Manufacturing method of semiconductor device

Abstract

To prevent the spread of a vertical crack when an adhesive is removed from a wafer.SOLUTION: A manufacturing method disclosed by the present specification includes a grinding step, a scribing step, a support plate separation step, a break step, and a removal step. In the grinding step, a first surface (2a) of a wafer (2) on which a plurality of semiconductor elements (3) is formed is attached to a support plate (12) through an adhesive (11), and a second surface (2b) of the wafer is ground. In the scribing step, a vertical crack (5) is formed inside the wafer along a boundary between the adjacent semiconductor elements by pressing a scribe wheel (32) against the wafer along the boundary. In the support plate separation step, the support plate is separated from the wafer while the adhesive is left. In the break step, the wafer is cleaved along the boundary by pressing a breaking bar (33) against the wafer over the adhesive along the boundary. In the removal step, the adhesive is removed from the semiconductor elements divided from the wafer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] One of the processes in the manufacturing of semiconductor devices is the step of cutting individual semiconductor elements from a wafer on which multiple semiconductor elements have been formed. Conventionally, the wafer was cut (diced) along the boundaries between adjacent semiconductor elements, but in recent years, a method called scribe and break has begun to be adopted.

[0003] This method first presses a scribe wheel (a circular plate with a thin edge) along the boundary between adjacent semiconductor elements, creating a crack inside the wafer along the boundary. Because the crack propagates in a direction perpendicular to the wafer surface, this crack is hereinafter referred to as a "vertical crack." Next, a break bar is pressed along the boundary, cleaving the wafer along the boundary. This method allows the gap between adjacent semiconductor elements on the wafer to be narrower than with conventional dicing methods. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-89622 Summary of the Invention [Problem to be solved by the invention]

[0005] In the process of forming semiconductor devices on a wafer, structures (such as trenches and electrodes) that realize the functions of the semiconductor device are formed on the surface layer of one side (first side) of the wafer, and the other side (second side) is ground. Typically, the main structures (such as trenches and gate electrodes) that realize the functions of the semiconductor device are formed first on the first side, and then the second side is ground. When grinding the second side, an adhesive is applied to the first side and the wafer is attached to a support plate. Because the main structures that realize the functions of the semiconductor device are formed on the first side, a relatively thick adhesive is applied to the first side and the wafer is attached to the support plate. The thick adhesive layer also functions as a protective layer to protect the structures on the first side. If a vertical crack is formed in the wafer and then the thick adhesive layer is peeled off, the adhesive's tackiness can generate relatively large stresses inside the wafer, causing the vertical crack to expand further and damaging the wafer. This specification provides a technology for preventing vertical cracks from spreading when removing the adhesive in a manufacturing method in which a semiconductor element is separated from a wafer by a scribe-and-break method after a process of bonding a wafer to a support plate and grinding the second surface. [Means for solving the problem]

[0006] The manufacturing method disclosed herein includes a grinding step, a scribing step, a support plate removing step, a breaking step, and a removal step. In the grinding step, a first surface (2a) of a wafer (2) on which a plurality of semiconductor elements (3) are formed is attached to a support plate (12) via an adhesive (11), and a second surface (2b) of the wafer is ground. In the scribing step, a scribe wheel (32) is pressed against the wafer along the boundary between adjacent semiconductor elements, forming a vertical crack (5) inside the wafer along the boundary. In the support plate removing step, the support plate is removed from the wafer while leaving the adhesive. In the breaking step, a break bar (33) is pressed against the wafer from above the adhesive along the boundary, cleaving the wafer along the boundary. In the removal step, the adhesive is removed from the semiconductor elements separated from the wafer.

[0007] In this manufacturing method, the adhesive on the first surface is not removed, but a break bar is pressed against the wafer from above the adhesive to cleave the wafer. The adhesive is removed after the semiconductor element is separated from the wafer. Therefore, when the adhesive is removed, the wafer has already been cleaved along the vertical crack, so the vertical crack does not spread when the adhesive is removed.

