JP2012089711A - Centering device of wafer, chamfering device and centering method of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost centering device of simple structure capable of centering a wafer with high accuracy, and to provide a chamfering device using it.SOLUTION: When a positioning cup 13 moves upward relative to a support 14 supporting a wafer W, the wafer W is supported by the tapered surface 11 of the positioning cup 13. When the wafer W is supported, the wafer W is slid on the tapered surface 11 with a vibration applied by a vibrator 12 and positioned. When the positioning cup 13 moves downward relative to the support 14, the positioned wafer W is supported by the support 14 and the wafer W is centered by the centering device 10 of the wafer W.

Description

  The present invention relates to a wafer centering apparatus used for centering a wafer, for example, when performing a chamfering process, and a chamfering apparatus including the same.

  In the manufacture of a semiconductor wafer, first, a semiconductor ingot is grown by the Czochralski method (CZ method), the floating zone melting method (FZ method), or the like, and the grown cylindrical ingot is sliced into a wafer shape. Next, a chamfering process for preventing chipping of the outer periphery of the wafer, a lapping process for eliminating thickness variations, an etching process for removing processing distortion and contaminants, a polishing process for mirroring the wafer main surface, etc. It is done sequentially.

  In the processing of such a wafer, in the chamfering process, the outer peripheral portion is ground while rotating while the wafer is sucked and held. For this reason, if the center position of the wafer is not accurately maintained, an excessively chamfered portion or a portion that remains without being chamfered (chamfered residue) occurs, which affects the quality and yield of the wafer.

  In particular, after an AlGaInP (aluminum gallium indium phosphide) epitaxial layer to be a light emitting layer is grown on a GaAs substrate by a MOVPE (Metal Organic Vapor Phase Epitaxy) method, it is transparent to a light emission wavelength by using a VPE (Vapor Phase Epitaxy) method. Since the outer peripheral portion of the wafer on which the GaP thick film current diffusion layer is grown cannot obtain normal electrical characteristics, it is necessary to accurately grind the outer peripheral portion with a chamfering device (chamfering width of 1 mm to 3 mm depending on the type). There is.

  In order to chamfer such a wafer, when the center position is accurately held, the wafer is centered manually with tweezers by visual inspection, or as an advanced type, the wafer is detected by an optical sensor. The position of the wafer was detected, and the wafer was centered by a robot mechanism (see Patent Document 1).

  However, in the manual method, the accuracy is low, the defective part is left behind and the non-defective part is excessively cut (loss), and the centering by the optical sensor and the robot mechanism is expensive. In addition, due to the environment where water is applied, troubles such as detection errors in the optical sensor have occurred.

JP-A-6-104330

  The present invention has been made in view of the above problems, and has a simple structure and a low-cost centering apparatus capable of accurately centering a wafer, a chamfering apparatus and a centering method including the centering apparatus. The purpose is to provide.

  In order to achieve the above object, the present invention provides a centering device for centering a wafer when the wafer is supported by a support, and the centering device is disposed at least coaxially with the support. A positioning cup that has a tapered surface that opens upward, supports a peripheral edge of the wafer from below with the taper surface, and a vibrator that applies vibration to the positioning cup. The cup moves up and down relatively with respect to the support, and the positioning cup moves relatively upward with respect to the support that supports the wafer, whereby the wafer is moved to the position of the positioning cup. When the wafer is supported by the taper surface, the wafer is positioned by sliding on the taper surface by the vibration applied by the vibrator. The wafer core is characterized in that the wafer is centered by supporting the positioned wafer with the support tool by moving the head downward relative to the support tool. A dispensing device is provided.

  In such an apparatus, when the wafer is supported by the taper surface of the positioning cup arranged coaxially with the support, the friction between the wafer and the taper surface is small due to the vibration applied by the vibrator. Slidably slides on the tapered surface and is positioned with high accuracy. Then, the centering can be easily and accurately performed only by supporting the positioned wafer by a support tool arranged coaxially with the positioning cup. In addition, since the positioning cup and the support are coaxially arranged and can be centered by simply moving up and down relatively, there is little trouble such as sensor failure with a simple structure, quick centering is possible, and low cost. It becomes a device.

