Wafer manufacturing method, wafer separation method, plate-like body formation unit, substrate separation unit, substrate formation device, and wafer separation unit

Abstract

To provide a wafer manufacturing method capable of efficiently manufacturing wafers by improving the degree of freedom of the work.SOLUTION: A wafer manufacturing method according to one embodiment of the present disclosure is a method for manufacturing wafers from an ingot, and includes: a first separation step of separating a plate-like body having a predetermined thickness from an end surface of the ingot to obtain a plate-like body having the end surface and a first separation surface; a plate-like body radiation step of forming a separation layer parallel to the end surface by radiating laser light so as to be focused at an intermediate position between the end surface of the plate-like body and the first separation surface; a second separation step of separating at the separation layer to obtain a first substrate having the first separation surface and a second separation surface facing the first separation surface, and a second substrate having the end surface and a third separation surface facing the end surface; and a polishing step of polishing the first separation surface, the second separation surface, and the third separation surface to obtain a first wafer and a second wafer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a wafer manufacturing method, a wafer separating method, a plate-shaped body forming unit, a substrate separating unit, a substrate forming apparatus, and a wafer separating unit. [Background technology]

[0002] For example, the demand for semiconductors is increasing in many industries due to the electrification and automation of automobiles, etc. A method for efficiently manufacturing semiconductor wafers by efficiently slicing ingots has been proposed (JP 2016-062949 A). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-062949 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the ingot slicing method described in Patent Document 1, a separation layer for separating an ingot into a first ingot and a second ingot is formed by using a laser beam, and after forming a plurality of separation layers on the first ingot to obtain a plurality of plates, the separation surface of the second ingot is flattened. In this manner, it is said that the manufacturing efficiency can be improved compared to obtaining the plates one by one from the ingot and flattening the separation surface each time. In this method, there is a risk that work on the second ingot cannot be performed until a plurality of separation layers are further formed on the first ingot to obtain a plurality of plates.

[0005] In view of the above-mentioned circumstances, an object of the present disclosure is to provide a wafer manufacturing method capable of efficiently manufacturing wafers by improving the degree of freedom of operation. [Means for solving the problem]

[0006] A wafer manufacturing method according to one embodiment of the present disclosure devised to solve the above-mentioned problems is a method for manufacturing wafers from an ingot, comprising: a first separation step of separating an end face of the ingot at a predetermined thickness to obtain a plate-like body having the end face and a first separation surface; a plate-like body irradiation step of irradiating the plate-like body with laser light so that the light is focused at an intermediate position between the end face and the first separation surface to form a separation layer parallel to the end face; a second separation step of separating at the separation layer to obtain a first substrate having the first separation surface and a second separation surface opposite the first separation surface, and a second substrate having the end face and a third separation surface opposite the end face; and a polishing step of polishing the first separation surface, the second separation surface, and the third separation surface to obtain a first wafer and a second wafer. Effect of the Invention

[0007] A wafer manufacturing method according to an aspect of the present disclosure can improve the freedom of operation and efficiently manufacture wafers. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic side view showing a substrate forming apparatus according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described.

[0010] (1) A wafer manufacturing method according to one embodiment of the present disclosure is a method for manufacturing wafers from an ingot, the method including: a first separation step of separating an end face of the ingot at a predetermined thickness to obtain a plate-like body having the end face and a first separation surface; a plate-like body irradiation step of irradiating the plate-like body with laser light so as to be focused at an intermediate position between the end face and the first separation surface to form a separation layer parallel to the end face; a second separation step of separating the plate-like body at the separation layer to obtain a first substrate having the first separation surface and a second separation surface opposite the first separation surface, and a second substrate having the end face and a third separation surface opposite the end face; and a polishing step of polishing the first separation surface, the second separation surface, and the third separation surface to obtain a first wafer and a second wafer.

[0011] In this wafer manufacturing method, an ingot is separated into a plate-like body and the remainder of the ingot, and the plate-like body is further separated into two substrates and polished to obtain a wafer. Since a new plate-like body can be separated from the remainder of the ingot while the plate-like body is being separated into the two substrates, the plate-like body and the substrate can be obtained efficiently, and as a result, wafers can be efficiently manufactured.

[0012] (2) In the above (1), the first separation step may include an ingot irradiation step of irradiating the ingot with a laser beam so as to be focused at a predetermined depth from the end face to form a first separation layer parallel to the end face, and the plate-like body may be separated at the first separation layer. By forming a separation layer in the ingot by irradiating the ingot with a laser beam and separating the plate-like body, the plate-like body can be obtained more efficiently.

[0013] (3) In the above (1) or (2), the wafer may be a SiC wafer or a GaN wafer, that is, the wafer manufacturing method is suitable for manufacturing SiC wafers and GaN wafers.

