JP6977657B2 - How to store carriers for double-sided polishing equipment and how to polish double-sided wafers - Google Patents

Description

The present invention relates to a method for storing a carrier for a double-sided polishing apparatus used when polishing both sides of a wafer at the same time, and to a method for polishing both sides of a wafer using the carrier.

Since the double-sided polishing machine simultaneously polishes both sides of, for example, about 5 wafers per batch, a carrier for a double-sided grinding machine having the same number of holding holes as the number of wafers is installed on the surface plate. Further, the wafer is held by the holding holes of the carrier, the wafer is sandwiched from both sides by the polishing cloth provided on the upper and lower surface plates, and polishing is performed while supplying the polishing agent to the polishing surface.

The carrier for double-sided polishing is formed to have a thickness thinner than that of the wafer, and is made of, for example, a metal such as stainless steel or titanium, or a hard resin such as glass epoxy. Here, the metal carrier has a resin insert material inside the wafer holding hole in order to prevent the inner peripheral portion of the wafer holding hole from coming into contact with the outer peripheral portion of the wafer and damaging it. This insert material is formed by fitting or injection molding. Here, since the inner peripheral portion of the insert material is in contact with the outer peripheral portion of the wafer, it is important for creating the edge shape of the wafer. It is desired that the insert material has the same height as the carrier body, and the thickness of the insert material is preferably constant. When the insert material protrudes from the metal part, the protruding part needs to be processed by carrier rising polishing (see Patent Document 1). This determines the initial thickness of the insert material.

Japanese Unexamined Patent Publication No. 2016-198864

Conventionally, when a carrier is taken out of the polishing apparatus for conditioning of the polishing cloth or replacement of the polishing cloth, which is performed regularly during wafer processing, the carrier is temporarily stored in water or in a dry state to manage the carrier. (See Fig. 9).

However, when the insert material is stored in water or in a dry state, swelling / shrinkage may occur. When swelling or shrinkage occurs, the thickness of the insert material changes, which has a problem of affecting the flatness of the wafer.

The present invention has been made to solve the above problems, and suppresses changes in the thickness of the insert material due to swelling and shrinkage between the time of storing the carrier and the time of double-sided polishing of the wafer, and suppresses the change in the thickness of the insert material after storage. It is an object of the present invention to provide a storage method for a carrier for a double-sided polishing apparatus, which improves the flatness of a wafer after polishing when the wafer is polished using a carrier.

In order to achieve the above-mentioned problems, in the present invention, a carrier main body, which is used in a double-sided polishing apparatus having an upper and lower surface plates to which a polishing cloth is attached and has holding holes for holding a wafer, and the holding holes are provided. A method for storing a carrier having a ring-shaped insert material which is arranged along the inner circumference and has an inner peripheral surface in contact with the peripheral edge of the wafer, wherein the carrier is used as a polishing agent for double-sided polishing of the wafer. Alternatively, a method for storing a carrier for a double-sided polishing apparatus, which comprises storing in an alkaline solution, is provided.

In the storage method of the carrier for the double-sided polishing apparatus of the present invention, the change in the thickness of the insert material due to swelling and shrinkage between the time of storing the carrier and the time of double-sided polishing of the wafer is suppressed, and after storage. When the wafer is polished using the carrier of the above, the flatness of the wafer after polishing can be improved.

At this time, as the abrasive and the alkaline solution, those having a pH of 10 or more and 12 or less can be used.

In the present invention, an abrasive or an alkaline solution in such a pH range can be suitably used for storage of the carrier.

Further, as the material of the insert material, a resin having a water absorption rate of 0.1% or more can be used.

When a resin having a water absorption rate of 0.1% or more is used as the material of the insert material, in the conventional method, the change in the thickness of the insert material due to swelling and shrinkage becomes more remarkable during storage and double-sided polishing of the wafer. Will end up. Therefore, it is possible to further enjoy the advantage of the present invention that the change in the thickness of the insert material due to swelling and shrinkage can be suppressed between the time of storing the carrier and the time of double-sided polishing of the wafer.

