Method of processing a wafer

Abstract

The present application provides a wafer processing method capable of suppressing a decrease in the bending strength of a device chip. The wafer processing method is a wafer processing method of a wafer having a functional layer on a front surface side, and includes: a laser processing step of removing the functional layer along a separation lane by irradiating a laser beam and forming a laser-processed groove along the separation lane; a cutting groove forming step of forming a cutting groove on the inner side of the laser-processed groove along the separation lane by cutting the wafer with a cutting tool; a grinding step of grinding the back surface side of the wafer to thin the wafer, exposing the cutting groove on the back surface side of the wafer, and dividing the wafer into a plurality of device chips; and a processing strain removing step of supplying a gas in a plasma state to the back surface side of the wafer and removing processing strains formed on the back surface side and the side portions of the plurality of device chips. In the processing strain removing step, a heat-affected layer formed on the periphery of the laser-processed groove is removed.

Description

TECHNICAL FIELD

[0001] The present application relates to a wafer processing method for a wafer having a functional layer constituting a plurality of devices. BACKGROUND

[0002] In a manufacturing process of a device chip, a wafer in which an IC (Integrated Circuit), an LSI (Large Scale Integration), or the like is formed on the front surface side of each of a plurality of regions divided by a plurality of spaced-apart streets (singulation predetermined lines) arranged in a lattice pattern is used. The wafer is singulated along the streets, and thus a plurality of device chips each having a device are obtained. The device chip is mounted on various electronic devices typified by mobile phones and personal computers.

[0003] In recent years, with the miniaturization and thinning of electronic devices, thinning of device chips is also required. Therefore, a process of thinning the wafer by grinding the back surface side of the wafer before singulation of the wafer is sometimes performed. The wafer is singulated after being thinned by grinding, and thus a thinned device chip is obtained.

[0004] In addition, as a method of singulating a wafer into a plurality of device chips while thinning the wafer, a process called dicing before grinding (DBG) is proposed (for example, refer to Patent Document 1). In the dicing before grinding process, first, a cutting tool is cut into the front surface side of the wafer, and a cutting groove (half-cut) having a depth smaller than the thickness of the wafer is formed along the streets. Then, the back surface side of the wafer is ground, and the wafer is thinned until the cutting groove is exposed on the back surface side of the wafer, and thus the wafer is singulated into a plurality of device chips. When the dicing before grinding process is used, an effect of being able to suppress generation of defects (chipping) on the back surface side of the wafer and the like is obtained.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2003-173987

[0006] When the wafer is singulated, a part of a layer (functional layer) including various films (insulating films, conductive films, and the like) constituting a device is sometimes left on the streets of the wafer. When the wafer is cut along the streets by a cutting tool, the functional layer is sometimes peeled off by being caught in the rotating cutting tool. Furthermore, when the peeling of the functional layer reaches the device from the street, there is a concern that the device is broken.

[0007] Therefore, a method in which the functional layer remaining on the separation lane is removed by irradiation of a laser beam before the wafer is cut by the cutting tool is sometimes used. Specifically, first, the functional layer is removed along the separation lane by irradiating a laser beam on the front surface side of the wafer. Then, the wafer is cut along the separation lane by the cutting tool to divide the wafer. When this method is used, the wafer is cut by the cutting tool in a state in which the functional layer is removed from the separation lane. Therefore, contact of the cutting tool with the functional layer is avoided, and breakage of the device due to peeling of the functional layer is prevented.

[0008] However, when the laser beam is irradiated along the separation lane, a laser-processed groove is formed on the wafer along the separation lane. Also, on the periphery of the laser-processed groove, a fine unevenness or a crack or the like, which is a strain, is formed due to the influence of heat generated by the irradiation of the laser beam. When the wafer including the region in which the strain (heat-affected layer) is formed is divided into a plurality of device chips, there is a problem that the heat-affected layer remains on the device chips to reduce the bending strength (flexural strength) of the device chips. SUMMARY

[0009] The present application was achieved in view of this problem, and an object thereof is to provide a wafer processing method capable of suppressing reduction in the bending strength of a device chip.

[0010] According to one embodiment of the present application, a wafer processing method is provided, the wafer having a functional layer constituting a plurality of devices on a front surface side, the plurality of devices being arranged in a plurality of regions divided by a plurality of separation lanes, wherein the wafer processing method has: a laser processing step of irradiating a laser beam having absorbency to the wafer on the front surface side of the wafer along the separation lane to form a laser-processed groove along the separation lane while removing the functional layer along the separation lane; a cutting groove forming step of cutting the front surface side of the wafer along the separation lane by a cutting tool thinner than a width of the laser-processed groove to form a cutting groove having a depth exceeding a finished thickness of the wafer inside the laser-processed groove along the separation lane; a protective member attaching step of attaching a protective member to the front surface side of the wafer after the cutting groove forming step is performed; a grinding step of holding the wafer by a chuck table of a grinding device through the protective member, grinding a back surface side of the wafer to thin the wafer until the thickness of the wafer becomes the finished thickness, to expose the cutting groove on the back surface side of the wafer to divide the wafer into a plurality of device chips; and a processing strain removing step of supplying a gas in a plasma state to the back surface side of the wafer to remove a processing strain formed on the back surface side and side portions of the plurality of device chips, in which the heat-affected layer formed on the periphery of the laser-processed groove is removed in the processing strain removing step.

[0011] Further, according to another aspect of the present application, there is provided a wafer processing method for a wafer having a functional layer constituting a plurality of devices on a front surface side, the plurality of devices being arranged in a plurality of regions divided by a plurality of separation lanes, the wafer processing method comprising: a laser processing step of irradiating a laser beam having absorbency to the wafer along the separation lanes to form laser processing grooves along the separation lanes by removing the functional layer along the separation lanes, the wafer being thinned by grinding the back surface side of the wafer until the thickness of the wafer becomes a finished thickness, thereby exposing the laser processing grooves on the back surface side of the wafer to divide the wafer into a plurality of device chips; a protective member attaching step of attaching a protective member to the front surface side of the wafer after the laser processing step; and a processing strain removing step of supplying a gas in a plasma state to the back surface side of the wafer to remove processing strains formed on the back surface side and side portions of the plurality of device chips, in which the heat-affected layer formed around the laser processing grooves is removed in the processing strain removing step.

[0012] Further, according to another aspect of the present application, there is provided a wafer processing method for a wafer having a functional layer constituting a plurality of devices on a front surface side, the plurality of devices being arranged in a plurality of regions divided by a plurality of separation lanes, the wafer processing method comprising: a laser processing step of irradiating a laser beam having absorbency to the wafer along the separation lanes to form laser processing grooves along the separation lanes by removing the functional layer along the separation lanes, the wafer being thinned by grinding the back surface side of the wafer until the thickness of the wafer becomes a finished thickness, thereby exposing the laser processing grooves on the back surface side of the wafer to divide the wafer into a plurality of device chips; a protective member attaching step of attaching a protective member to the front surface side of the wafer after the laser processing step; and a processing strain removing step of supplying a gas in a plasma state to the back surface side of the wafer to remove processing strains formed on the back surface side and side portions of the plurality of device chips, in which the heat-affected layer formed around the laser processing grooves is removed in the processing strain removing step.

