JP2011161610A - Ring-shaped holder for double-ended grinding device, and double-ended grinding device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ring-shaped holder for a double-ended grinding device capable of performing double-ended grinding to obtain a workpiece having more superior nano-topography as compared with conventional nano-topography with superior reproducibility, even when the double-ended grinding using a grinding wheel of a large diameter is performed. <P>SOLUTION: This ring-shaped holder is constituted of at least a detachable carrier including a holding hole for holding the workpiece at a center and a holder part for mounting the carrier. In the carrier, at least two or more radial slits are formed from an outer periphery of the carrier toward the inside. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention has a carrier for holding a workpiece and transmitting rotation to the workpiece in double-side simultaneous grinding of a plate-like workpiece (hereinafter simply referred to as a workpiece) such as a semiconductor wafer or a quartz substrate for exposure original plate. The present invention relates to a ring-shaped holder and a double-head grinding apparatus provided with the same.

For example, in a leading-edge device employing a large-diameter silicon wafer typified by a diameter of 300 mm, in recent years, it has been required to reduce the surface swell component called nanotopography.
Nanotopography is a kind of wafer surface shape, which shows irregularities with a wavelength component of 0.2 to 20 mm, whose wavelength is shorter than warp and warp and whose wavelength is longer than surface roughness. PV (Peak To Valley) ) Value is a very shallow swell component of about 0.1 to 0.2 μm.

  This nanotopography is said to affect the yield of the STI (Shallow Trench Isolation) process in the device process, and a strict level is required for the silicon wafer as the device substrate along with the miniaturization of design rules.

By the way, nanotopography is mainly created in a processing process of a silicon wafer.
In particular, it is easy to deteriorate in a processing method having no reference surface, for example, a wire saw cutting or double-head grinding process, and it is important to improve and manage relative wire meandering in wire cutting and wafer distortion in double-head grinding.

Here, a conventional double-head grinding method will be described. FIG. 12 is a diagram showing an example of a schematic of a conventional double-head grinding device, FIG. 13 is a diagram showing an example of a schematic of a conventional ring-shaped holder for a double-head grinding device, and FIG. It is a figure which shows an example of the outline of the carrier to perform.
As shown in FIG. 12, the double-head grinding apparatus 101 includes a ring-shaped holder 102 that supports a thin plate-like wafer 103 from the outer peripheral side along the radial direction, and is positioned on both sides of the ring-shaped holder 102. A pair of static pressure support members 112 that support the holder 102 in a non-contact manner by hydrostatic pressure from both sides along the axial direction of rotation, and a pair of grindstones 104 that simultaneously grind both surfaces of the wafer 103 supported by the ring-shaped holder 102. It has. The grindstone 104 is attached to a motor 111 so that it can rotate at high speed.

As shown in FIG. 13, the ring-shaped holder 102 includes a carrier 105 having a holding hole 109 for holding a wafer in the center, a holder portion 106 for attaching the carrier 105, and a retaining ring portion 107 for attachment. .
Further, as shown in FIG. 14, the carrier 105 is provided with an attachment hole 108 for attaching to the holder portion with a screw or the like.

  In the double-head grinding using such a device, there are many factors that deteriorate the nanotopography of the workpiece. For example, as shown in Patent Document 1, the position of the ring-shaped holder along the axial direction of rotation is disturbed. It turns out to be a big factor.

JP 2009-190125 A

On the other hand, in recent years, there is a tendency to use a large-diameter grindstone in order to improve grinding efficiency and grinding accuracy. Here, when the grindstone has a large diameter, in order to avoid interference with the grindstone, the ring-shaped holder portion also needs to have a large diameter, and naturally the radial dimension of the carrier also needs to be increased.
Moreover, since it is difficult to reduce the size of the high-precision static pressure support member, the size thereof is relatively large. In order to further improve the accuracy of position control in the rotation axis direction of the ring-shaped holder using such a high-precision hydrostatic support member, the carrier is enlarged to allow the hydrostatic support member to escape to the outer peripheral side. Is required.

