JP2014067843A - Laser processing device and protective film coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an economical protective film coating device capable of suppressing an amount of protective film liquid to be discarded, a laser processing device with the protective film coating device, and a protective film coating method.SOLUTION: A laser processing device comprises: a processing table which holds a workpiece; laser processing means for performing laser processing for the workpiece held on the processing table; a cassette mounting stand on which a cassette which can accommodate a plurality of workpieces is mounted; and transportation means for transporting a workpiece from the cassette mounted on the cassette mounting stand to at least the processing table. This device further comprises: a holding table having a holding surface on which a workpiece is held; a protective film liquid discharge head including a slit-like discharge port for discharging the protective film liquid composed of a water-soluble resin which forms a protective film on a surface of the workpiece held on the holding table; first moving means for approachably/separably and relatively moving the protective film liquid discharge head to the holding surface of the holding table; and second moving means for relatively moving the protective film liquid discharge head in a direction parallel to the holding surface of the holding table.

Description

  The present invention relates to a laser processing apparatus and a protective film coating method using the laser processing apparatus.

  A wafer such as a silicon wafer or a sapphire wafer formed on the surface by dividing a plurality of devices such as IC, LSI, LED, etc. by dividing lines is divided into individual devices by a processing apparatus, and the divided devices are mobile phones, Widely used in various electronic devices such as personal computers.

  A dicing method using a cutting device called a dicer is widely used for dividing the wafer. In the dicing method, a wafer is cut by cutting a wafer into a wafer while rotating a cutting blade having a thickness of about 30 μm by solidifying abrasive grains such as diamond with a metal or a resin at a high speed of about 30000 rpm. Divide into

  On the other hand, in recent years, a laser processing groove is formed by irradiating a wafer with a pulsed laser beam having a wavelength that absorbs the wafer, and the wafer is cut along the laser processing groove with a braking device to form individual laser processing grooves. A method of dividing into devices has been proposed (see, for example, Japanese Patent Laid-Open No. 10-305420).

  Laser processing grooves formed by a laser processing apparatus can increase the processing speed compared to a dicing method using a dicer, and relatively easily process even a wafer made of a material having high hardness such as sapphire or SiC. be able to. In addition, since the processing groove can be made to have a narrow width of, for example, 10 μm or less, the amount of devices taken per wafer can be increased as compared with the case of processing by the dicing method.

  However, when the wafer is irradiated with a pulse laser beam, debris is generated due to concentration of thermal energy in the region irradiated with the pulse laser beam. When this debris adheres to the device surface, there arises a problem that the quality of the device is lowered.

  Therefore, for example, in JP 2007-201178 A, a water-soluble resin such as PVA (polyvinyl alcohol) or PEG (polyethylene glycol) is applied to the processed surface of the wafer in order to solve such problems caused by debris. There has been proposed a laser processing apparatus in which a protective film is coated and a wafer is irradiated with a pulsed laser beam through the protective film.

JP-A-10-305420 JP 2007-2011178 A JP 2006-140311 A

  In a conventional protective film coating apparatus, the protective film liquid is supplied onto the workpiece while rotating the holding table holding the workpiece, and the protective film liquid is spread by centrifugal force to spread the protective film liquid on the entire surface of the workpiece. A spin coating method is generally used. However, the conventional spin coating method has a problem that approximately 90% or more of the protective film solution is discarded, which is uneconomical.

  In addition, in a protective film coating apparatus employing a conventional spin coating method, a large amount of protective film liquid scattered by spin coating becomes very thin thread-like waste, which accumulates inside the protective film coating apparatus and takes time to clean. It was difficult to completely remove the thread-like debris.

  In addition, thread-like waste easily floats in the air, and may be scattered during cleaning and adhere to the workpiece, contaminating the workpiece or contaminating the inside and outside of the protective film coating apparatus. there were.

  The present invention has been made in view of the above points, and an object thereof is to provide a laser processing apparatus and a protective film coating provided with an economical protective film coating apparatus that suppresses the amount of protective film liquid to be discarded. Is to provide a method.

  According to the first aspect of the present invention, there is provided a processing table for holding a workpiece, laser processing means for performing laser processing on the workpiece held on the processing table, and a cassette capable of accommodating a plurality of workpieces. A laser processing apparatus comprising: a cassette mounting table to be mounted; and a conveying unit that transports a workpiece from the cassette mounted on the cassette mounting table to at least the processing table, and holds the workpiece And a protective film liquid discharge head having a slit-like discharge port for discharging a protective film liquid made of a water-soluble resin that forms a protective film on the surface of the workpiece held on the holding table. First moving means for moving the protective film liquid discharge head relative to the holding surface of the holding table so that the protective film liquid discharge head can be moved toward and away from the holding table; and the protective film liquid discharge head of the holding table. Laser processing apparatus characterized by comprising a second moving means for moving in the direction parallel to the plane of, is provided.

