Wafer processing method

Abstract

To provide a wafer processing method which can suppress a time required for forming a mask for plasma dicing.SOLUTION: A wafer processing method includes: a coating step 1001 for coating a surface of a wafer with an ultraviolet curable resin; a protective film formation step 1002 of irradiating the ultraviolet curable resin with ultraviolet light, curing the ultraviolet curable resin, and forming a protective film, after execution of the coating step 1001; a mask formation step 1003 for emitting a laser beam along a scheduled dividing line, forming an opening along the scheduled dividing line in the protective film, and forming a mask for plasma dicing, after execution of the protective film formation step 1002; and a plasma etching step 1004 for subjecting the wafer to plasma etching through the mask for plasma dicing, after execution of the mask formation step 1003.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a wafer processing method for a wafer in which devices are respectively formed in each region of a surface defined by a plurality of intersecting scheduled division lines.

Background Art

[0002] Semiconductor devices are formed by dividing a wafer on which a plurality of semiconductor devices are formed, and the wafer is divided using a cutting device equipped with a cutting blade or a laser processing apparatus. In recent years, so-called plasma dicing, in which a wafer is divided by irradiating the wafer with plasmaized gas and etching only a region along the scheduled division lines, has also been performed.

[0003] In plasma dicing, a mask for plasma dicing exposing only the scheduled division lines is formed on the wafer. To facilitate removal of the plasma dicing mask after plasma etching, a method of forming the mask from a water-soluble resin is used (see, for example, Patent Document 1).

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] Since the plasma dicing mask is also etched during plasma dicing, it is necessary to form a plasma dicing mask having a sufficient thickness to protect the semiconductor devices. In the method disclosed in the aforementioned Patent Document 1, drying the water-soluble resin takes a long time, and improvement has been strongly desired.

[0006] The object of the present invention is to provide a wafer processing method that can suppress the time required for forming a mask for plasma dicing. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the present invention provides a wafer processing method in which devices are formed in each region of a surface partitioned by a plurality of intersecting division lines, comprising: a coating step of covering the surface of the wafer with an ultraviolet-curable resin; a protective film forming step of irradiating the ultraviolet-curable resin with ultraviolet light to cure it and form a protective film after performing the coating step; a mask forming step of irradiating the protective film with a laser beam along the division lines to form an opening in the protective film along the division lines and form a plasma dicing mask after performing the mask forming step; and a plasma etching step of performing plasma etching on the wafer through the plasma dicing mask after performing the mask forming step. After performing the plasma etching step, the plasma dicing mask of the wafer is covered with the ultraviolet-curable resin, and the ultraviolet-curable resin on the plasma dicing mask is cured by irradiating it with ultraviolet light to form a release resin layer on the plasma dicing mask, and then the release resin layer is peeled off the wafer to remove the plasma dicing mask together with the release resin layer in a mask removal step. It is characterized by having the following features.

[0008] In the wafer processing method described above, in the coating step, the ultraviolet-curable resin is supplied onto a surface plate that transmits ultraviolet light, and the back side of the wafer is held by a wafer holding unit having a holding surface facing the surface plate, and the wafer holding unit is moved relatively closer to the surface plate from a position where the surface of the wafer faces the ultraviolet-curable resin on the surface plate, thereby spreading the ultraviolet-curable resin on the surface of the wafer and coating the surface with the ultraviolet-curable resin. In the protective film formation step, the ultraviolet light may be irradiated onto the ultraviolet-curable resin through the surface plate.

[0009] In the wafer processing method described above, the UV-curable resin may be applied by spin coating in the coating step.

[0012] In the wafer processing method described above, the ultraviolet-curable resin may include an acrylate, a photopolymerizing agent, and a light-absorbing material that absorbs the wavelength of the laser beam. [Effects of the Invention]

