JP2008006652A - Method for partitioning processing of rigid and brittle material plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To partition accurately along a predetermined line. <P>SOLUTION: In a method for partitioning a plate 10 of a rigid and brittle material, when the incidence of a repeating short optical pulse laser beam 30 with an optically transparent wavelength is performed into the surface 11 of the rigid and brittle material plate 10 through a condenser lens 200 to the rigid and brittle material plate 10 with a thickness t, the focus position of the condenser lens 200 is adjusted so that the waist 31 of the laser beam 30 exists either at a shallower or deeper position than the inner part t/2 of the rigid and brittle material plate body 10, and overlapping incidence of the repeating short optical pulse laser beam 30 into the surface 11 of the rigid and brittle material plate body 10. A process for generating a photo-induced breakage in a region of the waist 31 and in the neighborhood of the back face 12 of the rigid and brittle material plate body 10 separated in the depth direction from the region of the waist 31 is included. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for dividing a hard and brittle material plate used for a semiconductor substrate or the like, and more specifically, by forming a light-induced fracture region in a hard and brittle material plate to be divided using a short optical pulse laser beam. The present invention relates to a division processing method.

  Conventionally, when a hard and brittle material plate such as a semiconductor substrate, a piezoelectric ceramic substrate, or a glass substrate is divided and processed, a short wavelength having a transparent wavelength in the plate along the line to be divided is formed on the surface layer portion of the plate to be processed. An optical pulse laser is incident to generate fine melt marks with microcracks clustered on the surface layer, and then stress is applied to divide the cracks using the cracks generated from the fine melt marks toward the inside of the plate. (For example, refer to Patent Document 1).

In addition, a short optical pulse laser having a center wavelength in the vicinity of 1.5 μm, which is a transparent wavelength with respect to a plate body such as silicon, a group III-V semiconductor, or glass, is made incident along a predetermined division line from the front surface and focused on the rear surface. There is also known a split processing method in which light-induced destruction is caused at a condensing portion located on the back surface by performing condensing irradiation so that the position is located (see, for example, Patent Document 2).
JP 2005-271563 A JP 2004-351466 A

  In the conventional division processing method, fine melting marks or light-induced fracture marks are formed on the surface layer portion or the back surface of the hard and brittle material plate to be processed. That is, the conventional division processing method forms a laser processing mark only on the front surface or the back surface. Therefore, in the subsequent dividing step by applying stress, it is difficult to generate a crack starting from the laser processing trace along the planned dividing line, and it is difficult to perform the dividing along the planned dividing line with high accuracy.

  The present invention has been made in view of the above-described problems of the conventional division processing method, and an object thereof is to provide a division processing method for a hard and brittle material plate that can be divided with high accuracy along a predetermined division line.

  In order to solve the above-mentioned problem, the method for splitting a hard and brittle material plate of the present invention is a condensing lens for a repetitive short optical pulse laser beam having a wavelength optically transparent to a hard and brittle material plate having a thickness t. When the laser beam is incident on the surface of the hard and brittle material plate, the focal point of the condenser lens is such that the waist of the laser beam exists at a position shallower or deeper than the inside t / 2 of the hard and brittle material plate. The position of the laser beam is adjusted and the optical axis of the laser beam is assumed to be divided with respect to the hard and brittle material plate so that the repeated short light pulse laser beam is incident on the surface of the hard and brittle material plate. Each time the laser beam is incident on the surface of the hard and brittle material plate while relatively moving along the surface, the waist region and the hard and brittle material plate separated in the depth direction from the waist region. Causing light-induced breakdown near the backside It is characterized by comprising the step of.

  Since light-induced fracture marks are formed along the planned split lines on the inside and back surfaces or front and back surfaces of the hard and brittle material plate, it is possible to accurately split along the planned split lines in the subsequent splitting process by applying stress. it can.

  Moreover, it is preferable that the numerical aperture of the said condensing lens is 0.3 or less.

  When the numerical aperture is 0.3 or less, the so-called depth of focus is large, so that the beam waist gradually spreads in the direction of the optical axis. Therefore, even if the thickness of the plate to be processed increases, Photo-induced fracture marks can be formed on the back surface.