Further, as the material of the insert material, a resin made of any one of vinyl resin, polystyrene resin, acrylic resin, polyamide resin, polyacetal, polycarbonate, polyethylene terephthalate, and fluorine resin can be used.

In the present invention, these resins can be suitably used as the material of the insert material.

The present invention also provides a double-sided polishing method for a wafer, which comprises storing the carrier by any of the above methods and using the stored carrier to polish the wafer.

As described above, the carrier stored by the carrier storage method of the present invention can suppress the change in the thickness of the insert material due to swelling and shrinkage between the time of storing the carrier and the time of double-sided polishing of the wafer. Therefore, by polishing the wafer using this stored carrier, it is possible to improve the initial flatness of the edge portion of the wafer, which is most affected by the change in the thickness of the insert material.

In the carrier storage method of the present invention, since the carrier is stored in the polishing agent or alkaline solution used for double-sided polishing of the wafer, the carrier insert material is kept in the same state during storage and during the actual double-sided polishing process. be able to. This makes it possible to suppress swelling and shrinkage of the insert material during storage. Further, since the stored carrier is used in the double-sided polishing method of the wafer of the present invention, the initial flatness of the edge portion at the start of reworking of the wafer can be improved.

It is a flow chart which shows the flow of the carrier storage method and the double-sided polishing method of a wafer of this invention. It is a graph which shows the swelling rate of an insert material. It is a graph which shows the transition of the flatness for each batch when the wafer is double-sided polished using the carrier after storage in an Example and a comparative example. It is a graph which shows the initial flatness at the time of double-sided polishing of a wafer using the carrier after storage in an Example and a comparative example. It is a schematic diagram which showed an example of the carrier for the double-sided polishing apparatus which can be used in this invention. It is a schematic diagram which showed an example of the double-sided polishing apparatus which can use the carrier for the double-sided polishing apparatus in this invention. It is a schematic diagram for demonstrating ESFQR in a wafer. It is a schematic diagram which enlarged one of the rectangular areas shown in FIG. 7. It is a flow chart which shows the flow of the conventional carrier storage method and the double-sided polishing method of a wafer.

As described above, after polishing when the wafer is polished using the carrier after storage by suppressing the change in the thickness of the insert material due to swelling and shrinkage between the time of storing the carrier and the time of double-sided polishing of the wafer. There has been a need to develop a storage method for carriers for double-sided polishing machines that can improve the flatness of wafers.

The present inventors have focused on the fact that the osmotic pressure differs between the abrasive (alkaline aqueous solution) and water, and when storing the carrier, if the abrasive or alkaline solution used for double-sided polishing of the wafer is used, it is being stored. We have found that the carrier insert material can be in the same state during the actual double-sided polishing process and can suppress the change in the thickness of the insert material due to swelling and shrinkage, and completed the present invention.

That is, the present invention is used in a double-sided polishing apparatus having an upper and lower surface plates to which a polishing cloth is attached, and is arranged along an inner circumference of a carrier main body in which a holding hole for holding a wafer is formed and an inner circumference of the holding hole. A method for storing a carrier having a ring-shaped insert material having an inner peripheral surface in contact with the peripheral edge of the wafer, wherein the carrier is stored in a polishing agent or an alkaline solution used for double-sided polishing of the wafer. It is a storage method of a carrier for a double-sided polishing machine, which is characterized by the above.

Hereinafter, the present invention will be described in detail with reference to the drawings as an example of an embodiment, but the present invention is not limited thereto.

FIG. 5 shows an example of a carrier for a double-sided polishing machine that can be used in the present invention. As shown in FIG. 5, the carrier 1 stored in the present invention is arranged along the inner circumference of the carrier main body 3 and the holding hole 2 in which the holding hole 2 for holding the wafer is formed, and is arranged on the peripheral edge of the wafer. It has a ring-shaped insert material 4 having an inner peripheral surface in contact with the portion. The chamfered portion of the wafer can be protected by the insert material 4.

The carrier body 3 may be preferably made of a metal such as stainless steel or titanium. Further, the carrier body 3 may be surface-hardened. For example, the carrier body 3 may be surface-hardened with DLC (diamond-like carbon).

