Wafer processing method

Abstract

To provide a wafer processing method capable of dividing a wafer into individual device chips without breaking or damaging the wafer even when a protrusion exists on a surface of the wafer.SOLUTION: A method for processing a wafer in which a plurality of devices are partitioned by division schedule lines on a surface includes a resin covering step, a resin curing step, a protective tape laying step, and a flattening step. The resin covering step covers a portion constituting a device by applying a liquid resin to a surface of the wafer. The resin curing step cures the covered liquid resin. The protective tape laying step lays a protective tape on an upper surface of the cured liquid resin. The flattening step flattens a surface of the protective tape.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for processing a wafer having a plurality of devices formed on its surface, the surface being partitioned by dividing lines. [Background technology]

[0002] Wafers with multiple devices such as ICs and LSIs formed on their surface, partitioned by planned division lines, are then separated into individual device chips by a dicing machine and used in electrical equipment such as mobile phones and personal computers.

[0003] In addition, a technology has been proposed in which a laser beam having a wavelength that is transparent to the wafer is irradiated at a focal point inside the wafer corresponding to the planned dividing line, forming a modified layer along the planned dividing line, and then grinding the back surface to form the desired thickness, and dividing the wafer into individual device chips (see Patent Document 1).

[0004] Also, a technology has been proposed in which grooves are formed on the surface of a wafer along the intended dividing lines, a protective tape is then laid on the surface of the wafer, and the back surface of the wafer is ground with a grinding wheel to finish the wafer to a predetermined thickness, while exposing the grooves on the back surface and dividing the wafer into individual device chips (see Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-078569 [Patent Document 2] Japanese Patent Application Publication No. 11-040520 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the technology described in Patent Document 1 is applied to a wafer on which unevenness, such as protruding electrodes called bumps, is formed on the surface of a device, there is a problem that the wafer may be damaged due to the bumps.

[0007] Furthermore, when implementing the technology described in Patent Document 2, there is a problem in that it is difficult to properly separate the wafer into individual device chips by grinding the back surface of the wafer without damaging the wafer on which bumps are formed on the surface of the device as described above.

[0008] The present invention has been made in view of the above-mentioned facts, and its main technical object is to provide a wafer processing method that can divide a wafer into individual device chips without breaking or damaging the wafer, even if protrusions are present on the surface of the wafer. [Means for solving the problem]

[0009] In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a method for processing a wafer on which a plurality of devices are formed by dividing lines, the method comprising: whole The resin coating process involves applying a liquid resin to the device to cover the components, and then hardening the coated liquid resin. to form a protective film a resin curing process; The protective film is removed while maintaining the protective film on the entire surface of the wafer. and a planarizing step of planarizing the surface of the protective tape. The protective film is removed after the dividing step of dividing the wafer into individual device chips along the dividing lines and before the wafer is picked up. A method for processing a wafer is provided.

[0010] In the planarization step, the back surface of the wafer is preferably held on a chuck table, the front surface of the wafer is exposed, and the protective tape is cut and planarized by a cutting means equipped with a cutting tool.

[0011] The method may include, in addition to carrying out the above-described wafer processing method, a modified layer forming step of irradiating a laser beam having a wavelength that is transparent to the wafer from a focal point positioned inside the back surface corresponding to the planned dividing lines to form a modified layer along the planned dividing lines, and a dividing step of grinding the back surface of the wafer with a grinding wheel to finish the wafer to a predetermined thickness and dividing the wafer into individual device chips from the modified layer.The method may also include, in addition to carrying out the above-described wafer processing method, a grinding step of grinding the back surface of the wafer with a grinding wheel to finish the wafer to a predetermined thickness, a modified layer forming step of irradiating a laser beam having a wavelength that is transparent to the wafer from a focal point positioned inside the back surface corresponding to the planned dividing lines to form a modified layer along the planned dividing lines, and a dividing step of applying an external force to the wafer to divide the wafer into individual device chips.

[0012] Furthermore, in the above-described wafer processing method, a groove forming step of forming grooves along the planned dividing lines formed on the front surface of the wafer may be carried out before the resin coating step, and after the groove forming step, a resin coating step, a resin hardening step, a protective tape laying step, and the planarization step may be carried out, after which the back surface of the wafer may be ground with a grinding wheel to finish the wafer to a predetermined thickness, and the grooves may be exposed on the back surface, and a dividing step may be carried out to divide the wafer into individual device chips. [Effects of the Invention]

