JP5282812B2 - Workpiece processing method and workpiece division method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a machining method for forming a division-starting point on a workpiece by which optical absorption in a machining trace is reduced, efficiency of taking out light from sapphire is enhanced and high-speed processing can be performed, and to provide a laser beam machining apparatus for materializing the machining method. <P>SOLUTION: The workpiece is irradiated with a pulsed laser beam in such a manner that an irradiation region for each unit pulsed beam of an ultrashort pulsed laser beam is formed discretely on the workpiece. By an impact or stress caused by irradiating an irradiation position with each unit pulsed beam, cleavage or parting of the workpiece is successively generated between the irradiation regions, thus forming a division-starting point on the workpiece. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a laser processing method for processing a workpiece by irradiating a laser beam.

  Various techniques (hereinafter simply referred to as laser processing or laser processing technology) for processing a workpiece by irradiating pulsed laser light are already known (see, for example, Patent Document 1 to Patent Document 4).

  Patent Document 1 discloses that when a die as a workpiece is divided, a groove having a V-shaped cross section (break groove) is formed along a planned dividing line by laser ablation, and the die is started from this groove. Is a method of dividing On the other hand, Patent Document 2 discloses that a laser beam in a defocused state is irradiated along a planned division line of an object to be processed (divided object), so that the irradiated region is less crystallized than the surroundings. In this method, a melt-modified region (modified region) having a substantially V-shaped cross section is generated, and the workpiece is divided starting from the lowest point of the melt-modified region.

  In any case where the division starting points are formed using the techniques disclosed in Patent Document 1 and Patent Document 2, the subsequent division is performed satisfactorily, so that it is uniform along the planned division line direction that is the scanning direction of the laser light. It is important to form a V-shaped cross section (groove cross section or altered region cross section) having a simple shape. For this purpose, for example, the irradiation of the laser beam is controlled so that the irradiated region (beam spot) of the laser beam for each pulse overlaps before and after.

  For example, when the repetition frequency (unit: kHz), which is the most basic parameter of laser processing, is R, and the scanning speed (unit: mm / sec) is V, the ratio V / R of both is the center distance of the beam spot. However, in the techniques disclosed in Patent Document 1 and Patent Document 2, laser light irradiation and scanning are performed under the condition that V / R is 1 μm or less so that beam spots overlap each other.

  Further, in Patent Document 3, a modified region is formed inside the substrate by aligning a condensing point inside the substrate having a laminated portion on the surface and irradiating laser light, and this modified region is defined as a starting point of cutting. An embodiment is disclosed.

  Further, in Patent Document 4, a laser beam scan is repeated a plurality of times for one separation line to deepen a groove portion and a modification portion that are continuous in the separation line direction and an internal modification portion that is not continuous in the separation line direction. The aspect formed in the up-down direction is disclosed.

  On the other hand, Patent Document 5 discloses a processing technique using an ultrashort pulse laser beam having a pulse width of the order of psec, and by adjusting the focused spot position of the pulse laser beam, a workpiece (plate). A mode is disclosed in which minute dissolution marks are formed in which micro cracks are clustered from the surface layer portion to the surface, and a linear separation facilitating region in which these dissolution marks are connected is disclosed.

JP 2004-9139 A International Publication No. 2006/062017 JP 2007-83309 A JP 2008-98465 A JP 2005-271563 A

  The method of forming the split starting point with laser light and then splitting with a breaker is more automated, faster, more stable and more accurate than diamond scribing, which is a conventional mechanical cutting method. Is advantageous in terms of sex.

  However, when a work piece in which a light emitting element structure such as an LED structure is formed on a substrate made of a hard and brittle and optically transparent material such as sapphire is divided into chips (divided pieces), The resulting processed traces absorb light generated inside the light emitting element, and there is a problem that the light extraction efficiency from the element is reduced. In particular, the problem associated with the light emitting device structure using a sapphire substrate having a high refractive index is significant.

  The inventor of the present invention, as a result of intensive studies, forms fine irregularities using the cleavage or tearing property of the workpiece at the processing position of the workpiece, and the total reflection at the position. Lowering the rate solves the above-mentioned problems and is effective in realizing higher light extraction efficiency than diamond scribing without laser processing traces. The knowledge that it can be suitably performed by using an ultra-short pulse laser beam was obtained.

  In Patent Document 1 to Patent Document 5, it is not recognized that there is recognition of such a problem, and no disclosure or suggestion is made regarding an aspect in which the cleavage property or cleavage property of the workpiece is used.

  The present invention has been made in view of the above problems, and the light absorption at the processing trace is reduced, and the light extraction efficiency from sapphire is increased, and the division starting point is formed on the workpiece capable of high-speed processing. An object of the present invention is to provide a processing method and a laser processing apparatus that realizes the processing method.

In order to solve the above-mentioned problems, the invention of claim 1 is a processing method for forming a split starting point on a workpiece having a light emitting element structure provided on a substrate made of an optically transparent material. The pulse laser beam is formed so that the irradiated region for each unit pulse beam of the laser beam is discretely formed in an equivalent direction to two different cleavage or cleavage easy directions of the workpiece. Irradiating the surface of the workpiece , thereby forming a starting point for division in the workpiece by sequentially generating cleavage or cleavage of the workpiece between the irradiated regions. It is characterized by that.

Invention of Claim 2 is the processing method of Claim 1, Comprising: The said pulsed laser beam is short pulsed light whose pulse width is 100 psec or less, It is characterized by the above-mentioned.

The invention of claim 3 is a method of dividing a workpiece, wherein the workpiece on which a division start point is formed by the method of claim 1 or claim 2 is divided along the division start point. It is characterized by that.

According to the inventions of claims 1 to 3 , the occurrence of alteration or scattering of the work piece is kept locally, while the work piece is actively cleaved or cleaved. It is possible to form the dividing starting point for the workpiece at a much higher speed than that.

In particular, as a split cross section when obtained by dividing the workpiece along the division originating points, which form the shape in the vicinity of the surface of the workpiece, irregularities due to each other cleavage or parting planes adjacent formed, division originating points Can be formed. When the work piece is a substrate made of a light and brittle and optically transparent material such as sapphire and a light emitting element structure such as an LED structure is formed, such a concavo-convex shape on the divided cross section of the substrate By forming the light emitting element, the light emission efficiency of the light emitting element can be improved.

