JP5504021B2 - Laser processing method - Google Patents

Description

  The present invention relates to a method of performing laser processing by irradiating a workpiece held on a chuck table with a laser beam.

  When various workpieces (workpieces) are divided into individual chips, a dicing tape formed of polyolefin or the like is formed on the back surface of the work to facilitate handling of the workpieces divided into individual chips. Affixed. The wafer to which the dicing tape is adhered in this way is held with the dicing tape side down on the chuck table (holding means) of the laser processing apparatus. Then, a laser beam is irradiated from the front surface side (upper surface side) of the wafer, and a laser processing groove is formed along a predetermined division line formed on the wafer. In this way, when the laser processing groove formed on the wafer reaches the back surface (lower surface) of the wafer, the laser beam penetrating the work passes through the dicing tape and reaches the holding member constituting the chuck table.

  Further, before cutting the street of the semiconductor wafer having the low-k film, in order to avoid circuit damage due to peeling of the low-k film at the time of cutting, a laser beam is applied to the low-k film formed on the street. When the low-k film is removed by irradiation, the chuck table is moved in the processing feed direction while irradiating a laser beam while the semiconductor wafer is held on the chuck table. In this case, it is not necessary to make the laser beam reach the back surface side of the semiconductor wafer, but in order to remove the Low-k film with certainty, it is necessary to irradiate the laser beam beyond the outer peripheral edge of the semiconductor wafer. This laser beam passes through the dicing tape attached to the back surface of the semiconductor wafer and reaches the holding member of the chuck table.

  The holding member that constitutes the chuck table is made of porous ceramics or metal material. When the laser beam reaches the upper surface, it absorbs the laser beam and generates heat. The heat causes the dicing tape to melt and damage it. There is a problem of making it.

  Also, a part of the melted dicing tape adheres to the holding member of the chuck table, contaminates the chuck table, or the work is carried out of the chuck table due to the adhering of the part of the dicing tape to the holding member. There is a problem of not being able to. Therefore, the present applicant has proposed a chuck table made of quartz glass in order to solve these problems (see Patent Document 1).

JP 2006-205187 A

  However, although the degree of breakage of the chuck table has been improved by the invention described in Patent Document 1, the chuck table is gradually deteriorated by irradiating the laser beam many times and absorbs the laser beam to generate heat. There is a problem that there is.

  The present invention has been made in view of these facts, and its main technical problem is to perform replacement and maintenance of the chuck table for a longer period of time even when the laser beam reaches the chuck table. It is an object of the present invention to provide a laser processing method capable of processing without any problem.

  The present invention uses a processing apparatus having a holding unit having a holding surface for holding a workpiece having a planned division line and a processing unit for irradiating a laser beam onto the planned division line of the workpiece held by the holding unit. This is related to a laser processing method that applies laser processing to a plurality of workpieces, and places the workpiece on the holding surface and holds it along the planned division line of the workpiece held on the holding surface by the processing means. In the placement process, the workpiece placement position is changed to the workpiece placement position in the previous placement process. The laser beam that overruns the workpiece in the machining process and the laser beam that penetrates the workpiece in the machining process To avoid laser beam is irradiated to the same position and location irradiated.

  In the mounting process, the mounting position of the work is shifted from the mounting position of the work in the previous mounting process, and the laser beam that overruns the work in the processing process and the laser beam that penetrates the work are In the past, the laser beam was not irradiated to the same spot where the laser beam was irradiated in the past, so that the spot deteriorates due to repeated irradiation of the laser beam to the same spot of the holding means, or the laser beam absorbs and generates heat Nothing will happen. Therefore, laser processing can be performed without replacing or maintaining the holding means over a long period of time.

It is a perspective view which shows an example of a laser processing apparatus. It is a top view which shows the overrun of the laser beam at the time of a workpiece | work processing. It is sectional drawing which shows the state in which a laser beam reaches a holding surface at the time of a workpiece | work processing. It is a top view which shows the 1st example of a mounting process. It is a top view which shows the 2nd example of a mounting process.

  A laser processing apparatus 1 shown in FIG. 1 is an apparatus for processing a workpiece W by irradiating a workpiece (workpiece) W held by a holding unit 2 with a laser beam from a processing unit 3. The holding means 2 is configured to be fed by the feed mechanism 4 in the X-axis direction and the Y-axis direction that is horizontally orthogonal to the X-axis direction. The feed mechanism 4 includes an X-direction feed mechanism 5 and a Y-direction feed mechanism 6.