[0008] Details and further improvements of the technology disclosed in this specification are described in the following "Description of Embodiments of the Invention." [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a plan view of a wafer. [Figure 2] FIG. 1 is a diagram illustrating the grinding process. [Figure 3] This is a diagram explaining the grinding process (2). [Figure 4] FIG. 10 is a diagram illustrating a scribing step. [Figure 5] FIG. 1 is a diagram illustrating the support plate removal process. [Figure 6] FIG. 10 is a diagram illustrating the support plate removal process (2). [Figure 7] FIG. 10 is a diagram illustrating a breaking process. [Figure 8] FIG. 10 is a diagram illustrating a removal step. DETAILED DESCRIPTION OF THE INVENTION

[0010] A manufacturing method according to an embodiment will be described with reference to the drawings. FIG. 1 is a plan view of a wafer 2 on which a plurality of semiconductor elements 3 are formed in a grid pattern. In FIG. 1, the semiconductor elements 3 are schematically represented by solid-line rectangles. The reference numeral "3" is omitted from some of the solid-line rectangles. For ease of explanation, the boundaries between adjacent semiconductor elements 3, which are the dividing lines along which the wafer 2 is later divided into individual semiconductor elements 3, are referred to as scribe lines 4. In the embodiment, the scribe lines 4 are imaginary lines rather than lines actually marked on the wafer 2. The scribe lines 4 may be lines or grooves actually drawn on the wafer 2 so that they can be visually confirmed. In FIG. 1, the scribe lines 4 are represented by dashed lines. The individual semiconductor elements 3 separated from the wafer 2 correspond to semiconductor devices. The semiconductor elements 3 are elements having functions such as transistors and diodes.

[0011] The material of the wafer 2 may be any semiconductor material such as SiC or GaN, but it is preferable that the semiconductor material has a crystal plane. The wafer 2 is formed so that the crystal plane is perpendicular to the wafer surface. Furthermore, the multiple semiconductor elements 3 are formed so that the scribe lines 4 (boundaries between adjacent semiconductor elements 3) coincide with the crystal planes in a plan view of the wafer.

[0012] 2 and subsequent figures, a method for manufacturing a semiconductor device (semiconductor element 3) will be described with reference to a cross section taken along line II-II in Fig. 1. For ease of explanation, the semiconductor elements overlapping line II-II in Fig. 1 will be referred to as semiconductor elements 3a, 3b, 3c, and 3d from the left.

[0013] The manufacturing method of the embodiment includes a grinding step, a scribing step, a support plate removing step, a breaking step, and a removal step.

[0014] (Grinding Process) The grinding process will be explained with reference to Figures 2 and 3. For ease of explanation, of the two surfaces of the wafer 2, the side on which the main structures 6 of the semiconductor elements 3a, 3b, such as gates and channels, are formed on the surface will be referred to as the first surface 2a, and the opposite surface will be referred to as the second surface 2b. The wafer 2 will be thinned later, but in Figure 2, the wafer 2 is drawn thicker than in Figure 3 to illustrate the wafer 2 before thinning.

[0015] 2 and 3 (and FIG. 4, which will be described later) depict the wafer 2 with the first surface 2a facing downward. Scribe lines 4 are shown inside the wafer 2 by dashed lines. The left side of the left scribe line 4 corresponds to semiconductor element 3d, the left side of the central scribe line 4 corresponds to semiconductor element 3c, the right side of the central scribe line 4 corresponds to semiconductor element 3b, and the right side of the right scribe line 4 corresponds to semiconductor element 3a. When semiconductor elements 3a-3d are not to be distinguished from one another, they are collectively referred to as "semiconductor element 3."

[0016] In this embodiment, illustration and description of the specific internal structure of the semiconductor element 3 will be omitted. However, to facilitate understanding, in the drawings, main structures 6 (main structures among the structures necessary to realize the functions of the semiconductor element), such as channels and gate electrodes formed inside the semiconductor element 3, are hatched differently from other parts of the wafer 2. The main structures 6 are formed on the surface layer on the first surface 2a side of the wafer 2. On the second surface 2b, either nothing is formed or a simple structure such as an electrode is formed.

[0017] In the grinding process, the first surface 2a of the wafer 2 is attached to a support plate 12 via an adhesive 11, and the second surface 2b of the wafer 2 is ground with a grinding wheel 31 (see FIG. 3). The wafer 2 is thinned by grinding. In FIG. 3, the wafer 2 is thinner than in FIG. 2.

