JP5631955B2 - 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

  In the case where both the elimination of the level difference on the surface of the object to be polished and the uniformity of the entire surface are required as the function of the polishing pad, for example, as shown in FIG. 6, the polishing layer 2 and the base layer 3 are provided. A two-layer polishing pad may be used. The underlayer 3 is made of a soft and low elastic modulus material such as a polyurethane-impregnated non-woven fabric obtained by impregnating a non-woven fabric with polyurethane to cure the entire surface of the polishing pad uniformly with the object to be polished. For the purpose of eliminating the level difference on the surface of the object to be polished, a hard and high elastic material, for example, hard foamed polyurethane is used, and both layers 2 and 3 have adhesive layers formed on both sides of the substrate. It is bonded by the double-sided tape 4 or the like.

  The polishing layer 2 made of foamed polyurethane has a large number of pores (pores) due to foaming, and there is a hole having a large diameter that penetrates the polishing layer 2 beyond the thickness of the polishing layer 2.

  In the polishing using such a polishing pad, the polishing slurry supplied to the surface 2a side of the polishing layer 2 passes through a hole penetrating the polishing layer 2 and the adhesive layer of the double-sided tape 4 on the back side of the polishing layer 2 For example, due to the strongly alkaline polishing slurry, the components of the adhesive material layer 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, and the polishing rate is increased. There is a problem of lowering.

  In addition to lowering the polishing rate, the adhesive layer of the double-sided tape 4 elutes, so that the adhesive strength between the polishing layer 2 and the underlayer 3 is weakened, and there is a problem that delamination may occur. is there.

  Such a problem is not limited to the above-mentioned holes due to foaming, but in the case where a processing hole provided in the polishing layer reaches the double-sided tape 4 on the back surface of the polishing layer for the purpose of improving the retention of the polishing slurry. Also occurs in the same way.

  Further, not only the penetration of the polishing slurry from the surface 2a of the polishing layer 2, but also the polishing layer 2 and the lower layer by the penetration of the polishing slurry from the peripheral surface of the base layer 3 such as a polyurethane-impregnated nonwoven fabric into the adhesive layer of the double-sided tape 4 Separation between layers with the formation 3 may occur.

  Further, as shown in FIG. 7, the polishing pad is fixed to the surface plate of the polishing machine by the double-sided tape 4a, but the double-sided tape for fixing the surface plate by the polishing slurry that has permeated from the peripheral surface of the base layer 3. When the adhesive material layer 4a is eluted, the bonding strength between the polishing pad and the double-sided tape 4a is weakened, and there is a problem that the polishing pad may be peeled off from the surface plate.

  The present invention has been made in view of the above points, and an object of the present invention is to suppress a decrease in the polishing rate of a laminated polishing pad and to prevent delamination.

The polishing pad of the present invention is a polishing pad in which a plurality of layers including a polishing layer whose surface is pressed against an object to be polished are laminated via an adhesive layer, and the polishing pad is one of two layers sandwiching the adhesive layer. Between the at least one layer and the adhesive layer, a water blocking layer for blocking the polishing slurry is directly adhered to at least one of the two layers .

Water stop layer has the preferable of the polishing slurry can be completely shut off.

  The adhesive layer is a layer that adheres two layers, and adhesion includes adhesion.

  In the case of providing a plurality of adhesive layers, a water-stopping layer may be provided for all the adhesive layers, but any water-proofing layer may be provided for at least one adhesive layer.

  At least one of the two layers sandwiching the adhesive layer is preferably a polishing layer.

  According to the present invention, since the water blocking layer for blocking the polishing slurry is provided between at least one of the two layers sandwiching the adhesive layer and the adhesive layer, at least of the two layers. It is possible to prevent the polishing slurry from permeating from one layer to the adhesive layer to elute the components of the adhesive layer, to suppress a decrease in the polishing rate, and to prevent peeling between the two layers.

  In one embodiment of the present invention, the water blocking layer is provided between the lowermost layer of the plurality of layers and an adhesive layer for fixing the polishing pad to a surface plate.