[0014] (4) In any one of (1) to (3) above, the first separation surface, the second separation surface, and the third separation surface separated in the first separation step and the second separation step may have a maximum height Rz of 100 μm or less. By separating the first separation surface so that the maximum height Rz of each separation surface is 100 μm or less, each separation surface can be efficiently planarized by polishing.

[0015] (5) In any one of (1) to (4), the plate-like body may have a thickness of 1.20 mm or less. By making the thickness of the plate-like body 1.20 mm or less, the number of wafers obtainable from the ingot can be increased.

[0016] (6) In any one of (1) to (5), the first wafer and the second wafer may have a thickness of 0.50 mm or less. By making the thickness of the first wafer and the second wafer 0.50 mm or less, it is possible to increase the reliability of increasing the number of wafers obtained from the ingot.

[0017] (7) In any one of (1) to (6), the laser light may be a femtosecond pulsed laser light. By irradiating the laser light with the femtosecond pulsed laser light, the thickness of the separation layer formed is suppressed, so that the wafer can be manufactured more efficiently.

[0018] (8) A wafer separation method according to one embodiment of the present disclosure includes a preparation step of preparing a ready-made wafer, an irradiation step of irradiating the prepared wafer with laser light so as to focus at a middle position in a thickness direction thereof to form a separation layer, a substrate separation step of separating the wafer at the separation layer to obtain a first substrate and a second substrate, and a polishing step of polishing separation surfaces of the first substrate and the second substrate to obtain a first wafer and a second wafer.

[0019] This wafer manufacturing method can efficiently manufacture wafers because a ready-made wafer can be separated into a plurality of substrates and polished to produce new wafers.

[0020] (9) In the above (8), the thickness of the prepared wafer may be 1.00 mm or less. By separating the wafer having a thickness of 1.00 mm or less, a thinner wafer substrate can be formed.

[0021] (10) A plate-shaped body forming unit according to one embodiment of the present disclosure is a unit for forming a plate-shaped body for a wafer from an ingot, and includes a stage capable of moving the ingot held therein in a direction perpendicular to the optical axis of the irradiated laser light, and a laser emission unit that emits femtosecond pulsed laser light to the ingot held on the stage.

[0022] Since the plate-shaped body forming unit includes a laser emission part that emits femtosecond pulsed laser light, the plate-shaped body can be efficiently formed from the ingot, and thus wafers can be efficiently manufactured.

[0023] (11) A substrate separation unit according to one embodiment of the present disclosure is a unit that separates a plate-like body separated from an ingot into a plurality of wafer substrates, and includes a stage that can move the plate-like body it holds in a direction perpendicular to the optical axis of the irradiated laser light, and a laser emission unit that emits femtosecond pulsed laser light to the plate-like body held on the stage.

[0024] Since the substrate separation unit is equipped with a laser emission part that emits femtosecond pulsed laser light, the plate-like body separated from the ingot can be efficiently made into a substrate, and thus wafers can be efficiently manufactured.

[0025] (12) A substrate forming apparatus according to an aspect of the present disclosure includes the plate-shaped body forming unit and the substrate separating unit.

[0026] The substrate forming apparatus is equipped with the plate-shaped body forming unit capable of efficiently forming plate-shaped bodies, and the substrate separation unit capable of efficiently separating substrates from the plate-shaped bodies, thereby enabling wafers to be manufactured more efficiently.

[0027] (13) A wafer separation unit according to one embodiment of the present disclosure is a unit for separating a ready-made wafer into a plurality of wafer substrates, and includes a stage capable of moving a held wafer in a direction perpendicular to an optical axis of an irradiated laser light, and a laser emission unit that emits femtosecond pulsed laser light to the wafer held on the stage.

[0028] The wafer separation unit includes a laser emission part that emits femtosecond pulsed laser light and can separate a ready-made wafer to form a plurality of wafer substrates, thereby enabling efficient manufacture of wafer substrates.

[0029] The maximum height Rz refers to a value measured in accordance with JIS B 0601-2001. Parallel to the end face includes not only perfect parallelism with the end face, but also a deviation of approximately 10 degrees from perfect parallelism.

[0030] [Details of the embodiment of the invention] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings as appropriate. Note that the drawings are illustrative of the embodiment, and the shape, size, scale, arrangement, etc. of each component (member) may differ from the actual one.