It is a figure for demonstrating the process by a 1st process pattern. It is an optical microscope image about the surface of the to-be-processed object which formed the division | segmentation starting point by the cleavage / cleaving process by a 1st process pattern. It is a SEM image from the surface (c surface) to a section after dividing a sapphire C surface substrate which formed a division starting point by processing concerning the 1st processing pattern along this division starting point. It is a figure which shows typically the processing mode by a 2nd processing pattern. It is an optical microscope image about the surface of the to-be-processed object which formed the division | segmentation origin by the cleavage / cleaving process by a 2nd process pattern. It is a SEM image from the surface (c surface) to a section after dividing a sapphire c plane substrate which formed a division starting point by processing concerning the 2nd processing pattern along this division starting point. It is a figure which shows typically the processing mode by the 3rd processing pattern. It is a figure which shows the relationship between the process planned line in the 3rd process pattern, and the formation planned position of a to-be-irradiated area | region. It is a schematic diagram which shows roughly the structure of the laser processing apparatus 50 which concerns on embodiment of this invention. It is a figure which shows the structure of the optical path setting means 5 typically.

<Processing principle>
First, the principle of processing realized in each embodiment of the present invention described below will be described. In general, the processing performed in the present invention is performed by irradiating the upper surface of the workpiece while scanning with a pulsed laser beam (hereinafter, also simply referred to as laser beam), so that the irradiation region of each pulse is irradiated. Cleaving or cleaving of the workpiece is sequentially generated between them, and a starting point (dividing starting point) for division is formed as a continuous surface of the cleaved surface or the cleaved surface formed in each.

  Note that in this embodiment mode, cleavage refers to a phenomenon in which a workpiece is cracked substantially regularly along a crystal plane other than the cleavage plane, and the crystal plane is referred to as a cleavage plane. In addition to cleaving and cleaving that are microscopic phenomena completely along the crystal plane, cracks that are macroscopic cracks may occur along a substantially constant crystal orientation. Depending on the substance, only one of cleavage, cleaving, or cracking mainly occurs, but in the following, in order to avoid complicated explanation, cleavage / cleavage is not distinguished from each other without distinguishing cleavage, cleaving, and cracking. Collectively called open. Further, the above-described processing may be simply referred to as cleavage / dehiscence processing or the like.

  In the following, an example will be described in which the workpiece is a hexagonal single crystal substance, and the directions of the a1 axis, a2 axis, and a3 axis are cleavage / cleavage easy directions. For example, a c-plane sapphire substrate corresponds to this. The a1 axis, a2 axis, and a3 axis of the hexagonal crystal are symmetric with each other at an angle of 120 ° in the c plane. The machining according to the present invention has several patterns depending on the relationship between the direction of these axes and the direction of the planned machining line (the planned machining direction). Hereinafter, these will be described. In the following, the laser light irradiated for each individual pulse is referred to as unit pulse light.

<First processing pattern>
The first processing pattern is an aspect of cleavage / dehissing processing when any of the a1 axis direction, the a2 axis direction, and the a3 axis direction is parallel to the planned processing line. More generally speaking, this is a processing mode in the case where the cleavage / cleavage easy direction matches the direction of the planned processing line.

  FIG. 1 is a diagram schematically showing a processing mode by the first processing pattern. FIG. 1 illustrates the case where the a1 axis direction and the planned machining line L are parallel. FIG. 1A is a diagram illustrating an azimuth relationship between the a1 axis direction, the a2 axis direction, the a3 axis direction, and the planned processing line L in such a case. FIG. 1B shows a state in which the unit pulse light of the first pulse of the laser light is irradiated to the irradiated region RE1 at the end of the processing line L.

  In general, irradiation with unit pulse light gives high energy to a very small region of the workpiece, and therefore, such irradiation is equivalent to the irradiation region of the unit pulse light (laser light) on the surface to be irradiated or the target. It causes alteration, melting, evaporative removal, etc. of substances in a range wider than the irradiation area.

  However, if the irradiation time of the unit pulse light, that is, the pulse width is set to be extremely short, a substance that is narrower than the spot size of the laser light and exists in the substantially central region of the irradiated region RE1 obtains kinetic energy from the irradiated laser light. While being scattered or altered in a direction perpendicular to the irradiated surface, the impact and stress generated by the irradiation of unit pulse light including reaction force caused by the scattering are around the irradiated region, In particular, it acts in the a1 axis direction, the a2 axis direction, and the a3 axis direction, which are easy cleavage / cleavage directions. As a result, micro-cleavage or cleaving partially occurs along the direction while maintaining an apparent contact state, or thermal distortion is inherent even without cleaving or cleaving. A state occurs. In other words, it can be said that the irradiation with the ultra-short pulse unit pulse light acts as a driving force for forming a weak intensity portion that is substantially linear in a top view toward the cleavage / cleavage easy direction.

  In FIG. 1 (b), the weak strength portion W1 in the + a1 direction that coincides with the extending direction of the planned processing line L among the weak strength portions formed in each of the above cleavage / cleavage easy directions is schematically shown by a broken line arrow. Is shown.

  Subsequently, as shown in FIG. 1C, the second unit pulse light of the laser light is irradiated, and the irradiated region RE2 is located on the processing planned line L at a position away from the irradiated region RE1 by a predetermined distance. As in the case of the first pulse, a weak intensity portion is formed in the second pulse along the easy cleavage / cleavage direction. For example, the weak strength portion W2a is formed in the −a1 direction, and the weak strength portion W2b is formed in the + a1 direction.

  However, at this time, the weak intensity portion W1 formed by the irradiation of the unit pulse light of the first pulse exists in the extending direction of the weak intensity portion W2a. That is, the extending direction of the weak strength portion W2a is a location where cleavage or cleavage can occur with less energy than other locations. Therefore, actually, when the unit pulse light of the second pulse is irradiated, the impact or stress generated at that time propagates to the easy-cleavage / cleavage direction and the weak intensity part existing ahead, and the weak intensity part From W2a to the weak intensity portion W1, complete cleavage or cleavage occurs almost at the moment of irradiation. As a result, a cleavage / cleavage plane C1 shown in FIG. 1 (d) is formed. The cleavage / cleavage surface C1 can be formed to a depth of about several μm to several tens of μm in the direction perpendicular to the drawing of the workpiece. Moreover, as will be described later, on the cleavage / cleavage plane C1, as a result of receiving a strong impact or stress, the crystal plane slips and undulations occur in the depth direction.

