JP2018190833A - Wafer processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a paste of a surface protective tape from remaining in a processed workpiece from which the surface protective tape is peeled when the workpiece is a wafer having a protrusion such as a bump.SOLUTION: A wafer processing method comprises: an irradiation step of irradiating a surface Wa of a wafer W with ultraviolet light; a surface protective tape sticking step of sticking a surface protective tape T composed of a base material layer T1 and a paste layer T2 on the base material layer T1 to the surface Wa of the wafer W after performing the irradiation step; a processing step of processing a rear surface Wb side of the wafer W after performing the surface protective tape sticking step; and a removal step of removing the surface protective tape T from the surface Wa of the wafer W after performing the processing step.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a wafer processing method in which devices having a plurality of protrusions are formed on a plurality of surfaces.

  When processing the back side of a wafer, a surface protection tape (see, for example, Patent Document 1) is widely used to protect the surface side on which a device is formed.

Japanese Patent Laid-Open No. H11-307620

  However, when the workpiece is a wafer having projections such as bumps, there is a problem that the paste of the surface protection tape remains on the root of the projection of the workpiece after processing.

  Therefore, when the workpiece is a wafer having protrusions such as bumps, there is a problem that the paste of the surface protection tape does not remain on the processed wafer.

  The present invention for solving the above problems is a wafer processing method in which a device having a plurality of protrusions is formed on a plurality of surfaces, an irradiation step of irradiating the surface of the wafer with ultraviolet rays, and the irradiation step. After carrying out, after carrying out the surface protective tape sticking step for sticking the surface protective tape consisting of the base material layer and the adhesive layer on the base material layer to the surface of the wafer, and the surface protective tape sticking step A processing method comprising: a processing step of processing the back side of the wafer; and a removing step of removing the surface protection tape from the front surface of the wafer after performing the processing step.

  In the processing method according to the present invention, an irradiation step of irradiating the surface of the wafer with ultraviolet rays is performed to remove dirt such as organic matter on the surface of the wafer or to modify the surface. After that, in order to attach the surface protection tape to the surface of the wafer in the surface protection tape application step, even if the wafer has protrusions such as bumps on the surface, the surface protection tape is peeled off after processing. It is possible to prevent the adhesive of the surface protection tape from remaining on the surface of the wafer.

It is a perspective view which shows an example of a wafer. It is a side view which shows the state which has irradiated the ultraviolet ray on the surface of the wafer. It is a side view of the wafer with which the surface protection tape was stuck on the surface. It is a perspective view which shows an example of a laser processing apparatus. It is sectional drawing which shows the state which has irradiated the laser beam along the division | segmentation planned line, and has formed the modified layer inside the to-be-processed object. It is sectional drawing which shows the state which grinds the back surface of a wafer. It is sectional drawing which shows the state which is removing the surface protection tape from the surface of a wafer.

A wafer W having a circular plate shape as shown in FIG. 1 is, for example, a silicon wafer. On the surface Wa, a device D such as an IC or LSI is provided in a plurality of grid-like regions partitioned by a plurality of division lines S. Is formed. A plurality of protrusions (for example, protrusion electrodes made of metal or the like) Wf are provided on the surface of each device D at a predetermined height.
Hereinafter, each step when the wafer W is processed by the processing method according to the present invention will be described.

(1) Irradiation Step First, the surface Wa of the wafer W is irradiated with ultraviolet rays. The ultraviolet irradiator disposed above the surface Wa of the wafer W shown in FIG. 1 is, for example, a low-pressure mercury lamp 50 and can simultaneously irradiate ultraviolet rays having a wavelength of 184.9 nm and ultraviolet rays having a wavelength of 253.7 nm. . By irradiating ultraviolet rays having a wavelength of 184.9 nm downward from the low-pressure mercury lamp 50, oxygen molecules existing in the atmosphere absorb the ultraviolet rays and generate oxygen atoms in the ground state. Furthermore, the generated oxygen atoms combine with surrounding oxygen molecules to generate ozone. The generated ozone absorbs ultraviolet rays having a wavelength of 253.7 nm and generates oxygen and active oxygen. Since extremely unstable active oxygen has a high oxidizing power, it is oxidized and decomposed in combination with an organic compound such as oil adhering to the surface Wa of the wafer W, for example. Then, the organic compound such as oil becomes H ₂ O, CO ₂ , NO, and the like, and is volatilized and removed from the surface Wa of the wafer W. Further, the surface Wa of the wafer W is modified to be hydrophilic, for example.

(2) Surface Protection Tape Adhesion Step Next, the wafer W is transferred onto the adhesion table 51 shown in FIG. Note that the irradiation of the surface Wa of the wafer W with ultraviolet rays may be performed on the main attachment table 51.