  Preferably, the laser processing apparatus further includes a drive source for rotating the holding table with a rotation axis passing through the center of the holding surface and orthogonal to the holding surface. Preferably, the protective film liquid discharge head is attached to the conveying means, and the first moving means and the second moving means are shared by the conveying means.

  According to invention of Claim 4, it is the coating method of the protective film using the laser processing apparatus of Claim 2 or Claim 3, Comprising: The holding step which hold | maintains a to-be-processed object by the said holding table, This holding | maintenance A positioning step of positioning the protective film liquid discharge head at a predetermined height from the upper surface of the workpiece held on the table; and after performing the positioning step, the protective film liquid discharge head is rotated while rotating the holding table. A coating step of discharging the protective film liquid from the protective film liquid discharge head onto the workpiece while being moved on the holding table, and coating the upper surface of the workpiece with a protective film liquid having a predetermined thickness in a spiral shape; A holding table rotating step of rotating the holding table after the coating step to flatten the protective film solution and drying it to form a protective film. Film coating process is provided.

  According to the laser processing apparatus of claim 1, since it becomes possible to discharge the protective film liquid from the protective film liquid discharge head having the slit-shaped protective film liquid discharge port to coat the workpiece with the protective film, It is possible to reduce the amount of protective film liquid to be discarded.

  According to the fourth aspect of the invention, the holding table holding the workpiece is rotated and the protective film liquid discharge head is moved while discharging the protective film liquid from the slit-shaped protective film liquid discharge port to Since it is supplied to the upper surface, the protective film liquid can be applied spirally on the workpiece, and the amount of the protective film liquid to be discarded can be suppressed.

1 is a perspective view of a laser processing apparatus according to an embodiment of the present invention. It is a schematic diagram explaining arrangement | positioning of each mechanism part of the laser processing apparatus which concerns on this invention embodiment. FIG. 3 is a perspective view of a wafer unit in which a wafer is supported on an annular frame via a dicing tape. It is a perspective view of a laser beam irradiation unit. It is a block diagram of a laser beam generation unit. It is a longitudinal cross-sectional view of a protective film liquid discharge head. It is explanatory drawing of the protective film liquid coating method.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a perspective view of a laser processing apparatus 2 according to an embodiment of the present invention is shown. Reference numeral 4 denotes an outer cover of the laser processing apparatus 2, and a processing region 14 shown in FIG. 2 is disposed in the outer cover 4.

  A touch panel display monitor 6 is disposed on the front surface 4 a of the exterior cover 4. With this display monitor 6, the operator inputs an operation command for the apparatus, and the operating status of the apparatus is displayed on the display monitor 6.

  Reference numeral 8 denotes a cassette mounting table for mounting a cassette containing a plurality of wafers therein, and is configured to be movable in the vertical direction (Z-axis direction). As shown in FIG. 3, a wafer 11 such as a semiconductor wafer or an optical device wafer is divided into a plurality of regions by a plurality of division lines 13 formed in a lattice pattern on the surface thereof. A device 15 is formed.

  The wafer 11 is attached to a dicing tape T that is an adhesive tape, and the outer peripheral edge of the dicing tape T is attached to an annular frame F to constitute a wafer unit 17. As a result, the wafer 11 is supported by the annular frame F via the dicing tape T, and is accommodated in the cassette in this state.

  Adjacent to the cassette mounting table 8, a temporary placement area 10 for temporarily placing the wafer unit 17 taken out from the cassette 8 is provided. As best shown in the layout diagram of FIG. 2, a protective film coating region 12 is disposed adjacent to the temporary placement region 10 on the opposite side of the cassette mounting table 8 in the Y-axis direction. Further, the processing region 14 is disposed on an extension line in the X-axis direction of the temporary placement region 10. In the protective film coating region 12, a cleaning process for cleaning the wafer 11 after laser processing is also performed.

  Adjacent to the cassette mounting table 8, a loading / unloading unit (loading / unloading means) 16 for loading / unloading the wafer unit 17 with respect to the cassette mounted on the cassette mounting table 8 is provided.

  The carry-in / out unit 16 has a clamp 17 attached to the tip of the support member 18. With this clamp 17, the annular frame F shown in FIG. 3 is clamped to carry out the wafer unit 17 from the cassette or into the cassette.