  Further, it is desirable that the position shallower than t / 2 is within the Rayleigh range from the surface of the hard and brittle material plate, and the position deeper than t / 2 is within the Rayleigh range from the back surface of the hard and brittle material plate. .

  Since the distance from the waist to the front or back surface is smaller than the Rayleigh range, even if the thickness of the plate to be processed increases, it is possible to more reliably form light-induced fracture marks on the inside and back surface or on the front and back surfaces. it can.

  Since light-induced fracture marks are formed along the planned split lines on the inside and back surfaces or front and back surfaces of the hard and brittle material plate, it is possible to accurately split along the planned split lines in the subsequent splitting process by applying stress. it can.

  A method for dividing a hard and brittle material plate according to the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram for explaining the division processing method of the present invention, FIG. 2 is a partially cutaway sectional view taken along line AA in FIG. 1, and FIG. 3 is an enlarged schematic view of the vicinity of the beam waist in FIG. FIG. FIG. 4 is an enlarged view of the vicinity of the beam waist when the beam waist is adjusted to be at a position shallower than half the thickness t from the surface 11 of the sapphire substrate. In FIG. 1 and FIG. 2, reference numeral 10 denotes a hard and brittle material plate, for example, a sapphire substrate, and reference numeral 15 shown by a dotted line on a surface 11 on which a laser beam is incident. As shown in FIGS. 1 and 2, for example, a 400 fs pulse generated from, for example, a rare earth doped mode-locked fiber laser-based femtosecond laser device having a wavelength that does not cause linear absorption by the sapphire substrate 10. A short optical pulse laser beam 30 having a width and a repetition period of 100 kHz is used. The short optical pulse laser beam 30 is incident on the front surface 11 after being narrowed down by the condenser lens 200 so that the waist 31 of the beam 30 is positioned inside the substrate 1. In this case, before starting the division processing, the optical bench 64 is finely moved in the Z-axis direction by a driving unit 61 of a processing apparatus (FIG. 6) to be described later, and the distance between the surface 11 of the sapphire substrate and the condenser lens 200. Is adjusted so that the beam waist 31 of the laser beam 30 exists at a position deeper than half the thickness t in the depth direction from the surface 11 of the substrate 10.

The setting of the short light pulse laser beam 30 collected by the condenser lens 200 to the position in the direction (depth direction) distance d ₀ (> t / 2) perpendicular to the surface 11 of the waist 31 is first performed as an illumination light source. Is used to set the focal point of the condenser lens 200 to the surface 11 of the substrate 10 and then move the condenser lens 200 to the surface 11 side of the substrate 10 by a predetermined distance d. The relationship between the predetermined distances d and d ₀ depends on the wavelength λ of the laser beam 30 and the refractive index n (λ) of the substrate 10.
d ₀ = n (λ) d (1)
It is expressed. For example, when the thickness of the substrate 10 is 100 μm and the waist 31 is set at a position of 80 μm from the surface 11 in the depth direction, d ₀ = 80 μm, n (λ) = 1.75, and d = 45.7 μm. What is necessary is just to move the condensing lens 200 to the surface 11 side about 46 micrometers.

The optical axis OA of the short optical pulse laser beam 30 is in the direction indicated by the arrow D (see FIG. 1) with a predetermined processing speed V along the planned division line 15 (indicated by a dotted line in FIG. 1) assumed on the surface 11 of the sapphire substrate 10. 2 is moved relative to the surface 11 of the substrate 10 in a direction perpendicular to the optical axis OA and parallel to the paper surface. At this time, as shown in FIG. 3B, each pulse of the pulsed laser beam 30 is in the direction of arrow D so that the solid spot 31 and the dotted spot 31 ′ (spot by the pulse immediately before the spot 31) overlap. Moving speed (processing speed) V is set. Here, the interval γ between the center line CL of the spot 31 indicating the degree of overlap and the center line CL ′ of the spot 31 ′ is uniquely determined by the pulse repetition frequency R and the processing moving speed V of the laser beam 30. That is, γ is
γ = V / R (2)
It is expressed. For example, if the diameter of the spots 31, 31 ′ is 7 μm and γ = 0.4 μm, when R = 100 kHz, V = 40 mm / s. That is, by setting V = 40 mm / s, the center CL is irradiated with 9 pulses of laser beam in an overlapping manner.