At this time, the centering device includes a vertical movement mechanism for moving the positioning cup up and down, and the positioning cup is moved relative to the support by moving the positioning cup up and down by the vertical movement mechanism. It is preferable to move up and down.
As described above, the centering device of the present invention includes a vertical movement mechanism that moves the positioning cup up and down, and the positioning cup is moved relative to the support by moving the positioning cup up and down by the vertical movement mechanism. If it moves up and down, the degree of freedom of the relative movement of the positioning cup relative to the support is improved, and the centering of the present invention can be performed without providing a new mechanism in other devices such as the support. The apparatus can be applied, and can be easily mounted on an existing apparatus, and the apparatus can be efficiently manufactured at low cost.

At this time, it is preferable that the taper surface of the positioning cup having an upper opening is inclined within 20 ± 10 degrees with respect to the central axis of the positioning cup.
Thus, if the taper surface of the upper opening of the positioning cup is inclined within 20 ± 10 degrees with respect to the central axis of the positioning cup, the wafer slips better and can be positioned reliably. The device can be centered with higher accuracy.

At this time, it is preferable that the taper surface of the upper opening of the positioning cup is any one of a fluororesin, a polyimide resin, and a polyetheretherketone.
Thus, if the material of the tapered surface of the positioning cup is one of fluororesin, polyimide resin, and polyetheretherketone, it is a material that has less friction and the wafer is less likely to be damaged. It becomes an apparatus that can perform centering.

Further, the present invention is a chamfering device for chamfering by grinding an outer peripheral portion of a wafer, and at least the support that supports the wafer and sucks and holds the wafer when the wafer is supported by the support. A chamfering device comprising: a wafer centering device of the present invention for centering a wafer; and a circular grinder for grinding and chamfering the outer peripheral portion of the wafer adsorbed and held by the support. Providing equipment.
With such a chamfering apparatus equipped with the wafer centering apparatus of the present invention, accurate wafer chamfering can be performed quickly and accurately, so that accurate chamfering can be efficiently performed. It becomes a low-cost chamfering device that can be used.

  Further, the present invention is a centering method for centering the wafer when the wafer is supported by a support, and is arranged at least coaxially with the support and has an upwardly opening tapered surface, A positioning cup for positioning by supporting the peripheral edge of the wafer from below with the tapered surface; and a vibrator for applying vibration to the positioning cup, wherein the positioning cup is relative to the support Using a centering device that moves up and down, the positioning cup is moved relatively upward with respect to a support that supports the wafer, and the wafer is supported by a tapered surface of the positioning cup, When the wafer is supported, the wafer is positioned by sliding on the tapered surface by the vibration applied by the vibrator, and then the positioning cup is supported by the support. Relatively by moving downward to provide a centering method for wafers, which comprises carrying out the centering of the wafer by supporting the positioned wafers by the support against.

  In such a method, when the wafer is supported by the taper surface of the positioning cup arranged coaxially with the support, the friction between the wafer and the taper surface is small due to the vibration applied by the vibrator. Slidably slides on the tapered surface and is positioned with high accuracy. Then, the centering can be easily and accurately performed only by supporting the positioned wafer by a support tool arranged coaxially with the positioning cup. In addition, the positioning cup and support are coaxially arranged and can be centered by simply moving up and down relatively, so there is little trouble such as sensor failure with a simple structure, and quick centering is possible at low cost. is there.

  As described above, according to the present invention, accurate centering can be quickly performed with a simple structure. For example, by using the wafer in a chamfering process, good chamfering can be performed by high-precision centering. Thus, the wafer centering apparatus can improve the yield.

It is a flowchart which performs centering by the wafer centering apparatus of this invention. It is the schematic which shows the centering apparatus of the wafer of this invention, and the chamfering apparatus provided with the same. It is a graph which shows the result of having measured the chamfering width | variety of the wafer which centered and chamfered in the Example and the comparative example. In the wafer surface before chamfering, (a) a side view, (b) a plan view, and (c) a wafer surface showing a yield reduction portion with poor electrical characteristics and a good yield portion with good electrical characteristics. It is a graph which shows the yield by the electrical property in each area | region. It is explanatory drawing which shows the outline of the wafer before and after chamfering at the time of chamfering after performing the centering of the wafer by the conventional manual operation.

