X & Y ORTHOGONAL CUT DIRECTION PROCESSING WITH SET

BEAM SEPARATION USING 45 DEGREE BEAM SPLIT

ORIENTATION APPARATUS AND METHOD

FIELD OF THE INVENTION

[0001] This invention relates to the processing of semiconductor wafers.

More particularly, the invention relates to an apparatus and method for scribing a pair of parallel cuts on a planar workpiece using a first beam and a second beam, each having an impact point on the workpiece, where the first and second impact points are positioned diagonally with respect to X and Y axes defined by the workpiece.

BACKGROUND

[0002] In the microelectronics industry, sheets of semiconductor materials are typically sawed into individual wafers using dicing saws. With dicing saws, there are several possible concerns including thermally and/or mechanically- induced cracking and or adhesion loss between adjacent layers, poor mechanical strength, moisture absorption and/or time-dependent behavior due to the use of coolant, texture effects, and poor thermal conductivity. Of these possible concerns, thermally and/or mechanically induced cracking and/or adhesion loss and moisture absorption are significant. Large tensile and shear stresses are imparted at the cut zone which can lead to cracking and/or adhesion loss leading to delamination between adjacent layers. Further, the use of coolant during sawing can lead to moisture absorption and time-dependant behavior. [0003] One approach to reduce potential problems with mechanically induced delamination is to reduce saw speed. However, this reduces throughput

and productivity. In addition, the potential problems relating to moisture absorption still remain.

[0004] Another approach is to cut or scribe a trench wider than the saw in the areas to be sawed using a laser device generating a single beam. The beam scribes through low dielectric constant (low-k) and metal layers, for example, and stops at the silicon. Following the laser scribing, the saw is used to cut through the silicon and singulate the wafers. The area removed by the laser acts as a crack stop and ensures that these cracks do not propagate into the wafer, and potentially affect the electrical performance of a finished integrated circuit contained on the wafer. The disadvantage of using a single laser beam is the requirement of cutting a fairly wide trench in the low-k and metal layers.

[0005] Still another approach is to scribe using a laser device generating at least two beams to make two trenches, one on each side of the area to be sawed. This eliminates the potential problem of cutting a wide trench. The operation of such a system is generally shown in Figure 6. Fig. 6 illustrates a planar workpiece 200. A pair or laser beams impact workpiece 200 at impact points 202 and 204. Impact points 202 and 204 are orthogonal to an X-axis 206 of the workpiece 200. A pair of parallel trenches may be scribed on the workpiece 200 bye either moving the workpiece 200 or the laser beams along X-axis 206. [0006] However, using two or more beams to cut parallel trenches requires additional processing time to reorient the workpiece 200 and/or the impact points 202, 204 if it is desired to scribe parallel trenches along a Y-axis 208. Such reorientation increases processing time.

SUMMARY

[0007] An X & Y orthogonal cut apparatus for scribing a pair of parallel cuts on a planar workpiece when the planar workpiece is oriented with an X-axis and a Y-axis. The apparatus includes a laser device generating at least two beams including a first beam and a second beam. The first beam and the second beam impacting the workpiece first and second impact points. The first and second impact points are positioned diagonally with respect to the X and Y axes of the workpiece. At least one actuator moves either the laser device or the workpiece to scribe parallel cuts on the workpiece.

DESCRIPTION OF THE DRAWING

[0008] The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:

[0009] Figure 1 is a schematic perspective view of an X & Y orthogonal cut apparatus according to an embodiment as disclosed herein; [0010] Figure 2 is a simplified plan view of a workpiece showing a pair of laser impact points on on the workpiece as disclosed herein; [0011] Figure 3 is a simplified plan view of a workpiece showing parallel scribed cuts on the workpiece;

[0012] Figure 4 is a simplified perspective view of a configuration of an X

& Y orthogonal cut apparatus having a laser device associated with an actuator as disclosed herein;

[0013] Figure 5 is block diagram of a process which can be carried out using the apparatus of Fig. 1 ; and

[0014] Figure 6 is a simplified plan view of a workpiece showing beam positioning on the workpiece according to the prior art.

