METHOD FOR MACHINING A WORKPIECE

Abstract

Method for machining a workpiece (1) comprising a semiconductor substrate (11) having a front surface (11a) and a rear surface (11b) and a ductile material layer (17) containing a ductile material having a ductility and arranged on the front surface (11a) or the rear surface (11b) of the semiconductor substrate (11), wherein the method comprises: a tape application step involving the application of a tape (21) to one side (11a, 11b) of the semiconductor substrate (11) of the workpiece (1); a holding step involving holding the workpiece (1) by a holding table (28) over the belt (21), so that the ductile material layer (17) is exposed; and After performing the holding step, a cutting step is performed with a relative movement of the holding table (28) and a cutting blade (52) to each other in order to cause the cutting blade (52) to cut into the ductile material layer (17) and the semiconductor substrate (11), so that the workpiece (1) is cut, wherein In the cutting step, the cutting blade (52) is rotated such that a section (52a) of the cutting blade (52) cuts into the workpiece (1) from the ductile material layer (17) in the direction of the semiconductor substrate (11), wherein the section (52a) is arranged on a front side in a direction of movement (X2) of the cutting blade (52) relative to the holding table (28).

Description

BACKGROUND OF THE INVENTION AREA OF THE INVENTION

[0001] The present invention relates to a method for machining a workpiece comprising a substrate and a ductile material layer. DESCRIPTION OF THE RELATED STATE OF THE ART

[0002] In electronic equipment, including mobile phones and personal computers, component chips containing electronic circuits are arranged as essential parts. Such component chips are obtained by defining a wafer, made of a semiconductor material such as silicon (Si), into several regions along planned dividing lines (hereinafter referred to as "roads") from its front surface, forming components in the individual regions, and then separating the wafer along the roads.

[0003] In recent years, there has been an increasing number of instances where a film made of a metal, such as copper (Cu) (hereinafter referred to as the "metal film"), is applied to the back face of a wafer to perform a variety of functions necessary for electronic component chips. When separating such a workpiece containing a wafer and metal film, a tape is applied to one side of the metal film of the workpiece to hold the workpiece on the metal film side (over the tape) so that the wafer is exposed. Subsequent cutting of the workpiece with a cutting blade, rotated so that it cuts into the workpiece from one side of the wafer towards the side of the metal film, allows the workpiece to be cut and divided into multiple electronic component chips.

[0004] In the aforementioned process, the metal film formed from a ductile metal is stretched towards the strip by the rotating cutting blade, resulting in the formation of rough metal edges, known as "burrs." Such burrs can cause failures, such as short circuits between terminals, for example, when such a component chip is mounted on a printed circuit board. Therefore, it is essential to completely eliminate the formation of burrs when cutting a workpiece containing a metal film.

[0005] To solve this problem, a method has been proposed in which a metal film is cut by irradiation with a laser beam (see, for example, JP 2018-78162A). According to this method, the laser beam is emitted to cut the metal film after a workpiece has been cut from one side of a wafer under conditions where no cutting blade cuts into the metal film. Because no cutting blade is used to cut the metal film, the metal film remains free of burrs that would otherwise result from contact with a rotating cutting blade.

[0006] JP 2016-004831A proposes a method for cutting an enclosure substrate. The method comprises a tape-gluing step in which a separating tape is glued to the side of a metal frame body that comes into contact with the back of an enclosure substrate; a holding step in which the enclosure substrate is held over the separating tape by a holding surface of a clamping table; and a cutting step in which a cutting blade is positioned at the height at which the separating tape is to be cut, and a relative movement is effected between the clamping table and the cutting blade to cut and divide the enclosure with the cutting blade. In the cutting step, the cutting blade is configured to cut the enclosure substrate as it rotates from the back of the enclosure substrate to its surface.

[0007] Furthermore, US 2016 / 0260630 A1 describes a processing method for a single-crystal substrate with a film formed on its front or back side, in order to reliably laser-process the single-crystal substrate to a desired thickness, whereby the film is removed by a cutting blade. SUMMARY OF THE INVENTION

[0008] However, a process that cuts a metal film with a laser beam, as mentioned above, requires the combined use of a cutting device and a laser processing device. This leads to the problem that the equipment and steps tend to become more complex. Complex equipment and steps, in turn, increase the costs required to process the workpiece.

