JP2012164974A - Laser processing device and laser processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a stable modified layer inside a wafer even when a laser beam is radiated over a film stuck to a back surface of the wafer during laser processing of the wafer.SOLUTION: A transparent expanding tape 15 is stuck to a back surface of a wafer 13 facing a front surface of the wafer 13 where a metal film is formed, and the wafer 13 is conveyed to a prescribed position of a liquid tank 12 with the front surface down. Thereafter, the liquid tank 12 is filled with liquid 11 and the wafer 13 is supported on a liquid level of the liquid 11. Further, a laser radiation part including a laser head 40 and a condenser lens 24 is driven in directions of X, Y, Z and θ by the control of a control part 50, the wafer 13 is irradiated with a laser beam P over the expanding tape 15, and the inside or front surface of the wafer 13 is modified. After the inside or front surface of the wafer 13 is modified, the liquid 11 is discharged from the liquid tank 12, division and separation are performed in the area of the wafer 13 where the modified layer is formed, and a chip is generated.

Description

  The present invention relates to a laser processing apparatus and a laser processing method for processing a workpiece such as a semiconductor wafer using a laser beam, and in particular, irradiates a laser beam from the back side of the workpiece to a division line of the workpiece. The present invention relates to a laser processing apparatus that forms a modified region and generates a chip, and a laser processing method.

  2. Description of the Related Art In recent years, a technique is widely known in which a laser beam is irradiated to form a modified layer in a semiconductor wafer (hereinafter referred to as a wafer), and the wafer is broken from the modified layer to generate a chip. For example, in Patent Document 1, a chip is generated by irradiating the surface of a wafer with laser light to form a modified layer in the wafer, and cleaving the wafer along the formed modified layer and cutting it. Techniques to do this are disclosed.

  On the other hand, recently, there are many devices in which the surface of a wafer is covered with a metal film, in particular, devices in which a metal film is formed on a planned cutting line of the wafer. In the case of a device having such a configuration, as shown in Patent Document 1, even if an attempt is made to irradiate a laser beam from the surface of the wafer to form a modified layer inside the wafer, the laser is formed by the metal film on the surface. Since the light is reflected, there is a problem that the laser beam does not reach the inside of the wafer. In such a case, the laser beam cannot be irradiated from the front surface of the wafer, so the laser beam must be irradiated from the back side of the wafer. However, since an expand tape for expanding (elongating) the wafer is usually attached to the back side of the wafer in the subsequent process, it is necessary to irradiate the wafer with laser light through the expand tape. .

  Therefore, for example, Patent Document 2 discloses a method in which a laser is irradiated onto a wafer through an expanded tape to form a melt processing region as a starting point of cutting inside the wafer (substrate). In this technique, the wafer with the expanded tape is placed on the stage with the back side of the wafer on the upper side and the surface of the wafer on the lower side. If a small amount of solid material comes into contact with the surface of the wafer, there is a risk of damaging an element having a fragile structure on the surface of the wafer. Therefore, for a wafer having such a structure, it is not possible to adopt a method of placing the wafer on the stage with the front side of the wafer facing back.

  Further, when the wafer is irradiated with laser light, the wafer itself is partially melted by the modification with the laser power, and therefore the wafer tends to be gradually heated by the laser power. In particular, when irradiating a wafer with a laser beam through an expanded film (through an expanded tape), the laser beam is absorbed by the expanded film, although it depends on the transmittance of the expanded film. The portion of the expanded film irradiated with may also be softened by heating.

  Furthermore, since energy loss occurs due to the wafer itself being irradiated through the expanded film, it is necessary to irradiate a relatively strong laser beam in order to form a reliable modified layer region in the wafer. . However, since the heat generated locally by such intense laser light irradiation affects the device on the wafer surface, dopants (impurities) implanted near the surface of the device are further diffused. It becomes a factor which degrades the performance of the. Therefore, it is necessary to quickly dissipate heat so that the heat formed in the modified layer of the wafer does not transfer to the surface of the wafer.

However, with respect to such locally generated heat, even if the atmosphere of the wafer is cooled, the local heat transmitted from the modified layer to the surface of the wafer cannot be efficiently discharged. In addition, when a minute and fragile element is formed on the wafer surface, the wafer surface cannot be supported by a stage, but even if the wafer surface is supported by a freezing chuck or the like, The chuck and the chuck are not in contact with each other in a surface state, but the substantial contact state is a point contact state due to a collection of point groups. Therefore, it is extremely difficult to efficiently dissipate heat transferred to the wafer surface by heat transfer and maintain the wafer surface at a constant temperature even during laser processing.

  Furthermore, when a modified layer is formed inside the wafer by laser processing, the modified layer is a portion that is far from the back side of the wafer to which the expanded film (expanded tape) is attached and is close to the front side of the wafer. It is necessary to irradiate the laser beam so that the light is condensed. In this case, the modified layer is formed inside the wafer, but there is also laser light that passes through the wafer with a part of the irradiation energy passing through the wafer. In such a case, for example, if a microscopic and fragile element is formed on the surface of the wafer, the surface of the wafer cannot be supported, but even if the surface of the wafer is supported by some chuck, The laser beam is also partially irradiated to the chuck portion. Therefore, the laser light may be reflected / scattered on the surface of the support (chuck) and irradiate other portions of the wafer surface. In such a case, laser burn occurs in a portion different from the cutting line of the wafer, and there is a risk that other portions of the wafer surface will be extremely deteriorated. The phenomenon in which the laser beam is reflected in this manner and another portion of the wafer is irradiated with the reflected light to be modified is referred to as a proximity effect. However, reduction of the deterioration of the wafer surface due to the proximity effect must also be considered.

  In addition, the adverse effect caused by the reflection of the laser beam due to the proximity effect is not only the process of irradiating the laser beam from the back side of the wafer through the film and forming a modified layer near the surface of the wafer, but also the wafer. Even in the conventional process of irradiating laser light from the front surface of the wafer, the laser light is scattered between the stage that supports the wafer and the back surface of the wafer, and laser burn occurs in a part of the wafer. As a result, chips (debris) are formed on the back surface of the wafer, and fine debris of the wafer may remain as dust on the wafer support (stage). Even if the support stage (stage) that supports the wafer is floated by compressed air or the like, it is difficult to support the wafer in a uniform plane state considering the deflection of the wafer itself. It is difficult to perform stable laser processing.

  As a related technique, there is disclosed a technique for generating a chip by holding a work without touching a device formation region and irradiating a laser beam along a planned division line from the back side of the work (for example, Patent Documents 3 and 4). According to this technology, a wafer is scheduled to be cut by attaching a pressure-sensitive adhesive tape to the back surface of the wafer with the back surface of the wafer on which the device is formed and irradiating laser light from the front surface side of the pressure-sensitive adhesive tape. By modifying the chip, chips can be easily generated from the wafer.

