JP2003266185A - Method of laser beam machining - Google Patents

Method of laser beam machining

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Publication number
JP2003266185A
JP2003266185A JP2002067406A JP2002067406A JP2003266185A JP 2003266185 A JP2003266185 A JP 2003266185A JP 2002067406 A JP2002067406 A JP 2002067406A JP 2002067406 A JP2002067406 A JP 2002067406A JP 2003266185 A JP2003266185 A JP 2003266185A
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Japan
Prior art keywords
semiconductor substrate
modified region
planned cutting
cutting portion
cutting
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP2002067406A
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Japanese (ja)
Other versions
JP4050534B2 (en
Inventor
Kenji Fukumitsu
Fumitsugu Fukuyo
文嗣 福世
憲志 福満
Original Assignee
Hamamatsu Photonics Kk
浜松ホトニクス株式会社
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Priority to JP2002067406A priority Critical patent/JP4050534B2/en
Priority claimed from MYPI20030866 external-priority patent/MY148590A/en
Publication of JP2003266185A publication Critical patent/JP2003266185A/en
Application granted granted Critical
Publication of JP4050534B2 publication Critical patent/JP4050534B2/en
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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/0604Shaping the laser beam, e.g. by masks or multi-focusing by a combination of beams
    • B23K26/0619Shaping the laser beam, e.g. by masks or multi-focusing by a combination of beams with spots located on opposed surfaces of the workpiece
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36Removing material
    • B23K26/40Removing material taking account of the properties of the material involved
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/50Working by transmitting the laser beam through or within the workpiece
    • B23K26/53Working by transmitting the laser beam through or within the workpiece for modifying or reforming the material inside the workpiece, e.g. for producing break initiation cracks
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2101/00Articles made by soldering, welding or cutting
    • B23K2101/36Electric or electronic devices
    • B23K2101/40Semiconductor devices
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00Materials to be soldered, welded or cut
    • B23K2103/50Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of laser beam machining by which the cutting force for cutting a semiconductor substrate is kept constant and a part to be cut is formed on the semiconductor substrate. <P>SOLUTION: The method of laser beam machining is characterized in that the method is provided with a process in which a part to be cut in parallel 9a is formed in the semiconductor substrate 1 by irradiating the semiconductor substrate 1 with laser light by focusing on the inside of the semiconductor substrate 1 and forming a fusion-processed region by a multi-photon absorption inside the semiconductor substrate 1, and a process in which a part to be vertically cut 9b is formed inside the semiconductor substrate 1, and the formed density of the fusion-processed region at the part to be vertically cut 9b is larger than the formed density of the fusion-processed region at the part to be cut in parallel 9a so that a cutting force for cutting the semiconductor substrate 1 along the part to be cut in parallel 9a and a cutting force for cutting the semiconductor substrate 1 along the part to be vertically cut 9b become equal. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing method used for cutting a semiconductor substrate such as a silicon wafer.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a semiconductor substrate such as a silicon wafer is cut into a lattice shape to obtain semiconductor chips. A scribe line is provided on the surface of the semiconductor substrate by a diamond point tool or the like. A method is known in which a knife edge is pressed against the back surface of the semiconductor substrate along the scribe line to break the semiconductor substrate (breaking).

In breaking the semiconductor substrate, the semiconductor substrate is cut into strips along scribe lines in one direction, and then the semiconductor substrates cut into strips are simultaneously cut along scribe lines in the other direction. Is common.

In order to suppress the occurrence of chipping and cracking and cut the semiconductor substrate by breaking with high accuracy, it is necessary to set extremely severe conditions such as keeping the pressing force of the knife edge to a necessary minimum. Becomes

[0005]

However, compared with the case where the semiconductor substrate is cut into strips along the scribe line in one direction, the semiconductor substrate cut into strips is simultaneously cut along the scribe line in the other direction. In that case, a larger cutting force is required, and therefore, in order to realize highly accurate cutting of the semiconductor substrate by braking, the extremely severe condition setting described above must be performed every time the direction of the scribe line changes.

Therefore, the present invention has been made in view of such circumstances, and a laser processing method capable of forming a planned cutting portion on the semiconductor substrate, which can keep the cutting force for cutting the semiconductor substrate constant. The purpose is to provide.

[0007]

In order to achieve the above-mentioned object, a laser processing method according to the present invention is performed by irradiating a laser beam with a converging point on the inside of a semiconductor substrate so that the inside of the semiconductor substrate is exposed. Forming a modified region by multiphoton absorption,
Multi-photon absorption is performed inside the semiconductor substrate by irradiating the inside of the semiconductor substrate with a laser beam by aligning the converging point inside the semiconductor substrate with the step of forming the first cut portion in the first direction in the modified region. Forming a modified region according to 1. and forming a second planned cutting portion in the second direction intersecting the first direction with the modified region, the semiconductor along the first planned cutting portion. Modification in the first planned cutting portion so that the first cutting force for cutting the substrate and the second cutting force for cutting the semiconductor substrate along the second planned cutting portion become equal to each other. The formation state of the region and the formation state of the modified region in the second planned cutting portion are different from each other.

According to this laser processing method, laser light is irradiated to the inside of the semiconductor substrate so that the focal point is aligned, and a phenomenon called multiphoton absorption is generated inside the semiconductor substrate to form a modified region. First crossing each other in the modified area
The first planned cutting portion and the second planned cutting portion are formed in the direction and the second direction, respectively. When the modified region is formed inside the semiconductor substrate, cracks occur in the thickness direction of the semiconductor substrate starting from the modified region.Therefore, the semiconductor substrate is cut along the planned cutting portion with a relatively small cutting force. Can be cut. And the magnitude of this cutting force is
It changes depending on the state of formation of the modified region in the planned cutting portion. Therefore, the formation state of the modified region in the first planned cutting portion and the formation state of the modified region in the second planned cutting portion are made different to cut the semiconductor substrate along the first planned cutting portion. Therefore, it is possible to control the first cutting force for cutting and the second cutting force for cutting the semiconductor substrate along the second planned cutting portion to be equal to each other. That is, it is possible to form, in the semiconductor substrate, a planned cutting portion capable of keeping the cutting force constant for cutting the semiconductor substrate.

The cutting force means, for example, bending stress or shearing stress is generated in the semiconductor substrate along the planned cutting portion of the semiconductor substrate, or thermal stress is generated by giving a temperature difference to the semiconductor substrate. The force required to cut the semiconductor substrate. Further, the converging point is a place where the laser light is condensed. And the planned cutting part is
The modified region may be formed by being continuously formed, or may be formed by the modified region being intermittently formed.