[0009] The present invention therefore has as an objective the provision of a method for processing a workpiece which has a substrate, such as a wafer, and a ductile material layer, such as a metal film, which can process the workpiece in simple steps and prevent the occurrence of burrs in the ductile material layer.

[0010] In accordance with one aspect of the present invention, a method for machining a workpiece is provided, comprising a semiconductor substrate having a front face and a rear face, and a ductile material layer containing a ductile material with ductility and arranged on the front face or the rear face of the semiconductor substrate. The method comprises a tape application step involving the application of a tape to one side of the semiconductor substrate of the workpiece; a holding step involving the holding of the workpiece by a holding table over the tape so that the ductile material layer is exposed; and, after the execution of the holding step, a cutting step involving the relative movement of the holding table and a cutting blade to cause the cutting blade to cut into the ductile material layer and the semiconductor substrate, thus cutting the workpiece.During the cutting step, the cutting blade is rotated so that a section of the cutting blade cuts into the workpiece from the ductile material layer in the direction of the semiconductor substrate, with the section being located on a front side in a direction of movement of the cutting blade relative to the holding table.

[0011] Preferably, the ductile material layer can be arranged on the rear surface of the semiconductor substrate, the workpiece can furthermore have several components arranged on one side of the front surface, and the ductile material layer can be formed from a metal film.

[0012] Preferably, the method may further include a position detection step after the execution of the holding step but before the execution of the cutting step, in which a position is detected based on an image obtained by imaging the front surface of the semiconductor substrate through the holding table and the belt, where the cutting blade is to be caused to cut into the workpiece.

[0013] Preferably, the semiconductor substrate can be made of silicon carbide (SiC).

[0014] In the machining process in accordance with the aspect of the present invention, the workpiece is held by the holding table above the belt so that the ductile material layer is exposed, and the cutting blade is then rotated such that a section of the cutting blade cuts into the workpiece from the ductile material layer in the direction of the semiconductor substrate, so that the workpiece is cut, wherein the section is arranged in the direction of movement of the cutting blade relative to the holding table on the side facing forward.

[0015] Even in a situation where the ductile material layer, containing the ductile material, is brought into close contact with the cutting blade and stretched, the cutting blade consequently comes into contact with the semiconductor substrate, which is made of a material harder than the ductile material. Therefore, the ductile material held in close contact with the cutting blade is removed from the cutting blade and remains essentially undeveloped. As a result, the formation of burrs on the ductile material layer can be suppressed.

[0016] Furthermore, in the processing method according to the present invention, unlike in the case where the ductile material layer is cut by a laser beam, it is not necessary to use a cutting device and a laser processing device in combination, and thus the workpiece can be processed in simple steps. According to the processing method of the present invention, the workpiece can be processed in simple steps, and the formation of burrs on the ductile layer can be prevented.

[0017] The above and other tasks, features and advantages of the present invention and the manner of its implementation will become clearer by studying the following description and attached claims, with reference to the accompanying drawings, which show a preferred embodiment of the invention, and the invention itself will be best understood by this. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective view depicting a workpiece; Fig. Figure 2 is a perspective view showing the workpiece with a strap attached to it; Fig. Figure 3 is a perspective view depicting a cutting device; Fig. Figure 4 is a perspective view showing a section of the cutting device; Fig. Figure 5 is a sectional view showing another section of the cutting device; Fig. Figure 6 is a perspective view showing another section of the cutting device; Fig. Figure 7 is a partial sectional view illustrating how the workpiece is shown from below; and Fig. Figure 8 is a partial section view illustrating how the workpiece is cut. DETAILED DESCRIPTION OF THE PREFERRED EXECUTION FORM

[0018] With reference to the attached drawings, a description of one embodiment of the present invention is given. Fig. Figure 1 is a perspective view depicting a workpiece 1 that is to be machined by a machining process in accordance with the embodiment. As in Fig. As shown in Figure 1, the workpiece 1 in this embodiment includes a substrate (wafer) 11 which is formed into a disk shape using a semiconductor material, such as SiC.

[0019] The substrate 11 is defined as several small areas by several mutually intersecting roads 13, and components (power components) 15, such as inverters or converters for use in controlling electrical power, are formed in the individual small areas. The resulting structure of the components 15 is designed to be distinguishable, for example, from one side of a front surface 11a of the substrate 11.

