Manufacturing method for semiconductor devices

Abstract

We propose a new technology for dividing semiconductor substrates with a metal film formed on their surface. [Solution] A method for manufacturing a semiconductor device comprises the steps of: forming a crack on the first surface side of a semiconductor substrate having a plurality of element regions by pressing a pressing member along the boundary of the element regions on the first surface side of the semiconductor substrate, the crack extending along the boundary and in the thickness direction of the semiconductor substrate; forming a metal film spanning the plurality of element regions on the first surface after the step of forming the crack; and dividing the semiconductor substrate and the metal film along the boundary by pressing a dividing member against the semiconductor substrate from the second surface side located on the back side of the first surface along the boundary after the step of forming the metal film.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a technique for dividing a semiconductor substrate having a metal film formed on its back surface in a method for manufacturing a semiconductor device. In this manufacturing method, first, a dividing groove is formed along a dividing line on the surface of a semiconductor substrate having a metal film formed on its back surface by plasma etching. The dividing groove is formed while leaving a predetermined remaining amount that does not reach the metal film from the surface. Then, by applying an external force from the surface of the semiconductor substrate along the dividing line, the remaining amount existing between the dividing groove and the metal film is divided. In Patent Document 1, the metal film is divided by the impact when the remaining amount is divided.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, in order to form a dividing groove while leaving a predetermined remaining amount, it is necessary to accurately control the depth of the dividing groove. Also, in Patent Document 1, since plasma etching or the like is used when forming the dividing groove, the manufacturing cost is high. In this specification, a new technique for dividing a semiconductor substrate having a metal film formed on its surface is proposed.

Means for Solving the Problems

[0005] A method for manufacturing a semiconductor device disclosed herein comprises the steps of: forming a crack (5) in a semiconductor substrate (2) having a plurality of element regions (3) by pressing a pressing member (32) against a first surface (2a) of the semiconductor substrate (2) along the boundary (4) of the element regions, thereby forming a crack (5) in the semiconductor substrate that extends along the boundary and in the thickness direction of the semiconductor substrate; forming a metal film (8) on the first surface that spans the plurality of element regions after the step of forming the crack; and forming a dividing member (33) against the semiconductor substrate from the second surface (2b) located on the back side of the first surface, along the boundary, thereby dividing the semiconductor substrate and the metal film along the boundary, after the step of forming the metal film.

[0006] In this manufacturing method, first, a pressing member is pressed against the first surface of the semiconductor substrate to form a crack in the semiconductor substrate. The crack is formed from the first surface side. Then, a metal film is formed on the first surface, and a dividing member is pressed against it from the second surface side. Since the crack is formed on the first surface side of the semiconductor substrate, it is far from the tip of the dividing member. Therefore, when the dividing member is pressed against the semiconductor substrate from the second surface side, a force is applied in a direction that splits the crack and pulls adjacent regions apart through the crack. As a result, the crack extends in the thickness direction of the semiconductor substrate. This divides the semiconductor substrate along the boundary of the element region. Also, similar to the adjacent regions through the crack in the semiconductor substrate, a force is applied in a direction that pulls adjacent regions across the crack in the metal film apart, and the metal film is also divided as adjacent regions across the crack are pulled apart. Thus, in the above manufacturing method, the metal film can be divided together with the semiconductor substrate by a simple process of pressing a pressing member and a dividing member against the semiconductor substrate. Furthermore, since cracks are formed in advance on the first surface side of the semiconductor substrate before forming the metal film on the first surface, both the semiconductor substrate and the metal film can be separated in a single step of pressing the dividing member against the second surface side. [Brief explanation of the drawing]

