Method for processing a wafer

Abstract

To provide a wafer processing method capable of preventing quality deterioration due to direct adhesion of debris to a surface side of a device chip without breaking or damaging the wafer even when a protrusion exists on a surface of the wafer.SOLUTION: A method for processing a wafer having a plurality of devices formed on a surface partitioned by division schedule lines, includes: a low viscosity resin covering step of covering portions constituting the devices by applying a first liquid resin with low viscosity to the surface of the wafer; a high viscosity resin covering step of, after the low viscosity resin covering step, applying a second liquid resin having higher viscosity than the first liquid resin to the surface of the wafer on top of the first liquid resin; a resin curing step of curing the covered first liquid resin and the second liquid resin; and a flattening step of flattening the cured resins.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for processing a wafer formed on a surface partitioned by a division planned line by a plurality of devices.

Background Art

[0002] A wafer formed on a surface partitioned by a division planned line by a plurality of devices such as ICs and LSIs is divided into individual device chips by a dicing device and used in electrical devices such as mobile phones and personal computers.

[0003] In addition, a technique has been proposed in which a condensing point of a laser beam having a wavelength that is transmissive to the wafer is positioned inside corresponding to the division planned line and irradiated to form a modified layer along the division planned line, and then the back surface is ground to a desired thickness and the wafer is divided into individual device chips (see Patent Document 1).

[0004] Furthermore, a technique has been proposed in which a condensing point of a laser beam having a wavelength that is absorptive to the wafer is positioned on the division planned line and ablation processing is performed to form a groove and divide the wafer into individual device chips (see Patent Document 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, when applying the technique described in Patent Document 1 above to a wafer having unevenness, for example, protruding electrodes called bumps, formed on the surface of the device, and coating a protective film for embedding the bumps and grinding the back surface of the wafer, there is a problem that grinding debris enters from the gap between the device divided into individual device chips and the protective film, contaminating the bumps.

[0007] Further, when applying the technique described in Patent Document 2 above to a wafer having bumps formed thereon as described above, coating a protective film made of a liquid resin on the surface, and positioning the condensing point of a laser beam having an absorbable wavelength with respect to the wafer on the dividing planned line on the surface of the wafer to perform ablation processing, there is a problem that the protective film peels off and debris adheres directly to the surface of the device chip, deteriorating the quality.

[0008] The present invention has been made in view of the above facts, and its main technical problem is to provide a wafer processing method capable of solving the problem that debris adheres directly to the surface side of a device chip and the quality deteriorates without damaging or injuring the wafer even if there are protrusions on the surface of the wafer.

Means for Solving the Problems

[0009] In order to solve the above main technical problem, according to the present invention, Having a plurality of protrusions on the surface A method for processing a wafer formed on a surface in which a plurality of devices are partitioned by dividing planned lines, the method including: a low-viscosity resin coating step of applying a first liquid resin having a low viscosity to the surface of the wafer to cover a part constituting the device; after the low-viscosity resin coating step, a high-viscosity resin coating step of applying a second liquid resin having a higher viscosity than the first liquid resin to the surface of the wafer and overlaying the first liquid resin; a resin curing step of curing the coated first liquid resin and second liquid resin To form a protective film ; and a flattening step of flattening the cured resin The protective film formed thereby is provided. , perform a grinding process of grinding the back surface of the wafer while holding the side on which the protective film is formed on a chuck table A method for processing a wafer is provided.

[0010] In the planarization process, it is preferable to hold the back surface of the wafer on the chuck table, expose the front surface of the wafer, and cut and planarize the resin by cutting means equipped with a bite.

[0011] While implementing the above-described wafer processing method, a modified layer forming step of forming a modified layer along the planned division line by irradiating the condensing point of a laser beam having a wavelength that is transmissive to the wafer from the back surface corresponding to the planned division line to the inside, and a dividing step of grinding the back surface of the wafer with a grinding wheel, finishing the wafer to a predetermined thickness, and dividing the wafer into individual device chips from the modified layer may be included. Further, while implementing the above-described wafer processing method, a grinding step of grinding the back surface of the wafer with a grinding wheel and finishing the wafer to a predetermined thickness, a modified layer forming step of forming a modified layer along the planned division line by irradiating the condensing point of a laser beam having a wavelength that is transmissive to the wafer from the back surface corresponding to the planned division line to the inside, and a dividing step of applying an external force to the wafer and dividing the wafer into individual device chips may be included.

[0012] While implementing the above-described wafer processing method, an ablation processing step of performing ablation processing along the planned division line by irradiating the condensing point of a laser beam having a wavelength that is absorptive to the wafer to the front surface corresponding to the planned division line may be included. Further, while implementing the above-described wafer processing method, before the low-viscosity resin coating step, a groove forming step of forming a groove in the planned division line formed on the front surface of the wafer is performed, and after the groove forming step, the low-viscosity resin coating step, the high-viscosity resin coating step, the resin curing step, and the planarization step are performed, and then, the back surface of the wafer is ground with a grinding wheel, the wafer is finished to a predetermined thickness, the groove is exposed, and a dividing step of dividing the wafer into individual device chips may be performed.