[0013] The wafer processing method of the present invention is a method for processing a wafer on which a plurality of devices are formed on a surface that is partitioned by planned division lines, the method comprising: whole The resin coating process involves applying a liquid resin to the device to cover the components, and then hardening the coated liquid resin. to form a protective film a resin curing process; The protective film is removed while maintaining the protective film on the entire surface of the wafer. and a planarizing step of planarizing the surface of the protective tape. The protective film is removed after the dividing step of dividing the wafer into individual device chips along the dividing lines and before the wafer is picked up.Therefore, even if protrusions such as bumps are formed on the surface of the device, the protrusions can be buried with the liquid resin, and the surface of the protective tape that covers the protective film formed by the hardening of the liquid resin is flattened, thereby eliminating the effects of waviness due to unevenness on the protective film and variations in the thickness of the protective tape, and the back surface of the wafer can be ground with a grinding wheel without damaging the wafer, allowing it to be properly divided into individual device chips. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1A is a perspective view of a wafer as a workpiece and a liquid resin coating device, and FIG. 1B is a perspective view showing an embodiment of a resin coating step. [Figure 2] FIG. 10 is a perspective view showing an embodiment of a resin curing step. [Figure 3] FIG. 1 is a perspective view showing an embodiment of a protective tape installation work. [Figure 4] 1 is a perspective view illustrating an embodiment of a planarization step. [Figure 5] FIG. 1A is a perspective view of a laser processing device, FIG. 1B is a perspective view showing an embodiment of a modified layer forming step, and FIG. 1C is a cross-sectional view of the wafer shown in FIG. [Figure 6] FIG. 1A is a perspective view showing an embodiment of a dividing step for dividing a wafer into individual device chips from a modified layer, and FIG. 1B is a perspective view showing a wafer divided into individual device chips by the dividing step of FIG. [Figure 7] FIG. 10 is a perspective view showing an embodiment of a grinding step in which the back surface of the wafer is ground with a grinding wheel. [Figure 8] 7A is a perspective view showing an embodiment of a modified layer forming step performed on a wafer ground by the grinding step of FIG. 6, and FIG. 7B is a cross-sectional view of the wafer shown in FIG. [Figure 9] 9 is a perspective view showing a mode in which the wafer that has undergone the modified layer forming step shown in FIG. 8 is held by a frame. FIG. [Figure 10] FIG. 10 is a perspective view showing an embodiment of a dividing step in which an external force is applied to a wafer to divide it into individual device chips. [Figure 11]FIG. 1A is a perspective view showing an embodiment of a groove forming step, FIG. 1B is a cross-sectional view of the wafer shown in FIG. 1A, and FIG. 1C is a perspective view of the wafer on which grooves have been formed by the groove forming step. [Figure 12] FIG. 10 is a perspective view showing an embodiment of a dividing step in which the back surface of the wafer is ground with a grinding wheel to divide the wafer into individual device chips. [Figure 13] FIG. 1A is a perspective view showing how a wafer divided into individual device chips is held by a frame, and FIG. 1B is a perspective view showing how a protective film is removed from the wafer. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a wafer processing method according to the present invention will be described in detail with reference to the accompanying drawings.

[0016] 1(a) shows a wafer 10 to be processed by the wafer processing method of this embodiment, and a liquid resin coating apparatus 20 (only a portion of which is shown). The wafer 10 is formed, for example, from a silicon (Si) substrate. The wafer 10 has a surface 10a partitioned by planned division lines 14, on which a plurality of devices 12 are formed. As shown in an enlarged partial view at the top of the figure, each device 12 has a plurality of bumps 16 formed thereon. The bumps 16 are protruding electrodes for electrically connecting the devices 12 to the outside, and are, for example, alloy electrodes primarily composed of lead and tin.

[0017] In the wafer processing method of this embodiment, first, a resin coating step is performed in which a liquid resin L, described below, is applied to the surface 10a of the wafer 10 to cover the portions that constitute the device 12. More specifically, the wafer 10 is transported 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 material with breathability. 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 is capable of rotating the chuck table 21 together with a rotation shaft 24.

[0018] The wafer 10 transported to the liquid resin coating device 20 is placed on the chuck table 21 of the liquid resin coating device 20 with the front surface 10a facing upward and the back surface 10b facing downward, and the suction means is activated to hold the wafer 10 by suction on the holding surface 22.

[0019] As shown in FIG. 1(b), after the wafer 10 is suction-held on the chuck table 21, the liquid resin supply nozzle 25 is positioned directly above the center of the wafer 10. The electric motor of the support base 23 is operated to rotate the chuck table 21 together with the rotary shaft 24 in the direction indicated by the arrow R1. A predetermined amount of liquid resin L is supplied from the nozzle 25a of the liquid resin supply nozzle 25 and applied to the front surface 10a of the wafer 10. For example, an epoxy resin that hardens when irradiated with ultraviolet light is used as the liquid resin L. The supply of the liquid resin L from the nozzle 25a is not limited to one time, but may be multiple times. The amount of liquid resin L supplied from the nozzle 25a is set to an amount sufficient to coat the front surface 10a of the wafer 10 with the liquid resin L and to cover the portions that constitute the device 12. This completes the resin coating process.