JP 2002-192370 A JP 2006-148175 A JP 2010-29927 A JP 2010-29930 A

  As described above, when the laser beam is irradiated from the surface of the wafer as in the technique of Patent Document 1, in a device in which a metal film is formed on the surface of the wafer, the laser beam is appropriately irradiated and the laser beam is irradiated. A modified layer cannot be formed inside the wafer. Moreover, when irradiating a laser beam through the said film stuck on the back surface of a wafer like the technique of patent document 2, the energy loss of a laser beam, the local heating of the said wafer, the heating softening of this film, Due to re-diffusion of impurities due to heating, deflection of the wafer, proximity effect, and the like, the modified layer cannot be formed by performing stable laser processing on the wafer. In the techniques of Patent Documents 3 and 4, since laser light is irradiated from the back surface of the wafer through the film, a stable modified layer can be formed on the wafer as in the technique of Patent Document 2. Can not.

  Therefore, at the time of laser processing of the wafer (substrate), the wafer level (horizontal state) is accurately maintained, the surface temperature of the wafer is kept constant, and the proximity effect is eliminated. Even if the laser beam is irradiated through the film affixed to the back surface of the wafer, there arises a technical problem to be solved in order to be able to form a stable modified layer inside or on the surface of the wafer. Therefore, an object of the present invention is to solve this problem.

  The present invention has been proposed to achieve the above object, and the invention according to claim 1 is a laser processing apparatus for modifying a substrate to divide the substrate into chips by laser light, wherein the liquid processing apparatus The substrate supported on the liquid surface, a transparent expanded film attached to the back surface of the substrate, and the substrate is irradiated with the laser light through the expanded film to modify the inside or the surface of the substrate. There is provided a laser processing apparatus comprising a laser beam irradiation means for performing.

  According to this configuration, an expanded film (expanded tape) is attached to the back side of the substrate (wafer), the back side of the substrate is faced up, and the front side of the substrate is faced down and supported by the liquid level. Yes. And a laser beam is irradiated to a board | substrate through an expanded film by a laser beam irradiation means, and the modified layer is formed in the inside or surface of this board | substrate. As a result, the substrate can be irradiated with laser light while maintaining the substrate in a horizontal state, so that a modified layer can be formed on the substrate with high accuracy to produce a chip.

  Further, the laser beam is focused on the inside or the surface of the substrate to modify the substrate. However, when the surface of the substrate is in contact with the liquid, the difference in the refractive index is smaller than when the substrate is in contact with air. . For example, a silicon oxide film is formed on the surface of a silicon substrate, and the refractive index of the silicon oxide film is about 1.45.

  On the other hand, since the refractive index of air is 1.0, when the substrate is in contact with normal air, scattering occurs due to the difference in refractive index between the substrate and air and the roughness shape of the substrate surface. Energy is lost. As a result, there is a possibility that heat is generated in the vicinity of the surface and the quality and performance of the element are deteriorated.

  In the present invention, if the liquid in contact with the substrate surface is, for example, water, the refractive index is about 1.3, so the difference in refractive index between the liquid and the substrate surface is greatly reduced. Further, the roughness shape of the surface also has an effect of making it less susceptible to scattering due to the roughness shape of the substrate surface because the liquid wraps around the shape and embeds the shape.

  As a result, if the substrate is supported on the surface of the liquid, the difference in refractive index is reduced, the influence of the roughness shape of the substrate surface is eliminated, and the scattering of laser light is greatly reduced. Greatly reduces the energy loss of the laser light generated in As a result, it is possible to protect the element surface by suppressing heat generation on the substrate surface, efficiently guide excess laser light into the liquid, and effectively attenuate the energy in the liquid.

  The invention described in claim 2 is a laser processing apparatus for performing substrate modification for dividing a substrate into chips by laser light, wherein a liquid tank filled with a liquid, and a liquid liquid filled in the liquid tank A substrate supported by a surface; a transparent expanded film affixed to the back surface of the substrate; and laser light irradiation means for modifying the interior or surface of the substrate by irradiating the expanded film with the laser light; A laser processing apparatus is provided.

  According to this configuration, the liquid tank is filled with a liquid, and is supported by the liquid surface of the liquid with the back side of the substrate having the expanded film attached facing upward and the surface side of the substrate facing downward. And a laser beam is irradiated to a board | substrate through an expanded film by a laser beam irradiation means, and the modified layer is formed in the inside or surface of this board | substrate. As a result, the substrate can be supported by the liquid level without destroying the fragile structure on the surface of the substrate, and even a large substrate that is largely bent by its own weight is filled in the liquid tank. The substrate can be horizontally supported by the liquid level of the liquid. Accordingly, since the laser beam can be appropriately irradiated to the substrate in the horizontal state, it is possible to form a chip by forming the modified layer with high accuracy on the substrate.

  In the invention of claim 3, the laser beam irradiation means has the substrate back surface facing the substrate surface on which the metal film is formed on the upper side, and the surface of the expanded film attached to the back surface of the substrate is the surface of the expanded film. 3. A laser processing apparatus according to claim 1, wherein the laser beam is irradiated with a laser beam.

  According to this configuration, the substrate is supported on the liquid surface with the surface side of the substrate on which the metal film is formed facing downward. And the laser beam is irradiated to the board | substrate through an expanded film by the laser beam irradiation means by making the back surface side of the board | substrate with which the expanded film was stuck up. As a result, the substrate can be supported by the liquid level without destroying the fragile structure on the surface of the substrate, and even the substrate that is large enough to bend due to its own weight is filled into the liquid tank. The substrate can be horizontally supported by the liquid.

  In addition, excessive heating near the surface of the substrate due to laser light irradiation causes the entire surface of the substrate to be immersed in the liquid uniformly when the substrate contacts the liquid surface of the liquid filled in the liquid tank. Can be efficiently cooled to keep the surface temperature of the substrate constant. Furthermore, since the heat capacity of the liquid is large, the temperature of the liquid that is cooling the substrate does not rapidly increase, and as a result, a stable temperature environment can be maintained for the substrate.

  According to a fourth aspect of the present invention, there is provided the laser processing apparatus according to the second or third aspect, wherein the liquid tank has a property of transmitting and absorbing the laser light.

  According to this configuration, since the liquid tank transmits and absorbs the laser beam, the proximity effect due to the transmission and irregular reflection of the laser beam can be prevented.

  A fifth aspect of the present invention provides the laser processing apparatus according to the first, second, third, or fourth aspect, wherein the refractive index of the liquid is substantially equal to the refractive index of the substrate.

  According to this configuration, the difference between the refractive index of the substrate and the refractive index of the liquid interface is made as small as possible by bringing the refractive index of the substrate and the refractive index of the liquid close to each other. The energy loss of laser light is greatly reduced.

  A sixth aspect of the present invention provides the laser processing apparatus according to the first, second, third or fourth aspect, wherein the laser beam irradiation means irradiates the laser beam in a pulsed manner.

  According to this configuration, since the laser beam is irradiated in a pulsed manner, there is no possibility that the liquid generates a large amount of heat due to the irradiation of the laser beam, and the temperature of the liquid can be adjusted to have a stable and uniform temperature distribution as much as possible. .

  The invention according to claim 7 is a laser processing method for performing substrate modification for dividing a substrate into chips by laser light, the first step of supporting the substrate by a liquid level, and the liquid level And a second step of modifying the inside or the surface of the substrate by irradiating the substrate supported by the laser beam with a laser beam.

