Mask formation method

Abstract

To provide a mask formation method solving the problem of finding it too troublesome to dispose a mask of a size corresponding to each chip on a chip basis since it requires much time and efforts therefor.SOLUTION: The present invention relates to a mask formation method used for applying metal plating to a predetermined dividing line of a substrate to be divided into individual chips by the predetermined dividing line. The mask formation method includes: a mask sheet preparing step of preparing a mask sheet having a size corresponding to the substrate and including a front face that can be adhered to a top face of the substrate; a first groove forming step of positioning a cutting blade on the front face of the mask sheet correspondently to the predetermined dividing line and forming a first groove with a depth which does not reach a rear face of the mask sheet; a sheet adhering step of opposing the top face of the substrate with the front face of the mask sheet and adhering the front face of the mask sheet to the top face of the substrate while making the first groove correspondent to the predetermined dividing line; and a second groove forming step of positioning the cutting blade from the side of the rear face of the mask sheet correspondently to the first groove and forming a second groove, which communicates with the first groove, with a depth which does not reach the substrate.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for forming a mask used when metal plating is performed along the division lines of a substrate to be divided into individual chips by the division 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 cut by a cutting machine equipped with a rotatable cutting blade to separate them into individual device chips, which are then used in electrical equipment such as mobile phones and personal computers.

[0003] The above-mentioned cutting device is also used when dividing a ceramic substrate into individual chips (see, for example, Patent Document 1), but before the cutting process is performed, AuSn (gold-tin) plating is applied in a grid pattern along the intended division lines, with a width exceeding the thickness of the cutting blade that will divide the ceramic substrate. [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, as mentioned above, in order to apply AuSn plating in a grid pattern along the intended division line with a width exceeding the thickness of the cutting blade, it is necessary to provide a mask of a size corresponding to each chip for each chip, which is troublesome. Furthermore, in order to make the mask arrangement more efficient, if a large mask sheet is attached to the surface of the ceramic substrate in advance and a cutting process is performed to remove the mask sheet with a width to apply AuSn plating, the tip of the cutting blade comes into contact with the surface of the substrate, which causes damage to the surface of the substrate.

[0006] The present invention has been made in view of the above facts, and its main technical object is to provide a method for forming a mask that solves the problem that the work of arranging a mask of a size corresponding to each chip for each chip without damaging the surface of the substrate is time-consuming and tedious. [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 the planned division lines of a substrate to be divided into individual chips by the planned division lines, the method comprising: a mask sheet preparation step of preparing a mask sheet having a size corresponding to the substrate and a surface that can be attached to the upper surface of the substrate; a first groove formation step of positioning a cutting blade on the surface of the mask sheet corresponding to the planned division lines and forming first grooves at a depth that does not reach the back surface of the mask sheet; a sheet attachment step of bringing the upper surface of the substrate and the surface of the mask sheet face to face and attaching the surface of the mask sheet to the upper surface of the substrate with the first grooves corresponding to the planned division lines; and a second groove formation step of positioning a cutting blade from the back side of the mask sheet corresponding to the first grooves and forming second grooves that communicate with the first grooves at a depth that does not reach the substrate.

[0008] In the mask sheet preparation step, a thermocompression sheet that is pressure-bonded by heating may be prepared as the mask sheet. Also, in the mask sheet preparation step, a sheet having an adhesive layer on its surface that has adhesive force may be prepared as the mask sheet. [Effects of the Invention]