[0020] Next, a resin curing step is performed to harden the liquid resin L coated on the wafer 10. To perform the resin curing step, for example, as shown on the left side of FIG. 2, an ultraviolet irradiation means 26 is positioned directly above the wafer 10 held in the liquid resin coating apparatus 20. Next, ultraviolet rays (UV) are irradiated from the ultraviolet irradiation means 26 toward the liquid resin L coated on the wafer 10. This hardens the liquid resin L, and as shown on the right side of FIG. 2, a protective film L' made of the hardened liquid resin L is formed on the front surface 10a of the wafer 10, completing the resin curing step. While a resin that hardens upon irradiation with ultraviolet rays (UV) is selected as the liquid resin L coated on the front surface 10a of the wafer 10 in this embodiment, the present invention is not limited thereto. For example, the liquid resin L may be a resin that hardens over time. In this case, the resin curing step corresponds to a step of waiting until the liquid resin L applied to the wafer 10 hardens after the resin coating step is completed.

[0021] Although the protective film L' described above is formed to a thickness sufficient to absorb the bumps 16 formed on the device 12, when viewed as a whole, the thickness of the protective film L' becomes non-uniform due to the influence of the irregularities 18 on the front surface 10a of the wafer 10 and the influence of shrinkage during hardening, etc., resulting in the formation of the irregularities 18. In this state, even if an attempt is made to thin the back surface 10b of the wafer 10 by grinding while holding the protective film L' side, the influence of the irregularities 18 may cause damage or breakage to the wafer 10. Therefore, in this embodiment, a protective tape laying step is performed in which a protective tape is laid on the upper surface of the protective film L' made of the cured liquid resin as described above, and a planarization step is performed in which the surface of the protective tape is planarized.

[0022] When carrying out the protective tape laying step, a protective tape T1 is prepared as shown in Fig. 3. The protective tape T1 is, for example, a backgrind tape used when performing a grinding process on a wafer. The backgrind tape is selected from, for example, polyethylene terephthalate (PET), ethylene-vinyl acetate copolymer (EVA), or a combination thereof, and has an adhesive formed on the side to be attached.

[0023] In the protective tape laying step, as shown in FIG. 3, a protective tape T1 is laid on the upper surface of the liquid resin L cured on the front surface 10a of the wafer 10, i.e., on the surface of the protective film L'. When laying the protective tape T1 on the protective film L', it is preferable to perform this in a reduced-pressure vacuum environment to prevent air or the like from entering between the protective film L' and the protective tape T1. When the protective tape T1 is laid in close contact with the protective film L', as shown on the right side of FIG. 3, unevenness 18' is formed on the protective tape T1 due to the influence of the unevenness 18 formed on the protective film L' and variations in the thickness of the protective tape T1. Therefore, in this embodiment, a planarization step is performed in which the protective tape T1 laid on the protective film L' as described above is cut and planarized.

[0024] 4 shows a cutting device 30 (only a part thereof is shown) suitable for carrying out the planarization step of this embodiment. The cutting device 30 is equipped with a cutting unit 31 that is mounted so as to be movable in the vertical direction. The cutting unit 31 is equipped with a movable base 32 that is moved in the vertical direction by a cutting feed means (not shown), and a spindle unit 33 mounted on the movable base 32. A support member 32a is mounted on the front surface of the movable base 32, and the spindle unit 33 is supported by the support member 32a.

[0025] The spindle unit 33 includes a spindle housing 33a mounted on the support member 32a, a rotary spindle 33b rotatably disposed in the spindle housing 33a, and a servo motor 33c as a drive source for driving the rotary spindle 33b to rotate. The lower end of the rotary spindle 33b protrudes 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.

[0026] The tool bit mounting member 33d has a tool bit mounting hole 33e that penetrates vertically through a portion of its outer periphery that is eccentric from the rotation axis. A tool bit 34 is inserted into the tool bit mounting hole 33e, and a tightening bolt 35 is threaded into an internally threaded hole formed on the side of the tool bit mounting member 33d to tighten and secure the tool bit. In the illustrated embodiment, the tool bit 34 is formed into a rod shape from tool steel such as a cemented carbide alloy, and a cutting edge formed of diamond or the like is provided at the lower tip of the tool bit 34. The tool bit 34 mounted on the tool bit mounting member 33d is rotated together with the tool bit mounting member 33d by the rotation of the rotating spindle 33b driven by the servo motor 33c.