  The surface protective tape T shown in FIG. 3 is, for example, a circular tape having a diameter approximately equal to the diameter of the wafer W, and a base layer T1 made of a polymer resin or the like, and an adhesive paste on the base layer T1. And an adhesive layer T2. The surface protection tape T in a state where the adhesive layer T2 faces downward with respect to the wafer W is positioned so that the center of the wafer W and the center of the surface protection tape T substantially coincide with each other. Then, the adhesive layer T2 of the surface protection tape T is pressed against the surface Wa of the wafer W by a not-shown press roller or the like, and the surface protection tape T is adhered to the wafer W.

(3) Processing Step In the processing step in the present embodiment, a laser beam having a wavelength that is transmissive to the wafer W is irradiated from the back surface Wb side with the condensing point positioned inside the division planned line S, A process called stealth dicing is performed in which a modified layer is formed inside the wafer W, and an external force is applied to the modified layer by grinding to divide the wafer W into individual chips. Note that the processing in the processing step is not limited to stealth dicing, and may be cutting processing in which cutting is performed from the back surface Wb side of the wafer W with a cutting blade, or grinding processing in which the back surface Wb of the wafer W is ground. For example, the wafer W to which the surface protection tape T is attached is conveyed to the laser processing apparatus 2 shown in FIG.

In front of the base 20 (−Y direction side) of the laser processing apparatus 2, a processing feed unit 21 that reciprocates the holding table 30 in the X-axis direction that is the processing feed direction is provided. The processing feed means 21 includes a ball screw 210 having an axis in the X-axis direction, a pair of guide rails 211 arranged in parallel to the ball screw 210, a motor 212 for rotating the ball screw 210, and an internal nut formed by the ball screw 210. And a movable plate 213 whose bottom is in sliding contact with the guide rail 211. When the motor 212 rotates the ball screw 210, the movable plate 213 is guided by the guide rail 211 and moves in the X-axis direction, and the holding table 30 disposed on the movable plate 213 is moved to the movable plate 213. Move in the X-axis direction.
On the base 20, a scale 200 is formed that extends in the X-axis direction along the guide rail 211 and indicates the position of the movable plate 213 in the X-axis direction.

  The holding table 30 for holding the wafer W has a circular outer shape, and includes a holding surface 300 configured by a porous member or the like for sucking and holding the wafer W. A suction source (not shown) communicates with the holding surface 300. The holding table 30 can be rotated around the axis in the vertical direction (Z-axis direction) by a rotating means 32 disposed on the bottom side of the holding table 30.

The holding table 30 can be reciprocated in the X-axis direction by the processing feed means 21, and is also moved in the Y-axis direction by the index feed means 22 disposed below the holding table 30 via the rotating means 32. Is possible. The index feeding means 22 includes a ball screw 220 having an axis in the Y-axis direction, a pair of guide rails 221 arranged in parallel to the ball screw 220, a motor 222 that rotates the ball screw 220, and an internal nut formed by the ball screw 220. And a movable plate 223 whose bottom portion is in sliding contact with the guide rail 221. When the motor 222 rotates the ball screw 220, the movable plate 223 is guided by the guide rail 221 and moves in the Y-axis direction, and the holding table 30 disposed on the movable plate 223 moves the movable plate 223. Move in the Y axis direction.
On the movable plate 223, a scale 223a is formed that extends in the Y-axis direction along the guide rail 221 and indicates the position of the movable plate 223 in the Y-axis direction.

  A column 20A is erected on the rear side (+ Y direction side) of the base 20, and the laser beam irradiation means 6 is disposed on the side surface of the column 20A on the + X direction side. The laser beam irradiation means 6 includes, for example, a rectangular parallelepiped housing 60 disposed horizontally with respect to the base 20, and a laser beam oscillator 61 is disposed in the housing 60. The laser beam oscillator 61 is, for example, a YAG laser or a YVO4 laser, and can oscillate a laser beam having a predetermined wavelength that is transmissive to the wafer W.

  At the tip of the housing 60, a condenser 62 having a condenser lens 62a is disposed inside. The laser beam irradiation means 6 reflects the laser beam oscillated from the laser beam oscillator 61 in the −Y-axis direction by a mirror (not shown) provided in the housing 60 and the condenser 62, and collects the condenser lens 62a. By making the light incident on the laser beam, the laser beam can be accurately condensed and irradiated onto a predetermined height position of the wafer W held by the holding table 30. The focal point position of the laser beam condensed by the condenser 62 can be adjusted in a direction perpendicular to the holding surface 300 of the holding table 30 by a focal point position adjusting unit (not shown).

