Manufacturing method for semiconductor devices

Abstract

To provide a technology that suppresses deformation of a semiconductor wafer that is peeled from a semiconductor ingot in a manufacturing method of a semiconductor device that uses a laser peeling technology.SOLUTION: A manufacturing method of a semiconductor device comprises: a deformation prevention layer forming step that forms a deformation prevention layer 30 on a first principal surface of a semiconductor ingot 1 which has the first principal surface 1a and a second principal surface 1b; a laser irradiation step in which a surface 3 extending in predetermined depth within the semiconductor ingot is irradiated with a laser, the laser irradiation step in which an inside of the semiconductor ingot is irradiated with the laser; and a peeling step in which a semiconductor wafer 2 including the first principal surface is peeled from a residual layer of the semiconductor ingot along a surface irradiated with the laser.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed in this specification relates to a method for manufacturing a semiconductor device.

[0002] In order to manufacture a semiconductor device, a technique has been proposed to cut out a semiconductor wafer from one main surface of a semiconductor ingot using a laser lift-off technique. In such a laser lift-off technique, a laser is irradiated into the semiconductor ingot to form a modified layer, and the semiconductor wafer is peeled off from the remaining layers of the semiconductor ingot along the modified layer. Patent Document 1 discloses an example of a method for manufacturing a semiconductor device using a laser lift-off technique.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] At the site where the modified layer is formed in the semiconductor ingot, the crystal structure may be destroyed by laser irradiation, and the atoms constituting the semiconductor may vaporize. For example, when the semiconductor ingot is made of a nitride semiconductor, it is known that nitrogen gas is generated at the site of the modified layer. The semiconductor wafer peeled off from the semiconductor ingot is thin. Therefore, when gas is generated inside the semiconductor ingot, one main surface of the semiconductor ingot including the peeled-off semiconductor wafer expands, and the semiconductor wafer is deformed. This specification provides a technique for suppressing deformation of a semiconductor wafer peeled off from a semiconductor ingot in a method for manufacturing a semiconductor device using a laser lift-off technique.

Means for Solving the Problems

[0005] A method for manufacturing a semiconductor device disclosed herein may include: a deformation prevention layer formation step of forming a deformation prevention layer (30) on the first main surface of a semiconductor ingot (1) having a first main surface (1a) and a second main surface (1b); a laser irradiation step of irradiating the semiconductor ingot with a laser, wherein the laser is irradiated onto a surface (3) extending to a predetermined depth within the semiconductor ingot; and a peeling step of peeling a semiconductor wafer (2) from the remaining layers of the semiconductor ingot along the surface irradiated with the laser. The type of semiconductor ingot may be any type of semiconductor ingot containing atoms that vaporize upon irradiation with the laser.

[0006] In the above manufacturing method, a deformation prevention layer is formed on the first main surface of the semiconductor ingot before the laser irradiation step. The first main surface of the semiconductor ingot is the area where the semiconductor wafer is peeled off. Therefore, even if gas is generated inside the semiconductor ingot during the laser irradiation step, deformation of the semiconductor wafer is suppressed. [Brief explanation of the drawing]

[0007] [Figure 1] This diagram shows the flow chart of the deformation prevention layer formation process, the laser irradiation process, and the peeling process in the manufacturing method of a semiconductor device. [Figure 2] This diagram schematically shows a cross-sectional view of a semiconductor ingot during the manufacturing process of a semiconductor device. [Figure 3] This diagram schematically shows a cross-sectional view of a semiconductor ingot during the manufacturing process of a semiconductor device. [Figure 4] This diagram schematically shows a cross-sectional view of a semiconductor ingot during the manufacturing process of a semiconductor device. [Figure 5] This diagram schematically shows a cross-sectional view of a semiconductor ingot during the manufacturing process of a semiconductor device. [Figure 6] This diagram schematically shows a cross-sectional view of a semiconductor ingot during the manufacturing process of a semiconductor device. [Modes for carrying out the invention]

[0008] As shown in Figure 1, the method for manufacturing a semiconductor device using the laser peeling technology disclosed herein comprises a deformation prevention layer formation step (S1), a laser irradiation step (step S2), and a peeling step (step S3). This manufacturing method peels a semiconductor wafer 2 from a semiconductor ingot 1 by performing these steps on the semiconductor ingot 1 shown in Figure 2. Multiple semiconductor devices (also called chips) are manufactured from the semiconductor wafer 2 by forming various diffusion regions and the like that which constitute electronic devices on the peeled semiconductor wafer 2.

[0009] As shown in Figure 2, the semiconductor ingot 1 has an upper surface 1a and a lower surface 1b, each extending parallel to the other in a plane. These upper surface 1a and lower surface 1b are also called the main surfaces. The semiconductor ingot 1 also has a side surface 1c that is perpendicular to the upper surface 1a and lower surface 1b and connects the upper surface 1a and lower surface 1b. The semiconductor ingot 1 is composed of a specific type of semiconductor single crystal. The semiconductor ingot 1 is not particularly limited, but may be composed of, for example, a nitride semiconductor single crystal. Specifically, the semiconductor ingot 1 may be composed of, for example, a gallium nitride (GaN) single crystal. The surface 3 extending to a predetermined depth of the semiconductor ingot 1 is, as will be described later, the surface to which the laser is irradiated, that is, the surface where multiple laser focal points converge (hereinafter referred to as the "focusing surface"). The depth of the focusing surface 3 is closer to the upper surface 1a than to the lower surface 1b of the semiconductor ingot 1. This is a semiconductor wafer 2, from which the portion of the semiconductor ingot 1 above the light-collecting surface 3 is peeled off from the semiconductor ingot 1.