Next, with reference to FIG. 3, a description will be given of a waist region and a mechanism in which light-induced breakdown due to, for example, multiphoton absorption occurs in the vicinity of the back surface of the hard and brittle material plate separated from the waist region in the depth direction. As shown in FIG. 3, for example, when the waist 31 is located at a position d ₀ (> t / 2) from the front surface 11 and away from the rear surface by the Rayleigh range Zr, it is considered as follows.

Now, as shown in FIG. 3, S ₁ and range of [delta] ₁ from the lower end of the range waist region (range hatched with diagonal lines) S _0, S ₀ of the upper and lower [delta] ₀ from the waist _31, the range of [delta] ₁ from the top If the range of δ ₂ from the lower end of S ′ ₁ and S ₁ is S ₂ , and the range of δ ₂ from the upper end of S ′ ₁ is S ′ ₂ , the intensity (power per unit area) of the laser beam 30 is naturally S ₀ is the highest, followed by S ₁ and S ′ ₁ , S ₂ and S ′ ₂ . Therefore, if the intensity of the laser beam is, for example, about 5 TW / cm ² , the multiphoton in the order of S ₀ → S ₁ , S ′ ₁ → S ₂ , S ′ ₂ if the crystal of the sapphire substrate is under the same constraint condition. It is considered that light-induced fracture processing by absorption is performed. However, as shown in FIG. 3, the lower end of S ₂ is in contact with the free space, and the binding is weak, and the vapor and particles generated by light-induced breakdown easily escape to the free space, so that S ₂ is easily processed. On the other hand, S ₀ , S ₁ , S ′ ₁ , S ′ ₂ are isolated from free space, are strongly bound, and are difficult to be processed because vapors and particles generated by light-induced destruction cannot escape. . Therefore, it is considered that S ₂ is first processed and then S ₀ having the highest strength is processed. That is, light-induced destruction marks 13 and 14 are formed in the waist region S ₀ and in the S ₂ region near the back surface spaced from the waist region S _{0 in the} depth direction. Incidentally, the processing of S _0, since not proceed and no escape of vapor or particles, would need to S ₁ region is also processed a little. Therefore, instead of the non-processing region where S ₁ region is not at all processed, a region that is partially processed.

Here, the Rayleigh range Zr will be described. The Rayleigh range is a distance in which the beam diameter when a single-mode laser beam (Gaussian beam) is condensed by the condenser lens is within √2 times the spot diameter at the waist 31, and as shown in FIG. Beyond the range, the beam grows rapidly. Therefore, the intensity of the beam within the Rayleigh range is high, and the beam intensity rapidly decreases after exceeding the Rayleigh range. Therefore, the position of the beam waist 31 is preferably within the Rayleigh range from the back surface 12. The Rayleigh range Zr is 2a when the diameter of the laser beam incident on the condenser lens 200 is 2a.
Zr = (4λ / π) (1 / 2a) ² (3)
It is expressed. Here, for example, when condensing a laser beam having a wavelength λ = 1.45 μm, when NA = 0.65, if f = 4 mm and 2a = 3 mm are substituted, Zr = 2.4 μm. When NA = 0.24, if f = 20 mm and 2a = 3 mm are substituted, Zr = 59 μm. Therefore, it can be seen that the larger NA is, the smaller Zr is, and the smaller NA is, the larger Zr is. Therefore, when the NA of the condensing lens is 0.3 or less, the above-described waist region S ₀ and the back surface region S ₂ are photoinduced even when the thickness t of the hard and brittle material plate to be divided is on the order of 100 μm. Destruction marks can be formed.

