Wafer Generation Equipment

Abstract

To provide a wafer generation apparatus capable of efficiently forming a modified layer on the inside of an ingot.SOLUTION: A wafer generation apparatus includes: holding means for holding an ingot; wafer generation means 6 for irradiating an ingot with a laser beam LB while positioning a condensation point of the laser beam LB having transparency to the ingot on the inside of the ingot and forming a modified layer in depth corresponding to the thickness of a wafer to be generated; and moving means for relatively moving the holding means and the wafer generation means 6. The wafer generation means 6 includes: an oscillator 18 for oscillating the laser beam LB; a condensing lens 20 for condensing the laser beam LB oscillated from the oscillator 18 into the inside of the ingot; and rotation means 22 for rotating the condensing lens 20 in parallel with an end face of the ingot.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a wafer preparation apparatus for preparing wafers. [Background technology]

[0002] Devices such as ICs, LSIs, and LEDs are formed by laminating functional layers on the surface of wafers made of materials such as Si (silicon) and Al2O3 (sapphire), and then dividing the wafer along planned dividing lines. Power devices, LEDs, and the like are formed by laminating functional layers on the surface of wafers made of hexagonal single crystal materials such as SiC (silicon carbide) and GaN (gallium nitride), and then dividing the wafer along planned dividing lines.

[0003] The wafer on which the devices are formed is processed along the intended dividing lines using a cutting machine or laser processing machine to separate it into individual device chips, and each of the separated device chips is used in electrical equipment such as mobile phones and personal computers.

[0004] Wafers on which devices are formed are generally produced by thinly slicing a cylindrical ingot with a wire saw, and the front and back surfaces of the produced wafers are polished to a mirror finish (see, for example, Patent Document 1).

[0005] However, when an ingot is cut with a wire saw and the front and back surfaces of the cut wafers are polished, most of the ingot (70-80%) is discarded, which is uneconomical. In particular, single crystal ingots such as SiC and GaN are hard and difficult to cut with a wire saw, which takes a considerable amount of time, resulting in poor productivity. In addition, the cost of the ingot is high, making it difficult to efficiently produce wafers.

[0006] Therefore, a technology has been proposed in which the focal point of a laser beam having a wavelength that is transparent to SiC or the like is positioned inside the ingot, the laser beam is irradiated onto the ingot, a modified layer is formed on the intended cutting surface, and a wafer is peeled off from the ingot along the intended cutting surface on which the modified layer has been formed (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-94221 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-49161 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the modified layers must be formed densely with an interval of about 10 μm between them, which takes time to form the modified layers and results in poor productivity.

[0009] An object of the present invention is to provide a wafer producing apparatus that can efficiently form a modified layer inside an ingot. [Means for solving the problem]

[0010] According to the present invention, the following wafer preparation apparatus is provided to solve the above problems: "A wafer production device for producing wafers, The wafer generating apparatus comprises at least a holding means for holding an ingot, a wafer generating means for positioning a focal point of a laser beam that is transparent to the ingot inside the ingot and irradiating the ingot with the laser beam to form a modified layer to a depth corresponding to the thickness of the wafer to be generated, and a moving means for moving the holding means and the wafer generating means relatively, The wafer generating means includes an oscillator that emits a laser beam, a focusing lens that focuses the laser beam emitted by the oscillator inside the ingot, and A rotating body on which the condenser lens is provided, and by rotating the rotating body and a rotating means for rotating the condenser lens parallel to the end face of the ingot. fruit, The condenser lens is disposed radially outward from the rotation axis of the rotating body. A wafer preparation apparatus is provided.

[0011] Preferably, a plurality of the condenser lenses are arranged in the rotational direction. The modified layer is preferably arc-shaped. [Effects of the Invention]