  According to this method, after the substrate is supported by the liquid surface, the substrate is irradiated with laser light to modify the inside or the surface of the substrate. However, the horizontal state of the substrate can be accurately maintained without the substrate being bent by its own weight. Furthermore, the surface temperature of the substrate can be kept constant by effectively discharging the amount of heat accumulated on the surface of the substrate with the irradiation of the laser light to the liquid.

  The invention according to claim 8 is a laser processing method for performing substrate modification for dividing a substrate into chips by laser light, wherein the substrate on which a transparent expanded film is attached is supported by a liquid surface. And a second step of irradiating the substrate supported by the liquid surface through the expanded film with the laser light to modify the inside or the surface of the substrate. A laser processing method is provided.

  According to this method, after supporting the substrate on which the transparent expanded film is adhered on the liquid surface of the liquid, the substrate supported on the liquid surface of the liquid is irradiated with laser light through the expanded film. The inside or surface of the substrate is modified. As a result, even if the surface of the substrate has a minute and fragile structure, the surface of the substrate is supported by the liquid surface, so that laser processing is performed in a stable support state without damaging the surface of the substrate. It can be performed.

  Further, since the expanded film and the substrate are bent by their own weight, it is possible to prevent a phenomenon in which misalignment occurs without taking the level of the laser light irradiation surface.

  The invention according to claim 9 is a laser processing method for performing substrate modification for dividing a substrate into chips by laser light, and is an expanded transparent to the substrate back surface facing the substrate surface on which the metal film is formed. A first step of attaching a film; a second step of conveying the substrate on which the expanded film is attached to a liquid tank; and filling the liquid in the liquid tank and attaching the substrate on which the expanded film is attached. A third step of supporting the liquid level of the liquid, and irradiating the substrate supported by the liquid level with the laser light through the expanded film to modify the inside or the surface of the substrate. And a fourth step of discharging the liquid supporting the substrate from the liquid tank after the modified layer is formed on or inside the substrate, and the liquid. Said liquid from the tank And the modified layer is applied to the substrate on which the expanded film is adhered, and a sixth step of conveying the substrate on which the expanded film is adhered to the outside from the liquid tank. And a seventh step of generating chips separated and separated in the formed region.

  According to this method, after the expanded film is pasted on the back surface of the substrate and the substrate is transported to the liquid tank, the liquid tank is filled with liquid and the back surface of the substrate on which the expanded film is pasted is directed upward. The substrate is supported by a surface. Then, the substrate supported on the liquid surface is irradiated with laser light through an expanded film to modify the inside or the surface of the substrate. Further, after the modified layer is formed on the inside or the surface of the substrate, the liquid is discharged from the liquid tank, and the substrate is transported from the liquid tank to the outside, so that the modified layer is formed in the region of the substrate. Chips are generated separately.

  The invention according to claim 10, by irradiating the laser beam on the surface side of the expanded film attached to the back surface of the substrate, with the back surface of the substrate facing the substrate surface on which the metal film is formed facing upward. The laser processing method according to claim 9, wherein the substrate is modified.

  According to this method, the substrate is supported by the liquid level with the surface side of the substrate on which the metal film is formed facing downward. And the laser beam is irradiated to the board | substrate through an expanded film by the laser beam irradiation means by making the back surface side of the board | substrate with which the expanded film was stuck up. As a result, the substrate can be supported by the liquid level without destroying the fragile structure on the surface of the substrate, and even the substrate that is large enough to bend due to its own weight is filled into the liquid tank. The substrate can be supported horizontally on the surface of the liquid.

  In addition, excessive heating near the surface of the substrate due to laser light irradiation causes the entire surface of the substrate to be immersed in the liquid uniformly when the substrate contacts the liquid surface of the liquid filled in the liquid tank. Can be efficiently cooled to keep the surface temperature of the substrate constant. Furthermore, since the heat capacity of the liquid is large, the temperature of the liquid that is cooling the substrate does not increase rapidly, and a stable temperature environment can be maintained with respect to the substrate.

  The invention according to claim 11 provides the laser processing method according to claim 7, 8, 9 or 10, wherein the refractive index of the liquid is substantially equal to the refractive index of the substrate.

According to this method, by making the refractive index of the substrate and the refractive index of the liquid close to each other, the difference in refractive index between the substrate and the liquid interface is further reduced as much as possible. Energy loss is greatly reduced.
According to a twelfth aspect of the present invention, there is provided the laser processing method according to the seventh, eighth, ninth or tenth aspect, wherein the laser beam is irradiated in a pulse manner.

  According to this method, since the laser beam is irradiated in a pulsed manner, there is no possibility that the liquid generates a large amount of heat due to the laser beam irradiation, and the temperature of the liquid is adjusted to have a stable and uniform temperature distribution as much as possible. Can do.

  In the first aspect of the present invention, since the substrate is supported by the liquid level and the laser beam is irradiated to the substrate through the expanded film, the substrate is maintained in a horizontal state, and the substrate is highly accurate. A modified layer can be formed to produce a chip.

  According to the second aspect of the present invention, since the substrate is supported in a horizontal state by the surface of the liquid filled in the liquid tank, the laser beam can be irradiated without causing the substrate to bend. Therefore, it is possible to form a chip by forming a modified layer on the substrate with high accuracy.

  Since the invention according to claim 3 is supported by the liquid level with the substrate surface on which the metal film is formed facing downward, and the laser beam is irradiated from the back side of the substrate to which the expanded film is attached, In addition to the effects of the invention described in 1 or 2, the substrate can be supported by the liquid level without destroying the fragile structure on the substrate surface, and the substrate is large enough to bend by its own weight. In addition, the substrate can be supported in a horizontal state by the liquid level of the liquid filled in the liquid tank.

  In addition, excessive heating near the surface of the substrate due to laser light irradiation causes the entire surface of the substrate to be immersed in the liquid uniformly when the substrate contacts the liquid surface of the liquid filled in the liquid tank. Can be efficiently cooled to keep the surface temperature of the substrate constant. Furthermore, since the heat capacity of the liquid is large, the temperature of the liquid that is cooling the substrate does not increase rapidly, and a stable temperature environment can be maintained with respect to the substrate.

  In the invention described in claim 4, since the liquid tank transmits and absorbs the laser beam, in addition to the effect of the invention described in claim 2 or 3, it is possible to appropriately prevent the proximity effect due to the transmission or irregular reflection of the laser beam. Can do.

  According to the fifth aspect of the present invention, energy loss due to scattering or the like occurring at the interface of the liquid is greatly reduced. When the laser beam of the portion is removed, the energy of the laser beam is locally used in the vicinity of the interface, so that the substrate surface can be prevented from generating heat locally.

  In the invention described in claim 6, since the temperature of the liquid can be adjusted to be as stable as possible and to have a uniform temperature distribution, in addition to the effect of the invention described in claim 1, 2, 3 or 4, the number of irradiation times Even when there is a possibility that a temperature difference may occur in the substrate due to the heat being gradually accumulated, the deformation of the substrate shape due to the temperature difference can be suppressed.

