JP2010029928A - Laser beam machining apparatus and laser beam machining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining apparatus and a laser beam machining method in which a workpiece is held without touching a device forming region and capable of emitting a laser beam from the rear face side, and in which a reformed layer can be formed accurately on a workpiece even with a warp therein. <P>SOLUTION: An excess region 10b which is provided in the periphery of the surface of a workpiece 10 and which has no device 10a formed in is sucked and held by means of an annular holding face 21a installed in the holder 21 of a holding means 20 and inclined inward radially. Then, a laser beam 5 having a wavelength passing through the workpiece 10 and an adhesive tape 12 is emitted from the rear face side of the workpiece 10 along a planned dividing line, on a converging point inside the workpiece 10 by a laser beam irradiation means 3, and a reformed region is formed inside the workpiece 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method and apparatus for processing a workpiece such as a semiconductor wafer using a laser beam. More specifically, the present invention relates to a technique for forming a modified region on a work division planned line by irradiating a laser beam from the back side of the work.

  In the manufacturing process of a semiconductor device, a circuit such as an IC (integrated circuit) or an LSI (large-scale integration) is formed in a matrix on the surface of a substantially disc-shaped semiconductor wafer, Thereafter, the wafer on which the plurality of circuits are formed is cut into a lattice shape along a predetermined street (cutting line) to separate each circuit into chips.

  Usually, a cutting device called a dicer is used for cutting (dicing) a semiconductor wafer. In recent years, a method of cutting a workpiece such as a semiconductor wafer using a laser beam has been developed (for example, see Patent Documents 1 and 2). For example, in the processing method described in Patent Document 1, a workpiece made of an oxide single crystal is irradiated with laser light, and the molecules of the oxide single crystal are dissociated and evaporated by a photochemical reaction, whereby a predetermined position of the workpiece is obtained. A groove is formed in the workpiece, and the workpiece is cleaved along the groove.

  Further, in the cutting method described in Patent Document 2, pulsed laser light having transparency to the work is irradiated to the inside of the work with a converging point, and an altered region is formed along the planned division line. . Since this deteriorated region has a lower strength than the other portions, the work is divided by applying the external force along the planned dividing line and starting from the deteriorated layer.

  On the other hand, for workpieces with irregularities on the surface, such as MEMS (Micro Electro Mechanical Systems), and workpieces with TEGs formed on the lines to be divided, the laser beam reaches the inside of the workpiece due to the irregularities and TEGs. There may not be. In particular, these effects are large in a work having a wide unevenness and a work having devices with narrow pitches and narrow streets.

  Therefore, conventionally, a method of irradiating a laser beam from the back side when forming an altered region in a work has been proposed (see, for example, Patent Documents 3 to 5). For example, in the laser processing methods described in Patent Documents 3 and 4, a workpiece is placed on the chuck table with the surface facing down, and laser light is emitted into the workpiece via a dicing film attached to the back surface of the workpiece. Irradiating. In these methods, the influence of the laser beam on the dicing film and the energy loss of the laser beam are reduced by using laser light having a wavelength having transparency for both the dicing film and the workpiece.

  Further, in the cleaving method described in Patent Document 5, a dicing tape having adhesiveness on both sides is used, and a work held on the ring frame via the dicing tape is placed on a transparent support plate made of glass or the like. It is placed. The back surface of the workpiece is irradiated with laser light through the transparent support plate and the dicing tape.

  Furthermore, warping may occur in the process up to the dicing process for semiconductor wafers, etc. In the case of such warped workpieces, the focal point position of the laser beam varies in the depth direction, resulting in the formation of altered regions. Accuracy is reduced. For this reason, in the conventional laser processing apparatus, the surface displacement of the workpiece is detected in advance, and based on the result, the laser beam is irradiated while adjusting the position of the focal point in the depth direction (see Patent Document 6). ).

JP-A-10-305420 JP 2002-192370 A (Patent No. 3408805) JP 2006-148175 A JP 2007-173475 A JP 2008-132710 A JP 2008-16577 A

  However, the conventional techniques described above have the following problems. In other words, when processing a workpiece with irregularities on the surface, such as MEMS, if the workpiece surface is directly sucked and held on the chuck table as in the methods described in Patent Documents 3 and 4, the irregular shape is deformed. There is a problem that the yield decreases. Conventionally, a method of attaching a protective tape to the work surface and adsorbing and holding the work to the chuck table via this protective tape has been adopted, but even in that case, when the protective tape is applied or peeled off, There is also a problem that the deformation of the adhesive tends to occur and the adhesive remains.