[0007] [Figure 1] Plan view of a semiconductor substrate. [Figure 2] A diagram illustrating the process of attaching the support plate. [Figure 3] A diagram illustrating the grinding process. [Figure 4] A diagram illustrating the crack formation process. [Figure 5] A diagram illustrating how cracks are formed. [Figure 6] Scanning electron microscope image of a cross-section of a semiconductor substrate where cracks have formed. [Figure 7] A diagram illustrating the metal film formation process. [Figure 8] A diagram illustrating the process of applying dicing tape. [Figure 9] A diagram illustrating the support plate removal process. [Figure 10] A diagram illustrating the protective coating process. [Figure 11] A diagram illustrating the division process. [Figure 12] A diagram illustrating the pickup process. [Modes for carrying out the invention]

[0008] An example manufacturing method disclosed herein may further include a step of attaching a support plate to the second surface before the step of forming the crack, and a step of peeling the support plate from the second surface after the step of forming the metal film and before the step of dividing.

[0009] In this configuration, a support plate is attached to the semiconductor substrate, and cracks are formed in the semiconductor substrate. By constructing the support plate from a hard material, cracks can be formed in the semiconductor substrate with a relatively low load when the pressing member is pressed against the semiconductor substrate.

[0010] In an example manufacturing method disclosed in this specification, the pressing member may be a scribing wheel, and pressing the pressing member may be rolling the scribing wheel. In the step of forming the crack, a scribe line with the crack extending in the thickness direction of the semiconductor substrate may be formed along the boundary on the first surface.

[0011] With such a configuration, by pivotally supporting the scribing wheel in a rotatable manner as a disc shape (ring shape), the scribing wheel can be rolled to easily form a crack along the boundary of the element region.

[0012] In an example manufacturing method disclosed in this specification, after the step of forming the metal film and before the step of peeling, a step of attaching a dicing tape to the surface of the metal film may be further provided.

[0013] With such a configuration, in the state where the dicing tape is attached, the semiconductor substrate and the metal film are divided. Since the semiconductor substrate (metal film) is fixed to the dicing tape, when pressing a dividing member against the semiconductor substrate, displacement of the semiconductor substrate can be suppressed, and scattering of the obtained semiconductor devices (divided semiconductor substrates) can be prevented.

[0014] In an example manufacturing method disclosed in this specification, before the step of dividing, a step of covering the second surface with a protective member may be further provided. In the step of dividing, the dividing member may be pressed along the boundary from the second surface side through the protective member.

[0015] With such a configuration, the dividing member is pressed against the semiconductor substrate in a state where the second surface is covered with the protective member. Since the second surface is protected by the protective member, damage to the second surface by the dividing member can be prevented.

[0016] (Example) The manufacturing method of the embodiment will be described with reference to the drawings. FIG. 1 is a plan view of a semiconductor substrate 2 in which a plurality of element regions 3 are formed in a matrix. In FIG. 1, each element region 3 is schematically shown by a solid line. For convenience of explanation, a line that is the boundary between adjacent element regions 3 and becomes the edge of an individual element region (semiconductor device) obtained by division when the semiconductor substrate 2 is later divided into individual element regions 3 is referred to as a division planned line 4. The division planned line 4 is a virtual line, not a line actually drawn on the semiconductor substrate 2. The division planned line 4 may be a line or groove actually drawn on the semiconductor substrate 2 so as to be visible. In each element region 3, a semiconductor element having functions such as a transistor and a diode is formed.

[0017] The semiconductor substrate 2 is made of SiC (silicon carbide). Note that the semiconductor substrate 2 may be made of other semiconductor materials such as Si (silicon) and GaN (gallium nitride). As shown in FIG. 2 and the like, the semiconductor substrate 2 has a first surface 2a and a second surface 2b located on the back side of the first surface 2a. On the second surface 2b of the semiconductor substrate 2, main structures 6 of semiconductor elements such as gates and channels are formed.

[0018] The manufacturing method of the embodiment includes a support plate attachment step, a crack formation step, a metal film formation step, a dicing tape attachment step, a support plate peeling step, a protective member coating step, and a division step.