  In the invention according to claim 7, since the substrate is supported by the liquid level and the substrate is irradiated with the laser beam, even if the substrate is large, the substrate is not bent by its own weight, and the horizontal state is maintained. It can be maintained with high accuracy. Furthermore, the surface temperature of the substrate can be kept constant by effectively discharging the amount of heat accumulated on the surface of the substrate to the liquid as the laser light is irradiated.

  In the invention according to claim 8, since the substrate on which the transparent expanded film is attached is supported by the liquid surface of the liquid and the laser beam is irradiated through the expanded film, the surface of the substrate has a minute and fragile structure. Even if it has, laser processing can be performed in a stable support state without damaging the surface of the substrate. Further, since the expanded film and the substrate are bent by their own weight, it is possible to prevent a phenomenon in which misalignment occurs without taking the level of the laser light irradiation surface.

  Since the invention according to claim 9 can be performed in a flow operation from the modification of the substrate by laser light to the chip processing by performing a series of laser processing steps while floating the substrate on the liquid surface of the liquid tank, Laser processing can be performed in a stable state without damaging the surface of the substrate.

  The invention according to claim 10 is supported over the liquid surface with the surface side of the substrate on which the metal film is formed facing downward, and over the expanded film with the back side of the substrate on which the expanded film is attached facing upward. Since the substrate is irradiated with laser light, in addition to the effect of the invention of claim 9, the substrate can be supported by the liquid level without destroying the fragile structure on the surface of the substrate, and Even if the substrate is large enough to bend due to its own weight, the substrate can be supported in a horizontal state on the surface of the liquid filled in the liquid tank.

  In addition, excessive heating near the surface of the substrate due to laser light irradiation causes the entire surface of the substrate to be immersed in the liquid uniformly when the substrate contacts the liquid surface of the liquid filled in the liquid tank. Can be efficiently cooled to keep the surface temperature of the substrate constant. Furthermore, since the heat capacity of the liquid is large, the temperature of the liquid that is cooling the substrate does not rapidly increase, and a stable temperature environment can be maintained with respect to the substrate.

  Since the invention according to claim 11 can significantly reduce the energy loss of the laser beam due to scattering or the like generated at the liquid interface, in addition to the effect of the invention according to claim 7, 8, 9 or 10, the substrate When a part of the laser beam is released from the surface to the liquid, the energy of the laser beam is locally used in the vicinity of the interface, and the surface can be prevented from generating heat locally.

  In the invention described in claim 12, since the temperature of the liquid can be adjusted so that the temperature distribution is as stable and uniform as possible, in addition to the effect of the invention described in claim 7, 8, 9 or 10, the number of irradiations is repeated. Even when the substrate is gradually heated and a temperature difference may occur in the substrate, the shape of the substrate can be prevented from being deformed by the temperature difference.

The block diagram of the laser processing apparatus applied to this invention. FIG. 2 is a conceptual diagram showing details of the driving means shown in FIG. The top view of the drive means shown in FIG. Process drawing which shows the flow of the laser processing process by the laser processing apparatus of this invention. The process figure which shows the chip-forming process of the wafer by an expand apparatus.

  The present invention maintains the level (horizontal state) of the wafer with high precision during the laser processing of the wafer, makes the surface temperature of the wafer constant, and eliminates the proximity effect. In order to achieve the purpose of forming a stable modified layer inside the wafer even when laser light is irradiated through the expanded film attached to the back side, the substrate is applied to the chip by laser light. A laser processing apparatus for modifying a substrate for dividing, the substrate supported by a liquid surface of the liquid, a transparent expanded film attached to the back surface of the substrate, and the substrate through the expanded film And a laser beam irradiating means for modifying the inside or the surface of the substrate by irradiating the laser beam on the substrate. It was realized. Hereinafter, a preferred embodiment of a laser processing apparatus according to the present invention will be described in detail with reference to FIGS.

  First, the structure of the laser processing apparatus applied to this invention is demonstrated. FIG. 1 is a configuration diagram of a laser processing apparatus applied to the present invention. As shown in FIG. 1, the laser processing apparatus 1 is mainly configured by a wafer mounting unit 10, a laser head 40 including a laser optical unit 20 and an observation optical unit 30, a control unit 50, and the like.

  The wafer mounting unit 10 includes a liquid tank 12 in which the liquid 11 is stored, a wafer 13 with the back side facing up and the front side supported by the liquid level of the liquid 11, the back side of the wafer 13, and the surfaces of the dicing frames 14, 14. And an expanded film (dicing tape) 15 that is integrally attached to each other. In such a configuration, since the wafer 13 is floating on the liquid surface of the liquid 11, if the liquid tank 12 is moved, the liquid 11 undulates and the horizontal state of the wafer 13 becomes unstable. The wafer placement unit 10 is fixed. Therefore, the laser light irradiation unit having an optical system such as the laser head 40 and the condensation lens (condensing lens) 24 is moved.

  In this embodiment, the refractive index of the liquid 11 filled in the liquid tank 12 can be adjusted to be substantially the same as the refractive index of the wafer 13, and the laser beam irradiation means can irradiate the laser beam in a pulsed manner. Can be adopted.

  In another embodiment, the liquid 11 in the liquid tank 12 is made very thin to prevent the liquid 11 from undulating and moving in a horizontal state when the liquid tank 12 is moved. (For example, the thickness of the liquid 11 may be 1 mm or less), and the wafer 13 may be placed on the liquid 11 and sealed around the wafer 13 and the liquid tank 12. If the displacement of the wafer 13 is fixed around the wafer 13, the wafer 13 will not be displaced laterally even if the liquid tank 12 is moved.

  Further, when the liquid 11 is thinned, the liquid 11 itself does not wave much due to the influence of the interface tension acting between the liquid 11 and the solid that is the surface of the liquid tank 12. For example, when the surface of the liquid tank 12 is roughened, the wettability of the liquid 11 with respect to the surface of the liquid tank 12, that is, the interfacial tension increases, and the liquid 11 in the liquid tank 12 sticks to the surface of the liquid tank 12. Even if the liquid tank 12 is moved in such a state, the liquid 11 is moved along with the liquid tank 12 which is a solid, and the liquid level is not greatly touched. Therefore, although depending on the magnitude of the acceleration for moving the liquid tank 12, if the liquid tank 12 is not moved rapidly, the liquid tank 12 itself can be moved while suppressing the undulation of the liquid 11.

  Further, if even a little liquid 11 is present on the wafer 13, the liquid 11 is an incompressible fluid unlike gas, so that the hydrostatic pressure acts uniformly on the entire liquid surface of the liquid 11. Therefore, even if the wafer 13 has a large size, it becomes possible to support the wafer 13 with uniform stress within the surface of the wafer 13.

  In addition, it is desirable that the temperature of the liquid 11 is kept as high as the temperature of the wafer 13 as much as possible, or at most about room temperature. Although the laser beam is irradiated inside the wafer 13, since the laser beam irradiation can be performed in a pulsed manner, there is no fear that the wafer 13 generates a large amount of heat. However, as the number of irradiations increases, the temperature gradually increases. When a temperature difference occurs, the shape of the wafer 13 may be deformed due to the temperature difference. In order to prevent this, it is preferable to adjust the temperature of the liquid 11 so as to obtain a stable and uniform temperature distribution without forming a temperature gradient with respect to the temperature distribution of the liquid surface.

