KR20130033113A

KR20130033113A - Laser processing method

Info

Publication number: KR20130033113A
Application number: KR1020110096986A
Authority: KR
Inventors: 오창호; 이동준
Original assignee: 주식회사 이오테크닉스
Priority date: 2011-09-26
Filing date: 2011-09-26
Publication date: 2013-04-03

Abstract

PURPOSE: A laser processing method is provided to separate a substrate in a width direction and to prevent a waste of materials by forming reforming regions in a direction perpendicular to a width direction of the substrate inside the substrate. CONSTITUTION: A laser processing method comprises the following steps: a step for forming a plurality of first reforming regions(125) between a first surface(110b) of a substrate(110) and an internal surface of the substrate by focusing first laser beams along a dicing intended line; a step for forming a plurality of second reforming regions inside the substrate in a direction perpendicular to a width direction of the substrate by focusing second laser beams on a cleaving intended line inside the substrate; a step for cleaving the substrate in a direction perpendicular to the width direction of the substrate; and a step for dicing the substrate in the width direction of the substrate.

Description

Laser processing method

The present invention relates to a laser processing method, and more particularly, to a laser processing method including forming a modified region inside a substrate and cleaving the substrate in a direction perpendicular to the substrate thickness direction.

After forming a laminate including a pattern or elements on a semiconductor substrate such as a silicon wafer, a dicing before grinding (DBG) process is conventionally used as a method for dividing the semiconductor substrate into a plurality of chips.

1A to 1D show an example of a laser processing method using a DBG process. Referring to FIG. 1A, for example, a substrate 10 such as a silicon wafer, a sapphire substrate, a glass substrate, or the like is provided, and a laminate 15 including a pattern or elements is formed on the bottom surface 10b of the substrate 10. Formed. In the substrate 10, a dicing schedule line 20 for a dicing process is set. The dicing scheduled line 20 is formed along the thickness direction of the substrate 10 from the upper surface 10a of the substrate 10 to the lower surface 10b of the substrate 10 inside the substrate 10 located at a predetermined depth. . Subsequently, the dicing processing unit 50 provided on the substrate 10 performs a dicing process along the dicing schedule line 20. Here, the laser beam emitted from the dicing processing unit 50 is focused in the substrate 10 to form a focusing point, and the modified region 25 is formed in the substrate 10 by the focusing point. When the dicing unit moves along the thickness direction of the substrate 10 and repeatedly focuses the laser beam inside the substrate 10, the dicing processing unit is disposed between the inside of the substrate 10 and the lower surface 10b of the substrate 10. A plurality of modified regions 25 may be formed along the thickness direction of the substrate 10.

When the dicing process is completed for all the dicing scheduled lines 20 in this way, as shown in FIG. 1B, the lower surface of the substrate 10 in the substrate 10 along the thickness direction of the substrate 10. Reformed regions 25 are formed between 10B. Next, in order to process the substrate 10 to a desired thickness, a grinding process is performed on the upper surface 10a side of the substrate 10. This grinding process continues until the substrate 10 is at the desired thickness. When the grinding process is completed, as shown in FIG. 1C, only the lower part 10 ″ of the substrate 10 and the stack 15 formed on the lower surface 10 b of the lower part 10 ″ of the substrate remain. In addition, if a natural or external mechanical force is applied to the lower portion of the substrate 10 ″ in the state shown in FIG. 1C, cracks may be generated by the modified regions 25. As shown, the lower substrate 10 ″ may be divided into a plurality of chips 70.

However, in the above-described DBG process, the substrate 10 must be polished until the substrate 10 has a predetermined thickness, and a large amount of solid powder is generated through the polishing process. Since these solid powders are often thrown away without being recycled, economic and environmental problems may be caused.

The present invention provides a laser processing method comprising forming a modified region inside a substrate to separate the substrate in a direction perpendicular to the substrate thickness direction.

In one aspect of the present invention,

Focusing a first laser beam within the substrate along a dicing predetermined line to form a plurality of first modified regions between the substrate and the first surface of the substrate;

Focusing a second laser beam on a cleaving line in the substrate to form a plurality of second modified regions in the substrate in a direction perpendicular to a thickness direction of the substrate;

Cleaving the substrate in a direction perpendicular to the thickness direction; And

Dicing the substrate in the thickness direction is provided a laser processing method comprising a.

The first and second laser beams may be focused into the substrate through the second surface of the substrate.

At least one first reformed region may be formed in a thickness direction of the substrate. When the plurality of first modified regions are formed along the thickness direction of the substrate, the plurality of first modified regions may be sequentially formed while going toward the first laser beam.