  On the other hand, the method described in Patent Document 5 can irradiate laser light from the back side without touching the surface of the workpiece, but the structure of the dicing tape is complicated, so that it is more expensive than the conventional tape. . In addition, this tape can be used only in the dicing process and has low versatility. Furthermore, in order to use the dicing tape described in Patent Document 5, an apparatus provided with V irradiation means and IR laser irradiation means is required. For the above reason, when the method described in Patent Document 5 is applied, there is a problem that the manufacturing cost increases.

  Further, the processing method described in Patent Document 6 is effective for a work with a small degree of warpage, but generally, a piezo element or the like is used for adjusting the focal point position, and thus the degree of warpage is large. However, there is a problem that it becomes impossible to follow and processing accuracy is lowered.

  Therefore, the present invention can hold the workpiece without touching the device formation region, can irradiate the laser beam from the back side, and can form a modified layer with high accuracy even if the workpiece is warped. A main object is to provide a laser processing apparatus and a laser processing method.

  The laser processing apparatus according to the present invention is a laser processing apparatus that forms a modified region inside a workpiece having a plurality of devices formed on the surface, wherein the devices provided on the peripheral edge of the workpiece surface are formed. A holding means having an annular holding surface for holding a non-contact area, and a laser beam irradiation means for irradiating a laser beam having a wavelength that passes through the work toward the back surface of the work. The surface is inclined radially inward.

  In the present invention, since the holding surface for holding the workpiece in contact is annular and is configured to contact only the region where the device is not formed, when the workpiece is placed upside down, that is, the device is formed. Even when the surface (front surface) is arranged facing the holding portion, the holding surface does not contact the region where the device is formed. In addition, since the holding surface is inclined radially inward, the workpiece held on the holding surface is corrected to have a convex warpage on the back side.

  In this laser processing apparatus, one or a plurality of holes for sucking and holding the workpiece may be formed on the holding surface.

  On the other hand, the laser processing method according to the present invention irradiates a laser beam onto a workpiece having a plurality of devices formed on the front surface and supported by an opening of the annular frame via an adhesive tape attached to the back surface. And a laser processing method for forming a modified region in the workpiece, wherein the peripheral portion of the workpiece surface where the device is not formed is sucked and held by an annular holding surface inclined radially inward. And a step of irradiating a laser beam having a wavelength that passes through the workpiece and the adhesive tape from the back surface side of the workpiece along the planned division line with a focusing point inside the workpiece.

  In the present invention, since the peripheral portion where the device is not formed on the work surface is held in contact, the device is not affected even when the laser beam is irradiated from the back surface. Further, since the suction surface is held by the holding surface inclined inward in the radial direction so as to become lower toward the inner diameter side, convex warpage is corrected on the back side of the workpiece.

  According to the present invention, since the workpiece is held by the annular holding surface inclined radially inward, the workpiece can be held without touching the device formation region, and the laser beam can be irradiated from the back surface side. Work warp can be corrected and machining accuracy can be improved.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. In addition, this invention is not limited to embodiment shown below. FIG. 1 is a perspective view showing the configuration of the laser processing apparatus of this embodiment. 2 is a perspective view showing a specific configuration of the holding means 2 shown in FIG. 1, and FIG. 3 is a cross-sectional view.

  As shown in FIG. 1, the laser processing apparatus 1 according to the present embodiment is provided with at least a holding unit 2 that holds a workpiece 10 and a laser beam irradiation unit 3 that irradiates a predetermined position of the workpiece 10 with a laser beam. ing.

  Examples of the workpiece 10 to be processed by the laser processing apparatus 1 according to this embodiment include a semiconductor wafer, an adhesive tape such as DAF (Die Attach Film), an inorganic material such as glass, silicon and sapphire, a metal material, or a plastic. And various processing materials that require micron-order accuracy. As shown in FIG. 2, the work 10 has an adhesive tape 10 attached to the back surface thereof, and is supported by the opening of the ring frame 11 via the adhesive tape 10. And it is processed in the state supported by this ring frame 11.

  On the other hand, as shown in FIG. 3, the holding means 2 in the laser processing apparatus 1 of the present embodiment includes a holding portion 21 having an annular holding surface 21a, and a plurality of clamps 22 that detachably fix the ring frame 11. Is provided. The holding portion 21 in the holding means 2 has a recess formed at a position that matches the region where the device 10a is formed when the workpiece 10 is placed, and the inner diameter of the holding surface 21a that holds the workpiece 10 in contact with it. Is larger than the region where the device 10a is formed. In other words, the holding unit 21 has an area in which the holding surface 21 a is not formed with the device 10 a provided on the peripheral edge of the work 10 when the work 10 is placed with the back surface facing the laser beam irradiation unit 3. Region) 10b only.

