JP2011143520A - Insert material, double-sided polishing device using the same, and double-sided polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insert material for a double-sided polishing device in which the development ratio of scratches generated on a surface of a semiconductor wafer after double-sided polishing can be smaller than that of the conventional method, the double-sided polishing device using the insert material, and a double-sided polishing method. <P>SOLUTION: The insert material is a ring-shaped resin insert material which is disposed at least between an upper and lower surface plates pasted with abrasive clothes, disposed along an inner peripheral part of a holding hole of a carrier base material which has the holding hole formed for holding the wafer sandwiched between the upper and lower surface plates during polishing, and contacted with a circumferential edge part of the wafer to be held. The insert material is composed of a resin having ash content of not more than 0.05 wt.%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an insert material provided in a carrier used for double-side polishing of a semiconductor wafer.

When both surfaces of a semiconductor wafer are simultaneously polished by polishing or the like, the semiconductor wafer is held by a carrier.
The carrier is generally formed to be thinner than the semiconductor wafer, and has a holding hole for holding the wafer at a predetermined position between the upper surface plate and the lower surface plate of the double-side polishing apparatus. The semiconductor wafer is inserted and held in this holding hole, and the upper and lower surfaces of the semiconductor wafer are sandwiched by polishing tools such as polishing cloths provided on the opposing surfaces of the upper surface plate and the lower surface plate, and the polishing slurry is supplied to the polishing surface. Polishing is performed.

  Here, the carrier used for double-side polishing in such a semiconductor wafer polishing step is mainly a metal carrier. For this reason, in order to protect a wafer peripheral part from the damage by a metal carrier, the resin-made insert materials are attached along the inner peripheral part of this holding hole.

  The resin-made insert material fitted in the inner periphery of the wafer holding hole used in the past is made by laminating a fiber reinforced resin impregnated with epoxy resin into inorganic fibers such as carbon fiber or aramid nonwoven fabric. (See, for example, Patent Document 1).

JP 2009-202259 A

However, when double-side polishing of a semiconductor wafer is performed using a carrier to which such an insert material is attached, scratches may occur on the surface of the polished wafer.
A semiconductor wafer in which such a scratch has occurred is naturally defective, and therefore, it is necessary to re-polish, which affects the production yield of the semiconductor wafer and thus rebounds to the production cost.

  The present invention has been made in view of the above problems, and an insert material for a double-side polishing apparatus capable of reducing the occurrence rate of scratches generated on the surface of a semiconductor wafer after double-side polishing, and the use thereof. An object of the present invention is to provide a double-side polishing apparatus and a double-side polishing method.

  In order to solve the above-described problems, in the present invention, at least a holding unit that is disposed between upper and lower surface plates to which a polishing cloth is attached and holds a wafer sandwiched between the upper and lower surface plates during polishing. A ring-shaped resin insert material that is disposed along the inner peripheral portion of the holding hole of the carrier base material in which holes are formed, and is in contact with the peripheral edge portion of the held wafer. Provided is an insert material comprising a resin of 0.05 wt% or less.

As will be described in detail later, the present inventors have clarified that scratches are generated by the inorganic impurities contained in the insert material dropping from the insert material during double-side polishing due to wear or the like.
Therefore, if the insert material disposed in the inner peripheral portion of the wafer holding hole of the double-side polishing carrier is made to have an ash content of 0.05 wt% or less, the inorganic material contained in the insert material during double-side polishing of a semiconductor wafer Since the amount of the compound is sufficiently small, the occurrence rate of scratches generated on the surface of the semiconductor wafer after polishing can be significantly reduced as compared with the conventional case. That is, the production efficiency of the semiconductor wafer can be improved, and the manufacturing yield can be improved.
In addition, the ash content in this invention shows the residue (inorganic impurity and its oxide) which remain | survives when the resin which comprises insert material is heated at high temperature. For example, this indicates a residue remaining in a platinum crucible when the resin is put in a platinum crucible and continuously heated at 800 ° C. in an electric furnace to completely burn the resin.

Here, in the insert material, the thickness Hi [μm] of the insert material satisfies the relationship of Hc ≧ Hi ≧ Hc−10 μm with respect to the thickness Hc [μm] of the carrier base material. It is preferable.
As described above, when the thickness Hi of the insert material is Hc and the carrier base material thickness is Hc, the wear of the insert material due to the polishing of the semiconductor wafer is satisfied by satisfying the relationship of Hc ≧ Hi ≧ Hc−10 μm. Can be suppressed, the life of the insert material becomes long, and the running cost can be reduced.

