JP2017157749A - Processing method of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an economical processing method improving workability, and reducing the risk of wafer breakage incident to peel adhesion.SOLUTION: A processing method of a wafer 11 where a device 15 is formed in each region of a surface sectioned by a plurality of intersecting division lines includes a protective film formation step of forming a protective film 17 by coating the surface of the wafer with a resin hardening by external stimulation, a protective film flattening step of holding the back side 11b of the wafer by means of the chuck table, and flattening the protective film by cutting with a cutting tool, a grinding step of holding the protective film side of the wafer by the suction holding part 50 of the chuck table 46, and thinning to a predetermined thickness by grinding the back side, a step of holding the protective film side of the wafer by means of the chuck table, and detecting the division line from the back side of the wafer, and a step of processing the wafer from the back side along the division lines and dividing into a plurality of chips.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a wafer processing method in which a device is formed in each region of a surface defined by a plurality of intersecting scheduled lines.

  Wafers such as semiconductor wafers on which a plurality of semiconductor devices such as IC and LSI are formed on the front surface and optical device wafers on which a plurality of optical devices such as LEDs and LDs are formed are ground to a predetermined thickness. After being formed, the chips are divided into individual chips by a processing apparatus such as a cutting apparatus or a laser processing apparatus, and the divided chips are widely used in various electronic devices.

  In grinding the back surface of the wafer, in order to protect the devices formed on the front surface of the wafer, the chuck table of the grinding apparatus is passed through the surface protective tape with the surface protective tape attached to the front surface of the wafer. Then, the wafer is subjected to backside grinding (see, for example, Japanese Patent Application Laid-Open No. 2014-082230).

  This surface protection tape is used for the surface of the wafer by, for example, a peeling device disclosed in Japanese Patent Application Laid-Open No. 2011-023606 before the wafer is divided into individual chips by the cutting device after the back surface grinding of the wafer. It is peeled off and discarded.

  When the wafer is cut, a dicing tape is attached to the back surface of the wafer in order to facilitate the handling of the chip after cutting, and the outer peripheral portion of the dicing tape is attached to the annular frame (for example, Japanese Patent Laid-Open No. Hei 8). -088202). After the wafer is cut, the formed individual chips are picked up from the dicing tape, and the dicing tape is discarded.

JP 2014-082380 A JP 2011-023606 A JP-A-8-088202

  However, in order to divide the wafer into backside chips after grinding the wafer backside and then cutting along the planned dividing line, a surface protection tape and a dicing tape are attached to each wafer and then peeled off. Has the problem of poor workability and labor.

  In addition, it is very uneconomical to use a surface protection tape and a dicing tape for each wafer and to discard them after use. Further, for a wafer that has been ground very thinly, for example, 50 μm or less, there is a high risk of damaging the wafer when the surface protective tape is peeled off and when the dicing tape is attached.

  The present invention has been made in view of the above points. The object of the present invention is to improve workability as compared with the prior art and to be economical, and to peel off the surface protection tape and apply the dicing tape. It is an object of the present invention to provide a wafer processing method capable of reducing the risk of damage to a wafer accompanying attachment.

  According to the present invention, there is provided a wafer processing method in which a device is formed in each region of a surface divided by a plurality of intersecting scheduled lines, and the wafer surface is coated with a resin that is cured by an external stimulus. A protective film forming step for forming a protective film, and a protective film flattening step for performing flattening by holding the back side of the wafer with a chuck table and cutting the protective film with a cutting tool after performing the protective film forming step. And after performing the protective film flattening step, holding the protective film side of the wafer with a chuck table, grinding the back surface of the wafer with a grinding means to thin the wafer to a predetermined thickness, After performing the grinding step, the protection film side of the wafer is held by the chuck table, and the planned division line detection step for detecting the division line from the back side of the wafer And a division step of dividing the wafer into a plurality of chips by processing the wafer from the back side of the wafer along the division line after performing the division line detection step. A method for processing a wafer is provided.

  Preferably, the wafer processing method further includes a pickup step of picking up a plurality of chips from the protective film after performing the dividing step.

  According to the present invention, a protective film that protects a device formed on the front surface side of a wafer is formed using a resin that is cured by an external stimulus, and the wafer is cut from the back side by using the protective film as a dicing tape during cutting. And split into chips.

  Therefore, in order to divide the wafer into chips by performing a grinding step and a dividing step in one protective film formation without attaching a surface protective tape and a dicing tape for each wafer as in the past, and then peeling off, Workability can be improved compared to the conventional case.