[0020] On one side of a rear surface 11b of the substrate 11, where the rear surface 11b is on the side opposite the front surface 11a, a ductile material layer 17, containing a ductile material such as a metal, is arranged. The ductile material layer 17 is a metal film, for example, made of a metal such as gold (Au), silver (Ag), copper, aluminum (Al), titanium (Ti), or nickel (Ni), and serves as a heat sink, a die-attach adhesive, or similar, with a thickness of approximately 0.1 to 30 µm.

[0021] The ductile material layer 17 is also formed in areas that overlap the roads 13 when viewed from one side of the front surface 11a or from one side of the rear surface 11b of the substrate 11. The ductile material layer 17 can be a single-layer metal film formed with an alloy containing, for example, a metal as mentioned above. Alternatively, the ductile material layer 17 can have a layered structure in which several metal films are superimposed on top of each other, each metal film formed with a single type of metal or metal alloy.

[0022] In this embodiment, the workpiece 1 includes the disk-shaped substrate 11, which is formed with SiC or a similar material, and no significant restrictions are imposed regarding the material, shape, structure, size, or similar characteristics of the substrate 11. Examples of the workpiece 1 may also include a substrate 11 formed with another semiconductor, such as Si, gallium arsenide (GaAs), or gallium phosphide (GaP), or a material such as a ceramic or resin. However, as described below, the substrate 11 must be formed with a material that is harder than the ductile material that forms part of the ductile material layer 17. Similarly, no restrictions are imposed regarding the type, number, shape, structure, size, arrangement, or similar characteristics of the components 15. Components 15 need not be formed on the substrate 11.

[0023] In the processing procedure in accordance with the embodiment, a band 21 (see Fig. 2), which is larger than the workpiece 1, attached to one side of the substrate 11 of the workpiece 1 (in other words, to the side of the front surface 11a of the substrate 11, that is, a side opposite the ductile material layer 17) (tape application step). Fig. Figure 2 is a perspective view showing workpiece 1 with the attached band 21.

[0024] Band 21 typically encloses a foil-shaped base material 21a (see Fig. 7, etc.) and an adhesive layer 21b, which is arranged on one side of the base material 21a, and allows visible light to pass through. The base material 21a of the strip 21 is, for example, made of a material such as polyolefin, polyvinyl chloride, or polyethylene terephthalate, while the adhesive layer 21b of the strip 21 is, for example, made of an acrylic-based or rubber-based material. When the strip 21 is brought into close contact with the side of the front surface 11a of the substrate 11 on one side of the adhesive layer 21b, the strip 21 is attached to, or adheres to, the workpiece 1.

[0025] For example, an annular frame 23, made of a metal such as stainless steel or aluminum, is attached to an outer circumferential section on the side of the adhesive layer 21b of the strip 21. The workpiece 1 is thus supported by the annular frame 23 via the strip 21. However, the workpiece 1 can also be machined without using the strip 21 and the frame 23.

[0026] As another alternative, it is also possible to use a strip 21 that does not have an adhesive layer 21b. In this case, the strip 21 is attached to the substrate 11 and the frame 23 by a process such as heat bonding, in which pressure is applied under heat. Furthermore, using the strip 21 that does not have an adhesive layer 21b simplifies the positional alignment (hereinafter referred to as "alignment") between a cutting blade 52 and the surfaces 13 of the workpiece 1, as described below. For the sake of simplifying alignment, it is desirable to use a strip 21 that has a planar base material 21a (for example, a base material 21a that has not undergone any embossing treatment).

[0027] After the belt 21 has been attached to the workpiece 1, the workpiece 1 is held on the side of the substrate 11 by the latter over the belt 21, so that the ductile material layer 17 is exposed (holding step). Fig. Figure 3 is a perspective view showing a cutting device 2 for use in the machining process in accordance with the embodiment. Fig. In section 3, a component of the cutting device 2 is indicated by a functional block, and some components of the cutting device 2 are omitted or simplified. In the following description, the X-axis direction (processing feed direction), the Y-axis direction (division feed direction or forward movement direction), and the Z-axis direction (height direction) are perpendicular to each other.