  Then, as shown in FIG. 1 (e), the irradiated regions RE1, RE2, RE3, RE4,... Are sequentially irradiated with unit pulse light by scanning the laser light along the planned processing line L. As a result, cleavage / cleavage surfaces C2, C3,... Are sequentially formed accordingly. It is the cleavage / dehissing process in the first machining pattern that continuously forms the cleavage / dehiscence surface in such a manner.

  That is, in the first processing pattern, a plurality of irradiated regions that exist discretely along the planned processing line L and the cleavage / cleavage surfaces formed between the plurality of irradiated regions as a whole This is the starting point for dividing the workpiece along the planned machining line L. After the formation of the division starting point, the workpiece can be divided in a mode generally along the planned processing line L by performing division using a predetermined jig or apparatus.

  In order to realize such cleavage / cleavage processing, it is necessary to irradiate a short pulse laser beam with a short pulse width. Specifically, it is necessary to use laser light having a pulse width of 100 psec or less. For example, it is preferable to use laser light having a pulse width of about 1 psec to 50 psec.

  On the other hand, it is preferable that the irradiation pitch of unit pulse light (center distance of irradiated spots) is about 4 μm to 15 μm at the maximum. If the irradiation pitch is larger than this, the formation of the weak strength portion in the cleavage / cleavage easy direction may not progress to such an extent that a cleavage / cleavage surface can be formed. From the viewpoint of reliably forming the division starting point consisting of

  Now, when the repetition frequency of laser light is R (kHz), unit pulse light is emitted from the laser light source every 1 / R (msec). When the laser beam moves relative to the workpiece at a speed V (mm / sec), the irradiation pitch Δ (μm) is determined by Δ = V / R. Therefore, the scanning speed V and the repetition frequency of the laser beam are determined so that Δ is about several μm. For example, the scanning speed V is preferably about 50 mm / sec to 3000 mm / sec, and the repetition frequency R is preferably about 10 kHz to 200 kHz. Specific values of V and R may be appropriately determined in consideration of the material of the workpiece, the absorption rate, the thermal conductivity, the melting point, and the like.

The laser beam is preferably irradiated with a beam diameter of about 1 μm to 10 μm. In such a case, the peak power density upon laser light irradiation is approximately 0.1 TW / cm ² to several tens TW / cm ² .

  Further, the laser beam irradiation energy (pulse energy) may be appropriately determined within the range of 0.1 μJ to 50 μJ.

  FIG. 2 is an optical microscope image of the surface of the workpiece on which the division starting points are formed by the cleavage / cleavage processing in the first processing pattern. Specifically, the sapphire c-plane substrate is a workpiece, and on the c-plane, processing is performed to discretely form irradiated spots at intervals of 7 μm with the a1 axis direction as the extending direction of the processing line L. The results are shown. The result shown in FIG. 2 suggests that the actual workpiece is processed by the mechanism described above.

  Further, FIG. 3 shows an SEM (scanning electron microscope) from the surface (c-plane) to the cross-section after dividing the sapphire c-plane substrate on which the division starting points are formed by the processing according to the first processing pattern along the division starting points. ) In FIG. 3, the boundary portion between the surface and the cross section is indicated by a broken line.

  The elongated triangular or needle-like region having a longitudinal direction from the surface of the workpiece, which is present in the range of about 10 μm from the surface, is observed in FIG. 3 and is irradiated with unit pulse light. This is a region where a phenomenon such as alteration or scattering removal has occurred directly (hereinafter referred to as a direct alteration region). Then, an area observed between the directly altered regions, which is observed such that a number of streak portions having a longitudinal direction in the left-right direction as viewed in the drawing are connected at a submicron pitch in the vertical direction as viewed in the drawing, is cleaved / dehised. Surface. Below these directly altered regions and cleavage / cleavage surfaces are the divided surfaces formed by the division.

  In addition, what is actually observed as a streak portion in the SEM image is a minute unevenness having a height difference of about 0.1 μm to 1 μm formed on the cleavage / dehiscence surface. Such irregularities are formed by applying a strong impact or stress to the work piece by irradiation with unit pulse light when cleaving / cleaving a hard brittle inorganic compound such as sapphire. It is formed by sliding.

  Although such fine irregularities exist, from FIG. 3 it is judged that the surface and the cross section are almost orthogonal with respect to the wavy line as a boundary, so that the fine irregularities are allowed as a processing error. It can be said that the workpiece can be divided substantially perpendicularly to the surface thereof by forming the dividing starting point by the first processing pattern and dividing the workpiece along the dividing starting point.

  As will be described later, it may be preferable to positively form such fine irregularities. For example, the effect of improving the light extraction efficiency that is remarkably obtained by the processing by the second processing pattern described below may be exhibited to some extent by the processing by the first processing pattern.

<Second processing pattern>
The second processing pattern is an aspect of cleavage / dehiscence processing when any of the a1 axis direction, the a2 axis direction, and the a3 axis direction is perpendicular to the processing planned line. In addition, the conditions of the laser beam used in a 2nd process pattern are the same as that of a 1st process pattern. More generally speaking, machining in the case where the direction equivalent to two different cleavage / cleavage directions (the direction of the symmetry axis of the two cleavage / cleavage easy directions) is the direction of the planned machining line. It is an aspect.

  FIG. 4 is a diagram schematically showing a processing mode by the second processing pattern. FIG. 4 illustrates a case where the a1 axis direction and the planned machining line L are orthogonal to each other. FIG. 4A is a diagram illustrating an azimuth relationship between the a1 axis direction, the a2 axis direction, the a3 axis direction, and the planned machining line L in such a case. FIG. 4B shows a state in which the unit pulse light of the first pulse of the laser light is irradiated to the irradiated region RE11 at the end of the processing line L.

  Also in the case of the second processing pattern, the weak intensity portion is formed by irradiating the unit pulse light of the ultrashort pulse, similarly to the first processing pattern. In FIG. 4B, among the weak strength portions formed in each of the above cleavage / cleavage easy directions, the weak strength portions W11a and W12a in the −a2 direction and the + a3 direction close to the extending direction of the processing line L are shown. This is schematically indicated by a broken arrow.