  FIG. 4A is a side view, FIG. 4B is a plan view, and FIG. 4C is a diagram showing a yield-decreasing portion with poor electrical characteristics and a favorable yield portion with good electrical characteristics in the GaAs wafer surface before chamfering. It is a graph which shows the yield by the electrical property in each area | region in a wafer surface. FIG. 5 is an explanatory view showing the outline of a wafer before and after chamfering when chamfering is performed after the wafer is manually centered by a conventional method.

In the chamfering process of the GaAs wafer, as shown in FIGS. 4 (a), 4 (b), and 4 (c), the yield-decreasing portion at the peripheral portion of the wafer having poor electrical characteristics is ground so as to leave the good yield portion as much as possible. Done. Conventionally, however, it is difficult to accurately center the wafer manually. When chamfering is performed with the held center position shifted, as shown in FIG. 5, excessive grinding portions and yield reduction portions are generated. A chamfering residue that was not completely removed occurred, causing deterioration in yield. Further, in order to eliminate the chamfering residue, it is necessary to widen the chamfering width, and a portion having good electrical characteristics is ground to a large extent, and the yield is further deteriorated.
Further, centering using a sensor or the like has problems such as an increase in apparatus cost and sensor detection failure.

  As a result of intensive investigations on such problems, the present inventors have found the following centering device of the present invention and completed the present invention.

Hereinafter, the present invention will be described in detail as an example of an embodiment with reference to the drawings, but the present invention is not limited thereto.
FIG. 1 is a flow chart of centering by the wafer centering apparatus of the present invention. FIG. 2 is a schematic view showing an example of an embodiment of the wafer centering apparatus of the present invention.

  The wafer centering apparatus 10 of the present invention shown in FIGS. 1 and 2 is a centering apparatus 10 that performs centering of the wafer W when the wafer W is supported by the support 14. The centering apparatus 10 includes: A positioning cup 13 that is disposed coaxially with the support 14 and has a tapered surface 11 that opens upward, supports the peripheral edge of the wafer W from below with the tapered surface 11, and applies vibration to the positioning cup 13. The positioning cup 13 moves up and down relatively with respect to the support 14.

  Then, as shown in FIGS. 1A and 1B, the positioning cup 13 moves upward relative to the support 14 that supports the wafer W, so that the peripheral edge of the wafer W is positioned from below. When the wafer W is supported by the 13 tapered surfaces 11, the wafer W slides on the tapered surface 11 and is positioned in a horizontal state by the vibration applied by the vibrator 12. Thereafter, as shown in FIG. 1 (c), the positioning cup 13 moves downward relative to the support 14, so that the wafer W positioned coaxially with respect to the positioning cup 13 and the support 14 is moved. The wafer W can be centered by being supported by the support tool 14.

  As described above, since the friction of the tapered surface 11 is reduced by the vibration applied by the vibrator 12, when the wafer W is supported by the tapered surface 11, the taper surface 11 is slippery and the central axis of the positioning cup 13 and the wafer W Are positioned so that their centers coincide. Then, by moving the positioning cup 13 relatively downward, the wafer W positioned by the support 14 arranged coaxially can be supported, and the wafer W can be accurately centered with a simple movement. It can be performed. In addition, since the device 10 is capable of centering only by moving up and down relatively with vibration by the vibrator, it is a low-cost device that can perform accurate centering with a simple structure. Moreover, there is almost no risk of failure such as sensor failure.

The shape of the positioning cup 13 is not particularly limited as long as it has an upwardly opening tapered surface 11. For example, if the funnel shape is used as shown in FIG. Support and positioning can be performed satisfactorily regardless of the position.
In this case, in the present invention, the inner diameter at the upper end of the tapered surface 11 of the positioning cup 13 is larger than the diameter of the wafer W to be centered, and the inner diameter at the lower end of the tapered surface 11 is the diameter of the wafer W to be centered. Smaller is better.

Moreover, it is preferable that the taper surface 11 of the positioning cup 13 which opens upward is inclined within 20 ± 10 degrees with respect to the central axis of the positioning cup 13 shown in FIG.
With such an inclination angle, the sliding of the wafer W on the tapered surface 11 is good, and accurate positioning is easy.