Next, with reference to FIG. 4, a description will be given of a waist region and a mechanism in which light-induced breakdown due to multiphoton absorption occurs in the vicinity of the back surface of the hard and brittle material plate separated in the depth direction from the waist region. FIG. 4 shows a case where the focal position of the condenser lens is adjusted so that the waist of the laser beam exists at a position shallower than the inside t / 2 of the hard and brittle material plate. As shown in FIG. 4, for example, when the waist 31 is located d ₀ (<t / 2) away from the front surface 11 and (Zr + Δ) away from the back surface, it can be considered as follows.

Now, as shown in FIG. 4, the range from the lower end of the [delta] ₁ of the upper and lower [delta] ranges waist region _S 0, _{S 0 0} West 31 _{S 1,} the range of [delta] ₁ from the upper end _S '1, the _{S 1} Assuming that the range of δ ₂ from the lower end is S ₂ and the range of Δ from the lower end of S ₂ is S ₃ , naturally the intensity (power per unit area) of the laser beam 30 is highest in S ₀ , and then S ₁ and S The order is' ₁ , S ₂ , S ₃ . Therefore, if the crystals of the sapphire substrate are under the same constraining conditions, it is considered that they are processed in the order of S ₀ → S ₁ , S ′ ₁ → S ₂ → S ₃ . However, as shown in FIG. 4, in the middle of S ′ ₁ , the lower end of S ₃ is in contact with the free space and the binding is weak, and the vapor and particles generated by light-induced breakdown easily escape to the free space. ′ ₁ and S ₃ are easily processed. On the other hand, S ₀ , S ₁ , and S ₂ are isolated from free space, are strongly bound, and are difficult to process because vapors and particles generated by light-induced destruction cannot escape. Therefore, it is considered that S ′ _{1 and} S ₃ are processed first, S ₀ having the highest strength, and then the lower part of S ₂ are processed. That is, photo-induced destruction marks are formed in the waist region S ₀ , a part of S ′ ₁ extending from the waist region S ₀ to the front surface 11, and a part of S ₃ and S ₂ near the back surface. Become.

  Next, the internal light-induced breakdown marks 13 and the light-induced breakdown marks 14 connected to the back surface or the light-induced breakdown marks 13 ′ connected to the front surface and the back surface of the sapphire substrate 30 formed along the planned dividing line by the above-described split processing method. The process of dividing or cleaving via the light-induced fracture mark 14 'will be described with reference to FIG. In FIG. 5, 10 is a sapphire substrate, and 14 and 14 ′ are light-induced destruction traces connected to the back surface formed along the planned division lines. First, as shown in FIG. 6, hold both side portions (portions indicated by white arrows 17 in FIG. 5) of the light-induced breakdown marks 14 and 14 ′ formed on the back surface 12 along the planned dividing line of the sapphire substrate 10. Alternatively, while pressing, a cutting edge such as a break blade (not shown) is pressed against the portion corresponding to the fracture marks 14 and 14 'on the surface 11 of the substrate 10 (the portion indicated by the white arrow 18 in FIG. 5). Thus, strain stress is concentrated on the fracture marks 14 and 14 ′, and the substrate 10 can be divided or cleaved easily and easily along the division line.

  Next, an example of a division processing apparatus for carrying out the division processing method of the present invention will be described with reference to FIG. The division processing apparatus includes a laser device 50 that generates a laser beam 30, a shutter 54 that controls the laser beam 30 on and off, a dichroic mirror 55 that transmits the laser beam 30, and a laser beam 30 that transmits the dichroic mirror 55. A condensing lens 200 for condensing, and a groove a on which the hard and brittle material plate 10 of the workpiece to which the laser beam 30 condensed by the condensing lens 200 is incident from the Z-axis direction is attached. The suction table 57, an X-axis stage 71 for moving the suction table 57 in the X-axis direction, a Y-axis stage 72 for moving the suction table 57 in the Y-axis direction orthogonal to the X-axis direction, and the suction table 57 Includes a Z-axis stage 73 for moving in the Z-axis direction orthogonal to the X-axis and Y-axis directions, and a control personal computer 80.

