JP2018052814A - Modified layer forming method and modified layer forming device for brittle material substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a modified layer forming method and a modified layer forming device for a brittle material substrate, using an aberration laser beam in which laser beams converge with aberration, in order to divide the brittle material substrate.SOLUTION: Laser beams L1, including the burst of a pulse laser beam, are passed through an aberration generation lens 4c to generate aberration, and made into an aberration laser beam L2. The aberration laser beam L2 is used for scanning along a scheduled division line S of a brittle material substrate W to form a modified layer, thereby dividing the brittle material substrate along the scheduled division line.SELECTED DRAWING: Figure 3

Description

The present invention relates to a modified layer forming method and a modified layer forming apparatus for a brittle material substrate such as glass.

  Conventionally, a laser processing technique called “stealth dicing” in which an internal modified layer is formed by irradiating a transparent (transparent) laser beam with respect to a substrate has been used (see Patent Document 1). . In this laser processing technology, a modified layer is formed by focusing on the inside of the substrate in the region to be divided and irradiating with a pulsed laser beam and performing this continuously along the street (scheduled division line). Form. And it divides | segments by applying external force along the modified layer in which intensity | strength fell.

In recent years, as a result of research and development of laser beams for splitting with pulse widths (pulse durations) of nanoseconds (ns) and picoseconds (ps), burst trains (burst pulse light) ) Is also used, which is a laser processing technique that irradiates a cutting laser beam called “burst mode” and performs internal modification of the substrate (see Patent Document 2).
In other words, using a laser with a wavelength that is transparent to the substrate, adjust the repetition frequency and pulse width of the pulsed laser beam so that it is a suitable cutting laser beam for processing, and align the focusing point inside the substrate. The modified layer can be formed without causing ablation. In this laser processing technique, burst pulse light (burst train) composed of a plurality of (for example, 2 to 10) fine pulse widths is used instead of directly irradiating a cutting laser beam having an adjusted pulse width. It is made to oscillate and irradiate in the divided state.

For example, when a split laser beam having a repetition frequency of 100 kHz (a pulse is generated at a cycle of 10 μs (μs)) and a pulse width of 200 ns is generated with a pulsed light energy of 10 μJ by the pulsed light generating unit, burst pulsed light forming unit Thus, this dividing laser beam is oscillated in a state where it is divided into 10 burst pulse lights (burst trains) having a fine pulse width of 1 ns. In this case, the peak power of the burst pulse light is theoretically (10 μJ / 10) / 1 ns = 1 kW on average, but the peak power of each burst pulse light may be equal to or different from each other. (For example, increasing the peak power of each burst pulse light sequentially, decreasing the peak power, etc.).
Then, a pulse laser beam having a wavelength that is transparent to the silicon substrate (eg, 1064 nm) and having a pulse width suitable for modification is oscillated as burst pulse light having such a plurality of fine pulse widths, and condensed. The burst pulse light is focused on the central portion in the thickness direction of the substrate by the detector, and the silicon substrate is irradiated in the “burst mode”. As a result, it is possible to suppress damage to the opposite surface caused by light leaking to the surface opposite to the laser incident surface in the workpiece, and to suppress damage to the device formed on the opposite surface. It is disclosed that it can be done.

  Further, as a processing method for cleaving a substrate using a burst train (burst pulse light) of a cutting laser beam, another literature discloses a laser processing technique for forming a “filament” in a substrate and processing the substrate. . In other words, a long laser beam is accumulated by irradiating a substrate with a focused laser beam focused by an objective lens, which is called a “laser filament” (hereinafter abbreviated as “filament”) having a length of several hundred microns or several millimeters. Patent Document 3 discloses that a narrow channel is formed in a substrate, and the substrate is translated to move the filament in a straight line or a curved line to cut and process a filament track (particularly, columns 0035 and 0039). . In this document, glass, semiconductor, transparent ceramics, polymer, transparent conductor, wide band gap glass, crystal, crystal quartz, diamond, and sapphire are described as substrate materials to which this processing method can be applied.

Further, Patent Document 4 discloses an improved method for further expanding the “laser filament” described in Patent Document 3 to form a longer spatially homogeneous filament.
According to this document, Patent Document 3 discloses that an incident laser beam composed of a burst of an ultrafast pulsed laser beam can be focused inside a substrate by a “focusing lens” to form a filament of about several hundred microns inside the substrate. It is going to be.