[0009] The mask forming method of the present invention is a method for forming a mask used when applying metal plating to the planned division lines of a substrate to be divided into individual chips by the planned division lines, and comprises: a mask sheet preparation step of preparing a mask sheet that is sized to correspond to the substrate and has a surface that can be attached to the upper surface of the substrate; a first groove forming step of positioning a cutting blade on the surface of the mask sheet corresponding to the planned division lines and forming first grooves at a depth that does not reach the back surface of the mask sheet; a sheet attachment step of bringing the upper surface of the substrate and the surface of the mask sheet face to face and attaching the surface of the mask sheet to the upper surface of the substrate with the first grooves corresponding to the planned division lines; and a second groove forming step of positioning a cutting blade from the back side of the mask sheet corresponding to the first grooves and forming second grooves that communicate with the first grooves at a depth that does not reach the substrate, thereby eliminating the problem of the time-consuming and cumbersome task of providing a mask of a size corresponding to each chip for each chip. Furthermore, in the second groove forming step, the second groove is formed to a depth that does not reach the surface of the substrate and is connected to the first groove formed earlier, so that substrates including ceramic substrates are not damaged. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is an overall perspective view of the cutting device. [Figure 2] FIG. 1A is a perspective view of a substrate that is a workpiece, and FIG. 1B is a perspective view showing a manner in which a mask sheet to be attached to the substrate of FIG. 1A is placed on a chuck table. [Figure 3] (a) An oblique view showing an embodiment of the first groove forming step, (b) an enlarged cross-sectional view of a portion of the embodiment of (a), and (c) an oblique view of a substrate on which first grooves have been formed along all of the planned groove formation lines. [Figure 4] FIG. 10 is a perspective view showing an embodiment of a sheet adhering step. [Figure 5] FIG. 10 is a perspective view showing a state in which the substrate is inverted and placed again on the chuck table to perform a second groove forming step. [Figure 6](a) An oblique view showing an embodiment of the second groove forming step, (b) an enlarged cross-sectional view of a portion of the embodiment of (a), and (c) an oblique view of a substrate on which first grooves and second grooves have been formed along all of the planned groove formation lines. [Figure 7] FIG. 1(a) is a perspective view showing an embodiment of cutting processing for dividing a substrate into individual chips, and FIG. 1(b) is a partially enlarged cross-sectional view of the embodiment shown in FIG. 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] 1 shows a cutting apparatus 1 that is capable of cutting a substrate 10 shown in the figure and is suitable for carrying out the mask forming method of this embodiment. The cutting apparatus 1 includes a substantially rectangular parallelepiped housing 2, a cassette 4 placed on a cassette table 4a of the housing 2, a carry-in / out means 3 that carries out unprocessed substrates 10 supported on a frame F from the cassette 4 to a temporary storage table 5 and carries processed substrates 10 placed on the temporary storage table 5 into the cassette 4, a transport means 6 having a swivel arm that transports the substrates 10 that have been transferred to the temporary storage table 5 to a chuck table 7, a cutting means 8 that performs cutting on the substrates 10 held on the chuck table 7, an imaging means 9 that captures an image of the substrate 10 held on the chuck table 7, a cleaning and transport means 17 that transports the processed substrates 10 from the carry-in / out position where the chuck table 7 is positioned in FIG. 1 to a cleaning apparatus 16 (details of which are omitted), and a control means (not shown). The cutting means 8 can be replaced with different cutting blades (for example, cutting blades 81A and 81B of different thicknesses and types) depending on the material of the workpiece and the cutting conditions.

[0013] The substrate 10 cut by the cutting device 1 is a ceramic substrate, and as shown enlarged in FIG. 2(a), it is a rectangular substrate having a plurality of chips 12 formed on the surface 10a and partitioned by dividing lines 14. The dividing lines 14 are formed in a grid pattern, with dividing lines 14 in a predetermined direction and dividing lines 14 in a direction perpendicular to the dividing lines 14. When dividing the substrate 10 into individual chips 12 using the cutting device 1, the substrate 10 is supported on an annular frame F via protective tape T and held on a chuck table 7, as shown in FIG. 1. The substrate 10 cut by the cutting means 8 is not limited to the above-described form, and may have a form in which the chips 12 and dividing lines 14 are covered with a molding resin and are not exposed on the surface 10a.

[0014] The cutting device 1 includes an X-axis moving means for relatively moving the chuck table 7 and the cutting means 8 in the X-axis direction, and a Y-axis moving means for relatively moving the chuck table 7 and the cutting means 8 in the Y-axis direction, which is perpendicular to the X-axis direction. In this embodiment, the X-axis moving means is a means for moving the chuck table 7 in the X-axis direction, and the Y-axis moving means is a means for moving the cutting means 8 in the Y-axis direction. Both the X-axis moving means and the Y-axis moving means are not shown in the drawings.

[0015] 1, the chuck table 7 includes a suction chuck 71 that forms the holding surface of the chuck table 7, and clamps 72 that are disposed opposite the outer periphery of the chuck table 7 and grip a frame F that supports the substrate 10. The suction chuck 71 is made of a breathable material and is connected to a suction source (not shown). By operating the suction source, a negative pressure is generated on the holding surface of the suction chuck 71, allowing the substrate 10 to be sucked and held.

[0016] The control means is configured by a computer and includes a central processing unit (CPU) that performs calculations according to a control program, a read-only memory (ROM) that stores the control program, etc., a readable and writable random access memory (RAM) that temporarily stores the detected values ​​of various sensors, calculation results, etc., an input interface, and an output interface (all of which are not shown in detail). The control means is connected to and controls each operating unit of the cutting device 1, and images captured by the imaging means 9 are stored in the control means and displayed on a display means (not shown).

