Semiconductor device manufacturing method

Abstract

To reduce damage to a wafer in a scribing step even if a foreign matter enters between the wafer and a support plate.SOLUTION: The present specification discloses a manufacturing method of a semiconductor device (3). The manufacturing method includes a groove formation step, a scribing step, and a break step. In the groove formation step, a groove (11) is formed on a first surface (2a) of a wafer (2) on which a plurality of semiconductor elements (3) is formed, along a boundary (4) between the adjacent semiconductor elements. In the scribing step, a vertical crack (5) is formed inside the wafer along the boundary by attaching the wafer to a support plate (31) while the first surface faces the support plate and pressing a scribing blade (33) from a second surface side of the wafer along the boundary. In the break step, the wafer is cleaved along the boundary by pressing a breaking blade (34) against the boundary.SELECTED DRAWING: Figure 6

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 blade (a disc blade 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 blade is pressed along the boundary, cleaving the wafer along the boundary. This method allows for a narrower gap between adjacent semiconductor elements on the wafer than 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 scribing process, a scribe blade is pressed firmly against a wafer attached to a support plate. Therefore, if a foreign object is present between the back surface of the wafer and the support plate, the wafer may be pinched between the foreign object and the scribe blade, causing the wafer to be strongly compressed in an extremely localized area and potentially being damaged. This specification provides a technology that does not damage the wafer (or at least reduces damage) during the scribing process even if a foreign object is present between the wafer and the support plate. [Means for solving the problem]

[0006] The manufacturing method disclosed herein comprises a groove forming step, a scribing step, and a breaking step. In the groove forming step, grooves (11) are formed on a first surface (2a) of a wafer (2) on which a plurality of semiconductor elements (3) are formed, along the boundary (4) between adjacent semiconductor elements. In the scribing step, the wafer is attached to a support plate (31) with the first surface facing the support plate, and a scribe blade (33) is pressed against the boundary from the second surface (2b) side of the wafer, forming a vertical crack (5) inside the wafer along the boundary. In the breaking step, a break blade (34) is pressed against the boundary, and the wafer is cleaved along the boundary.

[0007] In the manufacturing method disclosed in this specification, a groove is formed on the surface (second surface) opposite to the surface (first surface) against which the scribe blade is pressed. Even if foreign matter enters directly below the boundary (the boundary between adjacent semiconductor elements) during scribing, the foreign matter enters the groove, so the wafer is not tightly pinched between the scribe blade and the foreign matter. Even if foreign matter enters between the wafer and the support plate, the wafer is not damaged (or at least the damage is reduced) during the scribing process.

[0008] The grooves described above may be formed in a process for forming a structure for realizing the function of a semiconductor element. For example, the grooves may be formed in a process for forming trenches by etching in the region where the semiconductor element will be formed. Alternatively, a silicon oxide film may be formed on the inner surface of the groove, and the silicon oxide film may be formed in a process for forming a silicon oxide film on the semiconductor element. Alternatively, the grooves may be formed in a process for forming a resin layer on the semiconductor element.

[0009] 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]

[0010] [Figure 1] FIG. 2 is a plan view of a wafer. [Figure 2] FIG. 1 is a diagram illustrating the groove forming process. [Figure 3] FIG. 2 is a diagram illustrating the groove forming process. [Figure 4] FIG. 3 is a diagram illustrating the groove forming process. [Figure 5] FIG. 4 is a diagram illustrating the groove forming process. [Figure 6] FIG. 10 is a diagram illustrating a scribing step. [Figure 7] This is a diagram explaining the breaking process (1). [Figure 8] This is a diagram explaining the breaking process (2). DETAILED DESCRIPTION OF THE INVENTION

[0011] A manufacturing method of 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 number "3" is omitted for 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 FIG. 1, the scribe lines 4 are represented by dashed dotted 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.

[0012] 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.

[0013] 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 element on the left side of line II-II in Fig. 1 will be denoted by reference numeral 3a, and the semiconductor element on the right side will be denoted by reference numeral 3b. The manufacturing method of the embodiment includes a groove forming step, a scribing step, and a breaking step.

[0014] (Groove Forming Process) The groove forming process will be described with reference to Figures 2-5. For ease of explanation, of the two surfaces of the wafer 2, the side on which the main structures of the semiconductor elements 3a and 3b, such as gates and channels, are formed on the surface layer will be referred to as the first surface 2a, and the opposite surface will be referred to as the second surface 2b.

[0015] In the cross section of wafer 2 in Figure 2, the area to the left of the dashed line on the left is semiconductor element 3a, and the area to the right of the dashed line on the right is semiconductor element 3b. The main structures (main structures among the structures necessary to realize the functions of the semiconductor element) such as channels and gate electrodes formed inside semiconductor elements 3a and 3b are not shown. The scribe line 4 mentioned above is located between semiconductor element 3a and semiconductor element 3b. In Figure 2 and subsequent figures, scribe line 4 is represented by a dashed line.