[0010] As shown in Figure 3, in the deformation prevention layer formation process (step S1 in Figure 1), a deformation prevention layer 30 is formed over the entire upper surface 1a of the semiconductor ingot 1. The deformation prevention layer 30 covers the corners of the upper surface 1a of the semiconductor ingot 1 and is also formed on a part of the side surface 1c of the semiconductor ingot 1. However, the deformation prevention layer 30 is not formed on the side surface 1c of the semiconductor ingot 1 corresponding to the depth of the light-gathering surface 3. The material of the deformation prevention layer 30 is not particularly limited. The material of the deformation prevention layer 30 may be a material with a higher Young's modulus than the semiconductor ingot 1, or a material with a lower Young's modulus than the semiconductor ingot 1.

[0011] The deformation prevention layer 30 may be an organic material, taking into consideration its adhesion to the upper surface 1a of the semiconductor ingot 1. The deformation prevention layer 30 may be, for example, a resin (e.g., a thermosetting resin or an ultraviolet curing resin). Alternatively, the deformation prevention layer 30 may be a surface protection tape widely used in semiconductor manufacturing processes. The deformation prevention layer 30 may also be a ceramic, metallic, crystalline material, or a combination thereof. These materials may be directly bonded to the upper surface 1a of the semiconductor ingot 1, or they may be deposited on the upper surface 1a of the semiconductor ingot 1 using a film deposition technique (e.g., sputtering, vapor deposition, plasma deposition, or spin coating). The thickness of the deformation prevention layer 30 is not particularly limited and should be adjusted as appropriate to suppress deformation of the semiconductor ingot 1 during the laser irradiation process described later.

[0012] As shown in Figure 4, in the laser irradiation process (step S2 in Figure 1), a laser is irradiated onto a focusing surface 3 that extends to a predetermined depth in the semiconductor ingot 1. The laser is irradiated from the lower surface 1b of the semiconductor ingot 1 so as to be focused at a predetermined depth in the semiconductor ingot 1, with the lower surface 1b of the semiconductor ingot 1 exposed. The laser is a laser in a wavelength range that is transparent to the semiconductor ingot 1 (in this example, a single crystal of gallium nitride). The laser is not particularly limited, but may be a visible light laser, for example, a green laser. At the focal point, the crystal constituting the semiconductor ingot 1 (in this example, a single crystal of gallium nitride) is heated and decomposed, and a modified layer is formed. The intensity of the modified layer is lower than that of the crystal constituting the semiconductor ingot 1. Therefore, the intensity of the modified layer is lower than that of the surrounding crystal.

[0013] Nitrogen gas is generated during the process of forming a modified layer inside the semiconductor ingot 1. The light-collecting surface 3 of the semiconductor ingot 1, i.e., the location where the modified layer is formed, is close to the upper surface 1a of the semiconductor ingot 1. Therefore, when nitrogen gas is generated inside the semiconductor ingot 1, the upper surface 1a of the semiconductor ingot 1 tends to expand and deform. However, a deformation-preventing layer 30 is formed on the upper surface 1a of the semiconductor ingot 1. Therefore, even if nitrogen gas is generated inside the semiconductor ingot 1, the deformation of the upper surface 1a of the semiconductor ingot 1 is suppressed. As a result, damage to the semiconductor ingot 1 is prevented.

[0014] Furthermore, the deformation prevention layer 30 is not formed on the side surface 1c of the semiconductor ingot 1 corresponding to the depth of the light-collecting surface 3. Therefore, the altered layer formed in the laser irradiation process can be exposed on the side surface 1c of the semiconductor ingot 1. A portion of the nitrogen gas generated in the laser irradiation process can be efficiently discharged from the side surface of the semiconductor ingot 1. As a result, even if nitrogen gas is generated inside the semiconductor ingot 1, deformation of the upper surface 1a of the semiconductor ingot 1 is suppressed.

[0015] As shown in Figure 5, in the peeling process (step S3 in Figure 1), the semiconductor wafer 2 is peeled from the remaining layers of the semiconductor ingot 1 along the light-focusing surface 3 irradiated with the laser. Since the strength of the light-focusing surface 3 is reduced due to the formation of the altered layer, the semiconductor wafer 2 is peeled cleanly from the remaining layers of the semiconductor ingot 1. In this peeling process, the deformation prevention layer 30 remains on the upper surface 1a of the semiconductor ingot 1. Thus, the deformation prevention layer 30 can also function as a surface protective film in the peeling process.

[0016] A modified version of the above manufacturing method is described below.