  However, even if a large-diameter carrier is used to improve grinding efficiency and grinding accuracy, there is a problem that the improvement range of nanotopography is small. In addition, deterioration of nanotopography of unknown cause was sometimes observed.

  The present invention has been made in view of the above problems, and even when double-headed grinding using a large-diameter grindstone is performed, the nanotopography can obtain a good workpiece with better reproducibility than conventional ones. An object of the present invention is to provide a ring-shaped holder for a double-head grinding apparatus capable of grinding and a double-head grinding apparatus provided with such a ring-shaped holder.

  In order to solve the above-described problems, the present invention is a ring-shaped holder for a double-headed grinding apparatus that includes at least a detachable carrier having a holding hole for holding a workpiece at the center and a holder portion to which the carrier is attached. Thus, the carrier is provided with a ring-shaped holder for a double-head grinding machine, wherein at least two radial slits are formed from the outer periphery to the inner side of the carrier.

In this way, in a ring-shaped holder composed of a carrier having a holding hole for holding a workpiece in the center and capable of detaching at least two radial slits from the outer periphery to the inside, and a holder portion, Even when the diameter of the carrier is increased, the residual strain at the time of manufacture becomes smaller than that of a carrier without a slit, and the flatness of the carrier is improved.
When the workpiece is held by a carrier of a ring-shaped holder made of a carrier having such a small residual strain and improved flatness, the displacement in the thickness direction of the carrier is reduced, and the workpiece nanometer after grinding is reduced. Topography can be improved. Therefore, by using such a ring-shaped holder, the nanotopography of the workpiece after grinding can be improved as compared with the prior art. Therefore, it is possible to provide a ring-shaped work holder for a double-head grinding apparatus that can obtain a good work with good reproducibility compared to the conventional nanotopography.

Here, it is preferable that the carrier has a diameter of the carrier of 1.7 or more with respect to the diameter of the holding hole.
Thus, even if the carrier diameter is 1.7 times or more than the diameter of the holding hole of the workpiece, even if it is a large carrier that has not been heretofore, if the ring-shaped holder of the present invention is used, a workpiece with good nanotopography can be obtained. Can be obtained stably. That is, since the diameter of the carrier can be increased, a double-head grinding device equipped with a high-precision hydrostatic support member can be used, and a ring-shaped holder that contributes to efficiently obtaining a work with improved nanotopography. It can be.

  Further, in the present invention, at least a thin plate-like workpiece having a notch portion on the outer periphery has a protrusion that engages with the notch portion, and can be rotated from the outer periphery side along the radial direction of the workpiece. A double-head grinding apparatus comprising: a ring-shaped holder comprising a simple carrier and a holder portion; and a pair of grinding wheels for simultaneously grinding both surfaces of the workpiece held by the carrier of the ring-shaped holder, A double-head grinding apparatus using the ring-shaped holder according to the present invention is provided.

  In this way, with the double-headed grinding apparatus provided with the ring-shaped holder of the present invention, even when a grindstone with a remarkably large diameter is used, the nanotopography after grinding is a good workpiece. Therefore, it is possible to provide a double-head grinding apparatus that can manufacture a work with high efficiency and high flatness.

Here, it is preferable that a tensile stress directed toward the center of the carrier is applied to the carrier.
In this way, if the double-headed grinding apparatus is equipped with a ring-shaped holder using a carrier to which a tensile stress is applied toward the center direction, the carrier is tightened in the double-headed grinding process. The shake with respect to the rotation axis direction of the workpiece can be further reduced. That is, it is possible to provide a double-head grinding apparatus that can more stably perform double-head grinding of a workpiece having good nanotopography.

  As described above, according to the present invention, the flatness of the carrier can be improved, and the rotation of the carrier for driving the workpiece to rotate (the ring-shaped holder generated when the ring-shaped holder rotates). Carrier deformation along the rotation axis of the ring), and a ring-shaped holder suitable for double-head grinding capable of obtaining a high-precision work with small nanotopography and double-head grinding using the same An apparatus is provided.

