JP2018041895A - Processing method of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow for precise division of a wafer by pressing force of pressing means.SOLUTION: After forming a frame unit (U) by sticking a tape (T) expressing contractility by heating to a prescribed temperature or more, to the back side (W2) of a wafer (W), and then sticking the outer periphery of the tape to a frame (F), a laser processing groove (M) becoming a division start point is formed in the surface (W1) of the wafer along a first street (L1) and a second street (L2). Thereafter, the wafer is divided along the first street and second street, by pressing the wafer through the tape with a pressing blade (34) along the laser processing groove. When performing division, the tape is heated and shrank along the first street immediately after division, thus maintaining the interval between device chips (DC) adjacent to the first street.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a wafer processing method for dividing a wafer into devices along a street.

  In recent years, a method using laser processing has been proposed in order to divide a wafer in which a plurality of devices are partitioned by grid-like streets (see, for example, Patent Document 1). In the method of Patent Document 1, first, a laser processing groove is formed along the street by irradiating the back surface of the wafer with a pulsed laser beam having a wavelength that absorbs the wafer. Next, a protective sheet is attached to the surface of the wafer which is the opposite surface of the back surface where the laser processed grooves are formed. And a wafer is cut and divided | segmented by pressing with a pressing member along a laser processing groove | channel from the protection sheet side of a wafer.

  The division by the pressing member is sequentially performed on the streets extending in one direction among the lattice-like streets. Thereafter, the wafer is rotated 90 ° and the streets extending in the other direction (direction orthogonal to one direction) are sequentially pressed in the same manner, and the wafer is divided into individual device chips.

JP-A-2005-86160

  However, in the above-described wafer division, when the pressing member is pressed along the street, the protective sheet is extended, and adjacent chips move across the street. For this reason, after performing the division | segmentation about the street extended in one direction, when pressing with the press member about the street extended in the other direction, there exists a problem that it cannot divide | segment accurately with a pressing member being not positioned appropriately.

  This invention is made | formed in view of this point, and it aims at providing the processing method of the wafer which can divide | segment a wafer accurately by the press by a press means.

  The wafer processing method of the present invention is partitioned by a plurality of first streets extending in a first direction formed on the wafer surface and a plurality of second streets extending in a second direction orthogonal to the first direction. A wafer processing method that divides a wafer having a plurality of devices in each region, and a tape that exhibits shrinkage by heating at a predetermined temperature or more is attached to one surface of the wafer, and the outer periphery of the tape is After performing the frame unit forming step for forming the frame unit by sticking to the annular frame, and the frame unit forming step, the first street and the second street are processed by performing processing along the first street and the second street of the wafer. A split starting point forming step for forming a split starting point on the other surface or inside of the wafer along two streets and a split starting point forming step were performed. Further, the other surface side of the wafer of the frame unit is supported by the support means, the wafer is pressed in the vertical direction by the pressing means over the tape along the dividing start point, and the wafer is divided along the first street, A dividing step of dividing along the second street, and when dividing by pressing along the first street of the dividing step, the tape is heated along the first street immediately after the division by the pressing means. Shrinking to maintain the spacing between adjacent chips on the first street.

  According to this configuration, the tape that shrinks by heating is attached to the wafer, and the tape is heated along the first street pressed by the pressing means. it can. By such contraction, it is possible to satisfactorily maintain the interval between adjacent chips on the first street even after the pressure division along the first street. Thereby, in the subsequent pressing division of the second street, the accuracy of the pressing position of the pressing means with respect to the second street can be increased, and as a result, the dimensional accuracy of the chip formed by dividing can be increased.

  According to the present invention, even if the tape attached to the wafer is stretched by pressing by the pressing means, the tape can be shrunk by heating to divide the wafer with high accuracy.

It is a schematic perspective view which shows the wafer which concerns on this Embodiment, and is explanatory drawing which shows the frame unit formation step of this Embodiment. It is explanatory drawing which shows the division | segmentation starting point formation step of this Embodiment. It is explanatory drawing which shows the division | segmentation step of this Embodiment. It is explanatory drawing which shows the principal part of the said division | segmentation step. It is explanatory drawing similar to FIG. 4 which shows the division | segmentation step in a comparative example.

  Hereinafter, the wafer processing method of the present embodiment will be described with reference to the accompanying drawings. First, a wafer processed by the wafer processing method of the present embodiment will be described with reference to FIG. FIG. 1 is a schematic perspective view showing a wafer according to the present embodiment.

