JP2005109322A - Laser beam dicing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam dicing device that is improved in applicability, such that the device can cope with various processes, such as the formation of a multilayered reformed layer in a wafer, the cutting of a die attaching tape, or the like. <P>SOLUTION: The laser head 20 of the laser beam dicing device 10 is provided with a plurality of laser oscillators 21 and 22, light-condensing means 23 and 23 which individually condense the oscillated laser light beams L1 and L2, and an optical path collecting means 24 which collects the laser light beams L1 and L2 to one optical axis. The laser beam dicing device is constituted to cope with various processes, such as the formation of a multilayered reformed area in a wafer, a composite process by which the formation of the reformed area in the wafer and the cutting of the die attaching tape DT are performed simultaneously, or the like, with the plurality of laser light beams L1 and L2 having converging points P1 and P2 at different positions on the same optical axis. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a dicing apparatus for manufacturing a chip such as a semiconductor device or an electronic component, and more particularly to a dicing apparatus using laser light.

  Conventionally, in order to divide a wafer having a semiconductor device or electronic component formed on its surface into individual chips, a dicing apparatus that uses a grindstone called a dicing blade to form a grinding groove in the wafer and cut the wafer is used. The dicing blade is obtained by electrodepositing fine diamond abrasive grains with Ni, and an extremely thin one having a thickness of about 30 μm is used.

  The dicing blade was rotated at a high speed of 30,000 to 60,000 rpm and cut into the wafer, and the wafer was completely cut (full cut) or incompletely cut (half cut or semi-full cut). Half-cut is a method of cutting about half of the thickness into a wafer, and semi-full cut is a method of forming a grinding groove leaving a thickness of about 10 μm.

  By the way, in the case of grinding with this dicing blade, since the wafer is a highly brittle material, it becomes brittle mode processing, and chipping occurs on the front and back surfaces of the wafer, and this chipping is a factor that degrades the performance of the divided chips. It was.

As a means to solve this chipping problem in the dicing process, instead of cutting with a conventional dicing blade, a laser beam having a focused point is incident on the inside of the wafer, and a modified region by multiphoton absorption is formed inside the wafer. Techniques relating to laser processing methods for forming and dividing into individual chips have been proposed (see, for example, Patent Documents 1 to 6).
JP 2002-192367 A JP 2002-192368 A JP 2002-192369 A JP 2002-192370 A JP 2002-192371 A JP 2002-205180 A

  However, the laser processing apparatuses proposed in the above Patent Documents 1 to 6 cleave the wafer by a single irradiation method using a single laser beam, and the chipping problem is solved. The applicability to processing was poor.

  For example, in the case of a thick wafer, when a plurality of modified layers are formed inside the wafer, there is a problem that it takes time because it is necessary to scan and irradiate the laser light a plurality of times.

  In addition, when die attach tape for die bonding is attached to the back side of the wafer, there is a problem that the wafer cannot be divided into individual chips unless the die attach tape is cut in a separate process. .

  The present invention has been made in view of such circumstances, and provides a laser dicing apparatus having a high degree of applicability that can be applied to various processes such as formation of a multilayer modified layer inside a wafer and cutting of a die attach tape. For the purpose.

  In order to achieve the above object, the present invention provides a laser dicing apparatus according to claim 1, wherein a laser beam is incident from the surface of a wafer to form a modified region inside the wafer, and the wafer is divided into individual chips. In the laser dicing apparatus that divides the laser beam, a laser head that irradiates laser light toward the wafer is provided, and the laser head includes a plurality of laser oscillators and a plurality of laser beams that individually oscillate. It has a condensing means and an optical path concentrating means for collecting the plurality of laser beams on one optical axis.

  According to the first aspect of the present invention, the laser head of the laser dicing apparatus is provided with a plurality of laser beams having condensing points at different positions on the same optical axis. In addition, it is possible to cope with various processes such as a composite process in which the modified layer formation inside the wafer and the die attach tape are cut simultaneously.

  According to a second aspect of the present invention, in the laser dicing apparatus according to the first aspect, a condensing point position adjusting unit that individually adjusts the position of the condensing point on the optical axis of the plurality of laser beams in the laser head. It is characterized by being provided.