  Moreover, in this laser processing apparatus 1, the holding surface 21a of the holding part 21 is inclined inward in the radial direction so as to become lower toward the inner diameter side. Further, one or a plurality of holes are provided in the holding surface 21a, and the work 10 can be sucked and held by applying a negative pressure in each hole by the suction means 6.

  The holding means 2 described above is movable in the x direction and the y direction orthogonal to the x direction by the feeding means. Specifically, a ball screw 33a is arranged between a pair of guide rails 32a and 32b arranged in parallel to each other on the base 31, and a motor 33b is attached to one end of the ball screw 33a. The other end is rotatably supported by the bearing block 33c.

  A sliding block 34 is placed on the guide rails 32a and 32b and the ball screw 33a. On the sliding block 34, a pair of guide rails 35a and 35b and a ball screw 36a are parallel to each other. Has been placed. The ball screw 36a also has a motor 36b attached to one end, and the other end is rotatably supported by a bearing block 36c. Further, a sliding block 37 is placed on the guide rails 35 a and 35 b and the ball screw 36 a, and the holding means 2 is installed on the sliding block 37.

  In the feeding means constituted by these members, when the ball screw 33a is driven by the motor 33b, the sliding block 34 is guided and moved by the guide rails 32a and 32b, whereby the holding means 2 is moved in the x direction. Moving. On the other hand, when the ball screw 36a is driven by the motor 36b, the sliding block 37 is guided and moved by the guide rails 35a and 35b, thereby moving the holding means 2 in the y direction.

  On the other hand, the laser beam irradiation means 3 in the laser processing apparatus 1 of the present embodiment is disposed above the holding means 2 and has a wavelength of laser light that passes through the workpiece 10 such as a YAG laser oscillator or a YVO laser oscillator. And an optical component such as a mirror and a condenser lens for irradiating the workpiece 10 with the oscillated laser light.

  Moreover, the laser processing apparatus 1 of this embodiment may be provided with the displacement detection means 4 for detecting the displacement of the workpiece 10. When the workpiece 10 is a semiconductor wafer or the like, warping and undulation may occur in the process up to the dicing process. By detecting the displacement of the workpiece 10 by the displacement detecting means 4, the position and degree of the warping and undulation can be determined. I can know.

  For example, as shown in FIG. 1, the surface detection unit 4 includes a laser beam irradiation unit including a laser oscillator and a laser beam detection unit including a sensor and the like above the holding unit 2. It can be set as the structure which irradiates the workpiece | work 10 with the laser beam of the wavelength reflected by a back surface, and detects the reflected light. In this case, the amount of reflected light is measured in the laser light detection unit, and the change in the distance from the back surface of the workpiece 10 to the laser light detection unit, that is, the displacement of the back surface of the workpiece 10 can be obtained from the change in the value.

  Note that the configuration and the detection method of the displacement detection means are not particularly limited as long as the displacement of the front surface or the back surface of the workpiece 10 can be detected. For example, in the laser processing apparatus 1 shown in FIG. 1, the displacement detection means 4 and the laser light irradiation means 3 are provided separately. However, these are integrated so that the processing laser light and the displacement measurement laser light are combined. It may be coaxial.

  Next, the operation of the laser processing apparatus 1 according to the present embodiment, that is, a method for processing the workpiece 10 using the laser processing apparatus 1 will be described. FIG. 4 is a cross-sectional view schematically showing a method of processing the workpiece 10 by the laser processing apparatus 1 of the present embodiment. In the laser processing method of this embodiment, first, as shown in FIG. 2, the workpiece 10 to be processed is supported on the opening of the ring frame 11 via the adhesive tape 12. At this time, the adhesive tape 12 is affixed to the back surface of the workpiece 10.

  As shown in FIGS. 2 and 4, the work 10 is placed on the holding portion 21 of the holding means 2 with the laser beam turned up so that the laser beam is incident from the back surface of the work 10, and the ring frame 11 is clamped 22. Secure with. Thereafter, the suction means 6 is operated, and the surplus area 10a of the workpiece 10 is sucked and held by the holding surface 21a. At this time, as shown in FIG. 4, stress is applied to the workpiece 10 in the direction in which the central portion is recessed, so that the warpage with the convex back surface is corrected.

  Next, the laser beam irradiating means 3 causes the laser beam 5 having a wavelength that passes through the workpiece 10 and the adhesive tape 12 to be focused on the inside of the workpiece 10 and from the back side of the workpiece 10 along the planned division line. Irradiate. For example, when the workpiece 10 is a semiconductor wafer using a silicon substrate, pulse laser light having a wavelength of 1064 nm is irradiated. As a result, a modified region is formed on the division line of the workpiece 10.