Moreover, it is preferable that the said insert material consists of a polycarbonate or a polyacetal.
Insert materials made of polycarbonate or polyacetal with a low content of inorganic impurities can reliably reduce the scratch rate on the surface of semiconductor wafers, and high-purity products with a low content of inorganic impurities are relatively easy. Moreover, since it can be obtained at a low cost, it can be made an inexpensive insert material.

And it is preferable that the said insert material is produced by extrusion molding or injection molding.
Thus, extrusion molding or injection molding is suitable for producing polycarbonate and polyacetal with a low content of inorganic impurities, and is suitable for making an insert material having a low scratch generation rate.

  The present invention also provides a double-side polishing apparatus characterized by comprising at least a carrier for a double-side polishing apparatus comprising the insert material according to the present invention and the carrier base material.

  As described above, if the double-side polishing apparatus includes at least the carrier for the double-side polishing apparatus composed of the insert material and the carrier base material of the present invention, the generation of scratches can be reduced, the semiconductor wafer can be polished on both sides with high productivity, and the flatness It is possible to make a great contribution to the manufacture of a semiconductor wafer having a high height.

  Furthermore, in the present invention, a method for double-side polishing a semiconductor wafer, wherein a carrier for a double-side polishing apparatus comprising the insert material according to the present invention and the carrier base material is disposed between upper and lower surface plates to which a polishing cloth is attached. There is provided a method for double-side polishing a semiconductor wafer, comprising holding a semiconductor wafer in a holding hole formed in the carrier and sandwiching the semiconductor wafer between the upper and lower surface plates to perform double-side polishing.

  If the semiconductor wafer is held in the holding hole of the carrier for a double-side polishing apparatus consisting of the insert material and carrier base material of the present invention as described above, the occurrence of scratches can be reduced, polishing with good productivity, and flatness can be achieved. It is possible to make a semiconductor wafer having a high level.

  As described above, according to the present invention, the resin insert material has a low inorganic impurity concentration causing scratches, and the scratch occurrence rate of a semiconductor wafer in double-side polishing can be greatly improved as compared with the conventional case.

It is the figure which showed the relationship between the ash content in an insert material, and the scratch generation rate on the surface of a semiconductor wafer. It is the figure which showed an example of the external appearance of the ash content contained in the conventional insert material, and the analysis result of the composition. It is the figure which showed the result of the experiment which confirmed whether a semiconductor wafer surface generate | occur | produces a scratch by the ash content contained in insert material. It is the figure which showed typically the cause which a scratch generate | occur | produces when using the conventional insert material. It is the figure which showed an example of the manufacturing method of the insert material of this invention. It is the figure which showed an example of the manufacturing method of the conventional insert material. It is the schematic which showed an example of the cross section of the double-side polish apparatus provided with the carrier for double-side polish apparatuses which consists of an insert material and carrier base material of this invention. It is the figure which showed an example of the internal structure of the double-side polish apparatus by planar view.

Hereinafter, the present invention will be described more specifically.
As described above, development of an insert material for a double-side polishing apparatus capable of reducing the occurrence rate of scratches on the surface of a semiconductor wafer after double-side polishing, a double-side polishing apparatus and a double-side polishing method using the same. Was waiting.

Accordingly, the present inventors have intensively studied to find out the cause of occurrence of scratches.
First, as shown in, for example, Japanese Patent Application Laid-Open Nos. 11-11986 and 2008-44083, it is known that the cause of the scratch is a broken piece from a carrier or a broken piece of a fiber dropped from an insert material. .
Therefore, an insert material to which an aramid nonwoven fabric was not added was prepared and both surfaces of the wafer were polished. However, even when such an insert material was used, the occurrence rate of scratches could hardly be reduced.

Therefore, the resin constituting the insert material is considered to contain substances that cause scratches, and the resin constituting the insert material is analyzed, and the composition of inorganic impurities that remain without being sublimated by heating. Analysis was performed by EDX.
As a result, when 15.5 g of an aramid-epoxy laminate, which is a conventional insert material, was heated and burned, the residue (ash content / inorganic impurities) was 2.98 × 10 ⁻² g, and the weight concentration It was found to be 0.20 wt%. Further, as shown in FIG. 2, the composition was found to be Ca, Fe, Na, Mg, Al, Si and oxides thereof.