  According to this embodiment, since the water blocking layer is provided between the lowermost layer of the polishing pad and the adhesive layer for fixing to the surface plate, the penetration of the polishing slurry from the lower layer to the adhesive layer is suppressed. Thus, it is possible to prevent the components of the adhesive layer from eluting, thereby preventing the polishing pad from peeling from the surface plate.

  In another embodiment of the present invention, the adhesive layer is a double-sided tape in which an adhesive layer is 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 suppressed 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 a preferred embodiment of the present invention, the plurality of layers include the polishing layer and a base layer bonded to the back surface of the polishing layer via the adhesive layer.

  According to this embodiment, since the water stop layer is provided on the polishing layer side, the base layer side, or the polishing layer side and the base layer side of the adhesive layer that bonds the polishing layer and the base layer, the polishing layer side The penetration of the polishing slurry into the adhesive layer or the penetration of the polishing slurry from the base layer side into the adhesive layer can be prevented by the water-stopping layer, whereby the components of the adhesive layer are dissolved and the surface of the polishing layer is dissolved. It is possible to suppress the reduction of the polishing rate due to adhesion to the surface, and it is possible to prevent delamination between the polishing layer and the base layer.

  As the underlayer, a non-woven fabric impregnated with polyurethane and cured, foamed polyurethane, rubber sheet or the like is preferable.

  As the polishing layer, foamed polyurethane, non-woven fabric impregnated with polyurethane and cured are preferred.

  Moreover, it is preferable that the elasticity modulus of a base layer is smaller than the elasticity modulus of a grinding | polishing layer.

  In preferable embodiment of this invention, the said water stop layer is a thermobonding film.

  According to this embodiment, the thermoadhesive film can be heated and melted and adhered to the back surface of the polishing layer or the like 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, the water-stopping layer for blocking the polishing slurry is provided between at least one of the two layers sandwiching the adhesive layer and the adhesive layer. It is possible to prevent polishing slurry from penetrating from at least one layer into the adhesive layer and to dissolve the components of the adhesive layer, to suppress a decrease in the polishing rate and to prevent peeling between the two layers.

It is a schematic sectional drawing of the polishing pad of embodiment of this invention. It is a schematic sectional drawing of the polishing pad of other embodiment of this invention. It is a schematic sectional drawing of the polishing pad of other embodiment of this invention. It is a schematic sectional drawing of the polishing pad of other embodiment of this invention. It is a figure which shows the result of a peeling strength test. It is a schematic sectional drawing of the polishing pad of a prior art example. It is a schematic sectional drawing of the polishing pad of a prior art example.

  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 1 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 1 according to this embodiment is a two-layer pad including a polishing layer 2 whose surface 2 a is pressed against an object to be polished such as a silicon wafer, and a base layer 3, and is provided between the polishing layer 2 and the base layer 3. Is provided with a double-sided tape 4 as an adhesive layer.

  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 polishing layer 2 has a large number of pores (pores) due to foaming, and 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 foundation layer 3 of this embodiment is a polyurethane-impregnated nonwoven fabric obtained by impregnating a nonwoven fabric with polyurethane and curing it.

  As the urethane resin, the same urethane resin as that of the polishing layer 2 such as polyester, polyether, or polycarbonate can be used. As the nonwoven fabric, for example, a polyamide-based, polyester-based or the like nonwoven fabric can be used.

  A double-sided tape 4 as an adhesive layer between the polishing layer 2 and the base layer 3 includes a resin film as a base material, for example, a PET (polyethylene terephthalate) film, and an acrylic adhesive layer on both sides, for example. It has.

  The pressure-sensitive adhesive material of the pressure-sensitive adhesive layer is fluidized by applying pressure at room temperature and develops a pressure-sensitive adhesive function, and the density and cross-linking density of the pressure-sensitive adhesive material are compared with the thermal adhesive film constituting the water-stopping layer 5 described later. Therefore, 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 of the double-sided tape 4 through the holes penetrating the polishing layer 2, and the components of the adhesive material layer are eluted. In order to prevent this, a water blocking layer 5 is provided between the back surface of the polishing layer 2 and the double-sided tape 4.

