JP2004349275A - Process for producing chip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for producing a chip having a sufficient flexural strength even in case of a thin chip by suppressing chipping occurring on the front and rear surfaces of the chip as much as possible at the time of dicing. <P>SOLUTION: A V-groove G is formed in a wafer W to leave a slight thickness by means of a dicing blade 21A having a V-shaped forward end and the remaining part is cut completely by means of an extremely thin dicing blade 21B to produce a chip C having a substantially trapezoidal cross-section. Thickness being left when the V-groove is formed is set in the range of 5-30 μm and the extremely thin dicing blade 21B employs abrasive grains having a grain size as fine as #4000-#6000. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing chips such as semiconductor devices and electronic components, and more particularly to a method for manufacturing chips by dicing a wafer into individual chips.
[0002]
[Prior art]
Conventionally, in order to divide a wafer having a semiconductor device, electronic components, and the like formed on its surface into individual chips, a dicing apparatus that cuts the wafer by cutting the wafer with a grinding groove using a thin grindstone called a dicing blade has been used. . The dicing blade is obtained by electrodepositing fine diamond abrasive grains with Ni, and has a very thin thickness of about 30 μm.
[0003]
The dicing blade was rotated at a high speed of 30,000 to 60,000 rpm to cut into the wafer, and the wafer was completely cut (full cut) or incompletely cut (half cut or semi-full cut). Half cut is a method of cutting about half the thickness of the wafer, and semi-full cut is the case where a ground groove is formed while leaving a thickness of about 10 μm.
[0004]
However, in the case of grinding with a dicing blade, the wafer is a brittle mode because the wafer is a highly brittle material, and chipping occurs on the front and back surfaces of the wafer, and this chipping is a factor that lowers the performance of the divided chips. Was.
[0005]
Particularly, an IC chip incorporated in a thin IC card typified by a smart card recently has a thickness of 100 μm or less, and has a bending strength (breakage when a bending stress is applied) of the extremely thin IC chip itself. Difficulty), but there is a problem that chip bending strength of the chip is reduced due to chipping of the chip periphery formed at the time of dicing. In addition, chipping at the periphery of the chip is a troublesome problem because fine cracks gradually progress inside.
[0006]
As a means to solve the problem of reduction in bending strength due to this chipping in the dicing process, a dicing sheet is attached to the back surface of the wafer and diced from the surface, and another sheet is attached to the surface while maintaining the arrangement of each chip. After that, a technique has been proposed in which the dicing sheet on the back surface is peeled off, and the back surface and the end surface of each divided chip are coated with a thin film such as polyimide to reinforce each chip (for example, see Patent Document 1).
[0007]
In this technique, a sheet is attached to the back surface again after coating the chip with a reinforcing thin film, and then the sheet on the front surface is peeled off and sent to a die bonding step.
[0008]
[Patent Document 1]
JP-A-2002-43251
[Problems to be solved by the invention]
However, the technique proposed in the above patent document requires a reinforcing thin film coating step and a drying step in addition to the dicing step, and the adhesive sheet must be replaced twice more than in the conventional step. However, there is a problem that the chip cost increases.
[0010]
Also, even if the surface is covered, it is unavoidable that the fine cracks generated on the periphery of the chip gradually progress to the inside, which may hinder the electrical performance inherent to the chip or after a long time has passed. However, it was not possible to solve the problem of lowering the bending strength of the chip.
[0011]
The present invention has been made in view of such circumstances, and minimizes chipping that occurs on both front and back surfaces of a chip during dicing, and manufactures a chip having a sufficient bending strength even with a thin chip. An object of the present invention is to provide a chip manufacturing method.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a chip manufacturing method for dicing a wafer into individual chips by using a dicing blade having a V-shaped tip. A step of forming a V-groove with an uncut thickness and a step of completely cutting the uncut portion with an extremely thin dicing blade to produce a chip having a substantially trapezoidal cross section. .
[0013]
According to the first aspect of the invention, the wafer is formed with a V-shaped groove having a slight thickness by a dicing blade having a V-shaped tip, and the remaining portion is completely cut by an extremely thin dicing blade, and the cross section is substantially A trapezoidal chip is manufactured. In a chip having a trapezoidal cross section, internal stress generated when a bending stress is applied is more easily released to the outside from the side than in a chip having a normal rectangular cross section, so that the bending strength is improved.
[0014]
According to a second aspect of the present invention, in the first aspect of the present invention, the thickness of the wafer left uncut in the step of forming the V-groove is 5 μm to 30 μm.
[0015]
According to the second aspect of the present invention, since the wall thickness left behind by the V-groove is as thin as 5 μm to 30 μm, even if a very fine dicing blade is used as an ultra-thin dicing blade for completely cutting the remaining portion, Cutting can be performed without reducing the cutting speed.
