KR101616952B1 - Method of Completely Cutting Brittle Substrate with Arbitrary Form - Google Patents

Abstract

The present invention relates to a method of cutting a brittle material substrate by cutting a brittle material substrate by irradiating a laser pulse beam without cutting the brittle material directly along the target path, ≪ / RTI >

Description

TECHNICAL FIELD [0001] The present invention relates to a method for cutting a brittle material,

The present invention relates to a method of cutting a brittle material such as a fragile glass or a semiconductor wafer and a method of completely cutting the brittle material onto a substrate by irradiating the brittle material along a target path.

Generally, in order to cut a brittle material such as a glass or a semiconductor wafer which is easily broken by using a laser, a laser is irradiated on a substrate to be cut to form a defect on the surface or inside of the substrate, There is a technique of cutting the substrate along a line along which the substrate is to be cut by applying a suitable force to the substrate or using a coolant. However, since it tends to be broken in an undesired direction, it is difficult to cut the substrate directly or to secure a desired line to be cut. Such a method has a disadvantage that it adds a process cost and time and affects a yield reduction because it is accompanied by a process of applying a force to cut along a line to be cut rather than a complete cut once by a laser.

In addition, the heat generated in the process of irradiating the laser on the substrate to be cut may transmit the acoustic wave in the irregular direction to break the substrate in an undesired direction, so that it may be difficult to directly cut or obtain a desired line to be cut. It is difficult to secure the position accuracy and cutting quality because it is broken in an undesired direction.

Korean Priority No. 10-2009-0079342 (published on July 22, 2009) and Korean Registered Patent No. 10-1124347 (published on February 29, 2012) can be referred to as related prior arts .

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and it is an object of the present invention to provide a method of cutting a brittle material substrate by irradiating a laser pulse beam, Which is capable of completely cutting a brittle material along a target path directly without using a cooling method.

In order to accomplish the above object, according to one aspect of the present invention, there is provided a method of cutting a brittle material in a laser processing apparatus, , A substrate of a brittle material such as a glass substrate, a semiconductor wafer, or a sapphire substrate); Loading the substrate onto a stage; And irradiating the substrate with a laser (e.g., femtosecond laser) generated in the laser generation apparatus according to the laser generation condition along the target path, thereby performing complete cutting at a corresponding portion of the substrate irradiated with the laser .

The laser irradiation start position of the side edge of the substrate is a non-mirror side defect (Fig. 3). In the step of complete cutting, laser irradiation is started outside the laser irradiation start position of the substrate, So that a portion irradiated with the laser beam is caused to follow the target path on the substrate via the laser irradiation start position.

Wherein the laser beam is irradiated onto the substrate without cooling the laser beam irradiated on the substrate and is completely cut without cracking or melting in the irregular direction at the portion irradiated with the laser beam on the substrate.

The present invention is based on the principle that cracking in an irregular direction does not occur by eliminating transmission of a sound wave vibration due to minimization of heat generation at a laser-irradiated portion on the substrate.

The laser beam spot is irradiated to the side defects and the laser beam on the substrate adjacent to the laser beam spot irradiated to the side defects is irradiated to the side defects. The laser beam spots are superimposed on each other and the complete cutting is started.

According to the arbitrary shape cutting method of the brittle material according to the present invention, since the brittle material is completely cut along the target path without the need of a line process or a cooling method like the line to be cut, it is possible to reduce the process cost and increase the quality of the cut surface And it is also possible to easily cut the C chamfer (chamfer) for enhancing the edge strength as well as the target path made of a free curve such as a circle, an ellipse, and an arc shape by the same method.

1 is a flowchart illustrating a method of cutting a brittle material according to an embodiment of the present invention.
2 is a view for explaining an initial cutting process in a substrate to be cut having a side defect according to an embodiment of the present invention.
3 is a view for explaining a complete cutting method on a substrate to be cut according to an embodiment of the present invention.
Fig. 4 is a view for explaining a method for securing the C chamfer.
Figures 5A-5C illustrate examples of substrate side defects of the present invention.
FIG. 6 is an example of a state of a cut machining surface according to a complete cutting method according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout.

1 is a flowchart illustrating a method of cutting a brittle material according to an embodiment of the present invention.

Referring to FIG. 1, a brittle material cutting method using a laser processing apparatus according to an embodiment of the present invention includes setting data (S100) necessary for a control apparatus of a laser processing apparatus, preparing a substrate to be cut (S200) (S300), the start of cutting at the side of the edge of the substrate (S400), the cutting along the target path on the substrate (S500), and the like.