As the material of the insert material 4, a resin having a water absorption rate of 0.1% or more can be used. When a resin having a water absorption rate of 0.1% or more is used as the material of the insert material, in the conventional method, the change in the thickness of the insert material due to swelling and shrinkage becomes more remarkable during storage and double-sided polishing of the wafer. Will end up. Therefore, when such an insert material is used, it is possible to suppress a change in the thickness of the insert material due to swelling and shrinkage between the time of double-sided polishing of the wafer and the time of storage of the carrier, and the present invention is effective. Specifically, as the material of the insert material 4, a resin made of any one of vinyl resin, polystyrene resin, acrylic resin, polyamide resin, polyacetal, polycarbonate, polyethylene terephthalate, and fluorine resin can be used. can. These resins can be preferably used as the material of the insert material, but the material is not limited thereto. If necessary, a resin mixed with a filler may be used as the resin that is the material of the insert material.

Such a carrier 1 is used, for example, when the wafer W is double-sided polished in the 4-way type double-sided polishing apparatus 10 as shown in FIG. The double-sided polishing apparatus 10 includes an upper surface plate 11 and a lower surface plate 12 provided so as to face each other in the vertical direction. Abrasive cloth 13 is attached to the upper and lower surface plates 11 and 12, respectively. A sun gear 14 is provided in the central portion between the upper surface plate 11 and the lower surface plate 12, and an internal gear 15 is provided in the peripheral portion.

The outer peripheral teeth of the carrier 1 are meshed with each tooth portion of the sun gear 14 and the internal gear 15, and the carrier 1 rotates as the upper surface plate 11 and the lower surface plate 12 are rotated by a drive source (not shown). While revolving around the sun gear 14. At this time, both sides of the wafer W held by the holding holes 2 of the carrier 1 are simultaneously polished by the upper and lower polishing cloths 13. At the time of polishing the wafer W, the abrasive 17 is supplied from the abrasive supply device 16 to the polished surface of the wafer W.

The present invention is a method for storing the carrier 1 used in the double-sided polishing apparatus 10 as described above.

The storage method of the carrier for the double-sided polishing apparatus and the double-sided polishing method of the wafer of the present invention will be described with reference to the flow chart of FIG.

As shown in FIG. 1, the carrier storage method of the present invention can be applied, for example, when the wafer is first installed in a double-sided grinding machine for double-sided polishing. It is conceivable that a new carrier delivered by the manufacturer may be stored before use by replacing the carrier.
It is also possible to remove the carrier already used for double-sided polishing of the wafer from the double-sided grinding machine and apply it for temporary storage while re-installing the next wafer in the double-sided grinding machine for double-sided polishing. It can also be applied to the storage of the carrier once removed from the double-sided polishing machine during conditioning of the polishing cloth, replacement work due to the life end of the polishing cloth, and start-up work.

In the storage method of the present invention, the carrier is stored in an abrasive or an alkaline solution used for double-sided polishing of a wafer. The polishing agent and the alkaline solution are not particularly limited as long as they are used for double-sided polishing of the wafer, but it is preferably a polishing agent having a pH of 9-14, preferably 10-12, or an alkaline aqueous solution based on KOH or ammonia. Further, it is more preferable to store the wafer in the same abrasive or alkaline solution that is actually used for double-sided polishing of the wafer after storage because it can be stored under the same conditions as during the polishing process.

For example, as the abrasive, RDS-H11201 and RDS-H11202 (average particle size 75 nm and 90 nm) manufactured by Fujimi Incorporated, which are silica-based abrasive grains, are mixed at a mixing ratio of 1: 1 and the abrasive grain concentration is 2.4% by mass. A KOH-based alkaline aqueous solution having a pH of 10.5 can be exemplified.

The carrier stored in this way can be installed in the polishing apparatus 10 as shown in FIG. 6 to polish both sides of the wafer.

In this way, by always placing the carrier in the same state during and during the polishing process, it is possible to eliminate the influence of changes in the physical properties of the material itself.