  The holding means 2 includes a holding surface 20 on which the work W is placed and sucked, and a plurality of clamps that are arranged on the outer peripheral side of the holding surface 20 and fix the frame F integrated with the work W via the dicing tape T. 21. The clamp part 21 includes a pressing part 210 that rotates a predetermined angle around a horizontal rotation axis.

  The processing means 3 is fixed to a wall 10 provided at the rear end of the apparatus, and includes an irradiation head 30 that irradiates a laser beam downward.

  The X-direction feed mechanism 5 includes a ball screw 50 extending in the X-axis direction, a guide rail 51 disposed in parallel with the ball screw 50, a motor 52 connected to one end of the ball screw 50, and rotating at the lower portion thereof as a guide. The slide plate 53 includes a nut (not shown) that is in sliding contact with the rail 51 and screwed into the ball screw 50. The slide plate 53 is guided by the guide rail 51 and moves in the X-axis direction as the ball screw 50 rotates. It is the composition to do. A rotation drive unit 54 having a pulse motor is fixed inside the slide plate 53, and the rotation drive unit 54 can rotate the holding means 2 by a predetermined angle.

  The Y-direction feed mechanism 6 includes a ball screw 60 extending in the Y-axis direction, a guide rail 61 disposed in parallel to the ball screw 60, a motor 62 connected to one end of the ball screw 60 and rotating the ball screw 60, and a lower portion serving as a guide. The slide plate 63 includes a nut (not shown) that is in sliding contact with the rail 61 and screwed into the ball screw 60. The slide plate 63 is guided by the guide rail 61 and moves in the X-axis direction as the ball screw 60 rotates. It is the composition to do. The slide plate 63 is provided with an X-direction feed mechanism 5, and the X-direction feed mechanism 5 is also moved in the same direction as the slide plate 63 moves in the Y-axis direction.

Next, the case where the workpiece | work W shown in FIG. 1 is laser-processed using the laser processing apparatus 1 comprised in this way is demonstrated. The workpiece is not particularly limited. For example, semiconductor wafers such as silicon wafers and gallium arsenide, adhesive members such as DAF (Die Attach Film) provided on the back surface of the wafer for chip mounting, semiconductor product packages, ceramics, Examples thereof include glass, sapphire (Al ₂ O ₃ ) -based inorganic material substrates, various electronic components such as LCD drivers, and various processing materials that require processing position accuracy on the order of microns.

  On the surface W <b> 1 of the work W, division planned lines S are formed vertically and horizontally. The back surface of the workpiece W is attached to the dicing tape T. A ring-shaped frame F is attached to the peripheral edge of the dicing tape T, and the work W is integrated with and supported by the frame F via the dicing tape T. Although the workpiece W, the dicing tape T, and the frame F in FIG. 1 are illustrated in an enlarged manner, they are actually large enough to be held by the holding means 2.

  The workpiece W supported by the frame F via the dicing tape T is placed on the holding surface 20 on the dicing tape T side, and the workpiece W is sucked and held on the holding surface 20 via the dicing tape T (placement). Process). At this time, as shown in FIG. 2, the frame F is fixed at the clamp portion 21 by being pressed from above by the pressing portion 210. Here, the workpiece W is placed and held at the center of the holding surface 20.

  When the workpiece W is held by the holding means 2 together with the dicing tape T and the frame F in this way, the irradiation head while the X direction feeding mechanism 5 and the Y direction feeding mechanism 6 feed the holding table 2 in the X direction and the Y direction. When the laser beam 30 irradiates the division line S with the laser beam, the laser processing is performed along the division line S. Laser processing is performed on all the division lines S. Such laser processing includes full-cut processing in which the laser beam reaches the back surface side of the workpiece W, modified layer formation processing for forming a modified layer inside the workpiece, and an ablation groove on the surface of the workpiece W. There are an ablation process to be formed, a Low-k film removal process for removing the Low-k film formed on the planned division line S (processing step), and the like. The modified layer is a starting point when cutting by applying external force later, and the density, refractive index, mechanical strength and other physical characteristics are different from the surroundings. For example, there are a melt treatment region, a crack region, a dielectric breakdown region, a refractive index change region, and the like, and there are regions where these are mixed.