Then, 1 mg of such ash content was mixed in the polishing slurry, and a semiconductor wafer prepared in advance without scratches was polished on both sides by about 2 μm.
As a result, as shown in FIG. 3, the scratches were not generated in the wafer (batch No. 1) polished with the slurry containing no ash, despite the same conditions except for the presence or absence of ash addition. On the other hand, in the wafers (batch Nos. 2 and 3) polished with the slurry mixed with ash, it was found that scratches were generated on the surface with high probability.

That is, in the conventional insert material made of fiber reinforced resin, for example, as shown in FIG. 6, a resin plate for hollowing out the insert material 23 is laminated.
In the lamination molding process, there are many opportunities to touch metal parts such as a roll and a squeeze roll for applying tension to the fiber base material. For this reason, a lot of metal impurities are taken into the resin sheet, and since these are stacked, the impurities are integrated by the number of layers. Therefore, the resulting laminated resin plate 22 contains a total of 0.1 to 0.3 wt% of inorganic impurities such as Si, Ca, Fe, Na, Mg, and Al.

And as shown in FIG. 4, since this inorganic impurity is a trace amount and generally harder than a semiconductor wafer, when it is removed from the insert material 13 during double-side polishing, the wafer surface is damaged and scratches are generated. I found out.
That is, it has been found that the cause of scratches generated on the surface of the semiconductor wafer after double-side polishing is an inorganic impurity contained in the insert material.

  As a result of further intensive studies, the inventors of the present invention generated a ring-shaped resin insert material on the surface of a semiconductor wafer after double-side polishing by making the ash content of a resin having a weight of 0.05 wt% or less. The present invention has been completed by discovering that the occurrence rate of scratches can be reduced as compared with the prior art.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.
7 is a schematic view showing an example of a cross section of a double-side polishing apparatus provided with a carrier for a double-side polishing apparatus comprising the insert material and carrier base material of the present invention, and FIG. 8 is an internal structure of the double-side polishing apparatus in a plan view. It is the figure which showed an example.

  First, in FIGS. 7 and 8, a double-side polishing apparatus 10 having at least a carrier 11 for a double-side polishing apparatus comprising an insert material 13 and a carrier base material 12 according to the present invention has a lower surface plate 15b provided vertically opposite to each other. And an upper surface plate 15a, and polishing cloths 16a and 16b are affixed to opposite surfaces of the surface plates 15a and 15b, respectively. A sun gear 19 is provided at the center between the upper surface plate 15a and the lower surface plate 15b, and an internal gear 20 is provided at the periphery. The semiconductor wafer W is held in the holding hole 14 of the carrier base material 12 and is sandwiched between the upper surface plate 15a and the lower surface plate 15b.

  The teeth of the sun gear 19 and the internal gear 20 are meshed with the outer peripheral teeth of the carrier. As the upper surface plate 15a and the lower surface plate 15b are rotated by a drive source (not shown), the carrier 11 Revolving around the sun gear 19 while rotating. At this time, the semiconductor wafer W is held in the holding holes 14 of the carrier base material 12 and both surfaces are simultaneously polished by the upper and lower polishing cloths 16a and 16b. At the time of polishing, polishing slurry is supplied from the nozzle 17 through the through hole 18.

In FIG. 8, each carrier holds and polishes one wafer. However, a carrier having a plurality of holding holes is used to hold and polish a plurality of wafers in each carrier. Also good.
In the above description, the carrier of the planetary double-side polishing apparatus has been described as an example. However, the carrier for the double-side polishing apparatus of the present invention is not limited to the planetary type, and may be adopted as the carrier of the swing type double-side polishing apparatus. It is valid.

  Here, the ring-shaped contact is arranged along the inner peripheral portion of the holding hole 14 of the carrier base material 12 in which the holding hole 14 for holding the semiconductor wafer W is formed and is in contact with the peripheral portion of the held wafer W. The resin insert material 13 is made of a resin having an ash content of 0.05 wt% or less.

As described above, there are many inorganic impurities contained in the insert material during double-side polishing, and if the ash content is more than 0.05 wt%, the ash content that drops from the insert material due to wear of the insert material increases. Scratches frequently occur on the wafer surface due to ash.
However, as in the present invention, if it is a resin-made insert material having an ash content of 0.05 wt% or less, the content of the substance that causes scratches on the wafer surface is sufficiently small, so double-side polishing In this case, polishing can be performed in a state where the probability of occurrence of scratches is reduced compared to the conventional case. Therefore, a flat semiconductor wafer with few scratches can be obtained efficiently.