[0027] The cutting device 30 is provided with a chuck table mechanism 36. The chuck table mechanism 36 is provided with a rotatably arranged, disk-shaped chuck table 36a. The holding surface of the chuck table 36a is formed of a breathable material and is connected to a suction source (not shown). The chuck table mechanism 36 is provided with a movement mechanism (not shown) housed inside the cutting device 30, which can move the chuck table 36a together with the cover member 36b in the direction indicated by arrow R3.

[0028] The cutting device 30 shown in FIG. 4 is generally configured as described above, and the planarization step of this embodiment, which is carried out using the above-described cutting device 30, will be described below.

[0029] The wafer 10 is placed on the chuck table 36a of the cutting device 30 shown in FIG. 4 and held by suction, with the protective tape T1 facing upward. The servo motor 33c is driven to rotate the tool holder 33d in the direction indicated by arrow R2, and a notched feed means (not shown) is operated to lower the wafer 10 to a predetermined height for cutting the irregularities 18' of the protective tape T1 on the wafer 10. The moving means (not shown) is operated to move the chuck table mechanism 36 in the direction indicated by arrow R3 in FIG. 4, causing the chuck table 36a holding the wafer 10 to pass through the processing area below the tool holder 33d. As the chuck table 36a holding the wafer 10 passes through the processing area in this manner, the irregularities 18' are removed and flattened from the protective tape T1 laid on the wafer 10, as shown in the lower part of FIG. 4, completing the planarization process.

[0030] The planarization step of the present invention is not limited to planarization using the cutting device 30 described above, but may be planarization using, for example, a polishing device or the like.

[0031] By employing the wafer processing method including the resin coating step, resin curing step, protective tape laying step, and planarization step described above, various dividing processes for dividing the wafer 10 into individual device chips, which will be described below, can be carried out effectively. A first embodiment of the dividing process will be described with reference to Figures 5, 6, and 13.

[0032] 5(a) shows a wafer 10 on which a protective tape T1 flattened based on the above-described wafer processing method has been laid, and an overall perspective view of a laser processing apparatus 40 suitable for the first dividing process. The laser processing apparatus 40 is arranged on a base 40a and includes a laser irradiation means 41 that irradiates a laser beam onto the wafer 10 to be processed, a holding means 42 that holds the wafer 10, an imaging means 43 that images the wafer 10 held by the holding means 42, a feeding means 44 that feeds the laser irradiation means 41 and the holding means 42 relatively for processing and also moves the imaging means 43 and the holding means 42 relatively, and a frame 45 that includes a vertical wall 45a erected on the far side of the feeding means 44 on the base 40a and a horizontal wall 45b extending horizontally from the upper end of the vertical wall 45a.

[0033] An optical system (not shown) that constitutes the laser irradiation means 41 is housed inside the horizontal wall portion 45b of the frame 45. A condenser 41a that constitutes part of the laser irradiation means 41 is disposed on the underside of the tip of the horizontal wall portion 45b. The imaging means 43 is disposed adjacent to the condenser 41a in the X-axis direction indicated by the arrow X in the figure. The imaging means 43 includes a normal imaging element (CCD) that captures images using visible light, 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.

[0034] As shown in FIG. 5(a), the holding means 42 includes a rectangular X-axis direction movable plate 42a mounted on a base 40a so as to be movable in the X-axis direction; a rectangular Y-axis direction movable plate 42b mounted on the X-axis direction movable plate 42a so as to be movable in the Y-axis direction perpendicular to the X-axis direction; a cylindrical support 42c fixed to the upper surface of the Y-axis direction movable plate 42b; and a rectangular cover plate 42d fixed to the upper end of the support 42c. A chuck table 42e is disposed on the cover plate 42d and extends upward through an elongated hole formed in the cover plate 42d. The chuck table 42e is rotatable by a rotation drive means (not shown) housed in the support 42c. A circular suction chuck 42f made of a breathable porous material and extending substantially horizontally is disposed on the chuck table 42e. The suction chuck 42f is connected to a suction means (not shown) via a flow path passing through the support 42c.

[0035] The feed means 44 includes an X-axis feed means 46 and a Y-axis feed means 47. The X-axis feed means 47 converts the rotational motion of the motor 47a into linear motion via a ball screw 47b and transmits the linear motion to the X-axis movable plate 42a, moving the X-axis movable plate 42a back and forth in the X-axis direction along a pair of guide rails 40b, 40b arranged on the base 40a along the X-axis direction. The Y-axis feed means 47 converts the rotational motion of the motor 47a into linear motion via a ball screw 47b and transmits the linear motion to the Y-axis movable plate 42b, moving the Y-axis movable plate 42b back and forth in the Y-axis direction along a pair of guide rails 42g, 42g arranged on the X-axis movable plate 42a along the Y-axis direction.