[0019] (Support plate attachment step) In the support plate attachment process, as shown in Figure 2, a support plate 12 is attached to the second surface 2b of the semiconductor substrate 2. The support plate 12 is attached to the second surface 2b via an adhesive 11. The support plate 12 is made of, for example, glass. The adhesive 11 is, for example, a silicon-based adhesive, and in addition to the function of bonding the semiconductor substrate 2 to the support plate 12, it also has the function of protecting the main structure 6 formed on the second surface 2b of the semiconductor substrate 2. Therefore, the adhesive 11 is applied so that its thickness is greater than the thickness of the main structure 6. After that, as shown in Figure 3, the first surface 2a of the semiconductor substrate 2 is ground with a grinding wheel 31 as needed. This thins the semiconductor substrate 2.

[0020] (Crack formation process) Next, the crack formation process shown in Figure 4 is carried out. In the crack formation process, a scribe line with a crack 5 is formed on the semiconductor substrate 2 by pressing a scribing wheel 32 against the first surface 2a of the semiconductor substrate 2 attached to the support plate 12. The scribing wheel 32 is a disc-shaped (annular) member and is rotatably supported by a support device (not shown). Here, the scribing wheel 32 is moved (scanned) along the planned division line 4 while being pressed against the first surface 2a of the semiconductor substrate 2. As the scribing wheel 32 moves along the planned division line 4, it rolls (moves) on the first surface 2a of the semiconductor substrate 2 like a tire rolling on a road surface. The peripheral part of the scribing wheel 32 is sharp, and it forms a line (scribe line) on the first surface 2a of the semiconductor substrate 2 along the planned division line 4, indicating plastic deformation of the semiconductor substrate 2. In this embodiment, the scribing wheel 32 is pressed against the first surface 2a with a load of approximately 2.0 N. As shown in Figure 5, when the first surface 2a is pressed by the scribing wheel 32, compressive stress is generated in the surface region R of the first surface 2a inside the semiconductor substrate 2. The compressive stress is generated isotropically, starting from the point of pressure by the scribing wheel 32 (the point of contact between the periphery of the scribing wheel 32 and the first surface 2a), as shown by arrow 20. A scribe line is formed at the point of pressure by the scribing wheel 32, while tensile stress is generated inside the semiconductor substrate 2 directly below the region where compressive stress is generated. The tensile stress is generated directly below the region where compressive stress is generated, along the first surface 2a of the semiconductor substrate 2, and away from the planned division line 4, as shown by arrow 22. This tensile stress causes a crack 5 to be formed inside the semiconductor substrate 2, extending in the thickness direction of the semiconductor substrate 2. Here, by pressing the scribing wheel 32 against the first surface 2a and moving it along the planned division line 4, a crack 5 is formed along the boundary of adjacent element regions 3 and extending in the thickness direction of the semiconductor substrate 2. Crack 5 is formed near the surface layer of the first surface 2a of the semiconductor substrate 2.Generally, compressive stress suppresses crack formation and extension. Therefore, cracks 5 are formed so as to extend from outside the region where compressive stress occurs at the point of pressure by the scribing wheel 32 on the first surface 2a of the semiconductor substrate 2 to the region where tensile stress occurs directly below the region where compressive stress occurs. The scribing wheel 32 is an example of a "pressing member".

[0021] Figure 6 is a scanning electron microscope image of a cross-section of the semiconductor substrate 2 after crack 5 has been formed by the scribing wheel 32. Figure 6(a) is a view of the cross-section of the semiconductor substrate 2 near the first surface 2a, seen from an oblique angle above, and Figure 6(b) is a cross-sectional view of the semiconductor substrate 2 near the first surface 2a. As shown in Figure 6, it can be seen that by pressing the scribing wheel 32 along the planned division line 4, crack 5 is formed on the first surface 2a side of the semiconductor substrate 2 along the boundary of the element region 3. Also, as shown in Figure 6(a), a slight indentation of the scribe line is observed on the first surface 2a of the semiconductor substrate 2 due to the plastic deformation of the semiconductor substrate 2 by the scribing wheel 32. In Figure 6, the depth of crack 5 in the thickness direction of the semiconductor substrate 2 is approximately 6 μm.

