Processing method of workpiece

Abstract

The present invention provides a method for processing a workpiece. When performing plasma etching on a wafer having bumps formed on the front side, the entire front side of the wafer is covered with a resin film. The method includes: a holding step of holding the workpiece with the front side of the workpiece facing down so as to face the upper surface side of a stage provided with a curable resin having fluidity; a covering step of moving the workpiece downward and pressing the front side of the workpiece against the curable resin, so that the curable resin enters the gap between the bumps and the front side and the bumps are buried in the curable resin, thereby covering the entire front side of the workpiece with the curable resin; a hardening step of hardening the curable resin to form a resin film; a laser beam irradiation step of removing the resin film on each dicing predetermined line; and a dicing step of supplying a plasma gas to the workpiece and dicing the workpiece into individual device chips along each dicing predetermined line using the resin film as a mask.

Description

Technical Field

[0001] The present invention relates to a method for processing a workpiece provided with a plurality of bumps. Background Art

[0002] Device chips are generally mounted in electronic devices such as mobile phones and computers. In order to manufacture device chips, for example, first, a plurality of dicing lines are set in a grid pattern on the front side of a wafer formed of a semiconductor such as silicon, and devices are formed in each region divided by the plurality of dicing lines.

[0003] Then, after thinning the back side of the wafer to a predetermined thickness using a grinding device, the wafer is cut along each dicing line using a cutting device. Thus, the wafer is divided along the dicing lines, and device chips are manufactured.

[0004] A cutting device generally has a cutting unit that includes a cylindrical main shaft, a drive motor connected to one end side of the main shaft, and an annular cutting tool mounted on the other end side of the main shaft. As the cutting tool, for example, a hub-type cutting tool in which abrasive grains are fixed by an electroplated layer formed on an annular aluminum base (for example, refer to Patent Document 1) is used.

[0005] However, when cutting a wafer using a cutting tool, chipping, cracks, etc. are likely to be formed on the front side of the wafer. If chipping, cracks, etc. are formed, the flexural strength of the device chip is reduced, and thus there is a problem of deterioration in the quality of the device chip.

[0006] Therefore, a plasma cutting method (for example, refer to Patent Document 2) has been developed and put into practical use, which cuts a wafer into individual device chips by performing plasma etching on the wafer instead of cutting the wafer using a cutting tool.

[0007] In order to divide a wafer by the plasma cutting method, first, a resist film made of a photosensitive organic substance is used to cover the front side of the wafer using a spin coater. The spin coater has, for example, a chuck table including a holding surface for attracting and holding the wafer. A rotation drive source such as a drive motor is connected to the side of the chuck table opposite to the holding surface.

[0008] In order to cover the front side of the wafer with the resist film, first, the back side of the wafer is held by the holding surface. Then, in a state where the chuck table is rotated by the rotation drive source, a liquid resist material containing a photosensitive organic substance, a solvent, etc. is dropped onto the front side of the wafer. The resist material spreads in the outer peripheral direction of the wafer due to centrifugal force and covers the front side of the wafer. Then, when the resist material is dried, the solvent evaporates, and the front side of the wafer is covered with the resist film.

[0009] Next, a resist film located on the division predetermined line is removed using an exposure device, a developing device, etc., thereby patterning the resist film. Then, the resist film is used as a mask, and plasma etching is performed on the wafer. As a result, the wafer is divided into individual device chips.

[0010] In addition, conventionally, in order to mount a device chip on an electronic device, it is necessary to seal a device chip and lead terminals connected to each other by wires with resin in such a way that the lead terminals are exposed, thereby forming a package such as a QFN (Quad Flat Noleaded package). However, in recent years, miniaturization, thinning, and lightening of device chips mounted on electronic devices have been required.

[0011] In order to meet this requirement, a wafer-level chip size package (hereinafter referred to as WL-CSP) in which a device chip and lead terminals are not connected by wires and a part of the device chip is exposed has been developed. WL-CSP can achieve miniaturization etc. compared with packages such as QFN.

[0012] In a wafer for manufacturing WL-CSP, a wiring layer is formed on the front side of the wafer, a resin film is formed so as to partially cover the wiring layer, and a plurality of bumps (i.e., protruding electrodes) electrically connected to the wiring layer are formed to protrude from the resin film. In the case of manufacturing WL-CSP, attempts have also been made to perform plasma etching on the wafer to divide the wafer into individual WL-CSPs (for example, refer to Patent Document 3).