As described above, in the present invention, since the carrier is not stored in water or in a dry state as in the conventional case, it is possible to suppress the change in the thickness of the insert material due to swelling and shrinkage during storage and polishing. .. Therefore, by polishing the wafer using the carrier stored by the storage method of the present invention, it is possible to improve the initial flatness of the edge portion of the wafer where the change in the thickness of the insert material is the largest.

_{Specifically, ESFQR max} can be used as an index of the flatness of the outer peripheral portion of the wafer. ESFQR (Edge Site Front last sQuares Range) is a flatness index indicating the flatness of the outer peripheral portion, and corresponds to SFQR (Site Front last sQuares Range) at the edge (outer peripheral portion). SFQR is defined as the range of positive and negative deviations from this reference plane when a cell of arbitrary dimensions is determined on the wafer surface and the plane calculated by the least squares method for this cell surface is used as the reference plane. Will be done.

Here, an example of how to take cells of ESFQR will be described with reference to FIGS. 7 and 8. FIG. 7 shows a top view of the wafer, and the outer peripheral portion thereof is shown to be divided by a rectangular region 20 (cell). For example, the wafer W can be divided into 72 wafers in the circumferential direction. FIG. 8 is an enlarged view of one of the rectangular regions 20 in FIG. 7, and as shown in FIG. 8, the rectangular region 20 has a straight line L ₂ (for example, 35 mm) extending in the radial direction from the outer peripheral end and a wafer. circumferential direction of the outer peripheral portion (e.g., 5 °) is surrounded by an arc _{L 1} corresponding to, _{L 3} from the outer peripheral edge in the diameter direction (e.g., 2 mm) outer peripheral excluded region of (edge exclusion:. e.E) is Not included. That is, the ESFQR is the SFQR value (range of positive and negative deviations from the least squares surface in the region) of the rectangular region 20 (cell). The value of ESFQR _max represents the maximum value of ESFQR in each site on a given wafer.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In the following Examples and Comparative Examples, the pH of the abrasive actually used for polishing the wafer is assumed to be 10.5, but the pH is not limited to this.

<Evaluation of pH of storage solution and thickness of insert resin>
The carrier as shown in FIG. 5 is contained in pure water (pH 7.5), an alkaline aqueous solution having a different pH, or an abrasive equivalent to the case where the pH of the abrasive actually used for processing and polishing is assumed to be 10.5. The swelling rate was measured and compared by immersing (storing) in the water for 24 hours. The results are shown in FIG.

As the insert material, a resin of 66 nylon-glass filler 43% manufactured by Shirasaki Seisakusho with a water absorption rate of 2.0-3.0% was used. As the carrier body, a carrier using pure titanium as a substrate and having a DLC coating treatment of about 2 μm on both sides was used. A carrier having a thickness of about 776 μm after coating was used.
As the alkaline aqueous solution, a KOH-based alkaline aqueous solution was used.
As an abrasive for carrier storage, RDS-H11201 and RDS-H11202 (average particle size 75 nm and 90 nm) manufactured by Fujimi Incorporated, which are silica-based abrasive grains, are mixed at a mixing ratio of 1: 1 and the abrasive grain concentration is 2.4. A KOH-based alkaline aqueous solution having a pH of 10.5 was used in an amount of% by mass.

The swelling rate indicates the rate at which the thickness increases due to swelling after immersion (after storage) in comparison with the thickness of the insert material in a dry state. The thickness of the insert material of each carrier was measured using a Mitutoyo micrometer.

As shown in FIG. 2, it was confirmed that the higher the pH, the thinner the thickness of the insert material, and the osmotic pressure was different due to the difference in the pH of the alkaline aqueous solution, and the resin swelled and shrunk. Further, it was confirmed that the thickness of the insert resin was changed due to slight swelling and shrinkage of the resin because the osmotic pressure of water was different even in the abrasive having the same pH 10.5 as the wafer polishing processing conditions. Here, at pH 9 of pure water (pH 7.5) and alkaline aqueous solution, the swelling rate was larger than that of the actual abrasive (pH 10.5 was assumed), and the thickness of the insert material became slightly thicker. On the other hand, at pH 13.5, the swelling rate is smaller than that of the abrasive (assuming pH 10.5), so that the thickness of the insert resin becomes thin. Therefore, it was found that storage in the range of pH 10 or more and pH 12 or less is more preferable because the change in the thickness of the insert resin is smaller than that of the actual abrasive (assuming pH 10.5).