  Then, as shown in FIG. 4C, the unit pulse light of the second pulse of the laser light is irradiated, and the irradiated region RE12 is located at a position away from the irradiated region RE11 on the planned processing line L by a predetermined distance. When formed, similarly to the first pulse, a weak intensity portion is formed along the easy cleavage / cleavage direction in the second pulse. For example, a weak strength portion W11b is formed in the -a3 direction, a weak strength portion W12b is formed in the + a2 direction, a weak strength portion W11c is formed in the + a3 direction, and a weak strength portion W12c is formed in the -a2 direction. Will be.

  Also in this case, as in the case of the first processing pattern, the weak intensity portions W11a and W12a formed by the irradiation of the first unit pulse light are present in the extending direction of the weak intensity portions W11b and W12b, respectively. Actually, when the unit pulse light of the second pulse is irradiated, the impact or stress generated at that time propagates to the easy-cleavage / cleavage direction and the weak intensity portion existing ahead. That is, as shown in FIG. 4D, cleavage / cleavage surfaces C11a and C11b are formed. Also in this case, the cleavage / cleavage surfaces C11a and C11b can be formed to a depth of about several μm to several tens of μm in the direction perpendicular to the drawing of the workpiece.

  Subsequently, as shown in FIG. 4E, when the laser beam is scanned along the planned processing line L and the irradiated regions RE11, RE12, RE13, RE14,. The cleaved / cleavage surfaces C11a and C11b, C12a and C12b, C13a and C13b, C14a and C14b. It will be formed.

  As a result, a state in which the cleavage / cleavage plane is positioned symmetrically with respect to the planned processing line L is realized. In the second machining pattern, the plurality of irradiated areas discretely present along the planned machining line L and the cleavage / cleavage surfaces present in a zigzag form as a whole are intended to process the workpiece. It becomes a division starting point when dividing along L.

  FIG. 5 is an optical microscope image of the surface of the workpiece on which the division starting points are formed by the cleavage / cleavage processing in the second processing pattern. Specifically, the sapphire C-plane substrate is a workpiece, and the irradiated spots are discretely spaced at intervals of 7 μm on the C-plane with the direction orthogonal to the a1 axis direction as the extending direction of the processing line L. The result of processing to be formed is shown. From FIG. 5, even in an actual workpiece, a zigzag (zigzag) cleavage / cleavage surface is observed in the same manner as that schematically shown in FIG. 4 (e). Such a result suggests that the actual workpiece is processed by the mechanism described above.

  FIG. 6 is an SEM image from the surface (c-plane) to the cross-section after dividing the sapphire C-plane substrate on which the division starting points are formed by processing according to the second processing pattern along the division starting points. In FIG. 6, the boundary between the surface and the cross section is indicated by a broken line.

  From FIG. 6, in the range of about 10 μm from the surface of the cross section of the workpiece after division, the cross section of the workpiece has irregularities corresponding to the staggered arrangement schematically shown in FIG. It is confirmed that it has. It is the cleavage / cleavage surface that forms such irregularities. In addition, the uneven | corrugated pitch in FIG. 6 is about 5 micrometers. As in the case of the processing by the first processing pattern, the cleavage / cleavage surface is not flat, and unevenness of a submicron pitch is generated due to slippage on a specific crystal plane due to irradiation of unit pulse light. Yes.

  Further, it is the cross section of the directly altered region that extends from the surface portion in the depth direction corresponding to the position of the convex and concave portions. Compared to the directly altered region formed by the processing by the first processing pattern shown in FIG. 3, the shape is non-uniform. Further, below the direct alteration region and the cleavage / cleavage surface is a divided surface formed by the division.

  In the case of processing by the second processing pattern, in addition to the submicron pitch unevenness formed on the cleavage / cleavage surface, the adjacent cleavage / cleavage surfaces form unevenness with a pitch of about several μm. In a mode of forming a cross-section having such a concavo-convex shape, a work piece in which a light emitting element structure such as an LED structure is formed on a substrate made of a hard and brittle and optically transparent material such as sapphire is divided into chips This is effective when dividing into units. In the case of a light-emitting element, if the light generated inside the light-emitting element is absorbed at the location of the processing mark formed on the substrate by laser processing, the light extraction efficiency from the element will be reduced, When the unevenness as shown in FIG. 6 is intentionally formed on the processed cross section of the substrate by performing the processing with the second processing pattern, the total reflectance at the position is lowered and higher in the light emitting element. Light extraction efficiency will be realized.

<Third processing pattern>
In the third processing pattern, a point using an ultra-short pulse laser beam, a1 axis direction, a2 axis direction, or a3 axis direction is perpendicular to the planned processing line (in two different cleavage / cleavage easy directions). On the other hand, in the point that the equivalent direction is the direction of the planned processing line), the laser beam irradiation mode is different from that of the second processing pattern.

  FIG. 7 is a diagram schematically showing a processing mode by the third processing pattern. FIG. 7 illustrates a case where the a1 axis direction and the planned machining line L are orthogonal to each other. FIG. 7A is a diagram illustrating an azimuth relationship between the a1 axis direction, the a2 axis direction, the a3 axis direction, and the planned processing line L in such a case.

  In the second machining pattern described above, the laser beam is exactly in the middle of the a2 axis direction and the a3 axis direction, which are the extending directions of the planned machining line L, under the same orientation relationship as that shown in FIG. Along the direction (equivalent to the a2 axis direction and the a3 axis direction). In the third machining pattern, instead of this, as shown in FIG. 7B, the individual irradiated regions are staggered in an aspect along the two easy cleavage / cleavage directions sandwiching the machining line L. The unit pulse light for forming each irradiated region is irradiated so as to be formed in a zigzag manner. In the case of FIG. 7, irradiated regions RE21, RE22, RE23, RE24, RE25... Are formed along the −a2 direction and the + a3 direction alternately.

  Even when the unit pulse light is irradiated in such a manner, a cleavage / cleavage surface is formed between the irradiated regions as each unit pulse light is irradiated, as in the first and second processing patterns. The In the case shown in FIG. 7 (b), the irradiated regions RE21, RE22, RE23, RE24, RE25,... Are formed in this order, so that the cleavage / cleavage surfaces C21, C22, C23, C24,. -Are formed sequentially.