If an insert material made of a resin having an ash content of more than 0.05 wt% is used, the scratch generation rate on the wafer surface increases, so the ash content is set to 0.05 wt% or less.
Moreover, when using fiber reinforced resin, it is desirable not to use inorganic substances, such as glass fiber and carbon fiber, for fiber. Furthermore, it is more desirable not to mix inorganic fillers, additives and the like in the resin and fiber.

  Therefore, if it is a double-side polishing apparatus equipped with a carrier for double-side polishing apparatus consisting of such an insert material and a carrier base material, it is possible to perform double-side polishing of a semiconductor wafer with high productivity without generating almost any scratch, This greatly contributes to the manufacture of semiconductor wafers with high flatness.

Here, the insert material 13 can be made of polycarbonate or polyacetal.
When the ash content of the high-purity polycarbonate resin was measured, the residue (ash content) was 0.012 wt% in terms of weight concentration. Since this ash content was extremely small, a sample could not be collected and EDX measurement could not be performed. Similarly, as a result of measuring the ash content of high-purity polyacetal in the same manner, the ash content was very small, and EDX measurement could not be performed as in the case of polycarbonate.
By using an insert material made of polycarbonate or polyacetal having a low content of inorganic impurities, the scratch occurrence rate on the wafer surface can be reliably reduced. Moreover, since these materials can prepare a high purity product with a low content of inorganic impurities relatively easily, the cost required for the insert material can be reduced.

And this insert material shall consist of a polycarbonate or polyacetal produced by extrusion molding or injection molding.
Thus, if the ring-shaped resin insert material obtained by processing a resin made from the single-layer resin plate 21 formed by extrusion molding as shown in FIG. 5, the base resin sheet is a single layer and is laminated. Incorporation of inorganic impurities at the time of sheet molding can be reduced by this amount, which is advantageous for obtaining an insert material having a lower scratch generation rate than conventional ones. Similarly, by injection molding, it is also suitable for making a resin sheet as a base material into a single layer.
However, in order to obtain an insert material having an ash content of 0.05 wt% or less more reliably, it is desirable to take measures to prevent inorganic impurities from being mixed in extrusion molding or injection molding.

In addition, the thickness Hi [μm] of the insert material 13 can satisfy the relationship of Hc ≧ Hi ≧ Hc−10 μm with respect to the thickness Hc [μm] of the carrier base material 12.
Thus, if the thickness of the insert material is substantially the same as the thickness of the carrier base material or thin in the range of 10 μm or less, the ratio of the insert material contacting the polishing cloth can be reduced when polishing the semiconductor wafer. Therefore, it can suppress that it wears. As a result, the life of the insert material can be extended, and the running cost can be reduced. Moreover, since the wear of the insert material is suppressed, scratches are less likely to occur.

Further, it is desirable that the inner diameter R [mm] of the insert material 13 satisfies the relationship r ≦ R ≦ r + 2 mm with respect to the diameter r [mm] of the semiconductor wafer W.
If the inner diameter of the insert material satisfies such a relationship, the semiconductor wafer can be appropriately held by the insert material during double-side polishing of the wafer, so that it is possible to prevent the wafer from rampaging in the holding hole during double-side polishing. Can be finished into a flatter wafer.

  A carrier 11 for a double-side polishing apparatus comprising the insert material 13 and the carrier base material 12 of the present invention is disposed between the upper and lower surface plates 15a and 15b to which the polishing cloths 16a and 16b are attached. By holding the semiconductor wafer W in the holding hole 14 and sandwiching the semiconductor wafer W between the upper and lower surface plates 15a and 15b, the semiconductor wafer W is polished on both sides, thereby suppressing the generation of scratches and polishing the semiconductor wafer on both sides with high productivity. This makes it possible to manufacture a semiconductor wafer with high flatness.

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.
First, as a resin plate for producing an insert material, a polycarbonate resin plate (Example 1) produced by extrusion forming a high-purity single layer resin plate, and by extrusion forming a high-purity single layer resin plate A produced polyacetal resin plate (Example 2), a polypropylene (PP) single layer plate (Comparative Example 1), and a laminated resin plate produced by lamination molding of a fiber reinforced resin plate impregnated with an epoxy resin in an aramid nonwoven fabric substrate ( Comparative Example 2), a total of five laminated resin plates (Comparative Example 3) prepared by laminating a fiber reinforced resin plate impregnated with a phenolic resin in an aramid nonwoven fabric, and an insert material was prepared from this resin plate.