DESCRIPTION

[0015] An X & Y orthogonal cut apparatus 10 is illustrated in Fig. 1. The apparatus 10 is used for scribing a pair of parallel cuts 12, 14 on a planar workpiece 200. In a preferred embodiment, the planar workpiece 200 is a semiconductor wafer. The planar workpiece 200 is oriented along an X-axis 20 and a Y-axis 22. As shown, the planar workpiece 200 may be positioned on a stage 23. The apparatus 10 includes a laser device 24 generating at least two . beams including a first beam 26 and a second beam 28. The first and second beams 26 and 28 may pass through positioning optics 29 to direct the laser beams 26 and 28 to the workpiece 200. The first beam 26 and the second beam 28 each have an impact point 30, 32, respectively, on the planar workpiece 200, with the first and second impact points 30, 32 being positioned diagonally with respect to the X and Y axes 20, 22 of the planar workpiece 200. In the preferred embodiment, the apparatus 10 also includes a first actuator 34 to move the stage 23 and thus the planar workpiece 200 relative to the X-axis 20. When the planar workpiece 200 is moved along the X-axis 20 a pair of parallel cuts will be made in the direction of the X-axis 20. The preferred embodiment also includes a second actuator 36 to move the planar workpiece 200 relative to the Y-axis 22. [0016] The laser device 24 includes a laser 38. Preferably, the laser 38 is a diode-pumped laser and is capable of high-speed focusing and/or high- resolution focusing. The output of the laser 38 passes through optics 40 that divide the output of the laser 38 into first beam 26 and second beam 28. First and second beams 26 and 28 are redirected onto the planar workpiece 200 by the

positioning optics 29 to impact on planar workpiece 200 at impact points 30, 32. The optics 40 and the positioning optics 29 may each include, for example, one or more lens and/or mirror.

[0017] . The laser device 24 includes a first shutter 42 to control the first beam 26 and a second shutter 44 to control the second beam 28. The laser device 24 also includes a controller 46 to operate the shutters 42 and 44. Preferably the shutters 42 and 44 are positioned at laser device 24 but it is understood that shutters may be positioned at positioning optics 29.

[0018] . With reference to Fig. 3,. through operation of.the shutters 42 and

44 alignment of a first end 46 of the cut 12 made by the first beam 26 with a first end 48 of the cut 14 made by the second beam 28 and/or,a second end 50 of the cut 12 made by the first beam 26 with a second end 52 of the cut 14 made by the second beam 28 relative to the X-axis 20, the Y-axis 22, and/or an edge 54 of the planar workpiece 200 is performed as illustrated in Figs. 1 and 3. By control of the shutters 42 and 44 the cuts 12, 14 can thus be made to start or end at a desired or required position relative to the X-axis 20, the Y-axis 22, or the workpiece edge 54. ^•

[0019] As seen in Fig. 2, the positioning optics 29 positions the first impact point 30 diagonally at a forty-five (45) degree angle 60 relative to the second impact point 32 with respect to the X and Y axes 20, 22 of the planar workpiece 200. The result is that a separation 62 along the X-axis 20 of the impact points 20, 26 is generally equal to a separation 64 along the Y-axis 22. [0020] Because the X-axis separation 62 is generally equal to the Y-axis separation 64, generally parallel cuts 12, 14 having generally equal separation can be made along the X-axis 20 and/or the Y-axis 22 without having to reorient the

planar workpiece 200, laser beams 26, 28, optics 40, and/or positioning optics 29. Saw cutting zones 66 (shaded) are thus defined by the cuts 12, 14 as shown in Fig. 3.

[0021] In the example of Fig. 1, the first actuator 34 moves stage 23 along

Y-axis 22 to scribe parallel cuts along Y-axis 22. The second actuator 36 moves positioning optics 29 along the X-axis 20 to scribe parallel cuts along X-axis 20. It is contemplated herein that actuators 34, 36 are driven by a motor that may be a linear motor, a brushless linear motor, a galvanometer, a moving magnet galvanometer, any such suitable actuation mechanism, or any combination thereof.

[0022] A second preferred configuration of an X & Y orthogonal cut apparatus 1OA is seen in Fig. 4. In the second preferred embodiment, a laser device 24A is mounted to actuator 36A. In this configuration, actuator 36A moves the entire laser device 24A in addition to the positioning optics 29A. [0023] Looking now to Fig. 5, a process is illustrated for X & Y orthogonal cut direction processing using apparatus 10 of Fig. 1. The process includes directing the first beam and the second beam to impact the workpiece at a first and a second impact point, the first and second impact points being positioned diagonally with respect to the X and Y axes of the workpiece at step 100. Moving the first beam 26 and the second beam 28 relative to the planar workpiece 200 and/or the planar workpiece 200 relative to the first beam 26 and the second beam 28 occurs at step 100. At step 104 the cut 12 of the first beam 14 is controlled. At step 106 the cut 14 of the second beam is controlled. [0024] According to this example, step 104 includes aligning the first end

beam 28 and/or aligning the second end 50 of cut 12 of the first beam 26 relative to the second end 52 of the cut 14 of the second beam 28. Further according to this example, step 106 includes aligning the first end 48 of cut 14 relative to the first end 46 of cut 12 and/or aligning the second end 50 of cut 14 relative to the second end 48 of cut 12.

[0025] . If the answer in step 108 is that additional cuts 12, 14 are desired or required, the process repeats back to step 100. If additional cuts 12, 14 are not desired or required, the process ends at step 110.

[0026] While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.