  The dicing frames 14 and 14 are positioned and fixed at predetermined positions on the edge of the liquid tank 12 with high accuracy. Alternatively, the dicing frames 14 and 14 may be fixed without being floated on the liquid 11, although they may be fixed to other portions instead of the edge of the liquid tank 12. As a result, the position of the wafer 13 in the XY directions of the wafer 13 is determined via the dicing films 14 and 14 based on the fixed dicing frames 14 and 14.

  In addition, the wafer 13 may follow and move up and down with some vertical movement of the liquid level. This is because the dicing frames 14 and 14 are fixed and the dicing frames 14 and 14 and the wafer 13 are connected to each other. The film 15 acts as a damper so as to suppress vertical movement and shaking.

  Further, even when the liquid level is slightly different, the expanded film 15 is positioned to follow the minute height difference between the wafer 13 and the fixed dicing frames 14 and 14. The As a result, the XY direction can be stably positioned and the surface of the wafer 13 to be irradiated with the laser can be allowed to stand while following the liquid level with respect to the Z direction which is the vertical direction.

  If the liquid 11 filled in the liquid tank 12 floats up to the dicing frames 14 and 14, the reference surface cannot be taken, and stable laser processing cannot be performed. Therefore, the structures of the fixed dicing frames 14 and 14, the wafer 13 supported by the liquid surface of the liquid 11, and the flexible expanded film 15 that connects the dicing frames 14 and 14 and the wafer 12 are important.

  That is, the laser light irradiation unit of the optical system including the laser head 40, the condensation lens 24, and the like is configured to move precisely in the XYZθ direction according to a control signal from the control unit 50. As a result, the laser beam P irradiated from the condensation lens 24 onto the wafer 13 moves precisely in the XYZθ direction, so that the laser beam P can be scanned along the planned modification line of the wafer 13. In addition, by supporting the wafer 13 with the liquid surface of the liquid 11, it is possible to prevent the wafer 13 from being bent by its own weight. In particular, in the case of a large wafer 13, the effect of preventing deflection due to its own weight becomes even more remarkable.

  Further, a transparent expanding tape 15 for expanding (expanding) the wafer 13 that has been cleaved into chips is attached to the back surface side of the wafer 13. That is, an expanded tape 15 having an adhesive material is attached to one side (back side) of the wafer 13, and the back side is directed upward while being integrated with the dicing frame 14 via the expanded tape 15. The surface side of the wafer 13 is placed in a state where it floats on the liquid surface of the liquid 11 stored in the liquid tank 12. Therefore, the laser beam P irradiated from the condensation lens 24 of the laser beam irradiation unit located on the upper surface of the back surface of the wafer 13 passes through the transparent expanding tape 15 to form a modified layer inside the wafer 13.

  The laser optical unit 20 includes a laser oscillator 21, a collimating lens 22, a half mirror 23, a condensation lens (condensing lens) 24, and driving means 25 that minutely moves the laser light P in parallel with the wafer 13. Has been. Accordingly, the laser beam L (see FIG. 2) oscillated by the laser oscillator 21 is condensed inside the wafer 13 as the laser beam P through the optical system such as the collimating lens 22, the half mirror 23, and the condensation lens 24. At this time, the Z direction position of the condensing point of the laser beam P is adjusted by the Z direction fine movement of the condensation lens 24 by the Z fine movement means 27 (see FIG. 2) described later.

  The conditions of the laser beam P are as follows: the light source is a semiconductor laser pumped Nd: YAG laser which is a solid laser using yttrium, aluminum, garnet, the wavelength is 1064 nm, the laser beam spot cross-sectional area is 3.14 × 10 −8 cm 2, The oscillation form is a Q switch pulse, the repetition frequency is 100 kHz, the pulse width is 30 ns, the output power is 20 μJ / pulse, the laser light quality is TEM00 (single mode), and the polarization characteristic is linearly polarized light. The condition of the condensation lens 24 is that the magnification is 50 times, N.V. representing the resolution, the depth of focus, and the brightness of the image. A. (Numerical Aperture) is 0.55, and the transmittance with respect to the wavelength of the laser beam is 60%.

  In another embodiment, in the liquid tank 12, when the liquid tank 12 is moved, the liquid 11 undulates and the horizontal state becomes unstable. It is also possible to reduce the thickness of the liquid 13 (for example, the thickness of the liquid 11 to 1 mm or less), place the wafer 13 thereon, and seal the periphery of the wafer 13 and the liquid tank 12. If the wafer 13 is fixed around the wafer 13, the wafer 13 will not be displaced laterally even if the liquid tank 12 is moved.

  Further, when the liquid 11 is thinned, the liquid 11 itself does not wave much due to the influence of the interfacial tension acting between the liquid 11 and the solid surface of the liquid tank 12. For example, when the surface of the liquid tank 12 is roughened, the wettability of the liquid 11 with respect to the surface of the liquid tank 12, that is, the interface tension increases, and the liquid 11 in the liquid tank 12 sticks to the surface of the liquid tank 12. Even if the liquid tank 12 is moved in such a state, the liquid 11 moves with the liquid tank 12 which is a solid, and the liquid surface of the liquid 11 is not greatly touched. Therefore, although depending on the acceleration of moving the liquid tank 12, the liquid tank 12 itself can be moved if it is not moved rapidly.

  Further, if there is even a small amount of liquid in the wafer 13, the liquid 11 is an incompressible fluid unlike gas, so that hydrostatic pressure acts uniformly over the entire liquid surface, and the wafer 13 is a large size wafer 13. However, it becomes possible to support the wafer 13 with uniform stress in the surface of the wafer 13.

  Further, it is desirable that the temperature of the liquid 11 is kept as high as the temperature of the wafer 13 as much as possible, or at most about room temperature. Although the laser beam is irradiated inside the wafer 13, there is no possibility that the wafer 13 generates a large amount of heat by irradiating the laser beam in a pulsed manner. When a temperature difference occurs in the temperature distribution, the shape of the wafer 13 may be deformed due to the temperature difference. In order to prevent this, it is preferable to adjust the temperature of the liquid 11 so that a stable and uniform temperature distribution is obtained without forming a temperature gradient.

  The observation optical unit 30 includes an observation light source 31, a collimating lens 32, a half mirror 33, a condensation lens (condensing lens) 34, a CCD camera 35 as an observation means, an image processing unit 38, a television monitor 36, and the like. Yes.

  In the observation optical unit 30, the illumination light emitted from the observation light source 31 is irradiated on the surface of the wafer 13 through an optical system such as a collimator lens 32, a half mirror 33, and a condensation lens 24. Then, the reflected light from the surface of the wafer 13 is incident on a CCD camera 35 as observation means via the condensation lens 24, the half mirrors 23 and 33, and the condensation lens 34, and a surface image of the wafer 13 is captured. The

  The captured image data is input to the image processing unit 38 and used for alignment of the wafer 13 and is also displayed on the television monitor 36 via the control unit 50. Here, the control unit 50 includes a CPU, a memory, an input / output circuit unit, and the like, and controls the operation of each unit of the laser processing apparatus 1.