[0013] Patent Document 1: Japanese Patent Application Laid-Open No. 2000-87282

[0014] Patent Document 2: Japanese Patent Application Laid-Open No. 2006-114825

[0015] Patent Document 3: Japanese Patent Application Laid-Open No. 2017-103330

[0016] However, for a wafer for manufacturing WL-CSP, when a resin film such as a resist film is formed using a spin coater, during the process in which the liquid resin material expands due to centrifugal force, the flow of the resin material toward the outer peripheral side of the wafer is sometimes blocked by the bumps.

[0017] In addition, it is difficult for the resin material to enter the gaps around the bumps. Therefore, it is difficult to cover the entire front side with the resin film. Along with such difficulty in covering, there is also a problem of reduced yield. Summary of the Invention

[0018] The present invention has been completed in view of the above problems, and an object thereof is to cover the entire front surface of a wafer with a resin film when the wafer having bumps formed on the front side is subjected to plasma etching to divide the wafer.

[0019] According to one aspect of the present invention, there is provided a method for processing a workpiece, wherein the workpiece has a plurality of bumps provided in each of a plurality of regions divided by a plurality of division lines set on the front side of the workpiece, and the method for processing the workpiece includes the following steps: a holding step of holding the workpiece with the front surface of the workpiece facing downward so as to face the upper surface side of a stage provided with a curable resin having fluidity; a covering step of moving the workpiece downward and pressing the front surface side of the workpiece against the curable resin, so that the curable resin enters the gap between the bumps and the front surface and the bumps are buried in the curable resin, thereby covering the entire front surface of the workpiece with the curable resin; a hardening step of hardening the curable resin to form a resin film; a laser beam irradiation step of irradiating the resin film with a laser beam having a wavelength absorbed by the resin film along each of the division lines after the hardening step to remove the resin film on each of the division lines; and a dividing step of supplying a plasma gas to the workpiece after the laser beam irradiation step and dividing the workpiece into individual device chips along each of the division lines using the resin film as a mask.

[0020] Preferably, the method for processing the workpiece further includes a thinning step of cutting the surface of the resin film with a cutting tool to thin the resin film before the laser beam irradiation step.

[0021] In the covering step of the processing method according to one aspect of the present invention, the front surface side of the workpiece is pressed against a curable resin having fluidity, so that the curable resin enters the gap between the bumps and the front surface and the bumps are buried in the curable resin, thereby covering the entire front surface of the workpiece with the curable resin.

[0022] In this way, the bumps on the front surface side are pressed against the curable resin having fluidity without using centrifugal force. Therefore, even if the bumps are provided so as to protrude from the device, the entire front surface side of the wafer including the periphery of the bumps can be covered with a curable resin having a uniform thickness.

[0023] By using the resin film obtained by hardening the curable resin as a mask to perform plasma etching on the front surface side of the wafer, the wafer is divided into individual device chips. Thereby, the yield can be improved as compared with the case of forming a resist film using a spin coater. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1(A) is a perspective view of the wafer. Figure 1 (B) is a cross-sectional view of the wafer.

[0025] Figure 2 It is a diagram showing the resin supply process.

[0026] Figure 3 It is a diagram showing the holding process.

[0027] Figure 4 It is a diagram showing the covering process.

[0028] Figure 5 It is a diagram showing the hardening process.

[0029] Figure 6 It is a diagram showing the thinning process.

[0030] Figure 7 (A) is a diagram showing the laser beam irradiation process. Figure 7 (B) is a cross-sectional view of the wafer etc. after the laser beam irradiation process. Figure 7 (C) is an enlarged view of the vicinity of the groove.

[0031] Figure 8 (A) is a diagram showing the dicing process. Figure 8 (B) is a cross-sectional view of the wafer etc. after the dicing process. Figure 8 (C) is a cross-sectional view of the WL-CSP.

[0032] Figure 9 It is a flowchart of the wafer processing method.