[0016] In the groove forming step, grooves 11 are formed on the first surface 2a of the wafer 2 on which multiple semiconductor elements 3 are formed, along the boundaries (scribe lines 4) between adjacent semiconductor elements 3a, 3b. FIG. 2 shows a cross section of the wafer 2 before the grooves 11 are formed. A process such as dry etching is performed on the first surface 2a of the wafer to form the grooves 11 along the scribe lines 4 (FIG. 3). The dry etching process for forming the grooves 11 may be one of the processes for creating structures (e.g., trenches) in the regions of the semiconductor elements 3a, 3b to realize the functions of the semiconductor elements. Therefore, the grooves 11 are also formed in the regions of the semiconductor elements 3a, 3b.

[0017] Next, a silicon oxide film 21 is formed on the first surface 2a (FIG. 4). Since the silicon oxide film 21 also performs one of the functions of the semiconductor elements 3a and 3b, the silicon oxide film 21 is also formed on the semiconductor elements 3a and 3b. The silicon oxide film 21 in the regions of the semiconductor elements 3a and 3b is provided to insulate the surface layers of the semiconductor elements 3a and 3b. The silicon oxide film 21 is also formed on the side and bottom surfaces of the trench 11.

[0018] Next, a resin layer 22 is formed on the silicon oxide film 21 (FIG. 5). The resin layer 22 is formed also on the semiconductor elements 3a and 3b to protect the surfaces of the semiconductor elements 3a and 3b. However, the resin layer 22 is formed only outside the grooves 11. The resin layer 22 is, for example, a polyimide or polyamide layer.

[0019] The grooves 11 thus formed on the first surface 2a of the wafer 2 have a width of approximately 10-100 microns and a depth of approximately 5-50 microns. The bottom surface of the grooves 11 is flat.

[0020] The silicon oxide film 21 and the resin layer 22 may also be formed in a process for forming a structure for realizing the function of a semiconductor element. As described above, the silicon oxide film 21 is formed on the inner surface of the groove 11, and this silicon oxide film 21 may be formed in a process for forming a silicon oxide film on the semiconductor elements 3a and 3b. Alternatively, the groove 11 is increased in depth by the resin layer 22, and this resin layer 22 may be formed in a process for forming a resin layer on the semiconductor elements 3a and 3b.

[0021] (Scribing Process) Following the groove forming process, the scribing process is carried out. The scribing process will be described with reference to FIG. 6. In the scribing process, the wafer 2 is attached to the support plate 31 with the first surface 2a facing the support plate 31. A scribe blade 33 is pressed against the second surface 2b of the wafer 2 along the scribe line 4, and a vertical crack 5 is formed inside the wafer 2 along the scribe line 4.

[0022] A fixing sheet 32 is sandwiched between the wafer 2 and the support plate 31. The fixing sheet 32 is sandwiched to prevent the wafer 2 from moving when the scribe blade 33 is moved along the scribe line 4.

[0023] The scribe blade 33 is a disk-shaped component that is axially supported on a support device (not shown). The scribe blade 33 is moved along the scribe line 4 while being pressed against the wafer 2. During movement, the scribe blade 33 rolls on the wafer 2 without slipping, like a tire rolling on a road surface. Although the peripheral edge of the scribe blade 33 is sharp, it does not cut the wafer 2; it is simply pressed against the wafer 2 from the side of the second surface 2b. As mentioned above, the scribe line 4 runs along the crystal plane of the wafer 2, and when the scribe blade 33 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.

[0024] When attaching the wafer 2 to the support plate 31 with the fixing sheet 32, there is a possibility that a foreign substance 100 such as dust may become trapped between the wafer 2 and the support plate 31 (fixing sheet 32). If the scribe blade 33 is pressed strongly against the wafer 2 with the foreign substance 100 still trapped therein, an extremely strong localized concentrated stress may be generated in the wafer 2 between the foreign substance 100 and the scribe blade 33, potentially damaging the wafer 2. However, in the manufacturing method of the embodiment, a groove 11 is formed along the scribe line 4 on the surface (first surface 2a) of the wafer 2 facing the support plate 31, and as shown in FIG. 6, the foreign substance 100 enters the groove 11. Therefore, the wafer 2 is not tightly sandwiched between the scribe blade 33 and the foreign substance 100, and the wafer 2 is not significantly damaged.

[0025] The flat bottom surface of the groove 11 also contributes to reducing damage to the wafer 2. The flat bottom surface of the groove 11 prevents the wafer 2 from being pinched tightly between the foreign matter 100 that has entered and the scribe plate 33, preventing the wafer 2 from being severely damaged. Furthermore, when the groove 11 is V-shaped, the bottom of the groove forms an acute angle, and if a foreign matter hits the bottom surface of the groove when the scribe plate 33 is pressed, there is a risk that a new crack will occur from the bottom of the V-shape of the groove.