  And the ash content contained in the excessive resin part at the time of producing these insert materials was measured. Specifically, the remainder of the resin whose weight was measured in advance was put in a platinum crucible, and the resin was completely burned by continuing to heat at 800 ° C. in an electric furnace, and the weight of the residue remaining in the platinum crucible was measured. Calculated as (weight of residue) / (weight of excess resin).

Then, these carrier insert materials are arranged on the inner peripheral portion of the wafer holding hole formed in the carrier base material obtained by applying DLC coating on titanium, and double-side polishing of 100 silicon wafers is performed at different times. I went twice.
Then, whether or not scratches were generated on the surface of the double-side polished silicon wafer was evaluated by measuring the surface shape with a SUNCSCAN SP-1 device manufactured by TENCOR.

  As a result, the ash content of the insert material produced from the polycarbonate high-purity single layer resin plate of Example 1 was 0.02 wt%. Moreover, the ash content of the insert material produced from the polyacetal high-purity single-layer resin plate of Example 2 was 0.048 wt%. The ash content of the insert material of Comparative Example 1 was 0.11 wt%, the ash content of the insert material of Comparative Example 2 was 0.20 wt%, and the ash content of the insert material of Comparative Example 3 was 0.23 wt%.

  And when the insert material of Example 1 was used, the scratch generation rate was 2 to 5%. Moreover, in the insert material of Example 2, the scratch occurrence rate was 3 to 6%. On the other hand, the scratch occurrence rate when the insert material of Comparative Example 1 was used was 8 to 11%, the insert material of Comparative Example 2 was 10 to 15%, and the insert material of Comparative Example 3 was 12 to 16%. .

Then, when the relationship between the ash contained in the resin and the occurrence rate of scratches on the wafer surface was examined, as shown in FIG. 1, there is a proportional relationship between the ash content contained in the resin and the occurrence rate of scratches on the wafer surface. It was found that if the ash content in the insert material is small, the scratch generation rate can be lowered, but as the ash content increases, the scratch generation rate also increases.
That is, it was found that the rate of occurrence of scratches on the wafer surface can be reduced by using an insert material made of a resin having an ash content of 0.05 wt% or less.

  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.

10: Double-side polishing device,
DESCRIPTION OF SYMBOLS 11 ... Carrier, 12 ... Carrier base material, 13 ... Insert material, 14 ... Holding hole, 15a ... Upper surface plate, 15b ... Lower surface plate, 16a, 16b ... Polishing cloth, 17 ... Nozzle, 18 ... Through-hole, 19 ... Sun gear 20 ... Internal gear,
21 ... Single layer resin plate, 22 ... Laminated resin plate, 23 ... Insert material,
W: Semiconductor wafer.

Claims (6)

At least the holding of the carrier base material, which is disposed between the upper and lower surface plates to which the polishing cloth is attached, and in which a holding hole is formed for holding the wafer sandwiched between the upper and lower surface plates during polishing. A ring-shaped resin insert material disposed along the inner periphery of the hole and in contact with the peripheral edge of the held wafer,
The insert material is made of a resin having an ash content of 0.05 wt% or less.   In the insert material, the thickness Hi [μm] of the insert material satisfies the relationship of Hc ≧ Hi ≧ Hc−10 μm with respect to the thickness Hc [μm] of the carrier base material. The insert material according to claim 1.   The insert material according to claim 1, wherein the insert material is made of polycarbonate or polyacetal.   The insert material according to claim 3, wherein the insert material is produced by extrusion molding or injection molding.   5. A double-side polishing apparatus comprising at least a carrier for a double-side polishing apparatus comprising the insert material according to claim 1 and the carrier base material. A method for polishing a semiconductor wafer on both sides,
A carrier for a double-side polishing apparatus comprising the insert material according to any one of claims 1 to 4 and the carrier base material is disposed between upper and lower surface plates to which an abrasive cloth is attached, and formed on the carrier. A semiconductor wafer double-side polishing method, wherein a semiconductor wafer is held in the holding holes and sandwiched between the upper and lower surface plates to perform double-side polishing.

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