The step of cleaving the substrate in a direction perpendicular to the thickness direction may include spreading a crack generated by the second modified regions inside the substrate. Here, spreading the crack generated by the second reforming regions within the substrate may be performed by a water jet, an aerosol jet, a laser, or a blade.

Dicing the substrate in a thickness direction may include dicing the substrate by cracks generated by the first modified regions. Here, dicing the substrate may be performed by natural or mechanical force.

The substrate may include a light transmissive material. Patterns or elements may be formed on the first surface of the substrate.

Dicing processing units and cleaving processing units may be provided on the optical paths of the first and second laser beams, respectively. The dicing unit moves between the inside of the substrate and the first surface of the substrate by focusing the first laser beam on the inside of the substrate to form a focusing point while moving relative to the substrate along the dicing line. The first modified regions may be formed. The cleaving processing unit moves the second laser beam within the substrate to form a light converging point while moving relative to the substrate along the scheduled cleaving line, thereby forming the converging point in the direction perpendicular to the thickness direction of the substrate. Two modified regions can be formed.

The dicing processing unit and the cleaving processing unit may each include at least one high reflectivity optical mirror, at least one beam expander, and at least one optical lens. In addition, the cleaving processing unit is to divide one laser beam into a plurality of laser beams, and may further include a diffractive optical element having a plurality of diffractive gratings.

In another aspect of the present invention,

Forming a plurality of first modified regions between the substrate and the first surface of the substrate by focusing a first laser beam inside the substrate to form a focusing point along a dicing line; And

And forming a plurality of second modified regions in a direction perpendicular to the thickness direction of the substrate by focusing a second laser beam inside the substrate along a cleaving line to form a condensing point. do.

According to the present invention, the substrate can be separated in the thickness direction by forming modified regions in the direction perpendicular to the substrate thickness direction. Accordingly, it is possible to prevent waste of materials generated through the conventional polishing process, thereby solving problems that may occur in economic and environmental aspects.

1A to 1D are diagrams for explaining a laser processing method using a conventional DBG process.
2A to 2E are views for explaining a laser processing method according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals refer to like elements, and the size and thickness of each element may be exaggerated for clarity of explanation.

2A to 2E are views for explaining a laser processing method according to an embodiment of the present invention.

Referring to FIG. 2A, a substrate of a light transmissive material through which a laser can be transmitted may be used as the substrate 110 that is an object to be processed. For example, a glass substrate, a sapphire substrate, a silicon substrate, or the like may be used as the substrate 110, and a substrate of various materials may be used. Meanwhile, a stacking part 115 such as a pattern or elements may be formed on the first surface 110b of the substrate 110. However, the present invention is not limited thereto, and patterns or elements may not be formed on the substrate 110. The substrate 110 may be provided to be in close contact with a movable stage (not shown) on which a vacuum chuck is mounted. Here, when the substrate is provided on the xy plane, the stage is provided so as to be movable in the θ direction, which is the rotation direction on the x, y and z directions and the xy plane. Meanwhile, a dicing schedule line 120 for a dicing process and a cleaving schedule line 130 for a cleaving process are set in the substrate 110. Here, the dicing schedule line 120 is formed along a thickness direction of the substrate 110 between a predetermined position inside the substrate 110 and the first surface 110b of the substrate 110. 130 may be formed in the substrate 110 along a direction perpendicular to the thickness direction of the substrate 110.

First modified regions 125 are formed in the substrate 110 by using the dicing processing unit 150 provided on the substrate 110. Specifically, after placing the dicing processing unit 150 on the dicing line 120 formed in the substrate 110, the first laser beam from the dicing processing unit 150 to the substrate 110 Irradiate toward the second surface 110a, i.e., the upper surface. The first laser beam irradiated in this way is focused at a predetermined position inside the substrate 110 through the second surface 110a of the substrate 110 to form a light collecting point. As such, when the light converging point is formed in the substrate 110 by focusing the first laser beam, a first modified area 125 may be formed by absorption of multiple photons. As the first laser beam for forming the first reformed region 125, for example, a pulse width of about 1 dB or more and a peak power density at a condensing point of about 1 × 10 ⁸ (W / cm ² ) or more Lasers can be used. The dicing processing unit 150 is disposed on the optical path of the first laser beam, and may include a plurality of optical elements. For example, the dicing processing unit 150 may include at least one high reflectivity optical mirror having a reflectance of 70% or more, at least one beam expander for adjusting the size of the laser beam, It may include at least one optical lens having a numerical aperture of 0.1 or more. Here, the high reflectivity optical mirror is to change the direction of the laser beam, there is a light loss every time the laser beam passes through the optical mirror, in order to minimize this loss to minimize the number of optical mirrors of each optical mirror The reflectance needs to be maximized. Thus, a highly reflective optical mirror can be used for this. In addition, the beam expander extends the beam diameter of the incident laser beam and emits the beam. The beam expander may expand the size of the pulse laser generated by the laser light source by more than twice, and also pass the laser beam through the optical lens. It is possible to control the spot size at the focal point of.