  The laser processing apparatus 1 constitutes a frame wafer transfer mechanism, an operation plate, an indicator lamp and the like (not shown). Here, as will be described in detail later, the frame wafer transport mechanism moves the wafer 13 affixed to the expanded tape 15 and the dicing frame 14 up and down, and positions and transports them to a predetermined location in the liquid tank 12. I do.

  At this time, switches and a display device for operating each part of the wafer placement unit 10 are attached to the operation plate. In addition, the indicator lamp displays in a timely manner the operation status of the laser processing apparatus 1 during operation, at the end of operation, and at an emergency stop.

  FIG. 2 is a conceptual diagram showing details of the driving means 25 shown in FIG. As shown in FIG. 2, the driving means 25 includes a lens frame 26 that holds the condensation lens 24, a Z fine movement means 27 that is attached to the upper surface of the lens frame 26 and slightly moves the lens frame 26 in the Z direction in the figure. A holding frame 28 for holding the Z fine moving means 27, and PZ1, PZ2, and the like which are linear fine moving means for moving the holding frame 28 in parallel with the wafer 13 are configured. The wafer 13 is supported by the liquid surface of the liquid 11 stored in the liquid tank 12. As a result, a laser irradiation unit including an optical system such as the condensation lens 24 scans the wafer 13 to modify the inner surface of the wafer 13.

  2 uses a piezoelectric element (not shown) that expands and contracts when a voltage is applied. Due to the expansion and contraction of the piezoelectric element, the condensation lens 24 is finely fed in the Z direction, and the position of the condensing point of the laser beam P in the Z direction is precisely positioned.

  The holding frame 28 shown in FIG. 2 is supported by two pairs of parallel springs composed of four piano wires (not shown), is movable in the XY directions, and is restricted from moving in the Z direction. The support method of the holding frame 28 is not limited to the above method. For example, the upper and lower sides of the holding frame 28 are sandwiched by a plurality of balls to restrain the movement in the Z direction and support the movement in the XY direction. You may do it.

  Also, the linear fine movement means PZ1 and PZ2 shown in FIG. 2 use a piezoelectric element (not shown) like the Z fine movement means 27, and one end is fixed to the case main body of the laser head 40 (see FIG. 1). The other end is in contact with the side surface of the holding frame 28.

  FIG. 3 is a plan view of the driving means 25 shown in FIG. As shown in FIG. 3, two linear fine movement means PZ <b> 1 and PZ <b> 2 are arranged in the X direction, one end of each being fixed to the case main body of the laser head 40 (see FIG. 1) and the other end of the holding frame 28. It is in contact with the side. Therefore, by controlling the voltage applied to the linear fine movement means PZ1 and PZ2, the condensation lens 24 can be finely fed back and forth in the X direction, and the laser beam P (see FIG. 2) can be finely fed back and forth in the X direction or vibrated. You can make it.

  A piezoelectric element may be used for one of the linear fine movement means PZ1 and PZ2, and the other may be an elastic member such as a spring material. In addition, as shown in FIG. 3, instead of using two linear fine movement means PZ1 and PZ2, three or more linear fine movement means may be arranged on the circumference. In this case, it is desirable to arrange the linear fine movement means at equal positions on the circumference.

  1 and 2, the laser beam L is emitted from the laser oscillator 21, and this laser beam L passes through an optical system such as a collimator lens 22, a half mirror 23, a condensation lens 24, and the like. The inside of the wafer 13 is irradiated as laser light P. At this time, the Z direction position of the condensing point of the irradiated laser beam P is adjusted in the Z direction position of the optical system (laser beam irradiation unit) by the control signal (XYZθ signal) from the control unit 50 and the Z fine movement means 27. By the position control of the condensation lens 24 by the above, it is accurately set to a predetermined position inside the wafer 13.

  In this state, a control signal (XYZθ signal) from the control unit 50 is processed and sent in the X direction, which is the dicing direction of the wafer 13, and the condensation lens 24 is reciprocated by the linear fine movement means PZ1 and PZ2 provided in the laser head 40. It is moved slightly. Then, the laser beam P is vibrated in the X direction or an arbitrary XY direction in parallel with the wafer 13, and the condensing point of the laser beam P forms a modified region while slightly vibrating inside the wafer 13. As a result, one line of the modified region by multiphoton absorption is formed inside the wafer 13 along the planned cutting line of the wafer 13.

  In addition, you may add the vibration of the Z direction by the Z fine movement means 27 as needed. In addition, the laser beam P is sent back and forth like a perforation by sending the optical system (laser beam irradiation part) in the X direction while slowly reciprocating and finely feeding the laser beam P in the X direction which is the processing direction. You may make it irradiate repeatedly. When one modified region is formed along the planned cutting line in this way, the laser beam P is sequentially moved, and the modified region is similarly formed on the next line.

  Here, as the transparent film for expanding, such as the expanding tape 15 attached integrally to the back surface of the wafer 13 and the surface of the dicing frame 14, a polyolefin sheet or the like can be used. As the liquid 11 for floating the wafer 13, a standard refraction liquid made of Cargill can be used. The refractive index of this standard refraction liquid made of Cargill is from 1.000 to 1.395 of “Series AAA” which is a slightly volatile colorless prolocarbon liquid, and is an ethylene iodide volatile liquid. There are several types of “Series M” from 1.705 to 1.800, and it is desirable to use the liquid 11 that makes the refractive index difference as small as possible depending on the material of the surface of the wafer 13. That is, if the refractive index of the wafer 13 and the refractive index of the liquid 11 are not substantially different and are substantially equal, the laser beam P is introduced into the liquid 11 without being reflected at the interface of the liquid 11 as it is.

For reference, reference materials for standard refraction liquid made by Cargill include the following. HYPERLINK "http://www.moritex.co.jp/products/func/list#refraction.php?c#code=5-2-1-1" http://www.moritex.co.jp/products/ func / list # refraction.php? c # code = 5-2-1-1
HYPERLINK "http://www.kyoto-kem.com/en/products/stdsol/ref#sol.html"http://www.kyoto-kem.com/en/products/stdsol/ref#sol.html.

  The liquid 11 that supports the wafer 13 is desirably a liquid 11 that absorbs the laser beam P as much as possible. For example, in the case of water, it has a property of particularly absorbing infrared light, and in the case of infrared light, it has an absorption band in the vicinity of 3300 cm −1 or 1520 cm −1. As described above, when the liquid 11 that absorbs the laser beam P is used depending on the wavelength range in which the laser beam P is used, excess reflection on the wafer 13 is eliminated, and therefore laser burning due to the reflected beam hardly occurs. .