As the state of formation of the modified region in the above-mentioned planned cutting portion, for example, the density of the modified region, the size of the modified region, and the region from the surface of the semiconductor substrate to the modified region are as follows. There is a distance.

That is, in the above laser processing method, when the state of formation of the modified region in the first planned cutting portion and the state of formation of the modified region in the second planned cutting portion are made equal, the first cutting force is increased. In the case where the second cutting force is larger than the above, it is preferable to increase the formation density of the modified region in the second planned cutting portion compared to the formation density of the modified region in the first planned cutting portion. .

This is because inside the semiconductor substrate, cracks occur in the thickness direction of the semiconductor substrate starting from the modified region. Therefore, if the formation density of the modified region in the planned cutting part is increased, the planned cutting part is cut. This is because the cutting force for cutting the semiconductor substrate along the can be reduced. In addition,
The formation density of the modified region in the planned cutting portion means the ratio of the modified region to the semiconductor substrate in the planned cutting portion.

Further, in the above laser processing method, when the state of formation of the modified region in the first planned cutting portion and the state of formation of the modified region in the second planned cutting portion are made equal, the first cutting force is increased. In the case where the second cutting force is larger than the above, it is preferable to make the size of the modified region in the second planned cutting portion larger than the size of the modified region in the first planned cutting portion. .

This is because inside the semiconductor substrate, cracks occur in the thickness direction of the semiconductor substrate starting from the modified region. Therefore, if the size of the modified region in the planned cutting part is increased, the planned cutting part is cut. This is because the cutting force for cutting the semiconductor substrate along the can be reduced. In addition,
The size of the modified region mainly means the length of the modified region in the thickness direction of the semiconductor substrate.

Further, in the above laser processing method,
The first cutting force and the second cutting force generate bending stress in the semiconductor substrate, and the formation state of the modified region in the first planned cutting portion and the modified region in the second planned cutting portion When the second cutting force is larger than the first cutting force when the formation state of the first cutting force is equal to that of the first cutting force, the first cutting force from the surface of the semiconductor substrate on the side pulled by the bending stress caused by the first cutting force. It is preferable that the distance from the surface of the semiconductor substrate on the side pulled by the bending stress due to the second cutting force to the modified region in the second planned cutting portion is smaller than the distance to the modified region in the planned cutting portion. .

This is because when a bending stress is generated in the semiconductor substrate, the closer the modified region is to the surface of the semiconductor substrate that is pulled by this bending stress (that is, the smaller the distance from the surface to the modified region is). This is because a larger tensile stress acts on the modified region, so that the cutting force that causes bending stress can be reduced.

In the above laser processing method, the semiconductor substrate is irradiated with laser light under the condition that the peak power density at the condensing point of the laser light is 1 × 10 8 (W / cm 2 ).
By setting the pulse width to 1 μs or less, the modified region including the melt-processed region can be formed inside the semiconductor substrate. That is, the inside of the semiconductor substrate is locally heated by multiphoton absorption, and this heating forms the melt-processed region only inside the semiconductor substrate. This melting treatment area is an example of the above-mentioned modification area.

In the laser processing method according to the present invention, a modified region is formed inside the semiconductor substrate by irradiating the inside of the semiconductor substrate with a focusing point and irradiating with laser light. Therefore, a modified region is formed inside the semiconductor substrate by irradiating a laser beam with a step of forming the first planned cutting portion in the first direction in the inside of the semiconductor substrate by aligning a focusing point. A step of forming a second planned cutting part in a second direction intersecting the first direction with the modified region, and a formation state of the modified region in the first planned cutting part and a second planned cutting. It is characterized in that the state of formation of the modified region in the section is different from each other. The modified region may be a melt-processed region.

According to this laser processing method, a laser beam is irradiated to the inside of the semiconductor substrate so that the focal point is aligned with the laser beam to form a modified region inside the semiconductor substrate. The first direction in the first direction and the first direction in the second direction
And a second planned cutting part is formed. Therefore, by changing the formation state of the modified region in the first planned cutting portion and the formation state of the modified region in the second planned cutting portion, for example, the semiconductor substrate is formed along the first planned cutting portion. Various controls are possible, such as making the first cutting force for cutting and the second cutting force for cutting the semiconductor substrate along the second planned cutting portion equal. However, the formation of the modified region may be caused by multiphoton absorption or may be caused by other factors.

That is, in the above laser processing method, the first cutting force for cutting the semiconductor substrate along the first planned cutting portion and the cutting of the semiconductor substrate along the second planned cutting portion are used. The formation state of the reformed region in the first planned cutting portion and the formation state of the reformed region in the second planned cutting portion can be different from each other so that the second cutting force of No. 1 becomes the same.

Further, in the above laser processing method, the formation density of the modified region in the first planned cutting portion may be different from the formation density of the modified region in the second planned cutting portion.

Further, in the above laser processing method,
The size of the modified region in the first planned cutting portion may differ from the size of the modified region in the second planned cutting portion.

Further, in the laser processing method according to the present invention, the second planned cutting portion is for cutting the semiconductor substrate along the first planned cutting portion and then cutting the cut semiconductor substrate at the same time. It is preferably one. This is because a greater cutting force is required when simultaneously cutting the semiconductor substrates that have been cut than when cutting the uncut semiconductor substrate.

Further, in the laser processing method according to the present invention, an orientation flat is formed on the semiconductor substrate, the first direction is parallel to the longitudinal direction of the orientation flat, and the second direction is the orientation flat. Is preferably perpendicular to the longitudinal direction of. This is because a larger cutting force is required in the case of cutting perpendicularly to the longitudinal direction of the orientation flat than in the case of cutting parallel to the longitudinal direction of the orientation flat.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to the drawings. In the laser processing method according to the present embodiment, a laser beam is irradiated to the inside of the semiconductor substrate so that the focal point is aligned, and a modified region due to multiphoton absorption is formed inside the semiconductor substrate to form a planned cutting portion. .
Therefore, this laser processing method, in particular, multiphoton absorption will be described first.

When the photon energy hν is smaller than the absorption band gap E G of the material, it becomes optically transparent. Therefore, the condition under which absorption occurs in the material is hν> E G. However, even if it is optically transparent, if the intensity of the laser light is made extremely high, the condition of nhν> E G (n = 2, 3, 4, ...
・) Absorption occurs in the material. This phenomenon is called multiphoton absorption. In the case of a pulse wave, the intensity of the laser light is determined by the peak power density (W / cm 2 ) at the condensing point of the laser light. For example, the multiphoton is generated under the condition that the peak power density is 1 × 10 8 (W / cm 2 ) or more. Absorption occurs. The peak power density is (energy per pulse of laser light at the condensing point) ÷
It is calculated by (beam spot cross-sectional area of laser light × pulse width). Further, in the case of a continuous wave, the intensity of the laser light is determined by the electric field intensity (W / cm 2 ) at the condensing point of the laser light.