Advantages of the Invention

[0013] The wafer processing method of the present invention Having a plurality of protrusions on the surfaceA method for processing a wafer on which a plurality of devices are formed on a surface partitioned by a dividing line, the method including: a low-viscosity resin coating step of applying a first liquid resin having a low viscosity to the surface of the wafer to cover portions constituting the devices; a high-viscosity resin coating step of applying a second liquid resin having a higher viscosity than the first liquid resin to the surface of the wafer after the low-viscosity resin coating step and overlaying the first liquid resin; and a resin curing step of curing the coated first liquid resin and second liquid resin To form a protective film ; a planarization step of planarizing the cured resin, thereby The protective film formed thereby enabling the wafer to be divided into individual device chips without damaging or injuring the wafer even if there are protrusions on the surface of the wafer, and solving the problem of debris directly adhering to the surface of the device chips and degrading the quality. , perform a grinding process of grinding the back surface of the wafer while holding the side on which the protective film is formed on a chuck table BRIEF DESCRIPTION OF THE DRAWINGS

[0014]

Figure 1

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Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of a wafer processing method configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0016] In FIG. 1(a), a wafer 10 processed by the wafer processing method of the present embodiment and a liquid resin coating device 20 (only a part is shown) are shown. The wafer 10 is a wafer formed of, for example, a silicon (Si) substrate. The wafer 10 is formed on a surface 10a in which a plurality of devices 12 are partitioned by a dicing planned line 14, and a plurality of bumps 16 are formed on each device 12 as partially enlarged and shown upward in the figure. The bump 16 is a protruding electrode for electrically connecting the device 12 to the outside, and is, for example, an alloy electrode mainly composed of lead and tin.

[0017] In the method for processing a wafer according to this embodiment, first, a low-viscosity resin coating step of applying a first liquid resin L1, which will be described below, to the surface 10a of the wafer 10 to cover the portions constituting the device 12, and after the low-viscosity resin coating step, a high-viscosity resin coating step of applying a second liquid resin L2 having a higher viscosity than the first liquid resin L1 to the surface 10a of the wafer 19 and laminating it on the first liquid resin L1 are performed.

[0018] More specifically, first, the above-described wafer 10 is conveyed to a liquid resin coating apparatus 20 shown in the figure. The liquid resin coating apparatus 20 includes at least a chuck table 21 and a support base 23. The holding surface 22 of the chuck table 21 is formed of a porous member having air permeability. The chuck table 21 is connected to a suction means (not shown), and by operating the suction means, a suction negative pressure is generated on the holding surface 22. An electric motor (not shown) is disposed inside the support base 23, and the chuck table 21 can be rotated together with the rotation shaft 24.

[0019] With the surface 10a side of the wafer 10 conveyed to the liquid resin coating apparatus 20 facing upward and the back surface 10b side facing downward, the wafer 10 is placed on the chuck table 21 of the liquid resin coating apparatus 20, and the above-described suction means is operated to suction-hold it on the holding surface 22.

[0020] As shown in FIG. 1(b), when the wafer 10 is sucked and held by the chuck table 21, the liquid resin supply nozzle 25 is positioned directly above the center of the wafer 10. Two types of liquid resin supply sources are connected to the liquid resin supply nozzle 25. More specifically, a first liquid resin supply source (not shown) that supplies a first liquid resin L1 with low viscosity and a second liquid resin supply source (not shown) that supplies a second liquid resin L2 with higher viscosity than the first liquid resin L1 are connected. As the first liquid resin L1 and the second liquid resin L2, for example, an epoxy resin that cures by irradiation with ultraviolet rays is adopted. A solvent is mixed in the first liquid resin L1 at a high ratio with respect to the second liquid resin L2. The first liquid resin L1 is a so-called low-viscosity liquid resin that has no stickiness with respect to the second liquid resin L2.

[0021] After the wafer 10 is sucked and held by the chuck table 21, as shown in FIG. 1(b), the electric motor of the support base 23 is operated to rotate the chuck table 21 together with the rotating shaft 24 in the direction indicated by the arrow R1. A predetermined amount of the first liquid resin L1 is supplied from the injection port 25a of the liquid resin supply nozzle 25 and applied onto the surface 10a of the wafer 10. The supply amount of the first liquid resin L1 from the injection port 25a is set to an amount that covers the portion constituting the device 12 by applying the first liquid resin L1 onto the surface 10a of the wafer 10. Thus, the low-viscosity resin coating process is completed.

[0022] As described above, after the first liquid resin coating process is performed, a second liquid resin supply source (not shown) is connected to the liquid resin supply nozzle 25. As shown in FIG. 1(c), the chuck table 21 is rotated together with the rotating shaft 24 in the direction indicated by the arrow R1, and a predetermined amount of the second liquid resin L2 is supplied from the injection port 25a of the liquid resin supply nozzle 25 and applied so as to overlap the first liquid resin L1 previously applied onto the surface 10a of the wafer 10. The supply amount of the second liquid resin L2 from the injection port 25a is set to an amount that covers the entire first liquid resin L1 applied onto the surface 10a of the wafer 10. Thus, the high-viscosity resin coating process is completed.

[0023] In the above-described low-viscosity resin coating process, since the viscosity of the applied first liquid resin L1 is low, the liquid resin wraps around fine convex portions such as bumps, and the surface 10a of the wafer 10 is coated without gaps. Further, as described above, by applying a second liquid resin L2 made of a liquid resin having a higher viscosity than the first liquid resin L1 so as to overlap the first liquid resin L1, while being compatible with the first liquid resin L1 having a low viscosity, the surface 10a of the wafer 10 is coated without gaps by the first liquid resin L1 and the second liquid resin L2.