It is a figure which shows an example of the outline of the double-head grinding apparatus of this invention. It is a figure which shows an example of the outline of the ring-shaped holder for double-headed grinding apparatuses of this invention. It is a figure which shows an example of the outline of the carrier which comprises the ring-shaped holder for double-head grinding apparatuses of this invention. It is the figure explaining the outline of a mode that the ring-shaped holder for double-head grinding apparatuses of this invention rotates. It is the figure which showed an example of the outline of the static pressure means of the ring-shaped holder suitable for the double-head grinding apparatus of this invention. It is the figure which showed the outline of the measuring method of the rotation blur of the carrier in this invention. It is the figure which showed the outline of the measuring method of the bending rigidity of the carrier in this invention. It is the figure which showed the measurement result of the bending rigidity and rotation blur of the carrier of Example 1 and Comparative Example 1. It is the figure which showed the bending rigidity of the carrier of Example 1 and the comparative example 1, and the relationship of nanotopography. It is the figure which showed the measurement result of the bending rigidity of the carrier of Example 2, and the comparative example 2, and rotation blur. It is the figure which showed the bending rigidity of the carrier of Example 2 and the comparative example 2, and the relationship of nanotopography. It is a figure which shows an example of the outline of the conventional double-head grinding apparatus. It is a figure which shows an example of the outline of the ring-shaped holder for the conventional double-head grinding apparatus. It is a figure which shows an example of the outline of the carrier which comprises the ring-shaped holder for the conventional double-head grinding apparatus.

Hereinafter, the present invention will be described more specifically.
As described above, in order to use a large-diameter grindstone for the purpose of improving grinding efficiency and grinding accuracy, it is necessary to increase the carrier diameter in order to avoid interference between the large-diameter grindstone and the static pressure support member. There is. In spite of using a large-diameter grindstone by increasing the diameter of the carrier having the holding hole for holding the workpiece as described above, there has been a problem that the improvement width of the nanotopography is small or rather deteriorated.
Development of a ring-shaped holder for a double-headed grinding machine that can solve such problems and a double-headed grinding machine equipped with such a holder have been awaited.

  Therefore, the inventors of the present invention, while proceeding with research and research on this large-diameter grindstone, newly reduced the rigidity in the carrier thickness direction with the increase in the carrier diameter, thereby the thickness of the carrier during grinding. We found that the displacement in the direction was large, which greatly affected nanotopography. In the past, this was considered as having no effect on wafer quality such as nanotopography.

Therefore, in order to suppress displacement in the thickness direction of the carrier, a highly rigid metal member was examined.
However, since the carrier needs to have a large diameter and a shape thinner than the workpiece, it is difficult to obtain a sufficient effect. In addition, the residual distortion during carrier fabrication tends to deteriorate flatness, and this has the same effect as the disorder of the carrier position along the rotation axis of the ring holder due to the overall rotational shake, which adversely affects nanotopography. Also found to give.

  And as a result of earnestly examining these two problems of carrier displacement and rotational shake suppression, a carrier having at least two radial slits formed from the outer periphery toward the inner side was used. The present inventors have found that a ring-shaped holder can solve the above-mentioned problems and can also solve the problem of rotation of the carrier. Thus, the present invention has been completed.

  Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto. FIG. 1 is a view showing an example of the outline of the double-head grinding apparatus of the present invention, FIG. 2 is a view showing an example of an outline of the ring-shaped holder for the double-head grinding apparatus of the present invention, and FIG. The figure which shows an example of the outline of the carrier which comprises a holder, FIG. 4 is the figure explaining the outline of a mode that the ring-shaped holder for double-headed grinding apparatuses of this invention rotates.