[0033] Reference numeral description

[0034] 11: Wafer (workpiece); 11a: Front side; 11b: Back side; 11c: Groove; 13: Dicing predetermined line (street); 15: Device; 15a: Flat surface; 15b: Bump; 15c: Gap; 17: Ultraviolet curable resin; 19: Resin film; 19a: Surface; 19b: Groove; 21: Protective tape; 23: Wafer unit; 25: WL-CSP; 10: Bonding device; 12: Stage; 12a: Lower surface; 12b: Upper surface; 14a: UV lamp; 14b: Thin plate; 16: Nozzle; 18: Resin supply source; 20: Transfer device; 22: Housing; 22a: Recess; 22b: First flow path; 22c: Second flow path; 24: Porous plate; 24a: One surface; 26: Suction source; 28: Arm; 30: Tool cutting device; 32: Chuck table; 32a: Holding surface; 34: Tool cutting unit; 34a: Spindle housing; 34b: Spindle; 34c: Grinding wheel mount; 36: Tool wheel; 38: Tool tool; 38a: Base; 38b: Cutting edge; 40: Hammer part; 50: Laser processing device; 52: Processing head; 54: Plasma etching device; L: Laser beam; P: Etching gas. Detailed implementation mode

[0035] An implementation mode of one aspect of the present invention will be described with reference to the accompanying drawings. In the present implementation mode, a wafer (workpiece) 11 for manufacturing WL-CSP is processed to manufacture WL-CSP. Figure 1 (A) of is a perspective view of the wafer 11, Figure 1 (B) of is a cross-sectional view of the wafer 11.

[0036] The wafer 11 is a disk-shaped silicon wafer having a thickness of about 500 μm to 1000 μm. In addition, the material, shape, structure, size, etc. of the wafer 11 are not limited. A wafer 11 formed of a semiconductor material other than silicon such as silicon carbide (SiC) may also be used.

[0037] On the front side 11a of the wafer 11, a plurality of dicing predetermined lines (streets) 13 arranged in a grid pattern are set. Devices 15 are formed in each region divided by the plurality of dicing predetermined lines 13.

[0038] A part of the front side 11a of the device 15 is a flat surface 15a, and a plurality of bumps (protrusion electrodes) 15b are fixed to the device 15 so as to protrude from the flat surface 15a. The bumps 15b in the present implementation mode are substantially spherical, but the bumps 15b may also be prismatic or cylindrical.

[0039] Next, use Figures 2 to 9 The processing method of the wafer 11 when manufacturing WL-CSP from the wafer 11 will be described. In the processing method of the present implementation mode, first, use the bonding device 10 (refer to Figures 2 to 5), a resin film is formed on the front surface 11a side of the wafer 11 so as to cover the bumps 15b.

[0040] The bonding device 10 has a plate-shaped stage 12 formed of glass (such as float glass, quartz glass, etc.). A UV lamp 14a that emits ultraviolet rays (UV) is provided at a position below the lower surface 12a of the stage 12 (see Figures 3 to 5 ). In addition, the stage 12 allows the ultraviolet rays irradiated from the UV lamp 14a to pass through.

[0041] A disk-shaped thin plate 14b made of plastic (such as PET) having an area smaller than the upper surface 12b is fixed on the upper surface 12b of the stage 12. The thin plate 14b functions as a protective sheet that prevents the curable resin described later from coming into contact with the upper surface 12b. In addition, the thin plate 14b allows the ultraviolet rays irradiated from the UV lamp 14a to pass through.

[0042] A nozzle 16 is provided above the thin plate 14b. The nozzle 16 is fixed to a nozzle moving device (not shown), and the nozzle 16 can be moved to an inner area located above the thin plate 14b and an outer area located outside the outer periphery of the thin plate 14b by the operation of the nozzle moving device.

[0043] The nozzle 16 is connected to a resin supply source 18. A curable resin having fluidity is supplied from the resin supply source 18 to the nozzle 16. In the present embodiment, an ultraviolet curable resin 17 (see Figure 2 ) is used as the curable resin.

[0044] The ultraviolet curable resin 17 is an epoxy resin, a polyester resin, etc. In addition, a thermosetting resin or a natural curable resin that cures by mixing a main agent and a curing agent can be used instead of the ultraviolet curable resin 17.

[0045] A transfer device 20 for holding and transferring the wafer 11 is provided above the thin plate 14b (see Figures 3 to 5 ). The transfer device 20 has a disk-shaped frame 22 formed of metal.