[0028] As in Fig. As shown in Figure 3, the cutting device includes a bed 4. An X / Y motion mechanism (machining feed mechanism and indexing feed mechanism) 8 is arranged on an upper surface of the bed 4. The X / Y motion mechanism 8 includes a pair of X-axis guide rails 10, which are attached to the upper surface of the bed 4 and are substantially parallel to the X-axis direction. An X-axis motion table 12 is slidably mounted on the X-axis guide rails 10.

[0029] Nut sections (not shown) are arranged on one side of a lower surface of the X-axis motion table 12. An X-axis ball screw 14, which is substantially parallel to the X-axis guide rails 10, is threaded into the nut sections. An X-axis stepper motor 16 is connected to one end of the X-axis ball screw 14. Rotation of the X-axis ball screw 14 by the X-axis stepper motor 16 causes the X-axis motion table 12 to move along the X-axis guide rails 10 in the X-axis direction. An X-axis scale 10a is arranged next to the X-axis guide rails 10 for use in detecting the position of the X-axis motion table 12 in the X-axis direction.

[0030] A pair of Y-axis guide rails 20 are arranged essentially parallel to the Y-axis direction on an upper surface of the X-axis motion table 12. A Y-axis motion table 22 is slidably mounted on the Y-axis guide rails 20. Fig. Figure 4 is a perspective view showing a section of the cutting device 2, wherein the section includes the Y-axis motion table 22, and Fig. Figure 5 is a partial sectional view showing another section of the cutting device 2, wherein the section includes the Y-axis motion table 22. Fig. In section 5, hatching of the sections is omitted for the sake of simplicity of description.

[0031] As in the Fig. 4 and Fig. As shown in Figure 5, the Y-axis motion table 22 encloses a lower or bottom wall section 22a, which has a rectangular shape when viewed from the Z-axis direction. A side wall section 22b is connected to one end of the lower wall section 22a in the Y-axis direction. The side wall section 22b also has a rectangular shape when viewed from the Y-axis direction. An upper wall section 22c is connected to one end of the second wall section 22b in the Y-axis direction. The upper wall section 22c has a rectangular shape that, when viewed from the Z-axis direction, resembles that of the lower wall section 22a.Between the lower wall section 22a and the upper wall section 22c, a space 22b is thus formed, which extends to an outside at the other ends of the lower and upper wall sections 22a, 22c in the Y-axis direction and also at opposite ends of the lower and upper wall sections 22a, 22c in the X-axis direction.

[0032] On one side of a lower surface of the lower wall section 22a of the Y-axis motion table 22 are mother sections 22e (see Fig. 5) arranged, and a Y-axis ball screw 24, which is substantially parallel to the Y-axis guide rails 20, is threaded into the nut sections 22e. A Y-axis stepper motor 26 is connected to one end of the Y-axis ball screw 24.

[0033] Rotation of the Y-axis ball screw 24 by the Y-axis stepper motor 26 causes the Y-axis motion table 22 to move along the Y-axis guide rails 20 in the Y-axis direction. Next to the Y-axis guide rails 20 is a Y-axis scale 20a (see Fig. 3) arranged for use in detecting the position of the Y-axis motion table 22 in the Y-axis direction.

[0034] On one side of an upper surface of the upper wall section 22c of the Y-axis motion table 22, a holding table (clamping table) 28 is arranged for use in holding the workpiece 1. The holding table 28 is supported on the upper wall section 22c in such a way that the holding table 28 can rotate about an axis of rotation that is substantially parallel to the Z-axis direction.

[0035] The holding table 28 encloses a cylindrical frame element 30, which is made, for example, of a metal such as stainless steel. A disc-shaped retaining element 32 is arranged on an upper section of the frame element 30 to close an opening on one side of the upper section of the frame element 30. The retaining element 32 has a substantially planar upper surface 32a and a lower surface 32b (see Fig. 7, etc.) on one of the sides opposite the upper surface 32a and is made of a transparent material, such as soda glass, borosilicate glass or quartz glass, which allows visible light to pass through it.

[0036] As in Fig. As shown in Figure 4, several grooves 32c are formed in the upper surface 32a of the holding element 32 for use in suctioning the workpiece 1. A suction source (not shown), which includes a vacuum ejector or similar device, is connected to the grooves 32c, so that a negative pressure generated at the suction source can act on the grooves 32c.