[0013] In the wafer processing method of one embodiment of the present application, the heat-affected layer formed around the laser processing grooves is removed by supplying a gas in a plasma state to the wafer that has been divided into a plurality of device chips by the irradiation of the laser beam. Thus, the heat-affected layer can be prevented from remaining on the device chips, and the decrease in the bending strength of the device chips can be suppressed. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 (A) of FIG. 1 is a perspective view of a wafer, Figure 1 (B) of FIG. 1 is a cross-sectional view of the wafer.

[0015] Figure 2(A) is a partial sectional front view showing the wafer in a laser processing step, Figure 2 (B) is an enlarged plan view showing a portion of the wafer formed with a laser processed groove.

[0016] Figure 3 (A) is a partial sectional front view showing the wafer in a cutting groove forming step, Figure 3 (B) is an enlarged plan view showing a portion of the wafer formed with a cutting groove.

[0017] Figure 4 (A) is a perspective view showing the wafer in a protective member attaching step, Figure 4 (B) is a perspective view showing the wafer to which a protective member is attached.

[0018] Figure 5 (A) is a perspective view showing the wafer in a grinding step.

[0019] Figure 6 (A) is a sectional schematic view showing a plasma processing apparatus.

[0020] Figure 7 (B) is an enlarged sectional view showing a portion of the wafer to which a gas in a plasma state is supplied.

[0021] Figure 8 (A) is an enlarged sectional view showing a portion of the wafer formed with a laser processed groove, Figure 8 (B) is an enlarged sectional view showing a portion of the wafer after a heat affected layer around the laser processed groove is removed.

[0022] Figure 9 (A) is an enlarged sectional view showing a portion of the wafer formed with a laser separation groove, Figure 9 (B) is an enlarged sectional view showing a portion of the wafer after a heat affected layer around the laser separation groove is removed.

[0023] Explanation of Reference Numerals

[0024] 11: wafer; 11a: front surface; 11b: back surface; 11c: laser processing groove; 11d: cutting groove; 11e: heat affected layer (thermal strain layer); 11f: laser processing groove (laser separation groove); 11g: heat affected layer (thermal strain layer); 13: separation lane (separation predetermined line); 15: device; 17: functional layer (device layer); 19: protective member; 21: device chip; 10: laser processing apparatus; 12: chuck table (holding table); 12a: holding surface; 14: laser irradiation unit; 16: laser beam; 20: cutting apparatus; 22: chuck table (holding table); 22a: holding surface; 24: cutting unit; 26: spindle; 28: cutting tool; 40: grinding apparatus; 42: chuck table (holding table); 42a: holding surface; 44: grinding unit; 46: spindle; 48: mounting seat; 50: grinding wheel; 52: wheel base; 54: grinding tool; 60: plasma processing apparatus; 62: processing space; 64: chamber; 64a: bottom wall; 64b: upper wall; 64c: first side wall; 64d: second side wall; 64e: third side wall; 66: opening; 68: door; 70: opening and closing mechanism; 72: cylinder; 74: piston rod; 76: bracket; 78: exhaust port; 80: exhaust mechanism; 82: lower electrode; 84: upper electrode; 86: holding portion; 88: support portion; 90: opening; 92: insulating member; 94: high-frequency power source; 96: table; 98: flow path; 100: suction source; 102: cooling flow path; 104: refrigerant introduction path; 106: refrigerant circulation mechanism; 108: refrigerant discharge path; 110: gas ejection portion; 112: support portion; 114: opening; 116: insulating member; 118: high-frequency power source; 120: lifting mechanism; 122: support arm; 124: ejection port; 126: flow path; 128: flow path; 130: first gas supply source; 132: second gas supply source; 134: control portion (control unit, control device); 140: gas. DETAILED DESCRIPTION

[0025] Embodiments of the present application will be described below with reference to the accompanying drawings. First, a structure example of a wafer that can be processed by a wafer processing method of the present embodiment will be described. Figure 1 (A) is a perspective view of a wafer 11, Figure 1 (B) is a cross-sectional view of the wafer 11.

[0026] For example, wafer 11 is formed into a disk shape from silicon or the like, and has a front side 11a and a back side 11b. In addition, wafer 11 is divided into multiple rectangular regions by multiple spacer lines (predetermined dividing lines) 13 arranged in a grid pattern, and devices 15 such as IC (Integrated Circuit) and LSI (Large Scale Integration) are formed in these regions respectively.

[0027] Furthermore, there are no restrictions on the material, shape, structure, or size of the wafer 11. For example, the wafer 11 can be a substrate of any size and shape made of materials other than silicon, such as semiconductors (GaAs, InP, GaN, SiC, etc.), ceramics, resins, or metals. Additionally, there are no restrictions on the type, number, shape, structure, size, or arrangement of the devices 15 formed on the wafer 11.

[0028] like Figure 1 As shown in (B), a functional layer (device layer) 17 constituting multiple devices 15 is formed on the front side 11a of the wafer 11. This functional layer 17 contains various films (insulating films, conductive films, etc.) constituting the devices 15. For example, the functional layer 17 includes conductive films constituting electrodes or wiring of the devices 15, low-k insulating films constituting interlayer insulating films of the devices 15, and passivation films protecting the devices 15. The regions in the functional layer 17 divided by the spacers 13 correspond to the devices 15.

[0029] When wafer 11 is cut along spacer 13, wafer 11 is divided into multiple device chips, each containing a device 15. The dicing of wafer 11 may be performed using a cutting device, for example, that uses annular cutting tools to cut wafer 11. The cutting device includes: a chuck stage for holding wafer 11; and a cutting unit equipped with cutting tools for cutting wafer 11.

[0030] The cutting tool is rotated and cuts along the spacer 13 into the wafer 11 held by the chuck stage, thereby cutting the wafer 11 along the spacer 13. And, when the wafer 11 is cut along all the spacers 13, the wafer 11 is divided into multiple device chips.

[0031] However, as Figure 1As shown in (B), a part of the functional layer 17 is also formed on the street 13 of the wafer 11. Also, when the cutting tool is cut into the wafer 11 along the street 13, sometimes the functional layer 17 remaining on the street 13 is caught in the rotating cutting tool and peels off. For example, when a Low-k film included in the functional layer 17 remains on the street 13, the Low-k film is easily peeled off by the cutting tool. Also, when the peeling of the functional layer 17 reaches the device 15, there is a concern that the device 15 is broken.

[0032] Therefore, in the wafer processing method of the present embodiment, first, the wafer 11 is irradiated with a laser beam from the front surface 11a side along the street 13, thereby removing the functional layer 17 along the street 13 while forming a laser-processed groove along the street 13 (laser processing step). Figure 2 (A) is a partial cross-sectional front view of the wafer 11 in the laser processing step.