[0046] A disk-shaped recess 22a is formed in the lower part of the frame 22. The opening of the recess 22a is exposed on the lower surface of the frame 22, and the bottom surface of the recess 22a is located above the opening. A disk-shaped porous plate 24 formed of porous ceramic is fixed in the recess 22a. One surface 24a of the porous plate 24 on the opening side of the recess 22a is substantially flat and lies in the same plane as the lower surface of the frame 22.

[0047] A plurality of first flow paths 22b are radially formed in the concave portion 22a. The plurality of first flow paths 22b are respectively connected to one end of a second flow path 22c that penetrates the frame 22 in the thickness direction of the frame 22. Further, the other end of the second flow path 22c is connected to a suction source 26 such as an ejector.

[0048] When the suction source 26 is actuated, a negative pressure acts on one surface 24a of the porous plate 24 via the first flow path 22b and the second flow path 22c. Thereby, one surface 24a of the porous plate 24 functions as a holding surface for sucking and holding the wafer 11 or the like.

[0049] A plurality of arms 28 are connected to the upper portion of the frame 22, and the plurality of arms 28 move between an inner region located above the thin plate 14b and an outer region located outside the outer periphery of the thin plate 14b.

[0050] Next, a process of forming a resin film on the front surface 11a side of the wafer 11 so as to cover the bumps 15b using the bonding device 10 will be described. Figure 2 FIG. shows the resin supply process S10.

[0051] In the resin supply process S10, the nozzle 16 is positioned above the approximate center of the thin plate 14b, and the ultraviolet curable resin 17 is supplied from the nozzle 16 to the thin plate 14b. For example, when the diameter of the wafer 11 is 300 mm, in order to form a resin film having a thickness of 1 mm from the flat surface 15a, 70 ml of the ultraviolet curable resin 17 is supplied. Since the ultraviolet curable resin 17 has a prescribed viscosity, it accumulates in a dome shape, for example, near the directly below of the nozzle 16.

[0052] After the resin supply process S10, the wafer 11 is attracted and held on the back surface 11b side (holding process S20) using one surface 24a of the transfer device 20 so that the wafer 11 faces the thin plate 14b. Figure 3 FIG. shows the holding process S20. In the holding process S20, the front surface 11a of the wafer 11 faces downward, and the front surface 11a side faces the ultraviolet curable resin 17 located on the upper surface 12b side of the stage 12.

[0053] After the holding process S20, the wafer 11 is moved downward using the transfer device 20, and the front surface 11a of the wafer 11 is moderately pressed against the ultraviolet curable resin 17 so that the bumps 15b do not contact the thin plate 14b (covering process S30).

[0054] At this time, the distance between the lower end of the bump 15b and the upper surface of the thin plate 14b is set to a distance equivalent to the height of one or more but two or less bumps 15b. For example, when the height of the bump 15b is 100 μm, the lower end of the bump 15b is separated from the upper surface of the thin plate 14b by 100 μm or more and 200 μm or less. Figure 4 FIG. is a view showing the covering step S30.

[0055] The ultraviolet curable resin 17 enters the gap 15c between the bump 15b and the flat surface 15a, and the bump 15b is buried in the ultraviolet curable resin 17. Thus, the entire front surface 11a of the wafer 11 is covered with the ultraviolet curable resin 17.

[0056] In this way, in the covering step S30 of the present embodiment, the bump 15b on the front surface 11a side is pressed against the ultraviolet curable resin 17 having fluidity without using centrifugal force. Therefore, the gap between the bump 15b and the flat surface 15a and the entire front surface 11a side of the wafer 11 can be covered with the ultraviolet curable resin 17 having a uniform thickness.

[0057] After the covering step S30, ultraviolet rays are irradiated from the UV lamp 14a to the ultraviolet curable resin 17 through the stage 12 and the thin plate 14b for several seconds, for example, to cure the ultraviolet curable resin 17. Thus, a resin film 19 is formed on the front surface 11a side of the wafer 11 (hardening step S40).

[0058] Figure 5 FIG. is a view showing the hardening step S40. If the ultraviolet curable resin 17 is used, it is advantageous that the cured resin film 19 can be formed in a short time compared with the case of using a thermosetting resin or a natural curing resin.

[0059] Then, the transfer device 20 is moved upward. The adhesive force between the resin film 19 and the PET thin plate 14b is weaker than the adhesive force between the resin film 19 and the front surface 11a side of the wafer 11. Therefore, if the transfer device 20 is moved upward, the wafer 11 is easily peeled off from the thin plate 14b.