[0036] The laser processing apparatus 40 shown in FIG. 5(a) has a configuration generally as described above, and the modified layer formation step of the first dividing process, which is performed using this laser processing apparatus 40, will be described in more detail.

[0037] First, as shown in FIG. 5(a), the wafer 10 is placed on the suction chuck 42f of the chuck table 42e with the protective tape T1 side facing downward and the back surface 10b side of the wafer 10 facing upward, and is held by suction.

[0038] The wafer 10 held by the chuck table 42e is moved to a position directly below the imaging means 43 by operating the feeding means 44, and an image is taken of the wafer 10. The imaging means 43 is connected to a control means and a display means (not shown), and detects the dividing lines 14 formed on the front surface 10a of the wafer 10 and to be irradiated with a laser beam by irradiating the back surface 10b of the wafer 10 with infrared light and taking an image. The X and Y coordinates, which are position information of the detected dividing lines 14, are stored in the control means, and the chuck table 42e is rotated to align the predetermined dividing lines 14 in the X-axis direction (alignment).

[0039] After the above alignment is performed, the feeding means 44 is operated to move the chuck table 42e in the X-axis direction, and the wafer 10 is positioned directly below the condenser 41a of the laser irradiation means 41, as shown in FIG. 5(b). Next, the feeding means 44 is operated and the condenser 41a is moved in the Z-axis direction (up and down) indicated by the arrow Z in the figure, so that the focal point P1 of the laser beam LB1, which has a wavelength that is transparent to the wafer 10 and is irradiated by the laser irradiation means 41, is positioned inside a position corresponding to the predetermined dividing lines 14 from the back surface 10b side of the wafer 10, as shown in FIG. 5(c), and the modified layer 100 is formed. After the modified layer 100 is formed along the predetermined dividing lines 14, the wafer 10 is indexed and fed in the Y-axis direction by the distance corresponding to the dividing lines 14, and the unprocessed dividing lines 14 adjacent in the Y-axis direction are positioned directly below the condenser 41a. Then, in the same manner as described above, the focal point P1 of the laser beam LB1 is positioned inside the position corresponding to the planned dividing line 14 of the wafer 10 and irradiated, and the wafer 10 is processed and fed in the X-axis direction to form a modified layer 100.

[0040] The above-described laser processing is repeated, processing and feeding the wafer 10 in the X-axis direction and the Y-axis direction, to form modified layers 100 along all of the dividing lines 14 along the X-axis direction. Next, the wafer 10 is rotated 90 degrees, and the unprocessed dividing lines 14 perpendicular to the dividing lines 14 along which the modified layers 100 have already been formed are aligned in the X-axis direction. Then, the laser beam LB1 is irradiated to each of the remaining dividing lines 14 in the same manner as described above, with the focal point P1 of the laser beam LB1 positioned, to form modified layers 100 inside the wafer 10 along all of the dividing lines 14 formed on the front surface 10a of the wafer 10 (modified layer forming step).

[0041] The processing conditions for the laser processing carried out in the modified layer forming step are set, for example, as follows. Wavelength: 1342nm Average power: 1.0W Repetition frequency: 90kHz Feed speed: 700mm / sec

[0042] After the modified layer forming step described above has been performed, the wafer 10 is transferred to a grinding apparatus 50 (only a portion of which is shown) shown in Fig. 6(a). The grinding apparatus 50 includes a chuck table 51 that can be rotated by a rotary drive means (not shown), and grinding means 52. The grinding means 52 includes a rotary spindle 52a that can be rotated by a rotary drive 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, and a plurality of grinding stones 52d are arranged in an annular shape on the lower surface of the grinding wheel 52c.

[0043] 6(a), the wafer 10 transported to the grinding device 50 is suction-held on the chuck table 51 with the side on which the protective tape T1 is formed facing downward and the back surface 10b facing upward. Then, the rotating spindle 52a of the grinding means 52 is rotated in the direction indicated by arrow R4 at, for example, 6000 rpm, and the chuck table 51 is rotated in the direction indicated by arrow R5 at, for example, 300 rpm. Then, the grinding feed means (not shown) is operated to lower the grinding wheel 52d in the direction indicated by arrow R6, bringing 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 / sec. At this time, grinding can be carried out 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 the wafer 10 is divided into individual device chips 12' along the modified layers 100 formed along the planned division lines 14, as shown in Figure 6(b) (division step). This completes the first division process.