[0013] This invention has the effect of reducing the time required for forming a mask for plasma dicing. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a perspective view showing an example of a workpiece to be processed in the wafer processing method according to Embodiment 1. [Figure 2] Figure 2 is a flowchart showing the flow of the wafer processing method according to Embodiment 1. [Figure 3] Figure 3 is a partial cross-sectional side view showing the state in which the wafer holding unit of the coating apparatus, which holds the wafer, and the surface plate, on which the ultraviolet-curable resin is supplied, are facing each other during the coating step of the wafer processing method shown in Figure 2. [Figure 4] Figure 4 is a partial cross-sectional side view showing the state in which the wafer holding unit of the coating apparatus, which holds the wafer, is moved closer to the surface plate on which the ultraviolet-curable resin has been supplied during the coating step of the wafer processing method shown in Figure 2. [Figure 5] Figure 5 is a side view showing a partial cross-section of the state in which the wafer held in the wafer holding unit of the coating apparatus has spread the ultraviolet-curable resin on the surface of the standard during the coating step of the wafer processing method shown in Figure 2. [Figure 6] Figure 6 is a side view showing a partial cross-section of the state in the protective film formation step of the wafer processing method shown in Figure 2, where the UV-curable resin applied in the coating step is cured to form a protective film. [Figure 7] Figure 7 is a perspective view showing the state in which tape is attached to the back side of a wafer with a protective film formed on its surface, during the protective film formation step of the wafer processing method shown in Figure 2. [Figure 8] Figure 8 is a schematic side view showing a partial cross-section of the mask formation step of the wafer processing method shown in Figure 2. [Figure 9]FIG. 9 is a cross-sectional view schematically showing the wafer after the mask forming step of the wafer processing method shown in FIG. 2. [Figure 10] FIG. 10 is a cross-sectional view schematically showing a configuration example of a plasma etching apparatus that performs the plasma etching step of the wafer processing method shown in FIG. 2. [Figure 11] FIG. 11 is a cross-sectional view schematically showing the wafer after the plasma etching step of the wafer processing method shown in FIG. 2. [Figure 12] FIG. 12 is a cross-sectional view schematically showing a state where a tape is attached onto a plasma dicing mask in the mask removing step of the wafer processing method shown in FIG. 2. [Figure 13] FIG. 13 is a cross-sectional view schematically showing a state where the tape attached to the plasma dicing mask is peeled off in the mask removing step of the wafer processing method shown in FIG. 2. [Figure 14] FIG. 14 is a perspective view schematically showing a state where a tape is attached to the back surface of a wafer and a frame is attached to an outer edge portion of the tape in the covering step of the wafer processing method according to Modification 1 of Embodiment 1. [Figure 15] FIG. 15 is a side view schematically showing, in partial cross-section, a state where the entire surface of the wafer is covered with an ultraviolet curable resin in the covering step of the wafer processing method according to Modification 1 of Embodiment 1. [Figure 16] FIG. 16 is a side view schematically showing, in partial cross-section, the protective film forming step of the wafer processing method according to Modification 1 of Embodiment 1. [Figure 17] FIG. 17 is a cross-sectional view schematically showing a state where a release resin layer is formed on a plasma dicing mask in the mask removing step of the wafer processing method according to Modification 2 of Embodiment 1. [Figure 18] FIG. 18 is a cross-sectional view schematically showing a state where a peel tape is attached to the release resin layer formed on the plasma dicing mask in the mask removing step of the wafer processing method according to Modification 2 of Embodiment 1. DETAILED DESCRIPTION OF THE INVENTION

[0015] Modes (embodiments) for carrying out the present invention will be described in detail below with reference to the accompanying drawings. The present invention is not limited by the contents described in the following embodiments. The components described below include those that can be easily conceived by those skilled in the art and those that are substantially identical. Further, the configurations described below can be combined as appropriate. Various omissions, substitutions or modifications of the configuration can be made without departing from the gist of the present invention.

[0016] [Embodiment 1] A wafer processing method according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an example of a workpiece to be processed by the wafer processing method according to Embodiment 1. FIG. 2 is a flowchart showing the flow of the wafer processing method according to Embodiment 1.

[0017] (Wafer) The wafer processing method according to Embodiment 1 is a processing method for a wafer 1 shown in FIG. 1. In Embodiment 1, the wafer 1 is a wafer such as a semiconductor wafer in which silicon or the like is used as a substrate 2 and a device layer 3 is formed on the substrate 2. As shown in FIG. 1, in the wafer 1, devices 6 are respectively formed in respective regions of a front surface 4 which are partitioned in a grid pattern by a plurality of planned dividing lines 5 intersecting each other.

[0018] The device 6 is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), or a memory (semiconductor storage device). The device layer 3 includes: an inorganic film such as SiOF or BSG (SiOB), an organic film which is a polymer film such as a polyimide-based or parylene-based polymer film, or a low dielectric constant insulating film (hereinafter referred to as a Low-k film) made of carbon-containing silicon oxide (SiOCH); and a circuit layer configured to include a conductive metal pattern or a conductive metal film.

[0019] The low-k film is stacked with the circuit layer to form device 6. The circuit layer constitutes the circuit of device 6. For this reason, device 6 is composed of low-k films stacked on top of each other on the substrate 2, and circuit layers stacked between the low-k films. In the planned division line 5, the device layer 3 is composed of low-k films stacked on the substrate 2, except for the TEG (Test Elementary G group).

[0020] In this invention, the material of the substrate 2 of the wafer 1 and the type of device 6 are not limited to those described in Embodiment 1.

[0021] (Wafer processing method) The wafer processing method according to Embodiment 1 is a method of dividing a wafer 1 into individual chips 10 along a planned division line 5. The chip 10 includes a part of the substrate 2 and a device 6 on the substrate 2. The wafer processing method according to Embodiment 1 is also a method of dividing the wafer 1 into chips 10 by plasma etching, or so-called plasma dicing. As shown in Figure 2, the wafer processing method comprises a coating step 1001, a protective film formation step 1002, a mask formation step 1003, a plasma etching step 1004, and a mask removal step 1005.

[0022] (Coating step) Figure 3 is a partial cross-sectional side view showing the state in which the wafer holding unit of the coating apparatus, which holds the wafer, and the surface plate on which the UV-curable resin has been supplied are facing each other during the coating step of the wafer processing method shown in Figure 2. Figure 4 is a partial cross-sectional side view showing the state in which the wafer holding unit of the coating apparatus, which holds the wafer, has been moved closer to the surface plate on which the UV-curable resin has been supplied. Figure 5 is a partial cross-sectional side view showing the state in which the wafer held by the wafer holding unit of the coating apparatus has spread the UV-curable resin on the surface of the standard during the coating step of the wafer processing method shown in Figure 2. Note that the device layer 3 is omitted in Figures 3, 4 and 5.