  As shown in FIG. 1, the wafer W is formed in a substantially rectangular plate shape, and the material is not particularly limited, but sapphire and the like can be exemplified. On the surface W1 of the wafer W, a plurality of first streets L1 and a plurality of second streets L2 extending in a direction orthogonal to the first streets L1 are formed. A plurality of devices D are formed in each region partitioned by the first and second streets L1 and L2.

  Next, a wafer processing method will be described with reference to FIGS. FIG. 1 shows a frame unit formation step according to the present embodiment, FIG. 2 shows a division start point formation step according to the present embodiment, and FIG. 3 shows an explanatory diagram of the division step. FIG. 4 shows a main part of the division step. In this embodiment, an example in which ablation processing is applied to a wafer processing method will be described. However, the present invention can be applied to other methods for forming a division starting point on a wafer.

  As shown in FIG. 1, a frame unit forming step is first performed. In the frame unit forming step, the back surface (lower surface) W2 side, which is one surface of the wafer W, is adhered to the tape T whose outer peripheral portion is adhered to the annular frame (annular frame) F. By these attachments, a frame unit U (see FIG. 2) in which the wafer W is held on the frame F via the tape T is formed. Here, as the tape T, a synthetic resin such as PVC (polyvinyl chloride) can be exemplified, and has a property of deforming so as to extend in the surface direction when a partial load is applied in the thickness direction as described later. Furthermore, it is assumed that the stretched portion is provided with a property of exhibiting shrinkage in a direction in which it is restored by heating to a predetermined temperature or higher.

  As shown in FIG. 2, after the frame unit formation step is performed, the division start point formation step is performed. In the division starting point forming step, the frame unit U is held on the chuck table 11 of a laser processing apparatus (not shown), and then the wafer W is irradiated with a laser beam. Here, the laser processing apparatus further includes a processing head 20 as laser beam irradiation means supported by an arm (not shown). Hereinafter, the processing head 20 will be described.

  The processing head 20 condenses a laser beam oscillated from an oscillator (not shown) by a condensing lens, and irradiates the surface W1 which is the other surface of the wafer W with the laser beam to perform laser processing. In this case, the laser beam has a wavelength that is transmissive to the wafer W, and a part of the wafer W is sublimated by laser irradiation to the wafer W, and laser ablation is performed. Accordingly, the laser processing groove M serving as a division starting point is formed by relatively moving the processing head 20 and the wafer W while irradiating the surface W1 of the wafer W with the laser beam.

  Here, the ablation means that when the irradiation intensity of the laser beam exceeds a predetermined processing threshold, it is converted into electronic, thermal, photochemical and mechanical energy on the solid surface, and as a result, neutral atoms, molecules, positive and negative A phenomenon in which ions, radicals, clusters, electrons, and light are explosively emitted and the solid surface is etched.

  In the division start point forming step, first, the frame unit U is placed on the chuck table 11 and the wafer W is sucked and held on the chuck table 11 via the tape T. Next, when the chuck table 11 is moved and rotated, for example, the first street L1 extends in parallel with the X-axis direction (first direction), and the second street L2 extends perpendicular to the X-axis direction. The wafer W is positioned so as to extend in parallel with the direction (second direction).

  Next, the machining start position of the first street L <b> 1 that moves in the X-axis direction by moving the chuck table 11 is positioned directly below the machining head 20. Thereafter, the chuck table 11 and the processing head 20 are relatively moved (processed) in parallel with the X-axis direction while irradiating the surface W1 of the wafer W with the laser beam. As a result, the laser beam is irradiated along the first street L1, the surface W1 of the wafer W is subjected to the ablation processing along the first street L1, and the laser processing groove M serving as the division starting point is formed.

  After the laser processing groove M is formed along the target first street L1, the irradiation of the laser beam is stopped, and the chuck table 11 and the processing head 20 correspond to the interval of the first street L1 in the Y-axis direction. Relative movement (index feed). Thereby, the processing head 20 can be matched with the 1st street L1 adjacent to the 1st street L1 of object.

  Subsequently, a similar laser processing groove M is formed along the adjacent first street L1. By repeating this operation, the laser processing grooves M are formed along all the first streets L1 extending in the X-axis direction. Thereafter, the chuck table 11 is rotated 90 ° around the rotation axis, and the laser processing groove M is formed by ablation along the second street L2 extending in the Y-axis direction.

  As shown in FIG. 3, the division step is performed after the division start point formation step is performed. In the dividing step, a breaking device is used to divide along the streets L1 and L2 where the laser processing grooves M are formed. Here, the braking device 20 will be described below. In the braking device 20, a moving table 23 is supported on the base portion 21 via a guide rail 22 so as to be movable in the left-right direction in FIG. 3. A circular opening 23a is formed in the moving table 23, and an annular turntable 24 is rotatably supported on the periphery of the opening 23a. The moving table 23 can be moved along the guide rail 22 by a moving mechanism (not shown), and the rotating table 24 can be rotated by a rotating mechanism (not shown). Clamps 25 that hold the frame F are provided on four sides of the rotary table 24.