[0060] After the wafer 11 is peeled off from the thin plate 14b, a resin-made protective tape 21 having a diameter larger than that of the wafer 11 is pasted on the back surface 11b side of the wafer 11 using a tape pasting device (not shown) (refer to Figure 6 ).

[0061] In addition, a metal-made ring-shaped frame (not shown) is pasted on the outer peripheral portion of the protective tape 21 to form a wafer unit 23. Then, the wafer unit 23 is transferred to the dicing device 30.

[0062] The tool cutting device 30 has a chuck table 32. A table moving mechanism (not shown) composed of a ball screw or the like is provided below the chuck table 32. If the table moving mechanism is operated, the chuck table 32 moves in a specified machining feed direction.

[0063] A disk-shaped porous plate (not shown) formed of porous ceramics is fixed to the upper surface side of the chuck table 32. The porous plate is connected to a suction source (not shown) such as an ejector.

[0064] When the suction source is operated, negative pressure acts on the upper surface of the porous plate. Therefore, the upper surface of the porous plate functions as a holding surface 32a for sucking and holding the wafer unit 23. Above the holding surface 32a, a tool cutting unit 34 is provided.

[0065] The tool cutting unit 34 has a cylindrical spindle housing 34a. The spindle housing 34a is fixed to a Z-axis moving plate (not shown) that can move in the Z-axis direction, and the Z-axis moving plate is connected to a Z-axis moving mechanism (not shown).

[0066] A part of the spindle 34b is rotatably housed in the spindle housing 34a. The upper end portion of the spindle 34b is connected to a rotation drive source (not shown) such as a motor. On the other hand, the lower end portion of the spindle 34b projects outside the spindle housing 34a.

[0067] A disk-shaped grinding wheel mounting base 34c is fixed to the lower end portion of the spindle 34b. The upper surface side of a disk-shaped tool wheel 36 formed of a metal such as stainless steel or aluminum is mounted on the lower surface side of the grinding wheel mounting base 34c.

[0068] A tool 38 is mounted on a part of the outer peripheral portion on the lower surface side of the tool wheel 36. The tool 38 has a substantially prismatic base portion 38a mounted on the tool wheel 36.

[0069] A cutting edge 38b formed of diamond or the like is fixed to the end portion of the base portion 38a on the side opposite to the tool wheel 36. In addition, a hammer portion 40 is connected to other parts of the outer peripheral portion on the lower surface side of the tool wheel 36.

[0070] The center of gravity of the hammer portion 40 is arranged at a position symmetric with respect to the center of rotation of the tool cutting unit 34 with respect to the center of gravity of the tool 38. By arranging the hammer portion 40, the balance during rotation of the tool cutting unit 34 can be made better than in the case where there is no hammer portion 40.

[0071] The surface 19a side of the resin film 19 is cut using the tool cutting device 30 to thin the resin film 19 (thinning process S50). Figure 6FIG. is a diagram showing the thinning process S50. In the thinning process S50, first, the protective tape 21 side of the wafer unit 23 is held by the holding surface 32a of the chuck table 32.

[0072] Thereby, the resin film 19 of the wafer unit 23 is exposed upward. Next, by operating the rotation drive source, the cutting tool unit 34 is rotated about the spindle 34b, and the lower end of the cutting edge 38b is adjusted to a position slightly lower than the height of the upper end of the bump 15b.

[0073] Next, the chuck table 32 is moved in the machining feed direction (X-axis direction) perpendicular to the Z-axis direction. Thereby, a part of the upper side of the resin film 19 and the bump 15b is cut by the cutting tool 38, and the upper side of the bump 15b is exposed from the resin film 19. After the thinning process S50, the wafer unit 23 is transferred to the laser processing apparatus 50 (refer to Figure 7 (A)).

[0074] Similar to the cutting tool device 30, the laser processing apparatus 50 also has a chuck table (not shown) that sucks and holds the protective tape 21 side of the wafer unit 23. A θ stage (not shown) for rotating the chuck table is connected below the chuck table, and an X-axis moving mechanism (not shown) for moving the chuck table in the machining feed direction (X-axis direction) is connected below the θ stage.

