PROCESSING METHOD FOR A WAFER

Abstract

Machining method for a wafer (10) for dividing the wafer (10) on which several component chips (12') are formed on a front surface (10a) in such a way that they are characterized by several planned division lines (14) that intersect each other, into individual component chips (12'), wherein the machining method comprises: a training step for a modified layer to position a focal point of a laser beam (LB) with a wavelength that can be transmitted with respect to the wafer (10) in an interior of the planned division line (14) and to perform an irradiation with the laser beam (LB) along the planned division line (14) to form modified layers (100) in the interior; a coating step for a water-soluble plastic (24) for coating the front surface (10a) of the wafer (10) with a water-soluble plastic (24) before or after the formation step for a modified layer; a support step for a frame for attaching a rear surface (10b) of the wafer (10) to a dividing belt (T) and supporting an outer circumference of the dividing belt (T) by a ring frame (F) having an opening part (Fa) that encloses the wafer (10), before or after the formation step for a modified layer; a division step to extend the division band (T) to divide the wafer (10) into individual component chips (12') together with the water-soluble plastic (24) with which the front surface (10a) of the wafer (10) is coated; a removal step for a modified layer (100) to perform plasma etching and removal of the modified layers (100) remaining on the side surfaces of the device chips (12') in a state in which the parting line (T) is extended and the front surfaces of the individual device chips (12') are coated with the water-soluble plastic (24); and a removal step for a water-soluble plastic (24) to remove the water-soluble plastic (24) with which the front surfaces of the component chips (12') are coated.

Description

BACKGROUND OF THE INVENTION Technical field

[0001] The present invention relates to a processing method for a wafer for dividing the wafer, on which several components are formed on a front surface, into individual component chips in such a way that they are characterized by several planned division lines that are crossed by each other. Description of the state of the art

[0002] A wafer on which several components such as integrated circuits (ICs), large scale integration circuits (LSIs) and light-emitting diodes (LEDs) are formed on a front surface in such a way that they are characterized by several planned division lines that intersect each other, is divided into individual component chips by a laser processing device and the component chips obtained by the division are used for electronic equipment such as mobile phones and personal computers.

[0003] The laser processing device includes a clamping table that holds a workpiece (wafer), a laser beam irradiation unit that irradiates the workpiece, which is held by the clamping table, with a laser beam having a wavelength that can be transmitted relative to the workpiece, an X-axis feed mechanism that performs a processing feed of the clamping table and moves the laser beam irradiation unit relative to each other in an X-axis direction, and a Y-axis feed mechanism that performs a processing feed of the clamping table and the laser beam irradiation unit relative to each other in a Y-axis direction orthogonal to the X-axis direction.The laser processing device positions the focal point of the laser beam within a planned parting line of the wafer and performs an irradiation to form modified layers that serve as starting points for division within the planned parting line (see, for example, Japanese patent application no. 2012-2604). A ribbon supporting the back surface of the wafer is then extended, and the wafer is divided into individual device chips using the modified layers formed within it, along the planned parting line as the starting points for division.

[0004] US 9 748 182 B2 relates to a wafer processing method comprising a stacked element removal step in which a laser beam with an absorption wavelength is applied through a protective film along each parting line formed on the front face of a wafer to a stacked element, thereby performing ablation to remove the stacked element present at each parting line; a parting step in which an external force is applied to the wafer to divide the wafer into individual device chips along each parting line where a modified layer has previously been formed; and a plasma etching step in which an etching gas in a plasma state is supplied to the wafer from the front face after the stacked element removal step or after the parting step has been performed, thereby removing damage due to ablation in the stacked element removal step.

[0005] JP 2018 - 195 663 A relates to a method for dividing a wafer, comprising covering an area of ​​the wafer with a protective film; positioning a focal point of a laser beam with a wavelength transparent to the wafer within the wafer and applying the laser beam to the wafer along each planned division line from the back side to create a quality-modified layer and a crack in the wafer that, after the protective film covering step, extends from the quality-modified layer towards the face and back side; adhering a stretchable tape to the back side of the wafer; stretching the stretchable tape to increase the spacing between the device chips; supplying a plasma etching gas to the wafer from the face side to remove the quality-modified layer remaining on a side face of each device chip; and removing the protective film from the wafer.