The principle of laser processing according to this embodiment utilizing such multiphoton absorption will be described with reference to FIGS. 1 is a plan view of the semiconductor substrate 1 during laser processing, FIG. 2 is a sectional view taken along line II-II of the semiconductor substrate 1 shown in FIG. 1, and FIG. 3 is a plan view of the semiconductor substrate 1 after laser processing. FIG. 4 is a plan view, and FIG. 4 shows the semiconductor substrate 1 shown in FIG.
4 is a sectional view taken along line IV-IV, FIG. 5 is a sectional view taken along line VV of the semiconductor substrate 1 shown in FIG. 3, and FIG. 6 is a plan view of the cut semiconductor substrate 1.

As shown in FIGS. 1 and 2, the semiconductor substrate 1
The surface 3 has a desired planned cutting line 5 for cutting the semiconductor substrate 1. The planned cutting line 5 is an imaginary line extending in a straight line (a line may actually be drawn on the semiconductor substrate 1 to form the planned cutting line 5). In the laser processing according to the present embodiment, the modified region 7 is formed by irradiating the semiconductor substrate 1 with the laser light L by aligning the focus point P inside the semiconductor substrate 1 under the condition that multiphoton absorption occurs. The converging point means the laser beam L
Is the point where the light is collected.

By moving the laser light L relatively along the planned cutting line 5 (that is, along the direction of arrow A), the condensing point P is moved along the planned cutting line 5. As a result, as shown in FIG. 3 to FIG.
Is formed only inside the semiconductor substrate 1 along the planned cutting line 5, and the modified region 7 forms the planned cutting portion 9. In the laser processing method according to this embodiment, the semiconductor substrate 1 does not generate the modified region 7 by absorbing the laser light L to heat the semiconductor substrate 1. The laser light L is transmitted through the semiconductor substrate 1 to cause multiphoton absorption inside the semiconductor substrate 1 to form the modified region 7. Therefore, the surface 3 of the semiconductor substrate 1 hardly absorbs the laser light L, so that the surface 3 of the semiconductor substrate 1 is not melted.

When the semiconductor substrate 1 is cut, if the starting point is at the cutting point, the semiconductor substrate 1 is broken from the starting point, so that the semiconductor substrate 1 can be cut with a relatively small force as shown in FIG. Therefore, the surface 3 of the semiconductor substrate 1
The semiconductor substrate 1 can be cut without causing unnecessary cracks.

There are two possible ways of cutting the semiconductor substrate starting from the planned cutting part. One is a case where an artificial force is applied to the semiconductor substrate after the planned cutting portion is formed, so that the semiconductor substrate is cracked starting from the planned cutting portion and the semiconductor substrate is cut. This is cutting, for example, when the thickness of the semiconductor substrate is large. The artificial force is applied, for example, to apply a bending stress or a shear stress to the semiconductor substrate along the cut portion of the semiconductor substrate, or to generate a thermal stress by giving a temperature difference to the semiconductor substrate. That is. The other one is a case in which, by forming the planned cutting portion, the semiconductor substrate is naturally broken in the cross-sectional direction (thickness direction) of the semiconductor substrate starting from the planned cutting portion, and as a result, the semiconductor substrate is cut. . This can be achieved, for example, when the thickness of the semiconductor substrate is small, by forming the planned cutting portion by one row of modified regions, and when the thickness of the semiconductor substrate is large, a plurality of regions are formed in the thickness direction. This is possible because the planned cutting portion is formed by the modified regions formed in rows. Even in the case of this natural breakage, the part to be cut does not have a crack that extends to the surface of the part corresponding to the part where the part to be cut is not formed, and the part corresponding to the part where the part to be cut is formed. Since only the cleaving can be performed, the cleaving can be controlled better. In recent years, since the thickness of a semiconductor substrate such as a silicon wafer tends to be thin, such a cleaving method with good controllability is very effective.

In the present embodiment, the modified region formed by multiphoton absorption includes the melt-processed region described below.

A focusing point is set inside the semiconductor substrate, and the laser beam is irradiated under the condition that the electric field intensity at the focusing point is 1 × 10 8 (W / cm 2 ) or more and the pulse width is 1 μs or less. As a result, the inside of the semiconductor substrate is locally heated by multiphoton absorption. By this heating, a melt processing region is formed inside the semiconductor substrate. The melt-processed region is a region that has been once melted and then re-solidified, a region that is just in a molten state, or a region that is in a state where it is re-solidified from the molten state, and can also be referred to as a phase-changed region or a region in which the crystal structure is changed. Also,
It can be said that the melt-processed region is a region in which one structure is changed to another structure in a single crystal structure, an amorphous structure, or a polycrystalline structure. That is, for example, a region in which a single crystal structure is changed to an amorphous structure, a region in which a single crystal structure is changed to a polycrystalline structure, or a region in which a single crystal structure is changed to a structure including an amorphous structure and a polycrystalline structure is meant. To do. When the semiconductor substrate has a silicon single crystal structure, the melt-processed region has, for example, an amorphous silicon structure. The upper limit value of the electric field strength is, for example, 1
It is × 10 12 (W / cm 2 ). The pulse width is, for example, 1n
s-200 ns is preferable.

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

(A) Semiconductor substrate: Silicon wafer (thickness 350 μm, outer diameter 4 inches) (B) Laser light source: Semiconductor laser excitation Nd: YAG laser Wavelength: 1064 nm Laser light spot cross-sectional area: 3.14 × 10 −8 cm 2 Oscillation form: Q switch pulse repetition frequency: 100 kHz Pulse width: 30 ns Output: 20 μJ / pulse Laser beam quality: TEM 00 Polarization characteristic: Linearly polarized light (C) Condensing lens magnification: 50 times N.M. A. : 0.55 Transmittance for laser light wavelength: 60% (D) Moving speed of mounting table on which semiconductor substrate is mounted: 10
0 mm / sec

FIG. 7 is a view showing a photograph of a cross section of a part of the silicon wafer cut by the laser processing under the above conditions. A melt processing region 13 is formed inside the silicon wafer 11. The size in the thickness direction of the melt-processed region 13 formed under the above conditions is 100 μm.
It is a degree.

