Mask formation method

Abstract

To provide a mask formation method that can efficiently arrange a mask of a size corresponding to chips divided by cutting for each chip.SOLUTION: A method includes a resin film laying step of laying a resin film 20 as a mask on the upper surface of a substrate 10, a groove forming step of positioning a cutting blade 35 on the surface of the resin film 20 corresponding to planned division lines 14 to form grooves 100 of a depth that does not reach the planned division lines 14, and an exposure step of performing plasma etching on the surface of the resin film 20 with gas that etches the resin film 20 to remove the bottoms of the grooves 100 and expose the planned division lines 14.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for forming a mask used when metal plating is performed along the planned dividing lines of a substrate having an upper surface to be divided into individual chips along the planned dividing lines. [Background technology]

[0002] Wafers, on the surface of which multiple devices such as ICs and LSIs are formed and partitioned along planned dividing lines, are divided into individual device chips by a cutting machine equipped with a rotatable cutting blade, and these are used in electrical equipment such as mobile phones and personal computers.

[0003] Furthermore, for example, when dividing a ceramic substrate into individual chips, a cutting device is used (see, for example, Patent Document 1), but before dividing, a grid-like gold-tin (AuSn) plating having a width exceeding the thickness of the cutting blade is applied along the intended dividing line. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-039906 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in order to perform AuSn plating along the planned dividing lines, a mask of a size corresponding to the chip must be provided for each chip, which is an unbearable hassle.

[0006] The present invention has been made in consideration of the above facts, and its main technical object is to provide a method for forming a mask that can efficiently arrange a mask of a size corresponding to the chips to be divided by cutting processing for each chip, thereby solving the problem of unbearable hassle. [Means for solving the problem]

[0007] In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a method for forming a mask used when applying metal plating to a substrate having an upper surface that will be divided into individual chips by the planned dividing lines, the method including: a resin film laying step for laying a resin film that will serve as a mask on the upper surface of the substrate; a groove forming step for positioning a cutting blade on the surface of the resin film corresponding to the planned dividing lines to form grooves that are deep enough not to reach the planned dividing lines; and an exposure step for performing plasma etching on the surface of the resin film with a gas that etches the resin film to remove the bottom of the groove and expose the planned dividing lines.

[0008] In the resin film laying step, the resin film is preferably a liquid resin or a sheet. Furthermore, in the resin film laying step, the liquid resin is preferably an epoxy resin, and the sheet is preferably a thermocompression-bonded sheet that is bonded by heating. Furthermore, in the exposing step, the gas that etches the resin film is preferably oxygen. [Effects of the Invention]

[0009] The method for forming a mask according to the present invention is a method for forming a mask used in applying metal plating to a substrate having an upper surface to be divided into individual chips along the division lines, the method comprising the steps of: laying a resin film to serve as a mask on the upper surface of the substrate; positioning a cutting blade on the surface of the resin film to correspond to the division lines and forming grooves of a depth that does not reach the division lines; and exposing the division lines by plasma etching the surface of the resin film with a gas that etches the resin film to remove the bottoms of the grooves, thereby eliminating the need for a mask of a size corresponding to each chip to be divided on the substrate, which is troublesome. Furthermore, while there is a risk of damaging the substrate if a resin film that functions as a mask is laid on the substrate and then grooves are formed in the resin film using a cutting blade to expose the division lines, the present invention achieves the effect of not damaging the division lines on the substrate by forming grooves of a depth that does not reach the division lines and then exposing the division lines by plasma etching. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a perspective view of a substrate on which a mask is formed in the present embodiment. [Figure 2] FIG. 1A is a perspective view showing a form in which a resin film is formed on the upper surface of a substrate using a liquid resin, and FIG. 1B is a perspective view showing a form in which a resin film is formed by attaching a sheet. [Figure 3] FIG. 1 is a perspective view of a substrate having a resin film formed on its surface. [Figure 4] (a) is an oblique view showing how a substrate is held on a chuck table of a cutting device; (b) is an oblique view showing how a groove forming process is carried out; (c) is an enlarged partial cross-sectional view showing a groove formed by the groove forming process. [Figure 5] FIG. 10 is a perspective view of a substrate on which grooves are formed by a groove forming step. [Figure 6] FIG. 10 is an enlarged cross-sectional view of a portion of the substrate in which the dividing lines are exposed by an exposing step. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a method for forming a mask according to the present invention will be described in detail with reference to the accompanying drawings.