  The support member 18 is fixed to the block 20, and a nut that engages with the ball screw 24 is built in the block 20. One end of the ball screw 24 is connected to a pulse motor 26, and the ball screw 24 and the pulse motor 26 constitute a carry-in / out unit moving mechanism 28 that moves the carry-in / out unit 16 in the Y-axis direction.

  When the pulse motor 26 of the carry-in / out unit moving mechanism 28 is driven, the ball screw 24 is rotated, and the block 20 is moved in the Y-axis direction accordingly, and the clamp 17 connected to the block 20 via the support member 18 is moved. Move in the Y-axis direction.

  The wafer unit 17 with the annular frame F clamped by the clamp 17 and pulled out from the cassette is placed on a pair of centering guides 30 disposed in the temporary placement region 10, and the centering guides 30 move in directions toward each other. Thus, centering of the wafer unit 17 is performed.

  A processing table 32 positioned at the home position is disposed below the temporary placement area 10. A plurality of clamps 34 that clamp the annular frame F are disposed on the processing table 32.

  The machining table 32 shown in FIG. 1 is positioned at the home position, and the machining table 32 is moved in the X-axis direction and positioned in the machining area 14 as shown in FIG. In order to index and feed the wafer 11 during laser processing, it is also possible to move in the Y-axis direction.

  An opening 36 is formed below the side surface 4 b of the exterior cover 4, and the wafer 11 held on the processing table 32 moves between the home position shown in FIG. 1 and the processing region 14 through the opening 36. Is done.

  Reference numeral 38 denotes an upper arm movable in the Y-axis direction and the Z-axis direction. An H-shaped plate member 40 is fixed to the lower end of the upper arm 38, and the annular frame F is sucked into the plate member 40 by vacuum suction. Four suction pads 42 to be held are attached.

  A rotatable holding table (spinner table) 44 is disposed in the protective film covering region 12. Although not particularly illustrated, a plurality of clamps for clamping the annular frame F are attached around the holding table 44.

  A protective film liquid discharge head 46 is disposed on the side surface of the lower end portion of the upper arm 38. The protective film liquid discharge head 46 is fixed to a Z-axis moving member 48, and the protective film liquid discharge head 46 is fixed to the upper arm 38 by a protective film liquid discharge head moving mechanism 56 including a ball screw 52 and a pulse motor 54. It can move in the vertical direction (Z-axis direction) along the pair of guides 50 formed.

  The upper arm 38 is attached to the Y-axis moving member 58 so as to be movable in the Z-axis direction by a moving mechanism (not shown). As the moving mechanism, for example, a combination of a ball screw and a pulse motor, an air cylinder, or the like can be used.

  The Y-axis moving member 58 has a built-in nut, and this nut is screwed into a ball screw 60 that extends in the Y-axis direction. A pulse motor 62 is connected to one end of the ball screw 60, and the ball screw 60 and the pulse motor 62 constitute a Y-axis moving mechanism 64 of the upper arm 38. When the pulse motor 62 is driven, the ball screw 60 rotates and the Y-axis moving member 58 is moved in the Y-axis direction along a pair of guides 66 fixed to the side surface 4b of the exterior cover 4.

  Reference numeral 68 denotes a lower arm. An H-shaped plate member 70 is fixed to the lower end of the lower arm 68, and four suction pads 72 for sucking and holding the annular frame F by vacuum suction are arranged on the H-shaped plate member 70. It is installed.

  The lower arm 68 is attached to the Y-axis moving member 74 so as to be movable in the vertical direction (Z-axis direction) by a moving mechanism (not shown). As the moving mechanism, a combination of a ball screw and a pulse motor, an air cylinder, or the like can be adopted.

  A nut (not shown) is built in the Y-axis moving member 74, and this nut is screwed into a ball screw 76 extending in the Y-axis direction. A pulse motor 78 is connected to one end of the ball screw 76, and the ball screw 76 and the pulse motor 78 constitute a Y-axis moving mechanism 80 of the lower arm 68.

  When the pulse motor 78 of the Y-axis moving mechanism 80 is driven, the ball screw 76 rotates, and the lower arm 68 connected to the Y-axis moving member 74 moves along the Y-axis along a pair of guides 82 attached to the side surface 4b of the exterior cover 4. Moved in the direction.

  As shown in FIG. 4, a column 86 is erected on the base 84 and a laser beam irradiation unit 90 is attached to the column 86 in the processing area 14 covered with the exterior cover 4. The laser beam irradiation unit 90 includes a laser beam generation unit 92 shown in FIG. 5 housed in a casing 88 and a condenser (processing head) 94 attached to the tip of the casing 88. An imaging unit 96 is attached to the tip of the casing 88 adjacent to the condenser 94.