It will be described that the melt-processed region 13 is formed by multiphoton absorption. FIG. 8 is a graph showing the relationship between the wavelength of laser light and the transmittance inside the silicon substrate.
However, the reflection components on the front surface side and the back surface side of the silicon substrate are removed, and the transmittance of only the inside is shown. The thickness t of the silicon substrate is 50 μm, 100 μm, 200 μm,
The above relationship is shown for each of 500 μm and 1000 μm.

For example, when the wavelength of the Nd: YAG laser is 1064 nm, the thickness of the silicon substrate is 500 μm.
If it is less than m, the laser light will be 80 inside the silicon substrate.
It can be seen that more than% is transmitted. Since the thickness of the silicon wafer 11 shown in FIG. 7 is 350 μm, the melt-processed region 13 by multiphoton absorption is formed near the center of the silicon wafer, that is, at a portion 175 μm from the surface. In this case, the transmittance is 90% or more when a silicon wafer having a thickness of 200 μm is referred to.
There is little absorption inside 1 and most penetrates. This means that the laser light is absorbed inside the silicon wafer 11 so that the melt processing region 13 is exposed to the silicon wafer 1.
It means that the melt-processed region 13 is formed by multiphoton absorption, not that formed inside 1 (that is, the melt-processed region is formed by normal heating with laser light). The formation of the melt-processed region by multiphoton absorption is described, for example, in No. 7 of Proceedings of the 66th Annual Meeting of the Welding Society (April 2000)
It is described in "Evaluation of processing characteristics of silicon by picosecond pulse laser" on pages 2 to 73.

The silicon wafer is cracked in the cross-sectional direction starting from the planned cutting portion formed in the melt-processed region, and the cracks reach the front surface and the back surface of the silicon wafer. Be disconnected. The crack reaching the front surface and the back surface of the silicon wafer may grow naturally, or may grow when a force is applied to the silicon wafer. When a crack naturally grows from the planned cutting part on the front surface and the back surface of the silicon wafer, when the crack grows from the molten state of the melting treatment region forming the planned cutting part, There is also a case where cracks grow when the melt-processed region forming the is solidified from a molten state. However, in both cases, the melt-processed region is formed only inside the silicon wafer, and the cut surface after cutting has the melt-processed region formed only inside as shown in FIG. 7. If the planned cutting portion is formed in the semiconductor substrate in the melt-processed region, unnecessary cracks that deviate from the planned cutting portion line are unlikely to occur at the time of cutting, which facilitates cutting control.

Here, the formation state of the melt-processed region in the planned cutting portion and the cutting force for cutting the semiconductor substrate along the planned cutting portion (hereinafter referred to as "cutting force along the planned cutting portion") The relationship will be described.

As the state of formation of the melt-processed region in the planned cutting portion, for example, the formation density of the melt-processed region, the size of the melt-processed region, and the distance from the surface of the semiconductor substrate to the melt-processed region are as follows. is there. Here, the laser light used to form the melt-processed region will be described as pulsed laser light. In addition, the melt processing area formed by one pulse of laser light is particularly referred to as a “melt processing spot”.
Let's say. Since the melt processing region is an example of the reforming region, the following description naturally applies to the reforming region.

The relationship between the formation density of the melt processing area and the cutting force will be described with reference to FIGS. 9 and 10. FIG. 9 is a view showing the planned cutting portion 9 in which the melt processing spots 15 are intermittently formed, and FIG. 10 is a view showing the melt processing spots 15.
It is a figure which shows the to-be-cut part 9 which is continuously formed.

Inside the semiconductor substrate 1, cracks occur in the thickness direction of the semiconductor substrate 1 starting from the respective melt processing spots 15, so that the melt processing spots 15 as shown in FIG.
The cutting force along the planned cutting portion 9 becomes smaller in the case where the melting treatment spots 15 are continuously formed as shown in FIG. 10 than in the case where the cutting is formed intermittently. Therefore, the melt processing area 1 in the planned cutting portion 9
If the formation density of 3 is increased, the cutting force along the planned cutting portion 9 can be reduced.

Melt processing region 1 in the planned cutting portion 9
The formation density of 3 is, for example, the repetition frequency f of the laser light.
(Hz), and at least one of the moving speed v (mm / sec) of the condensing point of the laser light with respect to the semiconductor substrate 1 can be controlled. The formation density of the melt processing region 13 in the planned cutting portion 9 can be grasped as the number of melting processing spots formed per unit length of the planned cutting portion 9, where n is the number of the melting processing spots. This is because it can be expressed as “= f / v”. Therefore, in order to increase the formation density of the melt processing region 13, the repetition frequency of the laser light may be increased, or the moving speed of the condensing point of the laser light with respect to the semiconductor substrate 1 may be decreased.

The relationship between the size of the melt processing area and the cutting force will be described with reference to FIG.

Inside the semiconductor substrate 1, cracks occur in the thickness direction of the semiconductor substrate 1 starting from the respective melt processing spots 15. However, if the melt processing spot 15 shown in FIG. Since the distance over which the cracks run to the front surface 3 or the back surface 17 of the substrate 1 runs becomes small, the cutting force along the planned cutting portion 9 becomes small. Therefore, if the size of the melt processing region 13 in the planned cutting portion 9 is increased, the cutting force along the planned cutting portion 9 can be reduced.

Melt processing region 1 in the planned cutting portion 9
The magnitude of 3 is, for example, the power of laser light (that is,
It can be controlled by adjusting the energy per pulse of laser light. FIG. 11 is a cross-sectional view of the semiconductor substrate 1 in which the laser light L having a predetermined power is condensed, and FIG. 12 is a semiconductor including a melting processing spot 15 formed by the irradiation of the laser light L shown in FIG. 3 is a sectional view of the substrate 1. FIG. A region 19 shown in FIG. 11 is a region where the electric field intensity is equal to or higher than a threshold value at which multiphoton absorption occurs due to the irradiation of the laser light L, and the size of the melting treatment spot 15 depends on the size of the region 19. On the other hand, FIG. 13 is a cross-sectional view of the semiconductor substrate 1 in which the laser light L having a power higher than that in FIG. 11 is condensed inside.
4 is a cross-sectional view of the semiconductor substrate 1 including the melting processing spot 15 formed by irradiation with the laser light L shown in FIG. Due to the increase in the power of the laser beam L, the size of the region 19 shown in FIG. 13 is larger than the size of the region 19 shown in FIG. 11, and as a result, the size of the melting treatment spot 15 shown in FIG. The size is also larger than the size of the melting processing spot 15 shown in FIG. Therefore, in order to increase the size of the melt processing region 13, the power of the laser light may be increased.