[0044] As described above, once the wafer 10 has been divided into individual device chips 12' by the first dividing process, it is sent to a pick-up process (not shown) as necessary. For example, as shown in FIG. 13(a), an annular frame F having an opening Fa large enough to accommodate the wafer 10 is prepared, and the wafer 10 is inverted and positioned in the center of the opening Fa with the protective tape T1 facing upward and the back surface 10b of the wafer 10 facing downward, and held in place via adhesive tape T2. Then, as shown in FIG. 13(b), the protective tape T1 and protective film L' are removed, exposing the front surface 10a of the wafer 10 divided into the individual device chips 12', allowing for easy pick-up.

[0045] Since the first division process described above is carried out after the resin coating process, resin hardening process, protective tape laying process, and planarization process described above have been carried out, even if protrusions such as bumps 16 are formed on the surface of the device 12, the protrusions can be buried with the liquid resin L, and by flattening the surface of the protective tape T1 that covers the protective film L' formed by the hardening of the liquid resin L, the effects of unevenness 18 on the protective film L' and waviness due to variations in the thickness of the protective tape T1 can be eliminated, and the back surface 10b of the wafer 10 can be ground with a grinding wheel without damaging the wafer 10, allowing the wafer 10 to be properly divided into individual device chips 12'.

[0046] Next, the second dividing process, which is carried out in combination with the wafer processing method including the above-mentioned resin coating process, resin curing process, protective tape laying process, and planarization process, will be described below with reference to Figures 7 to 10.

[0047] In the second dividing process, the wafer 10 is also subjected to the wafer processing method including the resin coating step, resin curing step, protective tape laying step, and planarization step described above. Next, the wafer 10 with the protective tape T1 laid on the protective film L' is transported to the grinding device 50 (see FIG. 6) without undergoing the modified layer forming step. Then, as shown in FIG. 7, the wafer 10 transported to the grinding device 50 is suction-held on the chuck table 51 with the side with the protective tape T1 facing downward and the back surface 10b facing upward. The rotating spindle 52a of the grinding means 52 is rotated in the direction indicated by arrow R4 at, for example, 6000 rpm, and the chuck table 51 is rotated in the direction indicated by arrow R5 at, for example, 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 so that it contacts the back surface 10b of the wafer 10, and the grinding is fed at a grinding feed rate of, for example, 1 μm / sec. At this time, the grinding can be progressed while measuring the thickness of the wafer 10 with a contact-type measuring gauge (not shown), and the wafer 10 is ground until it reaches the predetermined finished thickness (grinding process).

[0048] After the above-described grinding process is performed to adjust the thickness of the wafer 10 to the finished thickness, the wafer 10 is transported to the laser processing apparatus 40 described with reference to FIG. 5. Then, the wafer 10 is placed on the chuck table 42e of the laser processing apparatus 40 with the back surface 10b side facing upward and held by suction. After the above-described alignment, the wafer 10 is moved in the X-axis direction to be positioned directly below the condenser 41a of the laser irradiation means 41, as shown in FIG. 8(a). Next, the feeding means 44 is operated, and the laser irradiation means 41 irradiates the wafer 10 with a laser beam LB2 having a wavelength that is transparent to the wafer 10, positioning the focal point P2 at a position inside the predetermined dividing line 14 from the back surface 10b side of the wafer 10, thereby forming a modified layer 110. Once the modified layer 110 has been formed along the predetermined dividing lines 14, the wafer 10 is indexed and fed in the Y-axis direction by the distance corresponding to the dividing lines 14, and the adjacent unprocessed dividing lines 14 in the Y-axis direction are positioned directly below the condenser 41a. Then, in the same manner as described above, the focal point P2 of the laser beam LB2 is positioned inside the position corresponding to the dividing lines 14 on the wafer 10 and irradiated, and the wafer 10 is processed and fed in the X-axis direction to form the modified layer 110.

[0049] By repeating the above-described processing, the wafer 10 is processed and fed in the X-axis direction and the Y-axis direction, and modified layers 110 are formed along all of the dividing lines 14 along the X-axis direction. Next, the wafer 10 is rotated 90 degrees, and the unprocessed dividing lines 14 perpendicular to the dividing lines 14 along which the modified layers 110 have already been formed are aligned in the X-axis direction. Then, the laser beam LB2 is irradiated to each of the remaining dividing lines 14 in the same manner as described above, with the focal point P2 of the laser beam LB2 positioned, to form modified layers 110 inside the wafer 10 along all of the dividing lines 14 formed on the front surface 10a of the wafer 10 (modified layer forming step).