[0006] JP 2005 - 252 126 A relates to a wafer processing method for dividing a wafer in which functional elements are arranged in areas subdivided by grid-like planned division lines on a front face, comprising a step for forming a decomposed layer along the planned division lines inside the wafer by irradiating the wafer with a pulsed laser beam that is transparent along the planned division lines; a division step for dividing the wafer into chips along the planned division lines by applying an external force along the planned division lines formed by the decomposed layers; and a chip support step for arranging the divided chips on a support element while their back faces are rotated upwards at a distance from each other.and a step to remove disassembled areas to remove the disassembled layers that remain on the side faces of the chips. PRESENTATION OF THE INVENTION

[0007] In the case where the modified layers, which serve as the origin points for splitting, are formed along planned split lines and the wafer is divided into individual component chips as described above, there is a problem that when the wafer is split, dust from the parts that serve as the origin points of splitting is scattered and adheres to the front surface of the components, thus contaminating the components.

[0008] Furthermore, some of the modified layers remain on the outer surfaces (sidewalls) of the component chips. This leads to problems such as dust being scattered from the remaining modified layers, contaminating the component chips and the atmosphere in subsequent steps after the splitting step, and reducing the flexural strength of the component chips due to the remaining modified layers on the sidewalls.

[0009] Consequently, an objective of the present invention is to provide a processing method for a wafer in which the front surface of the component chips and the atmosphere are not contaminated and the flexural strength of the component chips is not reduced.

[0010] In accordance with one aspect of the present invention, a processing method for a wafer for dividing the wafer into individual component chips is provided, in which several component chips are formed on a front surface in such a way that it is marked by several planned division lines that intersect each other. The processing method comprises a formation step for a modified layer for positioning a focal point of a laser beam with a wavelength that can be transmitted with respect to the wafer within the interior of the planned division line and performing irradiation with the laser beam along the planned division line to form modified layers inside, and a coating step with a water-soluble plastic for coating the front surface of the wafer with a water-soluble plastic before or after the formation step for a modified layer.The processing method also includes a frame support step for attaching a rear surface of the wafer to a dividing belt and supporting an outer circumference of the dividing belt by a ring frame having an opening part that encloses the wafer, before or after the formation step for a modified layer, and a dividing step for expanding the dividing belt to divide the wafer into the individual component chips along with the water-soluble plastic with which the front surface of the wafer is coated.The processing procedure also includes a modified layer removal step to perform plasma etching and remove the modified layers remaining on the side surfaces of the component chips in a state where the parting line is extended and the front surfaces of the individual component chips are coated with the water-soluble plastic, and a water-soluble plastic removal step to remove the water-soluble plastic with which the front surfaces of the component chips are coated.

[0011] In a case where the frame support step is performed after the training step for a modified layer, laser beam irradiation can be performed from a rear surface of the wafer to form the modified layers along the planned division lines in the training step for a modified layer. Furthermore, in a case where the frame support step is performed before the training step for a modified layer, laser beam irradiation can be performed from one side of the division line through the division line to form the modified layers along the planned division lines in the training step for a modified layer.

[0012] Preferably, in the dividing step, the water-soluble plastic is heated and softened, in a case where the dividing tape is extended to divide the wafer into individual component chips after the water-soluble plastic has cured. Preferably, in the dividing step, the dividing tape is extended to divide the wafer into the individual component chips before the water-soluble plastic cures.

[0013] According to the processing method for a wafer in accordance with the present invention, even if dust scatters when the wafer is split, the front surface is shielded from the dust by the water-soluble plastic, thus solving the problem of device chip contamination. Furthermore, plasma etching is performed in the state where the front surfaces of the device chips are protected by the water-soluble plastic. Therefore, the modified layers remaining on the outer perimeters of the device chips are removed without damaging the chips, and dust does not scatter in subsequent steps. Consequently, the problem of device chips and the atmosphere becoming contaminated is solved. Additionally, the problem of reduced flexural strength of the device chips is also resolved.