[0012] The wafer generating apparatus of the present invention comprises: The wafer generating apparatus comprises at least a holding means for holding an ingot, a wafer generating means for positioning a focal point of a laser beam that is transparent to the ingot inside the ingot and irradiating the ingot with the laser beam to form a modified layer to a depth corresponding to the thickness of the wafer to be generated, and a moving means for moving the holding means and the wafer generating means relatively, The wafer generating means includes an oscillator that emits a laser beam, a focusing lens that focuses the laser beam emitted by the oscillator inside the ingot, and A rotating body on which the condenser lens is provided, and by rotating the rotating body and a rotating means for rotating the condenser lens parallel to the end face of the ingot. fruit, The condenser lens is disposed radially outward from the rotation axis of the rotating body. Therefore, a modified layer can be efficiently formed inside the ingot. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view of a wafer preparation apparatus constructed in accordance with the present invention; [Figure 2] FIG. 2(a) is a schematic diagram of the wafer generating means shown in FIG. 1, and FIG. 2(b) is a bottom view of the rotating body shown in FIG. [Figure 3] (a) Perspective view of the ingot, (b) Plan view of the ingot shown in (a), (c) Front view of the ingot shown in (a). [Figure 4]FIG. 10( a ) is a perspective view showing the modified layer forming step, and FIG. 10( b ) is a side view showing the modified layer forming step. [Figure 5] Schematic diagram showing a peeling step. [Figure 6] FIG. 10(a) is a schematic diagram showing a first modified example of the wafer generating means, and FIG. 10(b) is a bottom view of the rotating body shown in FIG. [Figure 7] FIG. 10(a) is a schematic diagram showing a second modified example of the wafer generating means, and FIG. 10(b) is a bottom view of the rotating body shown in FIG. [Figure 8] FIG. 10(a) is a schematic diagram showing a third modified example of the wafer generating means, and FIG. 10(b) is a bottom view of the rotating body shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a wafer generating apparatus constructed according to the present invention will now be described with reference to the drawings.

[0015] (Wafer Generation Equipment 2) As shown in Figure 1, the wafer generation device 2 includes at least a holding means 4 for holding an ingot, a wafer generation means 6 for positioning the focal point of a laser beam that is transparent to the ingot inside the ingot and irradiating the ingot with the laser beam to form a modified layer to a depth corresponding to the thickness of the wafer to be generated, and a moving means 8 for moving the holding means 4 and the wafer generation means 6 relative to each other.

[0016] (Holding means 4) The holding means 4 includes an X-axis movable plate 12 supported on a base 10 so as to be freely movable in the X-axis direction, a Y-axis movable plate 14 supported on the X-axis movable plate 12 so as to be freely movable in the Y-axis direction, a holding table 16 rotatably supported on the upper surface of the Y-axis movable plate 14, and a motor (not shown) that rotates the holding table 16.

[0017] The X-axis direction is the direction indicated by the arrow X in Fig. 1, and the Y-axis direction is the direction indicated by the arrow Y in Fig. 1, which is a direction perpendicular to the X-axis direction. The XY plane defined by the X-axis and Y-axis directions is substantially horizontal.

[0018] In the holding means 4, the ingot is held on the upper surface of the holding table 16 via an appropriate adhesive (for example, an epoxy resin adhesive). Alternatively, a plurality of suction holes may be formed on the upper surface of the holding table 16, so that a suction force is generated on the upper surface of the holding table 16 to hold the ingot by suction.

[0019] (Wafer generation means 6) As shown in FIG. 2, the wafer generation means 6 includes an oscillator 18 that emits a laser beam LB, a focusing lens 20 that focuses the laser beam LB emitted by the oscillator 18 inside the ingot, and a rotation means 22 that rotates the focusing lens 20 parallel to the end face of the ingot.

[0020] (Oscillator 18) 1, the wafer generation means 6 has a housing 24 that extends upward from the upper surface of the base 10 and then extends substantially horizontally, and the oscillator 18 is housed in the housing 24. The oscillator 18 is configured to oscillate a pulsed laser beam LB having a wavelength that is transparent to the ingot that is the workpiece (for example, 1064 nm in the case of a SiC ingot).

[0021] (condenser lens 20) 1 and 2, the wafer generation means 6 further includes a hollow rotor 26 disposed on the lower surface of the leading end of the housing 24. The rotor 26 includes an upper cylindrical portion 28 rotatably supported on the lower surface of the leading end of the housing 24, and a lower cylindrical portion 30 extending radially outward from the lower end of the upper cylindrical portion 28. The condenser lens 20 is provided on the peripheral portion of the lower surface of the lower cylindrical portion 30 of the rotor 26, as shown in FIG.