[0050] The processing conditions for the laser processing carried out in the modified layer forming step in the second dividing process are set, for example, as follows. Wavelength: 1064nm Average power: 1.0W Repetition frequency: 80kHz Feed speed: 300mm / sec

[0051] After the modified layer forming step is performed as described above, the wafer 10 is carried out from the laser processing apparatus 40, and as shown in FIG. 10 , the wafer 10 is positioned in the center of an annular frame F having an opening Fa large enough to accommodate the wafer 10, with the protective tape T1 facing upward and the back surface 10b of the wafer 10 facing downward, and is held in place via adhesive tape T2. Next, as shown in FIG. 10 , the protective film L′ and protective tape T1 are removed from the front surface 10a of the wafer 10. After the protective film L′ and protective tape T1 are removed, an external force G is applied so as to pull the adhesive tape T2 radially outward from the center of the wafer 10, and the wafer 10 is divided into individual device chips 12′ using the modified layer 110 of the wafer 10 as the division starting point (dividing step).

[0052] By carrying out the second dividing process described above, the resin coating process, resin curing process, protective tape laying process, and planarization process are also carried out, so that the same effects as those of the first dividing process described above can be achieved, and the wafer 10 can be appropriately divided into individual device chips 12'.

[0053] Furthermore, an embodiment of a third dividing process for dividing the wafer 10 into individual device chips, which is carried out in combination with a wafer processing method including the above-mentioned resin coating process, resin curing process, protective tape laying process, and planarization process, will be described with reference to Figures 11 to 13.

[0054] When carrying out the third dividing process, a groove forming step is carried out on the wafer 10 to form grooves along the dividing lines 14 formed on the front surface 10a of the wafer 10 before carrying out the resin coating step. More specifically, the wafer 10 is first transported to a cutting device 60 (only a portion of which is shown) shown in FIG. 11. The cutting device 60 includes a chuck table (not shown) that holds the wafer 10 by suction, and cutting means 62 that cuts the wafer 10 held by suction on the chuck table. The chuck table is rotatable and includes moving means (not shown) that feeds the wafer 10 together with the chuck table for processing in the direction indicated by arrow X in the figure. The cutting means 62 includes a spindle housing 63, a spindle 64 disposed in and held by the spindle housing 63 in the Y-axis direction indicated by the arrow Y in the figure, an annular cutting blade 65 (e.g., 50 mm in diameter) held at the tip of the spindle 64, and a blade cover 66 that covers the cutting blade 65, and also includes Y-axis moving means (not shown) that indexes and feeds the cutting blade 65 in the Y-axis direction. The spindle 64 is driven to rotate by a spindle motor (not shown).

[0055] In carrying out the groove forming step of this embodiment, first, the wafer 10 is placed on the chuck table of the cutting device 60 with the front surface 10a facing upward and held by suction, and a predetermined division run 14 of the wafer 10 is aligned in the X-axis direction and aligned with the cutting blade 65. Next, the cutting blade 65, rotating at high speed (e.g., 30,000 rpm) in the direction indicated by arrow R7, is positioned on the division line 14 aligned in the X-axis direction and cuts from the front surface 10a to a depth that does not reach the back surface 10b but reaches at least the finished thickness of the device 12. While supplying cutting water to the cutting position (e.g., 2 liters / minute), the chuck table is moved in the X-axis direction (e.g., 50 mm / second) to form a groove 130 as shown in FIG. Furthermore, the cutting blade 65 of the cutting means 62 is indexed and fed onto a dividing line 14 adjacent in the Y-axis direction to the dividing line 14 on which the groove 130 has been formed and on which no groove 130 has been formed, and cutting is performed in the same manner as above to form the grooves 130. By repeating these steps, grooves 130 are formed along all dividing lines 14 along the X-axis direction. Next, the chuck table is rotated 90 degrees, and the direction perpendicular to the direction in which the grooves 130 were previously formed is aligned with the X-axis direction, and the above-mentioned cutting is performed on all dividing lines 14 newly aligned with the X-axis direction, so that grooves 130 are formed along all dividing lines 14 formed on the wafer 10 as shown in FIG. 11(c), completing the groove forming step.

[0056] After the groove forming step, the resin coating step, resin curing step, protective tape laying step, and planarization step are performed. After the planarization step, the wafer 10 on which the protective film L' and protective tape T1 are formed is transported to a grinding apparatus 50 shown in FIG. 12. The grinding apparatus 50 is the same as the grinding apparatus 50 described with reference to FIG. 6, and detailed description thereof will be omitted. The side of the wafer 10 on which the protective tape T1 is laid is placed on the chuck table 51 of the grinding apparatus 50 and held by suction. As shown in FIG. 12, the back surface 10b is ground with a grinding wheel 52d to expose the grooves 130, and the wafer 10 is ground to the finished thickness of the device 12. As a result, the wafer 10 is divided into individual device chips 12' as shown in the upper part of FIG. 13(a), completing the division step.