[0022] (Metal film formation process) Next, the metal film formation process shown in Figure 7 is carried out. In the metal film formation process, a metal film 8 is formed on the first surface 2a of the semiconductor substrate 2. The materials constituting the metal film 8 are not particularly limited, but for example, it is a multilayer film made of titanium, nickel, and gold. The metal film 8 is formed to cover substantially the entire area of ​​the first surface 2a. That is, the metal film 8 is formed on the first surface 2a so as to span multiple element regions 3. The metal film 8 functions as an electrode in the completed semiconductor device.

[0023] (Dicing tape application process) Next, the dicing tape application process shown in Figure 8 is carried out. In the dicing tape application process, the dicing tape 13 is applied to the surface of the metal film 8. The dicing tape 13 is applied so as to cover almost the entire surface of the metal film 8. The dicing tape 13 is fixed to a dicing frame (not shown). Note that in Figure 8 and subsequent figures, the semiconductor substrate 2 is depicted with the second surface 2b facing upwards.

[0024] (Support plate removal process) Next, the support plate peeling process shown in Figure 9 is performed. In the support plate peeling process, the support plate 12 and adhesive 11 are peeled off from the second surface 2b of the semiconductor substrate 2. Here, for example, the adhesive 11 is dissolved with a solvent, thereby peeling the support plate 12 together with the adhesive 11 from the second surface 2b. As a result, the semiconductor substrate 2 is supported by the dicing tape 13.

[0025] (Protective coating process) Next, the protective member coating process shown in Figure 10 is carried out. In the protective member coating process, the protective member 15 is attached so as to span the surface of each main structure 6 of each element region 3 of the semiconductor substrate 2, thereby covering the second surface 2b of the semiconductor substrate 2 with the protective member 15. The material of the protective member 15 is not particularly limited, but for example, resin can be used. By coating with the protective member 15, the second surface 2b of the semiconductor substrate 2 is protected in subsequent processes such as the splitting process.

[0026] (splitting process) Next, the splitting process shown in Figure 11 is carried out. In the splitting process, the break plate 33 is pressed along the planned splitting line 4 (crack 5 formed in the crack formation process), and the semiconductor substrate 2 is split along the planned splitting line 4 (along the boundary of the element region 3). Here, first, the semiconductor substrate 2 is placed on two support bases 34. The two support bases 34 are spaced apart. When the semiconductor substrate 2 is placed on the support bases 34, the semiconductor substrate 2 is placed so that the spacing is located below the position to be split (the position where the break plate 33 is pressed). After that, the break plate 33 is pressed against the second surface 2b of the semiconductor substrate 2 via the protective member 15. The break plate 33 is a plate-shaped member, and its lower end (the edge pressed against the second surface 2b) is ridge-shaped (sharp blade-shaped), but it is pressed against the semiconductor substrate 2 without cutting it.

[0027] Since there is no support base 34 below the break plate 33 (there is space between the two support bases 34), when the break plate 33 is pressed against the second surface 2b, the semiconductor substrate 2 bends so that it fits into the space between the two support bases 34. Here, the crack 5 is formed on the first surface 2a side of the semiconductor substrate 2. Therefore, when the break plate 33 is pressed against the semiconductor substrate 2 from the second surface 2b side, the semiconductor substrate 2 bends around the pressed portion (line) as an axis, and on the first surface 2a side, a force is applied in a direction that pulls the two element regions 3 adjacent to the division position away from the crack 5. Also, as described above, tensile stress is applied around the crack 5. Therefore, when the break plate 33 is pressed against the second surface 2b, the crack 5 extends in the thickness direction of the semiconductor substrate 2, and the semiconductor substrate 2 is divided along the planned division line 4. Furthermore, since the metal film 8 is formed on the first surface 2a of the semiconductor substrate 2, a force is applied to the metal film 8 in a direction that pulls the two element regions 3 adjacent to the division position apart, causing the metal film 8 to deform and be divided. Alternatively, instead of the two support bases 34, the entire first surface 2a of the semiconductor substrate 2 may be supported by a single elastic support plate (or one or more support bases via a single elastic support plate). In this case, although the elastic support plate is located below the break plate 33, when the semiconductor substrate 2 flexes, the elastic support plate deforms in accordance with the flexing of the semiconductor substrate 2. Therefore, when the break plate 33 is pressed against the second surface 2b, a force is applied to the crack 5 in a direction that pulls the two element regions 3 adjacent to the division position apart, similar to the case where it is supported by two support bases 34 (when there are no support bases 34 located below the break plate 33). The break plate 33 is an example of a "dividing member".