  The division processing apparatus further includes an observation light source 63 that generates visible light for illuminating the hard and brittle material plate 10 adsorbed on the adsorption table 57 with visible light, and 90 visible light from the observation light source 63. A half mirror 56 that is bent and incident on a dichroic mirror 55, a condenser lens 200, a dichroic mirror 55, and a CCD camera 62 that images the wafer 100 via the half mirror 56 are provided.

  The split processing apparatus further includes an optical bench 64 in which a laser device 50, a shutter 54, a dichroic mirror 55, a condenser lens 200, a half mirror 56, an observation light source 63, and a CCD camera 62 are arranged, and the optical bench 64 in the Z-axis direction. A drive unit 61 for driving.

  The shutter 54, the observation light source 63, the CCD camera 62, and the drive unit 61 are connected to the control personal computer 80. The shutter 54, the observation light source 63 is turned on and off, the imaging data processing of the CCD camera 62, and the drive unit 61. Drive control is performed. Therefore, the waist position (focus position) 31 of the laser beam 30 can be imaged by the CCD camera 62 and observed on the monitor of the control personal computer 80 in accordance with a command from the control personal computer 80.

  The laser device 50 includes an oscillation module 51, a fiber 53 that propagates the laser light oscillated from the oscillation module 51, an amplification module 52 that amplifies the laser light propagated through the fiber 53, and the laser light from the oscillation module 51. And a laser controller 54 for controlling the output, the pulse width, and the repetition frequency. The laser controller 54 is connected to the personal computer 80 and operates according to a command from the personal computer 80. The oscillation module 51 receives a Yb-doped mode-locked fiber laser, a fiber stretcher that receives a pulsed laser beam oscillated from the fiber laser and outputs a stretched pulsed laser beam, and a stretched pulsed laser beam. And a fiber preamplifier that receives the pulsed laser light that has been thinned out and outputs the amplified pulsed laser light. The amplification module 52 receives the pulse laser light from the oscillation module 51 through the fiber 53 and further amplifies it, and a compressor that receives the amplified pulse laser light and outputs the compressed pulse laser light. . The amplification module 52 is fixed to the optical bench 64 so that the laser beam 30 is emitted in the Z-axis direction. The amplification module 52 emits a laser beam 30 having a wavelength of 1045 nm, an average output of 1.2 W, a pulse width of 500 fs to 5 ps, and a repetition frequency of 50 to 1000 kHz.

  In addition to the above, the laser device 50 only needs to have a wavelength of 300 to 1800 nm, a pulse width of 10 fs to 10 ps, and a repetition frequency of 50 kHz to 10 MHz. For example, a reproduction amplification type Ti: sapphire laser device or the like may be used.

  The laser device 50 desirably has a performance of a wavelength of 700 to 1600 nm, a pulse width of 50 fs to 2 ps, and a repetition frequency of 50 to 300 kHz.

  Hereinafter, an operation procedure of the division processing apparatus having the above configuration will be described. First, the shutter 54 is closed, and the laser device 50 is operated at a predetermined repetition rate. Next, the oscillation module 51 is controlled by the controller 54 so that the pulse energy of the laser beam 30 emitted from the condenser lens 200 by opening the shutter 54 becomes a predetermined value.

  Next, the shutter 54 is closed, and the brittle material plate body is arranged so that the direction of the division line 15 on the suction table 57 is in the Y-axis direction and the division line 15 is located immediately above the groove i of the suction table 57. 10 is set. Next, while turning on the observation light source 63 and observing the surface 11 of the hard and brittle material plate 10 with the CCD camera 62, the X-axis stage 71 and the Y-axis are set so that the focal position coincides with the division line 15 on the surface 11. The stage 72 is moved, and the optical bench 64 is finely moved in the Z-axis direction by the drive unit 61.

Next, the optical bench 64 is moved by the drive unit 61 so that the waist position 31 is located at a predetermined depth d ₀ (<t / 2, where t is the thickness of the plate 10) from the surface 11. Approach (lower) the surface 11.

  Next, the shutter 54 is turned on and the plate 10 is moved at a predetermined moving speed V at which the beam spot overlaps in the Y-axis direction on the Y-axis stage 72 while condensing and irradiating the laser beam 30 to the waist position. When the distance is moved, the shutter 54 is turned off.

