JP5575363B2 - Polishing pad - Google Patents

Description

  The present invention relates to a polishing pad used when performing planarization processing of an object to be polished such as a wafer by a chemical mechanical polishing (hereinafter referred to as “CMP”) method in a manufacturing process of a semiconductor device or the like.

In general, in the CMP method, a polishing pad is held on a surface plate, an object to be polished such as a silicon wafer is held on a polishing head, and the polishing pad and the object to be polished are pressurized while supplying a polishing slurry. Polishing is performed by sliding relatively (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2003-224093

  The polishing pad is held on the surface plate by using, for example, a double-sided tape 3 shown in FIG. The polishing pad shown in FIG. 5 is composed of a single polishing layer 2, and on the back surface of the polishing layer 2, a double-sided tape 3 having an adhesive layer 6 on both surfaces of a substrate 5 such as a PET film is provided. The release paper 7 of the double-sided tape 3 is peeled off, and a polishing pad is bonded and fixed to a surface plate (not shown).

  The polishing layer 2 is made of, for example, foamed polyurethane, and has a large number of pores due to foaming. When polishing, the holes open on the surface 2a of the polishing layer 2, and hold the abrasive grains contained in the polishing slurry supplied to the surface 2a to enable efficient polishing. Many holes have large diameters that pass through the polishing layer 2 beyond the thickness of the polishing layer 2.

  The polishing slurry supplied to the surface 2a side of the polishing layer 2 reaches the adhesive layer 6 of the double-sided tape 3 on the back side of the polishing layer 2 through such a large-diameter hole that penetrates the polishing layer 2. For example, due to the strongly alkaline polishing slurry, the components of the adhesive layer 6 are eluted and reach and adhere to the surface 2a of the polishing layer 2 pressed against the object to be polished such as a silicon wafer, thereby reducing the polishing rate. There is a problem.

  Further, not only the polishing rate is lowered, but also the adhesive material layer 6 of the double-sided tape 3 is eluted, whereby the adhesive strength between the polishing pad and the double-sided tape 3 is weakened and the polishing pad may be peeled off from the double-sided tape 3. There is also a problem that there is.

  In particular, in double-side polishing, since the polishing slurry is supplied under pressure, the elution of the components of the adhesive material layer of the double-sided tape is also promoted, and the above problem becomes significant.

  The same applies not only to the above-mentioned holes due to foaming, but also to the case where the processing hole provided in the polishing pad reaches the double-sided tape on the back surface of the polishing pad for the purpose of improving the retention of the polishing slurry. Challenges arise.

  The present invention has been made in view of the above points, and has as its main purpose to suppress a decrease in the polishing rate of a polishing pad fixed to a surface plate by a double-sided tape. Further, the polishing pad is a double-sided tape. The purpose is to prevent peeling.

The polishing pad of the present invention is a polishing pad having a polishing layer whose surface is pressed against an object to be polished, and fixed to a surface plate by a double-sided tape provided on the back side of the polishing layer. Between the back surface and the double-sided tape, there is provided a water-stopping layer that blocks the polishing slurry, and the water- stopping layer is made of a thermal adhesive film that is a hot melt adhesive.

  The water-stopping layer is preferably capable of completely blocking the polishing slurry, but it is sufficient that the penetration of the polishing slurry can be suppressed even if it cannot be completely blocked.

  According to the present invention, since the water-stopping layer that blocks the polishing slurry is provided between the polishing layer and the double-sided tape, the polishing slurry supplied to the surface of the polishing layer is removed from the surface of the polishing layer to the back side. It is possible to prevent the adhesive material component of the double-sided tape from dissolving by penetrating into the tape, thereby preventing the adhesive component from adhering to the surface of the polishing layer and reducing the polishing rate, and The polishing layer can be prevented from peeling off from the double-sided tape.

  In one embodiment of the present invention, the double-sided tape has an adhesive layer formed on both sides of a base material.

  According to this embodiment, since the penetration of the polishing slurry into the double-sided tape is blocked by the water-stopping layer, it is possible to prevent the components of the adhesive material layer of the double-sided tape from eluting. In addition, the water-stopping layer and the double-sided tape can be reliably and easily bonded by the adhesive material layer of the double-sided tape.

  In another embodiment of the present invention, the polishing layer is a polyurethane foam.