[0031] First Embodiment The wafer manufacturing method, which is one embodiment of the present disclosure, is a method for manufacturing wafers from an ingot, and includes a first separation step of separating an end face of the ingot at a predetermined thickness to obtain a plate-like body having the end face and a first separation surface; a plate-like body irradiation step of irradiating the plate-like body with laser light so that the light is focused at an intermediate position between the end face and the first separation surface to form a separation layer parallel to the end face; a second separation step of separating at the separation layer to obtain a first substrate having the first separation surface and a second separation surface opposite the first separation surface, and a second substrate having the end face and a third separation surface opposite the end face; and a polishing step of polishing the first separation surface, the second separation surface, and the third separation surface to obtain a first wafer and a second wafer.

[0032] The shape of the ingot is not particularly limited, and may be, for example, approximately cylindrical. The size (dimensions) of the ingot is not particularly limited, and may be, for example, 20 cm, 50 cm, 70 cm, 100 cm or more in height (axial thickness), and 4 inches, 6 inches, 8 inches, 10 inches or more in diameter.

[0033] The material of the ingot is not particularly limited, and may be a compound material such as LT (lithium tantalate), LN (lithium niobate), InP (indium phosphide), GaAs (gallium arsenide), SiC (silicon carbide), or GaN (gallium nitride), and is preferably SiC or GaN. That is, the wafer obtained by the wafer manufacturing method is preferably a SiC wafer or a GaN wafer. An ingot containing SiC or GaN and a plate-shaped body separated from the ingot are suitable for the wafer manufacturing method because a separation layer can be easily formed by irradiation with a laser beam. The ingot may be a single crystal or a polycrystal.

[0034] [First separation step] The first separation step is not particularly limited, and may be, for example, a plate-shaped body cut out by cutting with a wire saw, but it is preferable to include an ingot irradiation step in which laser light is irradiated so as to be focused at a predetermined depth from an end face of the ingot to form a first separation layer parallel to the end face, and the plate-shaped body is separated at the first separation layer.

[0035] In cutting an ingot with a wire saw, at least the thickness (width) of the wire saw becomes the width for cutting (kerf loss), so there is a risk that the amount of loss of the ingot (portion that cannot be made into wafers) increases and the amount (number) of wafers obtained from the ingot decreases. The amount of loss of the ingot can be reduced by forming a first separation layer in the ingot with a laser beam and separating the plate-like body from the remaining part of the ingot at this first separation layer.

[0036] In addition, when cutting an ingot with a wire saw, it is difficult to suppress the surface roughness (amount of unevenness) of the cut surface (separation surface) between the plate-like body and the remaining part of the ingot, so the amount of polishing required to smooth the separation surface increases, and there is a risk of increasing the amount of loss of the ingot. By separating the plate-like body and the remaining part of the ingot with a separation layer formed by a laser beam, the surface roughness of the separation surface can be easily suppressed. In addition, separation at the separation layer formed by a laser beam makes it unnecessary to replace the wire saw, and can reduce the time required to separate the plate-like body compared to cutting with a wire saw.

[0037] The separation layer formed by the irradiation of laser light is a portion in which the composition of the ingot is modified by the focusing of the laser light, and is a region (layer) in which physical properties such as mechanical strength and density have changed from the surroundings (non-modified regions). The focusing of the laser light causes partial modification, such as partial melting of the ingot or the formation of partial fractures (fine cracks). By continuously or intermittently irradiating the ingot with laser light substantially parallel to the end face so as to focus the light at a predetermined depth from the end face, multiple modified portions are formed, which become a separation layer. The plate-shaped body and the remaining part of the ingot can be easily separated by this separation layer (multiple modified portions).

[0038] The separation layer is formed approximately parallel to the end face of the ingot. That is, the separation layer is formed approximately perpendicular to the axial direction of the ingot. The separation layer may be formed along the off-angle of the ingot. When the separation layer is formed along the off-angle of the ingot, the laser light may be irradiated while changing the focusing position (distance from the end face) so that the laser light is focused along the off-angle.

[0039] The upper limit of the thickness of the separation layer formed in the ingot by irradiation with the laser light is preferably 120 μm, more preferably 100 μm, even more preferably 80 μm, and particularly preferably 60 μm. By setting the thickness of the separation layer to the upper limit or less, the kerf loss of the ingot can be reduced. The lower limit of the thickness of the separation layer is not particularly limited and may be 5 μm, 10 μm, 30 μm, or 40 μm.

[0040] The separation surface (first separation surface) of the plate-like body formed by separation in the separation layer is preferably smooth, and specifically, the maximum height Rz is preferably 100 μm or less. The upper limit of the maximum height Rz is more preferably 70 μm, further preferably 50 μm, and particularly preferably 40 μm. By setting the maximum height Rz of the first separation surface to the upper limit or less, the amount of polishing of the first separation surface can be reduced to reduce the amount of loss of the ingot, thereby improving the efficiency of wafer manufacturing. The lower limit of the maximum height Rz is not particularly limited and may be 5 μm, 10 μm, 15 μm, or 20 μm.