  In the vicinity of the condenser 62, the alignment means 4 for detecting the division line S of the wafer W is disposed. The alignment unit 4 includes an infrared irradiation unit (not shown) that irradiates infrared rays, and an infrared camera 40 that includes an optical system that captures infrared rays and an imaging device (infrared CCD) that outputs electrical signals corresponding to the infrared rays. Based on the image acquired by the infrared camera 40, the division line S of the surface Wa of the wafer W can be detected by image processing such as pattern matching.

  In the processing step, first, as shown in FIG. 5, the wafer W is sucked and held by the holding table 30 with the back surface Wb facing upward. Next, the wafer W held on the holding table 30 is sent in the −X direction (forward direction) by the processing feed means 21 and is transmitted through the rear surface Wb side of the wafer W by the infrared camera 40 to pick up the division planned line S. The alignment unit 4 executes image processing such as pattern matching based on the image of the planned division line S imaged by the infrared camera 40, and the position of the planned division line S serving as a reference for irradiating the laser beam is detected.

  As the scheduled division line S is detected, the holding table 30 that holds the wafer W is indexed and fed in the Y-axis direction by the index feeding means 22, and the division planned line S that becomes the reference for irradiating the laser beam and the light collection. Positioning with the device 62 in the Y-axis direction is performed. Next, the condensing point position of the laser beam condensed by the condensing lens 62 a is positioned at a predetermined height position inside the wafer W. Then, a laser beam having a wavelength having transparency to the wafer W is oscillated from the laser beam oscillator 61, and the laser beam is condensed and irradiated on the inside of the wafer W held by the holding table 30.

  While irradiating the wafer W along the division line S with the laser beam, the wafer W is processed and fed in the −X direction at a predetermined processing feed rate, and the modified layer M is formed inside the wafer W as shown in FIG. To form. The formation position of the modified layer M in the thickness direction of the wafer W is, for example, a position higher than the position above the surface Wa of the wafer W by the finished thickness of the wafer W after grinding.

  When the wafer W advances in the −X direction to a predetermined position in the X-axis direction where the irradiation with the laser beam is completed along one division planned line S, the irradiation of the laser beam is stopped and the −W direction of the wafer W is stopped. Machining feed is stopped. Next, the holding table 30 is indexed and fed in the Y-axis direction, and the planned dividing line S and the condenser 62 located next to the scheduled dividing line S that becomes the reference when irradiating the laser beam in the processing feed in the -X direction. Are aligned in the Y-axis direction. After the alignment, the wafer W is processed and fed in the + X direction (reverse direction), and the laser beam enters the inside of the wafer W along one division planned line S in the same manner as the irradiation of the laser beam in the forward direction. Is irradiated and the modified layer M is formed. By sequentially irradiating the same laser beam, the laser beam is irradiated to the inside of the wafer W along all the division lines S extending in the X-axis direction, and the modified layer M is formed along each division line S. It is formed.

  Further, when the same irradiation with the laser beam is performed on the wafer W after the holding table 30 is rotated 90 degrees by the rotating means 32, the modified layer M is formed inside the wafer W along all the planned division lines S in the vertical and horizontal directions. Can be formed.

  Next, the wafer W is transferred to, for example, the grinding apparatus 1 shown in FIG. A grinding apparatus 1 shown in FIG. 1 is an apparatus for grinding a wafer W held on a holding table 10 by a grinding means 11.

  The holding table 10 that holds the wafer W has a circular outer shape, and includes a holding surface 100 that is configured of a porous member and holds the wafer W by suction. A suction source (not shown) communicates with the holding surface 100. The holding table 10 can rotate around an axis in the vertical direction (Z-axis direction) and can reciprocate in the X-axis direction.

The grinding means 11 is detachably mounted on a spindle 110 whose axial direction is the Z-axis direction, a motor (not shown) that rotationally drives the spindle 110, a mount 111 connected to the lower end side of the spindle 110, and a lower surface of the mount 111. And a ground grinding wheel 112.
The grinding wheel 112 includes an annular wheel base 112b and a plurality of substantially rectangular parallelepiped grinding wheels 112a disposed in a ring shape on the lower surface of the wheel base 112b. The grinding wheel 112a is formed by, for example, fixing diamond abrasive grains or the like with an appropriate binder.

  First, the wafer W is placed on the holding surface 100 with the back surface Wb facing upward so that the center of the holding table 10 and the center of the wafer W substantially coincide. Then, the suction force generated by a suction source (not shown) is transmitted to the holding surface 100, whereby the holding table 10 sucks and holds the wafer W.