Japanese Patent No. 3408805 JP 2014-104484 A Special table 2013-536081 gazette Japanese Patent Laying-Open No. 2015-037808

  In order to divide the glass substrate on which the modified layer whose strength is weakened by the “laser filament” shown in Patent Documents 3 and 4 above, the break bar is pressed along the modified layer and the substrate is machined. The method of dividing | segmenting by bending is taken. At this time, when the planned dividing line on which the modified layer is formed is a straight line, the dividing line can be cleanly divided along the planned dividing line. However, as shown in FIG. In the case of a quadrangular shape having an arc, or when there is an arcuate convex portion S2 in the middle of a straight segmentation line S as shown in FIG. 7 (b), the region of the arc S1 or the convex portion S2 is scheduled to be segmented. It becomes difficult to bend along the line S evenly, and it cannot be divided cleanly.

In view of this, a method of irradiating the modified layer with a CO ₂ laser and dividing it by a compressive stress due to heating may be considered instead of the mechanical dividing means using a break bar.
However, in the break by the CO ₂ laser, when the modified layer is irradiated with the laser beam and scanned, a small crack K tends to occur ahead of the laser irradiation point P in the laser traveling direction as shown in FIG. There is. This phenomenon is not a problem when the line to be divided S is a straight line, but in the case of an arc, since the crack precedes in the tangential direction of the arc, the crack K1 is advanced as shown in FIG. It cannot be divided. In particular, when the radius of the arc is 5 mm or less, the division becomes more difficult. Also, as shown in FIG. 9B, when there is an arc-shaped convex portion S2 in the middle of a straight line segmentation planned line S, the yield is increased due to a crack K2 extending across the bottom of the convex portion S2. There was a problem of getting worse.

The present invention includes a purpose of using the aberration Rezabi beam comprising bursts of pulsed laser beams, to provide a modified layer forming method, and modified layer forming apparatus capable of separating the brittle material substrate accurately clean To do.

In order to achieve the above object, a modified layer forming method for a brittle material substrate according to the present invention generates a laser beam including a burst of a pulsed laser beam into an aberration laser beam through an aberration generating lens that causes aberration. And scanning the aberration laser beam along the planned cutting line of the brittle material substrate to form a modified layer (usually a modified layer with reduced strength), thereby cutting the brittle material substrate along the planned cutting line. I try to divide it.
In the modified layer forming method of the present invention, it is preferable that the most focused portion of the aberration laser beam that is most focused is scanned in accordance with the intermediate position of the thickness of the brittle material substrate. Here, the most focused part of the aberration laser beam is a position where the peak power of the beam profile becomes highest when the beam profile (intensity distribution) is measured along the irradiation direction of the aberration laser beam (irradiation of the aberration laser beam). Position along the direction).

  Further, in the brittle material substrate cutting apparatus of the present invention made from another point of view, an aberration is generated between the table on which the brittle material substrate is placed and the laser beam including the burst of the pulsed laser beam emitted from the light source. An aberration laser beam emitting member that generates an aberration laser beam through an aberration generating lens to be moved, and an aberration laser beam emitting member that relatively moves the aberration laser beam emitting member along a planned cutting line of the brittle material substrate The mechanism consists of a mechanism.

  Since the present invention is configured as described above, a brittle material substrate such as a glass substrate is scheduled to be cut by moving it while irradiating the cutting laser beam along the line of the modified layer formed by the aberration laser beam. Can be completely cut along the line. Therefore, even if the planned dividing line is a quadrangle having an arc at the corner or a complicated shape having a curved convex part in the middle of the straight scheduled dividing line, the tangential direction of the arc There is an effect that it is possible to cleanly divide along the line to be cut without causing a crack that runs ahead of or a crack that crosses the bottom of the convex portion.

In the present invention, the aberration generating lens is preferably a plano-convex lens. In this case, the aberration laser beam can be emitted from the convex surface side by making the laser beam incident from the plane side of the plano-convex lens.
Further, in the present invention, the light source of the aberration laser beam is a near-infrared laser having a wavelength of 0.7 to 2.5 μm (for example, a fundamental wave of Nd: YAG laser), and a pulse width is 100 picoseconds or less. A burst of laser beams may be used.

Schematic explanatory drawing of the modified layer forming apparatus which concerns on this invention. The block diagram which shows the optical system of the aberration laser beam light emission member in this invention. FIG. 4 is an enlarged explanatory view showing a focused state of an aberration laser beam. The conceptual diagram which shows the profile of the burst of a pulse laser beam. Explanatory drawing which shows the modified layer formation process ( 1st step ) in this invention. Explanatory drawing which shows the parting process process ( 2nd step ) after the modified layer formation process in this invention. The top view which shows an example of the shape of a dividing line. Plan view for explaining the occurrence of cracking during cutting by CO ₂ laser beam. The top view for demonstrating generation | occurrence | production of the crack in the parting plan line shown in FIG.