[0041] The average thickness of the plate-like bodies separated from the ingot in the first separation step (the distance between the end face and the first separation surface opposite to the end face) is preferably 1.20 mm or less. The upper limit of the average thickness of the plate-like bodies is preferably 1.00 mm, more preferably 0.90 mm. By setting the average thickness of the plate-like bodies to the upper limit or less, the number of plate-like bodies obtained can be increased, and thus the number of wafers obtained can be increased. The lower limit of the average thickness of the plate-like bodies is not particularly limited, and may be, for example, 0.50 mm. The average thickness means the average value of thicknesses at any 10 points.

[0042] The laser light is preferably a pulsed laser light in order to efficiently form a plurality of the modified portions. The pulsed laser light may be a nanosecond pulsed laser light or a picosecond pulsed laser light, but is particularly preferably a femtosecond pulsed laser light. Since the femtosecond pulsed laser light has excellent absorption efficiency of the laser energy in the irradiated object, the fine modified portions can be easily formed in the ingot by irradiating the laser light. Therefore, the increase in the thickness of the separation layer can be effectively suppressed, and the maximum height Rz can be effectively suppressed. In addition, while the nanosecond pulsed laser light or the picosecond pulsed laser light is easily affected by the crystal orientation of the ingot, the femtosecond pulsed laser light forms the modified portions finely, so that the influence can be suppressed, and the separation layer can be formed so as to be approximately perpendicular to the axial direction of the ingot to separate the plate-shaped body.

[0043] Nitrogen may be used in the manufacture of an ingot (e.g., nitrogen doping, etc.). In the ingot, the high nitrogen concentration parts may turn black (become blackened). In such black parts, energy is not effectively absorbed by nanosecond pulsed laser light or picosecond pulsed laser light, so it may be necessary to appropriately adjust the energy of the laser light to form a separation layer. With femtosecond pulsed laser light, energy is effectively absorbed even in the black parts, so a separation layer may be formed efficiently and stably without the need for adjusting the energy of the laser light.

[0044] The wavelength, pulse width, repetition frequency, etc. of the femtosecond pulsed laser light irradiated to the ingot are not particularly limited, and may be appropriately selected depending on the material and size of the ingot, the depth at which the separation layer is formed (the distance from the end face), the thickness of the separation layer to be formed, etc. Specifically, for example, the laser light may have a fundamental wavelength (about 1064 nm), a pulse width of 500 femtoseconds or less, and a repetition frequency of 50 kHz or more and 100 kHz or less.

[0045] The procedure for forming a separation layer in an ingot is not particularly limited. For example, a stage holding an ingot moves in one direction (X direction) perpendicular to the irradiated laser light, and the laser light forms the above-mentioned multiple modified parts in the ingot during this movement. When the ingot passes the laser light, the stage moves the ingot a predetermined distance in a direction (Y direction) perpendicular to the above-mentioned one direction, and then moves it again in the X direction, forming new multiple modified parts approximately parallel to the above-mentioned multiple modified parts. By repeating this process, a separation layer is formed in the ingot.

[0046] The procedure for separating the plate-like body from the ingot is not particularly limited, and any known procedure can be used, such as fixing the ingot and peeling off the plate-like body by adsorbing, bonding, or sticking the end face, or rotating the plate-like body or the remaining part of the ingot approximately parallel to the end face to separate the plate-like body from the remaining part of the ingot (threading).

[0047] [Plate irradiation process] In the plate-shaped body irradiation step, a laser beam is irradiated to the plate-shaped body so as to be focused at a midpoint between the end face and the first separation surface, forming a separation layer parallel to the end face. That is, a separation layer (second separation layer) is formed in the plate-shaped body so that the plate-shaped body can be divided into approximately two equal parts in the thickness direction. The second separation layer formed on the plate-shaped body may be different from the first separation layer, but is preferably approximately the same. The laser beam irradiated to the plate-shaped body may be different from the laser beam irradiated to the ingot, or may be approximately the same. The laser beam irradiated to the plate-shaped body is preferably a femtosecond pulse laser beam.

[0048] The procedure for forming the second separation layer on the plate-like body may be the same as that for forming the first separation layer on an ingot, for example, by irradiating the plate-like body with laser light while moving a stage holding the plate-like body in the XY directions.

[0049] [Second separation step] The second separation step involves separation at the second separation layer to obtain a first substrate having the first separation surface and a second separation surface opposite to the first separation surface, and a second substrate having the end surface and a third separation surface opposite to the end surface.