[0012] FIG. 1 shows a substrate 10 on which a mask is formed by the mask forming method of this embodiment, and the substrate 10 is a ceramic substrate. As shown in the figure, the substrate 10 is a rectangular substrate on whose surface 10a a plurality of regions 12 are partitioned by planned division lines 14. The planned division lines 14 are formed in a grid pattern by division lines 14 in a predetermined direction and planned division lines 14 in a direction perpendicular to the predetermined direction. Note that the planned division lines in the present invention are not necessarily limited to those clearly shown in the figure, but also include lines that serve as a reference for division when the substrate 10 is divided into individual chips in a subsequent division process (description omitted), and also include lines that are not clearly shown on the surface 10a.

[0013] The method for forming a mask according to this embodiment will be described below using the above substrate 10 as an example.

[0014] (Resin membrane laying process) When carrying out the mask forming method of this embodiment, first, a resin film laying step is carried out in which a resin film that will serve as a mask is laid on the upper surface (surface 10a) of the substrate 10. The resin film laid on the surface 10a of the substrate 10 in the resin film laying step can be formed, for example, by applying a liquid resin or by attaching a resin sheet.

[0015] When forming the resin film using a liquid resin, for example, the substrate 10 is positioned directly below the liquid resin supply means 18 shown in FIG. 2( a), held on a table (not shown). A predetermined amount of liquid resin 19, such as an epoxy resin, is dripped onto the surface 10a of the substrate 10 from the supply nozzle 18a of the liquid resin supply means 18, and the liquid resin 19 is spread to a uniform thickness on the surface 10a of the substrate 10. At this time, it is preferable to rotate the table holding the substrate 10. After dripping the liquid resin 19, ultraviolet (UV) rays are irradiated onto the liquid resin 19 spread on the surface 10a of the substrate 10 using an ultraviolet irradiation means (not shown) to solidify the liquid resin 19. This allows a resin film of uniform thickness to be formed on the surface 10a of the substrate 10. The liquid resin 19 is not limited to epoxy resin but may be acrylic resin. Furthermore, it is not limited to resins that solidify upon UV irradiation but may be resins that solidify over time.

[0016] When the resin film is formed using a resin sheet in the resin film laying step, for example, a sheet 20 as shown in FIG. 2(b) is prepared. The sheet 20 is formed to a size sufficient to cover the surface 10a of the substrate 10, and is a thermocompression sheet that softens and exerts adhesive strength when heated to near its melting temperature, without forming an adhesive layer made of glue or the like on the attachment surface. The sheet 20 can be selected from, for example, a polyolefin-based sheet or a polyester-based sheet, and is preferably selected from a polyolefin-based sheet. When selecting from the polyolefin-based sheets, a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet is preferred. When a polyethylene sheet is selected as the sheet 20 to be thermocompression-bonded, the heating temperature is 120°C to 140°C, when a polypropylene sheet is selected, the heating temperature is 160°C to 180°C, and when a polystyrene sheet is selected, the heating temperature is 220°C to 240°C.

[0017] Once the sheet 20 is prepared, it is placed on the surface 10a of the substrate 10, as shown in FIG. 2(b). Next, using a heating roller or the like (not shown), the sheet 20 is pressed from above while being heated to the above-mentioned heating temperature, so that it adheres to the entire surface 10a of the substrate 10 and is thermocompression bonded. This generates adhesive force in the sheet 20, and the substrate 10 and the sheet 20 are integrated as shown in FIG. 3. It is more preferable to perform the thermocompression bonding while placing the substrate 10 in a reduced pressure atmosphere, as this allows the sheet 20 and the substrate 10 to be more reliably adhered to each other. Note that in this embodiment, an example will be described in which the sheet 20 is laid as a resin film on the surface 10a of the substrate 10 in the resin film laying step (in the following description, the sheet 20 laid on the substrate 10 is referred to as the resin film 20), and then a mask is formed.