  In the processing step, the laser beam is irradiated along the scheduled division line S, and the laser beam is overrun to the overrun position 7 as shown in an enlarged manner in FIG. In this case, the laser beam is directly applied to the dicing tape T and may pass through the dicing tape T and damage the holding surface 20 immediately below the overrun position 7. Even if quartz glass is used as the holding surface 20, damage to the holding surface 20 cannot be completely avoided if the same portion is repeatedly irradiated with a laser beam.

  Further, as shown in FIG. 3, in the full-cut processing in which the laser beam is cut so as to reach the back surface side W2 of the workpiece W, the laser beam L condensed on the back surface W2 of the workpiece W passes through the dicing tape T. As a result, the holding surface 20 is also reached. Therefore, the holding surface 20 may be damaged even at a position below the workpiece W.

  The workpiece W that has finished the machining process is released from the holding surface 20 after being released from the holding surface 20. The frame F is also released from the holding means 2 together with the workpiece W by being released from being pressed by the pressing portion 210 of the clamp portion 21 (detaching step).

  The mounting process, the processing process, and the removal process performed as described above may be performed in a fully automatic manner by a control unit (not shown) in the laser processing apparatus 1 or may be performed manually by an operator. You can also.

  When laser processing a plurality of workpieces, the placing process, the processing process, and the removing process are repeated a plurality of times as described above. Thus, while repeating each process sequentially, in the placing process, the work is not placed at a fixed position of the holding means 2 at the time of processing the work each time, but the previous work (for the previous work) is placed. In the placing step, the work is placed at a position shifted from the position where the work is placed on the holding means 2. The next workpiece is also placed and processed at a position different from the previous time. And by adopting such a mounting method, the laser beam overrunning the workpiece or the laser beam penetrating the workpiece is placed at the same location on the holding surface 20 of the holding means 2 that has already been irradiated with the laser beam. Prevents irradiation. There is no particular limitation on how to shift the work placement position, but a placement example is shown below. In addition, the work of shifting the workpiece in the placement process may be automatically performed by the processing apparatus, or may be manually performed by the operator.

(First example)
As shown in FIG. 4, if the previous workpiece is placed at the first placement position 80 (indicated by a two-dot chain line) that is the center of the holding means 2, When the laser beam is applied to the previous division planned line S of the workpiece while feeding the holding means 2 in the X-axis direction in the state of being placed at the first placement position 80, the laser beam is all of the planned division lines S. From the dicing tape T at the first overrun position (indicated by a two-dot chain line) shown in FIG. As a result, the holding surface 20 may be damaged below the first overrun position 70.

  Therefore, the workpiece to be machined next is placed at a second placement position 81 (shown by a solid line) that is slightly shifted in the Y-axis direction from the first placement position 80. Specifically, the workpiece W integrated with the frame F via the dicing tape T is placed on the holding means 2 while being shifted in the Y-axis direction (vertical direction in the example of FIG. 4) as a whole and held. While sucking the workpiece W through the dicing tape T on the surface 20, the pressing portion 210 is pressed against the frame F from above and fixed. In order to place the workpiece W integrated with the frame F automatically through the dicing tape T by the processing device in a state shifted from the first placement position 80, for example, the standby position of the holding means 2 is changed to the previous time. The workpiece may be moved slightly in the Y-axis direction from the standby position of the holding means 2 when the workpiece is placed at the first placement position, and the next workpiece may be placed at that position. In this case, since the workpiece W, the dicing tape T, and the frame F are displaced in the Y-axis direction as a whole, the position of the frame F held in the clamp portion 21 is also shifted in the Y-axis direction from the previous position indicated by the two-dot chain line. .

  Then, when a laser beam is irradiated onto the planned dividing line while overrunning in this state, the laser beam passes through the dicing tape T and reaches the holding surface 20 at the second overrun position shown in FIG. . Then, the holding surface 20 may be damaged at the second overrun position 71. However, the second overrun position 71 is a position different from the first overrun position 70, and the laser beam has been irradiated in the past. Since it is not the position where it was made, it can prevent that the holding surface 20 damages and deteriorates. For the workpiece to be processed next, if the workpiece is placed at a position different from the previous time, the first overrun position will be overrun at a position different from the second overrun position. Heat generation, damage, and deterioration of the holding surface 20 can be prevented. When the apparatus operates in full auto mode, the control unit in the apparatus may slightly shift the workpiece transfer position with respect to the holding means 2 each time. The actual shift amount may be controlled in consideration of the interval between the lines to be divided, the length of the overrun portion, and the like. Thus, if the mounting position of the workpiece W with respect to the holding means 2 is successively shifted in the Y-axis direction, the overrun laser beam concentrated on a specific portion of the holding surface 20 is not irradiated.