The first reformed region 125 may be formed between the inside of the substrate 110 and the first surface 110b of the substrate 110. In addition, a plurality of first modified regions 125 may be formed between the inside of the substrate 110 and the first surface 110b of the substrate 110 along the thickness direction of the substrate 110. That is, when the dicing processing unit 150 moves upward along the thickness direction of the substrate 110 and forms condensing points in the substrate 110 through the second surface 110a of the substrate 110, The first modification regions 125 may be sequentially formed while going into the substrate 110 from the side of the first surface 110b of the substrate 110. When the dicing processing unit 150 or the stage moves along the dicing schedule line and performs a dicing process, as shown in FIG. 2B, the substrate 110 is formed on all dicing schedule lines 120. The first modified regions 125 are formed in the thickness direction of the first modified regions 125.

In FIG. 2B, three first modified regions 125 are formed between the inside of the substrate 110 and the first surface 110b of the substrate 110, but the present disclosure is not limited thereto. One reformed region 125 may be formed. In addition, in FIG. 2A, since the dicing processing unit 150 moves in the thickness direction of the substrate 110, the first modified regions 125 are disposed between the first surface 110b of the substrate 110 and the inside of the substrate 110. Although the case in which the substrate 110 is formed has been described, the first modified regions 125 may be formed between the first surface 110b of the substrate 110 and the inside of the substrate 110 by moving the stage to which the substrate 110 is attached. It is possible.

Subsequently, referring to FIG. 2B, second reforming regions 135 are formed in the substrate 110 by the cleaving processing unit 160 provided on the substrate 110. Specifically, the cleaving processing unit 160 is positioned on the cleaving line 130 formed in the substrate 110, and then a second laser beam is emitted from the cleaving processing unit 160. Irradiate toward the second surface 110a, i.e., the upper surface. The irradiated second laser beam is focused at a predetermined position inside the substrate 110 through the second surface 110a of the substrate 110 to form a light collecting point. As such, when the light converging point is formed in the substrate 110 by focusing the second laser beam, the second modified region 135 may be formed by the multiphoton absorption. Like the first laser beam, the second laser beam for forming the second modified region 135 may have, for example, a pulse width of about 1 dB or more and a peak power density at a light collection point of about 1 × 10 ⁸ (W / cm ² ) or more pulse laser can be used.

When the cleaving processing unit 160 repeatedly moves along the cleaving line 130 in a direction perpendicular to the thickness direction of the substrate 110 and repeatedly forms a light converging point, the substrate 110 may have an interior of FIG. 2C. As illustrated in FIG. 2, the plurality of second modified regions 135 may be formed along the cleaving line 130 in a direction perpendicular to the thickness direction of the substrate 110. Meanwhile, in FIG. 2B, the case in which the second reforming regions 135 are formed between the inside of the substrate 110 by moving the cleaving processing unit 160 in a direction perpendicular to the thickness direction of the substrate 110 has been described. As the stage to which the substrate 110 is attached moves, the second modified regions 135 may be formed between the inside of the substrate 110. The cleaving processing unit 160 is disposed on the optical path of the second laser beam, and may include a plurality of optical elements. For example, the cleaving processing unit 160, like the dicing processing unit 150, at least one high reflectance optical mirror having a reflectance of 70% or more, at least one beam expander and opening for adjusting the size of the laser beam The number may include at least one optical lens having at least 0.1. On the other hand, the cleaving processing unit 160 is to reduce the time required to form the second modified regions 135 by dividing one laser beam into a plurality of laser beams, a plurality of diffractive gratings It may further include a diffractive optical element (diffractive optical element) having a.

Subsequently, cracks are spread throughout the substrate 110 by the second modified regions 135 formed in the substrate 110 in a direction perpendicular to the thickness direction of the substrate 110. As such, spreading the cracks throughout the substrate 110 may be performed using a water jet, an aerosol jet, a laser or a blade. However, the present invention is not limited thereto. Due to the spread of the crack, the substrate 110 is separated into the upper substrate 110 'and the lower substrate 110 "as shown in FIG. 2D. Here, the upper substrate 110' has a second surface. 110a, and the lower substrate 110 ″ includes the first surface 110b. In addition, the stacking part 115 is formed on the first surface 110b.