Debris such as gas and particles is released in the process of forming the light-induced destruction traces continuous with the back surface 12, but the following effects are exhibited by matching the planned dividing line and the groove of the adsorption table. 1) Debris can be efficiently removed by flowing pure water or He, N ₂ , reactive gas, etc. into the groove. 2) Optimal reaction according to the hard and brittle material plate to be divided. Chemical etching action occurs by selective use of a reactive gas (for example, SF ₆ that generates fluorine radicals) (fluorine radicals are generated by the action of plasma generated by light-induced breakdown, for example, silicon on a glass plate body Since the etching of the process proceeds chemically, the deeper processing is possible from the back to the inside. 3) The atmosphere gas requires a minimum volume. 4) The groove is evacuated to prevent debris from being scattered. It can suppress, and adhesion to the device currently formed in the hard and brittle material board can be prevented.

  Next, an example in which a sapphire substrate is divided by using the division processing method of the present invention will be described together with divided sectional photographs.

  FIG. 7 shows the result of division processing in which the focal position of the condenser lens is adjusted so that the waist of the laser beam exists at a position deeper than ½ of the thickness of the sapphire substrate.

Processing conditions Processing object: Sapphire substrate (thickness t = 100 μm)
Laser device: Yb-doped mode-locked fiber laser-based femtosecond laser device wavelength: 1.045 μm
Pulse width: 3.7ps
Pulse repetition frequency: 200 kHz
Average output: 1.2W
Beam diameter: 3mm
Condensing lens: numerical aperture 0.16, focal length 15.4 mm
Pulse energy after passing through the condenser lens: 1.5 μJ
Laser beam incident surface: C surface of sapphire crystal Laser beam incident direction: Waist position perpendicular to C surface: 78.8 μm from the surface (incident surface) to the inside in the thickness direction (collected after adjusting the focal point of the condenser lens to the incident surface) Positional Rayleigh range (calculated value when the optical lens is brought closer to the incident surface by 45 μm): 35.1 μm (calculated value)
Movement speed: 40mm / s
Beam waist (spot) diameter: 6.8 μm (calculated value)
Spot overlap degree (spot moving distance to the next pulse): 0.2 μm (calculated value)
Number of incident pulses to the center of the spot: 17 (calculated value)
Beam waist strength: 1.1 TW / cm ² (calculated value)

  FIG. 7 is a photomicrograph of a divided surface obtained by performing division processing under the above-described processing conditions and then pressing and pressing the cutting edge of the break blade. The pushing amount of the break blade at this time was 100 μm. It can be seen that a non-machined area (cleavage surface), a machined area (light-induced fracture marks in the waist area), a non-machined area (partially machined area), and a machined area connected to the back surface are formed from the front surface.

  FIG. 8 shows the result of division processing in which the focal position of the condenser lens is adjusted so that the waist of the laser beam is present at a position shallower than ½ of the thickness of the sapphire substrate.

Processing conditions Processing object: Sapphire substrate (thickness t = 100 μm)
Laser device: Yb-doped mode-locked fiber laser-based femtosecond laser device wavelength: 1.045 μm
Pulse width: 480fs
Pulse repetition frequency: 200 kHz
Average output: 1.2W
Beam diameter: 3mm
Condenser lens: numerical aperture 0.25, focal length 11.0 mm
Pulse energy after passing through the condenser lens: 1.5 μJ
Laser beam incident surface: C surface of sapphire crystal Laser beam incident direction: Waist position perpendicular to C surface: 17.5 μm from the surface (incident surface) to the inside in the thickness direction (collected after adjusting the focal point of the condenser lens to the incident surface) Positional Rayleigh range (calculated value when the optical lens is brought closer to the incident surface by 10 μm): 17.9 μm (calculated value)
Movement speed: 10mm / s
Beam waist (spot) diameter: 4.9 μm (calculated value)
Spot overlap degree (spot moving distance to next pulse): 0.05μm (calculated value)
Number of incident pulses to the center of the spot: 46 (calculated value)
Beam waist strength: 16.6 TW / cm ² (calculated value)

  FIG. 8 is a photomicrograph of a divided surface obtained by performing division processing under the above processing conditions and then pressing and pressing the cutting edge of the break blade. The pushing amount of the break blade at this time was 100 μm. It can be seen that there are formed a processing area (photo-induced fracture marks in the waist area) continuous from the front surface to the front surface, a non-processing area and a processing area continuous from the back surface.