(Second example)
As in the first example, if the previously machined workpiece is placed at the first placement position 82 (indicated by a two-dot chain line) that is the center of the holding means 2, When the laser beam is applied to the previous division line S of the workpiece while feeding the holding means 2 in the X-axis direction while the holder is placed at the first placement position 82, the laser beam is moved to the first placement position 82. There is a risk that the holding surface 20 may be damaged below the first overrun position 72 formed around the position 82.

  Therefore, the workpiece to be machined next is placed at a second placement position 83 (shown by a solid line) slightly rotated from the first placement position 82. Specifically, the holding means 2 in a state in which the workpiece W integrated with the frame F via the dicing tape T is rotated and shifted counterclockwise or clockwise (clockwise in the example of FIG. 5) as a whole. The workpiece W is sucked on the holding surface 20 via the dicing tape T, and in this state, the pressing portion 210 is pressed against the frame F from above and fixed. At this time, when the orientation flat 9 is formed on the workpiece W as in the example shown in FIG. 5, the orientation of the orientation flat 9 is different from the first placement position. In order to place the workpiece W integrated with the frame F automatically through the dicing tape T by the processing device in a state shifted from the first placement position 82, for example, the standby position of the holding means 2 is changed to the previous time. It is sufficient that the workpiece is set at a position slightly rotated from the standby position of the holding means 2 when the workpiece is placed at the first placement position, and the next workpiece is placed at that position. The actual amount of rotation may be controlled in consideration of the interval between the lines to be divided, the length of the overrun portion, and the like.

  Then, when the laser beam is irradiated to the planned dividing line while overrunning in this state, the first overrun position 72 and the second overrun position 73 are as shown in FIG. The laser beam reaches the holding surface 20 through the dicing tape T at a position different from the first overrun position 72 at a different position and angle. Therefore, since the laser beam that has repeatedly overrun and the laser beam that penetrates the workpiece are not irradiated to the same location, the holding surface 20 can be prevented from being heated, damaged, or deteriorated. In FIG. 5, the second overrun position 73 is shown only in the enlarged view, but actually, the same number of overruns as the first overrun position 72 are performed. Further, although the illustration of the dicing tape T and the frame F is omitted in FIG. 5, these are also rotated and placed together with the workpiece W.

  The workpiece to be processed next is further rotated and placed at a position different from the previous time and irradiated with a laser beam, so that the first overrun position and the second overrun position are different. Overrun occurs, and heat generation, damage, and deterioration of the holding surface 20 can be prevented.

1: Laser processing device 2: Holding table 3: Laser irradiation mechanism 30: Irradiation head 4: Feed mechanism 5: X direction feed mechanism 50: Ball screw 51: Guide rail 52: Motor 53: Slide plate 54: Rotation drive unit 6: Y Direction feed mechanism 60: Ball screw 61: Guide rail 62: Motor 63: Slide plate 7: Overrun position 70, 72: First overrun position 71, 73: Second overrun position 80, 82: First mounting Placement position 81, 83: Second placement position 9: Orientation flat

Claims (1)

Holding means having a holding surface for holding a workpiece having a division planned line;
Processing means for irradiating a laser beam onto a work division scheduled line held by the holding means and processing the workpiece;
A laser processing method for performing laser processing on a plurality of workpieces using a processing apparatus having
A placing step of placing and holding the workpiece on the holding surface;
A machining step for machining along the division line of the workpiece held on the holding surface by the machining means;
In the process of removing the workpiece that has been processed from the holding surface and repeating the removal process several times,
In the placement step, the workpiece placement position is shifted from the workpiece placement position in the previous placement step, so that the laser beam that overruns the workpiece in the machining step and the laser beam that penetrates the workpiece are A laser processing method that includes a workpiece shifting step that avoids irradiating the same spot that has been irradiated with a laser beam.

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