[0033] In the laser processing step, the wafer 11 is irradiated with a laser beam using a laser processing apparatus 10. The laser processing apparatus 10 has a chuck table (holding table) 12 which holds the wafer 11, and a laser irradiation unit 14 which irradiates the wafer 11 held by the chuck table 12 with a laser beam 16.

[0034] The upper surface of the chuck table 12 constitutes a holding surface 12a which holds the wafer 11. For example, the holding surface 12a is formed in a circular shape having a larger diameter than the wafer 11. However, the shape of the holding surface 12a is not limited, and is appropriately set according to the shape of the wafer 11. In addition, the holding surface 12a is connected to a suction source (not shown) such as an ejector via a flow path (not shown) formed in the inside of the chuck table 12.

[0035] In addition, the type and the configuration of the chuck table which holds the wafer 11 are not limited. For example, a chuck table which holds the wafer 11 by a mechanical method or an electrical method can be used instead of the chuck table 12.

[0036] A moving mechanism (not shown) and a rotating mechanism (not shown) are connected to the chuck table 12. The moving mechanism moves the chuck table 12 along a processing feed direction (first horizontal direction) and an indexing feed direction (second horizontal direction) which are perpendicular to each other. In addition, the rotating mechanism rotates the chuck table 12 about a rotation axis which is substantially parallel to the vertical direction (up-down direction).

[0037] A laser irradiation unit 14 is disposed above the chuck stage 12. The laser irradiation unit 14 irradiates the wafer 11 held by the chuck stage 12 with a laser beam 16 for processing the wafer 11. Specifically, the laser irradiation unit 14 includes a laser oscillator such as a YAG laser or a YVO4 laser; and a concentrator that focuses the laser beam pulsed by the laser oscillator at a predetermined position.

[0038] The wavelength of the laser beam 16 is set so that at least a portion of the laser beam 16 is absorbed by the wafer 11 (the laser beam 16 is absorptive to the wafer 11). In addition, the irradiation conditions of the laser beam 16 (power, spot diameter, repetition frequency, etc.) are set so that the wafer 11 is ablated when the laser beam 16 is irradiated.

[0039] In the laser processing step, the wafer 11 is first held by the chuck stage 12. Specifically, the wafer 11 is positioned according to the front side 11a (functional layer 17 side, reference). Figure 1 The wafer 11 is positioned on the chuck stage 12 with its (B) side exposed upwards and its back surface 11b facing the holding surface 12a. When a negative pressure from an attraction source is applied to the holding surface 12a in this state, the wafer 11 is attracted and held by the chuck stage 12. Alternatively, a protective tape or similar material can be attached to the back surface 11b side of the wafer 11 to protect it.

[0040] Next, the chuck table 12 is rotated to create a spacer track 13 (see reference). Figure 1 The length direction of (A) is approximately parallel to the machining feed direction. Additionally, the position of the chuck stage 12 is adjusted so that the focusing point of the laser beam 16 is positioned on the extension line of a spacer 13. Furthermore, the height of the focusing point of the laser beam 16 is adjusted so that the laser beam 16 converges on the front side 11a of the wafer 11.

[0041] And, as Figure 2 As shown in (A), while the laser beam 16 is irradiated from the laser irradiation unit 14, the chuck stage 12 is moved along the processing feed direction (in the direction indicated by arrow A). As a result, the laser beam 16 is irradiated along a spacer 13 onto the front side 11a of the wafer 11, and the wafer 11 is subjected to ablation processing.

[0042] When the laser beam 16 is irradiated onto the front side 11a of the wafer 11, the functional layer 17 (refer to...) Figure 1 (B) is removed along a spacer 13, and a laser processing groove 11c of a predetermined depth is formed linearly along a spacer 13 on the front side 11a of the wafer 11. In addition, the functional layer 17 can be removed by ablation based on irradiation by the laser beam 16, or it can be removed as a result of the formation of the laser processing groove 11c on the wafer 11.

[0043] Figure 2 (B) is an enlarged plan view showing a portion of the wafer 11 in which the laser-processed groove 11c is formed. When the laser beam 16 is irradiated along the division lane 13 to the wafer 11, the linear laser-processed groove 11c having a width smaller than the width of the division lane 13 (the interval of the adjacent devices 15) is formed on the wafer 11 along the division lane 13. Further, the width of the laser-processed groove 11c is adjusted by controlling, for example, the spot diameter of the laser beam 16.

[0044] In Figure 2 (B) of FIG. 11, the functional layer 17 is patterned in the region in which the laser-processed groove 11c is formed. Further, although the illustration is omitted in (B) of FIG. 11, by the irradiation of the laser beam 16, in the region in which the laser-processed groove 11c overlaps, the functional layer 17 (refer to (B) of FIG. 10) is removed. Figure 2 Figure 1 (B) of FIG. 11, by the irradiation of the laser beam 16, in the region in which the laser-processed groove 11c overlaps, the functional layer 17 (refer to (B) of FIG. 10) is removed.

[0045] Then, the same step is repeated to remove the functional layer 17 along all the division lanes 13, and the laser-processed groove 11c is formed. Thereby, the laser-processed groove 11c is formed in a lattice shape on the front surface 11a side of the wafer 11. Further, in the laser processing step, the laser beam 16 can be irradiated along each division lane 13 a plurality of times.

[0046] Further, in the laser processing step, a protective film can be formed on the front surface 11a side of the wafer 11 before the laser beam 16 is irradiated to the wafer 11. When the protective film is formed on the front surface 11a side of the wafer 11 and the laser beam 16 is irradiated to the wafer 11 through the protective film, it is possible to prevent the processing chips (chips) generated by the irradiation of the laser beam 16 from adhering to the front surface 11a side of the wafer 11. The protective film is removed after the formation of the laser-processed groove 11c is completed.

[0047] As the protective film, for example, a water-soluble resin such as PVA (polyvinyl alcohol), PEG (polyethylene glycol), or the like can be used. In the case where the protective film is composed of a water-soluble resin, the protective film can be easily removed by supplying pure water or the like to the front surface 11a side of the wafer 11.

[0048] Next, the front surface 11a side of the wafer 11 is cut along the division lane 13 with a cutting tool, and thereby a cutting groove is formed inside the laser-processed groove 11c along the division lane 13 (cutting groove formation step). Figure 3 (A) of FIG. 12 is a partial cross-sectional front view showing the wafer 11 in the cutting groove formation step.

[0049] ​In the cutting groove forming step, the wafer 11 is cut using a cutting device 20. The cutting device 20 has a chuck table (holding table) 22 which holds the wafer 11, and a cutting unit 24 which cuts the wafer 11 held by the chuck table 22.

[0050] The upper surface of the chuck table 22 constitutes a holding surface 22a which holds the wafer 11. The holding surface 22a is formed, for example, in a circular shape having a larger diameter than the wafer 11. However, the shape of the holding surface 22a is not limited, and is appropriately set according to the shape of the wafer 11. In addition, the holding surface 22a is connected to a suction source (not shown) such as an ejector via a flow path (not shown) formed in the inside of the chuck table 22.

