JP6955977B2 - How to form chips - Google Patents

Description

The present invention relates to a method for forming a chip having a device on the front surface and a metal layer on the back surface.

On the surface of a workpiece such as a device wafer, a device is formed in a region partitioned by a grid-like planned division line, and by dividing along the planned division line, individual chips having the device are formed. It is divided. For example, if a device wafer having a metal layer formed on the back surface is divided by cutting with a cutting blade, the cutting blade is clogged, which causes large chipping and cracks in the device wafer and may damage the cutting blade. be. Therefore, for example, the division method shown in Patent Document 1 below has been proposed. In this division method, a device wafer having a processing groove formed along a planned division line is attached to a sheet, and then the device wafers are individually placed starting from the processing groove by sandwiching and expanding the four sides of the sheet. It can be divided into chips.

Japanese Unexamined Patent Publication No. 2010-182901

However, since the metal layer formed on the device wafer has ductility, there is a problem that it is difficult to be divided by the above-mentioned division method.

An object of the present invention is to provide a method for forming a insert capable of preventing clogging of a cutting blade without deteriorating the processing quality.

The present invention is a method for forming a chip having a device on the front surface and a metal layer on the back surface, wherein the device is formed in each region divided by a plurality of planned division lines intersecting the front surfaces. A thinning step of grinding the back surface to reduce the thickness to the finish thickness of the chip, and after performing the thinning step, a dress wafer is arranged on the back surface of the device wafer via a metal paste to form a composite wafer. After performing the dress wafer arrangement step to be formed and the dress wafer arrangement step, the cutting blade cuts the cutting blade from the surface of the composite wafer to the dress wafer, and the cutting blade follows the planned division line. A cutting step of cutting the device wafer together with the metal paste, and a dress wafer removing step of removing the dress wafer by grinding the back surface of the composite wafer up to the metal paste after performing the cutting step. Equipped with.

The dress wafer is preferably made of the same material as the device wafer.

The chip forming method according to the present invention is thin, in which the back surface of a device wafer in which a device is formed in each region divided by a plurality of planned division lines intersecting the surfaces is ground and thinned to the finishing thickness of the chip. After performing the thinning step and the thinning step, the dress wafer arrangement step of forming the composite wafer by arranging the dress wafer on the back surface of the device wafer via the metal paste and the dress wafer arrangement step are performed. , A cutting step of cutting the device wafer together with the metal paste along the planned division line with the cutting blade while cutting the cutting blade from the surface of the composite wafer to the dress wafer, and after performing the cutting step, the metal paste is reached. Since it is equipped with a dress wafer removal step that removes the dress wafer by grinding the back surface of the composite wafer, the cutting blade cuts the device wafer and the metal paste even if the highly ductile metal paste is cut with the cutting blade. Since the dress wafer is cut immediately after the cutting, the spontaneous cutting of the cutting blade is promoted, the cutting blade is not clogged, and there is no possibility of large chipping or cracking. Therefore, according to the present invention, it is possible to obtain a chip with a metal paste having good processing quality.

When the dress wafer is made of the same material as the device wafer, the spontaneous cutting action of the cutting blade can be further promoted and the sharpness of the cutting blade can be maintained constant when the cutting step is performed. ..

It is a perspective view which shows the structure of an example of a device wafer. It is sectional drawing which shows the surface protection member arrangement step. It is a perspective view which shows the thinning step. It is sectional drawing which shows the dress wafer arrangement step. It is sectional drawing which shows the surface protection member removal step. It is a perspective view which shows the cutting step. It is sectional drawing which shows the 2nd surface protection member arrangement step. It is a perspective view which shows the dress wafer removal step. It is sectional drawing which shows the structure of the device wafer which the dress wafer was removed. It is sectional drawing which shows the transfer step. It is sectional drawing which shows the pickup step.