[0037] The retaining element 32 is configured such that visible light is allowed to pass through the retaining element 32 into at least its area, in a region other than that of the grooves 32c or similar features, and that the workpiece 1 and similar items, which are arranged on one side of the upper surface 32a of the retaining element 32, can be imaged from one side of the lower surface 32b of the retaining element 32. In this embodiment, the retaining element 32 is described as being formed entirely with the transparent material. However, it is necessary for the retaining element 32 to allow visible light to pass through at least a portion of it. In other words, it is not necessary to form the retaining element 32 solely with the transparent material.

[0038] A rotary drive source 34, such as an electric motor, is arranged on the side wall section 22b of the Y-axis motion table 22. A belt 36 is wound around a roller section 30a, which is arranged on an outer circumference of the frame element 30, and a roller 34a, which is connected to a shaft of the rotary drive source 34, to transmit power from the rotary drive source 34. The holding table 28 is therefore rotated about the axis of rotation, which is essentially parallel to the Z-axis direction, by the power transmitted from the rotary drive source via the belt 36.

[0039] On an outer circumferential section of the frame element 30, several clamps 30b are arranged in addition to the roller section 30a for use in attaching the ring-shaped frame 23. The clamps 30b are attached to the frame element 30 in such a way that they do not interfere with the rotation of the holding table 28. The holding table 28 is also moved in the X-axis and Y-axis directions by the aforementioned X / Y motion mechanism 8, together with the X-axis motion table 12 and the Y-axis motion table 22.

[0040] As in Fig. As shown in Figure 3, a column-shaped or wall-shaped support structure 38 is arranged on the upper surface of the bed 4 in an area where the support structure 38 does not overlap the X / Y motion mechanism 8. A Z-axis motion mechanism 40 is arranged on a side wall of the support structure 38. The Z-axis motion mechanism 40 includes a pair of Z-axis guide rails 42, which are attached to the side wall of the support structure 38 and are essentially parallel to the Z-axis direction.

[0041] A spindle housing 46, which includes a cutting unit (machining unit) 44, is slidably mounted on the Z-axis guide rails 42. Nut sections (not shown) are arranged on a side wall of the spindle housing 46, the side wall being on one side of the support structure 38, and a Z-axis ball screw 48 engages with the nut sections in threaded engagement. The Z-axis ball screw 48 is substantially parallel to the Z-axis guide rails 42.

[0042] A Z-axis stepper motor 50 is connected to one end section of the Z-axis ball screw 48. Rotation of the Z-axis ball screw 48 by the Z-axis stepper motor 50 causes the spindle housing 46 to move along the Z-axis guide rails 42 in the Z-axis direction. A Z-axis scale (not shown) is located next to the Z-axis guide rails 42 for use in detecting the position of the spindle housing 46 in the Z-axis direction.

[0043] The cutting unit 44 includes a spindle (not shown) as a shaft, which is parallel to the Y-axis. The spindle is supported in such a way that it can be rotated by the spindle housing 46 mentioned above. A distal end section of the spindle is exposed by the spindle housing 46. The cutting blade 52, with abrasive grains, such as diamond, which are attached to it by a bonding agent, such as a metal, fits onto the distal end section of the spindle. A rotational drive source (not shown), such as an electric motor, is connected to one side of a proximal end of the spindle.

[0044] An upper imaging unit 54 is attached to the spindle housing 46 of the cutting unit 44 to image the workpiece 1 and similar objects from above, which is held by the holding table 28. The upper imaging unit 54 is therefore moved in the Z-axis direction together with the cutting unit 44 by the Z-axis motion mechanism 40.

[0045] In an area on the upper surface of the bed 4, wherein the area is located away from the X / Y motion mechanism 8 in the Y-axis direction, a column-shaped or plate-shaped imaging unit support structure 56 is arranged. Fig. Figure 6 is a perspective view showing a further section of the cutting device 2, wherein the further section includes the imaging unit support structure 56. An imaging unit movement mechanism 58 is arranged on a side wall of the imaging unit support structure 56.

[0046] The imaging unit motion mechanism 58 has a pair of Z-axis guide rails 60, which are attached to the side wall of the imaging unit support structure 56 and are substantially parallel to the Z-axis direction. A Z-axis motion plate 62 is slidably mounted on the Z-axis guide rails 60. Nut sections (not shown) are arranged on the side wall of the Z-axis motion plate 62, the side wall being on one side of the imaging unit support structure 56, and a Z-axis ball screw 64 is threaded into the nut sections. The Z-axis ball screw 64 is substantially parallel to the Z-axis guide rails 60.