First, the substrate to be cut in the present invention refers to a substrate made of a brittle material such as a glass substrate, a semiconductor wafer, a sapphire substrate, a quartz material, and a substrate made of a solid and fragile material including various organic materials.

Although not shown in the drawings, the laser processing apparatus described below includes a stage for loading a substrate to be cut, a laser generating apparatus provided on the stage, and an optical system for irradiating the laser of the laser generating apparatus to the substrate A control device for controlling each component of the laser processing apparatus, and a user interface for inputting control data by the user. Such a control device may generate a control signal to perform the transfer of the stage or the optical system, the laser generation of the laser generation device, and the control of the optical system for focusing the laser on the substrate. Since such a laser generating apparatus is well known, a detailed description will be omitted.

In order to cut such a brittle substrate to be cut along an arbitrary target path such as a straight line, a circle, an ellipse, or an arc, the above-mentioned user uses a user interface to control the laser processing condition of the laser processing apparatus, The cutting control condition is set to a data input required for cutting such as a target path in which a path to be cut in advance is specified (S100). Here, the laser to be used for cutting the substrate is a femtosecond short ultrashort-pulse laser. The laser generator controls the laser generator to generate the femtosecond laser. The laser power, the laser beam spot size, And a cutting target path can be set by inputting data to the target path in order to automatically cut the substrate along the target path as shown in FIG.

In addition, a substrate to be cut of a brittle material is loaded on a stage of the laser processing apparatus by a fragile material such as a glass substrate, a semiconductor wafer, or a sapphire substrate (S200). The substrate loading can be done automatically or manually. As shown in FIG. 2, it is essential that a substrate having side defects other than the mirror surface is used as the side surface of the substrate to be loaded. Particularly, as described below, Side defects must be present.

After the setting of the cutting control condition (S100) and the loading of the substrate (S200), the laser generated in the laser generating apparatus of the laser processing apparatus is switched to the target path (S300 to S500) so that the laser beam is completely cut at the corresponding portion of the substrate.

As shown in Fig. 2, laser irradiation is started outside the substrate (S300) while moving the stage or the optical system in accordance with the setting of the cutting control condition (S100). In this case, it is preferable to use a femtosecond femtosecond short-pulse type laser, and in addition, a pulse type laser having a short irradiation time characteristic (Nanosecond, Picosecond, and Femtosecond) may be used.

As shown in FIG. 2, the laser irradiation start position among the side edges of the substrate must have a side defect, not a polishing surface. Usually, the edge side surfaces of the substrate are mirror-polished so that the roughness of the surface of the substrate is in the range of several tens of micrometers or less, and is used for the work by lapping, grinding, polishing or the like. However, It is preferable to use a substrate having a side surface irregular defect having a dimension, shape, and finish degree of a surface irregularity roughness of several hundred micrometers or more (e.g., greater than a laser beam spot size) even if it is processed.

Here, as a method of forming a defect on the side of the edge of the substrate, it is possible to use a nanosecond, a picosecond and a femtosecond laser pulse (see Figs. 5A, 5B and 5C) for causing cracks in the brittle material A post-treatment method, or a method of rubbing the glass surface with a material such as sandpaper to make the glass surface cloudy.

As an example of such a processing defect, when the substrate is processed by tempering glass (for example, Corning Gorilla III, 40 um DOL strengthened) substrate by grinding for glass surface or sandpaper as shown in FIG. 5A, 5B, when a laser beam is applied to the inside of the substrate using a pulse laser (machining to an inter-volume), a desired defect can be secured in a target portion to be a side surface of the substrate. Similarly, when the laser is focused on the outside of the substrate by using a pulsed laser and processed by filamentation, desired defects can be secured in a target portion to be a side surface of the substrate.

When the laser is irradiated outside the substrate (S300) and the laser reaches the laser irradiation start position of the substrate, complete cutting is started by cracking in the side defect of the laser irradiation portion (S400) The laser beam is irradiated to the laser irradiation start position of the same substrate and is completely cut along the target path on the substrate as shown in FIG. 3 (S500). Accordingly, unloading the object that has been separated and cut along the target path (withdrawal) makes it possible to obtain a desired object without a separate subsequent braking process.

Thus, by using a substrate having a defect on the side surface at the laser irradiation start position of the substrate, the cutting is started in the side defect of the substrate so that complete cutting is performed in the relevant side defect. In the case of mirror-surface processing without side defects, the laser can not absorb the laser beam due to reflection or scattering of the laser beam, and complete cutting can not be started.

