside the object; adjusting the power of the pulsed laser light so as to be larger or smaller than that of the first step; By irradiating the object to be processed with pulsed laser light in accordance with the inside of the object, another modification by multiphoton absorption is performed inside the object along another line to be cut of the object. A second step of forming a region, comprising: 17. A method according to claim 1, further comprising: irradiating the processing target with the pulsed laser beam while adjusting a focal point of the pulse laser light to the inside of the processing target, thereby cutting the processing target along a cutting line of the processing target. A first step of forming a modified region by multiphoton absorption inside the object; and adjusting the numerical aperture of an optical system including a condensing lens for condensing the pulsed laser light so as to be larger or smaller than the first step. By aligning the focal point of the pulsed laser light with the inside of the object to be processed, and irradiating the object to be processed with the pulsed laser beam, the processing is performed along another line to be cut of the object to be processed. A second step of forming another modified region by multiphoton absorption inside the object.