  As shown in FIG. 5, the laser beam generating unit 92 includes a laser oscillator 98 such as a YAG laser oscillator or a YVO4 laser oscillator, a repetition frequency setting unit 100, a pulse width adjusting unit 102, and a power adjusting unit 104. Yes. Although not shown in particular, the laser oscillator 98 has a Brewster window, and the laser beam emitted from the laser oscillator 98 is a linearly polarized laser beam.

  As shown in FIG. 6, the protective film liquid discharge head 46 is formed with slit-like discharge ports 106 for discharging the protective film liquid. The slit-like discharge port 106 extends in a direction perpendicular to the paper surface in FIG. The discharge port 106 is connected to the protective film liquid supply source 110. As the protective film liquid, water-soluble resins such as PVA (polyvinyl alcohol) and PEG (polyethylene glycol) can be employed.

  The protective film liquid discharge head 46 further has a suction port 108 connected to the suction source 112 formed adjacent to the slit-shaped discharge port 106 on the leading side in the protective film liquid application direction indicated by the arrow Y1. doing. The suction port 108 is also formed in a slit shape extending in the direction perpendicular to the paper surface.

  By sucking air from the suction port 108, gas is prevented from being mixed into the protective film liquid 114 coated on the wafer 11. The arrow Y2 is the moving direction of the wafer 11 when the protective film liquid is applied.

  In the present specification, the carry-in / out unit 16 having the clamp 17, the upper arm 38 and its moving mechanism 64, the lower arm 68 and its moving mechanism 80 will be collectively referred to as conveying means. Therefore, in the above-described embodiment, the protective film liquid discharge head 46 is attached to the transport unit.

  Accordingly, in the present invention, the protective film liquid discharge head 46 is not limited to the form attached to the upper arm 38, but the protective film liquid discharge head 48 may be attached to the lower arm 68 or the loading / unloading unit 16.

  Hereinafter, the operation of the above-described laser processing apparatus 2 will be described. First, the clamp 17 pulls out the first wafer unit 17 from the cassette to the temporary placement area 10, and centers the wafer unit 17 with the centering guide 30.

  Next, the upper arm 38 sucks the wafer unit 17, moves in the Y-axis direction, and transports the wafer unit 17 to the holding table 44 disposed in the protective film coating region 12. The wafer 11 is sucked and held by the holding table 44 via the dicing tape T, and the annular frame F is clamped and fixed by a clamp (not shown).

  Next, as shown in FIG. 7, the protective film liquid discharge head 46 is moved from the outer peripheral side of the wafer 11 toward the center, and the protective film liquid is supplied from the slit-shaped discharge port 106 while rotating the holding table 44. Then, the protective film liquid 114 is spirally applied to the surface of the wafer 11.

  When the protective film liquid is applied, the rotation speed of the holding table 44 is increased, for example, from 2 rpm when the protective film liquid discharge head 46 is positioned on the outer peripheral side to 25 rpm when the protective film liquid discharge head 46 is positioned on the inner peripheral side. It is preferable to make the coating speed at the dotted point constant.

  After the application of the protective film liquid 114 is completed, the holding table 44 is rotated at, for example, 3000 rpm for about 30 seconds to flatten the protective film liquid 114 and dry to coat the surface of the wafer 11 with the protective film.

  After the surface of the wafer 11 is coated with a protective film, the upper arm 38 attracts the wafer unit 17 and conveys the wafer unit 17 to the processing table 32 positioned at the home position. The wafer 11 is sucked and held by the processing table 32 via the dicing tape T, and the annular frame F is clamped and fixed by the clamp 34.

  Next, the processing table 10 is moved in the X-axis direction to be positioned in the processing region 14, alignment is performed by the imaging unit 96, and then a laser beam having a wavelength (for example, 355 nm) having absorptivity to the wafer 11 from the condenser 94 Is irradiated along the planned dividing line 13 to form a laser processed groove by ablation.

  During laser processing on the first wafer 11, the clamp 17 pulls the second wafer unit 17 from the cassette to the temporary placement area 10 and performs centering with the centering guide 30.

  After the centering is performed, the upper arm 38 transports the second wafer unit 17 to the holding table 44 and covers the second wafer 11 with a protective film. After covering the protective film, the upper arm 38 sucks the second wafer unit 17 and holds it until the processing of the first wafer 11 is completed in a state where the wafer unit 17 is separated from the holding table 44.