  An imaging means 31 is disposed at the center on the base portion 21 and below the wafer W held on the rotary table 24. This imaging means 31 images the upper wafer W from the lower side (front surface W1 side) and detects the positions of the streets L1 and L2 with visible light.

  A pair of support bases (support means) 33 extending in the Y direction via posts 32 are disposed on both sides of the image pickup means 31 on the base portion 21. Each support base 33 supports the wafer W held on the rotary table 24 on both sides of one first street L1 from the lower side. A pressing blade (pressing means) 34 for pressing the wafer W from above is provided above the pair of support bases 33. The pressing blade 34 is formed in a long shape extending in one direction (perpendicular to the paper surface), and is moved up and down by a pressing mechanism (not shown).

  In the vicinity of or adjacent to the pressing blade 34, a heater 40 serving as a heating means is disposed via a support structure (not shown). The heater 40 is provided so that the temperature of the tape T can be raised by heating the tape T located on the tip side of the pressing blade 34 by releasing hot air, irradiating far infrared rays, or a combination thereof. In the case of the heater 40 using far-infrared rays, only the tape T may absorb the far-infrared rays, and the other components may not be heated without absorbing the far-infrared rays. The heater 40 includes a plurality of heaters arranged in parallel in the extending direction so as to heat an area pressed by the pressing blade 34 with the tape T, in other words, an elongated area parallel to the extending direction of the pressing blade 34. Or a heater provided with a nozzle or the like parallel to the extending direction.

  In the dividing step, first, the frame unit U is placed on the rotary table 24 with the tape T as the upper side, and the wafer W is held on the rotary table 24 by pressing the frame F by the clamp 25. Next, when the surface of the wafer W is imaged by the imaging means 31, the first street L1 is positioned between the pair of support bases 33 and immediately below the pressing blade 34 based on the captured image. At this time, the surface W1 side of the wafer W is supported by the support base 33 in both side regions sandwiching the first street L1. When the pressing blade 34 is lowered in this state, the wafer W is pressed in the vertical direction by the pressing blade 34 over the tape T along the laser processing groove M, and the laser processing groove M is divided at the first street L1. The wafer W is divided as a starting point.

  When dividing in this way, as shown in FIG. 4, the pressing blade 34 applies a pressing force to the tape T in the vertical direction, and the tape T is deformed so as to extend in a direction away from the pressing blade 34. . By this deformation, the interval between the adjacent device chips DC across the first street L1 is increased. Here, in the present embodiment, when the hot air is discharged from the heater 40 toward the tape T, the area along the first street L1 immediately after the division by the pressing blade 34 is heated to a predetermined temperature or higher. Since the tape T develops shrinkage when heated to a predetermined temperature or higher, the tape T stretched by the heating from the heater 40 is shrunk and restored so that the distance between the expanded device chips DC approaches the original position. Is done.

  After dividing the wafer W along the target first street L1, the frame unit U and the pressing blade 34 are relatively moved in a direction orthogonal to the first street L1 corresponding to the interval between the first streets L1. Thereby, the press blade 34 can be matched with the 1st street L1 adjacent to the 1st street L1 of object. Subsequently, the wafer W is similarly divided with respect to the adjacent first street L1, and this operation is repeated to divide the wafer W along all the first streets L1.

  Next, the rotary table 24 (see FIG. 3) is rotated by 90 °, and the wafer W is divided at the position along the second street L2 using the laser processing groove M as a division starting point in the same manner as described above. When dividing along the second street L2, the operation of the heater 40 may be stopped, or the tape T may be heated by the heater 40 as described above. Then, in the wafer W, the pressing blades 34 are pressed against all the first streets L1 and the second streets L2, so that the wafers W are divided into individual device chips DC while being stuck to the tape T.

  In the dividing step of the present embodiment, the tape T is heated and contracted along the first street L1 immediately after the division, so that when the tape T is divided along the second street L2, the tape T remains stretched. It can be suppressed. Here, in order to compare and explain the state after the division along the first street L1, the division step shown in FIG. 5 is considered as a comparative example.

