TW201738027A - Method for cutting object to be processed - Google Patents

Abstract

A method for cutting an object to be processed comprises: a first step of causing laser light to enter a light condensing lens; and a second step of forming a reformed region in the object to be processed along a planned cutting line by causing a light condensing point to relatively move along the planned cutting line while using the light condensing lens to cause the laser light to be condensed inside the object to be processed. A light shielding region overlaps a part of the planned cutting line. In the first step, the laser light is caused to enter the light condensing lens using a ring-shaped laser light intensity profile. In the second step, a main plane is made the entrance plane for the laser light, and the light condensing point is relatively moved along the planned cutting line so as to pass through the light shielding region.

Description

Processing object cutting method

The present invention relates to a method of cutting an object to be processed.

Patent Document 1 describes a method of manufacturing a semiconductor wafer. In this method, an n-type gallium nitride based semiconductor layer (n-type layer) and a p-type gallium nitride based semiconductor layer (p-type layer) are laminated on a sapphire substrate, and the formed semiconductor wafer is divided into A plurality of semiconductor wafers. In this method, first, the element separation trench is formed by the desired wafer shape. The element isolation trench is formed by etching the p-type layer. Next, a modified region is formed inside the sapphire substrate. The modified region is formed by aligning the spotlight with the inside of the sapphire substrate and irradiating the laser light. The modified region is to be used in the disconnection of the substrate (wafer). Then, the substrate (wafer) is divided into wafers using a cleaving device.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Laid-Open Patent Publication No. 2011-181909

On the surface of the object to be processed (the wafer), there is a case where a light shielding region for shielding the laser light is provided. In this case, when the surface is used as the incident surface of the laser light and viewed from the direction intersecting with the incident surface, the laser beam is irradiated while the light collecting point of the laser light is moved through the light shielding region. When the object is processed, there is a fear that a portion where the modified region is defective may occur at a position corresponding to the light-shielding region. In the damaged area, there is a lack of precision, which will reduce the accuracy of cutting. As a result, there is a possibility that a step difference or the like occurs on the cut surface of the object to be processed, and the cut surface is defective.

In the same manner as the present invention, it is an object of the invention to provide an object cutting method capable of suppressing deterioration of a cut surface.

The method of cutting an object to be processed in the same manner as the present invention is a method for cutting an object to be cut along a line to cut, wherein the object has a main surface including a shading A light shielding region of laser light, comprising: a first process for causing laser light to be incident on a collecting lens for collecting laser light on a processing object, and a second process, using a collecting lens The laser beam is condensed inside the object to be processed, and the condensed spot of the laser light is relatively moved along the line to cut, thereby forming a modified region inside the object to be processed along the line to cut; The light shielding region is overlapped with a part of the planned cutting line when viewed from a direction intersecting the main surface, and the laser beam is made to have an intensity cross section of the laser light in an annular shape in the first manufacturing process. It is incident on the condensing lens; in the second process, the main surface is the incident surface of the laser light, and when viewed from the direction intersecting the main surface, the condensed spot is cut along the cut by the light shielding area. The line moves relatively.

In this method, the laser light is incident on the collecting lens in the first process. Then, in the second process, the laser light is collected by the condensing lens inside the object to be processed, and the condensed spot is relatively moved along the line to cut, thereby processing along the line to cut. The inside of the object forms a modified region. Here, the object to be processed has a main surface including a light shielding region that shields the laser light. Further, in the second process, the main surface is used as an incident surface of the laser light, and the light collecting point is relatively moved along the line to cut so as to pass through the light shielding region. Therefore, according to the conventional method, there is a fear that a defective portion of the modified region is generated at a position corresponding to the light shielding region in the inside of the object to be processed.

In order to solve this problem, the inventors of the present invention have found that it is possible to suppress the generation of a modified region at a position corresponding to the light-shielding region by concentrating the laser beam having the annular-shaped intensity profile and illuminating the object to be processed. The shortcomings of the deficiencies. Further, in this method, in the first process, laser light having an annular cross section in which an intensity cross section is formed is incident on the collecting lens. Therefore, according to this method, it is possible to suppress a portion where the modified region is defective at a position corresponding to the light shielding region. As a result, it is possible to suppress: on the cut surface Defects in the cut surface such as the stage difference.

In the method of cutting an object to be processed in the same manner as in the present invention, the object to be processed may include a semiconductor layer for a semiconductor laser including gallium nitride, a semiconductor layer including a main surface, and a light shielding region. The strip-shaped high-density defect region of the semiconductor layer is provided so as to extend in a direction intersecting the line to cut, and the line to be cut is set along the cleavage plane of the semiconductor layer. Here, in the case of forming a semiconductor laser resonator by cleaving, the cleavage plane is required to be mirror-finished. Therefore, it is particularly important to suppress the deterioration of the cut surface (opening surface). On the other hand, according to the above method, the modified region can be formed so as not to have a defective portion as described above along the planned cutting line set by the cleavage surface of the semiconductor layer for semiconductor laser. Therefore, it is possible to suppress the occurrence of defects in the cut surface (cleavage surface), and it is possible to achieve mirror surface reduction of the cut surface.

In the object cutting method according to the present invention, in the first process, the intensity cross section may be formed into an annular shape by a spatial light modulator that can exhibit a predetermined modulation pattern. In this case, by controlling the predetermined modulation pattern of the spatial light modulator, the annular shape of the intensity profile of the laser light can be dynamically changed. Therefore, the formation of the appropriate modified region can be performed in accordance with the material of the object to be processed or the required cutting accuracy.