  Further, when forming the protective film, the wafer has the original thickness before grinding, so there is no risk of damage to the wafer due to the formation of the protective film. Since peeling of the protective tape and sticking of the dicing tape are not performed according to the processing step, there is no fear of wafer breakage due to peeling of the surface protective tape and sticking of the dicing tape.

It is a surface side perspective view of a semiconductor wafer. It is sectional drawing of the wafer after a protective film formation step. It is a partial cross section side view which shows a protective film planarization step. It is a partial cross section side view which shows a grinding step. It is sectional drawing which shows a division | segmentation planned line detection step. It is sectional drawing which shows 1st Embodiment of a division | segmentation step. FIG. 7A is a cross-sectional view showing a second embodiment of the dividing step, and FIG. 7B is a cross-sectional view showing a third embodiment of the dividing step. FIG. 8 is a cross-sectional view showing a state in which after the modified layer is formed in the wafer in the dividing step of the third embodiment shown in FIG. 7B, an external force is applied to the wafer to divide the wafer into individual chips. It is a partial cross section side view which shows a pick-up step.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a front side perspective view of a semiconductor wafer 11 is shown. A semiconductor wafer (hereinafter sometimes simply referred to as a wafer) 11 shown in FIG. 1 is a silicon wafer having a thickness of about 700 μm, and a plurality of division lines (streets) 13 are formed in a lattice pattern on the surface 11a. In addition, devices 15 such as ICs and LSIs are formed in the respective regions partitioned by the plurality of division lines 13. 11 b is the back surface of the wafer 11.

  In the wafer processing method of the present invention, first, a protective film forming step is performed in which the surface 11a of the wafer 11 is covered with a resin that is cured by an external stimulus to form a protective film. FIG. 2 is a cross-sectional view after performing the protective film forming step, and the surface 11 a of the wafer 11 is covered with the protective film 17. In this embodiment, an ultraviolet curable resin is used as the resin that is cured by an external stimulus. However, a thermosetting resin that is cured by heating may be used.

  After the ultraviolet curable resin is applied to the surface 11a of the wafer 11 by a spin coating method, a press method, or the like, the ultraviolet curable resin is semi-cured by irradiating ultraviolet rays. The thickness of the protective film 17 is preferably in the range of 50 μm to 200 μm.

  After performing the protective film forming step, as shown in FIG. 3, the back surface 11b side of the wafer 11 is held by the chuck table 2 of the cutting tool, and the protective film 17 is turned by the cutting tool 20 to be flattened. A film planarization step is performed.

  In FIG. 3, the chuck table 2 includes a frame body 4, a holding part (pin chuck) 6 composed of a plurality of pins surrounded by the frame body 4, and a suction path 8 formed in the frame body 4. It is out. By selectively connecting the suction path 8 to a suction source, a negative pressure can be selectively applied to the pin chuck 6.

  The cutting tool unit 10 includes a spindle 12 that is rotationally driven by a motor, a wheel mount 14 that is fixed to the lower end of the spindle 12, and a cutting tool wheel 16 that is detachably attached to the wheel mount 14. The bite wheel 16 includes a base 18 and a cutting bit 20 that is detachably mounted on the outer periphery of the lower end of the base 18.

  In the protective film flattening step by the cutting tool 20, the back surface 11 b side of the wafer 11 is sucked and held by the chuck table 2 to expose the protective film 17. Then, the cutting tool unit 10 is positioned so that the cutting tool 20 cuts into the protective film 17 to a predetermined depth, the tool wheel 16 is rotated in the direction of arrow a, and the chuck table 2 is processed and fed linearly in the direction of arrow Y. Thereby, the protective film 17 is turned by the cutting tool 20 to be flattened.

  After performing the protective film flattening step, as shown in FIG. 4, the protective film 17 side of the wafer 11 is held by the chuck table 24 of the grinding device, and the back surface 11 b of the wafer 11 is ground by the grinding means (grinding unit) 32. Then, a grinding step for thinning the wafer 11 to a predetermined thickness is performed.

  In FIG. 4, the chuck table 24 of the grinding apparatus includes a frame body 26, a suction holding portion 28 formed of porous ceramics or the like surrounded by the frame body 26, and a suction path 30 formed in the frame body 26. It is out. By selectively connecting the suction path 36 to a suction source, a negative pressure is selectively applied to the suction holder 28.

  The grinding unit 32 includes a spindle 34 that is rotationally driven by a motor, a wheel mount 36 that is fixed to the lower end of the spindle 34, and a grinding wheel 38 that is detachably attached to the wheel mount 36. The grinding wheel 38 includes an annular wheel base 40 and a plurality of grinding wheels 42 fixed to the outer periphery of the lower end of the wheel base 40.