[0024] Next, a resin curing process for curing the first liquid resin L1 and the second liquid resin L2 coated on the wafer 10 is performed. When performing the resin curing process, for example, as shown on the left side of FIG. 2, an ultraviolet irradiation means 26 is positioned directly above the wafer 10 held by the above-described liquid resin coating apparatus 20. Next, ultraviolet rays UV are irradiated from the ultraviolet irradiation means 26 toward the first liquid resin L1 and the second liquid resin L2 coated on the wafer 10. As a result, the first liquid resin L1 and the second liquid resin L2 are cured, and as shown on the right side of FIG. 2, a protective film L obtained by curing the first liquid resin L1 and the second liquid resin L2 is formed on the surface 10a of the wafer 10, and the resin curing process is completed. In the present embodiment, a resin that is cured by irradiating ultraviolet rays UV is selected as the first liquid resin L1 and the second liquid resin L2 to be coated on the surface 10a of the wafer 10, but the present invention is not limited to this. For example, the first liquid resin L1 and the second liquid resin L2 may be resins that cure over time, and in that case, the resin curing process corresponds to a process of waiting for a predetermined time until the first liquid resin L1 and the second liquid resin L2 applied on the wafer 10 are cured to form the protective film L after the resin coating process is completed. Further, when the first liquid resin L1 and the second liquid resin L2 are produced from water-soluble liquid resins, it is possible to add water to the highly viscous second liquid resin L2 to produce the low-viscosity liquid resin L1.

[0025] Although the above-described protective film L is formed to have a thickness sufficient to absorb the bumps 16 formed on the device 12, overall, it is affected by the unevenness of the surface 10a of the wafer 10 or the shrinkage during curing, etc. As shown on the right side of FIG. 2, the film thickness of the protective film L becomes non-uniform, and irregularities 18 are formed. In such a state, even if an ablation process is performed by irradiating the surface 10a side of the wafer 10 with a laser beam having an absorbent wavelength to form a dividing groove along the planned dividing line 14, the depth of the groove will not be constant, and there is a risk of defective processing. Also, even if the back surface 10b of the wafer 10 is ground and thinned while holding the protective film L side, there is a risk that the wafer 10 will be damaged or broken due to the influence of the irregularities 18. Therefore, in the present embodiment, a flattening process for flattening the protective film L in which the liquid resin has hardened as described above is performed.

[0026] FIG. 3 shows a cutting device 30 (only a part is shown) suitable for performing the flattening process of the present embodiment. The cutting device 30 includes a cutting unit 31 that is movably mounted in the vertical direction. The cutting unit 31 includes a moving base 32 that is moved in the vertical direction by a cutting feed means (not shown) and a spindle unit 33 mounted on the moving base 32. A support member 32a is mounted on the front surface of the moving base 32, and the spindle unit 33 is supported by the support member 32a.

[0027] The spindle unit 33 includes a spindle housing 33a mounted on the support member 32a, a rotating spindle 33b rotatably disposed in the spindle housing 33a, and a servo motor 33c as a drive source for rotationally driving the rotating spindle 33b. The lower end portion of the rotating spindle 33b projects downward beyond the lower end of the spindle housing 33a, and a disk-shaped tool mounting member 33d is provided on the lower end side thereof.

[0028] The tool holder member 33d for the cutting tool is provided with a tool mounting hole 33e that penetrates vertically through a part of the outer peripheral portion eccentric from the axis of rotation. A cutting tool 34 is inserted into the tool mounting hole 33e, and a tightening bolt 35 is screwed in and tightened from a female screw hole formed on the side of the tool holder member 33d for fastening and fixing. Note that the cutting tool 34 is formed in a rod shape from tool steel such as super alloy steel in the illustrated embodiment, and a cutting edge formed of diamond or the like is provided at the lower tip of the cutting tool 34. The cutting tool 34 mounted on the tool holder member 33d is rotated together with the tool holder member 33d when the rotating spindle 33b driven by the servo motor 33c rotates.

[0029] The cutting device 30 is provided with a chuck table mechanism 36. The chuck table mechanism 36 includes a disk-shaped chuck table 36a rotatably arranged. The holding surface of the chuck table 36a is formed of a breathable member and is connected to a suction source (not shown). The chuck table mechanism 36 includes a moving mechanism (not shown) housed inside the cutting device 30, and the chuck table 36a can be moved together with the cover member 36b in the direction indicated by the arrow R3. Note that the cutting device 30 shown in FIG. 3 sucks and holds the wafer 10 conveyed from the liquid resin coating device 20 on the chuck table 36a.

[0030] The cutting device 30 shown in FIG. 3 is generally configured as described above. Hereinafter, the planarization process of the present embodiment implemented using the above-described cutting device 30 will be described.

[0031] On the chuck table 36a of the cutting device 30 shown in FIG. 3, a wafer 10 is sucked and held with the side on which the protective film L is formed facing upward. The servo motor 33c described above is driven to rotate the tool mounting member 33d in the direction indicated by the arrow R2, and a cutting feed means (not shown) is operated to lower the tool mounting member 33d to a predetermined height for removing the unevenness 18 of the protective film L on the wafer 10. A moving means (not shown) is operated to move the chuck table mechanism 36 in the direction indicated by the arrow R3 in FIG. 3, and the chuck table 36a holding the wafer 10 is passed through the processing area below the tool mounting member 33d. By passing the chuck table 36a holding the wafer 10 through the processing area in this way, as shown on the lower side of FIG. 3, the unevenness 18 is removed from the protective film L formed on the wafer 10 and flattened, and the flattening process is completed.

[0032] Note that the flattening process of the present invention is not limited to being flattened by the above-described cutting device 30, and may be flattened by, for example, a polishing device or the like.