[0051] In addition, the type and configuration of the chuck table which holds the wafer 11 are not limited. For example, a chuck table which holds the wafer 11 by a mechanical method or an electrical method, or the like can be used instead of the chuck table 22.

[0052] A moving mechanism (not shown) and a rotating mechanism (not shown) are connected to the chuck table 22. The moving mechanism moves the chuck table 22 in the machining feed direction (the front-and-rear direction in (A) of FIG. 1). In addition, the rotating mechanism rotates the chuck table 22 about a rotation axis which is substantially parallel to the vertical direction. Figure 3

[0053] The cutting unit 24 has a cylindrical main shaft 26 which is disposed in a direction which is substantially parallel to the holding surface 22a and substantially perpendicular to the machining feed direction. An annular cutting tool 28 which cuts the wafer 11 is attached to the front end portion (one end portion) of the main shaft 26. The cutting tool 28 is constituted, for example, by an electrocast abrasive tool which is formed by fixing diamond abrasive grains with nickel plating.

[0054] A rotating drive source (not shown) such as a motor is connected to the base end portion (the other end portion) of the main shaft 26. When the main shaft 26 is rotated by the rotating drive source, the cutting tool 28 attached to the main shaft 26 is rotated.

[0055] In addition, a moving mechanism (not shown) is connected to the cutting unit 24. The moving mechanism moves the cutting unit 24 in the indexing feed direction (the left-and-right direction in (A) of FIG. 1) and the vertical direction. The position in the indexing feed direction of the cutting tool 28 and the height (cutting depth) of the cutting tool 28 are adjusted by the moving mechanism. Figure 3

[0056] ​​In the cutting groove forming step, the wafer 11 is first held by the chuck table 22. Specifically, the wafer 11 is arranged on the chuck table 22 with the front surface 11a side facing upward and the back surface 11b side facing the holding surface 22a. When a negative pressure of the suction source is applied to the holding surface 22a in this state, the wafer 11 is held by the chuck table 22. Alternatively, a protective tape or the like that protects the wafer 11 can be attached to the back surface 11b side of the wafer 11.

[0057] Next, the chuck table 22 is rotated so that the length direction of the one space lane 13 is substantially parallel to the machining feed direction. In addition, the height of the cutting unit 24 is adjusted so that the lower end of the cutting tool 28 is arranged at a position that is lower than the bottom of the laser-processed groove 11c and higher than the back surface 11b of the wafer 11. In addition, the position of the indexing feed direction of the cutting unit 24 is adjusted so that the cutting tool 28 is arranged on the extension line of the one space lane 13.

[0058] In this state, the chuck table 22 is moved along the machining feed direction while the cutting tool 28 is rotated. Thus, the cutting tool 28 cuts into the front surface 11a side of the wafer 11 along the space lane 13, and a linear cutting groove 11d is formed in the wafer 11 along the space lane 13.

[0059] In addition, in the cutting groove forming step, a cutting tool 28 that is thinner (smaller in width) than the laser-processed groove 11c formed in the wafer 11 is used. Furthermore, the cutting tool 28 is moved so that the entire cutting tool 28 overlaps the laser-processed groove 11c and passes between the both ends in the width direction of the laser-processed groove 11c (inside the laser-processed groove 11c) when viewed from above.

[0060] Therefore, the cutting tool 28 does not come into contact with the pair of side surfaces of the wafer 11 that are exposed inside the laser-processed groove 11c and cuts into the bottom of the laser-processed groove 11c. As a result, the cutting groove 11d that is smaller in width than the laser-processed groove 11c is formed inside the laser-processed groove 11c toward the back surface 11b side of the wafer 11 from the bottom of the laser-processed groove 11c when viewed from above.

[0061] In addition, the cutting depth of the cutting tool 28 (the difference in height between the front surface 11a of the wafer 11 and the lower end of the cutting tool 28) is set to be greater than the thickness of the wafer 11 after grinding by the grinding step described later (the target value of the thickness of the wafer 11 in the grinding step). Therefore, the depth of the cutting groove 11d (the difference in height between the front surface 11a of the wafer 11 and the bottom of the cutting groove 11d) is greater than the finished thickness of the wafer 11.

[0062] Figure 3(B) is an enlarged plan view showing a portion of the wafer 11 in which the cutting groove 11d is formed. When the wafer 11 is cut along the separation lane 13 by the cutting tool 28, the cutting groove 11d having a width smaller than that of the laser-processed groove 11c is formed on the inner side of the laser-processed groove 11c along the separation lane 13 on the separation lane 13. In Figure 3 (B) of FIG. 11, a different pattern is formed in the region in which the cutting groove 11d is formed from the region in which the laser-processed groove 11c is formed.

[0063] Here, in the laser processing step described above, the functional layer 17 (see Figure 1 (B)) is removed in the region overlapping the laser-processed groove 11c. Therefore, when the inner side of the laser-processed groove 11c is cut by the cutting tool 28, contact of the cutting tool 28 with the functional layer 17 does not occur. Thus, peeling of the functional layer 17 due to entanglement with the rotating cutting tool 28 can be prevented.

[0064] Then, the same step is repeated to form the cutting groove 11d along all the separation lanes 13. Thus, the cutting groove 11d having a depth exceeding the finished thickness of the wafer 11 is formed in a lattice shape on the front surface 11a side of the wafer 11 along the separation lanes 13.

[0065] Next, a protective member is attached to the front surface 11a side of the wafer 11 (protective member attachment step). Figure 4 (A) is a perspective view showing the wafer 11 in the protective member attachment step.

[0066] In the protective member attachment step, for example, a protective member 19 formed in a circular shape having the same diameter as the wafer 11 is attached to the front surface 11a side of the wafer 11. The protective member 19 is attached to the wafer 11 in such a manner as to cover the entire front surface 11a side of the wafer 11.

[0067] As the protective member 19, for example, a protective tape composed of a soft resin is used. Specifically, the protective member 19 has a circular base material and an adhesive layer (paste layer) provided on the base material. The base material is composed of a resin such as polyolefin, polyvinyl chloride, polyethylene terephthalate, and the like, and the adhesive layer is composed of an adhesive such as an epoxy-based, acrylic-based, or rubber-based adhesive, or the like. Alternatively, an ultraviolet-hardening resin that is hardened by irradiation of ultraviolet rays can be used for the adhesive layer.

[0068] However, the material of the protective member 19 is not limited as long as the protective member 19 can protect the front surface 11a side of the wafer 11 and the plurality of devices 15. For example, the protective member 19 can be a high-rigidity substrate composed of silicon, glass, ceramic, or the like, formed in a plate shape.

[0069] Figure 4(B) is a perspective view showing the wafer 11 to which the protection member 19 is attached. The front surface 11a side of the wafer 11 and the plurality of devices 15 are protected by the protection member 19 during a process (grinding step, machining strain removal step, etc.) after the implementation.

[0070] Next, the wafer 11 is thinned by grinding the back surface lib side of the wafer 11, and the cutting groove lid is exposed on the back surface lib to divide the wafer 11 into a plurality of device chips (grinding step). Figure 5 is a front view showing the wafer 11 in the grinding step.