[0075] Above the chuck table, a processing head 52 for irradiating a pulsed laser beam L is provided (refer to Figure 7 (A)). The laser beam L irradiated from the processing head 52 has, for example, a wavelength of 355 nm, a repetition frequency of 200 kHz, an average output of 2.0 W, and a pulse width in the nanosecond range.

[0076] 355 nm is an example of the wavelength absorbed by the resin film 19. By irradiating a part of the resin film 19 with the laser beam L, a part of the resin film 19 is ablated and removed.

[0077] Using the laser processing apparatus 50, the laser beam L is irradiated onto the resin film 19 along each dicing predetermined line 13 to remove the resin film 19 on each dicing predetermined line 13 (laser beam irradiation process S60). Figure 7 (A) is a diagram showing the laser beam irradiation process S60.

[0078] In the laser beam irradiation process S60, first, the orientation of the wafer 11 is adjusted by the θ stage so that the X-axis direction of the laser processing apparatus 50 is parallel to one dicing predetermined line 13. Then, the laser beam L is irradiated from one end to the other end of one dicing predetermined line 13 to remove the resin film 19 on one dicing predetermined line 13.

[0079] Next, the processing head 52 is index-fed in the Y-axis direction perpendicular to the X-axis direction, and the processing head 52 is positioned directly above another division predetermined line 13 adjacent to one division predetermined line 13 in the Y-axis direction. Then, the laser beam L is irradiated from one end to the other end of the other division predetermined line 13, and the resin film 19 on the other division predetermined line 13 is removed.

[0080] Similarly, after removing the resin film 19 along all the division predetermined lines 13 parallel to the X-axis direction, the wafer 11 is rotated 90 degrees using the θ stage. Then, similarly, the resin film 19 is removed along the unprocessed division predetermined lines 13. In addition, in the laser beam irradiation step S60, when there is a TEG (Test Element Group) or a Low-k film on the division predetermined line 13, they are also removed together with the resin film 19.

[0081] Figure 7 (B) is a cross-sectional view of the wafer 11 and the like after the laser beam irradiation step S60. Through the laser beam irradiation step S60, grooves 19b are formed on the resin film 19 along each division predetermined line 13 and reaching the front surface 11a of the wafer 11. Thus, the resin film 19 is patterned.

[0082] Figure 7 (C) is an enlarged view of the vicinity of the groove 19b. In addition, although not shown in Figure 7 (C), in the laser beam irradiation step S60, sometimes the front surface 11a side of the wafer 11 is removed along the division predetermined line 13 or a thermally deteriorated layer is formed on the front surface 11a side along the division predetermined line 13.

[0083] After the laser beam irradiation step S60, the wafer unit 23 is transferred to a plasma etching apparatus 54 (refer to Figure 8 (A)). The plasma etching apparatus 54 of the present embodiment is a direct plasma type that plasmaizes a gas in a chamber by a capacitive coupling method, but it may also be a remote plasma type that supplies a gas plasmaized outside the chamber into the chamber.

[0084] The plasma etching apparatus 54 has a chamber (not shown) formed of metal and grounded. A gate portion (not shown) serving as a transfer path for the wafer unit 23 is provided in the chamber, and an exhaust apparatus (not shown) for exhausting the inside of the chamber is connected at a position different from the gate portion.

[0085] A worktable base (not shown) is provided in the chamber. An electrostatic chuck (not shown) and a bias electrode (not shown) are provided on the worktable base. The electrostatic chuck holds the wafer unit 23, and the bias electrode is electrically separated from the electrostatic chuck and is connected to a high-frequency power source (not shown) via an interelectrode coupling capacitor (not shown).

[0086] A mesh-like plasma diffusion member (not shown) made of metal is provided between the upper part of the workbench base and the ceiling part of the chamber. A gas supply pipe (not shown) is provided at the upper part of the chamber in a manner that is substantially perpendicular to the ceiling part of the chamber.

[0087] The gas supply pipe of the present embodiment is connected to a first gas supply source having SF6 and a second gas supply source having C4F8, but the types of gases used are not limited to this example.

[0088] In the present embodiment, the patterned resin film 19 is used as a mask, and the wafer 11 is divided into individual device chips along each division predetermined line 13 by the BOSCH method (division process S70). Figure 8 (A) of FIG. is a diagram showing the division process S70.