[0023] The coating step 1001 is a step in which the surface 4 of the wafer 1 is coated with an ultraviolet-curable resin 11 (shown in Figure 3). In Embodiment 1, in coating step 1001, as shown in Figure 3, liquid ultraviolet-curable resin 11 is supplied onto the surface 22 of a base plate 21 made of glass or the like that transmits ultraviolet light 28 (shown in Figure 6) of the coating apparatus 20. In Embodiment 1, in coating step 1001, as shown in Figure 3, the coating apparatus 20 opens the on / off valve 23 and uses a suction source 26 to suck the holding surface 25 of the wafer holding unit 24, which is facing the surface 22 of the base plate 21 at a distance and parallel to it, and holds the back side 7 of the wafer 1 by suction to the holding surface 25. Thus, in Embodiment 1, in coating step 1001, the back side 7 of the wafer 1 is held by suction with the wafer holding unit 24 having a holding surface 25.

[0024] In Embodiment 1, during the coating step 1001, the coating apparatus 20 moves the wafer holding unit 24 from the position shown in Figure 3, where the surface 4 of the wafer 1 faces the ultraviolet-curable resin 11 on the surface 22 of the platen 21, to a position closer to the platen 21, as shown in Figure 4. Then, the surface 4 of the wafer 1, which is held by the wafer holding unit 24 at suction, comes into contact with the ultraviolet-curable resin 11 on the surface 22 of the platen 21. In Embodiment 1, during the coating step 1001, the coating apparatus 20 moves the wafer holding unit 24 even closer to the platen 21, and as shown in Figure 5, pushes the ultraviolet-curable resin 11 on the surface 4 of the wafer 1 in the outer peripheral direction of the platen 21, thereby coating the entire surface 4 of the wafer 1 with the ultraviolet-curable resin 11.

[0025] Furthermore, in Embodiment 1, in the coating step 1001, the surface 4 of the wafer 1 and the surface 22 of the base plate 21 are positioned parallel to each other. In Embodiment 1, the UV-curable resin 11 is a resin that hardens when irradiated with ultraviolet light 28, and includes, for example, a well-known acrylate, a well-known photopolymerizing agent, and a well-known light-absorbing material (for example, carbon black or phthalocyanine) that absorbs a laser beam 36 (shown in Figure 8) with a wavelength of, for example, 355 nm.

[0026] (Protective film formation step) Figure 6 is a side view showing a partial cross-section of the protective film formation step in the wafer processing method shown in Figure 2, where the UV-curable resin applied in the coating step has cured to form a protective film. Figure 7 is a perspective view showing the protective film formation step in the wafer processing method shown in Figure 2, where tape has been attached to the back side of a wafer with a protective film formed on its surface. Note that device layer 3 is omitted in Figure 6.

[0027] The protective film formation step 1002 is a step in which, after performing the coating step 1001, the ultraviolet-curable resin 11 is irradiated with ultraviolet light 28 to cure it and form a protective film 12 (shown in Figure 6). In Embodiment 1, in the protective film formation step 1002, the coating apparatus 20 lights up an ultraviolet lamp 27 located below the surface plate 21, as shown in Figure 6, and irradiates the ultraviolet-curable resin 11 covering the entire surface 4 of the wafer 1 with ultraviolet light 28 for a predetermined time through the surface plate 21 from the ultraviolet lamp 27. As a result, the ultraviolet-curable resin 11 hardens, and a protective film 12 is formed on the entire surface 4 of the wafer 1 by the hardened ultraviolet-curable resin 11. The protective film 12 is made of a material that is resistant to the plasma-generated etching gas used in the plasma etching step 1004, and is formed to a uniform thickness that is resistant to the etching gas.

[0028] In Embodiment 1, in the protective film formation step 1002, as shown in Figure 7, the central part of a disc-shaped tape 8 with a larger diameter than the wafer 1 is attached to the back surface 7 of the wafer 1, and an annular frame 9 with an inner diameter larger than the outer diameter of the wafer 1 is attached to the outer edge of the tape 8. In Embodiment 1, the tape 8 is an adhesive tape comprising a base material made of a resin having non-adhesive and flexible properties, and an adhesive layer laminated on the base material and made of a resin having adhesive and flexible properties, with the adhesive layer being attached to the wafer 1 and frame 9, or a sheet consisting only of a base material made of a thermoplastic resin without an adhesive layer and being heat-pressed to the wafer 1 and frame 9.

[0029] (Mask formation step) Figure 8 is a schematic side view showing a partial cross-section of the mask formation step of the wafer processing method shown in Figure 2. Figure 9 is a schematic cross-sectional view showing the wafer after the mask formation step of the wafer processing method shown in Figure 2. Note that Figures 8 and 9 omit the device layer 3. The mask formation step 1003 is a step in which, after performing the protective film formation step 1002, a laser beam 36 (shown in Figure 8) is irradiated along the division line 5 to form an opening 131 (shown in Figure 9) in the protective film 12 along the division line 5, thereby forming a plasma dicing mask 13 (shown in Figure 9).