  At this time, for example, the position of the division line of the work 10 is irradiated with light (not shown) transmitted from the back surface of the work 10 to the inside of the work 10 via the adhesive tape 12. This can be confirmed by detecting reflected light (not shown) from the surface.

  Further, in the laser processing method of the present embodiment, the displacement detecting means 4 measures in advance the displacement of the portion irradiated with the laser beam 5, that is, the region corresponding to the planned division line on the back surface of the work 10, and the result Based on the above, it is desirable to irradiate the laser beam 5 while adjusting the focal point position in the thickness direction of the workpiece 10. As a result, even when the workpiece 10 is warped or undulated, the machining position can be made constant, so that the altered region can be formed with high accuracy.

  For example, when the workpiece 10 is a semiconductor wafer using a silicon substrate, the workpiece 10 is irradiated with a laser beam having a reflective wavelength of 635 nm and the change in the amount of reflected light is measured. It is possible to measure the displacement of the back surface of the plate.

  The workpiece 10 in which the modified region is formed on the planned division line by the above-described process can be easily and accurately divided along the planned division line by applying an external force and starting from the modified region. it can.

  As described above, in the laser processing apparatus 1 according to the present embodiment, the holding surface 21a for holding the workpiece 10 in contact is formed in an annular shape and is in contact with only the surplus region 10b where no device is formed. Even when it is arranged, it does not contact the region where the device 10a is formed. For this reason, the laser processing apparatus 1 of the present embodiment can hold the workpiece 10 without touching the device 10a even when the back surface of the workpiece 10 is irradiated with the laser beam 5.

  Furthermore, in the laser processing apparatus of the present embodiment, since the holding surface 21a of the holding portion 21 is inclined radially inward, it is possible to easily correct the convex warpage on the back surface side. As a result, the occurrence of defects due to deformation of the device 10a can be reduced and the yield can be improved. Moreover, since it is not necessary to stick a protective tape on the surface of the workpiece 10, the production efficiency can be improved and the manufacturing cost can be reduced.

  In the laser processing apparatus according to the present embodiment, the holding surface 21a of the holding portion 21 is inclined inward in the radial direction so that convex warpage can be corrected on the back surface side of the workpiece 10, but the holding surface is in the radial direction. When inclined outward, convex warpage can be corrected on the surface side.

  In addition, the laser processing apparatus of the present embodiment can be applied to the above-described processing of various workpieces. In particular, when laser light is irradiated from the surface side like an LED (Light Emitting Diode) element, the laser is processed. There is a possibility that the film may be altered or the element may be melted due to the influence of light, there is a possibility that the dust generated by the laser light irradiation may adhere to the element, and a defect may occur. It is suitable for processing such as those that have been processed, those in which TEGs are formed on the surface of the planned division lines, and those in which the width of the planned division lines is narrow.

It is a perspective view which shows the structure of the laser processing apparatus which concerns on embodiment of this invention. It is a perspective view which shows the specific structure of the holding means 2 shown in FIG. It is sectional drawing about the specific structure of the holding means 2 shown in FIG. It is sectional drawing which shows typically the method of processing the workpiece | work 10 with the laser processing apparatus 1 of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser processing apparatus 2 Holding means 3 Laser beam irradiation means 4 Displacement detection means 5 Laser light 6 Suction means 10 Work 10a Device 10b Excess area 11 Ring frame 12 Adhesive tape 21 Holding part 21a Holding surface 22 Clamp 31 Base 32a, 32b, 35a 35b Guide rail 33a, 36a Ball screw 33b, 36b Motor 33c, 36c Bearing block 34, 37 Sliding block

Claims (3)

A laser processing apparatus for forming a modified region inside a work having a plurality of devices formed on a surface thereof,
Holding means provided with an annular holding surface that contacts and holds a region where the device is not formed, which is provided at the peripheral portion of the workpiece surface;
A laser beam irradiation means for irradiating a laser beam having a wavelength that transmits the workpiece toward the back surface of the workpiece;
A laser processing apparatus in which the holding surface is inclined radially inward.   The laser processing apparatus according to claim 1, wherein the holding surface is formed with one or a plurality of holes for sucking and holding the workpiece. A plurality of devices are formed on the front surface, and a workpiece is supported on the opening of the annular frame via an adhesive tape attached to the back surface, and a laser beam is irradiated to form a modified region in the workpiece. A laser processing method,
Adsorbing and holding a peripheral portion of the workpiece surface where the device is not formed by an annular holding surface inclined radially inward;
And a step of irradiating a laser beam having a wavelength that passes through the workpiece and the adhesive tape from the back side of the workpiece along the planned dividing line with a focusing point inside the workpiece.

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