[0014] The above and further aims, features and advantages of the present invention and the way in which they are realized will become more apparent, and the invention itself will best be understood by studying the following description and the attached claims with reference to the attached drawings, which show preferred embodiments of the invention. BRIEF DESCRIPTION OF THE FIGURES Fig. Figure 1 is a perspective view showing an embodiment of a coating step for a water-soluble plastic; Fig. Figure 2 is a perspective view showing one embodiment of a training step for a modified layer; Fig. Figure 3 is a perspective view showing one embodiment of a frame support step; Fig. Figure 4 is a perspective view showing a form of heating and softening a water-soluble plastic; Fig. Figure 5 is a perspective view showing one embodiment of a division step; Fig. Figure 6 is a perspective view showing one embodiment of a removal step for a modified layer; Fig. Figure 7 is a perspective view showing an embodiment of a removal step for a water-soluble plastic; Fig. Figure 8 is a side view, partially in cross-section, which represents an embodiment of a recording step; Fig. Figure 9 is a perspective view showing another embodiment of the coating step for a water-soluble plastic; and Fig. Figure 10 is a perspective view showing another embodiment of a training step for a modified layer. DETAILED DESCRIPTION OF PREFERRED EXECUTION FORMS

[0015] A processing method for a wafer according to an embodiment of the present invention is described in detail below with reference to the accompanying figures. Fig. Figure 1 shows a wafer 10, which is a workpiece to be processed by the wafer processing method according to the embodiment. The wafer 10 is a wafer containing silicon, sapphire, gallium arsenide, or the like as a substrate and has a circular disk shape. Several components 12 are formed on a front surface 10a such that they are characterized by several planned division lines 14 that intersect each other. The wafer 10, prepared in this way, becomes a coating device 20 for a water-soluble plastic (only partially shown), which is Fig. The material is conveyed and placed and held on a rotary table 18 with the side of a rear surface 10b facing downwards, as shown in Figure 1. The rotary table 18 includes a rotary drive unit, which is not shown in the drawing, and the rotary table 18 is rotated at high speed.

[0016] In the coating device 20 for a water-soluble plastic, a nozzle 22 is arranged which feeds a predetermined water-soluble plastic 24 downwards. The water-soluble plastic 24 fed by the nozzle 22 is a water-soluble plastic such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP).

[0017] The nozzle 22 described above is positioned above the center of the rotary table 18, i.e., the center of the front surface 10a of the wafer 10, and a predetermined quantity of the water-soluble plastic 24 is fed downwards. Additionally, the rotary table 18 is rotated in a direction represented by R1, for example, at 300 revolutions per minute. The water-soluble plastic 24 is distributed to the outer circumferential side of the front surface 10a of the wafer 10 by a centrifugal force generated by this rotation, and the entire front surface 10a of the wafer 10 is coated with the water-soluble plastic 24, as shown at the lower stage in Figure 1. Fig. Figure 1 shows the coating step (coating step for a water-soluble plastic). As described later, the coating step for a water-soluble plastic is not limited to being carried out at this point in time and can be carried out after the formation step for a modified layer, which will be described later, and it is sufficient that the coating step for a water-soluble plastic is carried out at one point in time of a division step.

[0018] Subsequently, the wafer 10 is processed into a laser processing device 30 (only partially shown), which is in Fig. The laser processing device 30, as shown in Figure 2, includes a holding unit comprising a clamping table 32 and a laser beam irradiation unit 34, which irradiates the wafer 10, held by the clamping table 32, with a laser beam LB. Furthermore, the upper surface of the clamping table 32 is made of a gas-permeable material and is connected to a suction source, not shown, through the interior of the clamping table 32.The laser processing device 30 includes an X-axis feed mechanism that performs a processing feed of the clamping table 32 and the laser beam irradiation unit 34 relative to each other in an X-axis direction, a Y-axis feed mechanism that performs an index feed of the clamping table 32 and the laser beam irradiation unit 34 relative to each other in a Y-axis direction orthogonal to the X-axis direction, and a rotary drive unit that rotates the clamping table 32 (a graphical representation is omitted for these elements).