The device wafer W shown in FIG. 1 is an example of a workpiece having a circular plate-shaped substrate, and the device D is formed on the surface Wa of the device wafer W in each region partitioned by a plurality of grid-like division schedule lines S. Has been done. The back surface Wb on the side opposite to the front surface Wa of the device wafer W is a surface to be processed by grinding or the like. The material of the substrate constituting the device wafer W is not particularly limited, and is, for example, silicon (Si), silicon carbide (SiC), glass, ceramics, sapphire, or the like. A metal layer, which will be described later, is formed on the back surface Wb of the device wafer W shown in the present embodiment. Hereinafter, a method for forming the device wafer W into a chip having the device D on the front surface Wa and the metal layer on the back surface Wb will be described.

(1) Surface protection member arrangement step As shown in FIG. 2, the surface protection member 1 is attached to the surface Wa of the device wafer W. The surface protection member 1 has at least a size substantially the same as that of the device wafer W, and is a glue made of an acrylic or rubber resin on a base material made of a resin such as polyolefin, polyvinyl chloride, or polyethylene taffeta. A surface protective tape composed of layers. Each device D is protected by attaching the surface protection member 1 to the surface Wa of the device wafer W and covering the entire surface of the surface Wa. The surface protection member 1 is not limited to the surface protection tape, and may be made of a hard plate such as glass or a silicon wafer.

(2) Thinning Step As shown in FIG. 3, for example, the device wafer W is held by the holding surface 21 of the holding table 20, and the back surface of the device wafer W is held by the grinding means 10 arranged on the upper side of the holding table 20. Wb is ground and thinned to the finished thickness of the chip. The grinding means 10 is annularly fixed to a spindle 11 having a vertical axis orthogonal to the holding surface 21, a grinding wheel 13 mounted at the lower end of the spindle 11 via a mount 12, and a lower portion of the grinding wheel 13. It is provided with a grinding wheel 14. An elevating means (not shown) is connected to the grinding means 10, and the entire grinding means 10 can be elevated and lowered while rotating the grinding wheel 13 by the elevating means.

When grinding the device wafer W, the surface protection member 1 side attached to the front surface Wa of the device wafer W is held by the holding surface 21 of the holding table 20 to expose the back surface Wb of the device wafer W upward. The holding table 20 is rotated in the direction of arrow A, for example. Next, the grinding means 10 lowers the grinding wheel 13 at a predetermined grinding feed speed while rotating it in the direction of arrow A, for example, and grinds the chip while pressing the back surface Wb of the device wafer W with the rotating grinding wheel 14. Thin to the finish thickness. The thinning step shown in this embodiment is not limited to the above-mentioned grinding operation, and after rough grinding the device wafer W, the device wafer W after rough grinding is finish-ground to the finish thickness of the chip, and then the device wafer. W may be polished.

(3) Dress Wafer Arrangement Step After performing the thinning step, as shown in FIG. 4, the dress wafer W1 is arranged on the back surface Wb of the device wafer W via the metal paste 2 to form the composite wafer 3. .. The dress wafer W1 functions as a dress member for shaping and sharpening the cutting blade when performing the cutting step described later. The material of the dress wafer W1 may be different from that of the device wafer W, but it is more preferable that the dress wafer W1 is made of the same material as the device wafer W.

The metal paste 2 shown in the present embodiment is a metal layer formed on the back surface of the chip, and is formed into a sheet in which metal particles are dispersed in an adhesive film called, for example, a die attach film (DAF). .. The metal paste 2 may be attached to the back surface Wb of the device wafer W, or may be attached to the back surface of the dress wafer W1 and then the device wafer W may be attached to the dress wafer W1.

Further, the metal paste 2 may be a paste in which metal particles are dispersed in a DAF having ultraviolet curability and thermosetting property. In this case, it is preferable to apply the metal paste 2 to the back surface Wb of the device wafer W or the back surface of the dress wafer W1 and then cure the metal paste 2 by irradiating with ultraviolet rays or heating. Further, the metal paste 2 may be composed of a single metal such as a solder paste or a silver paste. In this way, the composite wafer 3 in which the device wafer W and the dress wafer W1 are integrated is formed so as to sandwich the metal paste 2.

After forming the composite wafer 3, as shown in FIG. 5, the front and back surfaces of the composite wafer 3 are inverted, the device wafer W side is turned upward, and the surface protection member 1 is peeled off from the entire surface Wa of the device wafer W. Remove. As a result, the surface of the composite wafer 3 (the surface Wa of the device wafer W) is exposed.