[0030] In Embodiment 1, during the mask formation step 1003, the laser processing apparatus 30 shown in Figure 8 holds the back surface 7 of the wafer 1 to the holding surface 32 of the chuck table 31 via tape 8, and clamps the frame 9 with clamps 37 provided around the chuck table 31. In Embodiment 1, during the mask formation step 1003, the laser processing apparatus 30 images the surface 4 of the wafer 1 with an imaging camera and performs alignment to align the wafer 1 with the focusing lens 34 of the laser beam irradiation unit 33.

[0031] In Embodiment 1, in the mask formation step 1003, the laser processing apparatus 30 moves the chuck table 31 and the laser beam irradiation unit 33 relative to each other along the division line 5, as shown in Figure 8, and irradiates the protective film 12 on each division line 5 with a laser beam 36 of a wavelength (for example, 355 nm) that is absorbed by the protective film 12 oscillated by the oscillator 35, thereby removing the protective film 12 on each division line 5. In Embodiment 1, in the mask formation step 1003, the laser processing apparatus 30 forms an opening 131 along the division line 5 over the entire length of each division line 5, thereby forming the protective film 12 on the plasma dicing mask 13 with the opening 131 formed as shown in Figure 9. The opening 131 exposes the division line 5 at its bottom.

[0032] (Plasma etching equipment) Next, the plasma etching apparatus 50 that performs the plasma etching step 1004 will be described based on the drawings. Figure 10 is a schematic cross-sectional view showing an example of the configuration of a plasma etching apparatus that performs the plasma etching step of the wafer processing method shown in Figure 2. As shown in Figure 10, the plasma etching apparatus 50 comprises a rectangular parallelepiped chamber 51, a holding unit 52, an upper electrode 53, and a control unit 55.

[0033] Chamber 51 has a processing space 511 formed inside where plasma etching is performed. Chamber 51 has an opening 513 for loading and unloading wafers 1 and an opening / closing door 514 on one side wall 512 that opens and closes the opening 513. The opening / closing door 514 opens and closes the opening 513 by moving up and down with an opening / closing mechanism 515 consisting of an air cylinder or the like.

[0034] Furthermore, the chamber 51 has an exhaust port 517 formed in its bottom wall 516, which connects the inside and outside of the chamber 51. An exhaust mechanism 510, such as a vacuum pump, is connected to the exhaust port 517.

[0035] The holding unit 52 and the upper electrode 53 are positioned facing each other in the processing space 511 of the chamber 51. The upper surface of the holding unit 52 is a holding surface 524 that holds the wafer 1 via the tape 8. The holding unit 52 is also made of a conductive material and functions as a lower electrode.

[0036] The holding unit 52 includes a disc-shaped holding portion 521 and a cylindrical support portion 520 that protrudes downward from the center of the lower surface of the holding portion 521. The support portion 520 is inserted into an opening 522 formed in the bottom wall 516 of the chamber 51. Within the opening 522, an annular insulating member 523 is placed between the bottom wall 516 and the support portion 520, electrically insulating the chamber 51 and the holding unit 52. The holding unit 52 is also connected to a high-frequency power supply 56 outside the chamber 51.

[0037] The holding portion 521 of the holding unit 52 is provided with an electrode 526 connected to a high-frequency power supply (not shown). When power is applied to the electrode 526 from the high-frequency power supply, the holding unit 52 generates a dielectric polarization phenomenon between the holding surface 524 and the wafer 1, and the wafer 1 is held and attracted onto the holding surface 524 by the electrostatic attraction force due to the polarization of the charge.

[0038] Furthermore, cooling channels 527 are formed inside the holding portion 521 and the support portion 520 of the holding unit 52, through which a cooling fluid flows to cool the holding unit 52. Both ends of the cooling channels 527 are connected to a refrigerant circulation mechanism 528. When the refrigerant circulation mechanism 528 is activated, a cooling fluid such as water circulates through the cooling channels 527, cooling the holding unit 52.

[0039] The upper electrode 53 is made of a conductive material and includes a disc-shaped gas ejection portion 531 and a cylindrical support portion 530 that protrudes upward from the center of the upper surface of the gas ejection portion 531. The support portion 530 is inserted into an opening 532 formed in the upper wall 518 of the chamber 51. Within the opening 532, an annular insulating member 533 is placed between the upper wall 518 and the support portion 530, thereby electrically insulating the chamber 51 from the upper electrode 53.

[0040] The upper electrode 53 is connected to the high-frequency power supply 57 outside the chamber 51. A support arm for the lifting mechanism 534 is attached to the upper end of the support portion 530. The upper electrode 53 moves up and down by the lifting mechanism 534.