  According to the invention of claim 2, since the positions of the condensing points on the optical axis of the plurality of laser beams can be individually adjusted, the respective laser beams can be condensed at effective points.

  According to a third aspect of the present invention, in the laser dicing apparatus according to the second aspect, the condensing point position adjusting unit is a driving unit that finely moves the plurality of condensing units on respective optical axes. It is said.

  According to a fourth aspect of the present invention, in the laser dicing apparatus according to the third aspect, the driving means includes at least one piezoelectric element.

  According to invention of Claim 3 and Claim 4, the position of a condensing point can be easily adjusted with a simple structure.

  According to a fifth aspect of the present invention, in the laser dicing apparatus according to any one of the first, second, third, and fourth aspects, the plurality of laser beams are the same type of laser beams. .

  According to the invention of claim 5, it is possible to easily form a multilayer modified layer inside the wafer at the same time.

  According to a sixth aspect of the present invention, in the laser dicing apparatus according to any one of the first, second, third, or fourth aspect, at least one of the plurality of laser beams is another laser beam. Is characterized by being a different kind of laser light.

  According to the sixth aspect of the present invention, different types of processing can be performed simultaneously with each of a plurality of laser beams.

  As described above, the laser dicing apparatus of the present invention has a plurality of laser oscillators, collects a plurality of laser lights on one optical axis by the optical path concentrating means, and individually collects a plurality of laser lights by the plurality of condensing means. Therefore, it is possible to cope with various processes such as the formation of a multilayered modified layer inside the wafer, and the combined process of simultaneously forming the modified layer inside the wafer and cutting the die attach tape.

  In addition, the position of the condensing point on the optical axis of a plurality of laser beams can be individually adjusted, and the same type or different types of laser beams can be used for a plurality of laser beams, so that a wide range of processing is possible. Also, can respond easily.

  The preferred embodiments of the laser dicing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. In each figure, the same number or symbol is attached to the same member.

  FIG. 1 is a schematic configuration diagram of a laser dicing apparatus according to the present invention. In the laser dicing apparatus 10, as shown in FIG. 5, the wafer is affixed to a dicing sheet S having an adhesive material on one side, and is carried in a state integrated with the frame F via the dicing sheet S. It is conveyed in the dicing apparatus 10.

  As shown in FIG. 1, the laser dicing apparatus 10 includes a wafer moving unit 11, a laser head 20, a control unit (not shown), and the like.

  The wafer moving unit 11 is mounted on the frame F via the dicing sheet S attached to the XY table 12 provided on the main body base 16 of the laser dicing apparatus 10, the Zθ table 15 mounted on the XY table 12, and the Zθ table 15. A suction stage 13 for sucking and holding the wafer W, a frame chuck 14 attached to the Zθ table 15 for sucking and holding the frame F, and the like.

  The wafer moving unit 11 precisely moves the wafer W in the XYZθ direction of the drawing while being mounted on the frame F via the dicing sheet S.

  The laser head 20 minutely moves two laser oscillators 21 and 22 that oscillate laser beams L1 and L2, condenser lenses (condensing means) 23 and 23, and condenser lenses 23 and 23 on respective optical axes. Driving means (condensing point position adjusting means) 26, 26, half-mirror 24A and mirror 24B constituting an optical path converging means 24 for collecting the optical axes of the laser beams L1 and L2, and an objective lens 25, etc. ing.

  In the laser head 20, the laser light L 1 oscillated from the laser oscillator 21 is condensed inside the wafer W through an optical system such as a condenser lens 23, a half mirror 24 A, and an objective lens 25.

  The laser beam L2 oscillated from the laser oscillator 22 is matched with the optical axis of the laser beam L1 via the condenser lens 23, the mirror 24B, and the half mirror 24A, and then the same as the laser beam L1 via the objective lens 25. The light is condensed inside the wafer W on the optical axis.