[0033] By adopting the wafer processing method including the above-described low-viscosity resin coating process, high-viscosity resin coating process, resin curing process, and flattening process, various dicing processes for dicing the wafer 10 into individual device chips, which will be described below, can be performed well. With reference to FIGS. 4, 5, and 13, an embodiment of the first dicing process will be described.

[0034] FIG. 4(a) shows an overall perspective view of a laser processing apparatus 40 suitable for first dicing, together with a wafer 10 on which a flat protective film L is formed based on the above-described wafer processing method. The laser processing apparatus 40 is disposed on a base 40a, and includes a laser irradiation means 41 for irradiating a laser beam onto the wafer 10 to be processed, a holding means 42 for holding the wafer 10, an imaging means 43 for imaging the wafer 10 held by the holding means 42, a feed means 44 for relatively feeding the laser irradiation means 41 and the holding means 42 in a processing feed direction, and relatively moving the imaging means 43 and the holding means 42, and a frame body 45 including a vertical wall portion 45a erected on the back side of the feed means 44 on the base 40a and a horizontal wall portion 45b extending horizontally from the upper end portion of the vertical wall portion 45a.

[0035] Inside the horizontal wall portion 45b of the frame body 45, an optical system (not shown) constituting the laser irradiation means 41 is accommodated. A condenser 41a constituting a part of the laser irradiation means 41 is disposed on the lower surface side of the tip end portion of the horizontal wall portion 45b. In the following description, the laser irradiation means 41 of the present embodiment is assumed to be capable of switching between irradiation with a laser beam having a wavelength that is transmissive to the wafer 10 and irradiation with a laser beam having a wavelength that is absorptive to the wafer 10. The imaging means 43 is disposed at a position adjacent to the condenser 41a in the X-axis direction shown by an arrow X in the figure. The imaging means 43 includes a normal imaging element (CCD) that images with visible light, an infrared irradiation means that irradiates the workpiece with infrared rays, an optical system that captures the infrared rays irradiated by the infrared irradiation means, and an imaging element (infrared CCD) that outputs an electrical signal corresponding to the infrared rays captured by the optical system.

[0036] As shown in Fig. 4(a), the holding means 42 includes a rectangular X-axis movable plate 42a mounted on the base 40a so as to be movable in the X-axis direction, a rectangular Y-axis movable plate 42b mounted on the X-axis movable plate 42a so as to be movable in the Y-axis direction orthogonal to the X-axis direction, a cylindrical support column 42c fixed to the upper surface of the Y-axis movable plate 42b, and a rectangular cover plate 42d fixed to the upper end of the support column 42c. A chuck table 42e extending upward through a long hole formed on the cover plate 42d is disposed on the cover plate 42d. The chuck table 42e is configured to be rotatable by a rotation driving means (not shown) housed in the support column 42c. A circular suction chuck 42f formed of a porous material having air permeability and extending substantially horizontally is disposed on the chuck table 42e. The suction chuck 42f is connected to a suction means (not shown) by a flow path passing through the support column 42c.

[0037] The feeding means 44 includes an X-axis feeding means 46 and a Y-axis feeding means 47. The X-axis feeding means 47 converts the rotational motion of the motor 47a into a linear motion via a ball screw 47b and transmits it to the X-axis movable plate 42a, and advances and retracts the X-axis movable plate 42a in the X-axis direction along a pair of guide rails 40b, 40b disposed along the X-axis direction on the base 40a. The Y-axis feeding means 47 converts the rotational motion of the motor 47a into a linear motion via a ball screw 47b and transmits it to the Y-axis movable plate 42b, and advances and retracts the Y-axis movable plate 42b in the Y-axis direction along a pair of guide rails 42g, 42g disposed along the Y-axis direction on the X-axis movable plate 42a.

[0038] The laser processing apparatus 40 shown in Fig. 4(a) has a configuration generally as described above, and the modification layer formation step of the first divided processing executed using this laser processing apparatus 40 will be described more specifically.

[0039] First, as shown in Fig. 4(a), with the protective film L side of the wafer 10 facing downward and the back surface 10b side of the wafer 10 facing upward, it is placed on the suction chuck 42f of the chuck table 42e and sucked and held.

[0040] The wafer 10 held by the chuck table 42e is moved under the imaging means 43 by operating the above-described feeding means 44 and imaged. The imaging means 43 is connected to a control means (not shown) and a display means, and by irradiating infrared rays from the back surface 10b side of the wafer 10 and imaging, a division planned line 14 to be irradiated with a laser beam formed on the side where the protective film L of the wafer 10 is formed is detected. The X coordinate and Y coordinate, which are the position information of the detected division planned line 14, are stored in the control means, and the chuck table 42e is rotated to align a predetermined division planned line 14 in the X-axis direction (alignment).

[0041] If the above alignment is carried out, the feeding means 44 is operated to move the chuck table 42e in the X-axis direction, and as shown in FIG. 4(b), the wafer 10 is positioned directly under the condenser 41a of the laser irradiation means 41. Next, while operating the above-described feeding means 44 and moving the condenser 41a in the Z-axis direction (vertical direction) indicated by the arrow Z in the figure, as shown in FIG. 4(c), the condensing point P1 of the laser beam LB1 having a wavelength that is transmissive to the wafer 10 irradiated by the laser irradiation means 41 is positioned inside the wafer 10 at a position corresponding to a predetermined division planned line 14 from the back surface 10b side and irradiated to form a modified layer 100. If the modified layer 100 is formed along the predetermined division planned line 14, the wafer 10 is indexed and fed in the Y-axis direction by the interval of the division planned line 14, and an unprocessed division planned line 14 adjacent in the Y-axis direction is positioned directly under the condenser 41a. Then, in the same manner as described above, the condensing point P1 of the laser beam LB1 is positioned inside the wafer 10 at a position corresponding to the division planned line 14, and the wafer 10 is processed and fed in the X-axis direction to form a modified layer 100.