  As shown in FIGS. 1 and 2, the double-head grinding apparatus 1 of the present invention has a holding hole 14 in which a thin plate-like workpiece 3 having a notch on the outer periphery is formed and a projection 9 that engages the notch is formed. A ring-shaped holder 2 comprising a carrier 5 and a holder portion 6 that can be rotated from the outer periphery along the radial direction of the work 3, and both surfaces of the work 3 held by the carrier 5 of the ring-shaped holder 2. It comprises a pair of grindstones 4 that are ground simultaneously.

  As shown in FIGS. 3 and 4, the double-head grinding apparatus 1 is provided with a drive gear 11 connected to a motor 13 for rotating the ring-shaped holder 2. The ring-shaped holder 2 can be rotated through the internal gear 10 by meshing and rotating the drive gear 11 by the motor 13.

  As shown in FIG. 2, the ring-shaped holder 2 provided in the double-head grinding apparatus 1 includes a carrier 5 that contacts the workpiece 3 and supports the carrier 5 from the outer peripheral side along the radial direction of the workpiece 3. The holder portion 6 to be attached, the retaining ring portion 7 for attachment, and the internal gear 10 used for rotating the ring-shaped holder 2 are provided, and the carrier is attached to the holder portion by screws or the like (not shown) through the attachment holes 8. Yes.

As shown in FIGS. 2 and 3, the carrier 5 is formed with a protrusion 9 that protrudes inward from the edge of the carrier 5, and is called a notch formed at the peripheral edge of the work 3. It conforms to the shape of the notch and can transmit the rotational movement of the ring-shaped holder 2 to the work 3.
A plurality of radial slits 12 are formed in plural from the outer periphery of the carrier 5 toward the inside.

  The number of the slits 12 is 4 or more, the slit width is preferably 0.1 mm to 1 mm, and the slit length is preferably 1/2 to 4/5 of the ring width from the outer periphery to the inner periphery of the carrier 5. However, the present invention is not limited to these, and the effect of the present invention is exhibited if there are at least two or more.

In this way, in the ring-shaped holder composed of at least the carrier and the holder part, in which at least two or more radial slits are formed from the outer periphery toward the inner side, even if the carrier has a larger diameter, The residual strain at the time of processing remaining on the outer periphery of the carrier can be made smaller than that of a carrier without slits, and the flatness can be improved.
And in a double-head grinding machine equipped with such a ring-shaped holder composed of a carrier, the displacement and rotational fluctuation of the carrier in the thickness direction are small when grinding a workpiece, and the value of nanotopography is better than before. It can be set as the apparatus which can obtain a stable workpiece | work stably.
And it can be set as the double-head grinding apparatus which can respond to the enlargement of a grindstone diameter, and becomes a double-head grinding apparatus which can obtain a workpiece | work with high efficiency and high flatness.

Here, the ratio of the diameter of the carrier to the diameter of the work holding hole can be 1.7 or more.
For example, when the workpiece diameter is 300 mm, the carrier outer diameter is 350 mm and the workpiece holding hole diameter is 300.4 mm. On the other hand, in the carrier in the ring-shaped holder of the present invention, for example, the carrier outer diameter can be 520 mm and the work holding hole diameter can be 300.4 mm. In this case, the ratio of the carrier diameter to the diameter of the holding hole is 520 / 300.4≈1.73.
When the workpiece diameter is 200 mm, for example, conventionally, the carrier outer diameter is 250 mm and the workpiece holding hole diameter is 200.4 mm. In the carrier in the ring-shaped holder of the present invention, the carrier outer diameter can be 350 mm, and the work holding hole diameter can be 200.4 mm. In this case, the ratio of the carrier diameter to the diameter of the holding hole is 350 / 200.4≈1.75.

Even if the carrier has a diameter that is at least 1.7 times the diameter of the work holding hole, as long as at least two slits are provided, displacement in the thickness direction of the carrier and rotational shake are small. Can improve the nanotopography of the workpiece.
For this reason, in order to improve grinding efficiency and grinding accuracy, the diameter of the grindstone is increased, or the bearing of the rotating shaft of the ring-shaped holder is moved outside to increase the accuracy of the position along the axial direction of the ring-shaped holder. Since the diameter of the carrier can be increased in order to increase the accuracy of the mechanism for further enhancement, double-head grinding that can further improve the nanotopography of the workpiece can be performed.