Since a so-called ultrashort pulse laser (femtosecond pulse laser) is used for the laser device, the processing principle is light-induced breakdown, which is adiabatic processing. Therefore, generation of cracks is suppressed in the processing area connected to the back surface, and the bending strength of the divided plate body is improved. In addition, internal processing performed simultaneously or processing connected to the surface can be efficiently performed even with a low average power because the pulse width is short. As a result, it is possible to suppress damage to the device and the like due to excess laser light that passes through the plate. In addition, when a near-infrared femtosecond pulse laser having a center wavelength of 1 μm or more is used, the thermal effect can be further suppressed because of high transparency to the plate and the semiconductor device. Further, when a femtosecond fiber laser device using an optical fiber for an oscillator or an amplifier is used, it has a repetition frequency of 100 kHz or more. Therefore, a large energy femto by a regenerative amplification method including a conventional titanium sapphire crystal having a repetition frequency of about 1 kHz. Compared to the second laser device, high-speed processing is possible. Further, since the beam quality is excellent (M ² = 1.3), the beam can be condensed to near the diffraction limit, and the processing shape accuracy is improved.

  Very likely to be used in the semiconductor industry.

It is a schematic diagram explaining the division | segmentation processing method of this invention. FIG. 2 is a partially cutaway sectional view taken along line AA in FIG. 1. It is the figure which expanded the beam waist vicinity of FIG. 2, and was shown typically. It is an enlarged view of the vicinity of the beam waist when the beam waist is adjusted to be at a position shallower than half of its thickness from the surface of the sapphire substrate. It is a schematic diagram explaining the principle which divides | segments the hard-brittle material board divided | segmented by the method of this invention. It is a block diagram which shows the division processing apparatus which can implement the division processing method of this invention. It is the microscope picture of the division surface of Example 1 which adjusted and adjusted the focus position of the condensing lens so that the waist of a laser beam may exist in the position deeper than 1/2 of the thickness of a sapphire substrate. It is the microscope picture of the division surface of Example 2 which adjusted and adjusted the focus position of the condensing lens so that the waist of a laser beam may exist in a position shallower than 1/2 of the thickness of a sapphire substrate.

Explanation of symbols

10... Hard and brittle material plate 11... Hard and brittle material plate surface 12... Hard and brittle material plate back surface 15. 30 ······ Short pulse laser beam 31 ··· Waist 200 ··· Condensing lens OA ··· Optical axis of laser beam

Claims (3)

When a short optical pulse laser beam having a wavelength that is optically transparent to a hard and brittle material plate having a thickness t is incident on the surface of the hard and brittle material plate through a condenser lens,
The focal position of the condensing lens is adjusted so that the waist of the laser beam exists at a position shallower or deeper than the inside t / 2 of the hard and brittle material plate, and the repeated short optical pulse laser beam While moving the optical axis of the laser beam relative to the hard and brittle material plate along a predetermined split line so as to be incident on the surface of the material plate, the laser beam is moved to the hard plate. A step of causing light-induced breakdown near the back surface of the hard and brittle material plate that is spaced in the depth direction from the waist region each time it is incident on the surface of the brittle material plate. A method for dividing a hard and brittle material plate.   2. The method for dividing a hard and brittle material plate according to claim 1, wherein the condensing lens has a numerical aperture of 0.3 or less.   The position shallower than t / 2 is within the Rayleigh range from the surface of the hard and brittle material plate, and the position deeper than t / 2 is within the Rayleigh range from the back surface of the hard and brittle material plate. The division | segmentation processing method of the hard-brittle material board of Claim 1 or 2.

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