  In this embodiment, the water-stopping layer 5 is composed of a thermal adhesive film that is a hot melt adhesive. Examples of the thermal adhesive film include polyamide-based, polyurethane-based, polyester-based, and EVA (Ethylene vinyl acetate) olefins. Any material of the system can be used.

  In this embodiment, since the polishing layer 2 is foamed polyurethane, the same polyurethane-based thermal adhesive film is used as the water blocking layer 5, 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%.

  Further, the molecular weight of the polymer of the heat bonding film is preferably 2 × 10 4 to 4 × 10 4 in terms of weight average molecular weight, and particularly preferably 2.5 × 10 4 to 3.5 × 10 4.

  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 dissolve into the polishing slurry like the adhesive layer of the double-sided tape 4.

  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 5 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 5 can be provided on the back side of the polishing layer 2 by hot pressing, for example, by plane 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 1 of FIG. 1 can be obtained by thermocompression bonding the base layer to the polishing layer 2 to which the water blocking layer 5 is bonded with the double-sided tape 4.

  Since the double-sided tape 4 has the adhesive material layer as described above, it is bonded with sufficient strength to the water stop layer 5 on the back surface of the polishing layer 2 by this adhesive material layer.

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

  A urethane-based thermal adhesive film (polyol component: isocyanate component (mol%), approximately 85%: 15%, weight average molecular weight 2.8 × 104) is applied to the back surface of the polishing layer made of polyurethane that has been chemically foamed. The sample of the polishing pad of the example was manufactured by heat-bonding as a water-stopping layer, and then thermocompression bonding a base layer made of polyurethane-impregnated nonwoven fabric with a double-sided tape. Further, a base layer made of polyurethane-impregnated non-woven fabric was thermocompression bonded to the back surface of the chemically-fired polyurethane polishing layer with a double-sided tape to produce a comparative polishing pad sample similar to the conventional example.

  Next, polishing was performed using the polishing pads of Examples and Comparative Examples under the following polishing conditions, and the polishing rate and uniformity were evaluated.

The uniformity was evaluated by measuring the film thickness distribution at 49 points in the polished surface after polishing an 8-inch TEOS film wafer and dividing the standard deviation by the average value.
<Polishing conditions>
Polishing slurry: fumed silica slurry, pH 11
・ Polisher: 24-inch surface plate, polisher ・ Platen rotation speed: Up; 50 rpm / Down; 50 rpm
・ Slurry flow rate: 200mL / min
・ Polishing pad Example (two-layer polishing pad with water blocking layer)
Comparative example (two-layer polishing pad without water blocking layer)
・ Pressure: 350gf / cm2
・ Polishing time: 2 min
<Polishing result>
The polishing rate is less than 4,000 kg / min after polishing of the comparative polishing pad and 300 batches (600 minutes).
-Uniformity exceeds 10% after polishing 400 batches (800 minutes).
-After 500 batches (1,000 minutes), partial delamination was observed.
The polishing rate is maintained at 4,000 kg / min even after polishing of the polishing pad of the example and 500 batches (1,000 minutes).
-Even after 500 batches (1,000 minutes), the uniformity is less than 7%.
-Even after 500 batches (1,000 minutes), no delamination was observed.

  As shown in the above polishing results, the polishing rate of the comparative example having no water blocking layer decreases the polishing rate, and after 600 minutes of polishing, the polishing rate is less than 4,000 kg / min. In the polishing pad of the example having a layer, a polishing rate of 4,000 kg / min could be maintained even after polishing for 1,000 minutes.

  Further, in the polishing pad of the comparative example, partial delamination was observed after polishing for 1,000 minutes, whereas in the polishing pad of the example, delamination was not recognized.

  Further, with respect to uniformity, after polishing for 800 minutes, the polishing pad of the comparative example exceeded 10%, whereas the polishing pad of the example was less than 7%.