[0018] (Groove formation process) After the resin film laying step has been carried out as described above, a groove forming step is carried out in which a cutting blade is positioned on the surface of the resin film 20 in correspondence with the above-mentioned planned division lines 14, and grooves are formed to a depth that does not reach the planned division lines 14. When carrying out this groove forming step, the work is transported to a cutting device 30 (only a portion of which is shown) shown in Figures 4(a) and (b).

[0019] The cutting device 30 includes a chuck table 31 shown in Fig. 4(a) and cutting means 32 shown in Fig. 4(b). The chuck table 31 has a holding surface 31a whose dimensions correspond to the substrate 10 and is formed in a rectangular shape. The holding surface 31a is formed of a breathable material and is connected to a suction means (not shown) so that negative pressure can be generated on the holding surface 31a. The cutting device 30 includes an X-axis moving means (not shown) that moves the chuck table 31 in the X-axis direction indicated by the arrow X in Fig. 4(b), and the chuck table 31 is configured to be freely rotatable. The cutting means 32 comprises a spindle housing 33 arranged along the Y-axis direction indicated by the arrow Y in Figure 4(b), a spindle 34 rotatably held in the spindle housing 33, an annular cutting blade 35 held at the tip of the spindle 34, a blade cover 36 that covers the cutting blade 35, and a cutting water supply nozzle 37 arranged on the blade cover 36 and connected to a cutting water supply means (not shown) that supplies cutting water to the cutting location during cutting processing.

[0020] The cutting means 32 is equipped with a Y-axis moving means (not shown) that indexes and feeds the cutting blade 35 in the Y-axis direction, and also with a Z-axis moving means (not shown) that feeds the cutting means 32 in the Z-axis direction indicated by the arrow Z in the figure. The spindle 34 is driven to rotate by a spindle motor (not shown). The cutting blade 35 used in this groove forming step is thicker (e.g., 50 μm) than the cutting blade (e.g., 30 μm) used when cutting along the planned division lines 14 of the substrate 10 (described later) and dividing it into individual ceramic chips.

[0021] To perform the groove forming process, as shown in FIG. 4(a), the substrate 10 is first placed on the chuck table 31 of the cutting device 30 with the front surface 10a facing upward and the back surface 10b facing downward. A suction device (not shown) is then activated to generate negative pressure on the holding surface 31a, thereby suction-holding the substrate 10. Next, an alignment device (not shown) captures an image of the substrate 10, aligns the predetermined division line 14 of the substrate 10 in the X-axis direction, and aligns it with the cutting blade 35. At this time, the surface height of the resin film 20 laid on the front surface 10a of the substrate 10 is also detected. Next, the Y-axis moving device is activated to position the cutting blade 35, which is rotating at high speed in the direction indicated by arrow R1, on the predetermined division line 14 aligned in the X-axis direction. The cutting blade 35 is then cut into the resin film 20 from the side of the substrate 10, and the chuck table is moved in the X-axis direction to form a groove 100 as shown in FIG. 4(c).

[0022] Here, the grooves 100 formed by the groove forming step are formed corresponding to the dividing lines 14, and as shown in FIG. 4(c), they are formed to a depth that does not reach the dividing lines 14 of the substrate 10, leaving a resin film 20 with a thickness of, for example, 10 to 20 μm at the bottom. Then, the cutting blade 35 of the cutting means 32 is indexed and fed onto a dividing line 14 adjacent in the Y-axis direction to the dividing line 14 on which the groove 100 is formed as described above, but on which no groove 100 is formed, to form grooves 100 that do not reach the dividing lines 14 of the substrate 10, in the same manner as described above. By repeating this cutting process, the grooves 100 are formed along all the dividing lines 14 along the X-axis direction. Next, the chuck table 31 is rotated 90 degrees, and the direction perpendicular to the direction in which the grooves 100 were previously formed is aligned with the X-axis direction. The above-mentioned cutting process on the resin film 20 is carried out along all of the planned division lines 14 that have been newly aligned with the X-axis direction. As shown in FIG. 5, grooves 100 are formed in the resin film 20 along all of the planned division lines 14 formed on the substrate 10, to a depth that does not reach the planned division lines 14, and leaves a resin film 20 with a thickness of, for example, 10 to 20 μm at the bottom.