  In the grinding step, the chuck film 24 sucks and holds the side of the protective film 17 attached to the front surface of the wafer 11 to expose the back surface 11 b of the wafer 11. While rotating the chuck table 24 holding the wafer 11 in the direction of arrow a at 300 rpm, for example, the grinding wheel 38 is rotated in the direction indicated by arrow b at, for example, 6000 rpm, and a grinding unit feed mechanism (not shown) is driven to drive the grinding wheel 42. Is brought into contact with the back surface 11 b of the wafer 11.

  Then, the back surface 11b of the wafer 11 is ground while the grinding wheel 38 is ground and fed downward at a predetermined grinding feed speed. While measuring the thickness of the wafer 11 with a contact or non-contact thickness gauge, the wafer 11 is thinned to a predetermined thickness.

  After performing the grinding step, as shown in FIG. 5, the protective film 17 side of the wafer 11 is sucked and held by the chuck table 46 of the cutting apparatus, and the wafer 11 is imaged by the imaging unit 54 from the back surface 11b side of the wafer 11, A planned division line detection step for detecting the planned division line 13 is performed.

  In FIG. 5, the chuck table 46 of the cutting apparatus includes a frame body 48, a suction holding unit 50 formed of porous ceramics or the like surrounded by the frame body 48, and a suction path 52 formed in the frame body 48. It is out. The suction path 52 is selectively connected to a suction source. The imaging unit 54 includes an infrared imaging element in addition to a normal imaging element.

  In the scheduled division line detection step, the suction path 52 of the chuck table 46 is connected to the suction source, the suction holding unit 50 sucks and holds the protective film 17 side, and the back surface 11b of the wafer 11 is exposed. Then, the dividing line 13 that passes through the wafer 11 by the infrared imaging element of the imaging unit 54 and extends in the first direction formed on the surface 11a of the wafer 11 and the second direction orthogonal to the first direction. Each of the planned division lines 13 that are expanded to the same is detected.

  After performing the division | segmentation planned line detection step, the division | segmentation step which processes the wafer 11 from the back surface 11b side of the wafer 11 along the division | segmentation planned line 13, and divides the wafer 11 into a some chip | tip is implemented. Referring to FIG. 6, a cross-sectional view of the first embodiment of the dividing step is shown.

  In 1st Embodiment of a division | segmentation step, a division | segmentation step is implemented with the cutting blade 54 of a cutting device. That is, the wafer 11 is sucked and held through the protective film 17 by the chuck table 46 of the cutting device, and the cutting blade 54 rotating at high speed is cut from the back surface 11b side of the wafer 11 through the wafer 11 to the protective film 17 to a predetermined depth. The wafer 11 is cut along the detected division line 13 in the direction of the arrow X1.

  54 a is the cutting edge position of the cutting blade 54 at the time of cutting, and t 1 represents the uncut portion of the protective film 17. That is, in this embodiment, the protective film 17 is used in the same manner as a dicing tape according to a conventional method, and the wafer 11 is fully cut.

  The cutting blades 54 are indexed and fed at intervals of the adjacent division lines 13 to cut the division lines 13 extending in the first direction one after another. Next, after the chuck table 46 is rotated by 90 °, all the division lines 13 extending in the second direction are cut to divide the wafer 11 into individual chips.

  Referring to FIG. 7A, there is shown a cross-sectional view of the second embodiment of the dividing step using the laser processing apparatus. The chuck table 58 of the laser processing apparatus includes a frame body 60, a suction holding unit 62 formed from porous ceramics or the like surrounded by the frame body 60, and a suction path 64 formed in the frame body 60. The suction path 64 is selectively connected to a suction source.

  In the dividing step of the second embodiment, the wafer 11 is sucked and held via the protective film 17 by the suction holding unit 62 of the chuck table 58, and the back surface 11b of the wafer 11 is exposed. Then, a laser beam LB1 having a wavelength (for example, 355 nm) having an absorptivity with respect to the wafer 11 is irradiated from the condenser 66 along the planned division line 13 detected from the back surface 11b side of the wafer 11, and the chuck table 58 is indicated by an arrow By machining and feeding in the X2 direction, a laser machining groove is formed along the planned dividing line 13 by ablation.

  For example, the laser beam LB1 is irradiated by a plurality of passes along the same division line 13 and the wafer 11 is fully cut by ablation. As an alternative embodiment, the wafer 11 may be half-cut by ablation, and the wafer 11 may be divided into individual chips by a braking device 68 as shown in FIG.

