JP7200898B2 - Double-sided polishing method of workpiece - Google Patents

Description

The present invention relates to a method for polishing both sides of a work.

In the manufacture of semiconductor wafers such as silicon wafers, which are typical examples of workpieces to be polished, a double-sided polishing process is used to polish both the front and back surfaces of the wafer at the same time in order to obtain higher-precision wafer flatness and surface roughness. It is generally adopted (for example, Patent Document 1).

International Publication No. 2014-2467

By the way, the shape of the wafer is required to be controlled in various ways according to its application. It may be desired to roll off

In such a case, for example, by performing double-side polishing using a polishing pad having a low hardness, the outer periphery of the wafer may be intentionally rolled off by elastic deformation of the polishing pad.

However, when a polishing pad having a low hardness is used, there is a possibility that problems such as a decrease in flatness (for example, GBIR) of the entire surface of the wafer may occur. Therefore, there is a demand for another technique that can intentionally control the outer peripheral shape of the wafer. Such a problem can occur not only in wafers but also in workpieces subjected to double-side polishing in general.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for polishing both sides of a work, which can intentionally control the outer peripheral shape of the work.

The gist and configuration of the present invention are as follows.
The work polishing method of the present invention comprises:
A double-sided polishing method for a workpiece, comprising holding the workpiece in a carrier plate having one or more holding holes for holding the workpiece and performing double-sided polishing of the workpiece,
acquiring a relationship between an inner diameter of the holding hole and an edge roll-off amount of the workpiece;
determining the inner peripheral diameter of the holding hole based on the desired edge roll-off amount and the acquired relationship between the inner peripheral diameter of the holding hole and the edge roll-off amount of the workpiece;
and a step of polishing both sides of the workpiece using the carrier plate having the holding hole with the determined inner diameter.

Here, "edge roll-off" means that the outer peripheral portion of the workpiece is sagging and the thickness of the outer peripheral portion is reduced. The "edge roll-off amount" is the amount of sagging in the outer peripheral portion of the work, and the larger the edge roll-off amount, the greater the sagging in the outer peripheral portion of the work, and therefore the thinner the outer peripheral portion.

ESFQR, for example, can be used as an index of the “edge roll-off amount”. “ESFQR” is an index that indicates the flatness of a wafer as defined in the SEMI standard, and is a fan shape formed in the peripheral region of the entire circumference of the wafer (72 equal divisions in the circumferential direction within a range of 30 mm from the outer circumference of the wafer). The thickness of each region of the wafer is obtained by calculating the sum of the absolute values of the maximum displacement amount from the reference plane obtained by the method of least squares. "ESFQRmax" is the maximum value among them. However, when the workpiece is a wafer, the outer edge may be chamfered, and therefore, for example, a 1 mm area in the radial direction from the outer edge can be excluded as the edge exclusion area.
In the case of a wafer whose periphery rolls off, the larger the "ESFQR", the larger the "edge roll-off amount".

Further, when the holding hole has an inserter (for example, made of resin) on the inner peripheral surface of the holding hole, the "inner peripheral diameter" refers to the inner peripheral diameter of the inserter.

Here, it is preferable that the edge roll-off amount is an edge roll-off amount in a sizing state.
The "fixed size state" refers to a state in which both sides of the workpiece are polished until the thickness of the workpiece is the same as the thickness of the carrier plate.

Generally, in double-sided polishing, the front and back surfaces of a workpiece are polished simultaneously using a polishing pad that is an elastic body. existing) is being polished. That is, as shown in FIG. 5, at the initial stage of polishing (state A), the entire surface shape of the workpiece is an upwardly convex shape, and a large sagging shape is seen on the outer periphery of the workpiece, and the edge roll-off amount is large. . At this time, the thickness of the work is sufficiently thicker than the thickness of the carrier plate. As the polishing progresses (state B), the overall shape of the workpiece becomes substantially flat, and the edge roll-off amount of the outer circumference of the wafer becomes small. At this time, the thickness of the workpiece and the thickness of the carrier plate are almost equal. After that, as the polishing progresses (state C), the shape of the workpiece gradually becomes concave at the center, and the outer periphery of the workpiece becomes rounded. In state C, the carrier plate is thicker than the workpiece. State B described above is the sizing state.

Moreover, the determined inner peripheral diameter is preferably 1 mm to 5 mm larger than the diameter of the workpiece.

Further, the double-sided polishing is performed using a polishing pad,
The surface hardness (ASKER C) of the polishing pad is preferably 70-90.
Here, the "surface hardness of the polishing pad (ASKER C)" is measured by an ASKER C hardness tester.