[0050] The procedure for separating the first substrate and the second substrate (hereinafter also simply referred to as substrates) from the plate-like body is not particularly limited, and a known procedure can be used, similar to the procedure for separating the plate-like body from the ingot.

[0051] The thickness of each of the separated substrates is preferably 700 μm or less. The upper limit of the thickness of the substrate is more preferably 600 μm, further preferably 500 μm, and particularly preferably 400 μm. When the thickness of each of the substrates is equal to or less than the upper limit, the wafer can be efficiently manufactured. The lower limit of the thickness of the substrate is not particularly limited and may be 160 μm or 180 μm.

[0052] The separation surfaces obtained by separating the plate-like body, that is, the second separation surface and the third separation surface, are preferably smooth like the first separation surface, and specifically, the maximum height Rz is preferably 100 μm or less.

[0053] [Substrate forming equipment] The above-mentioned substrate can be efficiently obtained by using a substrate forming apparatus 1 as shown in, for example, Figures 1, 2, and 3. The substrate forming apparatus 1 includes a plate-shaped body forming unit 10 and a substrate separating unit 20. The substrate forming apparatus 1 may be a combination of the plate-shaped body forming unit 10 and the substrate separating unit 20, each of which is an independent unit, or each of which may be disposed in a single housing.

[0054] (Plate forming unit) The plate-like body forming unit 10 includes a stage (first stage 11) capable of moving the ingot 100 held therein in a direction perpendicular to the optical axis of the irradiated laser light L (shown by a dotted line in each figure), and a laser emission section (first laser emission section 12) that emits femtosecond pulsed laser light to the ingot 100 held on the first stage 11.

[0055] The plate-like body forming unit 10 also has a plurality of reflecting mirrors 30 (three in FIG. 1) that reflect the laser light L emitted by the first laser emission part 12, and a lens (first lens 40) for focusing the laser light L reflected by the reflecting mirrors 30 within the ingot 100. The plate-like body forming unit 10 may also include other optical components and optical devices such as mirrors and lenses as long as they do not impede the formation of the separation layer.

[0056] The first stage 11 holds the ingot 100. The means by which the first stage 11 holds the ingot 100 is not particularly limited, and the ingot 100 may be held by any known means. In this embodiment, the ingot 100 is held so that its axial direction is substantially vertical (Z direction in FIG. 1). That is, the ingot 100 is irradiated with laser light L in the Z direction.

[0057] The first stage 11 can move in a direction perpendicular to the optical axis of the irradiated laser light L. That is, the first stage 11 can move in a substantially horizontal plane (the X and Y directions in FIG. 1). The plate-shaped body forming unit 10 forms a separation layer (first separation layer 110) in the ingot 100 by the first stage 11 moving relative to the irradiated laser light L. The first separation layer 110 is formed substantially perpendicular to the axial direction.

[0058] Specifically, for example, the first stage 11 moves the ingot 100 in the X direction, and during this movement, the laser light L forms the above-mentioned multiple modified portions in the ingot 100. When the ingot 100 passes the irradiation position of the laser light L, the first stage 11 moves the ingot 100 a predetermined distance in the Y direction and then moves it again in the X direction to form new multiple modified portions approximately parallel to the above-mentioned multiple modified portions. By repeating this, the first separation layer 110 is formed. It is preferable that the first stage 11 is also movable in the Z direction. In other words, it is preferable that the distance between the first stage 11 and the first lens 40 can be adjusted.

[0059] The first laser emission unit 12 includes a light source (laser oscillator) that emits femtosecond pulsed laser light, an amplifier that amplifies the femtosecond pulse, an excitation laser that excites the amplifier, etc. It is preferable that the first laser emission unit 12 is capable of arbitrarily setting the wavelength, pulse width, repetition frequency, output, etc. of the emitted laser light L.

[0060] The first lens 40 focuses the laser light L so that a separation layer (first separation layer 110) is formed in the ingot 100. The diameter of the laser light L focused by the first lens 40 on the first separation layer 110 is not particularly limited, and may be appropriately set depending on the depth of the separation layer to be formed (distance from the end face), the material of the ingot 100, the size of the ingot 100, the size of the modified portion formed by the irradiation of the laser light, the thickness of the separation layer, the speed at which the separation layer is formed (scanning speed), and the like. It is preferable that the first lens 40 is movable in the Z direction. That is, it is preferable that the first lens 40 is disposed so that the distance from the ingot 100 can be adjusted.

[0061] The ingot 100 with the first separation layer formed thereon is separated into a plate-like body and the remaining part of the ingot 100 by a plate-like body separating means (not shown).

[0062] (Substrate separation unit) The substrate separation unit 20 includes a stage (second stage 21) capable of moving the plate-like body 200 it holds in a direction perpendicular to the optical axis of the irradiated laser light L, and a laser emission section (second laser emission section 22) that emits femtosecond pulsed laser light to the plate-like body 200 held on the second stage 12.