  According to this embodiment, when the diameter of the hole due to foaming of the polishing layer made of polyurethane foam is large and penetrates the polishing layer, even if the polishing slurry penetrates from the penetrating hole, both sides are stopped by the water-stopping layer. Reaching the tape can be prevented.

  In still another embodiment of the present invention, the polishing layer is a nonwoven fabric impregnated with polyurethane and cured.

  According to this embodiment, even if the polishing slurry permeates the polishing layer made of a nonwoven fabric impregnated and cured with polyurethane, it can be prevented from reaching the double-sided tape by the water stop layer.

In this onset bright, the waterproofing layer is a thermal adhesive film is a hot melt adhesive.

According to the present invention , the thermal adhesive film can be heated and melted and adhered to the back surface of the polishing layer to provide a water stop layer. Moreover, since it is a film form, it can be set as the water stop layer of uniform thickness.

  The melting temperature of the thermal adhesive film is preferably 70 ° C. or higher and 120 ° C. or lower, and more preferably 90 ° C. or higher and 100 ° C. or lower. The higher the melting temperature, the higher the density after bonding and the cross-linking density of the thermal adhesive film constituting the water-stopping layer, and the components will not be eluted even when exposed to the polishing slurry.

  As the thermal adhesive film, polyamide, polyurethane, polyester, or EVA olefin can be used.

  When the polishing layer is polyurethane, the thermal adhesive film is preferably polyurethane, and the component ratio of the polyol component to the isocyanate component is 90 to 70%: 10 to 30% in mol%. preferable.

The molecular weight of the polymer of the heat-adhesive film is preferably a weight average molecular weight to ^{2 × 10 4 ~4 × 10 4} .

  According to the present invention, since the water-stopping layer that blocks the polishing slurry is provided between the polishing layer and the double-sided tape, the polishing slurry supplied to the surface of the polishing layer is moved from the surface of the polishing layer to the back side. It is prevented from penetrating into the double-sided tape, the adhesive layer component of the double-sided tape is prevented from melting and adhering to the surface of the polishing layer, thereby preventing a reduction in the polishing rate and polishing. The layer can be prevented from peeling from the double-sided tape.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of a polishing pad according to an embodiment of the present invention, and portions corresponding to the above-described conventional example are denoted by the same reference numerals.

  The polishing pad of this embodiment is a single layer pad having a polishing layer 2 whose surface 2a is pressed against an object to be polished such as a silicon wafer, and the back side of the polishing layer 2 is for fixing to a surface plate. A double-sided tape 3 is provided.

  The polishing layer 2 of this embodiment is made of foamed polyurethane obtained by foaming a urethane resin.

  As this urethane resin, any of polyether-based, polyester-based, polyester-ether-based, and polycarbonate-based urethane resins can be used. Examples of the polyol component used in the production of each urethane resin include polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, polyethylene adipate, polypropylene adipate, polyoxytetramethylene adipate, and the like. Examples of the isocyanate component include 4-4'-diphenylmethane diisocyanate and 2,4-tolylene diisocyanate.

  The thickness of the polishing layer 2 is, for example, 0.8 mm to 3.0 mm, and there are many pores due to foaming. Some of these holes have a maximum diameter equal to or greater than the thickness of the polishing layer 2. That is, the polishing layer 2 has a hole penetrating from the polishing surface to the back surface of the front surface 2a.

The density of the polishing layer 2 ^is preferably in the range of ^{0.4g / cm 3 ~0.9g / cm 3} , more preferably about 0.5 g / cm ^3.

  The double-sided tape 3 includes a resin film as a base material, for example, a PET (polyethylene terephthalate) film 5, for example, an acrylic adhesive material layer 6 on both sides, and a release paper 7.

  The pressure-sensitive adhesive material of the pressure-sensitive adhesive layer 6 is fluidized by applying pressure at normal temperature and develops a pressure-sensitive adhesive function. The density and the cross-linking density of the pressure-sensitive adhesive material are the same as those of the thermal adhesive film constituting the waterstop layer 8 described later. In comparison, when exposed to a polishing slurry, hydrolysis and the like occur much more easily than the thermal adhesive film, and the components are eluted.

  In this embodiment, the polishing slurry supplied to the polishing surface of the surface 2a of the polishing layer 2 reaches the adhesive material layer 6 of the double-sided tape 3 through the hole penetrating the polishing layer 2, and the components of the adhesive material layer 6 are In order to prevent elution, a water blocking layer 8 is provided between the back surface of the polishing layer 2 and the double-sided tape 3.