  The upper limit of the ratio is not particularly limited. However, when the ratio is larger than 3.5 times, the effect of providing at least two slits on the carrier is reduced, and there is a problem that the reduction in rigidity becomes conspicuous. Furthermore, since the carrier becomes larger than necessary and there is a problem in terms of cost, it is desirable that the carrier be 3.5 times or less.

Further, the carrier may be one to which a tensile stress directed toward the center of the carrier is applied.
For example, after the heated carrier is attached to the holder portion and then cooled to room temperature, tension (tensile stress) can be applied to the carrier, and displacement of the carrier during grinding can be further suppressed. Of course, the method for applying the tensile stress toward the center of the carrier is not limited to this.
Thus, since the ring-shaped holder of the present invention has a slit formed in the carrier, it is possible to apply tension without loss to the inner peripheral portion of the carrier, thereby further suppressing the displacement of the carrier during grinding. The flatness of the carrier can be further increased. Then, the flatness of the carrier is improved, and the rotational shake of the carrier can be suppressed, the nanotopography is further improved, and the product yield can be further improved.

Here, the support method for supporting the ring-shaped holder 2 of the present invention on the double-head grinding apparatus 1 is not particularly limited. For example, as shown in Patent Document 1, the axial direction of rotation is as much as possible. It is desirable to eliminate disturbances along the position.
Therefore, as shown in FIG. 5, it is desirable that the ring-shaped holder 2 be rotated with high accuracy using a static pressure bearing 21. As the static pressure means, it is preferable to use a fluid such as water or air.

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 1, Comparative Example 1)
A double-sided grinding of a silicon wafer having a diameter of 300 mm was performed using a double-sided grinding machine 1 for workpieces as shown in FIG.
First, a carrier made of SUS having an outer diameter of 520 mm was prepared, and double-sided grinding of a silicon wafer was performed using a ring-shaped holder that did not form a slit (Comparative Example 1).
Thereafter, the carrier used in the above-mentioned Comparative Example 1 has a slit of 45 mm in width and 0.5 mm in length and 3/4 of the ring width from the outer periphery to the inner periphery of the carrier, for a total of 8 slits. Double-head grinding was performed using a ring-shaped holder using the provided one (Example 1).
As for the static pressure means of the ring-shaped holder, an air bearing was used, and the position control along the axial direction of rotation was within 5 μm. And the grindstone used the SD # 3000 grindstone (Vitrified grindstone by Allied Material Co., Ltd.) which consists of a diameter 160mm and vitrified bond. The grinding amount of the silicon wafer was 30 μm.

  Also, the carrier when the carrier is attached to the ring-shaped holder before and after the slit is formed at various temperatures, such as room temperature (25 ° C.), 30 ° C., 45 ° C., and 60 ° C. And the displacement per unit load of the carrier (hereinafter referred to as bending rigidity) were investigated. The result is shown in FIG.

Here, FIGS. 6 and 7 show the definition of the rotational shake of the carrier and the bending rigidity of the carrier and the measuring method.
As shown in FIG. 6, the rotational shake of the carrier is a measurement of the PV value of the carrier surface when a non-contact eddy current type sensor 31 is installed at the reference position and the carrier is rotated once. The larger the value, the larger the displacement of the rotating carrier, and the smaller the value, the smaller the displacement.
As shown in FIG. 7, the bending rigidity of the carrier is measured by measuring the amount of carrier displacement when a load of 25 g is applied from the opposite side of the sensor 31 using an eddy current type sensor 31. The amount of displacement is calculated, and the larger the value, the stronger the deformation.

  As shown in FIG. 8, it was found that by performing the slit processing, the bending rigidity of the carrier is improved and the rotational shake is reduced. Further, it was found that the heating temperature at the time of attachment increases, that is, the tensile stress toward the center of the carrier is applied, and the effect increases as the stress increases. In addition, the value of the bending rigidity and rotation blur of each figure shows a relative value.