[0047] A Z-axis stepper motor 66 is connected to an end section of the Z-axis ball screw 64. Rotation of the Z-axis ball screw 64 by the Z-axis stepper motor 66 causes the Z-axis motion plate 62 to move along the Z-axis guide rails 60 in the Z-axis direction. A Z-axis scale (not shown) is located next to the Z-axis guide rails 60 for use in detecting the position of the Z-axis motion plate 62 in the Z-axis direction.

[0048] A lower imaging unit 70 is attached to the Z-axis motion plate 62 via a support arm 68, which is elongated in the Y-axis direction. The lower imaging unit 70 has a lighting device 72, which is configured to emit visible light onto an upper object (in this embodiment, the workpiece 1), and a camera 74, which has an imaging element to receive light reflected from the object and form an image.

[0049] Components such as the X / Y motion mechanism 8, the rotary drive source 34, the Z-axis motion mechanism 40, the cutting unit 44, the upper imaging unit 54, the imaging unit motion mechanism 58, and the lower imaging unit 70 are connected to a control unit 76. The control unit 76 is, for example, a computer comprising a processing device, such as a central processing unit (CPU), and a storage device, such as flash memory, and controls the operations of the individual components so that the workpiece 1 is adequately machined. Functions of the control unit 76 are implemented by actuating the processing device in accordance with software stored in the storage device.

[0050] When holding the workpiece 1 on the side of the substrate 11, the band 21, which is attached to the side of the substrate 11 of the workpiece 1, is the first to be held, as shown in Fig. As shown in Figure 5, the upper surface 32a of the holding element 32 is brought into contact with the holding table 28. This allows a negative pressure generated at the suction source to act on the grooves 32c. Furthermore, the frame 23 is secured by the clamps 30b. Consequently, the workpiece 1 is held on the holding table 28 with the side of the ductile material layer 17 facing upwards.

[0051] After the workpiece 1 has been held on the side of its substrate 11 by the holding table 28, a desired path 13 (in other words, a position where the cutting blade 52 is made to cut into the workpiece 1) is detected based on an image obtained by imaging the workpiece 1 from below (position detection step). Fig. Figure 7 is a partial sectional view illustrating how workpiece 1 is shown from below.

[0052] In particular, it is described how the operation of the X / Y motion mechanism 8 and the imaging unit motion mechanism 58 are controlled by the control unit 76 such that the lower imaging unit 70, as in Fig. Figure 7 illustrates how the lower imaging unit 70 is positioned under the area of ​​the retaining element 32, through which visible light is transmitted. In particular, the lower imaging unit 70 is inserted into the space 22b between the lower wall section 22a and the upper wall section 22c of the Y-axis motion table 22.

[0053] A positional relationship between the holding element 32 and the lower imaging unit 70 is set as desired in an area suitable for imaging the workpiece 1.

[0054] As mentioned above, the section of the holding element 32 and the band 21 allow visible light to pass through them. Therefore, the front surface 11a of the substrate 11 can be imaged to form an image when visible light from the illumination device 72 of the lower imaging unit 70 is emitted towards the workpiece 1 via the illumination device 72, and light reflected by the lower surface of the workpiece 1 (the front surface 11a of the substrate) is received by the imaging element of the camera 74. As described above, in this embodiment, the front surface 11a of the substrate 11 is imaged by the holding element 32 (holding table 28) and the band 21.

[0055] The image captured by camera 74 is sent, for example, to control unit 76. Control unit 76 applies pattern recognition to the image sent by camera 74, extracting characteristic patterns or similar features of the components 15, and determines the position of the desired path 13 where the cutting blade 52 is to be directed to cut into the workpiece 1. The determined position of the desired path 13 is stored in the memory device of control unit 76.

[0056] After the position of the desired road 13 has been detected, the rotating cutting blade 52 is made to cut into the workpiece 1 in order to cut the workpiece 1 (cutting step). Fig. Figure 8 is a partial sectional view illustrating how the workpiece 1 is cut. Specifically, it describes how the rotary drive source 34 is actuated, for example by the control unit 76, so that the desired machining path 13 is aligned essentially parallel to the X-axis direction. Furthermore, the operation of the X / Y movement mechanism 8 is controlled by the control unit 76 such that the position of the cutting blade 52 is aligned over an extension of the desired machining path 13.