According to the same aspect of the present invention, it is possible to provide a method of cutting an object to be processed which can suppress deterioration of a cut surface.

1‧‧‧Processing objects

3‧‧‧ Surface of the object to be processed

5, 5a, 5b‧‧‧ cut the booking line

6‧‧‧ Orientation plane

7‧‧‧Modified area

7s‧‧‧Qualification point

8‧‧‧ cut off starting area

10‧‧‧ wafer

10a‧‧‧cut face (m face)

10b‧‧‧ cut surface (a side)

11‧‧‧Substrate

12‧‧‧Semiconductor layer

13‧‧‧Electrode

14‧‧‧Lighting layer

14s‧‧‧End face of the luminescent layer

15‧‧‧ strip base

20‧‧‧ Chip Department

21‧‧‧Substrate

22‧‧‧Semiconductor layer

22s‧‧‧ main face

100‧‧‧ Laser processing equipment

101‧‧‧Laser light source

102‧‧‧Laser Light Source Control Department

103‧‧‧beam splitter

105‧‧‧ Concentrating lens

107‧‧‧Support table

111‧‧‧Workbench

113‧‧‧Optics

115‧‧‧Workbench Control Department

121, 123‧‧‧ mirror

122‧‧‧Space light modulator

Modulation surface of the 122s‧‧‧ spatial light modulator

L‧‧‧Round-shaped intensity profile of laser light

Ln‧‧‧solid round (general) intensity profile of laser light

A‧‧‧ Relative direction of movement of laser light along the line to cut

Ax‧‧‧ optical axis of laser light

The inner edge of the Ci‧‧‧ strength profile

The outer edge of the Co‧‧‧ strength profile

The inner diameter of the Di‧‧‧ laser beam

Do‧‧‧The outer diameter of the laser beam

G‧‧‧ stage difference

M‧‧‧ defective parts of the modified area

SA‧‧‧Light-shielded area

P‧‧‧ spotlight

Pa‧‧‧ intensity profile of circular laser light

Pb‧‧‧General laser light intensity profile

Fig. 1 is a schematic configuration diagram of a laser processing apparatus used for forming a modified region.

Fig. 2 is a plan view of an object to be processed which is a target of formation of a modified region.

Fig. 3 is a cross-sectional view taken along line II-II of the object to be processed in Fig. 2;

Fig. 4 is a plan view of the object to be processed after laser processing.

Fig. 5 is a cross-sectional view taken along the line V-V of the object to be processed in Fig. 4.

Fig. 6 is a cross-sectional view taken along line VI-VI of the object to be processed in Fig. 4.

Fig. 7 is a perspective view showing a wafer manufactured by using the object cutting method of the embodiment.

Fig. 8 is a view showing the object to be processed of the object cutting method of the embodiment.

Fig. 9 is a view showing the object to be processed of the object cutting method of the embodiment.

Fig. 10 is a view showing the configuration of the optical system shown in Fig. 1.

Figure 11 is a view showing the intensity profile of the laser light.

Fig. 12 is a cross-sectional view showing the main process of the object cutting method of the embodiment.

Fig. 13 is a view showing a cut surface of the object to be processed.

Fig. 14 is a view for explaining the relationship between the amount of deflection of the center of the light beam and the light shielding region, and the transmittance.

Figure 15 is a graph showing the relationship between the intensity on the optical axis of the laser light and the distance from the incident surface.

Fig. 16 is a view showing a modification of the annular strength cross section.

Fig. 17 is a view showing another modification of the annular strength cross section.

Fig. 18 is a view showing another modification of the annular strength cross section.

Fig. 19 is a view showing another modification of the annular strength cross section.

Hereinafter, an embodiment of one aspect of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals will be given to the same or in the opposite parts, and the repeated description will be omitted.

In the method of cutting an object to be processed according to the present embodiment, the object to be processed is irradiated with laser light along the line to be cut, and the starting point of the object to be cut is formed in at least the inside of the object to be cut along the line to cut. region. Here, first, the formation of the modified region will be described with reference to FIGS. 1 to 6 .

As shown in Fig. 1, the laser processing apparatus 100 includes a laser light source 101 that pulsates laser light L and a method of changing the orientation of the optical axis (light path) of the laser light L by 90°. Configured splitting The mirror 103 and a collecting lens 105 for collecting the laser light L on the object 1 are used. Further, the laser processing apparatus 100 includes a support table 107 for supporting the object 1 to be irradiated by the laser beam L condensed by the condensing lens 105, and a table 111 for use in Moving the support table 107; and the laser light source control unit 102 for controlling the output of the laser light L or the pulse width, pulse waveform, etc. to control the laser light source 101; and the table control unit 115, which is used To control the movement of the work table 111.

In the laser processing apparatus 100, the laser light L emitted from the laser light source 101 is changed by 90 degrees by the direction of the optical axis of the spectroscope 103, and then concentrated by the collecting lens 105: The inside of the object 1 on the support table 107. At the same time, the table 111 is moved, and the object 1 is relatively moved along the line to cut 5 with respect to the laser light L. Thereby, the modified object region along the line to cut 5 is formed in the object 1 to be processed. Here, in order to move the laser beam L relative to each other, the table 111 is moved. However, the condensing lens 105 may be moved or both of them may be moved. Further, in the laser processing apparatus 100, the laser beam L may be incident on the condensing lens 105 via the optical system 113 and then incident on the condensing lens 105.