[0019] The wafer 10, which has been conveyed to the laser processing device 30, is placed on the upper surface of the clamping table 32 and is suctioned and held with the side of the rear surface 10b facing upwards. The water-soluble plastic 24 solidifies over time, and no problem arises when the wafer 10 is held by the clamping table 32. An alignment step is performed on the wafer 10, which is held by the clamping table 32, using an infrared irradiation unit located in the laser processing device 30 and a setup unit that includes an infrared camera (a graphic representation of this is omitted). This detects the position of a planned division line 14, which is formed in a predetermined direction on the front surface 10a, and aligns the planned division line 14 with the X-axis direction.Information regarding the position of the detected planned division line 14 is stored in a control unit that is not shown in the illustration.

[0020] A beam condenser 36 of the laser beam irradiation unit 34 is positioned at the processing start position of the predetermined planned division line 14 based on the position information detected by the alignment step described above, and the focal point of the laser beam LB is positioned inside the planned division line 14, which extends in a first direction of the wafer 10, and irradiation is performed. Additionally, the processing feed of the clamping table 32 is performed in the X-axis direction, and a modified layer 100 is formed inside the planned division line 14 of the wafer 10.After the modified layer 100 has been formed along the interior of the predetermined planned division line 14, which extends in the first direction, an index feed of the clamping table 32 is performed in the Y-axis direction by the distance of the planned division lines 14, and the planned division line 14 that is adjacent in the Y-axis direction and has not yet been processed is positioned directly below the beam condenser 36. Then, similar to the processing described above, the focal point of the laser beam LB is positioned in the interior of the planned division line 14 of the wafer 10, and irradiation is performed. A processing feed of the clamping table 32 is then performed in the X-axis direction to form the modified layer 100 in the interior.

[0021] Similarly, the processing feed of the clamping table 32 is performed in the X-axis direction and the indexing feed of the clamping table 32 is performed in the Y-axis direction to form the modified layers 100 in all planned division lines 14 extending in the first direction. Subsequently, the clamping table 32 is rotated by 90 degrees and the planned division lines 14 in a second direction are aligned orthogonally to the planned division lines 14 extending in the first direction with the X-axis direction. Then, for the interior of each planned division line 14, the focal point of the laser beam LB is positioned in the interior and irradiation is performed similarly to the processing described above, so that the modified layers 100 are formed in all planned division lines 14 formed in the front surface 10a of the wafer 10 (formation step for a modified layer).

[0022] The processing conditions in the training step for a modified shift, as described above, are set as follows, for example. Wavelength: 1342 nm Repetition frequency: 90 kHz Average power consumption: 1.2 W Processing feed rate: 700 mm / s

[0023] After the training step for a modified layer has been carried out as described above, the wafer 10 is removed from the laser processing device 30. Then, the side of the front surface 10a, which is coated with the water-soluble plastic 24, is oriented upwards and the side of the rear surface 10b is oriented downwards and aligned at the center of a parting line T, which is in Fig. As shown in Figure 3, the outer circumference of the dividing strip T is supported by a ring frame F, which has an opening Fa of a size that allows the wafer 10 to be enclosed. Therefore, the wafer 10 is supported by the ring frame F through the dividing strip T (frame support step). The dividing strip T is a thin film, for example made of polyvinyl chloride (PVC), and has a surface with an adhesive layer. It is elastic and contractible.

[0024] After the wafer 10 is carried by the ring frame F as described above, a heater (not shown in the drawing) is positioned above the front surface 10a, which is coated with the water-soluble plastic 24, as required, and the water-soluble plastic 24 is coated by applying hot air H to it from the top, as shown in Fig. 4 shown, heated to break up the water-soluble plastic 24. Subsequently, in the state where the water-soluble plastic 24 is softened, the wafer 10 is conveyed to the expansion device, which is not shown in the illustration, and which expands the dividing belt T, and the dividing belt T is expanded in a radial manner (directions shown by arrows R2), as shown in Fig. 5 shown, extended. This creates division grooves 110 along the planned division lines 14 and divides the wafer 10 into individual component chips 12' together with the water-soluble plastic 24, with which the front surface 10a of the wafer 10 is coated (division step).