Further, the material of the upper opening tapered surface 11 of the positioning cup 13 is any one of fluororesin (for example, Teflon (registered trademark)), polyimide resin (for example, Vespel (registered trademark)), and polyether ether ketone (PEEK material). It is preferable that
These materials are preferable as the material of the tapered surface 11 of the apparatus 10 of the present invention because the wafer W is slippery and hardly damaged. In this case, the positioning cup 13 itself may be formed of these materials, or the outer shape may be formed of a hard material such as metal, and the fluororesin or the like may be attached to the surface thereof. The surface of at least the portion that contacts the wafer may be a fluororesin or the like.

The vibrator 12 is not particularly limited as long as it can apply vibration to the positioning cup 13. For example, a vibrator similar to that used in a vibrator or a mobile phone can be used.
Further, as the timing for operating the vibrator 12, for example, if the operation is performed immediately after the wafer is separated from the support tool 14 and before it is supported by the support tool 14 again, it is advantageous in preventing scratches on the back surface of the wafer. It is.

As shown in FIG. 1, the centering device 10 includes a vertical movement mechanism 15 that moves the positioning cup 13 up and down. The vertical movement mechanism 15 moves the positioning cup 13 up and down to move the positioning cup 13. It is preferable to move up and down relatively with respect to the support tool 14.
By providing such a vertical movement mechanism 15, the wafer W can be centered by mounting the apparatus 10 of the present invention on another existing apparatus having the support 14 without providing a new mechanism or the like. Can do. Accordingly, the wafer W can be efficiently centered at a lower cost.
However, in this case, the vertical movement of the support tool 14 and the positioning cup 13 may be relative, and only the support tool 14 has a vertical movement mechanism, and the support tool 14 and the positioning cup 13 move up and down relatively. Alternatively, both the support tool 14 and the positioning cup 13 may have a vertical movement mechanism.

  In the case of performing the centering by the apparatus 10 of the present invention, the centering can be performed by the centering method of the present invention. For example, in the chamfering process, as shown in FIG. It can be used when the wafer 14 is supported and sucked and held by the tool 14 (stage). After centering as shown in FIGS. 1A to 1C by the apparatus 10 of the present invention, the wafer W centered by the support 14 is sucked and held, and the grinder 21 of the chamfering apparatus 20 is rotated while rotating horizontally. The wafer W can be chamfered by moving it and bringing it into contact with the outer periphery of the wafer W that has been rotated in the same manner.

  With the apparatus of the present invention as described above, since accurate centering is possible, it is particularly suitable when chamfering is performed with a slight chamfering width of 1 to 3 mm. Since almost no chamfering occurs, the chamfer width can be set to the minimum necessary, and the yield is improved.

  The device of the present invention can be manufactured at a cost of about 1/20 to 1/5 of the general price of a centering device using a sensor and a robot mechanism, and the price is about 1/10 or less. It is possible to do this, and it is very low cost. In addition, the time required for the centering process is 8.7 seconds on the average of five times for the centering by the sensor and the robot mechanism, and the device of the present invention is 5.8 seconds on the average of the five times. is there. Therefore, the time of the centering process can be shortened to about 66.7% compared with the conventional apparatus.

The wafer centering apparatus of the present invention is not applied only to the chamfering apparatus exemplified above. As long as the apparatus needs to be centered when the wafer is supported by the support, any apparatus can be applied.
The wafer that can be centered by the centering apparatus of the present invention is not particularly limited, and can be used for centering GaP wafers, Si wafers, etc. in addition to the above-described GaAs wafers. As for the shape, not only a circular wafer but also a rectangular wafer can be centered in the case of a funnel-shaped positioning cup as shown in FIG.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Example)
Using the apparatus of the present invention shown in FIGS. 1 and 2, centering was performed, and then a wafer chamfering process was performed. In the centering apparatus, the positioning cup of the apparatus of the present invention was arranged coaxially with a wafer suction stage having a diameter of 30 mm having a suction mechanism and a rotation mechanism, and attached as shown in FIG. This positioning cup is made of a fluororesin, and an upper opening tapered surface is inclined 20 degrees with respect to the center axis of the positioning cup.