As the object to be processed, a plate-shaped member (for example, a substrate or a wafer) is used, and includes a semiconductor substrate formed of a semiconductor material or a piezoelectric substrate formed of a piezoelectric material. As shown in FIG. 2, the cutting target line 5 is set in the object 1 to be processed. The predetermined line 5 is cut and is an imaginary line extending linearly. When a modified region is formed inside the object 1 to be processed, as shown in FIG. 3, the light collecting point (concentrating position) is made. In a state in which P is aligned with the inside of the object 1 , the laser light L is relatively moved along the line to cut 5 (that is, in the direction of the arrow A in FIG. 2 ). Thereby, as shown in FIG. 4, FIG. 5, and FIG. 6, the modified region 7 is formed on the object 1 along the line to cut 5 . The modified region 7 formed along the line to cut 5 serves as the cutting start region 8.

The condensed spot P refers to where the laser light L converges. The line to cut 5 is not limited to a straight line, and may be a curved shape, or a combination of three or three elements, or a coordinate designation. The line to cut 5 is not limited to the imaginary line, and may be a line actually drawn on the surface 3 of the object 1 to be processed. The modified region 7 has a situation in which it is continuously formed, and there are cases in which it is formed intermittently. The modified region 7 may be in a column shape or a dot shape. In addition, the modified region 7 may be formed at least inside the object 1 to be processed. Further, when the crack is formed by using the modified region 7 as a starting point, the crack and the modified region 7 may be exposed on the outer surface (surface 3, back surface, or outer peripheral surface) of the object 1 to be processed. The laser light incident surface when the modified region 7 is formed is not limited to the surface 3 of the object 1 and may be the back surface of the object 1 .

When the modified region 7 is formed inside the object 1 to be processed, the laser beam L is transmitted through the object 1 and is particularly absorbed by the spot P near the inside of the object 1 . Thereby, the modified region 7 is formed in the object 1 (that is, internal absorption type laser processing). In this case, since the laser light L is hardly absorbed on the surface 3 of the object 1 to be processed, the surface 3 of the object 1 does not melt. On the other hand, the modified region 7 is formed on the surface 3 of the object 1 to be processed. In this case, the laser light L is particularly absorbed by the spot P near the surface 3, and is melted and removed from the surface 3 to form a removed portion such as a hole or a groove (surface absorption type laser processing). .

The modified region 7 refers to a region in which the density, the inflection rate, the mechanical strength, or other physical properties are different from the surroundings. The modified region 7 includes, for example, a molten processed region (a region that is re-solidified after being melted, a region in a molten state, and a region in a state of being resolidified from melting, and at least any of these). ), cracked areas, dielectric damage areas, areas of inflection rate change, etc., there are also such mixed areas. Further, as the modified region 7, the material of the object 1 is changed, the density of the modified region 7 is changed from the density of the non-modified region, or the lattice defect is formed. Area (this is also classified as a high dislocation density area).

The molten processed region, the inflection rate changing region, the density of the modified region 7, the region which changes from the density of the non-modified region, and the region in which the lattice defect is formed, and further, in the regions The inside or the interface between the modified region 7 and the non-modified region may contain cracks (cracks, micro cracks). The cracks contained therein may be formed in all of the modified regions 7, or may be formed only in a part or in a plurality of portions. The object 1 is a substrate including a crystalline material having a crystal structure. For example, the object 1 is formed of at least one of gallium nitride (GaN), germanium (Si), tantalum carbide (SiC), lithium niobate (LiTaO ₃ ), and sapphire (Al ₂ O ₃ ). The substrate. In other words, the object 1 may include, for example, a gallium nitride substrate, a tantalum substrate, a tantalum carbide substrate, a lithium niobate substrate, or a sapphire substrate. The crystalline material may be any of an anisotropic crystal and an isotropic crystal.

In the present embodiment, the modified region 7 can be formed by forming a plurality of modified spots (processing scars) along the line to cut 5 . In this case, the modified region 7 is obtained by collecting a plurality of modified spots. The modified point refers to a modified portion formed by a single shot of a pulsed laser light (that is, a one-shot laser shot: a laser shot). Examples of the modification point include a crack point, a melting point, a change point of a refractive index, or a mixture of at least one of these. For the modified point, the required cutting accuracy, the required flatness of the cut surface, the thickness, type, and crystal orientation of the object 1 can be appropriately controlled to appropriately control the size or the length of the crack to be generated. .

Next, a method of cutting an object to be processed according to the present embodiment will be described. Fig. 7 is a perspective view showing a wafer manufactured by using the object cutting method of the embodiment. The wafer 10 is, for example, a semiconductor laser containing gallium nitride. The wafer 10 includes a cut surface (for example, an m-plane located on a gallium nitride crystal) 10a as a cleavage surface, and another cut surface (for example, an a-side of a gallium nitride crystal) that intersects the cut surface 10a. 10b. The wafer 10 has a substrate 11 and a semiconductor layer 12 formed on the substrate 11, and an electrode 13 formed on the substrate 11 and the semiconductor layer 12.

The substrate 11 is, for example, a semiconductor substrate containing gallium nitride. The substrate 11 is, for example, a GaN substrate. The semiconductor layer 12 is, for example, by epitaxy A semiconductor laminate formed by growth. The semiconductor layer 12 contains, for example, gallium nitride. The semiconductor layer 12 includes, for example, a light-emitting layer (active layer) 14 for semiconductor lasers. The light emitting layer 14 is buried in the semiconductor layer 12. The end surface 14s of the light-emitting layer 14 is included in the cut surface 10a. The end face 14s is a mirror surface for forming a laser resonator. The electrode 13 is used to apply a voltage to the semiconductor layer 12.