Finally, referring to FIG. 2E, a plurality of chips 170 may be formed by dicing the lower substrate 110 ″ in which the first modified regions 125 are formed in the thickness direction of the substrate 110. Will be divided into Here, the lower substrate 110 ″ may be divided by cracks generated by the first modified regions 125 by applying a natural or mechanical force.

As described above, in the laser processing method according to the exemplary embodiment of the present invention, before dividing the substrate 110 into a plurality of chips 170, the second substrate is disposed in the substrate 110 in a direction perpendicular to the thickness direction of the substrate 110. The substrate 110 is cleaved in a direction perpendicular to the thickness direction of the substrate 110 by forming the modified regions 135 and spreading the cracks due to the second modified regions 135 all over the inside of the substrate 110. Done. Therefore, it is possible to prevent the waste of substrate material and environmental pollution caused by the conventional polishing process.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined by the appended claims.

10,110 ... substrate 10a, 110a ... second side of substrate
10b, 110b ... first side of substrate 15,115 ... laminate
20,120 ... Dicing line 25 ... Reform area
50,150 ... Dicing Processing Unit 70,170 ... Chip
125 ... First reforming area 130 ... Scheduled cleaving line
135 ... second reforming area 160 ... cleaving unit

Claims

Focusing a first laser beam within the substrate along a dicing predetermined line to form a plurality of first modified regions between the substrate and the first surface of the substrate;
Focusing a second laser beam on a cleaving line in the substrate to form a plurality of second modified regions in the substrate in a direction perpendicular to a thickness direction of the substrate;
Cleaving the substrate in a direction perpendicular to the thickness direction; And
And dicing the substrate in a thickness direction.

The method of claim 1,
And the first and second laser beams are focused into the substrate through a second surface of the substrate.

The method of claim 1,
At least one first modification region is formed in a thickness direction of the substrate.

The method of claim 1,
A plurality of first modified regions are formed along the thickness direction of the substrate, the plurality of first modified regions are sequentially formed while going toward the first laser beam incident.

The method of claim 1,
The step of cleaving the substrate in a direction perpendicular to the thickness direction includes spreading cracks generated by the second modified regions inside the substrate.

The method of claim 5, wherein
And spreading the cracks generated by the second modified regions within the substrate by a water jet, an aerosol jet, a laser, or a blade.

The method of claim 5, wherein
Dicing the substrate in a thickness direction includes dicing the substrate by cracks generated by the first modified regions.

The method of claim 7, wherein
And dicing the substrate is a natural or mechanical force.

The method of claim 1,
The substrate is a laser processing method comprising a translucent material.

The method of claim 1,
And a pattern or elements are formed on the first surface of the substrate.

The method of claim 1,
And a dicing processing unit and a cleaving processing unit, respectively, on the optical paths of the first and second laser beams.

The method of claim 11,
The dicing unit moves between the inside of the substrate and the first surface of the substrate by focusing the first laser beam on the inside of the substrate to form a focusing point while moving relative to the substrate along the dicing line. And a laser processing method for forming the first modified regions.

The method of claim 11,
The cleaving processing unit moves the second laser beam within the substrate to form a light converging point while moving relative to the substrate along the scheduled cleaving line, thereby forming the converging point in the direction perpendicular to the thickness direction of the substrate. Laser processing method for forming two modified regions.

The method of claim 11,
Wherein said dicing processing unit and the cleaving processing unit each comprise at least one high reflectivity optical mirror, at least one beam expander and at least one optical lens.

15. The method of claim 14,
The cleaving processing unit is for dividing one laser beam into a plurality of laser beams, the laser processing method further comprising a diffractive optical element having a plurality of diffractive gratings.

Forming a plurality of first modified regions between the substrate and the first surface of the substrate by focusing a first laser beam inside the substrate to form a focusing point along a dicing line; And
And forming a plurality of second modified regions in a direction perpendicular to a thickness direction of the substrate by focusing a second laser beam inside the substrate along a cleaving line to form a condensing point.

17. The method of claim 16,
Cleaving the substrate in a direction perpendicular to the thickness direction; And
Dicing the substrate in the thickness direction; Laser processing method further comprising.

17. The method of claim 16,
And the first and second laser beams are focused into the substrate through a second surface of the substrate.

The method of claim 18,
And a pattern or elements are formed on the first surface of the substrate.