[0063] Furthermore, the substrate separation unit 20 has a plurality of reflecting mirrors 31 (three in FIG. 1) that reflect the laser light L emitted by the second laser emission section 22, and a lens (second lens 41) that focuses the laser light L reflected by the reflecting mirrors 31 within the plate-shaped body 200. The substrate separation unit 20 may also include other optical system components and optical system devices, such as other mirrors and lenses, to the extent that they do not impede the formation of the separation layer.

[0064] The second stage 21 holds the plate-like body 200. The means by which the second stage 21 holds the plate-like body 200 is not particularly limited, and the plate-like body 200 may be held by a known means. In this embodiment, the plate-like body 200 is held so that the normal to its surface is in a substantially vertical direction (Z direction in FIG. 1). That is, the laser light L is irradiated onto the plate-like body 200 in the Z direction.

[0065] The second stage 21, like the first stage 11, can move in a direction perpendicular to the optical axis of the irradiated laser light L. That is, the second stage 21 can move in the X direction and the Y direction. The substrate separation unit 20 forms a separation layer (second separation layer 210) in the plate-like body 200 by the second stage 21 moving relatively to the irradiated laser light L. The second separation layer 210 is formed approximately perpendicular to the axial direction. It is preferable that the second stage 21 is also movable in the Z direction.

[0066] The second laser emission section 22 may be the same as the first laser emission section 11 .

[0067] The second lens 41 focuses the laser light L so that the second separation layer 210 is formed in the plate-like body 200. The diameter of the laser light L focused by the second lens 41 at the second separation layer 210 is not particularly limited, and may be the same as the diameter of the laser light L focused at the first separation layer 110. The second lens 41 is preferably movable in the Z direction.

[0068] The plate-like body 200 on which the second separation layer 210 is formed is separated into a first substrate and a second substrate by a substrate separation means (not shown).

[0069] The plate-shaped body forming unit 10 and the substrate separating unit 20 include laser emission parts 12, 22 that emit femtosecond pulsed laser light, and therefore can easily form separation layers 110, 210 in the ingot 100 and the plate-shaped body 200. In addition, since the separation layers 110, 210 are formed with femtosecond pulsed laser light, the thickness of the separation layers 110, 210 can be easily suppressed. The substrate forming apparatus 1 includes the plate-shaped body forming unit 10 and the substrate separating unit 20, and therefore can efficiently form plate-shaped bodies for wafers and substrates separated from the plate-shaped bodies, and can therefore efficiently manufacture wafers.

[0070] [Polishing process] In the polishing step, the first separation surface, the second separation surface, and the third separation surface of the first substrate and the second substrate obtained in the second separation step are polished to obtain a first wafer and a second wafer. In the polishing step, the end surface may be polished. The polishing method is not particularly limited, and a known method such as polishing using a grinder can be adopted.

[0071] Since the maximum height Rz of each separation surface of the first substrate and the second substrate is suppressed, the polishing amount is small, and polishing can be performed efficiently. The upper limit of the polishing amount in the polishing direction (normal direction of each separation surface) of each separation surface of the first substrate and the second substrate is preferably 100 μm or less, more preferably 70 μm, even more preferably 50 μm, and particularly preferably 40 μm. The lower limit of the polishing amount is not particularly limited, and may be 5 μm, 10 μm, 15 μm, or 20 μm.

[0072] The first separation surface may be polished prior to the second separation step.

[0073] The upper limit of the thickness of the wafer obtained by polishing the first substrate and the second substrate is preferably 450 μm, more preferably 350 μm, more preferably 300 μm, even more preferably 200 μm, even more preferably 150 μm, and particularly preferably 100 μm. The lower limit of the thickness of the wafer is not particularly limited and may be 50 μm or 80 μm.

[0074] The wafer manufacturing method can simultaneously form a separation layer on a plate-like body separated from an ingot to separate it into two substrates, and form a separation layer on the remaining portion of the ingot from which the plate-like body was separated to separate a new plate-like body, thereby making it possible to efficiently obtain the substrates and, in turn, efficiently manufacture wafers.

[0075] In the wafer manufacturing method, the thickness of the separation layer can be easily and effectively suppressed by using a femtosecond pulsed laser beam as the laser beam for forming the separation layer, and the suppression of the thickness of the separation layer can suppress the maximum height Rz of the separation surface formed by separation at this separation layer. Therefore, the loss amount of the ingot (kerf loss and polishing amount) can be effectively reduced, and the number of wafers obtained from the ingot can be easily increased. Second Embodiment

[0076] Next, a wafer separation method according to another embodiment of the present disclosure will be described in detail.