[0022] Between the oscillator 18 and the condenser lens 20, there are arranged a mirror 32 that reflects the laser beam LB emitted by the oscillator 18, a collimating lens 34 that converts the laser beam LB reflected by the mirror 32 into a parallel beam, and an optical fiber 36 that guides the laser beam LB that has passed through the collimating lens 34 to the condenser lens 20. The mirror 32 is provided inside the housing 24, and the collimating lens 34 and the optical fiber 36 are attached to the rotor 26.

[0023] (Rotation means 22) 2, the rotating means 22 has a motor 38 and a gear 40 fixed to the output shaft of the motor 38. A gear (not shown) that meshes with the gear 40 of the rotating means 22 is formed on the outer peripheral surface of the upper cylindrical portion 28 of the rotating body 26. The rotating means 22 rotates the rotating body 26 using the motor 38, thereby rotating the condenser lens 20 parallel to the end face of the ingot. Note that the mechanism for transmitting the rotational motion of the motor 38 to the rotating body 26 may be any other known mechanism.

[0024] 1, an imaging means 42 is attached to the lower surface at the tip of the housing 24 to detect the area to be laser processed by the wafer generation means 6. The image captured by the imaging means 42 is displayed on a display means 44 arranged on the upper surface at the tip of the housing 24.

[0025] (Transportation 8) Continuing the explanation with reference to FIG. 1, the moving means 8 includes an X-axis feed means 46 that moves the holding means 4 in the X-axis direction relative to the wafer generating means 6, and a Y-axis feed means 48 that moves the holding means 4 in the Y-axis direction relative to the wafer generating means 6.

[0026] (X-axis feed means 46) X-axis feed means 46 has a ball screw 50 connected to X-axis movable plate 12 and extending in the X-axis direction, and a motor 52 that rotates ball screw 50. X-axis feed means 46 converts the rotational motion of motor 52 into linear motion using ball screw 50 and transmits it to X-axis movable plate 12, moving X-axis movable plate 12 in the X-axis direction along guide rails 10a on base 10.

[0027] (Y-axis feed means 48) Y-axis feed means 48 has a ball screw 54 connected to Y-axis movable plate 14 and extending in the Y-axis direction, and a motor 56 that rotates ball screw 54. Y-axis feed means 48 converts the rotational motion of motor 56 into linear motion using ball screw 54 and transmits it to Y-axis movable plate 14, moving Y-axis movable plate 14 in the Y-axis direction along guide rails 12a on X-axis movable plate 12.

[0028] (Removal means 58) Furthermore, the wafer production apparatus 2 of the illustrated embodiment is provided with a peeling means 58 that peels the wafer from the ingot along the modified layer formed to a depth corresponding to the thickness of the wafer to be produced.

[0029] The peeling means 58 includes a casing 60 extending upward from the end of the guide rail 10a on the base 10, and an arm 62 supported by the casing 60 so as to be movable up and down and extending in the X-axis direction. The casing 60 incorporates an elevating means (not shown) for elevating the arm 62.

[0030] A motor 64 is attached to the tip of the arm 62, and an adsorbing piece 66 is connected to the underside of the motor 64 so as to be rotatable about an axis extending in the vertical direction. The adsorbing piece 66 is connected to suction means (not shown), and a plurality of suction holes (not shown) are formed in the underside of the adsorbing piece 66. The adsorbing piece 66 also has built-in ultrasonic vibration applying means (not shown) that applies ultrasonic vibrations to the underside of the adsorbing piece 66.

[0031] (Ingot 72) 3 shows an ingot 72 that is processed by the above-described wafer production apparatus 2. The ingot 72 shown in the figure is made of single crystal SiC (silicon carbide).

[0032] The cylindrical ingot 72 has a circular first end face 74, a circular second end face 76 located opposite the first end face 74, a circumferential surface 78 located between the first end face 74 and the second end face 76, a c-axis extending from the first end face 74 to the second end face 76, and a c-plane (see FIG. 3(c)) perpendicular to the c-axis. At least the first end face 74 has been flattened by grinding or polishing to such an extent that it does not interfere with the incidence of the laser beam LB.

[0033] In ingot 72, the c-axis is tilted with respect to a perpendicular line 80 to first end face 74, and an off-angle α (for example, α=1, 3, or 6 degrees) is formed between the c-plane and first end face 74. The direction in which the off-angle α is formed is indicated by arrow A in FIG.

