Wafer manufacturing method

Abstract

This invention aims to improve productivity in a wafer manufacturing method that uses laser light to produce wafers from workpieces made of single-crystal material. [Solution] The wafer manufacturing method of the present invention comprises an ion implantation step of implanting predetermined ions into a workpiece 10 made of a single crystal material to form an ion implantation modified region 12 inside the workpiece 10, and a laser irradiation step of irradiating the workpiece 10 with laser light L focused to a predetermined depth from the surface of the workpiece 10 to form a laser modified region 13 inside the workpiece 10. The process includes an ion implantation step and a laser irradiation step, followed by a peeling step in which the wafer 15 is peeled off from the workpiece 10.

Description

Technical Field

[0001] The present invention relates to a wafer manufacturing method for manufacturing a wafer from a workpiece made of a single crystal material.

Background Art

[0002] Various single crystal materials are used as materials for semiconductor substrates. Among such single crystal materials, silicon carbide (SiC), gallium nitride (GaN), diamond (C) and the like are known as difficult-to-cut materials, and conventionally, it has been difficult to cut out wafers from these ingots or blocks.

[0003] Patent Document 1 discloses a substrate processing method that uses laser light to cut out a thin substrate from a substrate material made of such a single crystal material. In this substrate processing method, focused laser light is irradiated to the inside of a substrate material such as SiC, thereby forming a modified portion that generates cleavage inside the substrate material. In this substrate processing method, by irradiating the substrate material with laser light while scanning, a plurality of cleavages generated inside the substrate material can be connected, whereby a thin substrate can be peeled off from the substrate material.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0005] The present invention aims to improve productivity in a wafer manufacturing method that uses laser light to manufacture a wafer from a workpiece made of a single crystal material.

Means for Solving the Problems

[0006] The wafer manufacturing method of the present invention is An ion implantation step involves implanting predetermined ions into a workpiece made of a single-crystal material to form an ion-implanted modified region inside the workpiece, A laser irradiation step involves irradiating the workpiece with laser light focused to a predetermined depth from the surface of the workpiece to form a laser-modified region inside the workpiece. After the ion implantation step and the laser irradiation step, a peeling step is performed to peel the wafer from the workpiece, It has.

[0007] In the wafer manufacturing method of the present invention, the laser irradiation step may be performed after the ion implantation step.

[0008] Furthermore, in the wafer manufacturing method of the present invention, the single crystal material and the ion implantation modified region may have different absorption spectra.

[0009] In the wafer manufacturing method of the present invention, the ion implantation step may be performed after the laser irradiation step.

[0010] In the wafer manufacturing method of the present invention, the ion implantation modified region may be more brittle than the single crystal material during the ion implantation step.

[0011] In the wafer manufacturing method of the present invention, the ions may be ions composed of elements constituting the single crystal material.

[0012] In the wafer manufacturing method of the present invention, the ions may consist of elements that do not function as donors and acceptors.

[0013] In the wafer manufacturing method of the present invention, the ions may have a valency of 2 or more.

[0014] In the wafer manufacturing method of the present invention, the ions may be implanted into the workpiece by channeling implantation during the ion implantation step. [Effects of the Invention]

[0015] According to the wafer manufacturing method of the present invention, productivity during wafer manufacturing is improved. [Brief Description of the Drawings]

[0016] [Figure 1] A flowchart showing the wafer manufacturing method in the first embodiment of the present invention. [Figure 2] A schematic diagram for explaining the ion implantation step in the first embodiment. [Figure 3] A schematic diagram for explaining the laser irradiation step in the first embodiment. [Figure 4] A schematic diagram showing the path along which a workpiece is irradiated with laser light in the laser irradiation step of the first embodiment. [Figure 5] A schematic diagram for explaining the peeling step in the first embodiment. [Figure 6] A flowchart showing the wafer manufacturing method in the second embodiment of the present invention. [Figure 7] A schematic diagram for explaining the laser irradiation step in the second embodiment. [Figure 8] A schematic diagram for explaining the ion implantation step in the second embodiment. [Mode for Carrying Out the Invention]

[0017] The wafer manufacturing method of the present invention will be described with reference to FIG. 1 to FIG. 8. In the first embodiment and the second embodiment described below, the same reference numerals are assigned to the same elements, and duplicate descriptions are omitted.