The details of the present invention will be described below based on the embodiments shown in the drawings.
FIG. 1 is a view showing a scribing (modified layer forming) apparatus (cutting apparatus) A according to the present invention.
The scribing device A is provided with a horizontal beam (lateral beam) 3 provided with guides 2 along the X direction on the left and right columns 1, 1. A scribe head 5 provided with an aberration laser beam emitting member 4 and a scribe head 8 provided with a dividing laser beam emitting member 6 and a cooling member (cooling medium) 7 are arranged on the guide 2 of the beam 3 by a motor M1. It is attached so that it can move in the direction. A table 9 on which the brittle material substrate W to be processed is placed and sucked and held is held on a base plate 11 via a rotation mechanism 10 having a vertical axis as a fulcrum, and the base plate 11 is a motor M2. It is formed so that it can move in the Y direction (the front-rear direction in FIG. 1) by the screw 12 driven by. In this embodiment, the aberration laser beam emitting member 4 and the dividing laser beam emitting member 6 are separately attached to the individual scribe heads 5 and 8, but they may be attached to a common scribe head. .

As shown in FIG. 2, the aberration laser beam emitting member 4 attached to the scribe head 5 has a pulse width (pulse duration) of 100 picoseconds or less, preferably 50 picoseconds or less (usually 1 picosecond or more), Here, a light source 4a that emits a pulse laser beam of 15 picoseconds, an optical modulator 4b that emits a pulse laser beam oscillated from the light source 4a as a set of divided burst trains, and an output from the optical modulator 4b. And an aberration generation lens 4c that causes aberration in the laser beam L1.
Note that a near-infrared laser having a wavelength of 0.7 to 2.5 μm can be used as the light source 4a.
An optical modulator 4b that emits a burst sequence of a pulse laser beam is disclosed in, for example, Japanese Translation of PCT International Publication No. 2012-515450. Here, a burst sequence of a pulse laser beam is generated using a known optical modulator. It is assumed that the light is emitted, and a detailed description thereof is omitted.

  The aberration generation lens 4c used for causing aberration in the laser beam L1 emitted from the optical modulator 4b is not particularly limited, but here, the focal point is dispersed in the optical axis direction and the laser beam L1 that has passed therethrough is passed. A plano-convex lens is used in which the lens is focused so as to form a blurred focus in the axial direction to cause aberration. The laser beam L1 that has passed through the plano-convex lens becomes an aberration laser beam L2 having a dispersed focus. By making the laser beam L1 incident from the plane side of the plano-convex lens, the aberration laser beam L2 can be emitted from the convex surface side.

  As shown in FIG. 3A, the aberration laser beam L2 generated from the burst sequence of the pulsed laser beam is focused by the aberration generation lens 4c, so that the laser energy is accumulated at each focal point f, and is narrow and long. An energy distribution region F can be formed. FIG. 3B schematically shows an enlarged view of the high energy distribution region F. By forming such a high energy distribution region F, when the surface of a soda glass substrate, for example, is irradiated as the brittle material substrate W that is a processing target, the strength decreases from the irradiated surface of the processing target substrate W to the deep inside. The modified layer can be processed.

In the cutting laser beam L3 (see FIG. 6) emitted from the cutting laser beam emitting member 6 attached to the other scribe head 8, the modified layer whose strength has been weakened by the compressive force due to heating is completely cut. A laser beam that can be used is used. In the present embodiment, a CO ₂ laser beam having a wavelength of 10.6 μm was used as the dividing laser beam L3. In place of the CO ₂ laser beam, an IR laser beam having a wavelength of 0.7 to 10 μm can also be used. Further, as the refrigerant injected from the cooling member 7, cooling air, sprayed water, or the like can be used.

  Next, a method for dividing the brittle material substrate W according to the present invention using the scribing apparatus A will be described below with reference to FIGS. In this example, a soda glass substrate having a thickness of 1.8 mm was used as the brittle material substrate W to be processed.

  First, as shown in FIGS. 5 and 6, the substrate W is placed on the table 9, and the aberration laser beam L <b> 2 emitted from the aberration laser beam emitting member 4 is irradiated toward the substrate W, and the scribe head 5 and The aberration laser beam emitting member moving mechanism by the guide 2 moves the substrate W along the planned cutting line S. At this time, the high energy distribution region F in the converging portion of the aberration laser beam L2 is set to an intermediate position of the thickness of the substrate W. As a result, the modified layer (usually, the modified layer whose strength has become weak) can be processed along the planned dividing line S from the irradiated surface of the substrate W to the deep inside.

Here, an example of a preferable implementation condition of the aberration laser beam L2 including a burst (burst train of pulse laser beams) is shown below.

Laser output: 19.4W
Repetition frequency: 32.5 kHz
Pulse width: 15 picoseconds Pulse interval (laser pulse irradiation interval on the substrate): 4 μm
Burst: 4 pulses Pulse energy: 155 μJ / 1 burst Scanning speed: 130 mm / s

The processing depth and processing state can be easily controlled by adjusting the laser output, repetition frequency, pulse width, burst number, pulse interval, aberration, and the like described above.