[0071] In the grinding step, the wafer 11 is ground using a grinding device 40. The grinding device 40 has a chuck table (holding table) 42 that holds the wafer 11, and a grinding unit 44 that grinds the wafer 11 held by the chuck table 42.

[0072] The upper surface of the chuck table 42 constitutes a holding surface 42a that holds the wafer 11. The holding surface 42a is formed, for example, in a circular shape having a larger diameter than the wafer 11. However, the shape of the holding surface 42a is not limited, and is appropriately set according to the shape of the wafer 11. In addition, the holding surface 42a is connected to a suction source (not shown) such as an ejector via a flow path (not shown) formed in the inside of the chuck table 42.

[0073] In addition, the type and configuration of the chuck table that holds the wafer 11 are not limited. For example, a chuck table that holds the wafer 11 by a mechanical method or an electrical method, etc. can be used instead of the chuck table 42.

[0074] A moving mechanism (not shown) and a rotating mechanism (not shown) are connected to the chuck table 42. The moving mechanism moves the chuck table 42 in the horizontal direction. In addition, the rotating mechanism rotates the chuck table 42 about a rotation axis that is substantially parallel to the vertical direction.

[0075] The grinding unit 44 has a cylindrical housing (not shown) that moves in the vertical direction by a moving mechanism (elevation mechanism, not shown), and a cylindrical spindle 46 that is a rotation axis is housed in the housing. The front end portion (lower end portion) of the spindle 46 protrudes downward from the lower end of the housing, and a disc-shaped mounting seat 48 made of metal, etc. is fixed to the front end portion.

[0076] A grinding wheel 50 having substantially the same diameter as the mounting seat 48 is mounted on the lower surface side of the mounting seat 48. The grinding wheel 50 has a circular ring-shaped grinding wheel base 52 made of a metal such as stainless steel or aluminum. Further, a plurality of grinding tools 54 formed in a cuboid shape are fixed to the lower surface side of the grinding wheel base 52 at substantially equal intervals along the outer periphery of the grinding wheel base 52. The lower surfaces of the plurality of grinding tools 54 are brought into contact with the wafer 11, thereby grinding the wafer 11.

[0077] A rotary drive source (not shown) such as a motor is connected to the base end portion (upper end portion) of the spindle 46. The grinding wheel 50 is rotated about a rotational axis substantially parallel to the vertical direction by a rotational force transmitted from the rotary drive source via the spindle 46 and the mounting seat 48.

[0078] Further, a nozzle (not shown) that supplies a grinding liquid such as pure water to the wafer 11 held by the chuck table 42 is provided in the vicinity of the grinding unit 44. The grinding liquid is supplied from the nozzle toward the wafer 11 and the plurality of grinding tools 54 when the wafer 11 is ground by the plurality of grinding tools 54.

[0079] In the grinding step, first, the wafer 11 is held by the chuck table 42. Specifically, the wafer 11 is arranged on the chuck table 42 in such a manner that the front surface 11a side faces the holding surface 42a and the back surface 11b side is exposed upward. When a negative pressure of a suction source is applied to the holding surface 42a in this state, the wafer 11 is held by suction by the chuck table 42.

[0080] Next, the chuck table 42 holding the wafer 11 is moved to the lower side of the grinding unit 44. Further, the chuck table 42 and the grinding wheel 50 are rotated at predetermined rotational speeds in predetermined directions, respectively, and the grinding wheel 50 is lowered toward the chuck table 42. The lowering speed of the grinding wheel 50 at this time is adjusted so that the plurality of grinding tools 54 press the back surface 11b side of the wafer 11 with a proper force.

[0081] When the lower surfaces of the plurality of grinding tools 54 rotating in contact with the back surface 11b side of the wafer 11, the back surface 11b side of the wafer 11 is scraped. Thus, the wafer 11 is subjected to a grinding process, and the wafer 11 is thinned. Further, when the wafer 11 is thinned to a predetermined thickness (finished thickness), the grinding of the wafer 11 is completed.

[0082] Further, the grinding liquid is supplied from the nozzle toward the wafer 11 and the plurality of grinding tools 54 when the wafer 11 is ground by the plurality of grinding tools 54. The wafer 11 and the plurality of grinding tools 54 are cooled by the grinding liquid, and chips (grinding chips) generated by the grinding of the wafer 11 are washed away.

[0083] When the wafer 11 is thinned to a thickness of the wafer 11 to be a finished thickness, the cutting groove 11d formed along the separation groove 13 is exposed on the back surface lib of the wafer 11 (see Figure 5 ). Thus, the wafer 11 is divided into a plurality of device chips 21 each having the device 15.

[0084] Next, a gas in a plasma state is supplied to the back surface lib side of the wafer 11, and processing strain formed on the back surface and side portions of the plurality of device chips 21 is removed (processing strain removal step).

[0085] When the laser processing step (see (A) of Figure 2 ) is performed, sometimes, a fine unevenness or a crack or the like strain (processing strain) formed by irradiation of the laser beam 16 remains on the periphery of the laser-processed groove 11c. For example, after the laser processing step is performed, the side surface of the wafer 11 exposed inside the laser-processed groove 11c and the periphery thereof or the like remains the processing strain.

[0086] In addition, when the cutting groove formation step (see (A) of Figure 3 ) is performed, sometimes, a fine unevenness or a crack or the like strain (processing strain) formed by contact with the cutting tool 28 remains on the periphery of the cutting groove 11d. For example, after the cutting groove formation step is performed, the side surface of the wafer 11 exposed inside the cutting groove 11d and the periphery thereof or the like remains the processing strain.

[0087] In addition, when the grinding step (see Figure 5 ) is performed, sometimes, a fine unevenness or a crack or the like strain (processing strain) formed by contact with the plurality of grinding tools 54 remains on the back surface lib side of the wafer 11.

[0088] When the wafer 11 including the above processing strain is divided to manufacture a plurality of device chips 21, the processing strain remains on the device chips 21. Also, the bending strength (flexural strength) of the device chips 21 is reduced due to the processing strain, and thus the quality of the device chips 21 is reduced. Therefore, in the present embodiment, the wafer 11 divided into the plurality of device chips 21 is subjected to plasma processing, and thus the processing strain is removed.

[0089] In the processing strain removal step, the wafer 11 is subjected to plasma processing using a plasma processing device. Figure 6 is a cross-sectional schematic view showing a plasma processing device 60.

[0090] The plasma processing apparatus 60 has a chamber 64 that forms a processing space 62 in which plasma processing is performed. The chamber 64 is formed in a rectangular parallelepiped shape including a bottom wall 64a, an upper wall 64b, a first side wall 64c, a second side wall 64d, a third side wall 64e, and a fourth side wall (not shown). In addition, an opening 66 for carrying in and out the wafer 11 is provided in the second side wall 64d.