[0042] Repeat the above-described laser processing, and feed the wafer 10 in the X-axis direction and the Y-axis direction to form the modified layer 100 along all the division planned lines 14 along the X-axis direction. Next, rotate the wafer 10 by 90 degrees to align the unprocessed division planned line 14 in the direction orthogonal to the division planned line 14 where the modified layer 100 has already been formed in the X-axis direction. Then, for each of the remaining division planned lines 14, position and irradiate the focus point P1 of the laser beam LB1 in the same manner as described above to form the modified layer 100 inside the wafer 10 along all the division planned lines 14 formed on the surface 10a of the wafer 10 (modified layer formation step).

[0043] Note that the processing conditions of the laser processing performed in the above-described modified layer formation step are set as follows, for example. Wavelength: 1342 nm Average output: 1.0 W Repetition frequency: 90 kHz Feed rate: 700 mm / second

[0044] If the above-described modified layer formation step is performed, the wafer 10 is transported to a grinding device 50 (only a part is shown) shown in Fig. 5(a). The grinding device 50 includes a chuck table 51 that can be rotated by a rotation driving means (not shown) and a grinding means 52. The grinding means 52 includes a rotary spindle 52a that is rotated by a rotation driving means (not shown), a wheel mount 52b attached to the lower end of the rotary spindle 52a, and a grinding wheel 52c attached to the lower surface of the wheel mount 52b. A plurality of grinding wheels 52d are annularly arranged on the lower surface of the grinding wheel 52c.

[0045] As shown in Fig. 5(a), if the wafer 10 transported to the grinding device 50 is sucked and held on the chuck table 51 with the side where the protective film L is formed facing downward and the back surface 10b side facing upward, the rotating spindle 52a of the grinding means 52 is rotated in the direction indicated by the arrow R4, for example, at 6000 rpm, and the chuck table 51 is rotated in the direction indicated by the arrow R5, for example, at 300 rpm. Then, the grinding feed means (not shown) is operated to lower the grinding wheel 52d in the direction indicated by the arrow R6 and bring it into contact with the back surface 10b of the wafer 10, and grinding feed is performed at a grinding feed rate of, for example, 1 μm / sec. At this time, grinding can be advanced while measuring the thickness of the wafer 10 with a contact-type measuring gauge (not shown), and by grinding until the predetermined finished thickness is reached, an external force is applied to the wafer 10, and as shown in Fig. 5(b), it is divided into individual device chips 12' along the modified layer 100 formed along the division planned line 14 (division step). Thus, the first division process is completed.

[0046] As described above, if the wafer 10 is divided into individual device chips 12' by the first division process, it is sent to a pickup process (not shown) as necessary. At that time, for example, as shown in Fig. 13(a), an annular frame F having an opening Fa capable of accommodating the wafer 10 is prepared, the wafer 10 is inverted, with the protective film L side facing upward and the back surface 10b side of the wafer 10 facing downward, and it is positioned at the center of the opening Fa and held via an adhesive tape T. Then, as shown in Fig. 13(b), by removing the protective film L, the surface 10a side of the wafer 10 divided into individual device chips 12' is exposed, and the device chips 12' can be easily picked up.

[0047] Since the above-described first dicing process is performed after the above-described low-viscosity resin coating process, high-viscosity resin coating process, resin curing process, and planarization process have been carried out in advance, the low-viscosity first liquid resin L1 wraps around projections such as bumps and coats them without gaps so as to enclose the projections. Further, since the high-viscosity second liquid resin L2 that is compatible with the first liquid resin L1 is applied and cured to form the protective film L, even when the above-described dicing process of grinding the back surface 10b side of the wafer 10 and dicing the wafer 10 into individual device chips 12' is performed after the modification layer forming process, grinding debris does not enter from the gap between the diced device chips 12' and the protective film L, and the bumps are prevented from being contaminated. Also, since the planarization process is carried out and the thickness of the protective film L is made uniform, even when the back surface 10b of the wafer 10 is ground with a grinding stone and the dicing process of dicing the wafer 10 into individual device chips 12' is performed, the wafer 10 is prevented from being damaged.

[0048] Next, a second dicing process that is carried out in combination with the above-described wafer processing method including the low-viscosity resin coating process, high-viscosity resin coating process, resin curing process, and planarization process will be described below with reference to FIGS. 6 to 9.

[0049] Also in the second dicing process, a wafer processing method including the above-described low-viscosity resin coating step, high-viscosity resin coating step, resin curing step, and planarization step is performed on the wafer 10. Next, without performing the above-described modified layer forming step, the wafer 10 with the protective film L formed thereon is transported to the above-described grinding apparatus 50 (see FIG. 5). Then, as shown in FIG. 6, the wafer 10 transported to the grinding apparatus 50 is sucked and held on the chuck table 51 with the side where the protective film L is formed facing downward and the back surface 10b side facing upward. The rotating spindle 52a of the grinding means 52 is rotated in the direction indicated by the arrow R4, for example, at 6000 rpm, and the chuck table 51 is rotated in the direction indicated by the arrow R5, for example, at 300 rpm. Then, the above-described grinding feed means is operated to lower the grinding wheel 52d in the direction indicated by the arrow R6 to bring it into contact with the back surface 10b of the wafer 10, and grinding is performed at a grinding feed rate of, for example, 1 μm / second. At this time, grinding can be advanced while measuring the thickness of the wafer 10 with a contact-type measuring gauge (not shown), and grinding is performed until the wafer 10 reaches the predetermined finished thickness (grinding step).