[0041] Multiple nozzles 535 are provided on the lower side of the gas ejection section 531. The nozzles 535 are connected to a first etching gas supply source 58 and a second etching gas supply source 59 via a flow path 536 formed in the gas ejection section 531 and the support section 530. The first etching gas supply source 58 supplies a first etching gas into the chamber 51 from the nozzles 535 through the flow path 536. In Embodiment 1, when the substrate 2 of the wafer 1 is made of silicon, the first etching gas supply source 58 supplies a fluorine-based gas into the chamber 51 as the first etching gas. The second etching gas supply source 59 supplies a second etching gas into the chamber 51 from the nozzles 535 through the flow path 536. In Embodiment 1, the second etching gas supply source 59 supplies an oxygen-based gas into the chamber 51 as the second etching gas.

[0042] The control unit 55 controls each component of the plasma etching apparatus 50 to cause the plasma etching apparatus 50 to perform plasma etching on the wafer 1. The control unit 55 is a computer having a processing unit with a microprocessor such as a CPU (central processing unit), a storage device with memory such as ROM (read-only memory) or RAM (random access memory), and an input / output interface device. The processing unit of the control unit 55 performs calculations according to the computer program stored in the storage device and outputs control signals for controlling the plasma etching apparatus 50 to each component of the plasma etching apparatus 50 via the input / output interface device.

[0043] Furthermore, the control unit 55 is connected to a display unit, which consists of a liquid crystal display device that displays various information and images, and an input unit used by the operator to register processing content information. The input unit consists of at least one of the following: a touch panel provided on the display unit and an external input device such as a keyboard.

[0044] (Plasma etching step) Figure 11 is a schematic cross-sectional view showing the wafer after the plasma etching step of the wafer processing method shown in Figure 2. Note that the device layer 3 is omitted in Figure 11. The plasma etching step 1004 is a step in which plasma etching is performed on the wafer 1 via the plasma dicing mask 13 after the mask formation step 1003 has been performed.

[0045] In Embodiment 1, during the plasma etching step 1004, the plasma etching apparatus 50 raises the upper electrode 53 by the lifting mechanism 534 and raises the frame clamping plate 542 by the lifting mechanism, and then lowers the opening / closing door 514 by the opening / closing mechanism 515 to open the opening 513.

[0046] In the plasma etching step 1004, the plasma etching apparatus 50 receives the wafer 1, on which a plasma dicing mask 13 has been formed on the entire back surface 7 in the mask formation step 1003, into the processing space 511 via a transport unit (not shown), and places the wafer 1 on the holding surface 524 of the holding unit 52 via tape 8. In the plasma etching step 1004, the plasma etching apparatus 50 applies power from a high-frequency power supply to the electrode 526 to adsorb and hold the surface 4 of the wafer 1 on the holding surface 524 via tape 8.

[0047] In the plasma etching step 1004, the plasma etching apparatus 50 raises the opening / closing door 514 using the opening / closing mechanism 515 to close the opening 513, activates the exhaust mechanism 510 to reduce the pressure inside the chamber 51, making the processing space 511 a vacuum (low pressure state), and activates the refrigerant circulation mechanism 528 to circulate a cooling fluid such as water in the cooling channel 527 to suppress abnormal temperature rise of the holding unit 52. In the plasma etching step 1004, the plasma etching apparatus 50 lowers the upper electrode 53 using the lifting mechanism 534, positioning the distance between the lower surface of the upper electrode 53 and the wafer 1 held by the holding unit 52 that constitutes the lower electrode to a predetermined electrode distance suitable for plasma etching.

[0048] In the plasma etching step 1004, the plasma etching apparatus 50 supplies a first etching gas from a first etching gas supply source 58 at a predetermined flow rate and ejects it from multiple nozzles 535 of the gas ejection section 531 toward the wafer 1 held on the holding unit 52. In the plasma etching step 1004, while the plasma etching apparatus 50 is supplying the first etching gas from the first etching gas supply source 58, it applies high-frequency power from a high-frequency power supply 57 to the upper electrode 53 to create and maintain plasma, and applies high-frequency power from a high-frequency power supply 56 to the lower electrode, the holding unit 52, to draw in ions.

[0049] In the plasma etching step 1004, the plasma etching apparatus 50 converts the first etching gas in the space between the holding unit 52 and the upper electrode 53 into plasma, and this plasma-converted first etching gas is drawn towards the wafer 1, etching (so-called plasma etching) the surface 4 of the division line 5 exposed from the opening 131 of the plasma dicing mask 13 of the wafer 1, forming an etching groove 14 (shown in Figure 11) on the surface 4 of the division line 5, and causing the etching groove 14 to advance toward the back surface 7 of the wafer 1.

[0050] In Embodiment 1, when the substrate 2 is made of silicon, a fluorine-based gas such as SF6, C4F8, or CF4 is used as the first etching gas, but the first etching gas is not limited to these. Also, in Embodiment 1, in the plasma etching step 1004, the plasma etching apparatus 50 plasma etches the wafer 1 by the Bosch method, which alternately repeats plasma etching by supplying SF6 and protective film deposition on the inner surface of the etching groove 14 by supplying C4F8, but in the present invention, plasma etching may be performed by supplying a single etching gas.