  In this embodiment, the water blocking layer 8 is made of a thermal adhesive film that is a hot melt adhesive. Examples of the thermal adhesive film include polyamide-based, polyurethane-based, polyester-based, or EVA (Ethylene vinyl acetate) olefins. Any material of the system can be used.

  In this embodiment, since the polishing layer 2 is a foamed polyurethane, the same polyurethane-based thermal adhesive film is used as the water blocking layer 8, and this polyurethane-based thermal adhesive film is composed of a polyol component and an isocyanate component. The component ratio is preferably 90-70%: 10-30% in mol%.

The molecular weight of the polymer of the heat adhesive film is preferably from 2 × ^{10 4} ~4 × ¹⁰ 4 and a weight average molecular weight, in particular, in the range of 2.5 × ^{10 4} ~3.5 × ¹⁰ 4 preferable.

  The thermal adhesive film is basically an adhesive and does not have stickiness, and it is necessary to change its form in order to develop adhesive force. Usually, a temperature of about 100 ° C. or higher is required. It is necessary to spend a certain amount of time. Since the temperature at the time of general polishing is about 30 ° C. to 40 ° C., the thermal adhesive film does not melt into the polishing slurry like the adhesive layer 6 of the double-sided tape 3.

  The higher the melting temperature of the thermal bonding film, the higher the density after bonding and the cross-linking density, and the components do not elute even when exposed to the polishing slurry. Therefore, the melting temperature of the thermal bonding film is the lowest. 100 ° C. or higher, preferably about 120 ° C.

  The thickness of the water blocking layer 8 is preferably 0.03 mm to 0.2 mm. In particular, if it is about 0.07 mm, sufficient water-stopping effect and adhesive force can be obtained.

  The water blocking layer 8 can be provided by hot pressing on the back surface side of the polishing layer 2 by, for example, flat pressing or roll pressing.

  From the viewpoint of mass productivity, the fluidization temperature of the thermal adhesive film is preferably 80 ° C. to 100 ° C., and the melt viscosity is preferably 300 ps or less for processing.

  The above-mentioned polishing pad of FIG. 1 can be obtained by thermocompression bonding the double-sided tape 3 to the polishing layer 2 to which the water blocking layer 8 is bonded.

  Since the double-sided tape 3 has the adhesive material layer 6 as described above, the adhesive material layer 6 adheres to the water stop layer 8 on the back surface of the polishing layer 2 with sufficient strength.

  Hereinafter, the present invention will be described in detail with reference to examples.

On the back surface of a polishing layer made of polyurethane that has been chemically foamed, a urethane-based thermal adhesive film (polyol component: approximately 85% in the isocyanate component (mol%): 15%, weight average molecular weight 2.8 × 10 ⁴ ) Was thermally bonded as a water-stopping layer, and then a double-sided tape was thermocompression bonded to the water-stopping layer to produce a polishing pad sample of the example. Also, a double-sided tape was thermocompression bonded to the back surface of a chemically-fired polyurethane polishing layer to produce a polishing pad sample of a comparative example similar to the conventional one.

  Next, double-side polishing was performed using the polishing pads of Examples and Comparative Examples under the following polishing conditions, and the polishing rate was measured using Ultra Gage 9500A manufactured by ADE.

Polishing conditions and polishing slurry: colloidal silica slurry, pH 11
・ Polisher: 1440mm surface plate, double-sided polisher ・ Platen rotation speed: Up; 20rpm / Down; 15rpm / Carrier; 24rpm
・ Slurry flow rate: 10L / min
・ Polishing pad Example (with water blocking layer), comparative example (without water blocking layer)
・ Pressure: 180 gf / cm ²
・ Polishing time: 40 min
・ Slurry dilution ratio: 1:20 (2.5% Solid @ POU)
Dress condition 1
Platen rotation speed: Up; 20 rpm / down; 20 rpm / carrier; 24 rpm
・ Rinse flow rate: 5L / min
・ Pressure: 100 gf / cm ²
・ Polishing time: 2 min
・ Dress: # 100,10min
Dress condition 2
Platen rotation speed: Up; 30 rpm / down; 30 rpm / dress; 60 rpm
・ Rinse flow rate: 5L / min
・ Pressure: 100 gf / cm ²
・ Polishing time: 2 min
・ Dress: # 100 or # 80 10min
FIG. 2 is a diagram showing the polishing results, in which the horizontal axis indicates the polishing time (min) and the vertical axis indicates the polishing rate (μm).