[0018] (First Embodiment) FIG. 1 is a flowchart showing the first embodiment which is an example of the wafer manufacturing method of the present invention. As shown in Figure 1, the wafer manufacturing method of the first embodiment includes an ion implantation step (S1-1), a laser irradiation step (S1-2), a delamination step (S1-3), and a planarization step (S1-4).

[0019] Figure 2 is a schematic diagram illustrating the ion implantation process (S1-1) in the first embodiment. As shown in Figure 2, the ion implantation step (S1-1) is a step in which predetermined ions 11 are implanted into a workpiece 10 made of a single-crystal material to form an ion-implanted modified region 12 inside the workpiece 10.

[0020] The workpiece 10 in this embodiment is an ingot or block of a single-crystal material used as a semiconductor material, and has a cylindrical shape. Furthermore, the workpiece 10 in this embodiment is a single-crystal material known to be difficult to machine, such as silicon carbide (SiC), gallium nitride (GaN), or diamond (C). However, the workpiece 10 is not limited to being made of these single-crystal materials.

[0021] In the ion implantation process (S1-1), the workpiece 10 is irradiated with an ion beam IB, thereby implanting ions 11 that constitute the ion beam IB into the interior of the workpiece 10. The implantation of ions 11 modifies the interior of the workpiece 10, forming an ion-implanted modified region 12.

[0022] In this embodiment, the energy of the ion beam IB is set so that the most ions 11 are implanted from the surface 10a of the workpiece 10 to a first depth d1. Therefore, the workpiece 10 has an ion implantation modification region 12 at and near the first depth d1.

[0023] Furthermore, the ion beam IB in this embodiment is a ribbon beam, and for example, by moving the workpiece 10 along the direction of arrow A in Figure 2, the ion beam IB is irradiated over the entire surface 10a of the workpiece 10. Therefore, the ion implantation modification region 12 is formed over the entire surface of the workpiece 10 at the first depth d1 and in the vicinity thereof. Note that the ion beam IB may also be a spot beam, and the surface 10a may be irradiated with the ion beam IB by scanning either or both of the ion beam IB and the workpiece 10.

[0024] As shown in Figure 1, the wafer manufacturing method of this embodiment includes a laser irradiation step (S1-2) that is performed after an ion implantation step (S1-1). Figure 3 is a schematic diagram illustrating the laser irradiation process (S1-2) in the first embodiment. As shown in Figure 3, the laser irradiation step (S1-2) is a step in which a laser beam L focused from the surface 10a of the workpiece 10 to a predetermined second depth d2 is irradiated onto the workpiece 10 to form a laser-modified region 13 inside the workpiece 10.

[0025] In the laser irradiation step (S1-2), the laser light L is focused by a lens (not shown) at a position that is a second depth d2 from the surface 10a of the workpiece 10. Therefore, the workpiece 10 has a laser-modified region 13 at and near the second depth d2. In this embodiment, the first depth d1 and the second depth d2 are equal, but the second depth d2 only needs to be set so that the laser-modified region 13 is formed within the ion-implanted modified region 12.

[0026] Furthermore, the first depth d1 into which the ions 11 are implanted may be set based on the second depth d2 into which the laser light L that is subsequently irradiated is focused. In other words, the first depth d1 and the second depth d2 should be set so that the laser modification region 13 is formed within the ion implantation modification region 12. Also, the entire laser modification region 13 does not have to be formed within the ion implantation modification region 12. In other words, only a part of the laser modification region 13 may be located within the ion implantation modification region 12.

[0027] Figure 4 is a schematic diagram showing the path through which the laser beam L is irradiated onto the workpiece 10 during the laser irradiation process (S1-2). In this embodiment, the laser light L is a short-pulse laser or an ultrashort-pulse laser. In this embodiment, the laser light L is irradiated onto the workpiece 10 while moving along the path indicated by the dashed arrow in Figure 4. As a result, as shown in Figures 3 and 4, a plurality of laser-modified regions 13 are formed inside the workpiece 10 at predetermined intervals.