  In this embodiment, the water blocking layer 5 is provided between the polishing layer 2 and the double-sided tape 4, but as another embodiment of the present invention, as shown in FIG. You may provide between. According to this configuration, it is possible to prevent the adhesive slurry of the double-sided tape 4 from being eluted by blocking the polishing slurry penetrating from the peripheral surface of the base layer 3 with the water blocking layer 5. Further, as another embodiment of the present invention, as shown in FIG. 3, water blocking layers 5 may be provided on both sides of the double-sided tape 4.

  In each of the above-described polishing pads, the lower surface of the underlayer 3 is fixed to the surface plate of the polishing machine with a double-sided tape. The polishing slurry penetrates from the peripheral surface of the underlayer 3 and the adhesive layer of the double-sided tape is used. When the components are eluted, the adhesive strength between the polishing pad and the double-sided tape is weakened, and the polishing pad may be peeled off from the surface plate.

  Therefore, as another embodiment of the present invention, as shown in FIG. 4, a water blocking layer 5a may be provided between the lower surface of the base layer 3 and the double-sided tape 4a for fixing to the surface plate. Good.

  As a reference, a single layer polishing pad was subjected to a peel test between a polishing pad and a sample with a waterproof layer between the polishing pad and a double-sided tape for fixing to a surface plate, and a sample without a waterproof layer. It was.

  That is, a 25 mm wide peel strength measurement sample obtained by thermally bonding a water-stopping layer to a polishing pad made of a single layer foamed polyurethane and then thermocompression-bonding a double-sided tape; A sample for measuring the peel strength having a width of 25 mm, which was thermocompression-bonded with a tape, was produced.

  Each sample was 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. 5 shows the result. In the sample without the water-stopping layer, the peel strength was less than 10 N / 25 mm for both 7 days, whereas in the sample having the water-stopping layer, 20 N / 25 mm to 25 N / 25 mm, about twice or more The peel strength was shown.

  Thus, it turns out that peeling strength improves by providing a water stop layer between a polishing pad and the double-sided tape for fixation to a surface plate.

  In each of the above-described embodiments, the present invention is applied to a polishing pad having a two-layer structure of a polishing layer and an underlayer. However, the present invention can be similarly applied to a polishing pad having a multilayer structure of three or more layers.

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

2 Polishing layer 3 Base layer 4, 4a Double-sided tape 5, 5a Water-stopping layer

Claims (12)

A plurality of layers including a polishing layer whose surface is pressed against an object to be polished is a polishing pad laminated via an adhesive layer,
A waterproof layer that blocks polishing slurry is directly adhered to at least one of the two layers between at least one of the two layers sandwiching the adhesive layer and the adhesive layer. A polishing pad provided.   The polishing pad according to claim 1, wherein the water blocking layer is provided between a lowermost layer of the plurality of layers and an adhesive layer for fixing the polishing pad to a surface plate.   The polishing pad according to claim 1, wherein the adhesive layer is a double-sided tape in which an adhesive material layer is formed on both surfaces of a base material.   The polishing pad according to any one of claims 1 to 3, wherein the plurality of layers include the polishing layer and a base layer bonded to the back surface of the polishing layer via the adhesive layer.   The polishing pad according to claim 4, wherein the underlayer is obtained by impregnating a nonwoven fabric with polyurethane and curing it.   The polishing pad according to claim 4, wherein the foundation layer is polyurethane foam.   The polishing pad according to claim 4, wherein the foundation layer is a rubber sheet.   The polishing pad according to claim 4, wherein an elastic modulus of the base layer is smaller than an elastic modulus of the polishing layer.   The polishing pad according to claim 1, wherein the polishing layer is foamed polyurethane.   The polishing pad according to any one of claims 1 to 8, 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 10, wherein the water blocking layer is a thermal adhesive film.   The polishing pad according to claim 11, wherein a material of the thermal adhesive film is any one of polyamide, polyurethane, polyester, or EVA olefin.

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