[0028] In the splitting process, the process of pressing the break plate 33 described above against the second surface 2b is repeatedly performed along each planned splitting line 4. This allows the semiconductor substrate 2 and the metal film 8 to be split along the boundary of each element region 3. Subsequently, as shown in Figure 12, the individualized element regions 3 and metal film 8 are peeled off from the dicing tape 13. When peeling the individualized element regions 3 and metal film 8 from the dicing tape 13, the dicing tape 13 is expanded to separate the individualized element regions 3 and metal film 8 from each other before peeling. This completes multiple semiconductor devices with metal films 8 (electrodes) formed on their surfaces.

[0029] As described above, in this embodiment, first, a crack 5 is formed on the first surface 2a side of the semiconductor substrate 2 by pressing the scribing wheel 32 against the first surface 2a of the semiconductor substrate 2. Since the crack 5 is formed on the first surface 2a side of the semiconductor substrate 2, when the break plate 33 is pressed against it from the second surface 2b side, the semiconductor substrate 2 bends along the crack 5. As a result, a force is applied along the crack 5 from the first surface 2a side in a direction that folds the semiconductor substrate 2 apart. Consequently, the crack 5 extends in the thickness direction of the semiconductor substrate 2, and the semiconductor substrate 2 can be easily divided along the boundary of the element region 3. Furthermore, since the metal film 8 is formed on the first surface 2a of the semiconductor substrate 2, a force is also applied to the metal film 8 on both sides of the crack 5 in a direction that pulls the metal film 8 apart, causing the metal film 8 to deform and be easily divided. Thus, in this embodiment, the metal film 8 can be divided together with the semiconductor substrate 2 by a simple process of pressing the scribing wheel 32 and the break plate 33 against the semiconductor substrate 2.

[0030] Furthermore, in this embodiment, a crack 5 is formed in advance on the first surface 2a side of the semiconductor substrate 2 before forming the metal film 8 on the first surface 2a. Therefore, both the semiconductor substrate 2 and the metal film 8 can be separated in a single step of pressing the break plate 33 from the second surface 2b side. In this embodiment, the crack 5 is formed on the first surface 2a side of the semiconductor substrate 2 before forming the metal film 8 on the first surface 2a. Therefore, compared to the case where the scribing wheel 32 is pressed against the first surface 2a via the metal film 8 to form the crack 5, the crack 5 can be formed with a lower load, thus reducing damage to the semiconductor substrate 2. Also, compared to the case where the scribing wheel is pressed against the second surface 2b of the semiconductor substrate 2 to form the crack, damage to the boundary portion between element regions on the second surface 2b (the peripheral portion of the resulting semiconductor device) can be reduced.

[0031] In this embodiment, a support plate 12 made of glass is attached to the semiconductor substrate 2, and a crack 5 is formed on the first surface side of the semiconductor substrate 2. Since the support plate 12 is made of a relatively hard material, a crack 5 can be formed on the first surface side of the semiconductor substrate 2 with a relatively low load when the scribing wheel 32 is pressed against the semiconductor substrate 2.

[0032] In this embodiment, the semiconductor substrate 2 and the metal film 8 are separated while the dicing tape 13 is attached. Since the semiconductor substrate 2 (metal film 8) is fixed to the dicing tape 13, when the break plate 33 is pressed against the semiconductor substrate 2, displacement of the semiconductor substrate 2 can be suppressed, and scattering of the resulting semiconductor device can be prevented.