  The positions on the optical axis of the condensing point P1 of the laser beam L1 and the condensing point P2 of the laser beam L2 are independently adjusted by moving the condensing lens 23 minutely on the optical axis by the driving means 26, respectively. The

The laser beams L1 and L2 oscillated from the laser oscillators 21 and 22 are, for example, conditions in which the peak power density at the condensing points P1 and P2 is 1 × 10 ⁸ (W / cm ² ) or more and the pulse width is 1 μs or less. Thus, a laser beam having transparency to the dicing sheet is used.

  The reason why laser light having transparency with respect to the dicing sheet is used is that, for example, it is possible to cope with modifications such as when laser light is irradiated from the back side of the wafer W.

  In addition, the laser dicing apparatus 10 includes a wafer cassette elevator (not shown), a wafer transfer means, an operation plate, an indicator lamp, and the like.

  The wafer cassette elevator moves a cassette in which wafers are stored up and down to position it at a transfer position. The transfer means transfers the wafer between the cassette and the suction stage 13.

  On the operation plate, switches for operating each part of the laser dicing apparatus 10 and a display device are attached. The indicator lamp displays an operation status such as processing end or emergency stop during processing of the laser dicing apparatus 10.

  FIG. 2 is a conceptual diagram for explaining the details of the driving means 26 for moving the condenser lens 23 minutely on the optical axis. The driving means 26 includes a lens frame 26A that holds the condenser lens 23, a piezoelectric element 26B that is attached to the upper surface of the lens frame 26A and moves the lens frame 26A minutely in the optical axis direction.

  The piezoelectric element 26B that expands and contracts by applying a voltage has a hollow cylindrical shape, the upper end of which is fixed to the laser head main body 20A, and the lower end is joined to a lens frame 26A that holds the condenser lens 23. The condensing lenses 23 and 23 are finely fed in the optical axis direction by the expansion and contraction of the piezoelectric element so that the positions of the condensing points P1 and P2 of the laser beams L1 and L2 are independently and precisely positioned. It has become.

  FIG. 3 is a conceptual diagram illustrating a modified region formed in the vicinity of a condensing point inside the wafer. As shown in FIG. 3, when the wafer W is processed and fed in the direction of the white arrow in the figure, the modified region R1 is formed at the condensing point P1 by the laser light L1 incident inside the wafer W, and the laser A modified region R2 is formed at the condensing point P2 of the light L2, and two upper and lower modified regions are simultaneously formed inside the wafer.

  As described above, the upper and lower two modified regions R1 and R2 are formed inside the wafer W, so that even if the thickness is large, the modified regions R1 and R2 are used as a starting point, or a slight external force is applied. Is cut along the modified regions R1 and R2. In this case, the wafer W is easily divided into chips without causing chipping on the front and back surfaces.

  Further, as shown in FIG. 5, since the dicing sheet S is attached to the back surface of the wafer W and mounted on the dicing frame F, the wafer W is separated into individual chips even if divided into individual chips. Never become.

  Some types of wafer W have a metal film such as Au formed on the back surface. In the case of such a product type, the wafer W cannot be cleaved satisfactorily only by forming the modified layer on the wafer base material.

  When dicing such a wafer W, a laser suitable for forming a modified region on the wafer base is used for the laser beam L1, and suitable for melting the metal film on the back surface of the wafer for the laser beam L2. The modified region is formed inside the wafer with the laser beam L1, and the metal film on the back surface of the wafer is melted with the laser beam L2.

  Some wafers W have a die attach tape attached to the back surface used in the die bonding step prior to the dicing step. FIG. 4 is a conceptual diagram showing a state where such a wafer W is subjected to laser dicing.

  As shown in FIG. 4, the wafer W has a die attach tape DТ attached to the back surface, and the die attach tape DТ is attached to the dicing sheet S and mounted on the frame F. In the dicing process, the wafer W must be cut and the die attach tape DТ must be cut.

  In this case, a laser suitable for forming a modified layer on the wafer substrate is used for the laser beam L1, and a laser suitable for melting the die attach tape DТ attached to the back surface of the wafer is used for the laser beam L2. The modified layer is formed inside the wafer with the laser beam L1, and at the same time, the die attach tape DТ on the back surface of the wafer is melted with the laser beam L2.