[0025] After the division step was carried out as described above, as in Fig. As shown in Figure 6, the wafer 10, supported by the ring frame F, is conveyed to a plasma device 40, of which a detailed drawing is omitted. Any well-known plasma device can be used as the plasma device 40. For example, the plasma device 40 includes an etching chamber forming a sealed space, an upper electrode and a lower electrode arranged within the etching chamber, a gas supply unit that expels an etching gas from the upper electrode to the lower electrode side of the etching chamber, etc. (a graphic representation of all these features is omitted). Here, between the upper and lower electrodes, the wafer 10, on which the division step has been performed, is placed with the side of the front surface 10a facing upwards.The etching gas is then fed into the etching chamber, and a high-frequency power, which generates a plasma, is applied to the upper electrode. This causes the etching gas, converted into a plasma, to be generated in the space between the upper and lower electrodes and attracted to the side of wafer 10.

[0026] Here, the wafer 10, which was conveyed to the plasma device 40 after the division step described above, is held in a state in which the side of the front surface 10a is protected by the water-soluble plastic 24 and the adjacent component chips 12' are divided by means of the division groove 110, i.e., in a state in which the sidewalls forming the outer circumferences of the component chips 12' are exposed. This exposed state is achieved, for example, by performing a heat-shrinking process, by applying heat to the outer circumferential region of the division band T that supports the wafer 10 and maintaining a tensile force S.For this reason, in the plasma etching device 40 described above, plasma etching is performed on the sidewalls of the component chips 12' in a state where the front surface of each component chip 12' is coated with the water-soluble plastic 24. As a result, the modified layers remaining on the outer perimeters of the component chips 12' are removed without etching the front surfaces of the component chips 12' (modified layer removal step).

[0027] Subsequently, wafer 10 is held on a rotary table (a graphic representation of which is omitted) of a cleaning unit (only partially shown), which is located in Fig. The rotary table is shown in Figure 7 and is positioned directly below a water discharge nozzle 52. Cleaning water W is then discharged onto the front surface 10a of the wafer 10 while the rotary table is rotated in a direction indicated by arrow R2, for example, at 500 rpm. The discharge of the cleaning water W dissolves and removes the film of water-soluble plastic 24 formed on the front surface 10a of the wafer 10 (water-soluble plastic removal step). After the water-soluble plastic 24 has been removed from the front surface 10a of the wafer 10, while the rotary table is rotated at, for example, 3000 rpm, air is discharged from a suitable air discharge nozzle (this is omitted from the drawing) to dry the front surface 10a of the wafer 10.

[0028] According to the embodiment described above, even if dust is scattered from the grooves 110 described above when the wafer 10 is split, the dust is blocked by the water-soluble plastic 24 with which the front surfaces of the component chips 12' are coated, thus preventing contamination. Furthermore, the modified layers remaining on the outer perimeters of the component chips 12' are removed by plasma etching, and therefore dust is not scattered in the subsequent steps. Consequently, the problem of contamination of the component chips and the atmosphere is solved. Additionally, the problem of reduced flexural strength of the component chips is also solved.

[0029] After the division step and the removal step for a modified layer have been performed as described above, a pick-up step is performed to pick up the component chips 12' from the division band T, as shown in Fig. 8 as required. The recording step can be carried out using a recording device 60, which is in Fig. Figure 8 shows, for example, how it can be carried out. The receiving device 60 includes a receiving clamp 62, which causes and promotes suction for the adhesion of the component chips 12', and an expansion unit 64, which expands the division band T to increase the distance between adjacent component chips 12'.

[0030] As in Fig. As shown in Figure 8, the expansion unit 64 comprises a circular cylindrical expansion drum 64a, several air cylinders 64b adjacent to the expansion drum 64a and extending upwards at intervals in a circumferential direction, an annular retaining element 64c connected to the upper end of each of the air cylinders 64b, and several clamps 64d arranged at intervals in the circumferential direction on the outer circumferential edge portion of the retaining element 64c. The inner diameter of the expansion drum 64a is larger than the diameter of the wafer 10, and the outer diameter of the expansion drum 64a is smaller than the inner diameter Fa of the ring frame F. Furthermore, the retaining element 64c corresponds to the ring frame F, and the ring frame F is enabled to be placed on the flat upper surface of the retaining element 64c.