  When the processing of the first wafer 11 is completed, the processing table 10 is moved in the X-axis direction and positioned at the home position shown in FIG. The lower arm 68 sucks the first wafer unit 17 on the processing table 32, moves in the Y-axis direction, transports the first wafer unit 17 that has been processed to the holding table 44, and after the processing is completed. The wafer 11 is cleaned.

  The second wafer unit 17 held by the upper arm 38 is transported to the processing table 32 and placed on the processing table 32. Next, the processing table 32 is conveyed to the processing region 14 in the X-axis direction, and laser processing is performed on the second wafer 11.

  While the first wafer 11 is being cleaned and the second wafer 11 is being processed, the clamp 17 pulls the third wafer unit 17 from the cassette to the temporary placement area 10 and performs centering by the centering guide 30. . After performing the centering, the upper arm 38 sucks and holds the third wafer unit 17.

  The lower wafer 68 transports the first wafer unit 17 that has been cleaned from the holding table 44 onto the centering guide 30, and the clamp 17 of the carry-in / out unit 16 moves the first wafer unit 17 that has been processed into the cassette. Accommodate.

  Thereafter, the carry-in / out unit 16, the upper arm 38, and the lower arm 68 are operated in this sequence to form a protective film on the wafer 11, and then a laser processing groove is formed in the wafer 11 by laser beam ablation processing.

  In this embodiment, since the conveying means is composed of the carry-in / out unit 16, the upper arm 38 and the lower arm 68, the wafer units 17 are pulled out from the cassette one after another without taking a processing waiting time, and the wafer 11 Laser processing can be performed after coating a protective film on the surface.

  According to the present embodiment, the protective film liquid can be ejected from the slit-shaped discharge port 106 of the protective film discharge head 46 and applied to the wafer 11 in a spiral shape. It is possible to reduce the amount of the membrane liquid.

  Further, since the conveying means is composed of the carry-in / out unit 16, the upper arm 38 and the lower arm 68, laser processing can be efficiently performed on a plurality of wafers 11 without taking a waiting time.

  In the embodiment described above, an example in which a wafer such as a semiconductor wafer or an optical device wafer is employed as a workpiece has been described. However, the workpiece is not limited to this, and has a pattern or a fine structure on the surface. The present invention is also applicable to other plate-like workpieces.

8 Cassette mounting table 10 Temporary placement area 12 Protective film coating area 14 Processing area 16 Loading / unloading unit 17 Clamp 30 Centering guide 32 Processing table 38 Upper arm 44 Holding table 46 Protective film liquid discharge head 68 Lower arm 90 Laser beam irradiation unit 94 Condensing Instrument (laser head)
106 Slit discharge port 108 Suction port

Claims (4)

A processing table for holding a workpiece; laser processing means for performing laser processing on the workpiece held on the processing table; a cassette mounting table on which a cassette capable of storing a plurality of workpieces is placed; A conveying means for conveying a workpiece from a cassette mounted on the cassette mounting table to at least the processing table, and a laser processing apparatus comprising:
A holding table having a holding surface for holding a workpiece;
A protective film liquid discharge head having a slit-like discharge port for discharging a protective film liquid made of a water-soluble resin that forms a protective film on the surface of the workpiece held by the holding table;
First moving means for moving the protective film liquid discharge head relative to the holding surface of the holding table so as to be close to and away from the holding surface;
Second moving means for relatively moving the protective film liquid discharge head in a direction parallel to the holding surface of the holding table;
A laser processing apparatus comprising:   The laser processing apparatus according to claim 1, further comprising a driving unit that rotates the holding table with a rotation axis that passes through the center of the holding surface and is orthogonal to the holding surface. The protective film liquid discharge head is attached to the transport means,
The laser processing apparatus according to claim 1, wherein the first moving unit and the second moving unit are shared by the transfer unit. A method for coating a protective film using the laser processing apparatus according to claim 2 or 3,
A holding step for holding a workpiece on the holding table;
A positioning step of positioning the protective film liquid discharge head at a predetermined height from the upper surface of the workpiece held by the holding table;
After performing the positioning step, the protective film liquid discharge head is discharged onto the work piece from the protective film liquid discharge head while moving the protective film liquid discharge head on the holding table while rotating the holding table, A coating step for spirally coating the upper surface of the workpiece with a protective film liquid having a predetermined thickness;
After performing the coating step, the holding table rotating step of rotating the holding table to flatten the protective film liquid and drying to form a protective film;
The protective film coating method characterized by including.

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