Next, FIG. 9 shows the relationship between nanotopography of a silicon wafer and bending rigidity of a carrier when mirror polishing is performed after double-head grinding in Example 1 and Comparative Example 1.
As shown in FIG. 9, the nanotopography is improved as the bending rigidity is increased. However, it was found that the nanotopography can be improved more in Example 1 in which a slit is formed in the carrier.

(Example 2, comparative example 2)
Prepare a carrier made of SUS having an outer diameter of 520 mm different from Example 1 and Comparative Example 1, and perform double-head grinding of a silicon wafer with a difference in the presence or absence of slits as in Example 1 and Comparative Example 1, We evaluated the rotational vibration of the carrier and the bending rigidity of the carrier.
In addition, the carrier used in Example 2 and Comparative Example 2 was intentionally selected to have a large rotational shake relative to the carrier of Example 1 and Comparative Example 1.

As shown in FIG. 10, it is understood that the bending rigidity of the carrier is improved and the rotational shake is reduced by performing the slit processing on the carrier having a larger rotational shake than in the first embodiment and the comparative example 1. It was. It was also found that the above effect was increased by further increasing the heating temperature.
FIG. 10 is a diagram showing the measurement results of the bending rigidity and rotational shake of the carriers of Example 2 and Comparative Example 2.

FIG. 11 shows the relationship between the nanotopography and the bending rigidity of the carrier when Example 2 and Comparative Example 2 are subjected to mirror polishing after double-head grinding.
As shown in FIG. 11, it was found that the nanotopography was improved with an increase in bending rigidity, and the nanotopography of the silicon wafer was improved in Example 2 where the slit processing was performed. Compared with FIG. 9, the value of nanotopography is high, but it was found that the effect of the present invention can be exhibited even with a carrier with large rotational fluctuation.

From the results shown in FIGS. 8 to 11, it can be seen that the bending rigidity is increased by carrying out the radial slit processing on the carrier, and further, the rotational shake of the carrier is reduced, so that the nanotopography can be improved by these two synergistic effects. It was.
It has also been found that the above effect can be further enhanced by heating and attaching, that is, by using a ring-shaped holder provided with a carrier to which a tensile stress is applied to the inner periphery.

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

1 ... Double-head grinding machine,
DESCRIPTION OF SYMBOLS 2 ... Ring-shaped holder, 3 ... Workpiece, 4 ... Grinding stone, 5 ... Carrier, 6 ... Holder part, 7 ... Holding ring, 8 ... Mounting hole, 9 ... Projection part, 10 ... Internal gear, 11 ... Drive gear, 12 ... Slit, 13 ... Motor (for holder), 14 ... Holding hole,
21 ... hydrostatic bearing,
31 ... Eddy current sensor.

Claims (4)

At least a ring-shaped holder for a double-head grinding apparatus comprising a detachable carrier having a holding hole for holding a workpiece in the center, and a holder portion to which the carrier is attached,
A ring-shaped holder for a double-headed grinding machine, wherein the carrier is formed with at least two radial slits from the outer periphery to the inner side of the carrier.   2. The ring-shaped holder for a double-head grinding apparatus according to claim 1, wherein the carrier has a diameter of the carrier of 1.7 or more with respect to the diameter of the holding hole. At least a thin plate-like workpiece having a cutout portion on the outer periphery, and a carrier that can be rotated from the outer peripheral side along the radial direction of the workpiece and a holder portion, having a protrusion that engages with the cutout portion. A double-head grinding apparatus comprising a ring-shaped holder and a pair of grindstones for simultaneously grinding both surfaces of the workpiece held by the carrier of the ring-shaped holder,
A double-head grinding apparatus using the ring-shaped holder according to claim 1 or 2 as the ring-shaped holder.   The double-head grinding apparatus according to claim 3, wherein the carrier is applied with a tensile stress toward the center of the carrier.

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