The wafer 10 includes a pair of strip-shaped bases 15. The strip-shaped base portion 15 is provided on the semiconductor layer 12 so as to extend in a direction crossing the cut surface 10a of the wafer 10. The strip base 15 contains, for example, gallium nitride. The strip base 15 is a high density defect area. The strip base 15 is used to shield the laser light L by, for example, scattering.

8 and 9 are views showing the object to be processed of the object cutting method according to the embodiment. Fig. 8 is a plan view, and Fig. 9(a) is a partially enlarged view of Fig. 8. Fig. 9(b) is a cross-sectional view taken along line IX-IX of Fig. 9(a). In the object cutting method of the present embodiment, as shown in Figs. 8 and 9, first, the object 1 is prepared. The object 1 has a plurality of wafer portions 20 for forming the wafer 10. The wafer portion 20 is in a direction parallel to the orientation flat surface 6 of the object 1 (hereinafter, also referred to as a "first direction"), and a direction perpendicular to the orientation plane 6 (hereinafter, There is also a case called "the second direction", which is arranged in a quadratic shape.

The object 1 has a substrate 21 for spanning the substrate 11 provided in the plurality of wafer portions 20. Further, the object 1 has a semiconductor layer 22 for spanning across a plurality of wafer portions 20. Semiconductor layer 12. As described above, the semiconductor layer 22 is, for example, a semiconductor layer for a semiconductor laser including gallium nitride. The semiconductor layer 22 is provided on the substrate 21. The semiconductor layer 22 includes a main surface 22s which is a surface on the opposite side to the substrate 21.

In the object 1 to be processed, a plurality of planned cutting lines 5a along the first direction and a plurality of planned cutting lines 5b along the second direction are set. The cut planned line 5a and the cut planned line 5b are crossed (for example, perpendicularly intersected). The wafer 10 is obtained by cutting the wafer portion 20 by cutting the object 1 along the line to cut 5a and the line to cut 5b. In other words, the single wafer portion 20 is defined by a region surrounded by a pair of adjacent cutting lines 5a and a pair of mutually adjacent cutting planned lines 5b.

The cutting planned line 5a is set along the cleavage plane of the substrate 21 and the semiconductor layer 22 (for example, the m-plane of the gallium nitride crystal). Therefore, the pair of cutting planned lines 5a adjacent to each other define the length of the wafer portion 20 located in the second direction (the length of the resonator of the semiconductor laser). The cutting planned line 5b is set, for example, along the a plane of the gallium nitride crystal. The pair of cutting planned lines 5b adjacent to each other define the length of the wafer portion 20 located in the first direction.

The semiconductor layer 22 is provided with a plurality of strip-shaped base portions 15 extending in the second direction. The wafer portions 20 adjacent to each other in the first direction are divided by the strip base portion 15. The strip-shaped base portion 15 extends, for example, in a direction intersecting (for example, perpendicularly intersecting) the split surfaces of the substrate 21 and the semiconductor layer 22 (for example, the m-plane of the gallium nitride crystal). The line to cut 5b is set in the strip base 15 along the strip base 15. Also, cut off the planned line 5a is set across the plurality of strip-like bases 15 in such a manner as to intersect (for example, perpendicularly intersect) the strip-like bases 15.

The strip base 15 is a part of the main surface 22s constituting the semiconductor layer 22. The area corresponding to the strip base 15 in the main surface 22s is a light shielding area SA that shields the laser light L. Therefore, the light shielding region SA is a strip-shaped high-density defect region provided on the semiconductor layer 22 so as to extend in a direction crossing (for example, perpendicularly intersecting) the planned cutting line 5a. Further, the light shielding area SA is overlapped with a part of the planned cutting line 5a when viewed from a direction intersecting the main surface 22s. Moreover, the predetermined line 5b is cut so as to be located in the light shielding area SA.

Further, each of the wafer portions 20 includes an electrode 13 and a light-emitting layer 14. The electrode 13 is provided on the main surface 22s. The light-emitting layer 14 is provided (embedded) between the mutually adjacent strip-like base portions 15 in the semiconductor layer 22.

In the next process, the modified region 7 is formed by irradiating the laser light L to the object 1 to be processed. More specifically, first, as shown in FIGS. 1 and 10, the main surface 22s (surface 3) is placed on the support table 107 so as to be positioned on the side of the collecting lens 105. Here, the condensing lens 105 is an objective lens disposed closest to the main surface 22s among the lenses of the laser processing apparatus 100. Therefore, between the condensing lens 105 and the main surface 22s, no optical element such as another lens is interposed therebetween.

Next, the laser light L is incident on the condensing lens 105 (first process) for concentrating the laser light L on the object 1 to be processed. In the first process, the laser light L is incident on the condensing lens 105 in a state in which the intensity cross section of the laser light L is formed in an annular shape. The so-called intensity profile refers to The intensity distribution of the laser light L in a plane perpendicular to the optical axis Ax of the laser light L. In the first process, in order to form the intensity cross section of the laser light L incident on the condensing lens 105 in an annular shape, the optical system 113 is used.