[0016]
According to a third aspect of the present invention, in the first or second aspect of the present invention, the ultra-thin dicing blade has an abrasive grain size of $ 4000 to $ 6000 and a thickness of 10 µm to 30 µm. Features.
[0017]
According to the third aspect of the present invention, since the dicing blade for completely cutting the part left uncut by the V-groove has an extremely fine grain size of $ 4000 to $ 6000, chipping does not occur at the time of complete cutting. Furthermore, since the thickness is as thin as 10 μm to 30 μm, the sectional shape of the divided chip becomes substantially trapezoidal, and the chip bending strength is improved in addition to the fact that chipping does not occur.
[0018]
According to a fourth aspect of the present invention, in the first aspect of the present invention, the step of forming the V-groove and the step of completely cutting are performed at the same processing speed. Features.
[0019]
According to the invention of claim 4, since the V-groove forming step and the complete cutting step are performed at the same processing speed, the V-groove processing is performed using a dicing apparatus having two spindles whose rotation axes are parallel to each other. And complete cutting can be performed at the same time, and a chip having a trapezoidal cross section can be manufactured with almost no reduction in throughput.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a chip manufacturing method according to the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same members are given the same numbers or symbols.
[0021]
First, the configuration of the dicing apparatus used in the chip manufacturing method according to the present invention will be described. FIG. 1 is a perspective view showing the appearance of the dicing apparatus. The dicing apparatus 10 includes a load port 60 for transferring a cassette containing a plurality of works to and from an external device, a conveying unit 50 having a suction unit 51 for conveying the works to each unit of the apparatus, and imaging the surface of the work. It comprises an imaging means 81 for performing the processing, a processing section 20, a spinner 40 for cleaning and drying the processed work, a controller 100 for controlling the operation of each section of the apparatus, and the like.
[0022]
The processing section 20 is provided with a high-frequency motor built-in type air-bearing spindle 22 having two rotating blades (dicing blades) 21 mounted at the ends thereof, and has a rotating blade (dicing blade) 21 at 30,000 to 60,000 rpm. , And the index feed in the Y direction and the cut feed in the Z direction are performed independently of each other. Further, the work table 23 on which the work is sucked and placed is ground and fed in the X direction in FIG.
[0023]
FIG. 2 is a conceptual diagram illustrating an embodiment according to a chip manufacturing method of the present invention. Of the two spindles 22 opposed to each other of the dicing device 10, a dicing blade 21A having a V-shaped tip is attached to a spindle 22A on the near side (left side in FIG. 2), and a spindle on the far side (right side in FIG. 2). An extremely thin dicing blade 21B is attached to 22B.
[0024]
The V-shaped dicing blade 21A is an electroformed blade of diamond abrasive grains, has a grain size of 4000, an outer diameter of about 55 mm, and a V-angle of 40 °, and is rotated at 50,000 to 55,000 rpm. The ultra-thin dicing blade 21B is also an electroformed blade of diamond abrasive grains, having a particle size of ♯4000 to ♯6000 (preferably ♯5000), an outer diameter of about 55 mm, a blade thickness of 10 μm to 30 μm (preferably 15 μm to 20 μm), A blade having a protruding amount of 300 μm and a concentration of abrasive grains lower than the standard is used, and is rotated at 50,000 rpm to 55,000 rpm.
[0025]
When the particle size of the ultra-thin dicing blade 21B is coarser than $ 4000, the backside chipping of the wafer W occurs more than an allowable value, and when it is finer than $ 6000, the grinding load is too large to perform dicing. In addition, if the blade thickness is less than 10 μm, the rigidity is weak, and the blade is immediately broken, which is not practical. If the thickness is more than 30 μm, if the cross section of the chip C is trapezoidal in the case of an extremely thin wafer W having a thickness of 100 μm or less. Not suitable.
[0026]
In the chip manufacturing method according to the present invention, first, as shown in FIG. 2A, a street between a plurality of pattern surfaces P formed on the main surface of the wafer W is formed with the back surface of the wafer W attached to a dicing tape T. A V-shaped groove G is formed in S by a dicing blade 21A having a V-shaped tip.
[0027]
The V-groove G thus formed is as shown in part A of FIG. FIG. 3 is an enlarged view of the portion A. As shown in the figure, the V groove G is left uncut from the back surface of the wafer W by the thickness of D. The uncut amount D is 5 μm to 30 μm, preferably 10 μm to 25 μm, and more preferably 15 μm to 20 μm. The grinding speed at this time was 40 mm / sec when the wafer W was Si.
[0028]
After this V-groove formation is performed for several lines, as shown in FIG. 2 (b), the bottom of the first V-groove G is cut into a dicing tape T with a thickness of about 10 μm using an extremely thin dicing blade 21B. Dicing (complete cutting) is performed. The grinding speed at this time was also 40 mm / sec.