[0023] (Exposure process) As described above, after the groove formation process has been carried out, an exposure process is carried out in which plasma etching is performed on the surface of the resin film 20 using a gas that etches the resin film 20, thereby removing 10 to 20 μm of the resin film 20 left at the bottom of the groove 100 by the groove formation process, thereby exposing the planned division lines 14.

[0024] The exposure step can be performed, for example, by a known plasma processing apparatus (not shown). The plasma processing apparatus includes, for example, a chamber capable of accommodating the substrate 10 and a processing space formed inside the chamber. The plasma processing apparatus introduces an etching gas into the evacuated processing space housing the substrate 10, converts the etching gas into plasma using a high-frequency current, and causes the plasma to collide with the resin film 20 laid on the substrate 10, thereby performing plasma etching. The bottom of the groove 100 is removed by this plasma processing apparatus, thereby exposing the planned division lines 14 formed on the substrate 10, as shown in FIG. 6. Oxygen can be used as the etching gas.

[0025] By carrying out the above-mentioned exposure process, the planned division lines 14 on the surface 10a of the substrate 10 are exposed, and only the area 12 partitioned by the planned division lines 14 is masked by the above-mentioned resin film 20, thereby completing the mask formation method of this embodiment.

[0026] The above-described mask forming method eliminates the need to provide a mask for each individual chip to be divided on the substrate 10, thereby eliminating the troublesome problem. Furthermore, if a resin film that functions as a mask is laid on the substrate 10 and then a cutting blade is used to form grooves in the resin film to expose the division lines 14, there is a risk of damaging the substrate 10. However, in the above-described embodiment, the grooves 100 are formed to a depth that does not reach the division lines 14, and then the division lines 14 are exposed by plasma etching, so that the division lines 14 on the substrate 10 are not damaged.

[0027] After the mask forming method of this embodiment is completed as described above, the masked substrate 10 is transferred to a known plating device (not shown), where metal plating is applied to the surface 10a of the substrate 10 to form, for example, an AuSn plating layer along the division lines 14. The metal-plated substrate 10 is then transferred to a cutting device similar to the cutting device 30 shown in FIG. 4, where a dividing process is performed to cut the substrate 10 along the division lines 14, dividing the substrate 10 into individual chips corresponding to the above-described regions 12. The thickness of the cutting blade used in this dividing process is thinner than the thickness of the cutting blade 35 used in forming the grooves 100. By cutting the center of the division lines 14 where the AuSn plating layer is formed, the desired chips are formed with a plating layer on the periphery. The mask applied to the surface 10a corresponding to the regions 12 may be removed before the dividing process, but it is preferably removed after the dividing process. By removing the mask after the dividing process, the divided chips are prevented from being contaminated by cutting chips discharged during the cutting process or in subsequent processes. [Explanation of symbols]

[0028] 10: Circuit board 10a: surface 10b: Back side 12: Area 14: Planned division line 18: Liquid resin supply means 18a: Supply nozzle 19: Liquid resin 20: Sheet (resin film) 30: Cutting equipment 31: Chuck table 32:Cutting means 33: Spindle housing 34: Spindle 35: Cutting blade 36: Blade cover 37: Cutting water supply nozzle 100: Groove

Claims

1. 1. A method for forming a mask used when metal plating is performed along planned division lines of a substrate having an upper surface to be divided into individual chips by the planned division lines, the method comprising: a resin film laying step of laying a resin film serving as a mask on the upper surface of the substrate; a groove forming step of positioning a cutting blade on the surface of the resin film in correspondence with the planned dividing lines to form grooves having a depth that does not reach the planned dividing lines; an exposing step of plasma etching the surface of the resin film with a gas that etches the resin film, thereby removing the bottom of the groove and exposing the planned dividing lines; A method for forming a mask comprising:

2. 2. The method for forming a mask according to claim 1, wherein in the resin film laying step, the resin film is a liquid resin or a sheet.

3. 3. The method for forming a mask according to claim 2, wherein in the resin film laying step, the liquid resin is an epoxy resin, and the sheet is a thermocompression-bonded sheet that is bonded by heating.

4. 2. The method for forming a mask according to claim 1, wherein the gas for etching the resin film in the exposing step is oxygen.

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