[0050] After performing the above-described grinding process and setting the thickness of the wafer 10 to the finished thickness, it is transported to the laser processing apparatus 40 described with reference to FIG. 4. Then, after placing the back surface 10b side of the wafer 10 upward on the chuck table 42e of the laser processing apparatus 40 and sucking and holding it, and after undergoing the above-described alignment, the wafer 10 is moved in the X-axis direction, and as shown in FIG. 7(a), the wafer 10 is positioned directly below the condenser 41a of the laser irradiation means 41. Next, while operating the above-described feeding means 44, as shown in FIG. 7(b), the condensing point P2 of the laser beam LB2 having a wavelength that is transmissive to the wafer 10 is positioned inside the wafer 10 corresponding to the predetermined division planned line 14 from the back surface 10b side of the wafer 10 and irradiated to form the modified layer 110. If the modified layer 110 is formed along the predetermined division planned line 14, the wafer 10 is indexed and fed in the Y-axis direction by the interval of the division planned line 14, and the unprocessed division planned lines 14 adjacent in the Y-axis direction are positioned directly below the condenser 41a. Then, in the same manner as described above, the condensing point P2 of the laser beam LB2 is positioned inside the position corresponding to the division planned line 14 of the wafer 10 and irradiated, and the wafer 10 is processed and fed in the X-axis direction to form the modified layer 110.

[0051] By repeating the above-described processing, the wafer 10 is processed and fed in the X-axis direction and the Y-axis direction to form the modified layer 110 along all the division planned lines 14 along the X-axis direction. Next, the wafer 10 is rotated 90 degrees to align the unprocessed division planned lines 14 in the direction orthogonal to the division planned lines 14 where the modified layer 110 has already been formed in the X-axis direction. Then, for each of the remaining division planned lines 14, in the same manner as described above, the condensing point P2 of the laser beam LB2 is positioned and irradiated to form the modified layer 110 inside the wafer 10 along all the division planned lines 14 formed on the surface 10a of the wafer 10 (modified layer forming step).

[0052] Note that the processing conditions of the laser processing performed in the modified layer forming step in the above-described second dicing process are set as follows, for example. Wavelength: 1064 nm Average output: 1.0 W Repetition frequency: 80 kHz Feed rate: 300 mm / sec

[0053] As described above, if the modified layer forming step is performed, the wafer 10 is unloaded from the laser processing apparatus 40, and as shown in FIG. 8, it is positioned at the center of the opening Fa of the annular frame F having an opening Fa capable of accommodating the previously prepared wafer 10, with the protective film L side facing upward and the back surface 10b side of the wafer 10 facing downward, and held via the adhesive tape T. Next, if the wafer 10 is held by the frame F, the protective film L is removed as shown in FIG. 9. After removing the protective film L, an external force G is applied so as to radially pull the adhesive tape T outward around the wafer 10, and the wafer 10 is divided into individual device chips 12' starting from the modified layer 110 (division step).

[0054] By performing the second division process described above, since the above-mentioned low-viscosity resin coating process, high-viscosity resin coating process, resin curing process, and planarization process are being performed, the same operational effects as those of the first division process described above can be achieved, and the wafer 10 can be satisfactorily divided into individual device chips 12'.

[0055] Furthermore, an embodiment of a third division process for dividing the wafer 10 into individual device chips, which is carried out in combination with a method for processing a wafer including the above-mentioned low-viscosity resin coating process, high-viscosity resin coating process, resin curing process, and planarization process, will be described with reference to FIG. 10.

[0056] In the third division process, after performing the above-described low-viscosity resin coating process, high-viscosity resin coating process, resin curing process, and planarization process, as shown in FIG. 10(a), the wafer 10 with the protective film L formed thereon is positioned at the center of the opening Fa of the annular frame F having an opening Fa capable of accommodating the wafer 10, and is held via the adhesive tape T with the protective film L side facing upward. Since the protective film L is formed on the surface 10a of the wafer 10 as described above, the wafer 10 shown in FIG. 10(a) is held in a state where the surface 10a side faces upward and the back surface 10b faces downward.

[0057] The above-described wafer 10 is transported to the laser processing apparatus 40 described with reference to FIG. 4 and is sucked and held by the chuck table 42e. The wafer 10 transported to the laser processing apparatus 40 is sucked and held by the chuck table 42e with the surface 10a covered with the protective film L facing upward. The wafer 10 held by the chuck table 42 is aligned as described above using the imaging means 43 disposed in the laser processing apparatus 40, the position of the division planned line 14 formed on the surface 10a is detected, and the wafer 10 is rotated by the rotation driving means for rotating the chuck table 42e to align a predetermined division planned line 14 in the X-axis direction. Information on the position of the detected division planned line 14 is stored in a control means (not shown).