[0017] The cutting device 1 shown in FIG. 1 has roughly the configuration as described above, and the method for forming a mask of this embodiment, which is carried out using the cutting device 1, will be described below.

[0018] When carrying out the mask forming method of this embodiment, first, as shown in Figure 2(b), a mask sheet preparation process is carried out to prepare a mask sheet 20 having a size corresponding to the above-mentioned substrate 10 and a surface 20a that can be attached to the upper surface (surface 10a) of the substrate 10.

[0019] The mask sheet 20 can be selected from a variety of sheets, including, for example, a thermocompression sheet that is pressure-bonded by heating, a sheet with an adhesive layer on its surface, etc. In the embodiment described below, a thermocompression sheet that exhibits adhesive force when heated and can be attached by pressing is used as the mask sheet 20. When a thermocompression sheet is used as the mask sheet 20, there is no need to form an adhesive layer on the front or back of the mask sheet 20.

[0020] The thermocompression sheet used as the mask sheet 20 can be selected from polyolefin-based sheets or polyester-based sheets. When selecting the mask sheet 20 from polyolefin-based sheets, it is preferable to select it from any one of polyethylene (PE) sheets, polypropylene (PP) sheets, and polystyrene (PS) sheets. When selecting the mask sheet 20 from polyester-based sheets, it is preferable to select it from any one of polyethylene terephthalate (PET) sheets and polyethylene naphthalate (PEN) sheets. In the embodiment described below, the explanation will continue assuming that a polyethylene sheet is selected as the mask sheet 20.

[0021] Once the mask sheet 20 corresponding to the size of the substrate 10 has been prepared through the mask sheet preparation process, it is placed on the holding surface of the suction chuck 71 of the chuck table 7 as shown in FIG. 2(b), and the suction source is activated to hold the mask sheet 20 by suction. Next, the X-axis movement means is activated to position the chuck table 7 directly below the imaging means 9, and information on the outer shape and surface height position of the mask sheet 20 is detected and stored in the control means. Note that, since the surface height information of the mask sheet 20 is the thickness of the mask sheet 20, it can also be input and stored in the control means in advance. Here, the control means pre-stores position information of the planned division lines 14 formed on the surface 10a of the substrate 10, which is the workpiece, in XY coordinates. Positions on the mask sheet 20 corresponding to the planned division lines 14 are set as planned groove formation lines along which first grooves 100 and second grooves 110, which will be described later, will be formed. The groove formation lines, like the division lines 14, are set in a grid pattern with groove formation lines set in a predetermined direction and groove formation lines set in a direction perpendicular to the predetermined direction (neither of which is shown in the figure).

[0022] After the mask sheet 20 is held by suction on the chuck table 7 and information such as the outer shape of the mask sheet 20 and the height of the surface 10a is stored in the control means, the predetermined direction of the groove formation line is aligned with the X-axis direction, as shown in FIG. 3(a), and the groove formation line to be machined is positioned directly below the cutting means 8. The cutting means 8 includes a spindle housing 80 extending in the Y-axis direction, a rotating spindle 82 rotatably supported by the spindle housing 80, a cutting blade 81A fixed to the tip of the rotating spindle 82, a blade cover 83 that covers the rotating spindle 82 and the cutting blade 81A, and a cutting water supply nozzle 84 that supplies cutting water to the area to be cut by the cutting blade 81A. The cutting blade 81A is rotated by a spindle motor (not shown). The cutting blade 81A is attached to cut the mask sheet 20 to form grooves, and is, for example, a blade with a cutting edge having a thickness of 100 μm at the tip.

[0023] The cutting blade 81A, rotated at high speed, is positioned on the groove formation line aligned in the X-axis direction. The cutting feed amount is adjusted in the Z-axis direction indicated by the arrow Z by a cutting feed means (not shown). The cutting blade 81A is then fed in the X-axis direction to form the first grooves 100. As can be seen from the partially enlarged cross-sectional view of FIG. 3(b), the first grooves 100 are formed to a depth that does not reach the back surface 20b of the mask sheet 20. Furthermore, the cutting blade 81A of the cutting means 8 is indexed and fed onto a groove formation line adjacent in the Y-axis direction to the groove formation line where the first grooves 100 are formed, but where no first grooves 100 are formed, to form the first grooves 100 in the same manner as described above. By repeating these steps, the first grooves 100 are formed along all groove formation lines along the X-axis direction. Next, the chuck table 7 is rotated 90 degrees, the direction perpendicular to the direction in which the first grooves 100 were previously formed is aligned with the X-axis direction, and the above-mentioned groove formation processing is performed on all of the groove formation lines newly aligned with the X-axis direction, forming the first grooves 100 along all of the groove formation lines on the mask sheet 20 (see FIG. 3(c)). As described above, the first grooves 100 are formed along all of the groove formation lines on the mask sheet 20, thereby completing the first groove formation step.