[0018] The adhesive 11 used is, for example, a silicone adhesive, and in addition to bonding the wafer 2 to the support plate 12, it also functions to protect the main structure 6 formed on the first surface 2a of the wafer 2. Therefore, the adhesive 11 is applied relatively thickly. Although not shown in the figure, various undulations are formed on the first surface 2a, including the surface of the main structure 6, and the adhesive 11 penetrates into the recesses of the undulations and adheres closely to the first surface 2a. In addition, the adhesive 11 has the property that the surface layer hardens and loses its adhesiveness when irradiated with ultraviolet light.

[0019] (Scribing Process) Following the grinding process, the scribing process is carried out. The scribing process will be explained with reference to FIG. 4. The first surface 2a of the wafer 2 is attached to a support plate 12 via an adhesive 11. In the scribing process, the wafer 2 is used while still attached to the support plate 12. In the scribing process, a scribing wheel 32 is pressed against the second surface 2b of the wafer 2 along the scribe line 4 (the boundary between adjacent semiconductor elements 3), and a vertical crack 5 is formed inside the wafer 2 along the scribe line 4.

[0020] The wafer 2 is fixed to the support plate 12 via an adhesive 11. Therefore, the wafer 2 does not move even when the scribe wheel 32 is moved along the scribe line 4. Furthermore, the adhesive 11 protects the main structure 6 even when the scribe wheel 32 is pressed strongly against the wafer 2.

[0021] The scribe wheel 32 is a disk-shaped component that is journaled on a support device (not shown). The scribe wheel 32 is moved along the scribe line 4 while being pressed against the wafer 2. During movement, the scribe wheel 32 rolls on the wafer 2 without slipping, like a tire rolling on a road surface. Although the scribe wheel 32 has a sharp peripheral edge, it does not cut the wafer 2; it is simply pressed against the wafer 2 from the second surface 2b side. As mentioned above, the scribe line 4 runs along the crystal plane of the wafer 2, and when the scribe wheel 32 is pressed hard, a vertical crack 5 is generated inside the wafer 2 along the scribe line 4. A "vertical crack" refers to a crack that propagates perpendicular to the surface of the wafer 2. In other words, the vertical crack 5 propagates along the crystal plane of the wafer 2.

[0022] (Support Plate Removing Process) The support plate removing process is carried out following the scribing process. The support plate removing process will be explained with reference to Figures 5 and 6. Note that from Figure 5 onwards, the wafer 2 is depicted with the first surface 2a facing up. Before removal, a dicing tape 13 is attached to the second surface 2b of the wafer 2, and although not shown, it is fixed to a dicing ring (Figure 5).

[0023] In the support plate removal process, the support plate 12 is removed from the wafer 2 while leaving the adhesive 11 in place. As mentioned above, the surface layer 11a of the adhesive 11 hardens when exposed to ultraviolet light, and the surface of the surface layer 11a loses its adhesive strength. The support plate 12 is made of transparent glass. Ultraviolet light is irradiated onto the adhesive 11 through the transparent support plate 12 (Figure 5). This hardens the surface layer 11a of the adhesive 11, and the surface (the surface of the surface layer 11a) loses its adhesive strength. Therefore, the support plate 12 can be easily removed from the wafer 2 (Figure 6).

[0024] A thermosetting adhesive may be used as the adhesive 11. In that case, the support plate 12 does not need to be transparent. The adhesive force of the surface layer 11a of the adhesive 11 may be lost by heating, and the support plate 12 may be removed from the adhesive 11.

[0025] (Breaking Step) Following the support plate removal step, the breaking step is carried out. The breaking step will be described with reference to Figures 7 and 8. In the breaking step, a breaking bar 33 is pressed along the scribe lines 4, and the wafer 2 is cleaved along the scribe lines 4.

[0026] 7 shows the cross section before the pressing of the break bar 33. Another protective sheet 15 is attached to the surface of the adhesive 11 (surface of the surface layer 11a) (FIG. 7).

[0027] In Figure 7, the break bar 33 pressed against the wafer 2 is depicted by an imaginary line (two-dot chain line). The break bar 33 has a length equivalent to the diameter of the wafer 2 and is pressed against the wafer 2 over the entire length of the scribe line 4. A vertical crack 5 is formed inside the wafer 2 along the scribe line 4. When the break bar 33 is pressed firmly against the wafer 2, the vertical crack 5 spreads further along the crystal plane, and the wafer 2 cleaves along the scribe line 4 (see Figure 8). In Figure 8, some traces of the vertical crack 5 are marked with the symbol "5a."