[0029]
Note that if the uncut amount D is 5 μm or less, cracks may reach the back surface of the wafer W in some places during V-groove formation. When the uncut amount D is 30 μm or more, the grinding load is too large during the full-cut dicing using an ultra-thin blade with a grain size of れ る 5000 performed after the formation of the V-groove, and the dicing must be performed at an extremely low grinding speed. It is not practical from the viewpoint of throughput.
[0030]
As described above, since the V-groove formation and the full-cut dicing have the same grinding speed, the preceding V-groove formation and the subsequent full-cut dicing can be performed simultaneously. In this way, as shown in FIG. 2C, the V-groove formation and the full-cut dicing sequentially proceed simultaneously, and when the processing of all the streets S is completed, the wafer W is rotated by 90 ° and goes straight to the street S. V-groove formation and full-cut dicing of the street S are performed.
[0031]
As described above, since the V-groove G is first formed on the pattern surface P side of the wafer W by the dicing blade 21A having the V-shaped tip, it is possible to cope with various types of device films. For example, in the case of a film such as a Low-K film, which is easy to generate a mark, and in the case of a polyimide-based thick film device having a thickness of 10 μm to 20 μm, chipping and the mark of the film are reduced. Dicing that is not performed is possible.
[0032]
Further, when performing the full cut dicing at the bottom of the V-groove G using an extremely thin dicing blade 21B, the grinding water easily flows to the deep V-groove G, so that the supply of the grinding water to the grinding point becomes good, and Effects such as backside chipping of W and reduction of film clogging at the tip of the dicing blade 21B are provided.
[0033]
Thus, a large number of chips C, C,... Are divided from the wafer W. As shown in FIG. 4, the divided chip C has a substantially trapezoidal cross section. Since the trapezoidal chip C has a large chamfered edge on the chip surface side, in the pickup process after dicing, the chip C is picked up by a pyramid collet or the like and compared with the conventional chip C when handling. This is advantageous because chipping of the front side edge portion hardly occurs.
[0034]
Incidentally, when dicing a Si wafer with an ultra-thin blade of usually $ 5000, the maximum grinding speed is 20 mm / sec, but in the case of the present invention, the uncut amount D is extremely small, 5 μm to 30 μm, so that Dicing can be performed at a speed of sec.
[0035]
Next, a comparative example of the chip manufacturing method of the present invention and a chip manufacturing method by a conventional dicing method will be described.
[0036]
In this experiment, the dicing blade 21A having a V-shaped tip was an electroformed blade of diamond abrasive grains having a particle size of ０００4000, an outer diameter of about 55 mm, and a tip V angle of 40 °, and was rotated at 55,000 rpm.
[0037]
The ultra-thin dicing blade 21B is also an electroformed blade of diamond abrasive grains, having a particle size of ０００5,000, an outer diameter of about 55 mm, a blade thickness of 15 μm, a blade tip protrusion amount of 300 μm, and a rotation speed of 55,000 rpm.
[0038]
In the conventional dicing method, an electroformed blade of diamond abrasive grains having a particle size of ♯2,500, an outer diameter of about 55 mm, a blade thickness of 30 μm, and a blade tip protrusion amount of 300 μm was used, and the rotation speed was 40,000 rpm.
[0039]
First, in the chip manufacturing method of the present invention, V-groove formation in which the uncut amount D is 20 μm and a full-cut dicing of the uncut portion are performed at a grinding speed of 40 mm / sec. Simultaneous grinding was performed, and 24 chips were diced with a chip size of 3 mm × 6 mm.
[0040]
Next, using a conventional dicing method, 24 pieces were diced at the same grinding speed of 40 mm / sec and a chip size of 3 mm × 6 mm by one-stage full cut. In both cutting modes, downcut was performed.
[0041]
FIG. 5 compares the magnitude of the backside chipping of the Si wafer between the chip manufacturing method of the present invention and the chip manufacturing method using the conventional dicing method in the above experiment. The measurement of chipping is obtained by observing the entire back surface of the wafer W from the dicing tape T side with a microscope and measuring the maximum value of chipping.
[0042]
As shown in FIG. 5, in the conventional dicing method, chipping was in the range of 5 μm to 22 μm, and the average value was 15.1 μm. On the other hand, in the chip manufacturing method of the present invention, the average value is 4.1 μm in the range of 2 μm to 8.5 μm, and the size of the rear surface chipping is improved to about 1 / 3.7.