The optical system 113 is disposed between the laser light source 101 (here, the beam splitter 103) and the collecting lens 105 in the light path of the laser light L. The optical system 113 has a function of forming an intensity cross section of the laser light L into an annular shape. Here, as an example, the optical system 113 includes a pair of mirrors 121 and 123 and a spatial light modulator 122. The mirror 121 is for deflecting the laser light L from the laser light source 101 (the beam splitter 103) toward the modulation surface 122s of the spatial light modulator 122. The mirror 123 is for deflecting the laser light L from the modulation surface 122s of the spatial light modulator 122 toward the collecting lens 105.

The spatial light modulator 122 is, for example, a LCOS-SLM (Liquid Crystal On Silicon Spatial Light Modulator). The spatial light modulator 122 has a modulation surface 122s including a liquid crystal layer or the like. The spatial light modulator 122 may, for example, present a predetermined modulation pattern to the modulation surface 122s. Thereby, the spatial light modulator 122 modulates the light incident on the modulation surface 122s, and changes the intensity profile to be emitted. Therefore, in the first process, the intensity cross section of the laser light L is formed into an annular shape by the spatial light modulator 122 exhibiting a predetermined modulation pattern.

Figure 11 is a diagram showing the intensity profile of the laser light. Fig. 11(a) is a view showing the intensity profile Pb of the general laser light L in a state in which it has not been modulated. Fig. 11(b) shows the intensity profile Pa of the laser light L in a state where the spatial light modulator 122 is modulated. As shown in Figure 11, light The department 113 uses a spatial light modulator 122 to convert a Gaussian beam having a solid circular intensity profile into a beam having an annular intensity profile. Here, the rounded area of the center of relatively high strength is cut off. Further, in the case of having any intensity profile, the condensing point P is set to be a solid circle. Further, in the case of an annular shape (when the outer edge and the inner edge of the ring are defined as a true circle (circular shape), the ratio of the outer diameter Do to the inner diameter Di (inner diameter Di) The outer diameter Do) can be appropriately performed in accordance with the accuracy of the desired cut surface or the material and structure of the object 1 to be processed, but it is preferably 50% or more and less than 85%. On the other hand, when it exceeds 85%, the size of the modified spot becomes unsettled with respect to the planned cutting line, and becomes unstable. As an example, when the effective beam diameter incident on the objective lens is 2.90 mm, the smallest inner diameter is 1.50 mm, and the largest inner diameter is 2.40 mm.

In the next process, as shown in Fig. 12, the laser beam 105 is used to condense the laser light L in the inside of the object 1 while the spot P of the laser light L is cut off. The predetermined line 5a is relatively moved, and the modified region 7 is formed inside the object 1 along the line to cut 5a (second process). More specifically, in the second process, first, the surface of the object 1 (the main surface 22s of the semiconductor layer 22) is used as the incident surface of the laser light L, and the light-converging point P of the laser light L is made to be opposite. It is in the state of the inside of the substrate 21. That is, the laser light L is condensed inside the substrate 21 via the semiconductor layer 22.

In the state thereof, by moving the object 1 to the laser light L relatively, along the line to cut 5a (toward the direction of the arrow in the drawing) The laser light L is irradiated (scanned) on the object 1 to be processed. At this time, the condensed point P of the laser light L is relatively moved from one end of the object 1 to the other end. In other words, in the second process, when viewed from a direction intersecting the main surface 22s, the condensed spot P is relatively moved along the line to cut 5a so as to pass through the plurality of light shielding regions SA.

Thereby, for example, at intervals corresponding to the pulse pitch of the laser light L ((relative moving speed of the processing object 1 with respect to the laser light L) / (frequency of pulse oscillation of the laser light L)), along the cutting schedule The line 5a is formed with a plurality of modified spots 7s inside the substrate 21. The modified region 7 is formed as a set of the modified spots 7s. Here, as will be described later, the modified spot 7s is also formed in a portion (a portion corresponding to the light shielding region SA) located at a position directly below the light shielding region SA when viewed from a direction intersecting the principal surface 22s. Therefore, here, in the portion corresponding to the light shielding area SA, the modified region 7 is not defective (interrupted). Here, the intensity cross section of the laser light L is also maintained in an annular shape when incident on the main surface 22s.

Further, in the second process, by adjusting the irradiation conditions of the laser light L, not only the inside of the substrate 21 but also cracks may be generated on the surface of the substrate 21 on the opposite side of the semiconductor layer 22 ( The back side of the object 1 is processed. Further, it is possible to carry out the cracks extending from the mutually adjacent modified spots 7s so as to be connected to each other.

Then, the second process is sequentially performed on all the planned cutting lines 5a, and the modified region 7 is formed inside the object 1 along all the planned cutting lines 5a. The cutting planned line 5a is set along the cleavage plane of the substrate 21 and the semiconductor layer 22 as described above. Therefore, in this In the second process, the modified region 7 is formed along the cleavage surface of the substrate 21 and the semiconductor layer 22.

Therefore, in the subsequent process, the object 1 to be processed can be cut by the splitting line 5a along with the modified region 7 as a starting point. The cutting of the object 1 along the line to cut 5a can be performed by applying a force to the object 1 in a direction in which the crack extending from the modified region 7 is extended. By processing the object 1 by cutting along the line to cut 5a, it is possible to obtain a plurality of rod-shaped objects to be processed including a plurality of wafers 10 (wafer portions 20) arranged along the line to cut 5a. Then, by cutting a plurality of rod-shaped objects to be processed along the line to cut 5b, it is possible to obtain the respective wafers 10 in which the substrate 11 is formed on the substrate 21 and the semiconductor layer 12 is formed on the semiconductor layer 22.