[0028] When a laser-modified region 13 is formed in the workpiece 10, cracks 14 are generated within the workpiece 10. If the single-crystal material forming the workpiece 10 is, for example, silicon carbide (SiC), the laser light L is focused inside the SiC, causing a separation of amorphous Si and amorphous C in the laser-modified region 13. At this time, cracks 14 are formed due to the volume expansion associated with the modification. Furthermore, by irradiating the workpiece 10 with laser light L along the path shown in Figure 4, multiple cracks 14 are linked together, making the workpiece 10 easier to delaminate.

[0029] In this embodiment, the single-crystal material forming the workpiece 10 and the ion-implanted modified region 12 may have different absorption spectra. In this case, the ionic species of ions 11 are selected from those that change the absorption spectrum of the workpiece 10 when implanted into the workpiece 10.

[0030] By implanting ions 11 that alter the absorption spectrum of the workpiece 10, for example, the absorbance to the laser light L in the ion-implanted modification region 12 can be increased. This further promotes modification in the laser modification region 13.

[0031] As shown in Figure 1, the wafer manufacturing method of this embodiment includes a peeling step (S1-3) that is performed after the laser irradiation step (S1-2). Figure 5 is a schematic diagram illustrating the peeling process (S1-3). The peeling process (S1-3) is a process of peeling the wafer 15 from the workpiece 10.

[0032] A known method can be used to detach the wafer 15 from the workpiece 10. For example, the wafer 15 can be detached from the workpiece 10 by fixing the underside of the workpiece 10 and pulling it upward while adsorbing the surface 10a of the workpiece 10.

[0033] As shown in Figure 1, the wafer manufacturing method of this embodiment includes a planarization step (S1-4) that is performed after the delamination step (S1-3). As shown in Figure 5, the wafer 15 has a peeled surface 15a formed when it is separated from the workpiece 10 in the peeling step (S1-3). Although not shown in Figure 5, the peeled surface 15a has irregularities, and in the planarization step (S1-4), these irregularities are flattened by grinding and polishing. The methods for grinding and polishing the peeled surface 15a are known. For example, in the planarization step (S1-4), the peeled surface 15a may be polished by CMP (Chemical Mechanical Polishing).

[0034] (Second embodiment) Figure 6 is a flowchart showing a second embodiment, which is an example of the wafer manufacturing method of the present invention. As shown in Figure 6, the wafer manufacturing method of the second embodiment includes a laser irradiation step (S2-1), an ion implantation step (S2-2), a delamination step (S2-3), and a planarization step (S2-4).

[0035] In the wafer manufacturing method of the first embodiment, the laser irradiation step (S1-2) is performed after the ion implantation step (S1-1), whereas in the wafer manufacturing method of the second embodiment, the ion implantation step (S2-2) is performed after the laser irradiation step (S2-1).

[0036] Figure 7 is a schematic diagram illustrating the laser irradiation process (S1-2) in the second embodiment. As shown in Figure 7, in the laser irradiation step (S1-2), similar to the first embodiment, the laser light L is irradiated by a lens (not shown) so as to focus from the surface 10a of the workpiece 10 to a position at a second depth d2. Therefore, the workpiece 10 has a laser-modified region 13 at and near the second depth d2.

[0037] Figure 8 is a schematic diagram illustrating the ion implantation process (S2-2) in the second embodiment. As shown in Figure 8, in the ion implantation step (S2-2), an ion beam IB is irradiated onto the workpiece 10 in which a laser-modified region 13 has been formed inside. In the ion implantation step (S2-2), as in the first embodiment, ions 11 are implanted into the workpiece 10, and an ion-implanted modified region 12 is formed.

[0038] At this time, the energy of the ion beam IB is set so that an ion implantation modification region 12 is formed in the region containing the laser modification region 13 or crack 14. In other words, the first depth d1, in which the most ions 11 are implanted, is set based on the second depth d2.

[0039] The peeling step (S2-3) and the planarization step (S2-4) in the second embodiment are the same as the peeling step (S1-3) and the planarization step (S1-4) in the first embodiment, respectively, so their descriptions are omitted.