[0057] As described above, when the wafer 10 is divided into device chips 12′, the shape of the wafer 10 is maintained by the protective film L′ and the protective tape T1, so as shown in the figure, an annular frame F having an opening Fa capable of accommodating the wafer 10 is prepared, and the wafer 10 is inverted so that the protective tape T1 side faces upward and the back surface 10b side of the wafer 10 faces downward, and positioned in the center of the opening Fa and held in place by adhesive tape T2. Then, as shown in Figure 13(b), by removing the protective film L′ and the protective tape T1, the front surface 10a of the wafer 10 divided into individual device chips 12′ is exposed, allowing the chips to be easily picked up. In this way, even when the third dividing process is performed, the thickness of the layer consisting of the protective film L' and the protective tape T1 is made uniform by combining the above-mentioned resin coating process, resin hardening process, protective tape laying process, and planarization process, so that even when a dividing process is performed in which the back surface 10b of the wafer 10 is ground with a grinding wheel and the wafer 10 is divided into individual device chips 12', the same effects as the above-mentioned first and second dividing processes can be achieved. [Explanation of symbols]

[0058] 10: Wafer 10a: surface 10b: Back side 12: Device 12': Device chip 14: Planned division line 16: Bump 18, 18': Uneven 20: Liquid resin coating device 21: Chuck table 22: Holding surface 23: Support base 24: Rotation axis 25: Liquid resin supply nozzle 25a: Nozzle 26: Ultraviolet irradiation means 30: Cutting equipment 31: Cutting unit 32: Mobile base 32a: Support member 33: Spindle unit 33a: Spindle housing 33b: Rotating spindle 33c: Servo motor 33d: Tool holder 33e: Tool mounting hole 34: Byte 35: Bolt 36: Chuck table mechanism 36a: Chuck table 36b: Cover member 40: Laser processing equipment 41: Laser irradiation means 42: Holding means 42a: X-axis movable plate 42b: Y-axis movable plate 42c: Post 42d: Cover plate 42e: Chuck table 42f: Suction chuck 42g: Guide rail 43: Imaging means 44:Transportation means 45:Frame body 45a: Vertical wall section 45b:Horizontal wall part 50: Grinding equipment 51: Chuck table 52: Grinding means 52a: Rotating spindle 52b: Wheel mount 52c: Grinding wheel 52d: Grinding wheel 60: Cutting equipment 62: Cutting means 63: Spindle housing 64: Spindle 65: Cutting blade 66: Blade cover 100, 110: Modified layer 130: Groove L: Liquid resin L': Protective film T1: Protective tape T2: adhesive tape

Claims

1. 1. A method for processing a wafer having a plurality of devices formed on a surface partitioned by planned division lines, comprising: a resin coating step of applying a liquid resin to the entire surface of the wafer to cover the portions that constitute the device; a resin curing step of curing the coated liquid resin to form a protective film; a protective tape laying step of laying a protective tape on the upper surface of the protective film while maintaining the protective film on the entire surface of the wafer; a planarization step of planarizing the surface of the protective tape; The present invention is configured to include: The method for processing a wafer, wherein the protective film is removed after a dividing step of dividing the wafer along the dividing lines into individual device chips and before the wafer is picked up.

2. 2. The wafer processing method according to claim 1, wherein the planarization step comprises holding the back surface of the wafer on a chuck table, exposing the front surface of the wafer, and cutting the protective tape with cutting means having a cutting tool to flatten the wafer.

3. a modified layer forming step of, after the planarization step, irradiating the wafer with a laser beam having a wavelength that is transparent to the wafer from a focal point positioned inside the wafer from the rear surface corresponding to the planned dividing lines to form a modified layer along the planned dividing lines; 3. The wafer processing method according to claim 1, further comprising a dividing step of grinding the back surface of the wafer with a grinding wheel to finish the wafer to a predetermined thickness and dividing the wafer into individual device chips at the modified layer.

4. a grinding step in which the back surface of the wafer is ground with a grinding wheel after the planarization step to finish the wafer to a predetermined thickness; a modified layer forming step of irradiating the wafer with a laser beam having a wavelength that is transparent to the wafer from a focal point positioned inside the wafer from the rear surface corresponding to the planned dividing lines to form a modified layer along the planned dividing lines; 3. The wafer processing method according to claim 1, further comprising a dividing step of applying an external force to the wafer to divide the wafer into individual device chips.

5. Before the resin coating step, a groove forming step is carried out in which grooves are formed along the dividing lines formed on the surface of the wafer; 3. The wafer processing method according to claim 1 or 2, wherein after the groove forming step, a resin coating step, a resin hardening step, a protective tape laying step, and the planarization step are carried out, and then a dividing step is carried out in which the back surface of the wafer is ground with a grinding wheel to finish the wafer to a predetermined thickness, the grooves are exposed on the back surface, and the wafer is divided into individual device chips.

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