  As a result, in the third processing pattern, a plurality of irradiated areas discretely present in a staggered arrangement with the planned processing line L as an axis, and a cleavage / crack formed between each irradiated area The open surface as a whole becomes a division starting point when the workpiece is divided along the planned machining line L.

  Then, when the division is actually performed along the division starting point, in the range of about 10 μm from the surface of the cross section of the workpiece after the division, the cleavage / dehissing surface is used as in the second machining pattern. Unevenness with a pitch of several μm is formed. In addition, as in the case of the first and second processing patterns, each cleaved / cleavage surface has a submicron pitch due to the occurrence of slippage on a specific crystal plane due to irradiation of unit pulse light. Unevenness occurs.

  Therefore, in the case of processing by such a third processing pattern, in addition to the submicron pitch irregularities formed on the cleavage / cleavage surfaces, in the same way as the processing by the second pattern, several μm by the cleavage / cleavage surfaces. Since unevenness of a certain pitch is formed, even when the processing by the third processing pattern is performed on the light emitting element, the obtained light emitting element is from the viewpoint of improving the light extraction efficiency as described above. It becomes more suitable.

  Note that, depending on the type of workpiece, in order to cause cleavage / dehiscence more reliably, both of the irradiated region RE21 and irradiated region RE22 in FIG. The midpoint, the midpoint of the irradiated region RE22 and the irradiated region RE23, the midpoint of the irradiated region RE23 and the irradiated region RE24, the midpoint of the irradiated region RE24 and the irradiated region RE25,. A region may be formed.

  By the way, the arrangement position of the irradiated region in the third processing pattern is partially along the easy cleavage / cleavage direction. The same applies to the case where the irradiated region is also formed at the midpoint position on the planned processing line L as described above. That is, it can also be said that the third processing pattern is common to the first processing pattern in that at least two irradiated areas are formed adjacent to each other in the cleavage / cleavage easy direction of the workpiece. Accordingly, from a different perspective, the third processing pattern can be regarded as a processing performed by the first processing pattern while periodically changing the laser beam scanning direction.

  In the case of the first and second processing patterns, since the irradiated region is positioned on a straight line, the laser light emission source is moved along the planned processing line to reach a predetermined formation target position. What is necessary is just to form a to-be-irradiated area | region by irradiating unit pulse light every time, and the formation aspect which concerns is the most efficient. However, in the case of the third processing pattern, the irradiated area is formed not in a straight line but in a zigzag pattern (in a zigzag pattern), so that not only a method of actually moving the laser beam emission source in a zigzag pattern (in a zigzag pattern). The irradiated region can be formed by various methods. In the present embodiment, the movement of the emission source means a relative movement between the workpiece and the emission source, and not only when the workpiece is fixed and the emission source moves, but also the emission source. Is fixed and the workpiece moves (actually, the stage on which the workpiece is placed moves).

  For example, as described above, by periodically moving the emission direction of the laser beam in a plane perpendicular to the planned processing line while relatively moving the output source and the stage at a constant speed parallel to the planned processing line. It is also possible to form the irradiated region in a manner that satisfies a staggered arrangement relationship.

  Alternatively, the above-described staggered arrangement relationship is achieved by periodically changing the irradiation timing of the unit pulse light from each emission source while relatively moving the plurality of emission sources at a constant speed in parallel. It is also possible to form an irradiated region with

  FIG. 8 is a diagram showing the relationship between the planned processing line and the planned formation position of the irradiated region in these two cases. In any case, as shown in FIG. 8, the formation planned positions P21, P22, P23, P24, P25... Of the irradiated regions RE21, RE22, RE23, RE24, RE25. .. Are alternately set on the parallel straight lines Lα and Lβ, and the formation of irradiated regions at the planned formation positions P21, P23, P25... Along the straight line Lα and the planned formation positions P22 and P24 along the straight line Lβ. · · · · · · · · · · · · · · · · · · ·

  When the emission source is moved in a zigzag manner (zigzag), the laser beam is relatively scanned by moving the stage on which the workpiece is placed, even if the emission source of the laser beam is directly moved. In any case, the movement of the emission source or stage is a two-axis simultaneous operation. On the other hand, the operation of moving only the emission source or the stage in parallel with the planned processing line is a uniaxial operation. Therefore, it can be said that the latter is more suitable for realizing high-speed movement of the emission source, that is, improvement of processing efficiency.

  As shown in each of the above processing patterns, the cleavage / cleavage processing performed in the present embodiment causes discrete irradiation of unit pulse light to cause continuous cleavage / cleavage mainly in the workpiece. This is a processing mode used as a means for imparting impact and stress. Deformation and scattering of the workpiece in the irradiated region are only locally generated as incidental. The cleavage / cleavage processing of the present embodiment having such characteristics performs processing by causing alteration / melting / evaporation removal continuously or intermittently while overlapping irradiation regions of unit pulse light. The mechanism is essentially different from the conventional processing method.

  Further, since it is sufficient that a strong impact or stress is instantaneously applied to each irradiated region, it is possible to irradiate while scanning with laser light at a high speed. Specifically, extremely high-speed scanning, that is, high-speed machining at a maximum of 1000 mm / sec can be realized. Considering that the processing speed in the conventional processing method is about 200 mm / sec at most, the difference is remarkable. Naturally, it can be said that the processing method realized in the present embodiment improves the productivity at each stage as compared with the conventional processing method.

  In the cleavage / cleavage processing in the present embodiment, the crystal orientation of the workpiece (the orientation in the cleavage / easy cleavage direction) and the planned processing line are in a predetermined relationship as in each of the above-described processing patterns. However, the object of application is not limited to these. In principle, the present invention can also be applied to a case where the two are in an arbitrary relationship and the workpiece is a polycrystalline body. In these cases, the direction in which cleavage / cleavage occurs with respect to the planned processing line is not always constant, and irregular irregularities may occur at the division starting point. However, the laser light including the interval between the irradiated areas and the pulse width may be used. By appropriately setting the irradiation conditions, it is possible to perform processing without any practical problems in which the unevenness remains within the allowable range of processing errors.

<Overview of laser processing equipment>
Next, a laser processing apparatus capable of realizing the above-described various processing patterns will be described.