[0034] A rectangular first orientation flat 82 and a rectangular second orientation flat 84, each of which indicates a crystal orientation, are formed on the peripheral surface 78 of the ingot 72. The first orientation flat 82 is parallel to the direction A in which the off angle α is formed, and the second orientation flat 84 is perpendicular to the direction A in which the off angle α is formed. As shown in FIG. 3(b), when viewed from above, the length L2 of the second orientation flat 84 is shorter than the length L1 of the first orientation flat 82 (L2 <L1)。

[0035] The ingot processed by the wafer generating apparatus of the present invention is not limited to the ingot 72 described above, but may be a SiC ingot whose c-axis is not inclined relative to the perpendicular to the first end face and whose off-angle α between the c-plane and the first end face is 0 degrees (i.e., the perpendicular to the first end face and the c-axis are aligned), or may be an ingot made of a material other than SiC, such as Si (silicon) or GaN (gallium nitride).

[0036] (Wafer production method) Next, a method for producing wafers from the ingot 72 using the above-described wafer production apparatus 2 will be described.

[0037] (holding process) In the illustrated embodiment, a holding step is first performed in which the ingot 72 is held by the holding means 4. In the holding step, the ingot 72 is fixed to the upper surface of the holding table 16 with a suitable adhesive (for example, an epoxy resin adhesive) with the first end face 74 facing upward. Note that a plurality of suction holes may be formed in the upper surface of the holding table 16, and a suction force may be generated on the upper surface of the holding table 16 to hold the ingot 72 by suction.

[0038] (Modified layer forming process) After the holding step is performed, the focal point of a laser beam LB that is transparent to the ingot 72 is positioned inside the ingot 72, and the laser beam LB is irradiated onto the ingot 72, thereby performing a modified layer formation step in which a modified layer is formed to a depth corresponding to the thickness of the wafer to be produced.

[0039] In the modified layer forming process, first, the X-axis feed means 46 is operated to position the holding table 16 directly below the imaging means 42. Next, the ingot 72 is imaged by the imaging means 42, and the positional relationship between the ingot 72 and the rotor 26 is adjusted based on the image of the ingot 72 captured by the imaging means 42. Next, the focal point FP (see FIG. 4(b)) is positioned at a depth corresponding to the thickness of the wafer to be produced (for example, about 500 μm).

[0040] 4(a) by the rotating means 22, and while the holding table 16 is being processed and fed in the X-axis direction, a laser beam LB having a wavelength that is transparent to the ingot 72 is irradiated onto the ingot 72 from the condenser lens 20. That is, while the condenser lens 20 is rotated parallel to the first end face 74 of the ingot 72 and the ingot 72 is being moved in the X-axis direction, the laser beam LB is irradiated.

[0041] This allows a large number of arc-shaped modified layers 86, in which SiC is separated into Si (silicon) and C (carbon), to be efficiently formed parallel to the first end face 74. Although not shown, cracks extend from the arc-shaped modified layers 86.

[0042] Such a modified layer forming step can be carried out, for example, under the following processing conditions. Pulse laser beam wavelength: 1064nm Average power: 6.0W Repetition frequency: 5MHz Pulse width: 10ps Numerical aperture of the condenser lens (NA): 0.8 Condenser lens rotation: 20Hz

[0043] In the modified layer forming process, it is preferable to install a beam damper that absorbs the laser beam LB around the ingot 72. This prevents the laser beam LB from being irradiated onto parts other than the ingot 72, such as the holding table 16, and thus prevents damage to the holding table 16.

[0044] Alternatively, the laser beam LB may be applied when the focal point FP is located inside the ingot 72, and the application of the laser beam LB may be stopped when the focal point FP is located outside the ingot 72.

[0045] (peeling process) After the modified layer forming step is performed, a separation step is performed in which the wafer is separated from the ingot 72 along the modified layer 86 formed to a depth corresponding to the thickness of the wafer to be produced.

[0046] In the peeling step, first, the X-axis feed means 46 is operated to position the holding table 16 below the suction piece 66 of the peeling means 58. Next, as shown in Figure 5, the arm 62 is lowered to bring the lower surface of the suction piece 66 into close contact with the upper surface (first end surface 74) of the ingot 72. Next, the suction means is operated to suck the lower surface of the suction piece 66 onto the upper surface of the ingot 72.