  Next, a series of steps for laser processing the wafer 13 will be described. FIG. 4 is a process diagram showing a flow of a laser processing process by the laser processing apparatus of the present invention. First, in FIG. 4A, the surface of the expanded tape (dicing tape) 15 attached integrally to the back surface of the wafer 13 and the surfaces of the dicing frames 14 and 14 is attached to the suction means 61a of the frame wafer transport mechanism 61. Adsorbed by 61b and 61c and transported to a predetermined position of the liquid tank 12 in the wafer mounting portion 10 shown in FIG. At this time, the back surface of the wafer 13 and the front surfaces of the dicing frames 14 and 14 are both vacuum-sucked by the suction means 61a, 61b and 61c, and the horizontal state (level) is maintained.

  Next, in FIG. 4B, the wafer 13 and the dicing frames 14 and 14 are vacuum-sucked by the suction means 61a, 61b and 61c and placed at a predetermined position in the liquid tank 12, and the liquid inlet 12a. The liquid 11 is injected into the liquid tank 12 from the inside.

  Next, in FIG. 4C, after the liquid 11 is fully filled into the liquid tank 12, the frame wafer transport mechanism 61 is filled with air to open the suction means 61a, 61b, 61c, and the frame wafer. The transport mechanism 61 is removed from the surface of the expanding tape 15.

  Next, in FIG. 4D, in a state where the wafer 13 is supported by the liquid surface of the liquid 11, the laser beam P is passed through the expand tape 15 while moving the laser processing unit 62 in the XY direction. Laser processing is performed by irradiating the back surface. That is, the laser modified layer is formed in the XY direction inside the wafer 13 by moving the laser beam P in the XY direction. At this time, since the wafer 13 is supported by the liquid surface of the liquid 11 and kept in a horizontal state, a modified layer is formed in the wafer 13 with high accuracy and uniformity.

  Next, in FIG. 4E, the frame wafer transport mechanism 61 is moved to a predetermined position on the liquid tank 12, and the expanded tape 15 is sucked by the suction means 61a, 61b, 61c of the frame wafer transport mechanism 61. Thus, the wafer 13 and the dicing frames 14 and 14 are supported. At this time, the liquid 11 filled in the liquid tank 12 is discharged from the liquid discharge port 12b.

  Next, in FIG. 4F, since the surface tension due to the liquid 11 does not work, after the surface of the wafer 13 is dried, the wafer 13 and the dicing frames 14 and 14 are lifted up by the frame wafer transport mechanism 61 to a predetermined level. Transport to position.

  The wafer 13 diced (modified) by the laser processing apparatus as described above is divided into chips by applying an external stress. This chip processing is performed by, for example, an expanding apparatus described below.

  Next, a chip forming process for dividing the wafer 13 into laser chips after laser processing will be described. FIG. 5 is a process diagram showing the wafer chip processing by the expanding apparatus. That is, the wafer 13 that has been laser diced (modified) by the laser processing apparatus is placed on the peeling table 71 with the surface facing up, as shown in FIG. In other words, the expanded tape 15 attached to the back surface of the wafer 13 is placed on the peeling table 71. The dicing frames 14 and 14 are fixed at predetermined positions by a frame fixing mechanism (not shown).

  In this way, when the wafer 13 is placed on the peeling table 71 and the dicing frames 14 and 14 are fixed, the wafer 13 is disposed so as to surround the peripheral portion of the peeling table 71 as shown in FIG. The ring 72 is pushed up by an elevating mechanism (not shown) and rises. Thereby, the expanding tape 15 affixed to the back side of the wafer 13 is expanded (expanded) radially.

  Then, when the expand tape 15 is expanded, an external stress is applied to the wafer 13, and the wafer 13 is divided starting from the modified layer as shown in FIG. 5B. At this time, since the modified layer of the wafer 13 is formed along the street, the wafer 13 is divided along the street. That is, since the street is set between individual chips, the wafer 13 is divided into individual chips. The wafer 13 that has been laser diced in this manner is in a state of being divided into individual chips by applying an external stress.

  In the above embodiment, the wafer 13 mounted on the dicing frames 14 and 14 is sucked and held by a wafer table (not shown) and laser dicing is performed. However, the wafer 13 is attached to the dicing frames 14 and 14. Laser dicing can also be performed by holding the wafer table directly without mounting. Further, it is possible to adopt a configuration in which laser dicing is performed by attaching only a tape (dicing tape) capable of transmitting laser light to the back surface of the wafer 13 without mounting on the dicing frames 14 and 14.

  As described above, the laser processing apparatus of the present invention is a laser processing apparatus that performs substrate modification for dividing a substrate into chips, and is basically a liquid tank that fills a liquid and supports the entire substrate. And a substrate supported by the liquid level of the liquid filled in the liquid tank, a transparent expanded film attached to the back surface of the substrate so as to hold the substrate, and has a stretchable elasticity. And a laser beam irradiating means for modifying the inside or the surface of the substrate by irradiating the substrate with a laser beam through an expanded film.

  According to the laser processing apparatus having such a configuration, even if the workpiece can support the substrate without destroying the fragile structure on the surface of the substrate and bends largely by its own weight, the liquid tank The substrate can be supported in a horizontal state with the liquid surface filled in the substrate. In addition, excessive heating near the surface of the substrate due to laser light irradiation causes the entire surface of the substrate to be immersed in the liquid uniformly when the wafer comes into contact with the liquid surface of the liquid filled in the liquid tank. Can be efficiently cooled to keep the surface temperature of the substrate constant. Furthermore, since the heat capacity of the liquid is large, the temperature of the liquid that is cooling the wafer does not rapidly increase, so that a stable temperature environment for the wafer can be maintained.

  As for the phenomenon in which a part of the laser light is transmitted from the substrate when the substrate is irradiated with the laser light, the refractive index of the liquid is higher than that of air, for example, the refractive index of water is about 1.3. Therefore, when the surface of the substrate is composed of an oxide film such as a silicon oxide film, the difference in refractive index between the substrate and the liquid can be made smaller than when laser light is emitted into the air. . Further, the liquid level of the liquid can also enter the uneven portion of the substrate surface.

  As a result, if the substrate is supported by the liquid surface, the difference in refractive index is reduced, the influence of the roughness shape of the substrate surface is eliminated, and the scattering of laser light is greatly reduced. It greatly reduces the energy loss of laser light that occurs in the vicinity. As a result, it is possible to protect the element surface by suppressing heat generation on the substrate surface, efficiently guide excess laser light into the liquid, and effectively attenuate the energy.

  Due to such a phenomenon, the difference in refractive index between the substrate and the liquid surface becomes small, and the roughness shape on the surface of the substrate embeds the shape by the liquid all around the shape. For this reason, it becomes difficult to receive the influence of the scattering by the roughness shape of the substrate surface. That is, laser light partially transmitted from the substrate is likely to enter the liquid, and laser light scattering is also reduced. Furthermore, by reducing the transmission and reflection of laser light in the liquid tank, it is possible to suppress laser burn on the substrate surface due to scattered or reflected laser light.

  In order to reduce the transmission and reflection of laser light in the liquid tank, for example, in a simple method, it is possible to prevent the reflection of laser light from the inner surface of the liquid tank by coloring the inner surface of the liquid tank black. Become. Further, an antireflection film (for example, a film thickness of λ / 4) corresponding to the wavelength λ of the laser beam used on the inner surface of the liquid tank may be coated.