<Evaluation of flatness of wafers that have been double-sided polished using carriers after storage>
(Example)
The carrier was stored by the storage method of the present invention, the carrier after storage was installed in the double-sided polishing apparatus 10 as shown in FIG. 6, and the wafer was actually polished to evaluate the flatness of the edge.

The carriers were stored for 24 hours in an abrasive having a pH of 10.5 used for polishing the wafers, and 25 silicon wafers having a diameter of 300 mm were polished on both sides using the stored carriers.

As the abrasive used for carrier storage and wafer polishing, RDS-H11201 and RDS-H11202 (average particle size 75 nm and 90 nm) manufactured by Fujimi Incorporated, which are silica-based abrasive grains, are ground at a mixing ratio of 1: 1. A KOH-based alkaline aqueous solution having a grain concentration of 2.4% by mass and a pH of 10.5 was used.
A double-sided polishing device DSP-20B manufactured by Fujikoshi Kikai Kogyo was used for wafer polishing, and SF4500 manufactured by Fujibo Ehime, which is a urethane foam pad having a shore A hardness of 90, was used as the polishing cloth.

WaferSigt2 manufactured by KLA Corporation was used for measuring the flatness of the wafer after the polishing process. The results of flatness measurement are shown in FIGS. 3 and 4. The index of the flatness of the edge portion (outer peripheral portion) of the wafer is ESFQR _max .

(Comparative example)
The carriers were stored in the same manner as in Examples except that the carriers were stored in pure water having a pH of 7.5, and the wafer was polished on both sides using the stored carriers to evaluate the flatness of the polished wafer. did.

As shown in FIG. 3, as compared with the case where the carrier, which is a comparative example, was stored in a state of being immersed in pure water, in the example, the insert material was stored under the same conditions as during the polishing process, so that the thickness of the insert material did not fluctuate. , It was confirmed that the edge flatness at the beginning of the batch was improved. From the histogram as shown in FIG. 4, it was confirmed that the edge flatness of the example was improved.

The present invention is not limited to the above embodiment. The above-described embodiment is an example, and any of the above-described embodiments having substantially the same configuration as the technical idea described in the claims of the present invention and having the same effect and effect is the present invention. Is included in the technical scope of.

1 ... carrier, 2 ... holding hole, 3 ... carrier body, 4 ... insert material,
10 ... Double-sided polishing device, 11 ... Upper surface plate, 12 ... Lower surface plate, 13 ... Polishing cloth,
14 ... Sun gear, 15 ... Internal gear, 16 ... Abrasive supply device 17 ... Abrasive,
20 ... rectangular area, W ... wafer.

Claims (5)

Used in a double-sided polishing device having an upper and lower surface plate to which a polishing cloth is attached, a carrier main body having a holding hole for holding a wafer and a carrier body arranged along the inner circumference of the holding hole are arranged on the peripheral edge of the wafer. A method of storing a carrier having a ring-shaped insert material having an inner peripheral surface in contact with the portion.
Method for storing a carrier for a double-side polishing apparatus, characterized by storing the carrier, in the polishing agent used in double-sided polishing of the wafer. And with the abrasive storage method of a carrier for double-side polishing apparatus according to claim 1, characterized in that used as pH it is 10 to 12. The method for storing a carrier for a double-sided polishing machine according to claim 1 or 2, wherein a resin having a water absorption rate of 0.1% or more is used as the material of the insert material. The claim is characterized in that, as the material of the insert material, a resin made of any one of vinyl-based resin, polystyrene-based resin, acrylic-based resin, polyamide-based resin, polyacetal, polycarbonate, polyethylene terephthalate, and fluorine-based resin is used. The method for storing a carrier for a double-sided polishing apparatus according to any one of claims 1 to 3. The carrier is stored by the storage method according to any one of claims 1 to 4.
A double-sided polishing method for a wafer, which comprises polishing the wafer using the stored carrier.

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