Moreover, the predetermined line 5b is cut and the entire position is in the light shielding area SA. Therefore, the cutting along the line to cut 5b is not a method of forming the modified region 7 in the inside of the substrate 21 by the incidence of the laser light L from the main surface 22s, but for example, laser melting can be used ( A method such as laser ablation) can be used.

As described above, in the object cutting method according to the present embodiment, the laser light L is incident on the collecting lens 105 in the first process. In the second process, the condensing light L is condensed in the inside of the object 1 by the condensing lens 105, and the condensed spot P is relatively moved along the line to cut 5a. The modified planned region 7 is formed inside the object 1 by the planned cutting line 5a. Here, the object 1 includes a main surface 22s including a light shielding area SA for shielding the laser light L. Further, in the second process, the main surface 22s is used as the incident surface of the laser light L, and the condensed spot P is relatively moved along the line to cut 5a so as to pass through the light shielding area SA.

Therefore, for example, as shown in FIG. 13(b), in the conventional method, a portion corresponding to the light shielding region SA in the inside of the object 1 is generated, and a defective portion of the modified region 7 is generated (middle way) There is no processed part) M. In the defective portion M of the modified region 7, the cracks extending from the mutually adjacent modified spots 7s are not continuous with each other. Therefore, when the object 1 is cut (cleared) along the modified region 7, the cut surface 10a may have a step G on the cut surface 10a due to meandering or the like. Here, the conventional method refers to the fact that, in the first process, the intensity profile of the laser light L is not formed into an annular shape as in FIG. 14(a), but is as shown in FIG. 14(b). The laser light L is incident on the collecting lens 105 in a state of a circular intensity cross section.

In the meantime, the present inventors have found that it is possible to suppress the occurrence of modification at a position corresponding to the light shielding area SA by concentrating the laser light L having an annular intensity cross section and then irradiating the object 1 to be processed. The missing portion M of the region 7. Further, in the object cutting method according to the present embodiment, in the first process, the laser light L having the intensity cross section formed into an annular shape is incident on the collecting lens 105. Therefore, according to the object cutting method, as shown in Fig. 13(a), it is possible to suppress the occurrence of the defective portion M of the modified region 7 at a position corresponding to the light shielding region SA. As a result, it is possible to suppress the occurrence of defects in the cut surface 10a such as the step difference G on the cut surface 10a.

Here, one of the factors that can achieve the above effects The wiseness of the inventors of the present invention will be explained. As shown in Fig. 14(c), the laser light L having an annular intensity cross section and the laser light Ln having a solid (conventional) intensity profile in a solid circular shape are adapted to the position of the light shielding area SA. The relationship has a different transmittance with respect to the object 1 to be processed. This point will be explained in more detail. First, as shown in Fig. 14 (a) and (b), the amount of deviation between the center of the beam of the laser light L and Ln and the center of the light shielding region SA is taken as Lo. Here, when the center of the beam of the laser light L, Ln coincides with the center of the light shielding area SA, the amount of deviation Lo is zero.

As described above, when the object 1 is relatively moved with respect to the laser light L, Ln, the amount of deviation Lo is shifted from the negative side to the positive side. At this time, as shown by the graph of the single-dotted line in Fig. 14(c), the transmittance of the laser light Ln having a general intensity profile becomes smaller as the amount of deviation Lo approaches zero. Further, the transmittance of the laser light Ln is minimized when the amount of deviation Lo is 0, and for example, there is a loss of about 65%.

On the other hand, as shown by the graph of the solid line in FIG. 14( c ), the transmittance of the laser beam L having an annular intensity cross section becomes smaller as the amount of deviation Lo approaches zero. The amount of deviation Lo is flat between -1 and 1. The transmittance at this time is larger than the transmittance of the general laser light L, for example, a loss of about 40%. This phenomenon can also be understood from Figure 15. That is, as shown in Fig. 15, the intensity of the circular laser light L on the optical axis is smaller than the intensity of the general laser light Ln on the optical axis, even from the incident surface of the laser light (Fig. Medium "z") is also difficult to attenuate.

That is to say, the laser light L has less energy loss when passing through the light shielding area SA than the laser light Ln. Therefore, immediately below the light shielding area SA, the energy of the laser light L at the condensing point P is larger than that of the laser light Ln. As a result, when the laser light L is used, the modified region 7 can be sufficiently formed even under the light shielding region SA, and the defective portion M of the modified region 7 is not easily generated. I believe that the above explanation is one of the reasons for achieving the above effects. Moreover, the experimental conditions used for carrying out the above investigation are as follows.

The outer diameter (beam outer diameter) of the intensity profile of the laser light L located on the incident surface of the laser beam L of the objective lens is: 2.88 mm.

The inner diameter (beam inner diameter) Di of the intensity profile of the laser light L located on the incident surface of the laser beam L of the objective lens is 2.0 mm.

The outer diameter of the beam of the laser light Ln located at the incident surface of the laser light Ln of the objective lens is 2.88 mm. The width of the light shielding area SA is 1.0 mm.