  FIG. 5 is an explanatory view similar to FIG. 4 showing the division steps in the comparative example. In FIG. 5, the same reference numerals are assigned for the sake of convenience to the same configurations as those in the above embodiment. In the comparative example, the wafer W is divided along the first street L1 without heating the tape T as compared with the above embodiment. When the wafer W is divided in this way, the interval between the adjacent device chips DC across the first street L1 remains widened. For this reason, as the number of divisions in the first street L1 by the pressing blade 34 with respect to the wafer W increases, the deformation amount of the tape T as a whole increases, and as a result, the tape T rises or waves as shown in FIG. It will be in a state of hitting. In this state, if the orientation of the wafer W is changed by 90 ° and division is made along the second street L2, the position of the pressing blade 34 is shifted from the position of the second street L2, or the pressing blade 34 cannot be positioned. It may become impossible to divide.

  In this respect, in this embodiment, since the tape T is heated along the first street L1 pressed by the pressing blade 34, the deformation of the tape T can be suppressed, and the interval between the adjacent device chips DC is restored to the original state. It can be maintained well. Thereby, when pressing with the press blade 34 along the 2nd street L2 after that, the position accuracy of the press blade 34 with respect to the position of the 2nd street L2 can be improved. As a result, it is possible to efficiently apply a pressing force to the laser processing groove M from the pressing blade 34 to increase the processing accuracy, and it is also possible to increase the dimensional accuracy of the device chip DC formed by the division.

  In particular, when the indexes (intervals) of the streets L1 and L2 are shortened and the size of the device chip DC is decreased, the tape T is easily deformed as in the modified example of FIG. For example, with a small chip having an index size of about 1.5 times the thickness of the wafer W, such as an index of 150 μm for a wafer W thickness of 100 μm and an index of 300 μm for a wafer W thickness of 200 μm, the tape T may be deformed. The direction of the device chip DC changes so as to follow, and the tape T is easily deformed. Therefore, in such a case, there is a problem that the position of the pressing blade 34 with respect to the position of the second street L2 is particularly easily displaced. In this respect, in the present embodiment, the tape T is heated and contracted along the first street L1 immediately after the division, so that the pressing blade 34 presses against the second street L2 even if the size of the device chip DC is reduced. The position accuracy can be increased, and the pressure can be divided with high accuracy on the second street L2.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, direction, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  For example, the division starting point of the wafer W is not limited to the laser processing groove M described above, and various changes can be made. For example, the condensing point of the laser beam may be positioned inside the wafer W, and a modified layer serving as a division starting point may be formed along the streets L1 and L2 inside the wafer W by irradiation with the laser beam. The modified layer refers to a region where the density, refractive index, mechanical strength, and other physical characteristics inside the wafer W are different from the surroundings due to the irradiation of the laser beam, and the strength is lower than the surroundings. The modified layer is, for example, a melt treatment region, a crack region, a dielectric breakdown region, or a refractive index change region, and may be a region in which these are mixed.

  Furthermore, as the division starting point, a machining groove serving as the division starting point may be formed using a cutting device (dicer) or a scriber.

  Further, before performing the division starting point forming step, a water-soluble resin such as PVA (polyvinyl alcohol) or PEG (polyethylene glycol) is applied to the surface W1 of the wafer W, and a protective film is coated on the surface W1. The wafer W may be irradiated with a laser beam through the wafer W. By covering with the protective film in this way, even when debris is generated by irradiation with the laser beam, it is possible to prevent the debris from adhering to the surface W1.

  As described above, the present invention has an effect that a wafer can be accurately divided by pressing by a pressing means, and is useful for a wafer processing method for dividing various wafers into individual chips.

33 Support stand (support means)
34 Pressing blade (pressing means)
D device DC device chip (chip)
F frame (annular frame)
L1 1st street L2 2nd street M Laser processing groove (division starting point)
T tape U frame unit W wafer W1 surface (the other surface)
W2 Back side (one side)

Claims (1)

A plurality of devices are provided in each area defined by a plurality of first streets formed on the wafer surface extending in a first direction and a plurality of second streets extending in a second direction orthogonal to the first direction. A wafer processing method for dividing a provided wafer,
A frame unit forming step of attaching a tape that expresses shrinkage by heating at a predetermined temperature or more to one surface of the wafer, and attaching a peripheral unit of the tape to an annular frame to form a frame unit;
After performing the frame unit forming step, the wafer is processed along the first street and the second street of the wafer, and on the other side or inside of the wafer along the first street and the second street. A split starting point forming step for forming a split starting point;
After carrying out the division starting point forming step, the other surface side of the wafer of the frame unit is supported by a support means, and the wafer is pressed in the vertical direction by the pressing means over the tape along the division starting point, Dividing the wafer along the first street and then dividing along the second street,
When dividing along the first street in the dividing step, the pressing means heats and contracts the tape along the first street immediately after the division by the pressing means, and the adjacent chip on the first street. A wafer processing method characterized by maintaining an interval between them.

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