[0089] In the division process S70, first, the wafer unit 23 is transferred onto the electrostatic chuck, and the wafer unit 23 is held by the electrostatic chuck in such a manner that the resin film 19 is exposed upward and the protective tape 21 is in contact with the electrostatic chuck. Then, the door part is closed, and the exhaust device is operated to make the pressure inside the chamber a specified pressure.

[0090] Next, in a state where power is supplied from the high-frequency power supply to the bias electrode, SF6 is supplied from the gas supply pipe to the inside of the chamber for a first specified time. The SF6 gas is plasmaized inside the chamber, and the plasmaized SF6 gas is supplied to the front surface 11a side of the wafer 11.

[0091] The plasmaized SF6 gas (i.e., etching gas P) supplied to the front surface 11a side of the wafer 11 contains fluoride ions, fluorine radicals, etc., and the wafer 11 is etched by the etching gas P (etching process).

[0092] Next, the supply of SF6 gas from the first gas supply source is stopped, and C4F8 gas is supplied from the second gas supply source to the gas supply pipe for a second specified time. Thereby, the plasmaized C4F8 gas is supplied to the front surface 11a side of the wafer 11. By the plasmaized C4F8 gas, the side surfaces and the bottom surface of the etching groove (not shown) on the front surface 11a of the wafer 11 are covered with a CF-based polymer film (covering process).

[0093] Furthermore, by alternately switching the types of gases supplied into the chamber, the etching process and the covering process are repeated multiple times. The wafer 11 is divided along the division predetermined line 13 by the groove 11c formed in the wafer 11, and WL-CSP (device chip) is manufactured.

[0094] Figure 8 (B) of FIG. is a cross-sectional view of the wafer 11 etc. after the division process S70, Figure 8(C) is a cross-sectional view of WL-CSP25. Additionally, Figure 9 is a flowchart of a method for processing the wafer 11.

[0095] In the present embodiment, by using the resin film 19 as a mask to perform plasma etching on the front surface 11a side of the wafer 11, the wafer 11 can be divided into individual WL-CSP 25s. Therefore, compared with the case of forming a resist film using a spin coater, the yield can be improved.

[0096] Additionally, in the case where a space without the resin film 19 is formed between the bump 15b and the flat surface 15a, there is a concern about a reduction in the strength of the WL-CSP 25. However, in the present embodiment, since the resin film 19 is formed through the above-mentioned covering process S30 and the like, it is not easy to form such a space. Therefore, a reduction in the strength of the WL-CSP 25 can be prevented.

[0097] Additionally, in the case where a space is formed between the bump 15b and the flat surface 15a, when the wafer 11 is heated during plasma etching, the air present in the space expands, and breakage and cracks of the wafer 11, the resin film 19, etc. are likely to occur. However, in the present embodiment, since it is not easy to form a space between the bump 15b and the front surface 11a, breakage and cracks of the wafer 11, the resin film 19, etc. can be prevented.

[0098] In addition, the structures, methods, etc. of the above embodiment can be appropriately changed and implemented without departing from the purpose of the present invention. The BOSCH method is adopted in the above-mentioned dividing process S70, but depending on the thickness of the wafer 11 removed by etching, the covering process can be omitted and only the etching process can be performed.

Claims

1. A method for processing a workpiece, wherein a plurality of bumps are provided in each of a plurality of regions defined by a plurality of division predetermined lines set on the front side of the workpiece, and characterized in that, The method for processing the workpiece has the following steps: A holding step of holding the workpiece with the front side thereof facing downwards so as to be opposed to the upper surface side of a stage provided with a curable resin having fluidity; A covering step of moving the workpiece downward and pressing the front side of the workpiece against the curable resin, so that the curable resin enters the gap between the bumps and the front side and the bumps are buried in the curable resin, and covering the entire front side of the workpiece with the curable resin; A hardening step of hardening the curable resin to form a resin film; A laser beam irradiation step of, after the hardening step, irradiating a laser beam having a wavelength absorbed by the resin film along each division predetermined line to remove the resin film on each division predetermined line; and A dividing step of, after the laser beam irradiation step, supplying a plasma gas to the workpiece and dividing the workpiece into individual device chips along each division predetermined line using the resin film as a mask, The method for processing the workpiece further has the following thinning step: before the laser beam irradiation step, cutting the surface of the resin film formed in the hardening step with a cutting tool to thin the resin film.

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