[0026] (Breaking Process) The breaking process is carried out following the scribing process. The breaking process will be described with reference to Figures 7 and 8. In the breaking process, a break blade 34 is pressed along the scribe line 4, and the wafer 2 is cleaved along the scribe line 4. Figure 7 shows a cross section before the break blade 34 is pressed. The break blade 34 pressed against the wafer 2 is depicted by an imaginary line (two-dot chain line). Figure 8 shows a cross section after the break blade 34 is pressed, in which the wafer 2 has been cleaved along the scribe line 4 and the wafer 2 has been divided into the semiconductor element 3a side and the semiconductor element 3b side.

[0027] The break blade 34 has a length equal to the diameter of the wafer 2 and is pressed against the wafer 2 along 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 blade 34 is pressed firmly against the wafer 2, the vertical crack 5 spreads further, and the wafer 2 is cleaved along the scribe line 4 (see FIG. 8). In FIG. 8, the trace of the vertical crack 5 is denoted by the symbol "5a."

[0028] The break blade 34 is pressed against the second surface 2b of the wafer 2. That is, the break blade 34 is pressed against the bottom surface of the groove 11.

[0029] In the breaking step, the wafer 2 is temporarily removed from the support plate 31 and attached with the first surface 2a facing the support plate 31. At this time, another fixing sheet 35 is sandwiched between the wafer 2 and the support plate 31 (see FIGS. 7 and 8). The other fixing sheet 35 is used to prevent the wafer 2 from slipping off the support plate 31 when the break blade 34 is pressed against it.

[0030] As described above, according to the manufacturing method of the embodiment, grooves 11 are formed on the first surface 2a of the wafer 2 along the scribe lines 4, and the scribe blade 33 is pressed against the wafer 2 with the groove 11 side facing the support plate 31. By introducing the grooves 11, when the scribe blade 33 is pressed strongly against the wafer 2, damage caused by the foreign matter 100 being caught in the wafer 2 is not caused (at least, damage to the wafer 2 is reduced).

[0031] To reiterate, neither the scribe blade 33 nor the break blade 34 cuts (cuts) the wafer 2. The scribe blade 33 generates a vertical crack 5 inside the wafer 2, and the break blade 34 cleaves the wafer 2.

[0032] At least one or both of silicon oxide film 21 and resin layer 22 may be omitted. However, the steps of forming groove 11, forming silicon oxide film 21, and forming resin layer 22 are all steps required for manufacturing semiconductor element 3 (steps of forming a structure for realizing the functions of a semiconductor element) and can be performed simultaneously. Therefore, adding the step of forming groove 11 along scribe line 4 (and the step of forming silicon oxide film 21 / resin layer 22) to the conventional manufacturing method only increases costs slightly.

[0033] Points to note regarding the techniques described in the examples are as follows. In the manufacturing method of the examples, the break blade 34 is pressed against the first surface 2a in the breaking step. The break blade 34 may also be pressed against the second surface 2b. The scribe blade 33 and the break blade 34 may be made of any material and may have any shape as long as they achieve the above-mentioned functions.

[0034] The foreign matter 100 that has entered the groove 11 is captured by the adhesive fixing sheet 32 and is therefore removed from the wafer 2 together with the fixing sheet 32 when the fixing sheet 32 is peeled off from the wafer 2.

[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, 3b: Semiconductor element 4: Scribe line 5: Vertical crack 11: Groove 21: Silicon oxide film 22: Resin layer 31: Support plate 32, 35: Fixing sheet 33: Scribe blade 34: Break blade 100: Foreign matter

Claims

1. A method for manufacturing a semiconductor device (3), comprising: a groove forming step of forming grooves (11) along the boundaries (4) between adjacent semiconductor elements (3) on a first surface (2a) of a wafer (2) on which a plurality of semiconductor elements (3) are formed; a scribing step of attaching the wafer to a support plate (31) with the first surface facing the support plate (31) and sandwiching an adhesive fixing sheet (32) therebetween, pressing a scribe blade (33) along the boundary from the side of the second surface (2b) of the wafer, forming a vertical crack (5) inside the wafer along the boundary, and peeling off the fixing sheet from the wafer; a breaking step of pressing a break blade (34) against the wafer at the boundary to cleave the wafer along the boundary; The manufacturing method comprises:

2. The manufacturing method described in claim 1, wherein in the breaking step, the second surface of the wafer is attached to the support plate with another fixed sheet (35) sandwiched therebetween, and then the breaking blade is pressed against the wafer.

3. The manufacturing method according to claim 1 , wherein the groove is formed by a step of forming a structure for realizing the function of the semiconductor element.

4. 4. The method of claim 3, wherein the groove is formed by etching a trench in the region where the semiconductor element is to be formed.

5. 4. The manufacturing method according to claim 3, wherein a silicon oxide film (21) is formed on the inner surface of the trench, and the silicon oxide film is formed in a step of forming a silicon oxide film on the semiconductor element.

6. The manufacturing method according to claim 3 , wherein the groove is formed in the step of forming a resin layer on the semiconductor element.

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