The relationship between the distance from the surface of the semiconductor substrate to the melt processing area and the cutting force will be described with reference to FIG. FIG. 15 is a diagram schematically showing a state in which the cutting force F acts on the back surface 17 of the semiconductor substrate 1.

As shown in FIG. 15, when the cutting force F acts on the back surface 17 from the back surface 17 of the semiconductor substrate 1 toward the front surface 3, bending stress acts on the semiconductor substrate 1. The cutting force F forms the surface on the side where the surface 3 of the semiconductor substrate 1 is pulled, but the melt processing spot 1 having a large distance from the surface 3
As compared with 5a, the melt-processed spot 15b having a smaller distance from the surface 3 has a larger tensile stress. Therefore, when the cutting force F that causes the bending stress to the semiconductor substrate 1 acts as described above, the portion to be cut 9 is cut from the surface 3 that is the surface on the pulled side of the semiconductor substrate 1.
By reducing the distance to the modified region 15 in, the cutting force F along the planned cutting portion 9 can be reduced.

The distance from the surface 3 of the semiconductor substrate 1 to the melt processing region 13 can be controlled by adjusting the position of the laser light focusing point inside the semiconductor substrate 1.

Next, a laser processing apparatus used in the above laser processing method will be described with reference to FIG. FIG. 16 is a schematic configuration diagram of the laser processing apparatus 100.

The laser processing apparatus 100 includes a laser light source 101 for generating a laser light L, a laser light source control unit 102 for controlling the laser light source 101 to adjust the power and repetition frequency of the laser light L, and the laser light L. A dichroic mirror 103 which has a reflection function and is arranged to change the direction of the optical axis of the laser light L by 90 °, and a condenser lens 105 which condenses the laser light L reflected by the dichroic mirror 103. A mounting table 107 on which the semiconductor substrate 1 irradiated with the laser light L condensed by the condensing lens 105 is mounted, a θ stage 108 for rotating the mounting table 107, and the mounting table 107 in the X-axis direction. And an Y-axis stage 11 for moving the mounting table 107 in the Y-axis direction orthogonal to the X-axis direction.
1, a Z-axis stage 113 for moving the mounting table 107 in the Z-axis direction orthogonal to the X-axis and Y-axis directions, and a stage controller 115 for controlling the movement of these four stages 108, 109, 111, 113. With.

Since the Z-axis direction is the direction orthogonal to the surface 3 of the semiconductor substrate 1, it is the direction of the depth of focus of the laser light L incident on the semiconductor substrate 1. Therefore, the Z-axis stage 11
By moving 3 in the Z-axis direction, the focus point P of the laser light L can be aligned with the surface 3 of the semiconductor substrate 1 or a desired position inside the semiconductor substrate 1. In addition, the movement of the condensing point P in the X (Y) axis direction causes the semiconductor substrate 1 to move in the X
It is performed by moving in the X (Y) axis direction by the (Y) axis stage 109 (111).

The laser light source 101 is an Nd: YAG laser which generates pulsed laser light. Other lasers that can be used for the laser light source 101 include Nd: YVO
There are 4 lasers, Nd: YLF lasers and titanium sapphire lasers. Nd: Y when forming the melt-processed region
It is preferable to use an AG laser, an Nd: YVO 4 laser, or an Nd: YLF laser. In this embodiment, pulsed laser light is used for processing the semiconductor substrate 1, but continuous wave laser light may be used as long as it can cause multiphoton absorption.

The laser processing apparatus 100 further includes a mounting table 1
For observing the light source 117 for illuminating the semiconductor substrate 1 mounted on 07 with visible light, the dichroic mirror 103 and the condenser lens 105 are arranged on the same optical axis. Beam splitter 119
With. Beam splitter 119 and condenser lens 1
The dichroic mirror 103 is arranged between the dichroic mirror 05 and the camera. The beam splitter 119 has a function of reflecting approximately half of visible light and transmitting the other half, and is arranged so as to change the direction of the optical axis of visible light by 90 °. About half of the visible light emitted from the observation light source 117 is reflected by the beam splitter 119, and the reflected visible light passes through the dichroic mirror 103 and the condenser lens 105, and cuts the planned cutting line 5 of the semiconductor substrate 1. Illuminate the containing surface 3.

The laser processing apparatus 100 further includes the image pickup device 12 arranged on the same optical axis as the beam splitter 119, the dichroic mirror 103 and the condenser lens 105.
1 and the imaging lens 123. The image sensor 121 is, for example, a CCD camera. The reflected light of visible light that illuminates the surface 3 including the planned cutting line 5 and the like passes through the condenser lens 105, the dichroic mirror 103, and the beam splitter 119, is imaged by the imaging lens 123, and is imaged by the imaging element 121. And becomes imaging data.

The laser processing apparatus 100 further includes an image data processing section 125 to which the image data output from the image sensor 121 is input, an overall control section 127 for controlling the entire laser processing apparatus 100, and a monitor 129. The imaging data processing unit 125 calculates focus data for focusing the visible light generated by the observation light source 117 on the surface 3 based on the imaging data. The stage control unit 115 controls the movement of the Z-axis stage 113 based on this focus data, so that the visible light is focused on the surface 3. Therefore, the imaging data processing unit 125 functions as an autofocus unit. Further, the imaging data processing unit 125 calculates image data such as an enlarged image of the surface 3 based on the imaging data. This image data is sent to the overall control unit 1.
27 is sent to the monitor 129. As a result, an enlarged image or the like is displayed on the monitor 129.

The overall controller 127 includes the stage controller 1
Data from the image pickup device 15, image data from the image pickup data processing unit 125, and the like are input, and the laser light source control unit 102, the observation light source 117, and the stage control unit 115 are controlled based on these data, thereby the laser processing apparatus. Control 100 as a whole. Therefore, the overall control unit 127 functions as a computer unit.

The laser processing method according to this embodiment when the above laser processing apparatus 100 is used will be described below.

In the laser processing method according to the present embodiment, the focusing point is set inside the semiconductor substrate 1, the peak power density at the focusing point is 1 × 10 8 (W / cm 2 ) or more, and the pulse width is By irradiating a laser beam under the condition of 1 μs or less to form a melt processing region inside the semiconductor substrate 1,
A plurality of planned cutting portions are formed in each of the first direction and the second direction.

Here, the semiconductor substrate 1 is a silicon wafer (thickness 625 μm, outer diameter 6 inches) having an orientation flat (hereinafter referred to as “OF”) 21 as shown in FIG. ) Surface and OF
The surface parallel to 21 and the surface perpendicular to OF21 (110)
A surface, that is, a cleavage plane.