[0058] Based on the position information detected by the above alignment, as shown in Fig. 10(a), the condenser 41a of the laser irradiation means 41 is positioned on the planned division line 14 in a predetermined direction, and the condensing point of the laser beam LB3 having a wavelength that is absorbent to the wafer 10 is positioned and irradiated on the surface 10a corresponding to the planned division line 14 of the wafer 10. At the same time, the wafer 10 is fed in the X-axis direction together with the chuck table 42e, and ablation processing is performed along the predetermined planned division line 14 of the wafer 10 to form a division groove 120 that breaks the protective film L and the wafer 10. If the division groove 120 is formed along the predetermined planned division line 14, the wafer 10 is indexed and fed in the Y-axis direction by the interval of the planned division line 14, and the unprocessed planned division line 14 adjacent in the Y-axis direction is positioned directly below the condenser 41a. Then, in the same manner as described above, the condensing point of the laser beam LB3 is positioned and irradiated on the planned division line 14 of the wafer 10, and the wafer 10 is fed in the X-axis direction to form the division groove 120. Similarly, the wafer 10 is fed in the X-axis direction and the Y-axis direction to form the division groove 120 along all the planned division lines 14 along the X-axis direction. Next, the wafer 10 is rotated by 90 degrees to align the unprocessed planned division line 14 in the direction orthogonal to the planned division line 14 where the division groove 120 has already been formed in the X-axis direction. Then, corresponding to each of the remaining planned division lines 14, the condensing point of the laser beam LB3 is positioned and irradiated in the same manner as described above to form the division groove 120 along all the planned division lines 14 formed on the surface 10a of the wafer 10 as shown in Fig. 10(b). Thus, the ablation processing step is completed.

[0059] Note that the processing conditions of the laser processing performed in the ablation processing step in the above third division processing are set as follows, for example. Wavelength: 355 nm Average output: 3.0 W Repetition frequency: 50 kHz Processing feed rate: 10 mm / sec

[0060] As shown in Fig. 10(b), since the dividing groove 120 breaks the protective film L and the wafer 10 to divide the wafer 10 into individual device chips 12’, the protective film L is removed as necessary to expose the surface 10a of the wafer 10 as shown in Fig. 10(c), so as to be in a state suitable for picking up the device chips 12’. The removal of the protective film L can be carried out by an appropriate method. For example, a solvent that dissolves the protective film L can be supplied to the surface, or the protective film L can be removed by attaching and peeling an adhesive tape having an appropriate adhesive force to the surface on which the protective film L is formed.

[0061] Furthermore, a fourth dividing process for dividing the wafer 10 into individual device chips, which is implemented in combination with a method for processing a wafer including the above-described low-viscosity resin coating process, high-viscosity resin coating process, resin curing process, and planarization process, will be described with reference to Figs. 11 to 13.

[0062] When implementing the fourth dividing process, before performing the above-described resin coating process on the wafer 10, a groove forming process for forming a groove in the planned dividing line 14 formed on the surface 10a of the wafer 10 is carried out. More specifically, first, the wafer 10 is transported to a cutting device 60 shown in Fig. 11. The cutting device 60 includes a chuck table (not shown) that sucks and holds the wafer 10, and a cutting means 62 that cuts the wafer 10 sucked and held by the chuck table. The chuck table is configured to be rotatable and includes a moving means (not shown) that feeds the wafer 10 together with the chuck table in the direction indicated by arrow X in the figure. The cutting means 62 includes a spindle housing 63, a spindle 64 disposed and held in the Y-axis direction indicated by arrow Y in the figure in the spindle housing 63, an annular cutting blade 65 (for example, 50 mm in diameter) held at the tip of the spindle 64, and a blade cover 66 that covers the cutting blade 65, and includes a Y-axis moving means (not shown) that indexes and feeds the cutting blade 65 in the Y-axis direction. The spindle 64 is rotationally driven by a spindle motor (not shown).

[0063] When implementing the groove forming process of this embodiment, first, the surface 10a of the wafer 10 is placed on the chuck table of the cutting device 60 with the surface facing upward and suction-held. The predetermined dividing line 14 of the wafer 10 is aligned in the X-axis direction, and alignment with the cutting blade 65 is performed. Next, the cutting blade 65 rotated at high speed (for example, 30,000 rpm) in the direction indicated by the arrow R7 is positioned on the dividing line 14 aligned in the X-axis direction, and a cut is made to a depth that does not reach the back surface 10b from the surface 10a side but reaches at least the finished thickness of the device 12. While supplying cutting water (for example, 2 liters / minute), the chuck table is processed and fed in the X-axis direction (for example, 50 mm / second) to form a groove 130 as shown in FIG. 11(b). Further, on the dividing line 14 adjacent in the Y-axis direction to the dividing line 14 where the groove 130 is formed and on the dividing line 14 where the groove 130 is not formed, the cutting blade 65 of the cutting means 62 is indexed and fed, and cutting processing for forming the groove 130 is performed in the same manner as above. By repeating these operations, the groove 130 is formed along all the dividing lines 14 along the X-axis direction. Next, the chuck table is rotated 90 degrees, the direction orthogonal to the direction in which the groove 130 was previously formed is aligned with the X-axis direction, and the above-described cutting processing is performed for all the dividing lines 14 newly aligned in the X-axis direction. As shown in FIG. 11(c), the groove 130 is formed along all the dividing lines 14 formed on the wafer 10, and the groove forming process is completed.

[0064] If the above-described groove forming step is carried out, then the above-described low-viscosity resin coating step, high-viscosity resin coating step, resin curing step, and planarization step are carried out. After the planarization step, the wafer 10 with the protective film L formed thereon is transported to the grinding apparatus 50 shown in FIG. 12. The grinding apparatus 50 is the same apparatus as the grinding apparatus 50 described with reference to FIG. 6, and the detailed description thereof is omitted. The side of the wafer 10 on which the protective film L is formed is placed on the chuck table 51 of the grinding apparatus 50 and sucked and held. As shown in FIG. 12, the back surface 10b is ground by the grinding wheel 52d to expose the groove 130, and the wafer 10 is finished to have the finished thickness of the device 12. As a result, as shown above the upper part of FIG. 13(a), the wafer 10 is divided into individual device chips 12', and the dividing step is completed.