[0028] The break bar 33 is pressed against the wafer 2 from above the adhesive 11 and protective sheet 15. When the break bar 33 is pressed, the wafer 2 is cleaved, and at the same time, the adhesive 11 and protective sheet 15 are also cut along the scribe lines 4. Figure 8 shows a cross section after the break bar 33 has been pressed, in which the wafer 2 has been cleaved along the scribe lines 4, the adhesive 11 and protective sheet 15 have also been cut, and the wafer 2 has been divided into individual semiconductor elements 3a-3d.

[0029] (Removal Process) Following the breaking process, the removal process is carried out. In the removal process, the adhesive 11 is removed from the semiconductor element 3 separated from the wafer 2. FIG. 8 shows the state in which the dicing tape 13 has been peeled off from the semiconductor element 3c, and the adhesive 11 and protective sheet 15 have also been removed. The adhesive 11 is dissolved, for example, with a solvent and removed from the semiconductor element 3c. The adhesive 11 and protective sheet 15 are also removed from the other semiconductor elements 3a, 3b, and 3d.

[0030] As described above, according to the manufacturing method of the embodiment, the vertical cracks 5 are formed after the adhesive 11 is applied to the wafer 2, and the wafer 2 is separated into individual semiconductor elements 3 before the adhesive 11 is removed from the semiconductor elements 3. When the adhesive 11 is removed, the vertical cracks 5 are prevented from spreading.

[0031] Another feature of the manufacturing method of the embodiment is as follows: In the support plate removal step, the surface layer 11a of the adhesive 11 is hardened to remove the support plate 12 from the adhesive 11. The support plate 12 is easily removed, and contamination of the break bar 33 with the adhesive 11 in the breaking step is prevented (at least contamination of the break bar 33 with the adhesive 11 is reduced).

[0032] In the breaking step, a protective sheet 15 is attached to the surface of the adhesive 11, and then the break bar 33 is pressed against the wafer 2. The protective sheet 15 more effectively prevents the break bar 33 from being contaminated by the adhesive.

[0033] It should be noted that protective sheet 15 may not be necessary. In that case, in the support plate removal step, adhesive 11 may be removed from wafer 2 using strong adhesive tape. That is, adhesive tape may be attached to the surface of adhesive 11, and adhesive 11 may be peeled off from wafer 2 together with the adhesive tape.

[0034] A few points to note about the technology described in the embodiments are as follows. Neither the scribe wheel 32 nor the break bar 33 cuts (cuts) the wafer 2. The scribe 32 creates a vertical crack 5 inside the wafer 2, and the break bar 33 widens the vertical crack 5 to cleave the wafer 2. The scribe wheel 32 and the break bar 33 may be made of any material and may have any shape as long as they can achieve the above functions.

[0035] The vertical crack 5 may reach one of the first surface 2 a and the second surface 2 b of the wafer 2 .

[0036] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives alone is technically useful. [Explanation of symbols]

[0037] 2: Wafer 2a: First surface 2b: Second surface 3: 3a-3d: Semiconductor element 4: Scribe line 5: Vertical crack 6: Main structure 11: Adhesive 11a: Surface layer 12: Support plate 13: Dicing tape, 15: Protective sheet 31: Grinding wheel 32: Scribe wheel 33: Break bar

Claims

1. A method for manufacturing a semiconductor device, comprising: a grinding step in which a first surface (2a) of a wafer (2) on which a plurality of semiconductor elements (3) are formed is attached to a support plate (12) via an adhesive (11), and a second surface (2b) of the wafer is ground; a scribing step of pressing a scribe wheel (32) against the wafer along the boundary (4) between adjacent semiconductor elements to form a vertical crack (5) inside the wafer along the boundary; a support plate removing step of removing the support plate from the wafer while leaving the adhesive; a breaking step of pressing a breaking bar (33) against the wafer from above the adhesive along the boundary to cleave the wafer along the boundary; a removing step of removing the adhesive from the semiconductor element separated from the wafer; The manufacturing method comprises:

2. The manufacturing method according to claim 1, wherein in the support plate removing step, the surface layer (11a) of the adhesive is hardened to remove the support plate from the adhesive.

3. The manufacturing method according to claim 1 or 2, wherein in the breaking step, a protective sheet is attached to the surface of the adhesive before the breaking bar is pressed against the surface.

Images