[0024] After the first groove forming step has been carried out as described above, the substrate 10 described based on Figure 2(a) is inverted as shown in the upper part of Figure 4, with the surface 10a of the substrate 10 facing downward, and the surface 10a facing the surface 20a on which the first grooves 100 have been formed after the first groove forming step described above, and a sheet adhering step is carried out in which the surface 20a of the mask sheet 20 is adhered to the surface 10a of the substrate 10 with the first grooves 100 aligned with the intended dividing lines 14 of the substrate 10.

[0025] As described above, since a polyethylene sheet is selected as the mask sheet 20, when the sheet adhering step is carried out, the mask sheet 20 is heated to a predetermined temperature (120°C to 140°C, which is close to the melting point of the polyethylene sheet) to exert adhesive force and is thermocompression bonded to the surface 10a of the substrate 10. The means for carrying out this heating is not particularly limited, but the mask sheet 20 can be heated to the above-mentioned predetermined temperature range and exert adhesive force by heating using a heater attached inside the chuck table 7 or by heating by blowing hot air from above the mask sheet 20. Furthermore, to increase the degree of pressure bonding, the mask sheet 20 may be pressed from the side with a roller or the like.

[0026] After the sheet attachment process has been carried out as described above, the suction source connected to the chuck table 7 is stopped to release the negative pressure generated in the chuck table 7, and the substrate 10 with the mask sheet 20 attached to its front surface 10a is removed from the chuck table 7 as shown in Figure 5 and inverted as shown on the left, and placed again on the chuck table 7 with the back surface 10b of the substrate 10 facing downward and the back surface 20b of the mask sheet 20 facing upward, and held by suction.

[0027] Next, as in the first groove forming process described above, the mask sheet 20 is imaged using the imaging means 9, and the direction along the predetermined groove formation line stored in the control means is aligned with the X-axis direction, and the groove formation line to be processed is positioned directly below the cutting blade 81A of the cutting means 8.

[0028] Next, as shown in FIG. 6( a), a cutting blade 81A rotated at high speed is positioned on the groove formation line where the first groove 100 aligned in the X-axis direction is formed, and the cutting feed amount in the Z-axis direction is adjusted by the cutting feed means to cut into the mask sheet 20 from the back surface 20b side, while the chuck table 7 is processed and fed in the X-axis direction to form the second groove 110. Here, as can be seen from FIG. 6( b), the second groove 110 is formed to a depth that does not reach the surface 10a of the substrate 10 and is connected to the previously formed first groove 100. Next, the cutting blade 81A of the cutting means 8 is indexed and fed onto a groove formation line adjacent in the Y-axis direction to the groove formation line where the second groove 110 is formed and where the second groove 110 is not formed, and similarly to the above, the second groove 110 is formed to a depth that does not reach the surface 10a of the substrate 10 and is connected to the previously formed first groove 100. By repeating this groove forming process, second grooves 110 are formed along all of the groove formation lines along the X-axis direction, i.e., along the first grooves 100. Next, the chuck table 7 is rotated 90 degrees, and the direction perpendicular to the direction in which the second grooves 110 were previously formed as described above is aligned with the X-axis direction, and groove forming process is performed to form second grooves 110 along all of the groove formation lines that have now been aligned with the X-axis direction, thereby forming second grooves 110 similar to those described above along all of the groove formation lines in the mask sheet 20, thereby completing the second groove forming step (see FIG. 6(c)).

[0029] According to the above-mentioned mask forming method including the mask sheet preparation step, first groove forming step, sheet attachment step, and second groove forming step, the mask sheet 20 attached to the substrate 10 has communicating grooves 100+110 formed along the planned division lines 14 of the substrate 10, connecting the first grooves 100 and the second grooves 110, making it possible to easily arrange masks of sizes corresponding to the individual chips 12. Furthermore, in the second groove forming step, the second grooves 110 are formed to a depth that does not reach the surface 10a of the substrate 10 and that is deep enough to communicate with the previously formed first grooves 100, so that the substrate 10 is not damaged.

[0030] The above-described mask formation method forms a mask covering the areas of the chips 12 on the substrate 10 that are not to be plated, and the substrate 10 is transported to an appropriate plating device where plating is performed on the substrate 10 (not shown), forming a plating layer 30 of, for example, AuSn (gold-tin) of an appropriate thickness on the surface 10a (see FIGS. 7(a) and 7(b)). In this embodiment, as described above, the communicating grooves 100+110 consisting of the first grooves 100 and the second grooves 110 are formed in the mask sheet 20, and the mask sheet 20 remains on the chips 12, so that the plating layer 30 is not formed directly on the chips 12 but is formed only in the areas corresponding to the planned division lines 14.