[0051] In the plasma etching step 1004, the plasma etching apparatus 50 has a predetermined time set for plasma etching the substrate 2 of the wafer 1 according to the thickness of the substrate 2 of the wafer 1. In the plasma etching step 1004, the plasma etching apparatus 50 applies high-frequency power to the holding unit 52 and the upper electrode 53 while supplying the first etching gas for a predetermined time, and as shown in Figure 11, completely removes the division lines 5 exposed from the opening 131 of the plasma dicing mask 13, dividing the wafer 1 along the opening 131 into individual chips 10. That is, in the plasma etching step 1004, etching grooves 14 are made to penetrate the wafer 1 along the entire length of each division line 5.

[0052] (Mask removal step) Figure 12 is a schematic cross-sectional view showing the state in which tape is attached to the plasma dicing mask during the mask removal step of the wafer processing method shown in Figure 2. Figure 13 is a schematic cross-sectional view showing the state in which the tape attached to the plasma dicing mask is peeled off during the mask removal step of the wafer processing method shown in Figure 2. Note that device layer 3 is omitted in Figures 12 and 13.

[0053] The mask removal step 1005 is a step in which, after performing the plasma etching step 1004, a tape 15 consisting of a substrate 151 and an adhesive layer 152 is attached to the plasma dicing mask 13 of the wafer 1, and then the tape 8 is peeled off from the wafer 1, thereby removing the plasma dicing mask 13 together with the tape 15 from the wafer 1.

[0054] In Embodiment 1, in the mask removal step 1005, as shown in Figure 12, a disc-shaped tape 15 having approximately the same diameter as the wafer 1 is attached to the plasma dicing mask 13 on the surface 4 of the wafer 1. In Embodiment 1, the tape 154 is an adhesive tape comprising a base material 151 made of a resin having non-adhesive and flexible properties, and an adhesive layer 152 laminated on the base material 151 and made of a resin having adhesive and flexible properties, with the adhesive layer 152 being attached to the plasma dicing mask 13. Furthermore, the adhesive force of the adhesive layer 152 to the plasma dicing mask 13 is stronger than the adhesive force of the plasma dicing mask 13 to the surface 4 of the wafer 1.

[0055] In Embodiment 1, in the mask removal step 1005, as shown in Figure 13, one end of the tape 15 is moved along the surface 4 of the wafer 1, passing through the center of the wafer 1 and then toward the other end. As a result, the UV-curable resin 11 constituting the plasma dicing mask 13 has reduced adhesive strength to the surface 4 of the wafer 1 compared to before curing when UV light 28 was irradiated in the protective film formation step 1002. Therefore, the plasma dicing mask 13 is removed from the surface 4 of the wafer 1 together with the tape 15. Thus, in Embodiment 1, in the mask removal step 1005, the plasma dicing mask 13 is removed from the wafer 1 together with the tape 15 by peeling the tape 15 from the wafer 1. The thus divided chips 10 are picked up from the tape 8.

[0056] The wafer processing method according to Embodiment 1 described above forms a plasma dicing mask 13 with an ultraviolet-curable resin 11. For this reason, even when forming a protective film 12 of sufficient thickness, the wafer processing method according to Embodiment 1 allows the ultraviolet-curable resin 11 to be cured by irradiation with ultraviolet light 28. Therefore, the plasma dicing mask 13 can be formed in a shorter time than when forming a plasma dicing mask 13 by drying a conventional water-soluble resin (for example, a water-soluble liquid resin such as polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP)).

[0057] As a result, the wafer processing method according to Embodiment 1 has the effect of suppressing the time required for forming the plasma dicing mask 13.

[0058] Furthermore, the wafer processing method according to Embodiment 1 involves pressing the surface 4 of the wafer 1 onto the ultraviolet-curable resin 11 on the surface plate 21 to form a protective film 12. This method makes it easy to control the thickness of the protective film 12 and also allows for the formation of a thick protective film 12.

[0059] [Variation 1] A wafer processing method according to Modification 1 of Embodiment 1 will be described based on the drawings. Figure 14 is a schematic perspective view showing the state in the coating step of the wafer processing method according to Modification 1 of Embodiment 1, where tape is attached to the back surface of the wafer and a frame is attached to the outer edge of the tape. Figure 15 is a schematic side view showing a partial cross-section of the state in the coating step of the wafer processing method according to Modification 1 of Embodiment 1, where the entire surface of the wafer is covered with an ultraviolet-curable resin. Figure 16 is a schematic side view showing a partial cross-section of the protective film formation step of the wafer processing method according to Modification 1 of Embodiment 1. Note that Figures 14, 15, and 16 use the same reference numerals as Embodiment 1 for the same parts and their descriptions are omitted. Also, Figures 14, 15, and 16 omit the device layer 3.

[0060] The wafer processing method according to Modification 1 of Embodiment 1 comprises, similarly to Embodiment 1, a coating step 1001, a protective film formation step 1002, a mask formation step 1003, a plasma etching step 1004, and a mask removal step 1005.

[0061] In Modification 1 of Embodiment 1, in coating step 1001, first, as shown in Figure 14, the central part of a disc-shaped tape 8 with a larger diameter than the wafer 1 is attached to the back surface 7 of the wafer 1, and an annular frame 9 with an inner diameter larger than the outer diameter of the wafer 1 is attached to the outer edge of the tape 8. In Modification 1 of Embodiment 1, in coating step 1001, the protective film coating apparatus 60 shown in Figure 15 places the back surface 7 side of the wafer 1 on the holding surface 62 of the spinner table 61 via the tape 8, holds the back surface 7 side of the wafer 1 on the holding surface 62 via the tape 8, and clamps the frame 9 with clamp parts 63 provided around the spinner table 61.