  FIG. 9 is a schematic diagram schematically showing the configuration of the laser processing apparatus 50 according to the embodiment of the present invention. The laser processing device 50 includes a laser beam irradiation unit 50A, an observation unit 50B, a transparent member such as quartz, a stage 7 on which the workpiece 10 is placed, and various laser processing devices 50. The controller 1 mainly controls operations (observation operation, alignment operation, processing operation, etc.). The laser light irradiation unit 50A includes a laser light source SL and an optical path setting means 5, and is a part that irradiates the workpiece 10 placed on the stage 7 with laser light, and corresponds to the laser light emission source described above. To do. The observation unit 50B has a surface observation for directly observing the workpiece 10 from a side irradiated with laser light (referred to as a front surface) and a side placed on the stage 7 (referred to as a back surface). This is a part for performing back surface observation through the stage 7.

  The stage 7 is movable in the horizontal direction between the laser beam irradiation unit 50A and the observation unit 50B by the moving mechanism 7m. The moving mechanism 7m moves the stage 7 in a predetermined XY 2-axis direction within a horizontal plane by the action of a driving unit (not shown). Thereby, the movement of the laser beam irradiation position in the laser beam irradiation unit 50A, the movement of the observation position in the observation unit 50B, the movement of the stage 7 between the laser beam irradiation unit 50A and the observation unit 50B, and the like are realized. It becomes. As for the moving mechanism 7m, a rotation (θ rotation) operation in a horizontal plane around a predetermined rotation axis can be performed independently of horizontal driving.

  In the laser processing apparatus 50, the front surface observation and the back surface observation can be switched appropriately. Thereby, the optimal observation according to the material and state of the workpiece 10 can be performed flexibly and promptly.

  The stage 7 is formed of a transparent member such as quartz, and a suction pipe (not shown) serving as an intake passage for adsorbing and fixing the workpiece 10 is provided therein. The suction pipe is provided, for example, by drilling a predetermined position of the stage 7 by machining.

  With the workpiece 10 placed on the stage 7, suction is performed on the suction pipe by the suction means 11 such as a suction pump, for example, and the suction provided at the stage 7 mounting surface side tip of the suction pipe. The workpiece 10 (and the transparent sheet 4) is fixed to the stage 7 by applying a negative pressure to the holes. In addition, in FIG. 9, although the workpiece 10 which is a process target has illustrated the case where it is affixed on the transparent sheet 4, sticking of the transparent sheet 4 is not essential.

<Illumination system and observation system>
The observation unit 50B irradiates the workpiece 10 placed on the stage 7 with the epi-illumination light L1 from the epi-illumination light source S1 from above the stage 7 and the oblique light-transmitting illumination light L2 from the oblique illumination light source S2. The surface observation by the surface observation means 6 from above the stage 7 and the back surface observation by the back surface observation means 16 from below the stage 7 can be performed.

  Specifically, the epi-illumination light L1 emitted from the epi-illumination light source S1 is reflected by the half mirror 9 provided in a lens barrel (not shown) and is irradiated onto the workpiece 10. . The observation unit 50B includes surface observation means 6 including a CCD camera 6a provided above the half mirror 9 (above the lens barrel) and a monitor 6b connected to the CCD camera 6a. The bright field image of the workpiece 10 can be observed in real time with the light L1 irradiated.

  In the observation unit 50B, a CCD camera 16a provided below the stage 7, more preferably below a half mirror 19 described later (below the lens barrel), and a monitor 16b connected to the CCD camera 16a, The back surface observation means 16 containing is provided. The monitor 16b and the monitor 6b provided in the surface observation means 6 may be common.

  Further, the coaxial illumination light L3 emitted from the coaxial illumination light source S3 provided below the stage 7 is reflected by the half mirror 19 provided in a lens barrel (not shown) and collected by the condenser lens 18. In addition, the workpiece 10 may be irradiated via the stage 7. More preferably, an oblique illumination light source S4 may be provided below the stage 7 so that the oblique illumination light L4 can be applied to the workpiece 10 via the stage 7. These coaxial illumination light source S3 and oblique illumination light source S4 are, for example, when there is an opaque metal layer on the surface side of the workpiece 10 and it is difficult to observe from the surface side due to reflection from the metal layer. It can be suitably used when observing the workpiece 10 from the back side.

<Laser light source>
As the laser light source SL, one having a wavelength of 500 nm to 1600 nm is used. Further, in order to realize the processing with the processing pattern described above, the pulse width of the laser beam LB needs to be about 1 psec to 50 psec. The repetition frequency R is preferably about 10 kHz to 200 kHz, and the laser beam irradiation energy (pulse energy) is preferably about 0.1 μJ to 50 μJ.

  The polarization state of the laser beam LB emitted from the laser light source SL may be circularly polarized light or linearly polarized light. However, in the case of linearly polarized light, for example, the angle between the two is within ± 1 ° so that the polarization direction is substantially parallel to the scanning direction from the viewpoint of the bending of the processed cross section in the crystalline work material and the energy absorption rate. It is preferable that it is made to exist. When the emitted light is linearly polarized light, the laser processing apparatus 50 preferably includes an attenuator (not shown). The attenuator is disposed at an appropriate position on the optical path of the laser beam LB and plays a role of adjusting the intensity of the emitted laser beam LB.

<Optical path setting means>
The optical path setting means 5 is a part for setting an optical path when the workpiece 10 is irradiated with laser light. According to the optical path set by the optical path setting means 5, the laser beam is irradiated to a predetermined irradiation position of the workpiece (scheduled formation position of the irradiated area).

  The optical path setting means 5 not only allows the workpiece 10 to be irradiated with the laser light LB emitted from the laser light source SL during the processing, but also from the laser light source SL. A plurality of optical paths of the laser light LB when the emitted laser light LB is irradiated onto the workpiece 10 are actually or virtually set, and each unit pulse light of the laser light LB is applied to the workpiece. The optical path when irradiating the optical path can be sequentially switched among the set optical paths. In the latter case, a state where simultaneous scanning is performed at a plurality of locations on the upper surface of the workpiece 10 or a state virtually regarded as such is realized. In other words, it can be said that the optical path of the laser beam LB is multiplied.

  Although FIG. 9 illustrates the case where scanning is performed at three locations with the three laser beams LB0, LB1, and LB2, the mode of multiplexing the optical path by the optical path setting unit 5 is not necessarily limited to this. . A specific configuration example of the optical path setting unit 5 will be described later.