Also, the workpiece is preferably a silicon wafer.

Further comprising the step of acquiring the relationship between the inner diameter of the holding hole and the surface roughness of the end surface of the workpiece,
In the step of determining the inner peripheral diameter of the holding hole, the inner peripheral diameter of the holding hole is determined based on the desired surface roughness of the end face of the work, and the acquired inner peripheral diameter of the holding hole and the end face of the work. is preferably determined based on the relationship between the surface roughness of

According to the present invention, it is possible to provide a method for polishing both sides of a work, which can intentionally control the outer peripheral shape of the work.

1 is a schematic diagram of an example of a double-side polishing apparatus used in a method for polishing both sides of a workpiece according to an embodiment of the present invention; FIG. 1 is a flowchart of a method for polishing both sides of a workpiece according to one embodiment of the present invention; FIG. FIG. 4 is a diagram showing the relationship between the inner diameter of holding holes of a carrier plate and ESFQRmax. FIG. 5 is a diagram showing the relationship between the inner diameter of a holding hole of a carrier plate and the surface roughness Ra of the end surface of a work; It is a figure for demonstrating a sizing state.

Embodiments of the present invention will be exemplified in detail below with reference to the drawings.

<Double-side polishing device for work>
FIG. 1 is a schematic diagram of an example of a double-sided polishing apparatus used in a double-sided polishing method for a workpiece according to an embodiment of the present invention.

The double-side polishing apparatus 100 has the same configuration as a double-side polishing apparatus normally used for double-side polishing of a work (wafer W), except that the inner diameter of the holding hole 1 is determined by a method described later. can do. An example thereof will be described below.

As shown in FIG. 1, a workpiece double-side polishing apparatus 100 of the present embodiment has at least one (one in the illustrated example) holding a workpiece (a wafer W (a silicon wafer as an example) in the present embodiment). It has one or more (one in the example shown) carrier plates 2 with holes 1 .
As shown in FIG. 1, the double-sided polishing apparatus 100 of this example includes a rotating surface plate 3 having an upper surface plate 3a and a lower surface plate 3b opposed thereto, and a sun gear 4 provided at the center of rotation of the rotating surface plate 3. , and an internal gear 5 provided in an annular shape on the outer peripheral portion of the rotating platen 3 .
As shown in FIG. 1, polishing pads 6 are attached to the opposing surfaces of the upper and lower rotating surface plates 3, that is, the lower surface of the upper surface plate 3a and the upper surface of the lower surface plate 3b. It is

Further, as shown in FIG. 1, the carrier plate 2 is provided between the upper surface plate 3a and the lower surface plate 3b. In the illustrated example, the double-side polishing apparatus 100 has only one carrier plate 2, but it may have a plurality of carrier plates 2, and the number of holding holes 1 may be one or more. If so, it may be two or more. In the illustrated example, a workpiece (wafer W) is held in the holding hole 1 .
In this example, the diameter of the workpiece (wafer W) to be polished by the double-sided polishing apparatus 100 is 300 mm, but it is not limited to this case. Further, when the work is a wafer W, the crystal orientation, conductivity type, etc. are not particularly limited.

Here, the double-side polishing apparatus 100 is a planetary gear type double-side polishing apparatus that can cause the carrier plate 2 to perform planetary motion of revolution and rotation by rotating the sun gear 4 and the internal gear 5. . That is, while the polishing slurry is being supplied, the carrier plate 2 is moved in a planetary motion, and at the same time, the upper surface plate 3a and the lower surface plate 3b are rotated relative to the carrier plate 2, so that the upper and lower rotating surface plates 3 are coated with a cloth. Both sides of the work (wafer W) held in the holding holes 1 of the carrier plate 2 can be slid on both sides of the work (wafer W) to simultaneously polish both sides of the work (wafer W).

Here, in the present embodiment, the surface hardness (ASKER C) of the polishing pad 6 is preferably 70-90.

Further, the inner peripheral surface of the carrier plate 2 may or may not have an inserter (made of resin, for example).

As will be described later, the inner diameter of the holding hole 1 of the carrier plate 2 is determined through a predetermined process, and the inner diameter is preferably 1 mm to 5 mm larger than the diameter of the workpiece. In this example, since the work is a wafer with a diameter of 300 mm, the inner diameter of the holding hole 1 of the carrier plate 2 is preferably 301 mm to 305 mm.