[0077] The wafer separation method includes a preparation step of preparing a ready-made wafer, an irradiation step of irradiating the prepared wafer with laser light so as to be focused at a middle position in the thickness direction to form a separation layer, a substrate separation step of obtaining a first substrate and a second substrate by separating the wafer at the separation layer, and a polishing step of obtaining a first wafer and a second wafer by polishing the separation surfaces of the first substrate and the second substrate. The wafer separation method separates one ready-made wafer to obtain two wafers.

[0078] [Preparation process] The ready-made wafer is a wafer having a first surface that has been flattened (polished) and a second surface that has been flattened. The material of the wafer to be prepared is not particularly limited, and examples thereof include compound materials such as LT (lithium tantalate), LN (lithium niobate), InP (indium phosphide), GaAs (gallium arsenide), SiC (silicon carbide), and GaN (gallium nitride), with SiC and GaN being preferred. The wafer may be either single crystal or polycrystalline.

[0079] The thickness of the wafer may be 1.00 mm or less. The upper limit of the thickness of the wafer may be 0.90 mm, 0.85 mm, 0.80 mm, or 0.75 mm. The lower limit of the thickness of the wafer is not particularly limited and may be, for example, 0.3 mm or 0.4 mm. When the thickness of the wafer before separation does not exceed the upper limit, two new wafers having a small thickness can be obtained.

[0080] [Irradiation process] In the irradiation step, a separation layer is formed by irradiating the wafer with a laser beam so as to be focused at a middle position in the thickness direction of the wafer. That is, a separation layer is formed at a middle position (center position) in the thickness direction of the wafer so that the wafer can be divided into approximately two equal parts in the thickness direction. The laser beam irradiated to the wafer is preferably a femtosecond pulsed laser beam.

[0081] The upper limit of the thickness of the separation layer formed in the wafer is preferably 120 μm, more preferably 100 μm, even more preferably 80 μm, and particularly preferably 60 μm. By setting the thickness of the separation layer to the upper limit or less, the kerf loss of the wafer can be reduced. The lower limit of the thickness of the separation layer is not particularly limited and may be 5 μm, 10 μm, 30 μm, or 40 μm.

[0082] [Substrate separation process] In the substrate separation step, the first substrate and the second substrate are obtained by separation at the separation layer. The procedure for separating the first substrate and the second substrate (hereinafter also simply referred to as substrate) from the wafer is not particularly limited, and known means can be used, as in the case of separating the plate-like body described above.

[0083] The thickness of each of the separated substrates is preferably 500 μm or less. The upper limit of the thickness of the substrate is more preferably 450 μm, further preferably 400 μm, and particularly preferably 350 μm. When the thickness of each of the substrates is equal to or less than the upper limit, new wafers can be efficiently obtained. The lower limit of the thickness of the substrate is not particularly limited and may be 160 μm or 180 μm.

[0084] The separation surface of each of the substrates obtained by separation at the separation layer is preferably smooth, and specifically, the maximum height Rz is preferably 100 μm or less. The upper limit of the maximum height Rz is more preferably 70 μm, further preferably 50 μm, and particularly preferably 40 μm. By making the maximum height Rz of the first separation surface equal to or less than the upper limit, the amount of polishing of the first separation surface can be reduced, thereby reducing the amount of loss of the wafer. The lower limit of the maximum height Rz is not particularly limited, and may be 5 μm, 10 μm, 15 μm, or 20 μm.

[0085] The substrate is preferably obtained by using the substrate separation unit described above. Specifically, in the substrate separation unit 20, the wafer is placed on the stage 21 instead of the plate-like body 200, and is irradiated with femtosecond pulsed laser light, whereby the first substrate and the second substrate can be easily obtained.

[0086] [Polishing process] In the polishing step, the separation surfaces of the first substrate and the second substrate are polished to obtain a first wafer and a second wafer. The polishing means is not particularly limited, and for example, a known means such as polishing using a grinder can be used.

[0087] Since the maximum height Rz of each separation surface of the first substrate and the second substrate is suppressed, the polishing amount is small, and polishing can be performed efficiently. The upper limit of the polishing amount in the polishing direction (normal direction of each separation surface) of each separation surface of the first substrate and the second substrate is preferably 100 μm or less, more preferably 70 μm, even more preferably 50 μm, and particularly preferably 40 μm. The lower limit of the polishing amount is not particularly limited, and may be 5 μm, 10 μm, 15 μm, or 20 μm.

[0088] The upper limit of the thickness of the wafer obtained by polishing the first substrate and the second substrate is preferably 450 μm, more preferably 350 μm, more preferably 300 μm, even more preferably 200 μm, even more preferably 150 μm, and particularly preferably 100 μm. The lower limit of the thickness of the wafer is not particularly limited and may be 50 μm or 80 μm.