In the present embodiment, the first direction is OF
21 is parallel to the longitudinal direction, and the second direction is OF
21 is a direction perpendicular to the longitudinal direction. Further, a plurality of planned cutting portions (hereinafter referred to as “parallel cutting planned portions”) formed in the first direction are formed at intervals of 2 mm, and are for cutting the semiconductor substrate 1 first during braking. ,
A plurality of planned cut portions (hereinafter referred to as “vertical cut portions”) formed in the second direction are formed at intervals of 2 mm, and the semiconductor substrate 1 cut along the parallel cut portions during braking is simultaneously cut. It is for cutting.

In the laser processing method according to this embodiment, the melting process area in the parallel cutting planned portion is made so that the cutting force along the parallel cutting planned portion and the cutting force along the vertical cutting planned portion become equal. The formation density of the melt-processed region in the vertical cutting scheduled portion is made higher than the formation density of.

This requires a larger cutting force in the case of cutting perpendicularly to the longitudinal direction of the OF 21 and a case of cutting the uncut semiconductor substrate 1 as compared with the case of cutting in parallel to the longitudinal direction of the OF 21. This is because a greater cutting force is required when the semiconductor substrates 1 that have been cut are cut at the same time. That is, if the formation density of the melt-processed region in the planned parallel cutting portion and the formation density of the melt-processed region in the vertical cutting planned portion are equalized, the cutting force along the vertical cutting planned portion is higher than the cutting force along the parallel cutting planned portion. This is because the power becomes greater. As described above, when the formation density of the melt-processed region in the planned cutting portion is increased, the cutting force along the planned cutting portion is reduced.

In this embodiment, since pulsed laser light is used as the laser light, by increasing the repetition frequency of the laser light, the melting process in the vertical cutting scheduled portion is higher than the formation density of the melting processing region in the parallel cutting scheduled region. The formation density of the region is increased so that the cutting force along the planned parallel cutting portion and the cutting force along the planned vertical cutting portion are equal. The repetition frequency of the laser light for forming the planned parallel cut portion and the repetition frequency of the laser light for forming the vertical cut portion are determined in advance in consideration of various conditions.

A specific example of the laser processing method according to this embodiment will be described with reference to FIGS. Figure 1
8 is a flowchart for explaining the laser processing method according to the present embodiment.

First, the light absorption characteristics of the semiconductor substrate 1 are measured by a spectrophotometer or the like (not shown). Based on the measurement result, the laser light source 101 that emits the laser light L having a wavelength transparent to the semiconductor substrate 1 or a wavelength with little absorption is selected (S101).

Then, the thickness of the semiconductor substrate 1 is measured, the amount of movement of the semiconductor substrate 1 in the Z-axis direction is determined based on the thickness measurement result and the refractive index of the semiconductor substrate 1, and the above-mentioned parallel cutting is planned. The repetition frequency of the laser light for forming the portion and the repetition frequency of the laser light for forming the vertical cut portion are determined (S103). The amount of movement of the semiconductor substrate 1 in the Z-axis direction is determined by the focusing point P of the laser light L having a wavelength transparent to the semiconductor substrate 1 or a wavelength with little absorption.
Is the amount of movement of the semiconductor substrate 1 in the Z-axis direction with reference to the condensing point P of the laser light L located on the surface 3 of the semiconductor substrate 1 in order to position the inside of the semiconductor substrate 1. Step S
The movement amount data and the repetition frequency data determined in 103 are input to the overall control unit 127.

Thereafter, the semiconductor substrate 1 is processed by the laser processing apparatus 1
No. 00 on the mounting table 107, and the visible light is generated from the observation light source 117 to illuminate the semiconductor substrate 1 (S10).
5). The image pickup device 12 is provided on the surface 3 of the illuminated semiconductor substrate 1.
Image by 1. The image data captured by the image sensor 121 is sent to the image data processing unit 125. Based on the imaged data, the imaged data processing unit 125 calculates focus data such that the visible light focus of the observation light source 117 is located on the surface 3 (S107).

This focus data is sent to the stage controller 115. The stage control unit 115 moves the Z-axis stage 113 in the Z-axis direction based on this focus data (S109). As a result, the focus of visible light from the observation light source 117 is located on the surface 3 of the semiconductor substrate 1. The imaging data processing unit 125 calculates the enlarged image data of the surface 3 of the semiconductor substrate 1 based on the imaging data. This magnified image data is sent to the monitor 129 via the overall control unit 127, whereby the monitor 129 displays the surface 3 of the semiconductor substrate 1.
An enlarged image of is displayed.

Then, the semiconductor substrate 1 is rotated by the θ stage 108 so that the direction parallel to the longitudinal direction of the OF 21 of the semiconductor substrate 1 matches the stroke direction of the Y stage 111 (S111). Then, the movement amount data determined in step S103 and input in advance to the overall control unit 127 is sent to the stage control unit 115. The stage controller 115 uses the laser light L based on this movement amount data.
The semiconductor substrate 1 is moved in the Z-axis direction by the Z-axis stage 113 to a position where the condensing point P is inside the semiconductor substrate 1 (S113).

After that, the repetition frequency of the laser light for forming the parallel cutting planned portion, which is determined in step S103 and is input in advance to the overall control unit 127, is sent to the laser light source control unit 102. The laser light source control unit 102 determines the laser light source 101 based on the repetition frequency data.
To generate a laser beam L and irradiate the semiconductor substrate 1 with the laser beam L. Since the condensing point P of the laser light L is located inside the semiconductor substrate 1, the melting processing region is the semiconductor substrate 1
Is formed only inside. Then, the X-axis stage 109
The semiconductor substrate 1 is moved by the or Y-axis stage 111 to form a plurality of parallel cut portions at intervals of 2 mm inside the semiconductor substrate 1 (S115).

Then, the semiconductor substrate 1 is rotated by the θ stage 108 so that the direction perpendicular to the longitudinal direction of the OF 21 of the semiconductor substrate 1 matches the stroke direction of the Y stage 111 (S117). Then, the repetition frequency of the laser light for forming the planned vertical cutting portion, which is determined in step S103 and input in advance to the overall control unit 127, is sent to the laser light source control unit 102. The laser light source control unit 102 causes the laser light source 101 to generate the laser light L based on the repetition frequency data, and irradiates the semiconductor substrate 1 with the laser light L. Since the condensing point P of the laser light L is located inside the semiconductor substrate 1, the melting processed region is formed only inside the semiconductor substrate 1. Then, the semiconductor substrate 1 is moved by the X-axis stage 109 and the Y-axis stage 111 to form a plurality of planned vertical cutting portions at intervals of 2 mm inside the semiconductor substrate 1 (S119).