<Method of polishing both sides of workpiece>
FIG. 2 is a flow diagram of a method for polishing both sides of a workpiece according to one embodiment of the present invention.
As shown in FIG. 2, in the method for polishing both sides of a work according to the present embodiment, first, the relationship between the inner diameter of the holding hole 1 and the edge roll-off amount of the work (wafer W) is obtained (step S101: 1 step).

Here, the relationship between the inner diameter of the holding hole 1 and the edge roll-off amount of the workpiece (wafer W) will be described in detail. FIG. 3 is a diagram showing the relationship between the inner diameter of the holding hole of the carrier plate and ESFQRmax. Also, as described above, the ESFQR is one of the indices of the edge roll-off amount. The ESFQR in FIG. 3 shows the ESFQR in the sizing state. Experimental details regarding FIG. 3 are described later in the Examples.

As a result of intensive studies by the present inventors to solve the above problems, as shown in FIG. 3, the edge roll-off amount (ESFQRmax in FIG. Turned out to be big.
Here, in the initial stage of polishing (state A in FIG. 5), since the wafer is thicker than the carrier plate, the peripheral portion of the wafer is directly polished by the elastic polishing pad. As the polishing progresses from there and the thickness of the wafer becomes almost the same as the thickness of the carrier plate, the outer periphery of the wafer is protected by the carrier plate, and the polishing pad acts on the outer periphery of the wafer. decreases, the amount of polishing at the central portion of the wafer becomes relatively large, and the wafer becomes flat (state B). While being protected, the central portion of the wafer is polished, so that the central portion of the wafer becomes recessed (state C).
For this reason, when the gap between the inner peripheral surface of the holding hole and the workpiece (wafer W) increases, the above-described effect of protecting the outer peripheral portion of the wafer by the carrier plate and reducing the polishing amount of the outer peripheral portion decreases. In addition, the larger the inner diameter of the holding hole, the greater the amount of polishing slurry that intervenes and the more the polishing is promoted. is considered to increase the edge roll-off amount.

Thus, there is a correlation between the inner diameter of the holding hole 1 and the edge roll-off amount of the workpiece (wafer W). increases, the edge roll-off amount increases.
Therefore, in step S101 (first step), the inner peripheral diameter of the holding hole 1 when the work (wafer W) is polished on both sides (for example, when the work (wafer W) is polished to a fixed dimension), and the work ( With regard to the edge roll-off amount of the wafer W), by preparing a large number of sufficient data in advance, the data itself, the data subjected to statistical processing, etc., or the holding hole 1 based on the data and the edge roll-off amount of the work (wafer W) can be acquired as the relationship between the inner circumference diameter of the holding hole and the edge roll-off amount of the work.
As an example, the relationship between the inner diameter of the holding hole and the edge roll-off amount of the workpiece can be stored in a computer having a storage unit (memory or the like), or can be stored by a computer having a communication unit or the like. You may make it transmit/receive related information. The information can be updated in real time or timely.

Next, as shown in FIG. 2, in the present embodiment, based on the desired edge roll-off amount and the acquired relationship between the inner diameter of the holding hole and the edge roll-off amount of the workpiece, the Determine the inner diameter (step S102: second step).
As described above, there is a correlation between the inner diameter of the holding hole 1 and the edge roll-off amount of the workpiece (wafer W). , the edge roll-off amount increases, which is obtained in step S101 (first step).
Therefore, by determining the desired edge roll-off amount, the obtained relationship between the inner diameter of the holding hole and the edge roll-off amount of the work can be used to determine the inside diameter of the holding hole of the carrier plate used for double-sided polishing. A circumference can be determined.
As an example, in step S101 (first step), the relationship between the inner diameter of the holding hole and the edge roll-off amount is mathematically represented (for example, by a linear expression). When obtained as a relationship with the roll-off amount, the inner diameter of the holding hole of the carrier plate used for double-side polishing can be obtained by substituting the desired edge roll-off amount into the above formula. Although not particularly limited, since the inner diameter of the carrier plate is often an integer value, it can be obtained as an integer value by rounding off or the like. Alternatively, the relationship between the inner diameter of the holding hole and the edge roll-off amount of the workpiece can be used as is, and the desired edge roll-off amount (and the edge roll-off amount close thereto) can be achieved. Using the obtained data of the holding holes of the carrier plate, the inner diameter of the holding holes of the carrier plate used for double-side polishing can be determined. For example, the average value of the carrier plate retention hole data that was able to achieve the desired amount of edge roll-off (and close to it) can be calculated. Similarly, although not particularly limited, since the inner diameter of the carrier plate is often an integer value, it can be obtained as an integer value by rounding off or the like. Alternatively, the inner peripheral diameter of the largest number of holding holes of the carrier plate that achieved the desired edge roll-off amount (and the edge roll-off amount close to it) is the number of holding holes of the carrier plate used for double-sided polishing. It can also be determined as the inner diameter.
It should be noted that the same process can be carried out in the case where the relationship between the inner peripheral diameter of the holding hole and the edge roll-off amount of the work is obtained by statistically processing the above data.
As an example, the determination can be made by a computer having a calculator.