[0031] After the above-described plating process is performed on the substrate 10, as shown in FIG. 7(a), the substrate 10 is supported by an annular frame F via a protective tape T, and is suction-held on the chuck table 7 of the cutting device 1, with the frame F fixed by a clamp 72. Next, the substrate 10 is imaged by an imaging means 9 to detect the position of the intended division line 14, which is the processing position, and the substrate 10 is positioned directly below the cutting means 8. At this time, the cutting means 8 is equipped with a cutting blade 81B, instead of the above-described cutting blade 81A, which cuts the substrate 10 and divides it into individual chips. The cutting blade 81B is thinner (e.g., 30 μm) than the cutting blade 81A and is thinner than the width dimension of the plating layer 30 formed corresponding to the 100 μm width of the first groove 100 and the second groove 110. 7(b), cutting blade 81B is rotated at high speed, and the X-axis feed means, Y-axis feed means, and cutting feed means are operated to perform a cutting feed from above along the center of the width direction of division lines 14, thereby performing a dividing step of dividing substrate 10 into individual chips 12. In this dividing step, cutting blade 81B, which has a thinner cutting edge on the tip side than cutting blade 81A, is used to perform cutting along division lines 14, so that chips 12 are divided into individual chips 12 with plating layer 30 surrounding the outer periphery of each chip 12.

[0032] In the above-described embodiment, after the mask forming method is performed, plating is performed without removing the mask sheet 20 on the chips 12, and the chips are then divided into individual chips 12 by the cutting means 8. This prevents chips 12 generated by the cutting process and cutting water containing the cutting waste from directly adhering to the chips 12, thereby contaminating the chips 12. However, the present invention is not limited to this, and the mask 20 may be removed from the chips 12 before cutting the substrate 10. If a thermocompression sheet is selected as the mask sheet 20, it is preferable to cool it to reduce its adhesive strength before removing it from the substrate 10.

[0033] In the above embodiment, a thermocompression sheet was selected as the mask sheet 20, but the present invention is not limited to this. Alternatively, a sheet having an adhesive layer on its surface coated with an adhesive paste or a UV sheet whose adhesive strength is reduced by irradiating the adhesive layer with ultraviolet light may be selected. When a UV sheet is selected as the mask sheet 20, heating is not required during the sheet attachment process, simplifying the process compared to when a thermocompression sheet is selected. However, since ultraviolet light is required to reduce the adhesive strength, ultraviolet light irradiation is required before the plating process described above. [Explanation of symbols]

[0034] 1:Cutting device 2: Housing 3: Carrying in / out means 4: Cassette 4a: Cassette table 5: Temporary table 6: Means of transport 7: Chuck table 71: Vacuum chuck 72: Clamp 8: Cutting means 80: Spindle housing 81A: Cutting blade 81B: Cutting blade 82: Rotating spindle 83: Blade cover 84: Cutting water supply nozzle 9: Imaging means 10: Circuit board 12: Chip 14: Planned division line 16: Cleaning equipment 17: Cleaning and carrying out means 20: Mask sheet 20a: Surface 20b: Back side 30: Plating layer 100: First Groove 110: The Second Groove

Claims

1. 1. A method for forming a mask used when metal plating is performed along planned division lines of a substrate to be divided into individual chips by the planned division lines, comprising: a mask sheet preparation step of preparing a mask sheet having a size corresponding to the substrate and a surface that can be attached to the upper surface of the substrate; a first groove forming step of positioning a cutting blade on the front surface of the mask sheet corresponding to the intended dividing line and forming first grooves to a depth that does not reach the back surface of the mask sheet; a sheet adhering step of making the upper surface of the substrate face the surface of the mask sheet and adhering the surface of the mask sheet to the upper surface of the substrate so that the first grooves correspond to the intended division lines; a second groove forming step of positioning a cutting blade from the back surface side of the mask sheet in correspondence with the first groove to form a second groove communicating with the first groove at a depth that does not reach the substrate; A method for forming a mask comprising:

2. 2. The method for forming a mask according to claim 1, wherein in the mask sheet preparation step, a thermocompression sheet that is pressure-bonded by heating is prepared as the mask sheet.

3. 2. The method for forming a mask according to claim 1, wherein in the mask sheet preparation step, a sheet having an adhesive layer on its surface is prepared as the mask sheet.

Images