[0062] In Modification 1 of Embodiment 1, in the coating step 1001, the protective film coating apparatus 60 rotates the spinner table 61 around its axis, as shown in Figure 15, and applies liquid ultraviolet-curable resin 11 from the coating nozzle 64 above the wafer 1 to the center of the surface 4 of the wafer 1. The ultraviolet-curable resin 11 applied to the surface 4 of the wafer 1 is then spread to the outer edge of the wafer 1 by the centrifugal force generated by the rotation of the spinner table 61, covering the entire surface 4 of the wafer 1. Thus, in Modification 1 of Embodiment 1, in the coating step 1001, the ultraviolet-curable resin 11 is supplied and applied to the wafer 1 held by the spinner table 61 rotating around its axis, using a so-called spin coating method.

[0063] In Modification 1 of Embodiment 1, in the protective film formation step 1002, the protective film coating apparatus 60 retracts the coating nozzle 64 from above the wafer 1 and positions the ultraviolet irradiation unit 65 above the surface 4 of the wafer 1, and as shown in Figure 16, irradiates the ultraviolet curable resin 11 on the surface 4 of the wafer 1 with ultraviolet light 28 from the ultraviolet irradiation unit 65 for a predetermined time. In Modification 1 of Embodiment 1, in the protective film formation step 1002, the protective film coating apparatus 60 irradiates the ultraviolet curable resin 11 on the surface 4 of the wafer 1 with ultraviolet light 28 from the ultraviolet irradiation unit 65 for a predetermined time to cure the ultraviolet curable resin 11 on the surface 4 of the wafer 1 and form a protective film 12 that covers the entire surface 4 of the wafer 1.

[0064] In the modification 1 of Embodiment 1, the mask formation step 1003, the plasma etching step 1004, and the mask removal step 1005 are performed in order, similar to Embodiment 1, to divide the wafer 1 into individual chips 10.

[0065] The wafer processing method according to Modification 1 of Embodiment 1, similar to Embodiment 1, allows for the formation of a plasma dicing mask 13 using an ultraviolet-curable resin 11. This method enables the formation of the plasma dicing mask 13 in a shorter time than the conventional method of forming a plasma dicing mask 13 by drying a water-soluble resin, thereby reducing the time required for forming the plasma dicing mask 13.

[0066] [Variation 2] A wafer processing method according to a modified example 2 of Embodiment 1 will be described with reference to the drawings. Figure 17 is a schematic cross-sectional view showing the state in which a release resin layer has been formed on the plasma dicing mask during the mask removal step of the wafer processing method according to a modified example 2 of Embodiment 1. Figure 18 is a schematic cross-sectional view showing the state in which a peel tape has been attached to the release resin layer formed on the plasma dicing mask during the mask removal step of the wafer processing method according to a modified example 2 of Embodiment 1. Note that in Figures 17 and 18, the same reference numerals are used for the same parts as in Embodiment 1, and their descriptions are omitted.

[0067] The wafer processing method according to Modification 2 of Embodiment 1 comprises a coating step 1001, a protective film formation step 1002, a mask formation step 1003, a plasma etching step 1004, and a mask removal step 1005, similar to Embodiment 1. The wafer processing method according to Modification 2 of Embodiment 1 is performed in the same order as Embodiment 1, with the coating step 1001, the protective film formation step 1002, the mask formation step 1003, and the plasma etching step 1004 being carried out in sequence.

[0068] In Modification 2 of Embodiment 1, in the mask removal step 1005, after performing the plasma etching step 1004, the entire plasma dicing mask 13 on the surface 4 of the wafer 1 is covered with ultraviolet-curable resin 11, as shown in Figure 17. In Modification 2 of Embodiment 1, when covering the entire plasma dicing mask 13 with ultraviolet-curable resin 11 in the mask removal step 1005, the procedure is the same as in the protective film formation step 1002 of Modification 1 of Embodiment 1.

[0069] In Modification 2 of Embodiment 1, in the mask removal step 1005, the UV-curable resin 11 on the plasma dicing mask 13 is cured by irradiating it with UV light 28 to form a release resin layer 16 (shown in Figure 17) on the plasma dicing mask 13. When curing the UV-curable resin 11 on the plasma dicing mask 13 by irradiating it with UV light 28, the procedure is carried out in the same manner as in the protective film formation step 1002 of Modification 1 of Embodiment 1.

[0070] Next, in Modification 2 of Embodiment 1, in the mask removal step 1005, one end of a strip-shaped peel tape 17 is attached to one end of the release resin layer 16. In Modification 2 of Embodiment 1, the peel tape 17 is an adhesive tape comprising a base material made of a resin having non-adhesive and flexible properties, and an adhesive layer laminated on the base material and made of a resin having adhesive and flexible properties, with the adhesive layer being attached to the release resin layer 16. Furthermore, the adhesive force of the adhesive layer of the peel tape 17 to the release resin layer 16 and the adhesive force of the release resin layer 16 to the plasma dicing mask 13 are stronger than the adhesive force of the plasma dicing mask 13 to the surface 4 of the wafer 1.