(4) Cutting Step After performing the dress wafer arrangement step, as shown in FIG. 6, the dress wafer is formed from the surface Wa of the device wafer W along the planned division line S by using the cutting means 30 for cutting the workpiece. The device wafer W is cut together with the metal paste 2 by cutting up to W1. The cutting means 30 includes a spindle 31 having a horizontal (Y-axis direction in the illustrated example) axis, a spindle housing 32 that rotatably surrounds the spindle 31, and a cutting blade 33 mounted on the tip of the spindle 31. The cutting blade 33 is also rotated by the rotation of the spindle 31. The cutting means 30 includes a moving means (not shown) for moving the cutting means 30 in the index feed direction (Y-axis direction) orthogonal to the machining feed direction (X-axis direction in the illustrated example), and the cutting means 30 in the vertical direction. An elevating means for elevating and lowering is connected.

After holding the composite wafer 3 on a holding table (not shown), the holding table is moved below the cutting means 30 and the spindle 31 is rotated to move the cutting blade 33 around the axis in the Y-axis direction, for example, in the direction of arrow R. While rotating, the cutting means 30 is lowered in a direction approaching the surface Wa of the device wafer W. While cutting the cutting blade 33 from the surface Wa of the device wafer W to the dress wafer W1, the device wafer W is completely formed with the metal paste 2 along the line S to be divided for one row oriented in the X-axis direction with the cutting blade 33. A cutting groove M is formed along the planned division line S by cutting the wafer.

When the composite wafer 3 is cut by the cutting blade 33, the cutting blade 33 always cuts into the dress wafer W1 immediately after the metal paste 2 is cut, so that the spontaneous cutting action of the cutting blade 33 can be promoted. When the dress wafer W1 is made of the same quality as the device wafer W, the spontaneous cutting action of the cutting blade 33 can be further promoted, and the sharpness of the cutting blade 33 can be maintained constant.

After forming the cutting groove M along the planned division line S for one row facing the X-axis direction, the cutting means 30 is indexed in the Y-axis direction, and the above is made for all the scheduled division lines S facing the X-axis direction. The cutting operation of is repeated to form a cutting groove M. After that, the composite wafer 3 is rotated by 90 ° by rotating the holding table, the planned division line S oriented in the Y-axis direction is directed in the X-axis direction, and the same cutting as described above is repeated, and all the planned division lines are performed. A cutting groove M is formed along S.

(5) Second surface protection member arrangement step As shown in FIG. 7, the second surface protection member 1A is attached to the surface Wa of the device wafer W on the surface of the composite wafer 3 (the surface Wa of the device wafer W). , Each device D is protected by covering the entire surface Wa. Similar to the surface protection member 1 described above, the second surface protection member 1A may be a surface protection tape or may be made of a hard plate such as glass or a silicon wafer.

(6) Dress Wafer Removal Step After performing the cutting step and the second surface protection member disposing step, as shown in FIG. 8, the back surface of the composite wafer 3 (the back surface of the dress wafer W1) is removed by using the grinding means 10. Grind and remove. Specifically, the second surface protection member 1A side attached to the surface Wa of the device wafer W is held by the holding surface 21 of the holding table 20, and the back surface of the dress wafer W1 is exposed upward to expose the holding table 20. For example, in the direction of arrow A. Next, the grinding means 10 lowers the grinding wheel 13 at a predetermined grinding feed speed while rotating the grinding wheel 13 in the direction of arrow A, for example, and presses the back surface of the composite wafer 3 with the rotating grinding wheel 14 until the metal paste 2. The dress wafer W1 is removed by grinding.