[0017] In the above example, the laser irradiated in the laser irradiation process was irradiated from the lower surface 1b of the semiconductor ingot 1. Alternatively, the laser irradiated in the laser irradiation process may be irradiated from the upper surface 1a of the semiconductor ingot 1. In this case, the material used for the deformation prevention layer 30 can be any material that is transparent to the laser.

[0018] Furthermore, in the above example, the deformation prevention layer 30 was formed only on the upper surface 1a of the semiconductor ingot 1. Alternatively, the deformation prevention layer may also be formed on the lower surface 1b of the semiconductor ingot 1. For example, if the semiconductor ingot 1 is thin, forming deformation prevention layers on both sides of the semiconductor ingot 1 can suppress deformation of the semiconductor ingot 1 after the semiconductor wafer 2 has been peeled off. The deformation prevention layer formed on the lower surface 1b of the semiconductor ingot 1 may be made of the same material as the deformation prevention layer 30 formed on the upper surface 1a of the semiconductor ingot 1, or it may be made of a different material.

[0019] As shown in FIG. 6, the anti-deformation layer 30 may include an adhesive layer 32 and a support substrate 34. The adhesive layer 32 is made of an organic material and is not particularly limited. For example, it may be a double-sided tape commonly used in semiconductor manufacturing processes. The support substrate 34 is fixed to the upper surface 1a of the semiconductor ingot 1 via the adhesive layer 32 and is made of a material with a higher Young's modulus than that of the semiconductor ingot 1. The support substrate 34 is a flat substrate extending parallel to the main surface of the semiconductor ingot 1 and extends laterally wider than the side surface 1c of the semiconductor ingot 1. The support substrate 34 is not particularly limited and may be, for example, a glass substrate or a sapphire substrate. When an anti-deformation layer is also formed on the lower surface 1b of the semiconductor ingot 1, an anti-deformation layer made of the same material as the adhesive layer 32 and the support substrate 34 of the anti-deformation layer 30 may be used.

[0020] The anti-deformation layer 30 has a support substrate 34 with a high Young's modulus. Therefore, even if nitrogen gas is generated in the semiconductor ingot 1 during the laser irradiation process, deformation of the upper surface 1a of the semiconductor ingot 1 can be suppressed.

[0021] Hereinafter, the features of the technology disclosed in this specification will be summarized. The technical elements described below are each independent technical elements, which exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing.

[0022] (Feature 1) A method for manufacturing a semiconductor device, An anti-deformation layer forming step of forming an anti-deformation layer (30) on the first main surface of a semiconductor ingot (1) having a first main surface (1a) and a second main surface (1b); A laser irradiation step of irradiating a laser into the semiconductor ingot, wherein the laser is irradiated onto a surface (3) extending to a predetermined depth within the semiconductor ingot; A peeling step of peeling the semiconductor wafer (2) including the first main surface from the remaining layers of the semiconductor ingot along the surface irradiated with the laser; A method for manufacturing a semiconductor device, comprising:

[0023] (Feature 2) The method for manufacturing a semiconductor device according to feature 1, wherein in the laser irradiation step, the laser is irradiated from the second main surface of the semiconductor ingot while the second main surface is exposed.

[0024] (Feature 3) The method for manufacturing a semiconductor device according to feature 1 or 2, wherein the deformation prevention layer has an organic material layer.

[0025] (Feature 4) The deformation prevention layer has a support substrate (34), The method for manufacturing a semiconductor device according to any one of features 1 to 3, wherein the support substrate has a Young's modulus greater than that of the semiconductor ingot.

[0026] (Feature 5) A method for manufacturing a semiconductor device according to any one of features 1 to 4, wherein the semiconductor ingot is a nitride semiconductor.

[0027] Although embodiments have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings achieve multiple objectives simultaneously, and achieving even one of these objectives constitutes technical usefulness. [Explanation of symbols]

[0028] 1: Semiconductor ingot, 2: Semiconductor wafer, 3: Light-gathering surface, 30: Deformation prevention layer

Claims

1. A method for manufacturing a semiconductor device, A deformation prevention layer formation step in which a deformation prevention layer (30) is formed on the first main surface of a semiconductor ingot (1) having a first main surface (1a) and a second main surface (1b), A laser irradiation step in which a laser is irradiated into the semiconductor ingot, wherein the laser is irradiated onto a surface (3) extending to a predetermined depth within the semiconductor ingot, A peeling step of peeling the semiconductor wafer (2) including the first main surface from the remaining layers of the semiconductor ingot along the surface irradiated with the laser, Equipped with, The deformation prevention layer is an organic material layer, and the method is a method for manufacturing a semiconductor device.

2. The method for manufacturing a semiconductor device according to claim 1, wherein in the laser irradiation step, the laser is irradiated from the second main surface of the semiconductor ingot while the second main surface is exposed.

3. The deformation prevention layer has a support substrate (34), The method for manufacturing a semiconductor device according to claim 1, wherein the support substrate has a Young's modulus greater than that of the semiconductor ingot.

4. A method for manufacturing a semiconductor device according to any one of claims 1 to 3, wherein the semiconductor ingot is a nitride semiconductor.

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