[0057] Then, the operation of the Z-axis movement mechanism 40 is controlled by the control unit 76 to adjust the position of the cutting unit 44 in the Z-axis direction so that the height of the lower end of the cutting blade 52 is lower than the height of the lower surface of the workpiece 1 (the front surface 11a of the substrate 11). Subsequently, the holding table 28 is moved as shown in Fig.Figure 8 illustrates how the X / Y motion mechanism 8 moves the cutting blade 52 during rotation in the X-axis direction (a first direction X1). In other words, the holding table 28 and the cutting blade 52 are moved relative to each other in the X-axis direction.

[0058] Representing here a direction in which the cutting blade 52 moves relative to the holding table 28 as a second direction X2 (a direction opposite to the first direction X1), a direction R1 in which the cutting blade 52 is rotated is set such that a section 52a of the cutting blade 52, with the section 52a being located on a front side in the second direction X2, cuts into the workpiece 1 from the ductile material layer 17 in the direction of the substrate 11. In other words, the cutting blade 52 is rotated so that the section 52a of the cutting blade 52 moves from top to bottom.

[0059] Even in a situation where the ductile material layer 17, with the ductile material contained therein, is brought into close contact with the cutting blade 52 and would thus be stretched by the cutting blade 52, the rotation of the cutting blade 52 in the direction R1, as described above, brings the cutting blade 52 into contact with the substrate 11, which is formed with the material that is harder than the ductile material. This causes the ductile material, which is held in close contact with the cutting blade 52, to be moved away from the cutting blade 52 and remain essentially unstretched. Therefore, the formation of burrs by the ductile material layer 17 can be prevented.

[0060] Through the processes described above, the cutting blade 52 is caused to cut along the desired path 13 into the workpiece 1 (the ductile material layer 17 and the substrate 11). As a result, the workpiece 1 is cut along the desired path 13. These processes are repeated until the workpiece 1 has been cut along all paths 13 established on the workpiece 1.

[0061] It has already been confirmed that if the conditions described below are met, the formation of burrs in the ductile material layer 17 can be largely prevented. The use of such a thin cutting blade 52, which meets these conditions, also significantly contributes to preventing the formation of burrs by reducing the volume of the ductile material layer 17 that needs to be removed by cutting. Substrate material: SiC Substrate thickness: 50 µm or more, but 360 µm or less Material of the ductile material layer: Au, Ag, Cu, Al, Ti or Ni Thickness of the ductile material layer: 0.1 µm or more, but 30 µm or less Road spacing: 0.5 mm or more, but 5 mm or less Cutting blade type: electroplated blade Cutting blade thickness: 15 µm or more, but 40 µm or less Grain size (grit) of the abrasive grains contained in the cutting blade: #1200 or more, but #2000 or less Cutting blade rotation speed (circumferential speed of the cutting blade: 15000 rpm or more, but 30000 rpm or less (2600 m / min or more, but 5300 m / min or less) Feed rate of the holding table: 20 mm / s or more, but 100 m / s or less if a ductile material layer is formed on the C-surface of the SiC; 1 mm / s or more, but 10 mm / s or less if a ductile material layer is formed on the Si-surface of the SiC.

[0062] After the workpiece 1 has been held by the holding table 28 via the belt 21 as described above during the machining process in accordance with the embodiment, so that the ductile material layer 17 is exposed, the cutting blade 52 is rotated such that the section 52a of the cutting blade 52 cuts into the workpiece 1 from the ductile material layer 17 in the direction of the substrate 11, with the section 52a being located on the front side in the direction of movement (the second direction X2) of the cutting blade 52 relative to the holding table 28. As a result, the workpiece 1 is cut.

[0063] Even in a situation where the ductile material layer 17, containing the ductile material, is brought into close contact with the cutting blade 52 and would thus be stretched by the cutting blade 52, the cutting blade 52 comes into contact with the substrate 11, which is formed with a material harder than the ductile material. Therefore, the ductile material held in close contact with the cutting blade 52 is removed from the cutting blade 52 and remains essentially undeveloped. As a consequence, the formation of burrs on the ductile material layer 17 is prevented.