When the dress wafer W1 is completely removed, the individual chips C on which the metal paste 2 is formed on the back surface Wb are exposed as in the device wafer W shown in FIG. In the dress wafer removal step of the present embodiment, the load current value of the spindle 11 increases when the grinding wheel 14 reaches the metal paste 2, so that the current supplied to the motor during grinding by using, for example, a current value detecting means. It is preferable to detect the value as the load current value of the spindle 11 to control the grinding amount of the composite wafer 3. That is, a threshold value indicating a predetermined grinding amount is set in advance in the grinding means 10, and when the load current value detected during grinding exceeds the threshold value, the grinding feed operation of the grinding means 10 is performed assuming that the metal paste 2 is exposed. Control. As a result, even if the thickness of the metal paste 2 and the thickness of the dress wafer W1 vary, the grinding means 10 can be controlled accurately, and only the dress wafer W1 is removed to ensure the chip C having the metal paste 2. Can be obtained in. In the dress wafer removing step shown in the present embodiment, the dress wafer W1 is removed by grinding, but the dress wafer W1 may be peeled off from the device wafer W.

(7) Transfer Step As shown in FIG. 10, the front and back surfaces of the device wafer W are inverted, and the back surface of the device wafer W is placed on the tape T attached to the frame F having an opening in the center via the metal paste 2. Wb is attached and the surface Wa of the device wafer W is turned upward. After that, the second surface protection member 1A is peeled off from the surface Wa of the device wafer W to remove it. As a result, the surface Wa of the device wafer W separated into pieces on the chip C is exposed.

(8) Pickup step As shown in FIG. 11, for example, the collet 40 picks up the chip C. The collet 40 has a suction surface 41 for sucking the chip C, and is movable in the vertical direction. The collet 40 picks up the chip C having the metal paste 2 by peeling it from the tape T by adsorbing and ascending the mounting surface of the chip C. In this way, the chip C having the metal paste 2 on the back surface is formed. The picked-up chip C is transferred to the next process and die-bonded onto a metal frame or a mounting substrate.

As described above, in the method for forming a chip according to the present invention, the back surface Wb of the device wafer W in which the device D is formed in each region divided by a plurality of planned division lines S where the surface Wa intersects is ground to obtain a chip. A thinning step of thinning to the finish thickness of the device wafer W, a dress wafer arrangement step of arranging the dress wafer W1 on the back surface Wb of the device wafer W via the metal paste 2 to form the composite wafer 3, and the composite wafer 3 A cutting step of cutting the device wafer W together with the metal paste 2 along the planned division line S by the cutting blade 33 while cutting the cutting blade 33 from the surface of the surface to the dress wafer W1 and the composite wafer up to the metal paste 2. Since the dress wafer removal step of removing the dress wafer W1 by grinding the back surface of the third is provided, even if the highly ductile metal paste 2 is cut by the cutting blade 33, the cutting blade 33 is the device wafer W and the metal paste. Since the dress wafer W1 is cut immediately after cutting with 2, the spontaneous cutting of the cutting blade 33 is promoted, the cutting blade 33 is not clogged, and there is no possibility that large chipping or cracks will occur. As described above, according to the present invention, it is possible to obtain the chip C with the metal paste 2 having good processing quality.

1,1A: Surface protection member 2: Metal paste 3: Composite wafer 10: Grinding means 11: Spindle 12: Mount 13: Grinding wheel 14: Grinding wheel 20: Holding table 21: Holding surface 30: Cutting means 31: Spindle 32: Spindle housing 33: Cutting blade 40: Collet 41: Suction surface

Claims (2)

A method for forming a chip having a device on the front surface and a metal layer on the back surface.
A thinning step of grinding the back surface of a device wafer in which a device is formed in each region divided by a plurality of planned division lines intersecting the surfaces to reduce the thickness to the finish thickness of the chip.
After performing the thinning step, a dress wafer disposing step of disposing a dress wafer on the back surface of the device wafer via a metal paste to form a composite wafer, and a dress wafer disposing step.
After performing the dress wafer arrangement step, the cutting blade cuts the device wafer together with the metal paste along the planned division line with the cutting blade while cutting the cutting blade from the surface of the composite wafer to the dress wafer. Cutting steps and
A method for forming a chip, comprising a dress wafer removing step of removing the dress wafer by grinding the back surface of the composite wafer up to the metal paste after performing the cutting step. The method for forming a chip according to claim 1, wherein the dress wafer is made of the same material as the device wafer.

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