In this way, inside the semiconductor substrate 1 shown in FIG. 17, the parallel cut portion 9a is formed as shown in FIG.
And the planned vertical cutting portions 9b are formed in a lattice shape. Then, as shown in FIGS. 20 and 21, the formation density of the melt-processed spots 15 in the planned vertical cutting portion 9b shown in FIG. 21 is higher than that of the melt-processed spots 15 in the parallel cutting planned portion 9a shown in FIG. It's getting higher. As a result, the cutting force along the planned vertical cutting portion 9b, which requires a large cutting force when the formation densities of the melt processing regions are made equal, is reduced, and the cutting force along the planned parallel cutting portion 9a and the vertical cutting are performed. The cutting force along the planned portion 9b becomes equal.

Therefore, at the time of breaking the semiconductor substrate 1, the knife edge is pressed against the back surface 17 of the semiconductor substrate 1 to cut the semiconductor substrate 1 into strips along the parallel cut portions 9a. After that, the semiconductor substrate 1 cut into strips is cut at the same time along the vertical cut portions 9b, and the cutting force along the parallel cut portions 9a and the vertical cut portions 9b are cut. Since the cutting force is the same, even if the direction of the planned cutting portion changes, it is not necessary to newly perform extremely severe conditions such as keeping the pressing force of the knife edge to the necessary minimum. Therefore, it is possible to cut the semiconductor substrate 1 with high accuracy while suppressing the occurrence of chipping and cracking while keeping the braking conditions constant, and obtain a semiconductor chip having a highly accurate cut surface.

Although the embodiments of the present invention have been described in detail above, it goes without saying that the present invention is not limited to the above embodiments.

In the above-described embodiment, the formation density of the melt-processed regions is different in the formation state of the melt-processed regions in the parallel cut-scheduled part 9a and the vertical cut-scheduled part 9b of the semiconductor substrate 1. As the formation state of the processing area,
By changing the size of the melt-processed region and the distance from the surface 3 of the semiconductor substrate 1 to the melt-processed region, the parallel cutting scheduled portion 9
The cutting force along a and the cutting force along the planned vertical cutting portion 9b may be equal. Further, these forming states may be combined so that the cutting force along the parallel cut scheduled portion 9a and the cutting force along the vertical cut scheduled portion 9b become equal.

In the above embodiment, a square semiconductor chip (one side is 2 mm) is cut out from the semiconductor substrate 1. However, for example, when a rectangular semiconductor chip is cut out, the length of the rectangle is cut. Since the cutting force for cutting the semiconductor substrate is different between the side direction and the short side direction, the present invention is extremely effective even in such a case.

Further, in the present invention, the portion to be cut formed in the first direction is modified by the above-described one-point spot laser processing (one focusing point of laser light is aligned in the thickness direction). The region to be formed in one row and the planned cutting portion to be formed in the second direction intersecting the first direction is processed by a multi-point spot laser processing described later (a plurality of converging points of laser light are aligned in the thickness direction). By forming the modified regions in a plurality of rows, it is possible to make the modified regions different from each other. 22 is a diagram showing a first embodiment of multipoint spot laser processing, and FIG. 23 is a diagram showing a second embodiment of multipoint spot laser processing.

As shown in FIG. 22, by using a two-point spot lens 131, the condensing points P1 and P2 of the laser light L aligned in the thickness direction of the semiconductor substrate 1 are simultaneously aligned inside the semiconductor substrate 1, thereby Two modified regions 7 are formed inside the substrate 1.
Rows are formed, and the planned cutting portions 9 are formed by these two rows of modified regions 7.
Can be formed. The specific conditions are as follows. Semiconductor substrate: Silicon wafer (thickness 300 μm) Laser light source wavelength: 1064 nm Beam diameter: φ5 mm Beam profile: TEM 00 Short focal depth position: 60 μm Long focal depth position: 240 μm Long focal length A. : 0.6 short focus N. A. : 0.8 Lens material: BK7

Further, as shown in FIG. 23, the semiconductor substrate 1
The condensing point P1 of the laser beam L1 is adjusted by the condensing lens 105 to the front surface 3 side of the inside, and the condensing point of the laser beam L2 is adjusted by the other condensing lens 105 to the rear surface 17 side inside the semiconductor substrate 1. By combining P2, two rows of modified regions 7 are formed inside the semiconductor substrate 1, and these two rows of modified regions 7 are formed.
Therefore, the planned cutting portion 9 can be formed.

[0082]

As described above, according to the laser processing method of the present invention, a phenomenon of multiphoton absorption is caused inside the semiconductor substrate by irradiating the inside of the semiconductor substrate with a laser beam and focusing the laser beam. To generate a modified region, and with the modified region, a first planned cutting portion and a second planned cutting portion are formed in a first direction and a second direction intersecting with each other. There is. When the modified region is formed inside the semiconductor substrate, cracks occur in the thickness direction of the semiconductor substrate starting from the modified region.Therefore, the semiconductor substrate is cut along the planned cutting portion with a relatively small cutting force. Can be cut.
Then, the magnitude of this cutting force changes depending on the formation state of the modified region in the planned cutting portion. Therefore, the formation state of the modified region in the first planned cutting portion and the formation state of the modified region in the second planned cutting portion are made different to cut the semiconductor substrate along the first planned cutting portion. Therefore, it is possible to control the first cutting force for cutting and the second cutting force for cutting the semiconductor substrate along the second planned cutting portion to be equal to each other. That is, it is possible to form, in the semiconductor substrate, a planned cutting portion capable of keeping the cutting force constant for cutting the semiconductor substrate.

[Brief description of drawings]

FIG. 1 is a plan view of a semiconductor substrate during laser processing by a laser processing method according to this embodiment.

FIG. 2 is a sectional view taken along line II-II of the semiconductor substrate shown in FIG.

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

FIG. 4 is a sectional view taken along line IV-IV of the semiconductor substrate shown in FIG.

5 is a cross-sectional view of the semiconductor substrate shown in FIG. 3, taken along line VV.

FIG. 6 is a plan view of a semiconductor substrate cut by a laser processing method according to this embodiment.

FIG. 7 is a view showing a photograph of a cross section of a part of a silicon wafer cut by the laser processing method according to the present embodiment.

FIG. 8 is a graph showing the relationship between the wavelength of laser light and the transmittance inside the silicon substrate in the laser processing method according to the present embodiment.

FIG. 9 is a diagram showing a planned cutting portion in which melting processing spots are intermittently formed by the laser processing method according to the present embodiment.

FIG. 10 is a diagram showing a planned cutting portion in which melting processing spots are continuously formed by the laser processing method according to the present embodiment.