[0091] A door 68 that opens and closes the opening 66 is provided outside the opening 66. The door 68 is connected to an opening and closing mechanism 70 that moves the door 68 in the vertical direction (up and down direction). The opening and closing mechanism 70 is constituted by, for example, a cylinder 72 having a piston rod 74. The upper end of the piston rod 74 is connected to the lower portion of the door 68. In addition, the cylinder 72 is fixed to the bottom wall 64a of the chamber 64 by means of a bracket 76.

[0092] The door 68 is lowered by the opening and closing mechanism 70 to expose the opening 66, so that the wafer 11 can be carried into the processing space 62 of the chamber 64 through the opening 66, or carried out of the processing space 62 of the chamber 64 through the opening 66.

[0093] In addition, an exhaust port 78 that connects the inside and outside of the chamber 64 is formed in the bottom wall 64a of the chamber 64. An exhaust mechanism 80 for depressurizing the processing space 62 is connected to the exhaust port 78. The exhaust mechanism 80 is constituted by, for example, a vacuum pump.

[0094] In the processing space 62 of the chamber 64, a lower electrode 82 and an upper electrode 84 are arranged in a mutually opposing manner. The lower electrode 82 is constituted by an electrically conductive material, and includes a disc-shaped holding portion 86 and a cylindrical support portion 88 that protrudes downward from the central portion of the lower surface of the holding portion 86.

[0095] The support portion 88 is inserted into an opening 90 formed in the bottom wall 64a of the chamber 64. An annular insulating member 92 is arranged between the bottom wall 64a inside the opening 90 and the support portion 88, and the chamber 64 is insulated from the lower electrode 82 by the insulating member 92. In addition, the lower electrode 82 is connected to a high-frequency power source 94 outside the chamber 64.

[0096] A recess is formed on the upper surface side of the holding portion 86, and a stage 96 on which the wafer 11 is placed is provided in the recess. The upper surface of the stage 96 constitutes a holding surface that holds the wafer 11. In addition, a flow path (not shown) is formed in the inside of the stage 96, and the upper surface of the stage 96 is connected to a suction source 100 such as an ejector via the flow path and a flow path 98 formed in the inside of the lower electrode 82.

[0097] In addition, a cooling flow path 102 is formed inside the holding portion 86. One end side of the cooling flow path 102 is connected to a refrigerant circulation mechanism 106 via a refrigerant introduction path 104 formed in the support portion 88. In addition, the other end side of the cooling flow path 102 is connected to the refrigerant circulation mechanism 106 via a refrigerant discharge path 108 formed in the support portion 88. When the refrigerant circulation mechanism 106 is caused to operate, the refrigerant flows in the order of the refrigerant introduction path 104, the cooling flow path 102, and the refrigerant discharge path 108 to cool the lower electrode 82.

[0098] The upper electrode 84 is composed of an electrically conductive material, and includes a disc-shaped gas ejection portion 110 and a cylindrical support portion 112 protruding upward from a central portion of an upper surface of the gas ejection portion 110. The support portion 112 is inserted into an opening 114 formed in an upper wall 64b of the chamber 64. An annular insulating member 116 is disposed between the upper wall 64b inside the opening 114 and the support portion 112, and insulates the chamber 64 and the upper electrode 84 by the insulating member 116. In addition, the upper electrode 84 is connected to a high-frequency power source 118 outside the chamber 64.

[0099] A support arm 122 connected to a lifting mechanism 120 is attached to an upper end portion of the support portion 112. The upper electrode 84 is moved in the vertical direction (upward and downward direction) by the lifting mechanism 120 and the support arm 122.

[0100] A plurality of ejection ports 124 are provided on the lower surface side of the gas ejection portion 110. The ejection ports 124 are connected to a first gas supply source 130 and a second gas supply source 132 via a flow path 126 formed inside the gas ejection portion 110 and a flow path 128 formed inside the support portion 112. The first gas supply source 130 and the second gas supply source 132 can supply gases having different compositions to the flow path 128.

[0101] The constituent elements (the opening and closing mechanism 70, the exhaust mechanism 80, the high-frequency power source 94, the suction source 100, the refrigerant circulation mechanism 106, the high-frequency power source 118, the lifting mechanism 120, the first gas supply source 130, the second gas supply source 132, and the like) of the plasma processing apparatus 60 are connected to a control portion (control unit, control device) 134 that controls the plasma processing apparatus 60. The control portion 134 is composed of a computer or the like, and controls the operation of each of the constituent elements of the plasma processing apparatus 60.

[0102] In the processing strain removal step, first, the door 68 of the plasma processing apparatus 60 is lowered by the opening / closing mechanism 70, and the opening 66 is exposed. Further, the wafer 11 is carried into the processing space 62 of the chamber 64 through the opening 66 by a carrying mechanism (not shown) and is placed on the stage 96. At this time, the wafer 11 is placed in a manner that the back surface lib side is exposed upward (the upper electrode 84 side). In addition, at the time of carrying in the wafer 11, it is preferable to previously raise the upper electrode 84 by the elevation mechanism 120 to expand the interval between the lower electrode 82 and the upper electrode 84.

[0103] Next, the wafer 11 is suction-held by the stage 96 by applying negative pressure of the suction source 100 to the upper surface of the stage 96. In addition, the door 68 is raised by the opening / closing mechanism 70 to close the opening 66, and thus the processing space 62 is sealed. Further, the height position of the upper electrode 84 is adjusted by the elevation mechanism 120 to make the upper electrode 84 and the lower electrode 82 have a prescribed positional relationship suitable for plasma processing. Further, the exhaust mechanism 80 is operated to make the processing space 62 a reduced pressure state (for example, 50 Pa or more and 300 Pa or less).

[0104] In addition, in a case where it is difficult to hold the wafer 11 on the stage 96 by the negative pressure of the suction source 100 at the time of reducing the pressure of the processing space 62, the wafer 11 is held on the stage 96 by power (representatively, electrostatic attraction) or the like. For example, a plurality of electrodes are embedded in the inside of the stage 96, a prescribed voltage is applied to the electrodes, and thus Coulomb force is applied between the stage 96 and the wafer 11 to make the wafer 11 adhere to the stage 96. That is, the stage 96 functions as an electrostatic chuck stage.

[0105] Further, the gas for etching (etching gas) is supplied from the first gas supply source 130 to between the lower electrode 82 and the upper electrode 84 through the flow path 128, the flow path 126, and the plurality of discharge ports 124. In addition, a prescribed high-frequency power (for example, 1000 W or more and 3000 W or less) is applied to the lower electrode 82 and the upper electrode 84. As a result, the gas existing between the lower electrode 82 and the upper electrode 84 is plasma-ized, and the gas in the plasma state is supplied to the back surface lib side of the wafer 11.

[0106] Figure 7 is an enlarged sectional view showing a part of the wafer 11 to which the gas in the plasma state is supplied. The gas 140 discharged from the plurality of discharge ports 124 becomes the plasma state including ions and radicals between the lower electrode 82 and the upper electrode 84. Further, the gas 140 in the plasma state is supplied to the back surface lib side of the wafer 11 which has been divided into a plurality of device chips 21. As a result, the gas 140 in the plasma state acts on the wafer 11, and the wafer 11 is subjected to plasma etching.