However, the experiment for performing the above investigation is not an experiment of measuring the transmittance and the beam diameter of the object 1 in the object, but on the objective lens. This is because it is difficult to measure the transmittance in the object 1 to be processed. In this experiment, the beam diameter of the laser light L incident on the objective lens was 5.0 mm, and the diameter of the objective lens was 2.88 mm. Since the beam profile Do of the laser light L incident on the objective lens is determined by the diameter of the objective lens, in this case, it is 2.88 mm as described above, and the inner diameter Di is 2.0 mm. On the other hand, in this experiment, the light shielding area SA was formed on the objective lens. Therefore, the width of the light shielding area SA described above is converted into a wide width on the incident surface of the objective lens.

The experiment under such conditions is equivalent to the experiment under the actual condition of the object 1 for the following reasons. That is, first, as the outer diameter Do of the beam, the smaller of the beam diameter of the laser light L and the lens aperture is employed. Further, in the direction in which the object to be processed 1 intersects with the incident surface of the laser light L, it is assumed that a geometrical similarity relationship can be established in a position where the focused point P is sufficiently separated. In addition, the outer diameter and the inner diameter of the beam of the laser beam L of the laser beam L incident on the object 1 are set to Dso and Dsi, respectively, and the ratio is set to γ. At this point, the following relationship can be established.

γ=Dsi/Dso=Di/Do‧‧‧(1)

In addition, the width of the actual light shielding area SA located in the object 1 is Ws, and the width of the light shielding area SA at the position of the incident surface of the objective lens is set as described above. For W, the following relationship can be further established.

Γo=Ws/Dso=W/Do‧‧‧(2)

Γi=Ws/Dsi=W/Di‧‧‧(3)

γ=γo/γi‧‧‧(4)

That is, the ratio of the outer diameter of the beam of the laser light L to the inner diameter of the beam (γ), the ratio of the outer diameter of the beam of the laser light L to the width of the light shielding area SA (γo), and the inner diameter of the beam of the laser beam L are The ratio (γi) of the width of the light-shielding region SA is equivalent between the experiment and the value of the experiment in the object 1 to be processed. From this, it can be said that this experiment is equivalent to the experiment under the actual conditions of the object 1 at least under the above examination.

Further, for another factor shown in the above effect The wiseness of the inventors of the present invention will be explained. According to the present inventors, it has been confirmed that the condensed spot when the laser light L having the annular intensity cross section is condensed to the maximum extent is condensed as compared with the laser light Ln having the general intensity profile. The point is relatively elongated along the optical axis of the laser light L, and the sectional area along the optical axis becomes large.

From this point, it is understood that the energy input to the object 1 can be increased at the condensed point of the laser light L compared to the condensed point of the laser light Ln. As a result, in the case where the laser light L is used, even if it is directly under the light shielding area SA, sufficient energy can be input for the process of forming the modified region 7, and the defective portion M of the modified region 7 is not easily generated. This point is considered to be another cause for achieving the above effects.

Here, in the object cutting method of the present embodiment, the object 1 is a semiconductor layer 22 for a semiconductor laser including gallium nitride. The semiconductor layer 22 includes a main surface 22s. Moreover, the light shielding area SA is a strip-shaped high-density defect area provided in the semiconductor layer 22 so as to extend in a direction crossing the line to cut 5a. Further, the cutting planned line 5a is set along the cleavage plane of the substrate 21 and the semiconductor layer 22.

In the case of a resonator that forms a semiconductor laser by cleaving, the cleavage plane is required to be mirrored. Therefore, it is particularly important to suppress the deterioration of the cut surface (opening surface). According to the object cutting method of the present embodiment, the line to cut 5a is set along the opening surface of the semiconductor layer 22 for the semiconductor laser and the substrate 21, along the line to cut 5a. As described above, it can be formed in such a manner that the defective portion M is not generated. Into the modified area 7. Therefore, it is possible to surely suppress the occurrence of defects in the cut surface (opening surface) and to mirror the cut surface.

Further, in the object cutting method according to the present embodiment, in the first process, the spatial light modulator 122 exhibiting a predetermined modulation pattern is used to implement the intensity profile of the laser light L as Ring-shaped. Therefore, by controlling the predetermined modulation pattern of the spatial light modulator 122, the annular shape of the intensity profile of the laser light L can be dynamically changed. Therefore, the formation of the appropriate modified region 7 can be performed in accordance with the material of the object 1 to be processed or the required cutting accuracy.

The above embodiment is an embodiment of the object cutting method in the same manner as the present invention. Therefore, the method of cutting the object to be processed in the same manner of the present invention is not limited to the above embodiment. In the method of cutting the object to be processed in the same manner as in the present invention, the above-described embodiment can be arbitrarily changed within the scope of not changing the essence of each of the claims.

For example, the object to be processed in the object cutting method in the same manner as in the present invention is not limited to the above-described object 1 to be processed. In other words, the object to be processed may be a semiconductor layer 22 (semiconductor layer 12) which does not include a semiconductor laser including gallium nitride, and may be, for example, TEG. Further, the light shielding area SA is not limited to a high-density defect area, and may be a wiring or the like. In other words, the object to be processed may be implemented as an arbitrary object provided with an arbitrary shielding region with respect to the incident surface of the laser light.

Further, the optical system 113 is not limited to being used as long as it has a function of setting the intensity cross section of the laser light L into a ring shape. Inter-light modulator 122. For example, the optical system 113 may be an axicon lens pair. Alternatively, the optical system 113 may be a reticle member provided with a central portion of the beam spot of the laser light L that is disposed in a circular shape with respect to the condensing lens 105. At this time, the mask member may be directly provided on the incident surface of the laser light L of the collecting lens 105 or may be held separately from the incident surface.