  In the case of division by the laser processing apparatus as in the present embodiment, the division planned line detection step described with reference to FIG. 5 is performed in such a manner that the wafer 11 is held by the chuck table 58 of the laser processing apparatus, 13 is detected.

  Referring to FIG. 7B, a third embodiment of the dividing step is shown. In the division step of the third embodiment, the wafer 11 is irradiated with a laser beam LB2 having a wavelength (for example, 1064 nm) having transparency to the wafer 11.

  That is, in the dividing step of the third embodiment, the protective film 17 side is sucked and held by the chuck table 58, and the back surface 11b of the wafer 11 is exposed. Then, the laser beam LB2 is irradiated from the back surface 11b side of the wafer 11 while the focusing point of the laser beam LB2 is adjusted to the inside of the wafer 11 from the condenser 66, and the chuck table 58 is processed and sent in the direction of the arrow X2. Then, the modified layer 19 is formed along the division line 13 inside the wafer 11.

  While the chuck table 58 is indexed and fed at an interval between adjacent division lines 13, the same modified layer 19 is formed along all the division lines 13 extending in the first direction. Next, after the chuck table 58 is rotated by 90 °, the same modified layer 19 is formed along all the planned division lines 13 extending in the second direction orthogonal to the first direction.

  After the modified layer 19 is formed inside the wafer 11 along all the planned dividing lines 13, the wafer 11 is divided into individual chips 23 using a braking device 70 as shown in FIG. 8.

  The braking device 70 shown in FIG. 8 is mounted on a support base 72 in which an air supply path 74 is formed, a plurality of clamps 76 attached to the support base 72, and the support base 72. And an elastic sheet 78 attached to the surface.

  In the external force imparting step, first, as shown in FIG. 8A, the wafer 11 in which the modified layer 19 is formed inside the wafer 11 along the scheduled division line 13 is supported by the support base 70 via the protective film 17. It is mounted on the elastic sheet 78 placed on top.

  Then, the outer peripheral surplus area 21 on the outermost periphery of the wafer 11 is clamped and fixed by a clamp 76. Here, since the outer peripheral part of the elastic sheet 78 is adhered to the support base 72, the outer peripheral part is kept airtight.

  Next, as shown in FIG. 8B, compressed air is supplied to the lower side of the elastic sheet 78 from the air supply source 80 via the air supply path 74, and external force is applied to the elastic sheet 78 by the compressed air, and the elasticity is increased. The sheet 78 is deformed into a convex shape.

  As a result, bending stress acts on the wafer 11, so that the wafer 11 is divided into individual chips 23 along the planned division line 13 with the modified layer 19 formed inside as a starting point of breakage.

  After performing the dividing step, as shown in FIG. 9, a pickup step for picking up individual chips 23 attached to the protective film 17 from the protective film 17 is performed. In this pickup step, the protective film 17 is irradiated with ultraviolet rays so that the protective film 17 is completely cured to reduce the adhesive strength of the protective film 17, and then the chip 23 is picked up by the collet 84 of the pickup device 82.

  In the case where the protective film 17 is formed of a thermosetting resin, the protective film 17 is heated to completely cure the protective film 17 made of the thermosetting resin to reduce its adhesive force. Perform the pick-up step.

10 Byte Cutting Unit 11 Semiconductor Wafer 13 Divided Line 15 Device 17 Protective Film 19 Modified Layer 20 Cutting Bit 21 Wafer Perimeter Excess Area 23 Chip 32 Grinding Unit 38 Grinding Wheel 44 Imaging Unit 54 Cutting Blade 66 Concentrator 70 Breaking Device 76 Clamp 78 Elastic sheet 82 Pickup device 84 Collet

Claims (2)

A wafer processing method in which a device is formed in each region of a surface partitioned by a plurality of division lines to intersect,
A protective film forming step of forming a protective film by coating the surface of the wafer with a resin that is cured by an external stimulus;
After performing the protective film forming step, the back surface side of the wafer is held by a chuck table, and the protective film is flattened by cutting the protective film with a cutting tool,
After performing the protective film flattening step, holding the protective film side of the wafer with a chuck table, grinding the back surface of the wafer with a grinding means to thin the wafer to a predetermined thickness,
After carrying out the grinding step, the protective film side of the wafer is held by a chuck table, and the division planned line detection step for detecting the division planned line from the back side of the wafer;
After performing the planned division line detection step, the division step of processing the wafer from the back side of the wafer along the division line to divide the wafer into a plurality of chips,
A wafer processing method characterized by comprising:   The wafer processing method according to claim 1, further comprising a pickup step of picking up the plurality of chips from the protective film after performing the dividing step.

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