FIG. 11 is a cross-sectional view of a semiconductor substrate in which laser light of a predetermined power is focused by the laser processing method according to the present embodiment.

FIG. 12 is a cross-sectional view of a semiconductor substrate including a melting treatment spot formed by irradiation with laser light shown in FIG.

13 is a cross-sectional view of a semiconductor substrate in which laser light having a power higher than that in the case of FIG. 11 is focused inside.

FIG. 14 is a cross-sectional view of a semiconductor substrate including a melting treatment spot formed by irradiation with laser light shown in FIG.

FIG. 15 is a diagram schematically showing a state in which a cutting force is applied to the back surface of the semiconductor substrate according to the present embodiment.

FIG. 16 is a schematic configuration diagram of a laser processing apparatus according to the present embodiment.

FIG. 17 is a perspective view of a semiconductor substrate according to this embodiment.

FIG. 18 is a flowchart for explaining a laser processing method according to this embodiment.

19 is a sectional view taken along line IXX-IXX of the semiconductor substrate shown in FIG.

20 is a cross-sectional view of the semiconductor substrate shown in FIG. 19 taken along the line XX-XX.

21 is a sectional view taken along line XXI-XXI of the semiconductor substrate shown in FIG.

FIG. 22 is a diagram showing a first example of multi-point spot laser processing.

FIG. 23 is a diagram showing a second embodiment of multipoint spot laser processing.

[Explanation of symbols]

1 ... Semiconductor substrate, 3 ... Surface, 5 ... Planned cutting line, 7 ...
Modified region, 9 ... scheduled cutting portion, 9a ... parallel cutting scheduled portion, 9
b ... Vertical cutting planned portion, 11 ... Silicon wafer, 13 ... Melt processing region, 15 ... Melt processing spot, 17 ... Back surface, 1
9 ... Area, 21 ... Orientation flat, 100
... laser processing device, 101 ... laser light source, 105 ... focusing lens, 108 ... θ stage, 109 ... X axis stage, 111 ... Y axis stage, 113 ... Z axis stage, F
... Cutting power, L, L1, L2 ... Laser light, P, P1, P2
… Focus point.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. 7 Identification code FI theme code (reference) H01L 21/301 B23K 101: 40 // B23K 101: 40 H01L 21/78 BL F term (reference) 3C069 AA01 BA08 BB01 BB02 BB03 CA05 EA02 4E068 AD01 AE01 CA02 CA03 CA11 DA10

Claims (12)

[Claims]
1. A modified region by multiphoton absorption is formed inside the semiconductor substrate by irradiating a laser beam with a focusing point aligned inside the semiconductor substrate, and the modified region forms the first modified region. A step of forming a first planned cutting portion in a direction, and irradiating a laser beam with a focusing point inside the semiconductor substrate to form a modified region by multiphoton absorption inside the semiconductor substrate, Forming a second planned cutting part in a second direction intersecting the first direction in the modified region, and cutting the semiconductor substrate along the first planned cutting part. So that the first cutting force for cutting and the second cutting force for cutting the semiconductor substrate along the second planned cutting portion are equal to each other, the modified region in the first planned cutting portion. Forming state and modified region in the second planned cutting portion Made different from the formation with each other, the laser processing method characterized by.
2. When the state of formation of the modified region in the first planned cutting portion and the state of formation of the modified region in the second planned cutting portion are made equal to each other, the first cutting force is higher than that of the first cutting force. When the cutting force of 2 becomes larger, the formation density of the modified regions in the second planned cutting portion is made higher than the formation density of the modified regions in the first planned cutting portion. The laser processing method according to claim 1.
3. When the state of formation of the modified region in the first planned cutting portion and the state of formation of the modified region in the second planned cutting portion are made equal to each other, the first cutting force is higher than that of the first cutting force. When the cutting force of 2 becomes larger, the size of the modified region in the second planned cutting portion is made larger than the size of the modified region in the first planned cutting portion. The laser processing method according to claim 1 or 2.
4. The first cutting force and the second cutting force generate bending stress in the semiconductor substrate, and the formation state of a modified region in the first planned cutting portion and If the second cutting force is larger than the first cutting force when the formation state of the modified region in the second planned cutting portion is made equal, the bending stress due to the first cutting force is increased. The distance from the surface of the semiconductor substrate on the side pulled by the second cutting force to the modified region in the first planned cutting portion compared to the distance from the surface of the semiconductor substrate on the side pulled by the second cutting force. The laser processing method according to any one of claims 1 to 3, wherein the distance to the modified region in the planned cutting portion 2 is reduced.
5. The condition for irradiating the semiconductor substrate with laser light is that the peak power density at the condensing point of the laser light is 1
The modified region including a melt-processed region is formed inside the semiconductor substrate by setting the pulse width to be not less than × 10 8 (W / cm 2 ) and not more than 1 μs. The laser processing method according to any one of 1.
6. A modified region is formed inside the semiconductor substrate by irradiating a laser beam with a converging point inside the semiconductor substrate, and the modified region forms a first direction in a first direction. Forming a modified region inside the semiconductor substrate by irradiating a laser beam with a focusing point aligned inside the semiconductor substrate. A step of forming a second planned cutting portion in a second direction intersecting with the first direction, the formation state of the modified region in the first planned cutting portion and a modification in the second planned cutting portion. A laser processing method characterized in that a formation state of a quality region is different from each other.
7. A first cutting force for cutting the semiconductor substrate along the first planned cutting portion, and a second cutting force for cutting the semiconductor substrate along the second planned cutting portion.
The state of formation of the modified region in the first planned cutting portion and the state of formation of the modified region in the second planned cutting portion are made different from each other so that the cutting force is equal to each other. Item 7. The laser processing method according to Item 6.
8. The formation density of the modified region in the first planned cutting portion and the formation density of the modified region in the second planned cutting portion are different from each other, according to claim 6 or 7. Laser processing method.
9. The laser processing according to claim 6, wherein the size of the modified region in the first planned cutting portion and the size of the modified region in the second planned cutting portion are different from each other. Method.
10. The laser processing method according to claim 6, wherein the modified region is a melt-processed region.
11. The second planned cutting part is for cutting the semiconductor substrate along the first planned cutting part and then simultaneously cutting the cut semiconductor substrate. The laser processing method according to any one of claims 1 to 10.
12. An orientation flat is formed on the semiconductor substrate, the first direction is parallel to the longitudinal direction of the orientation flat, and the second direction is perpendicular to the longitudinal direction of the orientation flat. The laser processing method according to any one of claims 1 to 10, wherein
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