[0089] This wafer manufacturing method can easily and efficiently manufacture thin wafers because it is possible to obtain two new wafers by separating one ready-made wafer.

[0090] [Other embodiments] The above-mentioned embodiment does not limit the configuration of the present invention. Therefore, the above-mentioned embodiment may omit, replace or add components of each part of the above-mentioned embodiment based on the description in this specification and common technical knowledge, and it should be understood that all of these are within the scope of the present invention.

[0091] The number of substrates obtained from the plate-like body or wafer may be three or more. For example, in the plate-like body irradiation step or the irradiation step, two separation layers for dividing the plate-like body or wafer into three equal parts in the thickness direction may be formed, and the three substrates may be separated in the second separation step or the substrate separation step. [Industrial Applicability]

[0092] A wafer manufacturing method according to an embodiment of the present disclosure can efficiently manufacture wafers and is therefore suitable for use in the manufacture of semiconductor products, etc. [Explanation of symbols]

[0093] 1 Substrate forming equipment 10 Plate-shaped body forming unit 11 First Stage 12 First laser emission section 20 Substrate separation unit 21 Second Stage 22 Second laser emission section 30,31 Reflective mirror 40,41 Lens 100 ingots 110 1st separation layer 200 Plate-shaped body 210 Second separation layer L Laser light

Claims

1. 1. A method for producing wafers from an ingot, comprising the steps of: a first separation step of separating a predetermined thickness from an end surface of the ingot to obtain a plate-like body having the end surface and a first separation surface; a plate-like body irradiation step of irradiating the plate-like body with laser light so as to be focused at an intermediate position between the end face and the first separation surface, thereby forming a separation layer parallel to the end face; a second separation step of separating the substrate at the separation layer to obtain a first substrate having the first separation surface and a second separation surface opposite to the first separation surface, and a second substrate having the end surface and a third separation surface opposite to the end surface; a polishing step of polishing the first separation surface, the second separation surface, and the third separation surface to obtain a first wafer and a second wafer; A wafer manufacturing method comprising:

2. 2. The wafer manufacturing method according to claim 1, wherein the first separation step includes an ingot irradiation step of irradiating laser light so as to be focused at a predetermined depth from an end face of the ingot to form a first separation layer parallel to the end face, and the plate-shaped body is separated at the first separation layer.

3. 3. The method for producing a wafer according to claim 1, wherein the wafer is a SiC wafer or a GaN wafer.

4. 3. The wafer manufacturing method according to claim 1, wherein the first separation surface, the second separation surface and the third separation surface separated in the first separation step and the second separation step have a maximum height Rz of 100 μm or less.

5. 3. The wafer manufacturing method according to claim 1, wherein the thickness of the plate-like body is 1.20 mm or less.

6. 3. The wafer manufacturing method according to claim 1, wherein the first wafer and the second wafer have a thickness of 0.50 mm or less.

7. 3. The wafer manufacturing method according to claim 1, wherein the laser light is a femtosecond pulse laser light.

8. a preparation step of providing a pre-fabricated wafer; an irradiation step of irradiating the prepared wafer with laser light so as to be focused at a middle position in a thickness direction of the wafer to form a separation layer; a substrate separation step of obtaining a first substrate and a second substrate by separating the substrate at the separation layer; a polishing step of polishing the separation surfaces of the first substrate and the second substrate to obtain a first wafer and a second wafer; A wafer separation method comprising:

9. 9. The wafer separation method according to claim 8, wherein the wafers prepared have a thickness of 1.00 mm or less.

10. A unit for forming a plate-shaped body for a wafer from an ingot, a stage capable of moving the held ingot in a direction perpendicular to the optical axis of the irradiated laser light; a laser emission unit that emits femtosecond pulse laser light to the ingot held on the stage; A plate-shaped body forming unit comprising:

11. A unit for separating a plate-shaped body separated from an ingot into a plurality of wafer substrates, a stage capable of moving the plate-like body held in a direction perpendicular to the optical axis of the irradiated laser light; a laser emission unit that emits femtosecond pulse laser light onto the plate-like body held on the stage; A substrate separation unit comprising:

12. The plate-shaped body forming unit according to claim 10, The substrate separation unit according to claim 11 ; A substrate forming apparatus comprising:

13. A unit for separating a ready-made wafer into a plurality of wafer substrates, comprising: a stage capable of moving a held wafer in a direction perpendicular to the optical axis of the irradiated laser light; a laser emission unit that emits femtosecond pulse laser light to the wafer held on the stage; A wafer separation unit comprising:

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