[0065] As described above, in the state where the wafer 10 is divided into device chips 12', since the form of the wafer 10 is maintained by the protective film L, as shown in the figure, an annular frame F having an opening Fa capable of accommodating the wafer 10 is prepared. The wafer 10 is inverted so that the protective film L side is upward and the back surface 10b side of the wafer 10 is downward, and it is positioned at the center of the opening Fa and held via the adhesive tape T. Then, as shown in FIG. 13(b), by removing the protective film L, the surface 10a side of the wafer 10 divided into individual device chips 12' is exposed, and it becomes a state where it can be easily picked up. In this way, even when performing the fourth dividing process, by combining the above-described low-viscosity resin coating step, high-viscosity resin coating step, resin curing step, and planarization step, since the thickness of the protective film L is uniform, even when performing a dividing step of grinding the back surface 10b of the wafer 10 with a grinding wheel and dividing the wafer 10 into individual device chips 12', the wafer 10 is prevented from being damaged.

Explanation of Reference Numerals

[0066] 10: Wafer 10a: Front surface 10b: Back surface 12: Device 12’: Device chip 14: Scheduled cutting line 16: Bump 18: Concavo-convex 20: Liquid resin coating device 21: Chuck table 22: Holding surface 23: Support base 24: Rotation axis 25: Liquid resin supply nozzle 25a: Injection port 26: Ultraviolet irradiation means 30: Cutting device 31: Cutting unit 32: Moving base 32a: Support member 33: Spindle unit 33a: Spindle housing 33b: Rotating spindle 33c: Servo motor 33d: Tool holder member 33e: Tool mounting hole 34: Tool 35: Bolt 36: Chuck table mechanism 36a: Chuck table 36b: Cover member 40: Laser processing device 41: Laser irradiation means 42: Holding means 42a: X-axis direction movable plate 42b: Y-axis direction movable plate 42c: Support column 42d: Cover plate 42e: Chuck table 42f: Suction chuck 42g: Guide rail 43: Imaging means 44: Feeding means 45: Frame body 45a: Vertical wall part 45b: Horizontal wall part 50: Grinding device 51: Chuck table 52: Grinding means 52a: Rotating spindle 52b: Wheel mount 52c: Grinding wheel 52d: Grinding stone 60: Cutting device 62: Cutting means 63: Spindle housing 64: Spindle 65: Cutting blade 66: Blade cover 100, 110: Modified layer 120: Dividing groove 130: Groove L1: Low-viscosity resin L2: High-viscosity resin L: Protective film

Claims

A method for processing a wafer formed on a surface partitioned by a division planned line, wherein a plurality of devices having a plurality of protrusions on the surface are formed, comprising: A low-viscosity resin coating step of applying a first liquid resin with low viscosity to the surface of the wafer to cover the portions constituting the devices; After the low-viscosity resin coating step, a high-viscosity resin coating step of applying a second liquid resin with higher viscosity than the first liquid resin to the surface of the wafer and overlaying it on the first liquid resin; A resin curing step of curing the coated first liquid resin and second liquid resin to form a protective film; A planarization step of planarizing the protective film formed by the cured resin, and comprising: A method for processing a wafer, which comprises performing a grinding process of holding the side on which the protective film is formed on a chuck table and grinding the back surface of the wafer.

2. The method for processing a wafer according to claim 1, wherein the planarization step holds the back surface of the wafer on a chuck table, exposes the surface of the wafer, and cuts and planarizes the resin by cutting means provided with a cutting tool.

3. After the planarization step, a modified layer forming step of positioning and irradiating a condensing point of a laser beam having a wavelength permeable to the wafer from the back surface corresponding to the division planned line into the interior to form a modified layer along the division planned line; The method for processing a wafer according to claim 1 or 2, comprising: a dividing step of grinding the back surface of the wafer with a grinding stone to finish the wafer to a predetermined thickness and dividing the wafer from the modified layer into individual device chips.

4. After the planarization step, a grinding step of grinding the back surface of the wafer with a grinding stone to finish the wafer to a predetermined thickness; A modified layer forming step of positioning and irradiating a condensing point of a laser beam having a wavelength permeable to the wafer from the back surface corresponding to the division planned line into the interior to form a modified layer along the division planned line; The method for processing a wafer according to claim 1 or 2, comprising: a dividing step of applying an external force to the wafer and dividing the wafer into individual device chips.

5. The method for processing a wafer according to claim 1 or 2, comprising an ablation processing step of positioning and irradiating a condensing point of a laser beam having an absorbent wavelength to the surface of the wafer corresponding to the division planned line after the planarization step to perform ablation processing along the division planned line.

6. Before the low-viscosity resin coating step, a groove forming step of forming grooves with respect to the division planned lines formed on the surface of the wafer is performed. After the groove forming step, a low-viscosity resin coating step, a high-viscosity resin coating step, a resin curing step, and the planarization step are performed. Then, the back surface of the wafer is ground with a grinding wheel to finish the wafer to a predetermined thickness, while exposing the groove, and a dicing step of dicing the wafer into individual device chips is performed. The method for processing a wafer according to claim 1 or 2.

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