  Further, the laser light entering the liquid can be absorbed and attenuated by selecting an appropriate liquid containing molecules having an absorption band with respect to the wavelength of the laser light to be used. In addition, since what kind of liquid is used depends on the wavelength of the laser light to be used, it is desirable to use a liquid having good absorbency as appropriate according to the laser light to be used.

  Due to these effects, some laser light leaking from the substrate (workpiece) is scattered, and other effects such as proximity effects such as burning and deterioration of other parts of the substrate surface due to reflection of the laser light. Can be prevented.

  The laser processing method of the present invention is a laser processing method in which a modified layer is formed inside a substrate by irradiating a laser beam through an expanded film attached to the back surface of the substrate, and a large workpiece (substrate). Even in this case, the substrate is not bent by its own weight, and the horizontal state (level) of the substrate can be maintained with a simple method with high accuracy. Furthermore, the surface temperature of the substrate can be kept constant by effectively discharging the amount of heat accumulated on the surface of the substrate to the liquid as the laser light is irradiated.

  In addition, the laser light that escapes from the surface side of the substrate is reflected by the laser light irradiation, so that the proximity effect that is irradiated again on the surface of the substrate does not occur, and the laser light is reflected on the surface of the substrate. Material is used. Furthermore, even if the surface of the substrate has a minute and fragile structure and cannot be supported with the surface facing down, the surface of the substrate is supported by the liquid level. Laser processing can be performed in a stable support state without being damaged. Further, since the expanded film and the substrate are bent by their own weight, it is possible to prevent a phenomenon in which misalignment occurs without taking the level of the laser light irradiation surface.

  According to the above embodiment, since the refraction of the liquid is almost equal to the refractive index of the substrate, even if it is a liquid, by making the refractive index of the substrate and the refractive index of the liquid close to each other, There is no difference in refractive index, and energy loss due to scattering or the like occurring at the interface is greatly reduced. Therefore, when a part of the laser beam escapes from the surface into the liquid, the energy of the laser beam is locally used in the vicinity of the interface, and the surface of the substrate can be prevented from generating heat locally.

  Further, when the laser beam irradiation means irradiates the laser beam in a pulsed manner, there is no fear that the liquid interface greatly generates heat, and the temperature of the liquid can be adjusted to be as stable and uniform as possible. As a result, it is possible to suppress the deformation of the substrate shape due to the temperature difference even when there is a possibility that a temperature difference may be caused on the liquid surface by gradually heating up the number of irradiations. In other words, by irradiating laser light in a pulsed manner, that is, intermittently or intermittently, without excessive temperature gradients, wafer cracking due to thermal stress is reduced and quality performance is improved. Can be planned.

  As described above, the laser processing apparatus and the laser processing method according to the present invention have been described in detail based on the specific examples. However, the present invention is not limited to the contents of the above examples, Various modifications can be made without departing from the spirit, and the present invention naturally extends to the modifications.

  Since the laser processing apparatus according to the present invention can form a chip by forming a modified layer with high accuracy on a substrate, it can be effectively used for various semiconductor manufacturing apparatuses.

DESCRIPTION OF SYMBOLS 1 Laser processing apparatus 10 Wafer mounting part 11 Liquid 12 Liquid tank 12a Liquid inlet 12b Liquid outlet 13 Wafer (substrate)
14 Dicing frame 15 Expanding tape (dicing tape)
20 Laser optics 21 Laser oscillator 22, 32 Collimate lens 23, 33 Half mirror 24, 34 Condensation lens (Condensing lens)
25 Driving means 26 Lens frame 27 Z fine movement means 28 Holding frame 30 Observation optical part 31 Observation light source 35 CCD camera 36 Television monitor 38 Image processing part 40 Laser head 50 Control part 61 Frame wafer transport mechanism 61a, 61b, 61c Adsorption means 62 Laser processing part 71 Peeling tape 72 Ring L Laser beam P Laser beam PZ1, PZ2 Linear fine movement means

Claims (12)

A laser processing apparatus for modifying a substrate for dividing a substrate into chips by laser light,
The substrate supported by a liquid surface;
A transparent expanded film affixed to the back surface of the substrate;
A laser processing apparatus, comprising: a laser beam irradiation unit that irradiates the substrate with the laser beam through the expanded film to modify the inside or the surface of the substrate. A laser processing apparatus for modifying a substrate for dividing a substrate into chips by laser light,
A liquid tank filled with liquid;
The substrate supported by the liquid level of the liquid filled in the liquid tank;
A transparent expanded film affixed to the back surface of the substrate;
A laser processing apparatus comprising: a laser beam irradiation unit configured to irradiate the expanded film with the laser beam to modify the inside or the surface of the substrate.   The laser beam irradiation means irradiates the laser beam on the surface side of the expanded film attached to the back surface of the substrate with the back surface of the substrate facing the substrate surface on which the metal film is formed facing upward. The laser processing apparatus according to claim 1 or 2.   The laser processing apparatus according to claim 2, wherein the liquid tank has a property of transmitting and absorbing the laser light.   The laser processing apparatus according to claim 1, 2, 3, or 4, wherein the refractive index of the liquid is substantially equal to the refractive index of the substrate.   5. A laser processing apparatus according to claim 1, wherein said laser beam irradiation means irradiates laser beam in a pulsed manner. A laser processing method for modifying a substrate to divide a substrate into chips by laser light,
A first step of supporting the substrate with a liquid surface;
And a second step of irradiating the substrate supported by the liquid surface with laser light to modify the inside or the surface of the substrate. A laser processing method for modifying a substrate to divide a substrate into chips by laser light,
A first step of supporting the substrate, to which the transparent expanded film is attached, on the liquid surface;
And a second step of modifying the inside or the surface of the substrate by irradiating the substrate supported by the liquid surface with the laser light through the expanded film. Processing method. A laser processing method for modifying a substrate to divide a substrate into chips by laser light,
A first step of attaching a transparent expanded film to the back surface of the substrate facing the substrate surface on which the metal film is formed;
A second step of transporting the substrate with the expanded film attached thereto to a liquid tank;
A third step of filling the liquid tank with a liquid and supporting the substrate to which the expanded film is attached on the liquid surface of the liquid;
A fourth step in which the substrate supported by the liquid surface is irradiated with the laser light through the expanded film to modify the inside or the surface of the substrate;
After a modified layer is formed on the inside or the surface of the substrate, a fifth step of discharging the liquid supporting the substrate from the liquid tank;
After the liquid is discharged from the liquid tank, the sixth step of conveying the substrate with the expanded film attached thereto from the liquid tank to the outside;
A laser processing method comprising: a seventh step of generating chips by dividing and separating the substrate on which the expanded film is attached in a region where the modified layer is formed.   The substrate is modified by irradiating the surface of the expanded film attached to the back surface of the substrate with the laser beam facing upward on the back surface of the substrate facing the substrate surface on which the metal film is formed. The laser processing method according to claim 9.   11. The laser processing method according to claim 7, 8, 9, or 10, wherein a refractive index of the liquid is substantially equal to a refractive index of the substrate.   The laser processing method according to claim 7, wherein the laser beam is irradiated in a pulse manner.

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