  FIG. 4 is a schematic diagram showing a burst train of pulse laser beams. Four fine pulses p obtained by dividing each pulse laser beam are formed, and this is intermittently irradiated for each repetition frequency.

As described above, after processing the modified layer whose strength has decreased along the planned division line S with respect to the substrate W, as shown in FIG. 6A, the planned divided line S obtained by processing the modified layer. While being irradiated with the CO ₂ laser beam L3 from the dividing laser beam light emitting member 6 toward the direction, it is moved along the scheduled cutting line S by the dividing laser beam light emitting member moving mechanism including the scribe head 8 and the guide 2. At the same time, the coolant is injected from the cooling member 7 toward the front side in the traveling direction of the irradiation point P of the CO ₂ laser beam L3. FIG. 6B is a plan view of a portion of the irradiation point P of the CO ₂ laser beam L3 on the substrate W as viewed from above, and a cooling region by the cooling member 7 is indicated by a symbol B. The cooling region B is formed so as to cool the front side in the traveling direction of the irradiation point P of the laser beam (preferably surrounding the periphery of the irradiation point P around the front side in the traveling direction of the irradiation point P) by scattering of the coolant.

In this way, the substrate W is completely divided along the planned division line S by the thermal stress by moving the modified layer along the planned division line S while being irradiated with the CO ₂ laser beam L3. At this time, the front side in the traveling direction of the irradiation point P of the CO ₂ laser beam L3 (preferably the periphery of the irradiation point P around the front side in the traveling direction of the irradiation point P) is cooled. Thermal stress, that is, compressive stress due to heating, and tensile stress due to cooling can be effectively increased, and as a result, the crack K on the front side in the laser traveling direction as described above with reference to FIG. 8 is generated. In addition, only the portion of the irradiation point P can be effectively divided. Therefore, for example, as shown in FIG. 9A, when the planned dividing line S has a quadrangular shape having an arc S1 at the corner, or in the middle of the straight divided scheduled line S as shown in FIG. 9B. Even if it has a circular arc-shaped convex part S2, it is possible to divide neatly along the planned cutting line S without causing a crack K1 that runs ahead in the tangential direction of the circular arc or a crack K2 that crosses the bottom of the convex part S2. Can do.
Further, since the thermal stress can be increased by cooling the front side in the traveling direction of the irradiation point P of the CO ₂ laser beam L3 (preferably around the front side in the traveling direction of the irradiation point P), the CO ₂ laser can be increased. Even if the output of the beam L3 is lowered, it can be divided and the power consumption can be reduced.

As mentioned above, although typical embodiment of this invention was described, this invention is not necessarily limited only to said embodiment. For example, in the above-described embodiment, after the modified layer is formed on all the planned dividing lines by the irradiation of the aberration laser beam, the modified layer is irradiated with a cutting laser beam such as a CO ₂ laser beam to be divided. However, the cutting laser beam may be irradiated following the irradiation of the aberration laser beam. In the present invention, the object of the present invention can be achieved and modified and changed as appropriate without departing from the scope of the claims.

  The present invention can be used when a brittle material substrate such as a glass substrate is cut.

A Scribe (modified layer formation) device (cutting device)
B Cooling region F High energy distribution region K Crack L1 Laser beam L2 Aberration laser beam L3 Laser beam for cutting (CO ₂ laser beam)
P Laser beam irradiation point S Scheduled line W Brittle material substrate 2 Guide 4 Aberration laser beam light emitting member 4a Light source 4b Optical modulator 4c Aberration generating lens 5 Scribe head 6 Laser beam light emitting member for cutting 7 Cooling member (cooling medium) )
8 Scribe head 9 Table

Claims (3)

A method for forming a modified layer of a brittle material substrate,
A laser beam including a burst of pulsed laser beam is transmitted through an aberration generating lens that generates aberration, and is generated into an aberration laser beam.
Modified layer forming method of the brittle material substrate, characterized in Rukoto forming form a modified layer by scanning along be cut line of the aberration laser beam brittle material substrate. 2. The modified brittle material substrate according to claim 1, wherein a light source of the aberration laser beam is a near infrared laser having a wavelength of 0.7 to 2.5 μm, and a burst of a laser beam having a pulse width of 100 picoseconds or less is used. Quality layer forming method. A table on which a brittle material substrate is placed;
An aberration laser beam emitting member that generates a laser beam including a burst of a pulsed laser beam emitted from a light source into an aberration laser beam via an aberration generation lens that generates aberration;
An apparatus for forming a modified layer of a brittle material substrate, comprising: an aberration laser beam light emitting member moving mechanism that relatively moves the aberrant laser beam light emitting member along a planned cutting line of the brittle material substrate.

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