[0047] Then, the ultrasonic vibration applying means is operated to apply ultrasonic vibration to the lower surface of the chucking piece 66, and the chucking piece 66 is rotated by the motor 64. This makes it possible to peel the wafer 88 from the ingot 72 along the modified layer 86 formed to a depth corresponding to the thickness of the wafer to be produced. After the wafer 88 is peeled, the peeled surfaces of the ingot 72 and the wafer 88 are flattened by grinding or polishing.

[0048] As described above, the wafer generation means 6 of the illustrated embodiment includes an oscillator 18 that oscillates a laser beam LB, a focusing lens 20 that focuses the laser beam LB oscillated by the oscillator 18 inside the ingot 72, and a rotation means 22 that rotates the focusing lens 20 parallel to the end face of the ingot 72, so that a modified layer 86 can be efficiently formed inside the ingot 72.

[0049] (First Modification) The wafer generation means 6 of the present invention is not limited to the above-described embodiment. For example, instead of the optical fiber 36 shown in Fig. 2, first and second mirrors 90 and 92 for guiding the laser beam LB transmitted through the collimator lens 34 to the condenser lens 20 may be disposed between the collimator lens 34 and the condenser lens 20, as in a first modified example shown in Fig. 6.

[0050] (Second Modification) 7, a plurality of condenser lenses 20 are arranged at intervals in the rotation direction of the rotor 26. In the second modified example, eight condenser lenses 20 are arranged, but the number and intervals between the condenser lenses 20 can be set arbitrarily.

[0051] In this case, a diffractive beam splitter 94 that splits the laser beam LB reflected by the mirror 32 and a plurality of optical fibers 36 that guide the laser beam LB split by the diffractive beam splitter 94 to a plurality of focusing lenses 20 are provided inside the rotating body 26.

[0052] In the second modification, the laser beam LB emitted by the oscillator 18 is reflected by the mirror 32, then split by the diffractive beam splitter 94, and is irradiated onto the ingot from the plurality of condenser lenses 20 via the plurality of optical fibers 36. Therefore, a modified layer can be formed inside the ingot more effectively.

[0053] (Third Modification) Furthermore, as in a third modified example shown in Figure 8, there may be provided a plurality of focusing lenses 20 arranged at intervals in the rotational direction of the rotor 26, a diffraction beam splitter 94 that splits the laser beam LB reflected by the mirror 32, and a plurality of sets of first and second mirrors 90, 92 for guiding the laser beam LB split by the diffraction beam splitter 94 to the plurality of focusing lenses 20.

[0054] In the third modified example, eight condenser lenses 20 are arranged, and eight sets of first and second mirrors 90, 92 are provided, but for convenience, Figure 8(a) shows two sets of first and second mirrors 90, 92.

[0055] 7, in the third modified example, the laser beam LB emitted by the oscillator 18 is reflected by the mirror 32, then split by the diffractive beam splitter 94, and is irradiated onto the ingot from the plurality of condenser lenses 20 via the plurality of sets of first and second mirrors 90, 92. Therefore, a modified layer can be formed inside the ingot more effectively. [Explanation of symbols]

[0056] 2: Wafer generation equipment 4: Holding means 6: Wafer generation means 8. Transportation 18: Oscillator 20: Condenser lens 22: Rotation means 72: Ingot 86: Modified layer LB: Laser beam FP: Spotlight

Claims

1. A wafer production apparatus for producing wafers, The wafer generating apparatus comprises at least a holding means for holding an ingot, a wafer generating means for positioning a focal point of a laser beam that is transparent to the ingot inside the ingot and irradiating the ingot with the laser beam to form a modified layer to a depth corresponding to the thickness of the wafer to be generated, and a moving means for moving the holding means and the wafer generating means relatively, the wafer generating means includes an oscillator that oscillates a laser beam, a focusing lens that focuses the laser beam oscillated by the oscillator inside the ingot, a rotor on which the focusing lens is provided, and a rotating means that rotates the rotor to rotate the focusing lens parallel to the end face of the ingot, The condenser lens is disposed radially outward of the axis of rotation of the rotating body.

2. 2. The wafer preparation apparatus according to claim 1, wherein a plurality of said condenser lenses are arranged in the rotation direction.

3. A wafer generating apparatus as described in claim 1, wherein the modified layer is arc-shaped.

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