As shown in FIG. 3, in order to completely cut the laser beam spot without being broken in the irregular direction, the laser beam spot of the portion irradiated with the side defect and the laser beam on the substrate adjacent thereto is spot- And the complete cutting is started while being overlapped with each other. That is, the speed at which the laser follows the target path by the optical system or the stage movement is important, and without the proper overlap of the laser pulse beam, the complete cut at the adjacent portion may not be continuous due to lack of energy to cut the substrate, It may be necessary to perform a subsequent process in which only a crack is generated so as to cut it by applying a further force. In addition, when the laser power is excessive, the heat generated in the substrate at the time of overlapping the laser beam spots causes a sound wave vibration, and such a sound wave vibration may cause a problem that the substrate of the brittle material breaks in an irregular direction.

Accordingly, in the present invention, by properly controlling the laser power and the degree of overlapping (overlap) of the laser beam spots according to the laser movement speed, it is possible to minimize the heat generation at the laser irradiated portion on the substrate, The process is performed under the condition of eliminating or suppressing the transmission of the sound wave vibration so as to prevent the substrate from being broken in an irregular direction (S500).

A microscope photograph of the cut surface of the substrate cut by the complete cutting method of the brittle material is illustrated in FIG. Here, the cutting quality of the mirror surface as shown in the sectional view of FIG. 6 can be obtained under conditions of 100 to 500 femtosecond laser, repetition rate of 50 to 200 kHz, power of 5 to 20 W, and cutting speed (conveying speed of the stage or optical system) of 10 to 300 mm / there was. As a result of the bending strength (4 point bending test), it was confirmed that the rigidity of 600 MPa or more can be secured. In addition, although the cutting speed is referred to as a stage or a conveyance speed of the optical system, when the stage moves, it can be seen that the laser moves on the stage when viewed from a fixed laser, 10 to 300 mm / sec. When the optical system is transported, it can be seen that the laser reflected from the optical system moves.

According to the method of cutting a brittle material according to the present invention, the substrate can be completely cut by melting in an irregular direction by performing a process under a condition that heat generation is minimized without cooling the laser irradiated portion on the substrate. In addition, since the brittle material is completely cut without a subsequent process of applying a force after a line process for forming cracks such as a line to be cut, and breaking the brittle material, the process cost can be reduced and the quality of the cut surface can be improved. In addition, the C-chamfering (chamfer) or rounding (see FIG. 4) for enhancing the edge strength as well as the target path made of a free curve such as a circle, an ellipse, and an arc shape can be easily cut by the same method. In C chamfering or rounding, the stage or the optical system is appropriately moved so that the laser is directed to the edge of the substrate, so that the edge of the substrate having the side defects can be cut to a certain length or rounded.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. This is possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

Claims (8)

In a brittle material cutting method in a laser processing apparatus,
Setting a target path in advance in the control device to specify a laser generation condition and a path to be cut of the substrate to be cut;
Forming side defects on the side surface of the substrate having a surface irregularity roughness larger than the laser beam spot set by the control device and loading the substrate on which the side defects are formed on the stage; And
And irradiating the substrate with a laser generated in the laser generator in accordance with the laser generation condition along the target path so that complete cutting is performed at the corresponding portion of the substrate irradiated with the laser,
The irradiation start position of the laser generated in the laser generator corresponds to the side defect of the substrate to be cut,
In the step of complete cutting,
Wherein the irradiation of the laser beam is started outside the laser irradiation start position of the substrate so that a portion irradiated with the laser beam follows the target path on the substrate via the laser irradiation start position. delete The method according to claim 1,
Wherein the laser beam is completely cut without melting the laser beam on the substrate and is melted without breaking in an irregular direction on the laser beam irradiated portion of the substrate. The method according to claim 1,
Wherein a propagation of a sound wave vibration due to minimization of heat generation at a laser-irradiated portion on the substrate is eliminated to prevent cracking in an irregular direction. The method according to claim 1,
The side defects at the laser irradiation start position begin to melt the side defective portion of the substrate so that the laser beam is absorbed and complete cutting is performed, and the laser beam spot irradiated to the side defects and the laser beam spot Wherein the laser beam spot of the portion to be irradiated with the laser beam is superposed and the complete cutting is started. The method according to claim 1,
Wherein the substrate is a brittle substrate comprising a glass substrate, a semiconductor wafer, or a sapphire substrate. The method according to claim 1,
Wherein the laser is a femtosecond laser. 6. The method of claim 5,
Wherein a speed at which the laser follows the target path for superposition of the laser beam spot and the laser beam spot adjacent thereto is 10 to 300 mm / sec.

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