In addition, the method of cutting the object to be processed in the present embodiment is not limited to the object to be processed having the light-shielding region on the incident surface as described above, and is also effective for the object to be processed having no light-shielding region. In other words, even in the case where the object to be processed having no light-shielding region is condensed and irradiated with laser light having a general intensity profile, the defective portion of the modified region may be suddenly generated. On the other hand, according to the object cutting method of the present embodiment, it is possible to reduce the occurrence of a defective portion in the sudden modification region, and it is possible to suppress the defective portion.

Further, in the above embodiment, the intensity profile Pa of the laser light L is formed into an annular shape. Further, as one of the annular intensity sections Pa, as shown in FIG. 11, the case where the outer edge and the inner edge of the annular ring are both true circles is exemplified. However, the strength profile Pa may be an annular shape, and the outer edge and the inner edge are not limited to a true circle. Another example of the annular intensity profile Pa will be described below.

Fig. 16 is a view showing a modification of the annular strength cross section. Fig. 16(a), as described above, is a case where the outer edge Co of the intensity profile Pa and the inner edge Ci are both true circles. In contrast, Figure 16 (b) to (d) are examples in which the outer edge Co is a true circle and the inner edge Ci is an ellipse. In particular, in Figs. 16(b) and 16(c), the major axes of the ellipses of the inner edges Ci are arranged so as to intersect each other (vertically intersect). Further, in Fig. 16(d), the major axis of the ellipse of the inner edge Ci is inclined.

Fig. 17 is a view showing another modification of the annular strength cross section. In the example shown in Fig. 17, the outer edge Co of the strength profile Pa is implemented as an ellipse. In particular, in Fig. 17(a), the inner edge Ci is implemented as a true circle. Further, in Fig. 17 (b) to (d), the outer edge Co and the inner edge Ci are both formed into an ellipse. In Figs. 17(b) and 17(c), the major axes of the ellipse of the inner edge Ci are arranged so as to intersect each other (vertically intersect). Further, in Fig. 17(d), the major axis of the ellipse of the inner edge Ci is inclined.

Fig. 18 is a view showing another modification of the annular strength cross section. In the example shown in Fig. 18, the outer edge Co of the strength profile Pa is implemented as an ellipse. In particular, in the example of Fig. 18, the ellipse of the outer edge Co is inclined. In Fig. 18(a), the inner edge Ci is implemented as a true circle. Further, in Figs. 18(b) to (d), the outer edge Co and the inner edge Ci are both formed into an ellipse. In Figs. 18(b) and 18(c), the major axes of the ellipses of the inner edges Ci are arranged so as to intersect each other (vertically intersect). Further, in Fig. 18(d), the major axis of the ellipse of the inner edge Ci is inclined.

Fig. 19 is a view showing another modification of the annular strength cross section. In the example of Fig. 19(a), the outer edge Co and the inner edge Ci is also implemented as an ellipse, and their respective centers (axes) are not identical. In the example of Fig. 19(b), the outer edge Co is a true circle, and the inner edge Ci thereof is embodied as an ellipse. In particular, in the example of Fig. 19(b), the major axis of the ellipse of the inner edge Ci is made larger than the diameter of the true circle of the outer edge Co. Further, in the example of Fig. 19(c), the single outer edge Co includes a plurality of (here, two) inner edges Ci of the ellipse.

As described above, the annular intensity profile Pa of the laser light L may be formed by a ring or a ring including a partial ring by including a circular outer edge and an inner edge of a true circle and an ellipse. The same effect as the above embodiment can be achieved in either case.

[Industrial availability]

The present invention can provide a method of cutting an object to be processed which can suppress the failure of the cut surface.

1‧‧‧Processing objects

3‧‧‧ Surface of the object to be processed

5‧‧‧ cut the booking line

A‧‧‧ Relative direction of movement of laser light along the line to cut

Claims (4)

A method of cutting an object to be processed is a method of cutting an object to be cut along a line to be cut, wherein the object has a main surface including light shielding to shield laser light In the first process, the laser beam is incident on a condensing lens for concentrating the laser light on the object to be processed, and a second process is performed by using the condensing lens. The laser light is condensed inside the object to be processed, and the condensing point of the laser light is relatively moved along the line to cut along the line to cut, thereby forming a change in the inside of the object to be processed along the line to cut. The light shielding region is overlapped with a part of the planned cutting line when viewed from a direction intersecting the main surface; and in the first process, the intensity cross section of the laser light is rounded The laser light is incident on the condensing lens in an annular state; in the second process, the main surface is an incident surface of the laser light, and intersects from the main surface When the direction is observed, the light collecting point is relatively moved along the line to cut along the light shielding area. The method of cutting an object to be processed according to claim 1, wherein the object to be processed has a semiconductor layer for a semiconductor laser including gallium nitride, and the semiconductor layer includes the main surface. The light shielding area is oriented to intersect with the above-mentioned cutting planned line The direction extending is provided in a strip-shaped high-density defect region of the semiconductor layer, and the planned cutting line is set along a cleavage surface of the semiconductor layer. The method of cutting an object according to claim 1 or 2, wherein in the first process, the intensity profile is implemented by a spatial light modulator that exhibits a predetermined modulation pattern. Ring-shaped. The method of cutting an object according to any one of claims 1 to 3, wherein a ratio of an outer diameter to an inner diameter of the strength cross section is 50% or more and less than 85%.