[0031] As in Fig. As shown in Figure 8, the multiple air cylinders 64b raise or lower the retaining element 64c relative to the expansion drum 64a between a reference position (shown by solid lines), in which the upper surface of the retaining element 64c is at approximately the same height as the upper end of the expansion drum 64a, and an expansion position (shown by the double dotted-dashed lines), in which the upper surface of the retaining element 64c is at its lower side relative to the upper end of the expansion drum 64a.

[0032] The receiving clamp 62, which is in Fig. The device shown in Figure 8 is designed to be movable in the horizontal and upward-downward directions. Furthermore, a suction element (not shown in the drawing) is connected to the gripping tool 62, and the lower surface of the tip of the gripping tool 62 causes a suction effect on the component chip 12'.

[0033] The description is given with reference to Fig. 8 continued. In the loading step, the wafer 10, which is divided into individual component chips 12', is first oriented upwards, and the ring frame F is placed on the upper surface of the holding element 64c, which is located at the reference position. Subsequently, the ring frame F is fixed by the several clamps 64d. Following this, the holding element 64c is lowered to the expansion position, thereby exerting a tensile force on the dividing band T. Subsequently, the distance between the component chips 12' that adhere to the dividing band T is determined as shown by the double-dotted-dashed lines in Fig. 8 is shown, extended.

[0034] Subsequently, the picking tool 62 is positioned above the component chips 12' of the picking target and lowered, causing a suction effect on the upper surface of the component chips 12' against the lower surface of the tip of the picking tool 62. The picking tool 62 is then raised, separating the component chip 12' from the dividing strip T for picking (see the upper step on the right side in Figure 1). Fig. 8) Subsequently, the picked-up component chip 12' is conveyed to a tray or the like, not shown in the drawing, or is conveyed to a predetermined conveying position for the next step. Then the picking operation is performed sequentially for all component chips 12', so that the picking step is completed. If the removal step for a water-soluble plastic was previously performed as described above, the water-soluble plastic 24 was removed from the component chip 12' picked up in the picking step as shown in the upper stage of the right-hand side. Fig. 8 shown, removed. Consequently, the component chip 12' can be conveyed to a connection step as it is and a connection processing can be carried out.

[0035] In the embodiment described above, the removal step for a water-soluble plastic is performed before the uptake step. However, the present invention is not limited thereto. After the removal step for a modified layer has been performed by plasma etching, the uptake step can be performed without performing the removal step for a water-soluble plastic, so that the device chip 12' can be uptaken with the water-soluble plastic 24 remaining on its front surface (see the lower step of the right side in Figure 1). Fig. 8) In this case, in the next or subsequent step, the removal step for a water-soluble plastic is carried out to remove the water-soluble plastic 24 immediately before the component chips 12' are wired to a substrate or the like, for example. This allows the front surfaces of the component chips 12' to be kept clean until just before the next step during the period from the pickup step to the next step.

[0036] In the embodiment described above, the frame support step is performed after the formation step for a modified layer, and irradiation with the laser beam LB is performed directly from the rear surface of the wafer to form the modified layer 100 at the planned division line 14 in this formation step for a modified layer. However, the frame support step can be performed before the formation step for a modified layer. In this case, as in Fig. As shown in Figure 9, the side of the front surface 10a of the wafer 10 is oriented upwards, and the side of the rear surface 10b is oriented downwards and attached to the center of the dividing band T. Additionally, the outer circumference of the dividing band T is supported by the ring frame F, which has an opening Fa sized to enclose the wafer 10 (frame support step). Subsequently, the front surface 10a of the wafer 10 is positioned directly below the nozzle 22 of the coating device 20 for a water-soluble plastic. Then, the water-soluble plastic 24 is fed to the front surface 10a of the wafer 10, which is held by the ring frame F, and the ring frame F is rotated in a direction indicated by arrow R3. This allows the front surface 10a to be uniformly coated with the water-soluble plastic 24, as in the lower step of Figure 9. Fig. As shown in 9, it will be coated.