  Next, the operation of the laser dicing apparatus 10 according to the present invention will be described using an example in which two layers of modified regions R1 and R2 are formed inside the wafer W. When dicing, the wafer W initially placed on the suction stage 13 is photographed with a circuit pattern and an alignment mark on the surface by a CCD camera (not shown) and aligned by an alignment means having an image processing apparatus.

  Next, laser beams L1 and L2 are emitted from the laser oscillators 21 and 22, respectively. The laser light L1 is applied to the upper surface of the wafer W via an optical system such as a condenser lens 23, a half mirror 24A, and an objective lens 25, and the laser light L2 is emitted to the condenser lens 23, the mirror 24B, the half mirror 24A, and the objective lens. The top surface of the wafer W is irradiated through an optical system such as 25.

  The positions of the condensing points P1 and P2 of the irradiated laser beams L1 and L2 in the Z direction are accurately adjusted independently to predetermined positions inside the wafer by adjusting the positions of the respective condensing lenses 23 by the driving means 26. Is set.

  In this state, the XY table 12 is processed and fed in the X direction which is the dicing direction. As a result, two lines of modified regions R1 and R2 by multiphoton absorption are simultaneously formed in the wafer.

  When one line of laser dicing is performed, the XY table 12 is indexed and fed by one pitch in the Y direction, and the next line is similarly laser-diced.

  When all the lines are laser-diced, the Zθ table 15 is rotated 90 °, and all the lines orthogonal to the previous line are also laser-diced, and the wafer W is divided into individual chips to form one wafer W. Laser dicing is completed.

  As described above, since the two modified regions R1 and R2 are simultaneously formed inside the wafer W by the laser beams L1 and L2, even the thick wafer W is stably cleaved and chipped in a short time. High-quality dicing that hardly occurs is performed.

  In the above-described embodiment, the piezoelectric element 26B is used as the driving unit 26 of the condenser lens 23. However, the present invention is not limited to this, and other known linear actuators can be used.

  Further, although the mirror 24B and the half mirror 24A are used as the optical path converging means 24 for collecting the plurality of laser beams L1 and L2 on one optical axis, the optical path of the plurality of laser beams is set to 1 by using other optical members such as a prism. You may make it collect on one optical axis.

Schematic configuration diagram of a laser dicing apparatus according to the present invention Sectional drawing showing the structure of the drive means of a condensing lens Conceptual diagram showing a state in which a two-layer modified region is formed inside the wafer Conceptual diagram when dicing a wafer with die attach tape Perspective view showing wafer mounted on frame

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Laser dicing apparatus, 20 ... Laser head, 21, 22 ... Laser oscillator, 23 ... Condensing lens (condensing means), 24 ... Optical path condensing means, 26 ... Driving means (condensing point position adjusting means), 26B ... Piezoelectric element, F ... frame, L1, L2 ... laser beam, P1, P2 ... condensing point, R1, R2 ... modified region, S ... dicing sheet, W ... wafer

Claims (6)

In a laser dicing apparatus that enters a laser beam from the surface of a wafer to form a modified region inside the wafer, and divides the wafer into individual chips,
A laser head for irradiating a laser beam toward the wafer is provided,
The laser head
Multiple laser oscillators,
A plurality of condensing means for individually condensing the oscillated laser beams;
An optical path condensing unit that collects the plurality of laser beams on one optical axis.   2. The laser according to claim 1, wherein the laser head is provided with a condensing point position adjusting means for individually adjusting a condensing point position on an optical axis of the plurality of laser beams. Dicing equipment.   The laser dicing apparatus according to claim 2, wherein the condensing point position adjusting unit is a driving unit that minutely moves the plurality of condensing units on respective optical axes.   The laser dicing apparatus according to claim 3, wherein the driving unit includes at least one piezoelectric element.   The laser dicing apparatus according to any one of claims 1, 2, 3, and 4, wherein the plurality of laser beams are the same type of laser beams.   5. The laser dicing apparatus according to claim 1, wherein at least one of the plurality of laser beams is a laser beam different from other laser beams.

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