In the centering step, the positioning cup was first lowered by the vertical movement mechanism so that the upper surface of the wafer suction stage was positioned above the upper end of the taper surface of the positioning cup.
Then, a GaAs wafer having a diameter of 2 inches (50 mm) was placed on the stage (FIG. 1A).

Next, the positioning cup was gradually raised, and the wafer was supported by the tapered surface of the positioning cup (FIG. 1B). Immediately after the wafer left the stage, the vibrator was operated to apply vibration to the positioning cup, and the wafer was quickly positioned by vibration.
Next, the vibrator was stopped, the positioning cup was lowered, and the wafer was placed on the stage. Then, the stage suction mechanism was operated to suck and hold the wafer to complete the centering.

The result of measuring the chamfer width of the chamfered wafer after performing the chamfering process after the centering is shown in FIG.
Note that the chamfering width in the example was set to a target of a chamfering width of 2.3 mm, which is smaller than that of the conventional chamfering.

(Comparative example)
As in the examples, however, centering was performed manually using tweezers with the naked eye. Further, the chamfering width was chamfered with a target of 2.5 mm which is the same as the chamfering width conventionally performed.
The result of measuring the chamfer width of the chamfered wafer is shown in FIG.

  As shown in FIG. 3, in the chamfering by manual centering in the comparative example, the accuracy of the chamfering width is bad, excessive grinding of the non-defective part and chamfering remaining of the defective part of the electrical characteristics of the outer periphery of the wafer are generated The width variation was large. When the centering device of the present invention is used in the embodiment, the yield is improved by 4.85% by eliminating the chamfer remaining in the defective area, and the target chamfer width is reduced to the end of the defective peripheral area. By setting, the yield was improved by 3.48%, and in the example, the yield was increased by a total of 8.33%.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

10 ... Centering device, 11 ... Tapered surface, 12 ... Vibrator,
13 ... Positioning cup, 14 ... Support, 15 ... Vertical movement mechanism,
20 ... Chamfering device, 21 ... Grinder, W ... Wafer.

Claims (6)

A centering device for centering the wafer when the wafer is supported by a support;
The centering device is arranged at least coaxially with the support, has an upwardly opening tapered surface, and supports a positioning cup for positioning by supporting the peripheral edge of the wafer from below with the tapered surface, and the positioning A vibrator for applying vibration to the cup, wherein the positioning cup moves up and down relatively with respect to the support, and the positioning cup is relative to the support that supports the wafer. The wafer is supported by the taper surface of the positioning cup, and when the wafer is supported, the wafer is positioned by sliding on the taper surface by vibration applied by the vibrator. The positioning cup moves downward relative to the support tool, so that the positioned wafer is supported by the support tool. Centering device wafer, comprising performs a centering of the serial wafer.   The centering device includes a vertical movement mechanism that moves the positioning cup up and down. The vertical movement mechanism moves the positioning cup up and down to move the positioning cup relative to the support. The wafer centering device according to claim 1, wherein   3. The wafer according to claim 1, wherein an upper tapered surface of the positioning cup is inclined within 20 ± 10 degrees with respect to a central axis of the positioning cup. 4. Centering device.   4. The wafer according to claim 1, wherein a material of the tapered surface of the upper opening of the positioning cup is one of a fluororesin, a polyimide resin, and a polyetheretherketone. 5. Centering device.   A chamfering apparatus that chamfers by grinding an outer peripheral portion of a wafer, and at least a support that supports and holds the wafer by suction, and performs centering of the wafer when the wafer is supported by the support 5. The wafer centering device according to claim 1, and a circular grinder that grinds and chamfers the outer peripheral portion of the wafer held by suction by the support. A chamfering device characterized by that. A centering method for centering the wafer when supporting the wafer with a support,
At least a positioning cup that is arranged coaxially with the support and has an upwardly opening tapered surface, and supports the peripheral edge of the wafer from below by the tapered surface for positioning, and applies vibration to the positioning cup. Using a centering device that moves up and down relatively with respect to the support,
The positioning cup is moved upward relative to the support supporting the wafer, and the wafer is supported by the taper surface of the positioning cup, and is applied by the vibrator when the wafer is supported. The wafer is positioned by sliding on the tapered surface by vibration, and then the positioned wafer is supported by the support by moving the positioning cup downward relative to the support. The wafer is centered by the above-described method.

Images