[0043]
Next, using the same blade as in the backside chipping experiment, and under the same processing conditions, a Si mirror wafer having a diameter of 200 mm and a thickness of 50 μm was formed in a chip size of 10 mm × 10 mm using the chip manufacturing method of the present invention and the conventional dicing method. The chips C were manufactured by dicing 10 chips at a time by the above method, and the bending strengths of the chips C by the respective methods were compared.
[0044]
The bending strength was measured by the three-point method shown in FIG. FIG. 6A shows the measurement state of the chip C manufactured by the conventional method, and FIG. 6B shows the measurement state of the chip C manufactured by the method of the present invention. As shown in FIG. 6, the bending strength is measured by supporting the back surface of the chip C at two points, applying a stress F from the main surface side, and measuring the stress F when the chip C breaks. The distance between the two points of the back support was 4 mm, and the pressing speed from above was 0.15 mm / min.
[0045]
FIG. 7 summarizes the results of this experiment. As shown in FIG. 7, the bending strength of the chip C manufactured by the conventional method was 0.23 kgf in the range of 0.18 kgf to 0.33 kgf. On the other hand, in the case of the chip C manufactured by the method of the present invention, the average was 0.35 kgf in the range of 0.22 kgf to 0.39 kgf, and the bending strength was improved by about 50%.
[0046]
In the present invention, the V-groove G is formed in the wafer W by leaving a small thickness, and the remaining portion is completely cut by the extremely thin dicing blade 21B. Instead of complete cutting, a laser dicing method in which a laser beam is applied to the remaining portion, a modified layer is formed inside the remaining thickness, and the laser beam is cut off, may be used.
[0047]
Further, by chamfering each ridge line of the chip C having a trapezoidal cross section obtained by the chip manufacturing method of the present invention by etching, grinding, plasma etching, or the like, the bending strength of the chip C can be further improved.
[0048]
【The invention's effect】
As described above, according to the chip manufacturing method of the present invention, the wafer is formed with a V-shaped groove having a small thickness with a V-shaped dicing blade, and the remaining portion is completely formed with an extremely thin dicing blade. By cutting, a chip having a cross section having a high bending strength and a substantially trapezoidal shape can be obtained. This trapezoidal chip has a large chamfered edge on the chip surface side, so even in the pickup process after dicing, when picking up and handling the chip with a pyramid collet or the like, the chip surface has a higher surface area than a conventional chip. This is advantageous because chipping of the side edge portion hardly occurs.
[0049]
In addition, since the V-groove is formed on the pattern surface side of the wafer with a V-shaped dicing blade, chipping and chipping of the film are reduced, so that it is possible to cope with various types of device films and is not affected by the film thickness or film quality of the device. Dicing is possible.
[0050]
Also, when performing full cut dicing using an extremely thin dicing blade at the bottom of the V-groove, the grinding water easily flows into the deep V-groove, so that the supply of the grinding water to the grinding point becomes good, and the backside chipping of the wafer is performed. In addition, the effect of reducing clogging of the film at the tip of the dicing blade is great.
[0051]
In addition, since the thickness left behind when forming the V-groove is thin, a blade having a high grain size can be used as an ultra-thin dicing blade for complete cutting, and the cutting speed when using a normal blade having a small grain size can be used. While maintaining the same cutting speed, backside chipping of the wafer can be suppressed to within an allowable value.
[Brief description of the drawings]
FIG. 1 is an external view of a dicing apparatus used in a chip manufacturing method according to an embodiment of the present invention. FIG. 2 is a conceptual diagram illustrating a chip manufacturing method according to an embodiment of the present invention. FIG. 4 is a perspective view showing a chip obtained by the chip manufacturing method according to the present invention; FIG. 5 is a graph showing a comparative example of backside chipping; FIG. FIG. 7 is a graph showing a comparative example of the die strength of a chip.
Reference numeral 10: dicing apparatus, 21: dicing blade, 21A: dicing blade having a V-shaped tip, 21B: extremely thin dicing blade, 22, 22A, 22B: spindle, C: chip, D: uncut amount, G: V groove, T: dicing tape, W: wafer

Claims (4)

In a chip manufacturing method in which a wafer is diced and divided into individual chips,
Using a dicing blade having a V-shaped tip, forming a V-groove in the wafer with a slight thickness left uncut;
A step of completely cutting the uncut portion with an extremely thin dicing blade,
A chip having a substantially trapezoidal cross section. 2. The chip manufacturing method according to claim 1, wherein the thickness of the wafer left uncut in the step of forming the V groove is 5 μm to 30 μm. 3. The chip manufacturing method according to claim 1 or 2, wherein the ultra-thin dicing blade has a grain size of abrasives of $ 4000 to $ 6000 and a thickness of 10 µm to 30 µm. 4. The chip manufacturing method according to claim 1, wherein the step of forming the V-groove and the step of completely cutting are performed at the same processing speed. 5.

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