Next, as shown in FIG. 2, in this embodiment, the workpiece (wafer W) is double-sided polished using a carrier plate having holding holes with the determined inner diameter (step S103: third step). The double-side polishing in step S103 (third step) can be performed using, for example, the double-side polishing apparatus 100 described with reference to FIG. At this time, it is preferable to replace the carrier plate of the double-sided polishing apparatus with a carrier plate having holding holes with the determined inner diameter. You can prepare a new one. Double-sided polishing can be performed by a normal method. As an example, as described above, while supplying the polishing slurry, the carrier plate 2 is caused to undergo planetary motion, and at the same time, the upper surface plate 3a and the lower surface plate 3b are rotated relative to the carrier plate 2, thereby vertically Both surfaces of the work (wafer W) held in the holding holes 1 of the carrier plate 2 can be slid on both sides of the work (wafer W) so that both sides of the work (wafer W) can be polished at the same time.
A method for polishing both sides of a workpiece according to the present embodiment will be described below.

According to the method for polishing both sides of a workpiece of the present embodiment, a workpiece (wafer The outer shape of W) can be intentionally controlled. That is, since the holding hole having the determined inner diameter corresponds to the desired edge roll-off amount, the outer peripheral shape of the workpiece (wafer W) is intentionally controlled. According to the method for polishing both sides of a workpiece of the present embodiment, the polishing pad used has a surface hardness (ASKER C) of 70 to 90. There is no loss due to replacement of materials, and the problem of reduction in flatness (GBIR, etc.) of the entire surface of the work (wafer W) caused by using a polishing pad with low hardness is not caused. Furthermore, according to the double-side polishing method of the workpiece of the present embodiment, the contact area between the workpiece (wafer W) and the inner peripheral surface of the holding hole of the carrier plate is reduced, and the rotation of the workpiece (wafer W) is promoted. Also, as will be shown in Examples described later, the surface quality of the end face can be improved by reducing the roughness of the end face of the workpiece (wafer W).

Here, the edge roll-off amount (the work edge roll-off amount in step S101 and the expected edge roll-off amount in step S102) is preferably the edge roll-off amount in a fixed size state. This is because there is no adverse effect on the flatness of the entire surface of the workpiece, etc., compared to the case where polishing is further performed from the sizing state in order to obtain the desired edge roll-off amount. On the other hand, even in the state before the sizing state (state A in FIG. 5), a larger edge roll-off amount (sagging amount) can be obtained.

Also, the determined inner peripheral diameter is preferably 1 mm to 5 mm larger than the diameter of the workpiece. When the determined inner diameter is larger than the diameter of the workpiece by 1 mm or more, the gap between the inner peripheral surface of the holding hole and the workpiece (wafer W) is increased more reliably, and the outer peripheral portion is protected by the carrier plate. On the other hand, it is possible to obtain the effect of weakening the above-mentioned effect and increasing the amount of polishing slurry intervening. , the workpiece can be more reliably held in the holding hole.
Although not particularly limited, the diameter of the workpiece and the inner peripheral diameter of the workpiece holding hole of the carrier plate are often integer values, so the determined inner peripheral diameter should be an integer value within the above range. is also preferred.
As an example, when the diameter of the workpiece is 300 mm, the inner diameter of the workpiece holding hole of the carrier plate is preferably 301 mm, 302 mm, 303 mm, 304 mm, or 305 mm.

Double-sided polishing is performed using a polishing pad, and the surface hardness (ASKER C) of the polishing pad is preferably 70-90. Compared to the case of exchanging to a polishing pad with a low hardness, there is no loss of material exchange, and the use of a polishing pad with a low hardness reduces the flatness (GBIR, etc.) of the entire surface of the work (wafer W). This is because it does not cause the problem of

It is also preferable to measure the edge roll-off amount (for example, ESFQR) of the outer peripheral portion of the workpiece when the double-side polishing in step S103 (third step) is completed. As a result, the result can be fed back to update the data, and the precision for obtaining the desired edge roll-off amount in the next double-sided polishing can be improved.