[0071] In Modification 2 of Embodiment 1, in the mask removal step 1005, as shown in Figure 18, the other end of the peel tape 17 is moved along the surface 4 of the wafer 1 so that it passes through the center of the wafer 1 and then toward the other end of the release resin layer 16. As a result, the UV-curable resin 11 constituting the plasma dicing mask 13 has reduced adhesive strength to the surface 4 of the wafer 1 compared to before curing when UV light 28 was irradiated in the protective film formation step 1002. Therefore, the plasma dicing mask 13 peels off from the surface 4 of the wafer 1 together with the peel tape 17 and the release resin layer 16. Thus, in Modification 2 of Embodiment 1, in the mask removal step 1005, the plasma dicing mask 13 is removed from the wafer 1 together with the release resin layer 16 by peeling off from the surface 4 of the wafer 1 together with the peel tape 17 and the release resin layer 16.

[0072] The wafer processing method according to the modified example 2 of Embodiment 1, similar to Embodiment 1, allows for the formation of a plasma dicing mask 13 using an ultraviolet-curable resin 11. This method enables the formation of the plasma dicing mask 13 in a shorter time than the conventional method of forming a plasma dicing mask 13 by drying a water-soluble resin, thereby reducing the time required for forming the plasma dicing mask 13.

[0073] Next, the inventors of the present invention confirmed the effects of the present invention. For this confirmation, the time required to form the protective film 12 of the present invention and the comparative example was measured. The results are shown in Table 1 below.

[0074] [Table 1]

[0075] In the present invention, the irradiation time of ultraviolet 28 required to completely cure the ultraviolet-curable resin 11 that covers the entire surface 4 of the wafer 1 by irradiating it with ultraviolet 28, thereby forming a protective film 12 of the thickness required for the plasma etching step 1004, was measured. In the comparative example, the drying time of the water-soluble resin required to completely dry the aforementioned water-soluble resin that covers the entire surface 4 of the wafer 1, thereby forming a protective film 12 of the thickness required for the plasma etching step 1004, was measured.

[0076] According to Table 1, the comparative example required 5 minutes, while the present invention required 2 minutes. Therefore, Table 1 shows that by forming the plasma dicing mask 13 with the UV-curable resin 11, the plasma dicing mask 13 can be formed in a shorter time than when forming the plasma dicing mask 13 by drying a conventional water-soluble resin, and the time required for forming the plasma dicing mask 13 can be reduced.

[0077] It should be noted that the present invention is not limited to the embodiments described above. That is, it can be implemented with various modifications without departing from the core principles of the present invention. [Explanation of Symbols]

[0078] 1 wafer 4 surface Planned division lines (5 divisions) 6 devices 7 Back side 11 Ultraviolet curing resin 12 Protective film 13 Plasma dicing mask 15 Tapes 16. Release resin layer 21 Surface plate 24 Wafer holding unit 25 Holding surface 28 Ultraviolet rays 36 laser beams 131 Aperture 151 Base material 152 Glue layer 1001 Covering step 1002 Protective film formation step 1003 Mask Forming Step 1004 Plasma etching step 1005 Mask removal step

Claims

1. A wafer processing method in which devices are formed in each region of the surface partitioned by multiple intersecting division lines, A coating step of coating the surface of the wafer with an ultraviolet-curable resin, After performing the coating step, the UV-curable resin is irradiated with ultraviolet light to cure it and form a protective film, and After performing the protective film formation step, a mask formation step is performed in which a laser beam is irradiated along the planned division line to form an opening in the protective film along the planned division line to form a mask for plasma dicing, After performing the mask formation step, a plasma etching step is performed on the wafer through the plasma dicing mask, A wafer processing method comprising: performing the plasma etching step, covering the plasma dicing mask of the wafer with the ultraviolet-curable resin, curing the ultraviolet-curable resin on the plasma dicing mask by irradiating it with ultraviolet light to form a release resin layer on the plasma dicing mask, and then removing the release resin layer from the wafer to remove the plasma dicing mask together with the release resin layer.

2. In the coating step, the UV-curable resin is supplied onto a surface plate that transmits ultraviolet light, and the back side of the wafer is held by a wafer holding unit having a holding surface facing the surface plate. The wafer holding unit is then moved relatively closer to the surface plate from a position where the surface of the wafer faces the UV-curable resin on the surface plate, thereby spreading the UV-curable resin on the surface of the wafer and coating the surface with the UV-curable resin. The wafer processing method according to claim 1, wherein in the protective film formation step, the ultraviolet-curable resin is irradiated with ultraviolet light through the surface platen.

3. The wafer processing method according to claim 1, wherein the coating step involves applying the ultraviolet-curable resin by spin coating.

4. The method for processing a wafer according to any one of claims 1 to 3, wherein the ultraviolet-curable resin comprises an acrylate, a photopolymerizing agent, and a light-absorbing material that absorbs the wavelength of the laser beam.

Images