[0040] In the ion implantation step (S1-1) in the first embodiment and the ion implantation step (S2-2) in the second embodiment, the ion implantation modified region 12 may be embrittlement of the single-crystal material forming the workpiece 10.

[0041] In this case, the ions 11 implanted into the workpiece 10 are selected from ion species capable of embrittlement of the workpiece 10. By embrittlement of the workpiece 10 in the ion implantation modification region 12, the wafer 15 can be peeled off from the workpiece 10 even more easily in the subsequent peeling process (S1-3 or S2-3).

[0042] Furthermore, the ions 11 implanted into the workpiece 10 may consist of elements that make up the single-crystal material of the workpiece 10. In this case, for example, if the workpiece 10 is a single crystal of silicon carbide (SiC), the ions 11 are Si ions or C ions.

[0043] Si ions or C ions are implanted into SiC, and these implanted Si ions or C ions may remain in the wafer 15 after the planarization process (S1-4 or S2-4). Even in this case, since the implanted Si ions or C ions are ions composed of elements that make up SiC, they do not affect the final product of wafer 15.

[0044] Furthermore, the ions 11 implanted into the workpiece 10 may consist of elements that do not function as semiconductor donors or acceptors. In this case, the ions 11 may be, for example, H ions, He ions, Ne ions, or Ar ions. As a result, even if the implanted ions 11 remain in the wafer 15 after the planarization process (S1-4 or S2-4), the ions 11 do not function as donors or acceptors, and therefore do not affect the final product of the wafer 15.

[0045] In the ion implantation process (S1-1) in the first embodiment and the ion implantation process (S2-2) in the second embodiment, when implanting ions 11 into deeper regions, the energy of the ion beam IB can be increased. However, depending on the equipment used, it may not be possible to increase the energy of the ion beam IB to the required level. In such cases, ions 11 having a valency of 2 or more may be generated and implanted into the workpiece 10.

[0046] Alternatively, ions 11 may be implanted into the workpiece 10 by channeling implantation. Channeling implantation is a phenomenon in which ions penetrate deeply along the crystal axis by implanting ions along the crystal axis of a single crystal. When ions 11 are implanted into the workpiece 10 by channeling implantation, the ions 11 reach deeper regions from the surface 10a. In other words, by channeling implantation of ions 11, an ion-implanted modified region 12 can be formed in a deeper region.

[0047] In the first and second embodiments of the present invention, productivity is improved when manufacturing the wafer 15.

[0048] The present invention is not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the spirit of the invention. [Explanation of Symbols]

[0049] 10 Workpiece 10a surface 11 Ions 12 Ion implantation modification area 13 Laser modification area 14 Cracks 15 wafers d1 First depth d2 Second depth

Claims

1. An ion implantation step involves implanting predetermined ions into a workpiece made of a single-crystal material to form an ion-implanted modified region inside the workpiece, A laser irradiation step involves irradiating the workpiece with laser light focused to a predetermined depth from the surface of the workpiece to form a laser-modified region inside the workpiece. After the ion implantation step and the laser irradiation step, a peeling step is performed to peel the wafer from the workpiece, A method for manufacturing a tapered wafer.

2. The wafer manufacturing method according to claim 1, wherein the laser irradiation step is performed after the ion implantation step.

3. The wafer manufacturing method according to claim 2, wherein the single crystal material and the ion implantation modified region have different absorption spectra.

4. The wafer manufacturing method according to claim 1, wherein the ion implantation step is performed after the laser irradiation step.

5. The wafer manufacturing method according to any one of claims 1 to 4, wherein in the ion implantation step, the ion implanted modified region is more brittle than the single crystal material.

6. The wafer manufacturing method according to any one of claims 1 to 4, wherein the ions consist of elements constituting the single crystal material.

7. The wafer manufacturing method according to any one of claims 1 to 4, wherein the ions consist of elements that do not function as donors and acceptors.

8. The wafer manufacturing method according to any one of claims 1 to 4, wherein the ion has a valency of 2 or more.

9. The wafer manufacturing method according to any one of claims 1 to 4, wherein in the ion implantation step, the ions are implanted into the workpiece by channeling implantation.

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