  As shown in FIG. 2, in the polishing pad of the comparative example having no water stop layer, the polishing rate decreases with the lapse of the polishing time, and after polishing for 2,000 minutes, the polishing rate becomes 0.4 μm / min. It is below.

  On the other hand, in the polishing pad of the example provided with the water stop layer, the polishing rate is hardly decreased, and the polishing rate is maintained at 0.4 μm / min or more over the polishing time of 14,000 minutes or more. I understand that.

  Thus, in the polishing pad of the example provided with the water blocking layer, a high polishing rate of 0.4 μm / min was maintained over a long period of 14,000 minutes or longer.

  Next, a peel test was performed according to the following procedure.

  A sample for measuring peel strength having a width of 25 mm and having the same configuration as the above-described examples and comparative examples was manufactured. The manufactured samples of Examples and Comparative Examples were immersed in a slurry of pH 10.5 and 40 ° C. for 2 days and 7 days, and the peel strength was measured by 180 degree peeling. Each sample was prepared for n = 3, and reproducibility was also confirmed.

  FIG. 3 shows the result. In the sample of the comparative example without the water blocking layer, the peel strength was lower than 10 N / 25 mm for both of the two days and the seven days, whereas in the sample of the example having the water blocking layer, 20 N / 25 mm to 25 N / 25 mm. The peel strength was about twice or more.

  Furthermore, a sample for measuring peel strength having a width of 25 mm having the same configuration as that of the example was manufactured. The sample of the manufactured example was immersed in a slurry of pH 10.5 and 40 ° C. for 48 days, and the peel strength was measured by 180 ° peeling.

  FIG. 4 shows the result. In the examples, the peel strength exceeding 25 N / 25 mm was maintained for 48 days.

  As described above, it was confirmed that the polishing pad of the example suppressed the decrease in the polishing rate and maintained high peel strength as compared with the polishing pad of the comparative example.

  In the above-described embodiment, the polishing layer 2 is a foamed polyurethane. However, as another embodiment of the present invention, as a urethane-impregnated nonwoven fabric obtained by impregnating a urethane resin into a polyamide-based, polyester-based nonwoven fabric, and curing. Also good.

  The thickness of the polishing layer made of this urethane-impregnated nonwoven fabric is preferably about 0.8 mm to 1.5 mm, and the hardness (Asker C) is preferably about 78 to 98.

  The present invention is useful for polishing semiconductor wafers and precision glass substrates.

It is a schematic sectional drawing of a part of polishing pad concerning an embodiment of the invention. It is a figure which shows transition of a polishing rate. It is a figure which shows the result of a peeling strength test. It is a figure which shows a peeling strength test result. It is a schematic sectional drawing of the polishing pad of a prior art example.

Explanation of symbols

2 Polishing layer 3 Double-sided tape 6 Adhesive layer 8 Water stop layer

Claims (7)

A polishing pad having a polishing layer whose surface is pressed against an object to be polished and fixed to a surface plate by a double-sided tape provided on the back side of the polishing layer,
Between the back surface of the polishing layer and the double-sided tape, a water-stopping layer that blocks polishing slurry is provided ,
The water-stop layer is made of a thermal adhesive film that is a hot melt adhesive.
Polishing pad, characterized in that.   The polishing pad according to claim 1, wherein the double-sided tape has an adhesive layer formed on both sides of a base material.   The polishing pad according to claim 1, wherein the polishing layer is foamed polyurethane.   The polishing pad according to claim 1, wherein the polishing layer is obtained by impregnating a nonwoven fabric with polyurethane and curing it. The polishing pad according to any one of claims 1 to 4, wherein a material of the thermal adhesive film is any one of polyamide, polyurethane, polyester, or EVA olefin . The polishing pad according to claim 5, wherein the material of the thermal bonding film is a polyurethane-based material and includes a polyol component and an isocyanate component, and the component ratio is 90 to 70%: 10 to 30% in mol% . The polishing pad according to claim 6, wherein the molecular weight of the polymer of the thermal adhesive film is 2 × 10 ⁴ to 4 × 10 ⁴ in terms of weight average molecular weight .

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