<Controller>
The controller 1 controls the operation of each of the above-described units, and implements a control unit 2 that realizes processing of the workpiece 10 in various modes to be described later, a program 3p that controls the operation of the laser processing apparatus 50, and processing processing. It further includes a storage unit 3 for storing various data referred to at the time.

  The control unit 2 is realized by a general-purpose computer such as a personal computer or a microcomputer, for example, and various components can be obtained by reading and executing the program 3p stored in the storage unit 3 into the computer. Is realized as a functional component of the control unit 2.

  Specifically, the control unit 2 includes a drive control unit 21 that controls operations of various driving parts related to processing such as driving of the stage 7 by the moving mechanism 7m and focusing operation of the condenser lens 18, CCD, An imaging control unit 22 that controls imaging by the cameras 6 a and 16 a, an irradiation control unit 23 that controls the irradiation mode of the laser light LB from the laser light source SL and the optical path setting mode in the optical path setting unit 5, and the stage 7 by the suction unit 11 A suction control unit 24 for controlling the suction and fixing operation of the workpiece 10 on the workpiece, and processing for executing processing to the processing target position according to the given processing position data D1 (described later) and processing mode setting data D2 (described later). The processing unit 25 is mainly provided.

  The storage unit 3 is realized by a storage medium such as a ROM, a RAM, and a hard disk. The storage unit 3 may be implemented by a computer component that implements the control unit 2, or may be provided separately from the computer, such as a hard disk.

  In the storage unit 3, machining position data D1 describing the position of the planned machining line set for the workpiece 10 is given from the outside and stored. Further, the storage unit 3 describes conditions for individual parameters of laser light, optical path setting conditions in the optical path setting means 5, driving conditions for the stage 7 (or their settable ranges), and the like for each processing mode. The machining mode setting data D2 is stored in advance.

  Various input instructions given by the operator to the laser processing apparatus 50 are preferably performed using a GUI realized in the controller 1. For example, a processing menu is provided on the GUI by the operation of the processing unit 25. Based on the processing menu, the operator selects a processing mode, which will be described later, and inputs processing conditions.

<Alignment operation>
In the laser processing apparatus 50, prior to the processing, the observation unit 50B can perform an alignment operation for finely adjusting the arrangement position of the workpiece 10. The alignment operation is a process performed to make the XY coordinate axes defined on the workpiece 10 coincide with the coordinate axes of the stage 7. Such alignment processing is performed when the processing with the above-described processing pattern is performed so that the crystal orientation of the workpiece, the planned processing line, and the scanning direction of the laser light satisfy a predetermined relationship required in each processing pattern. Is important.

  The alignment operation can be performed by applying a known technique, and may be performed in an appropriate manner according to the processing pattern. For example, in the case where a repeated pattern is formed on the surface of the workpiece 10 such as when a large number of device chips manufactured using one mother substrate are cut out, a method such as pattern matching is used. Thus, an appropriate alignment operation is realized. In this case, roughly speaking, the CCD camera 6a or 16a acquires captured images of a plurality of alignment marks formed on the workpiece 10, and based on the relative relationship between the captured positions of these captured images. The processing unit 25 specifies the alignment amount, and the drive control unit 21 moves the stage 7 by the moving mechanism 7m according to the alignment amount, thereby realizing alignment.

  By performing such an alignment operation, the machining position in the machining process is accurately specified. Note that after the alignment operation is completed, the stage 7 on which the workpiece 10 is placed moves to the laser beam irradiation unit 50A, and subsequently a processing process is performed by irradiating the laser beam LB. The movement of the stage 7 from the observation unit 50B to the laser beam irradiation unit 50A is guaranteed so that the planned processing position assumed during the alignment operation does not deviate from the actual processing position.

<Outline of processing>
Next, the processing in the laser processing apparatus 50 according to the present embodiment will be described. In the laser processing apparatus 50, the optical path setting means 5 is combined by irradiating the laser beam LB emitted from the laser light source SL and passing through the optical path setting means 5 and the movement of the stage 7 on which the workpiece 10 is placed and fixed. The workpiece 10 can be processed while the laser beam having passed through is scanned relative to the workpiece 10.

  The laser processing apparatus 50 is characterized in that a basic mode and a multi mode can be alternatively selected as a processing mode (processing mode) by scanning (relatively) the laser beam LB. Is. These processing modes are provided in accordance with the optical path setting mode in the optical path setting means 5 described above.

  The basic mode is a mode in which the optical path setting means 5 fixedly determines the optical path of the laser light LB emitted from the laser light source SL. In the basic mode, the laser beam LB always passes through one optical path, and the stage 7 on which the workpiece 10 is placed is moved at a predetermined speed so that the laser beam scans the workpiece 10 in one direction. Is realized.

  The basic mode is preferably used when performing processing with the above-described first and second processing patterns. That is, for the workpiece 10 in which the planned processing line L is set parallel to the cleavage / easy cleavage direction, the workpiece 10 is aligned so that the cleavage / easy cleavage direction coincides with the moving direction of the stage 7. In addition, the first processing pattern can be processed by processing in the basic mode. On the other hand, with respect to the workpiece 10 in which the planned processing line L is set to be perpendicular to the cleavage / easy cleavage direction, the workpiece 10 is aligned so that the cleavage / easy cleavage direction and the moving direction of the stage 7 are orthogonal to each other. In addition, the second processing pattern can be processed by performing processing in the basic mode.

  Further, in principle, it can also be applied to machining with the third machining pattern by appropriately changing the moving direction of the stage 7.

  On the other hand, the multi mode is a mode in which a plurality of optical paths are set by actually or virtually multiplexing the optical path of the laser beam LB. For example, as shown in FIG. 8, a plurality of laser beams are scanned substantially or virtually along the straight lines Lα and Lβ parallel to the planned processing line L or further along the planned processing line L itself. As a result, this is a mode that realizes the same processing as when the laser beam is scanned in a manner that repeatedly intersects the planned processing line L. Note that virtually scanning a plurality of laser beams is actually irradiating a laser beam with one optical path as in the basic mode, but by changing the optical path with time, It means that the same scanning mode as that in the case of irradiating with laser light is realized.

  The multi mode is suitably used when processing with the third processing pattern. That is, as in the case of the second machining pattern, for the workpiece 10 in which the planned machining line L is set to be perpendicular to the cleavage / easy cleavage direction, the cleavage / easy cleavage direction and the moving direction of the stage 7 are the same. After the workpiece 10 is aligned so as to be orthogonal to each other, the third processing pattern can be processed by performing processing in a multimode.