[0107] Further, the composition of the gas 140 is not limited, and is appropriately selected in accordance with the material of the wafer 11. For example, in the case where the wafer 11 is a silicon wafer, a gas 140 containing a fluorine-based gas such as CF4, SF6, or the like can be used.

[0108] The gas 140 in the plasma state is irradiated to the back surface lib of the wafer 11, and enters the gap between the adjacent device chips 21 (laser-processed grooves lie and cutting grooves lid). Thereby, the processing strain formed on the back surface lib side of the wafer 11 (corresponding to the back surface side of the device chip 21) and the processing strain formed on the side portion of the wafer 11 exposed between the adjacent device chips 21 (corresponding to the side portion of the device chip 21) are removed by plasma etching.

[0109] Here, in the above laser processing step (refer to Figure 2 (A)), due to heat generated by irradiation of the laser beam 16, processing strain such as unevenness due to thermal strain is easily formed particularly in the periphery of the laser-processed groove lie. Further, when a region (heat-affected layer, thermal strain layer) in which the processing strain due to the heat is formed is left on the wafer 11, the bending strength of the device chip 21 is adversely affected.

[0110] Figure 8 (A) is an enlarged sectional view showing a portion of the wafer 11 in which the laser-processed groove lie is formed. A heat-affected layer (thermal strain layer) lie remains in the periphery of the laser-processed groove lie due to irradiation of the laser beam 16. In Figure 8 (A) of FIG. 10, a case where the heat-affected layer lie remains along both side ends (a pair of side surfaces of the wafer 11 exposed inside the laser-processed groove lie) of the laser-processed groove lie and the bottom of the laser-processed groove lie is shown. The heat-affected layer lie is formed to a prescribed thickness (for example, 20 μm or less) in accordance with the irradiation conditions of the laser beam 16.

[0111] When the gas 140 in the plasma state is supplied to the wafer 11 in which the heat-affected layer lie is formed, the gas 140 enters the cutting groove lid from the back surface lib side of the wafer 11, and reaches the laser-processed groove lie. Further, the heat-affected layer lie formed in the periphery of the laser-processed groove lie is subjected to plasma etching by the gas 140, and thereby the heat-affected layer lie is removed.

[0112] Figure 8 (B) is an enlarged sectional view showing a portion of the wafer 11 in which the heat-affected layer lie in the periphery of the laser-processed groove lie is removed. The heat-affected layer lie is removed by supplying the gas 140 in the plasma state, and thereby the reduction in the bending strength of the device chip 21 is suppressed.

[0113] In addition, a strain layer (defect-removing layer) can be formed on the back surface 11b side of the wafer 11 after the above-described processing strain removal step. This strain layer corresponds to a region in which a finer concave-convex or a crack than the processing strain formed in the wafer 11 in the above-described laser processing step and the cutting groove formation step is formed.

[0114] It is confirmed that when the strain layer is present on the back surface 11b side of the wafer 11, a defect-removing effect in which a metal element (copper or the like) present in the inside of the wafer 11 is captured by the strain layer is obtained. Therefore, when the strain layer is formed on the back surface 11b side of the wafer 11, the metal element is less likely to move to the front surface 11a side of the wafer 11 on which the plurality of devices 15 are formed, and malfunction of the devices 15 due to the metal element (leakage of current or the like) is less likely to occur.

[0115] In the formation of the strain layer, the plasma processing apparatus 60 (refer to FIG. 2) can be used. Figure 6 For example, the inert gas is made into a plasma state by the plasma processing apparatus 60 and supplied to the back surface 11b side of the wafer 11, whereby the strain layer is formed.

[0116] Specifically, after the removal of the processing strain is completed in the processing strain removal step, the supply of the etching gas from the first gas supply source 130 to the chamber 64 is stopped. Meanwhile, the inert gas (for example, a rare gas such as He, Ar, or the like) is supplied from the second gas supply source 132 to the chamber 64, and predetermined high-frequency power is applied to the lower electrode 82 and the upper electrode 84.

[0117] Thus, the inert gas is ionized between the lower electrode 82 and the upper electrode 84, and the inert gas in a plasma state is irradiated to the back surface 11b of the wafer 11. As a result, the back surface 11b of the wafer 11 is sputtered, and a fine concave-convex or a crack (strain) is formed on the back surface 11b. The region in which this strain is formed (strain layer) functions as a defect-removing layer that captures a metal element contained in the inside of the wafer 11.

[0118] In addition, the thickness of the strain layer formed by the plasma processing using the inert gas is extremely small. For example, the thickness of the strain layer is 1 / 10 or less of the thickness of the processing strain formed in the wafer 11 in the laser processing step and the cutting groove formation step. Therefore, the strain layer has a small influence on the bending strength of the device chip 21.

[0119] As described above, in the wafer processing method of the present embodiment, the heat-affected layer 11e formed around the laser-processed groove 11c is removed by supplying a gas in a plasma state to the wafer 11 that has been divided into a plurality of device chips 21 through irradiation of the laser beam 16. Thus, it is possible to prevent the heat-affected layer 11e from remaining on the device chips 21, and it is possible to suppress a decrease in the bending strength of the device chips 21.

[0120] Further, in the above-described embodiment, an example in which the laser-processed groove 11c and the cutting groove 11d are formed on the wafer 11 (see FIGS. 8(A) and 8(B) of Figure 2 Figure 3 However, in the laser processing step, the laser-processed groove 11c having a depth exceeding the finished thickness of the wafer 11 can be formed along the separation lane 13 through irradiation of the laser beam 16.

[0121] When the wafer 11 in which the laser-processed groove 11c having a depth exceeding the finished thickness of the wafer 11 is formed is thinned until the thickness of the wafer 11 becomes the finished thickness (grinding step), the laser-processed groove 11c is exposed on the back surface 11b side of the wafer 11. Thus, the wafer 11 is divided into a plurality of device chips 21.

[0122] As described above, when the depth of the laser-processed groove 11c is made greater than the finished thickness of the wafer 11, the process of cutting the wafer 11 with the cutting tool 28 (cutting groove forming step) can be omitted. Thus, it is not necessary to perform preparation and operation of the cutting device 20, and the number of man-hours is reduced.

[0123] Further, in the laser processing step, the laser-processed groove extending from the front surface 11a to the back surface 11b of the wafer 11 can be formed along the separation lane 13 through irradiation of the laser beam 16. In this case, the wafer 11 is divided along the separation lane 13 through irradiation of the laser beam 16.

[0124] Figure 9 FIG. 8(A) is an enlarged sectional view showing a portion of the wafer 11 in which the laser-processed groove (laser division groove) 11f extending from the front surface 11a to the back surface 11b of the wafer 11 is formed. When the laser-processed groove 11f is formed along the separation lane 13 through irradiation of the laser beam 16, the wafer 11 is divided along the separation lane 13. That is, in the laser processing step, the wafer 11 is divided into a plurality of device chips 21.