[0064] Furthermore, in the machining process according to the embodiment, it is not necessary to use a cutting device and a laser processing device in combination, unlike in the case where the ductile material layer 17 is cut by a laser beam, and thus the workpiece 1 can be machined in simple steps. According to the machining process of the embodiment, the workpiece 1 can be machined in these simple steps, and the formation of burrs on the ductile material layer 17 is prevented.

[0065] It should be noted that the present invention can be implemented with various modifications without being limited to or by the description of the embodiment mentioned above. For example, it has been confirmed that when machining a workpiece having a silicon-based substrate, the following conditions make it possible to largely prevent the formation of burrs in a ductile material layer. The use of such a thin cutting blade, which meets these conditions, also significantly contributes to preventing the formation of burrs by reducing the volume of the ductile material layer that needs to be removed by cutting. Substrate material: Si Substrate thickness: 10 µm or more, but 300 µm or less Material of the ductile material layer: Ao, Ag, Cu, Al, Ti or Ni Thickness of the ductile material layer: 0.1 µm or less, but 30 µm or more Road spacing: 0.1 mm or more, but 5 mm or less Cutting blade type: electroplated blade Cutting blade thickness: 5 µm or more, but 40 µm or less Grain size (grid) of the cutting grains contained in the cutting blade: #1500 more, but #3500 or less Cutting blade rotation speed (circumferential speed of the cutting blade): 15000 rpm, but 60000 rpm or less (2600 m / min or more, but 10500 m / min or less) Feed rate of the holding table: 30 mm / s or more, but 200 mm / s or less

[0066] In the embodiment mentioned above, the description is given by way of example, in which the workpiece 1 is cut by the cutting blade 52. However, the machining method in accordance with the present invention can also be applied when a workpiece is partially cut by a cutting blade. In this case, it is only necessary to adjust the position of the cutting unit in the Z-axis direction so that the height of the lower end of the cutting blade is higher than the lower surface of the workpiece (the front surface of the substrate) and lower than the height of the interface between the substrate and the ductile material layer (the rear surface of the substrate).

[0067] In the embodiment mentioned above, a description is also given of an example in which the workpiece 1, including the metal film, is processed as the ductile material layer 17. However, it is not necessary for the ductile material layer belonging to the workpiece to be a metal film, as long as it contains a ductile material that has a higher ductility than that of the substrate material. For example, the ductile material layer can be a resin film or the like, formed using a resin. Furthermore, the ductile material layer can be arranged on the side of the front surface of the substrate.

Claims

[1] Method for machining a workpiece (1) comprising a semiconductor substrate (11) having a front surface (11a) and a rear surface (11b) and a ductile material layer (17) containing a ductile material having a ductility and arranged on the front surface (11a) or the rear surface (11b) of the semiconductor substrate (11), the method comprising: a tape application step involving the application of a tape (21) to one side (11a, 11b) of the semiconductor substrate (11) of the workpiece (1); a holding step involving holding the workpiece (1) by a holding table (28) over the belt (21), so that the ductile material layer (17) is exposed; and After performing the holding step, a cutting step is performed with a relative movement of the holding table (28) and a cutting blade (52) to each other in order to cause the cutting blade (52) to cut into the ductile material layer (17) and the semiconductor substrate (11), so that the workpiece (1) is cut, wherein In the cutting step, the cutting blade (52) is rotated such that a section (52a) of the cutting blade (52) cuts into the workpiece (1) from the ductile material layer (17) in the direction of the semiconductor substrate (11), wherein the section (52a) is arranged on a front side in a direction of movement (X2) of the cutting blade (52) relative to the holding table (28). [2] Method according to claim 1, wherein the semiconductor substrate (11) is formed from silicon carbide. [3] Method according to claim 1, wherein the ductile material layer (17) is arranged on the rear surface (11b) of the semiconductor substrate (11), the workpiece (1) further comprises several components (15) arranged on one side of the front surface (11a), and the ductile material layer (17) is formed from a metal film. [4] Method according to claim 3, wherein the semiconductor substrate (11) is formed from silicon carbide. [5] The method of claim 1 or 3, further comprising: After performing the holding step, but before performing the cutting step, a position detection step is performed in which a position where the cutting blade (52) is to be made to cut into the workpiece (1) is detected based on an image taken by imaging the front surface (11a) of the semiconductor substrate (11) through the holding table (28) and the belt (21). [6] Method according to claim 5, wherein the semiconductor substrate (11) is formed from silicon carbide.

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