Here, the step of obtaining the relationship between the inner peripheral diameter of the holding hole and the surface roughness of the end face of the workpiece is further included, and in the step of determining the inner peripheral diameter of the holding hole, the inner peripheral diameter of the holding hole It is preferable that it is determined based on the surface roughness of the end face of the work to be measured, and the acquired relationship between the inner peripheral diameter of the holding hole and the surface roughness of the end face of the work.
As shown in FIG. 4, which will be described later, there is a correlation that the larger the inner peripheral diameter of the work holding hole of the carrier plate, the smaller the surface roughness Ra of the end surface of the work after polishing. Considering both the roll-off amount and the desired surface roughness of the end face of the work, the appropriate inner diameter of the work holding hole of the carrier plate is determined, and the outer peripheral shape of the work and the surface roughness of the end face of the work are determined. can be intentionally controlled at the same time.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, the edge roll-off amount of the outer peripheral portion is not limited to the case where ESFQR is used as an index.
Examples of the present invention will be described below, but the present invention is not limited to the following examples.

Carrier plates with different inner diameters of workpiece holding holes (inner diameters of 301 mm, 302 mm, 303 mm, 304 mm, and 305 mm) were prepared, and a wafer with a diameter of 300 mm was polished using a double-sided polishing apparatus as shown in FIG. , double-sided polishing was performed.
After performing double-sided polishing, the ESFQR was measured by excluding an area of 1 mm in the radial direction from the outer peripheral edge of the wafer as an edge exclusion area, using a flatness measurement device (manufactured by KLA-Tencor: Wafersight2), and the maximum value ( ESFQRmax) was determined.
FIG. 3 and Table 1 show the measurement results. As a result, it was found that the larger the inner diameter, the larger the ESFQRmax, and the edge roll-off could be achieved.

As shown in FIG. 3 and Table 1, there is a correlation between the inner diameter of the workpiece holding hole and the edge roll-off amount of the wafer. It can be seen that there is a relationship in which the edge roll-off amount increases as .
Therefore, by acquiring this relationship, it is possible to determine the inner diameter of the holding hole of the workpiece based on the desired edge roll-off amount and the acquired relationship.

Next, the roughness Ra of the end surface of the wafer after double-side polishing was measured using a Chapman MPS.
FIG. 4 and Table 2 show the measurement results.

As shown in FIG. 4 and Table 2, it can be seen that the use of a carrier plate having a large inner diameter of the work holding hole reduces the surface roughness Ra and improves the surface quality.

100: double-sided polishing device,
1: holding hole,
2: carrier plate,
3: rotating surface plate,
3a: upper surface plate,
3b: lower surface plate,
4: Sun gear,
5: internal gear,
6: polishing pad,
W: Wafer

Claims (6)

A double-sided polishing method for a workpiece, comprising holding the workpiece in a carrier plate having one or more holding holes for holding the workpiece and performing double-sided polishing of the workpiece,
acquiring a relationship between an inner diameter of the holding hole and an edge roll-off amount of the workpiece;
determining the inner peripheral diameter of the holding hole based on the desired edge roll-off amount and the acquired relationship between the inner peripheral diameter of the holding hole and the edge roll-off amount of the workpiece;
and a step of performing double-side polishing of the work by using the carrier plate having the holding hole with the determined inner diameter. 2. The method of polishing both sides of a workpiece according to claim 1, wherein said edge roll-off amount is an edge roll-off amount in a constant size state. 3. The method of polishing both sides of a workpiece according to claim 1, wherein the determined inner peripheral diameter is 1 mm to 5 mm larger than the diameter of the workpiece. The double-sided polishing is performed using a polishing pad,
4. The method for polishing both sides of a workpiece according to claim 1, wherein said polishing pad has a surface hardness (ASKER C) of 70-90. The double-sided polishing method for a workpiece according to any one of claims 1 to 4, wherein the workpiece is a silicon wafer. further comprising acquiring a relationship between the inner diameter of the holding hole and the surface roughness of the end face of the workpiece;
In the step of determining the inner peripheral diameter of the holding hole, the inner peripheral diameter of the holding hole is determined based on the desired surface roughness of the end face of the work, and the acquired inner peripheral diameter of the holding hole and the end face of the work. The method for polishing both sides of a work according to any one of claims 1 to 5, wherein the determination is made based on the relationship between the surface roughness and the surface roughness.

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