  Next, the holding table 10 holding the wafer W moves in the + X direction to below the grinding unit 11, and the grinding wheel 112 provided in the grinding unit 11 and the wafer W are aligned. For example, as shown in FIG. 6, the rotation center of the grinding wheel 112 is shifted in the + X direction by a predetermined distance with respect to the rotation center of the holding table 10, and the rotation trajectory of the grinding wheel 112 a is the rotation center of the wafer W. Is done through.

  After the positioning of the grinding wheel 112 and the wafer W is performed, the grinding wheel 112 rotates as the spindle 110 is driven to rotate counterclockwise as viewed from the + Z direction side. Further, the grinding means 11 is sent in the −Z direction, and the grinding wheel 112 a of the rotating grinding wheel 112 abuts on the back surface Wb of the wafer W to perform grinding. During grinding, as the holding table 10 rotates counterclockwise as viewed from the + Z direction side, the wafer W held on the holding surface 100 also rotates, so that the grinding wheel 112a becomes the back surface Wb of the wafer W. Grind the entire surface. During the grinding process, the grinding water is supplied to the contact portion between the grinding wheel 112a and the wafer W to cool and clean the contact portion.

  When grinding is continued, the grinding pressure acts along the modified layer M shown in FIG. 6 so that cracks extend mainly toward the surface Wa of the wafer W starting from the modified layer M. Divided into chips. Then, grinding is continued even after the division, and when the wafer W is formed to a finished thickness, the grinding means 11 is raised, the grinding wheel 112a is separated from the wafer W, the grinding is finished, and the processing steps in this embodiment are completed. To do.

(4) Removal Step As shown in FIG. 7, the adhesive tape T3 is attached to the back surface Wb of the wafer W divided into chips C. The adhesive tape T3 is, for example, a disk-shaped tape having an outer diameter larger than the outer diameter of the wafer W. For example, the annular frame F is positioned with respect to the wafer W so that the center of the wafer W placed on an attachment table (not shown) and the center of the opening of the annular frame F substantially coincide. Then, the adhesive tape T3 is pressed against and adhered to the back surface Wb of the wafer W by a press roller or the like on the bonding table. At the same time, by attaching the outer peripheral portion of the adhesive surface of the adhesive tape T3 to the annular frame F, the wafer W is supported by the annular frame F via the adhesive tape T3. It becomes ready for handling.
After the wafer is supported by the annular frame F, the surface protection tape T is peeled off from the outer peripheral edge of the wafer W and removed from the surface Wa of the wafer W.

  In the processing method according to the present invention, an irradiation step of irradiating the surface Wa of the wafer W with ultraviolet rays is performed to remove dirt such as organic matter on the surface Wa of the wafer W, or the surface Wa is modified to be hydrophilic, for example. . Then, in order to stick the surface protective tape T to the surface Wa of the wafer W in the surface protective tape attaching step, even if the wafer W has the protrusions Wf such as bumps on the surface Wa, the surface is processed after being processed. It is possible to prevent the paste of the adhesive layer T2 of the surface protective tape T from remaining on the surface Wa of the wafer W shown in FIG. 7 from which the protective tape T has been peeled, particularly the root portion of the protrusion Wf.

W: Wafer Wa: Wafer surface Wb: Wafer back surface Wf: Projection S: Divided line D: Device M: Modified layer C: Chip 50: Low-pressure mercury lamp 51: Pasting table T: Surface protection tape T1: Base material layer T2: Adhesive layer 2: Laser processing device 20: Base 20A: Column 30: Holding table 300: Holding surface 32: Rotating means
21: Processing feed means
210: Ball screw 211: Guide rail 212: Motor 213: Movable plate
22: Index feeding means 220: Ball screw 221: Guide rail 222: Motor 223: Movable plate 6: Laser beam irradiation means 60: Housing 61: Laser beam oscillator 62: Condenser 62a: Condensing lens
4: Alignment means 40: Infrared camera 1: Grinding device 10: Holding table 100: Holding surface 11: Grinding means 110: Spindle 111: Mount 112: Grinding wheel 112a: Grinding wheel 112b: Wheel base T3: Adhesive tape F: Ring flame

Claims (1)

A wafer processing method in which a device having a plurality of protrusions is formed on a plurality of surfaces,
An irradiation step of irradiating the surface of the wafer with ultraviolet rays;
After carrying out the irradiation step, a surface protective tape attaching step for attaching a surface protective tape comprising a base material layer and a glue layer on the base material layer to the surface of the wafer;
After performing the surface protection tape attaching step, a processing step for processing the back side of the wafer;
And a removal step of removing the surface protection tape from the surface of the wafer after performing the processing step.

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