[0125] ​When the laser processing groove 11f is formed in the laser processing step, the cutting groove 11d can be formed without it, and the cutting groove forming step can be omitted. Furthermore, the grinding step is performed after the wafer 11 has been divided into multiple device chips 21, grinding the back side of each of the multiple device chips 21. However, if the thickness of the device chips 21 obtained in the laser processing step is already within the desired range, the grinding step can be omitted.

[0126] Furthermore, when a laser processing groove 11f is formed by irradiation with laser beam 16, a heat-affected layer (thermal strain layer) 11g is formed around the laser processing groove 11f. Figure 9 (A) shows the presence of residual heat-affected layer 11g along the two sides of the laser processing tank 11f (a pair of sides of the wafer 11 exposed inside the laser processing tank 11f).

[0127] When using plasma processing device 60 (refer to) Figure 6 When plasma gas 140 is supplied to the back surface 11b side of the wafer 11 on which the heat-affected layer 11g is formed, the plasma gas 140 enters the laser processing tank 11f. As a result, the heat-affected layer 11g formed around the laser processing tank 11f is removed (heat-affected layer removal step). Figure 9 (B) is an enlarged cross-sectional view showing a portion of the wafer 11 after the heat-affected layer 11g around the laser processing groove 11f has been removed.

[0128] In addition, it is sometimes difficult to form a laser processing groove 11c with a depth exceeding the finished thickness of the wafer 11 or a laser processing groove 11f from the front side 11a to the back side 11b of the wafer 11 by a single irradiation with a laser beam 16. In this case, the laser processing grooves 11c and 11f are formed by irradiating the respective spacers 13 with multiple laser beams 16.

[0129] Furthermore, in the above embodiment, the plasma processing apparatus 60 (refer to) that ionizes the gas supplied to the chamber 64 inside the chamber 64 is described. Figure 6 The description is provided. However, the plasma processing apparatus 60 may also supply plasma-ionized gas from the outside of the chamber 64 to the inside of the chamber 64.

[0130] It was confirmed that when plasma-ionized gas from the outside of chamber 64 is introduced into chamber 64 and supplied to wafer 11, the gas easily enters the gaps formed on wafer 11 (laser processing grooves 11c, 11f, cutting grooves 11d, etc.). It is speculated that this is because when plasma-state gas is introduced from the outside of chamber 64 into the inside via piping, the ions contained in the gas are expelled by adsorption onto the inner wall of the piping, and the gas with a higher proportion of free radicals is supplied to wafer 11.

[0131] Therefore, when the gas that is plasmaized outside the chamber 64 is supplied to the wafer 11, the gas in the plasma state easily travels inside the laser processing grooves 11c, 11f, the cutting grooves 11d toward the front surface 11a of the wafer 11. Thus, it is easy to remove the processing strain (for example, the heat affected layer 11e shown in (A) of FIG. 10, etc.) formed on the front surface 11a side of the wafer 11. Figure 8

[0132] In addition, the configuration, the method, etc. of the above-described embodiments can be appropriately changed and implemented as long as the scope of the object of the present application is not deviated.​

Claims

1. A wafer processing method, the wafer having a functional layer constituting a plurality of devices on a front surface side, the plurality of devices being arranged in a plurality of regions divided by a plurality of division lines, characterized by comprising: a laser processing step of irradiating a laser beam having absorbency to the wafer on the front surface side of the wafer along the division lines to form laser processed grooves along the division lines while removing the functional layer along the division lines; a cutting groove forming step of cutting the front surface side of the wafer along the division lines using a cutting tool thinner than a width of the laser processed grooves to form cutting grooves having a depth exceeding a finished thickness of the wafer on an inner side of the laser processed grooves along the division lines; a protective member attaching step of attaching a protective member to the front surface side of the wafer after the cutting groove forming step; a grinding step of holding the wafer by a chuck table of a grinding device through the protective member to grind a back surface side of the wafer to thin the wafer until the thickness of the wafer becomes the finished thickness, thereby exposing the cutting grooves on the back surface side of the wafer to divide the wafer into a plurality of device chips; and a processing strain removing step of supplying a gas in a plasma state to the back surface side of the wafer to remove processing strains formed on the back surface side and side portions of the plurality of device chips, wherein in the processing strain removing step, a heat affected layer remaining along both side ends and a bottom of the laser processed grooves is removed.

2. The wafer processing method according to claim 1, wherein in the processing strain removing step, the gas in the plasma state is supplied to the back surface side of the wafer in a direction directly opposite to the back surface side of the wafer from directly above the back surface side of the wafer to smoothly irradiate the gas in the plasma state to the back surface of the wafer in a direction perpendicular to the back surface of the wafer and into gaps between adjacent device chips, thereby removing the processing strains formed on the back surface side of the plurality of device chips and side portions exposed to the gaps between the adjacent device chips.

3. A wafer processing method, the wafer having a functional layer constituting a plurality of devices on a front surface side, the plurality of devices being arranged in a plurality of regions divided by a plurality of division lines, characterized by comprising: a laser processing step of irradiating a laser beam having absorbency to the wafer on the front surface side of the wafer along the division lines to form laser processed grooves having a depth exceeding a finished thickness of the wafer along the division lines while removing the functional layer along the division lines; a protective member attaching step of attaching a protective member to the front surface side of the wafer after the laser processing step; a grinding step of holding the wafer by a chuck table of a grinding device through the protective member to grind a back surface side of the wafer to thin the wafer until the thickness of the wafer becomes the finished thickness, thereby exposing the laser processed grooves on the back surface side of the wafer to divide the wafer into a plurality of device chips; and ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ In the process strain removal step, a plasma gas is supplied to the back side of the wafer from directly above it in a direction opposite to the back side of the wafer. This plasma gas is then directed perpendicularly to the back side of the wafer and smoothly irradiates the back side of the wafer, penetrating into the gaps between adjacent device chips. This process removes the processing strain formed on the back sides of the multiple device chips and on the exposed sides in the gaps between adjacent device chips. In this processing strain removal step, the heat-affected layer formed around the laser processing tank is removed.

4. A method for processing a wafer, the wafer having a functional layer constituting a plurality of devices on its front side, the plurality of devices being disposed in a plurality of regions divided by a plurality of spacers, characterized in that, The wafer fabrication method comprises the following steps: In the laser processing step, a laser beam that absorbs the wafer is irradiated along the spacer, thereby removing the functional layer along the spacer and forming a laser processing groove along the spacer to divide the wafer into multiple device chips. The protective component attachment step involves attaching a protective component to the front side of the wafer after the laser processing step has been performed. The processing strain removal step involves supplying a plasma gas to the back side of the wafer from directly above it in a direction opposite to the back side of the wafer, so that the plasma gas smoothly irradiates the back side of the wafer in a direction perpendicular to the back side of the wafer and enters the gap between adjacent device chips, thereby removing the processing strain formed on the back side of the multiple device chips and the exposed sides in the gap between adjacent device chips. as well as The heat-affected layer removal step involves providing a plasma-state gas to the back side of the wafer after the protective component bonding step, thereby removing the heat-affected layer formed around the laser processing tank.

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