  It is preferable that the processing mode can be selected according to a processing menu provided to the operator in the controller 1 by the operation of the processing unit 25, for example. The processing unit 25 acquires the processing position data D1 and the conditions corresponding to the selected processing pattern from the processing mode setting data D2, and the drive control unit 21 or the like so that the operation according to the conditions is executed. The operation of each corresponding unit is controlled through the irradiation control unit 23 and others.

  For example, adjustment of the wavelength and output of the laser light LB emitted from the laser light source SL, the pulse repetition frequency, the pulse width, and the like are realized by the irradiation control unit 23 of the controller 1. When a predetermined setting signal according to the processing mode setting data D2 is issued from the processing unit 25 to the irradiation control unit 23, the irradiation control unit 23 sets the irradiation condition of the laser beam LB according to the setting signal.

  In particular, when processing is performed in the multi-mode, the irradiation control unit 23 synchronizes the optical path switching timing by the optical path setting means 5 with the emission timing of the unit pulse light from the laser light source SL. Thereby, unit pulse light is irradiated with respect to the planned formation position of each irradiation region in the optical path corresponding to the planned formation position among the plurality of optical paths set by the optical path setting means.

  In the laser processing apparatus 50, it is possible to irradiate the laser beam LB in the defocus state in which the in-focus position is intentionally shifted from the surface of the workpiece 10 as necessary during the processing. It has become. This is realized, for example, by adjusting the relative distance between the stage 7 and the optical path setting means 5.

<Configuration example and operation of optical path setting means>
Next, a specific configuration of the optical path setting unit 5 and an example of the operation will be described mainly for the operation in the multimode.

  In the following description, the processing is performed while moving the stage 7 on which the workpiece 10 is placed along the moving direction D that coincides with the extending direction of the processing line L. To do.

  Further, in the multi-mode operation, the laser beam LB0 is irradiated when the irradiated region RE is formed on the planned processing line L, and the irradiated region on the straight line Lα parallel to the planned processing line L. The laser beam LB1 is irradiated when the RE is formed. The laser beam LB1 is also irradiated when the irradiated region RE is formed on the straight line Lβ parallel to the processing line L and symmetrical with respect to the processing line L. Is the laser beam LB2.

  Further, the processing of the third processing pattern in the multi-mode is realized by positioning a plurality of irradiated regions formed sequentially or simultaneously along the easy cleavage / cleavage direction.

  FIG. 10 is a diagram schematically showing the configuration of the optical path setting means 5. The optical path setting means 5 includes a plurality of half mirrors 53, a mirror 54, an optical path selection mechanism 55, and a lens system 52.

  The half mirror 53 and the mirror 54 divide the optical path of the laser beam LB emitted from the laser light source SL in an in-plane direction perpendicular to the moving direction D of the stage 7, and a plurality of optical paths (laser beams LB0, LB1, and LB2). Provided to form an optical path). The number of half mirrors 53 is determined according to the number of optical paths. In FIG. 10, two half mirrors 53 are provided to obtain three optical paths. By providing the half mirror 53 and the mirror 54, the stage 7 is moved while emitting the laser beam LB, thereby realizing a state in which a plurality of laser beams scan the workpiece 10.

  The optical path selection mechanism 55 is provided to control the emission timing of the laser light to the workpiece 10 in a plurality of optical paths. More specifically, the optical path selection mechanism 55 includes an optical switch SW in the middle of the optical path of each laser beam branched by the half mirror 53 and the mirror 54. The optical switch SW is composed of, for example, an AOM (acousto-optic modulator), an EOM (electro-optic device), or the like. It has a function to make it (non-passing state). Thereby, in the optical path selection mechanism 55, only the laser beam that passes through the optical switch SW in the ON state is irradiated to the workpiece 10.

  In the multi-mode operation of the laser processing apparatus 50 including the optical path setting means 5 having such a configuration, the irradiation control unit 23 performs the laser light LB0 according to the emission timing of the unit pulse light of the laser light LB according to the repetition frequency R. This is realized by controlling the ON / OFF operation of each optical switch SW so that the optical switches SW on the optical paths of LB1, LB2 are sequentially and periodically turned on. By such control, the laser beam LB0, LB1, LB2 passes through the optical path selection mechanism 55 and is irradiated on the workpiece 10 only when the timings at which the laser beams LB0, LB1, LB2 form the irradiated region are reached. It will be.

  That is, a plurality of optical paths of laser light irradiated to the workpiece 10 are actually provided, and by scanning the plurality of laser lights simultaneously in parallel while changing the irradiation timing of each unit pulse light, Multi-mode operation is performed.

  Note that the operation in the basic mode is possible, for example, by moving only the optical switch SW on any one of the optical paths of the laser beams LB0, LB1, and LB2 to emit the laser beam LB and moving the stage 7. It is.

DESCRIPTION OF SYMBOLS 1 Controller 2 Control part 3 Memory | storage part 4 Transparent sheet 5 Optical path setting means 7 Stage 7m Movement mechanism 10 Workpiece 50 Laser processing apparatus 53 Half mirror 54 Mirror 55 Optical path selection mechanism C1-C3, C11a, C11b, C21-C24 Cleaving / Cleaved surface D Direction of movement (of stage 7) L Planned line LB, LB0, LB1, LB2 Laser light RE, RE1-RE4, RE11-RE15, RE21-RE25 Irradiated area SL Laser light source SW Optical switch

Claims (3)

A processing method for forming a division starting point on a workpiece provided with a light emitting element structure on a substrate made of an optically transparent material ,
The pulse laser beam is formed so that the irradiated region for each unit pulse beam of the pulse laser beam is discretely formed in a direction equivalent to two different cleavage or cleavage easy directions of the workpiece. By irradiating the surface of the workpiece , thereby causing the workpiece to be cleaved or cleaved sequentially between the irradiated regions, a starting point for division is formed in the workpiece. ,
A processing method of a workpiece characterized by the above. The processing method according to claim 1,
The pulse laser beam is an ultrashort pulse beam having a pulse width of the order of psec.
A processing method of a workpiece characterized by the above. A method of dividing a workpiece,
Dividing the workpiece on which the division start point is formed by the method according to claim 1 or 2 along the division start point,
A workpiece dividing method characterized by the above.