[0033] In this embodiment, the break plate 33 is pressed against the semiconductor substrate 2 while the second surface 2b is covered by the protective member 15. Since the second surface 2b is protected by the protective member 15, it is possible to prevent the break plate 33 from damaging the second surface 2b.

[0034] In the above-described embodiment, the support plate attachment step, the dicing tape attachment step, and the protective member covering step may be omitted.

[0035] The configurations of the manufacturing methods disclosed herein are listed below. (Composition 1) A method for manufacturing a semiconductor device, A step of forming a crack in a semiconductor substrate that extends along the boundary and in the thickness direction of the semiconductor substrate by pressing a pressing member against the first surface of a semiconductor substrate having multiple element regions along the boundary of the element regions, The step of forming the cracks is followed by the step of forming a metal film on the first surface that spans the plurality of element regions, A step of separating the semiconductor substrate and the metal film along the boundary by pressing a dividing member against the semiconductor substrate along the boundary from the second surface side located on the back side of the first surface, after the step of forming the metal film, A manufacturing method that includes the following features. (Configuration 2) The pressing member is a scribing wheel, Pressing the aforementioned pressing member against the surface causes the scribing wheel to roll. The manufacturing method according to configuration 1, wherein in the step of forming the crack, a scribe line is formed on the first surface along the boundary, accompanied by the crack extending in the thickness direction of the semiconductor substrate. (Composition 3) Prior to the step of forming the crack, there is a step of attaching a support plate (12) to the second surface, After the step of forming the metal film, and before the step of dividing, a step of peeling the support plate from the second surface, A manufacturing method according to configuration 1 or 2, further comprising: (Composition 4) The manufacturing method according to configuration 3, further comprising the step of attaching a dicing tape (13) to the surface of the metal film after the step of forming the metal film and before the step of peeling it off. (Composition 5) The process further includes, before the division step, covering the second surface with a protective member (15), The manufacturing method according to any one of configurations 1 to 4, wherein in the step of dividing, the dividing member is pressed against the boundary from the second surface side via the protective member.

[0036] 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]

[0037] 2: Semiconductor substrate, 2a: First surface, 2b: Second surface, 3: Element region, 4: Planned division line, 5: Crack, 6: Main structure, 8: Metal film, 11: Adhesive, 12: Support plate, 13: Dicing tape, 15: Protective material, 32: Scribing wheel, 33: Break plate

Claims

1. A method for manufacturing a semiconductor device, A step of forming a crack (5) in a semiconductor substrate (2) that extends along the boundary and in the thickness direction of the semiconductor substrate by pressing a pressing member (32) against the first surface (2a) of a semiconductor substrate (2) having a plurality of element regions (3) along the boundary (4) of the element regions, The step of forming the cracks is followed by the step of forming a metal film (8) on the first surface that spans the plurality of element regions, After the step of forming the metal film, a step of separating the semiconductor substrate and the metal film along the boundary is performed by pressing the dividing member (33) against the semiconductor substrate along the boundary from the second surface (2b) located on the back side of the first surface, A manufacturing method that includes the following features.

2. The pressing member is a scribing wheel, Pressing the aforementioned pressing member against the surface causes the scribing wheel to roll. The manufacturing method according to claim 1, wherein in the step of forming the crack, a scribe line is formed on the first surface along the boundary, accompanied by the crack extending in the thickness direction of the semiconductor substrate.

3. Prior to the step of forming the crack, there is a step of attaching a support plate (12) to the second surface, After the step of forming the metal film, and before the step of dividing, a step of peeling the support plate from the second surface, The manufacturing method according to claim 1, further comprising:

4. The manufacturing method according to claim 3, further comprising the step of attaching a dicing tape (13) to the surface of the metal film after the step of forming the metal film and before the step of peeling it off.

5. The process further includes, before the division step, covering the second surface with a protective member (15), The manufacturing method according to any one of claims 1 to 4, wherein in the step of dividing, the dividing member is pressed against the boundary from the second surface side via the protective member.

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