[0037] In the case where the support step for a frame was performed before the training step for a modified layer as described above, the wafer 10, as in Fig. The wafer 10, as shown in diagram 10, is conveyed to the laser processing device 30, and a clamping table (not shown in the diagram) is used to hold the wafer 10 in such a way that the rear surface 10b of the wafer 10 is supported by the ring frame F through the parting line T, i.e., the side of the parting line T is oriented upwards. Then, irradiation with the laser beam LB is performed from the side of the parting line T through the parting line T, so that the modified layers 100 are formed in all planned parting lines 14 in the front surface 10a of the wafer 10, similar to the processing based on Fig. 2 is described.

[0038] In all the embodiments described above, the coating step for a water-soluble plastic is performed before the formation step for a modified layer. However, as described above, it is sufficient for the coating step for a water-soluble plastic to be performed before the dividing step in which dust, etc., is dispersed. Therefore, the coating step for a water-soluble plastic can be performed after the formation step for a modified layer and immediately before the dividing step.In a case where, after the formation step for a modified layer has been carried out, the coating step for a water-soluble plastic has been carried out, and the division step has been carried out, it is advantageous for the coating step for a water-soluble plastic to be carried out immediately before the division step, and for the division step to be carried out before the curing of the water-soluble plastic 24 with which the front surface 10a of the wafer 10 is coated. This can preferably divide the wafer 10 into the individual component chips 12' without requiring heating and softening of the water-soluble plastic 24.

Claims

[1] A processing method for a wafer (10) for dividing the wafer (10) on which several component chips (12') are formed on a front surface (10a) in such a way that they are characterized by several planned division lines (14) which intersect each other, into individual component chips (12'), wherein the processing method comprises: a training step for a modified layer to position a focal point of a laser beam (LB) with a wavelength that can be transmitted with respect to the wafer (10) in an interior of the planned division line (14) and to perform an irradiation with the laser beam (LB) along the planned division line (14) to form modified layers (100) in the interior; a coating step for a water-soluble plastic (24) for coating the front surface (10a) of the wafer (10) with a water-soluble plastic (24) before or after the formation step for a modified layer; a support step for a frame for attaching a rear surface (10b) of the wafer (10) to a dividing belt (T) and supporting an outer circumference of the dividing belt (T) by a ring frame (F) having an opening part (Fa) that encloses the wafer (10), before or after the formation step for a modified layer; a division step to extend the division band (T) to divide the wafer (10) into individual component chips (12') together with the water-soluble plastic (24) with which the front surface (10a) of the wafer (10) is coated; a removal step for a modified layer (100) to perform plasma etching and removal of the modified layers (100) remaining on the side surfaces of the device chips (12') in a state in which the parting line (T) is extended and the front surfaces of the individual device chips (12') are coated with the water-soluble plastic (24); and a removal step for a water-soluble plastic (24) to remove the water-soluble plastic (24) with which the front surfaces of the component chips (12') are coated. [2] Processing method for a wafer (10) according to claim 1, wherein in a case in which the frame support step is carried out after the formation step for a modified layer, irradiation with the laser beam (LB) is carried out from a rear surface side (10b) of the wafer (10) to form modified layers (100) in the planned division lines (14) in the formation step for a modified layer. [3] Processing method for a wafer (10) according to claim 1 or 2, wherein in a case where the frame support step for a frame is carried out prior to the formation step for a modified layer, irradiation of the laser beam (LB) from one side of the parting line (T) through the parting line (T) is carried out to produce the modified layers (100) in the planned parting lines (14) in the formation step for a modified layer. [4] Processing method for a wafer (10) according to one of the preceding claims, wherein in the division step the water-soluble plastic (24) is heated and softened in a case in which the division band (T) is extended in order to divide the wafer (10) into individual component chips (12') after the water-soluble plastic (24) has cured. [5] Processing method for a wafer (10) according to one of claims 1 to 3, wherein in the dividing step the dividing band (T) is extended to divide the wafer (10) into individual component chips (12') before the water-soluble plastic (24) has cured.

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