Ultra fine fiber polishing pad and method for manufacturing the same

Abstract

A method is provided for making a polishing pad. In the method, ultrafine fiber-generating fibers are made into a non-woven fabric with two sides. At least one of the sides of the non-woven fabric is made a dense layer. The non-woven fabric is coated with a polymer. Because of the dense layer, the polymer cannot penetrate the non-woven fabric. The ultrafine fiber-generating fibers are converted to ultrafine fibers. Since the dense layer prevents the polymer from penetrating the ultrafine fiber-generating fibers, the ultrafine fibers remain a high concentration of fiber. The ultrafine fibers are transformed into nap. Therefore, the polishing pad is made with a polishing layer that includes the nap. The concentration of fiber of the polishing layer is higher than 80%.

Description

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to a polishing pad for polishing the surfaces of objects such as semiconductors, storage medium substrates, integrated circuits and electro-optical panels, and relates to a method for making the polishing pad.

2. Related Prior Art

In the semiconductor industry, there is a trend toward the reduction of the semiconductor characteristics and the increasing of the superficial planarity. In detail, it is preferred to provide a surface with an even form by reducing the quantity and size of superficial flaws.

Polishing is often used to turn a rough surface into a smooth surface. Amid other polishing methods, there are fixed-type polishing methods and suspension-type polishing methods.

In a fixed-type polishing method, used is a fixed-type polishing pad with a polishing layer on a substrate. The substrate is a PET foil for example. The polishing layer includes polishing particles and an adhesive for fixing the polishing particles to the substrate. Although providing a high polishing rate, the fixed-type polishing pad causes grave impacts on the polished surface, and it is difficult to clean the polished surface of debris. Hence, many large and deep scratches are made in the polished surface, and this is not desirable.

In a suspension-type polishing method, used is a suspension-type polishing pad with a polishing solution on a substrate. The polishing solution is a suspension with polishing particles suspended in a solvent. For the use of the solvent, it is easy to clean the polished surface of debris. As suspended in the solvent, the polishing particles freely move. Hence, the impacts on the polished surface by the suspended polishing particles can readily be adjusted. Moreover, it is easy to control the result by changing the suspension-type polishing pad. Various velvets and fabrics are used in the suspension-type polishing pad to achieve adequate effects according to different purposes.

In the suspension-type polishing method, the polishing solution is provided between the substrate and the polished surface, and the substrate is regularly rotated related to the polished surface. The substrate of the suspension-type polishing pad may include urethane or polyurethane plastics filled in a blanket made of polyester. Alternatively, the blanket may be made of natural fibers such as wool for instance.

Chemical mechanical polishing (“CMP”) is often used in a typical machine for polishing semiconductor devices. In a CMP method, a polishing pad includes a polishing solution on a substrate. The polishing pad is used to polish the surfaces of semiconductor devices. The polishing solution is provided between a wafer and the substrate, and the wafer is pressed on and rotated relative to the polishing pad while chemical substances in the polishing solution and the pressure and rate between the wafer and the polishing pad and temperature are under control. The polishing solution includes polishing particles capable of mechanically polishing the surface of the wafer when mixed with the chemical substances. Between the chemical substances and the surface of the wafer, chemical reactions such as removal and oxidation happen. The polishing pad often includes a continuous substrate. When the wafer is rotated relative to the polishing pad, some redundant material is mechanically removed from the surface of the wafer by the polishing particles of the polishing liquid while some other redundant material is chemically removed from the surface of the wafer by the solvent of the polishing liquid.

Disclose in US Patent Application Publication 2002/0013984A1 is a sheet for texturing and a method of producing the same. The method includes four steps among which the second and third steps can be interchanged.

Firstly, a non-woven fabric is composed of ultrafine fiber-generating fibers (a) and (b).

Secondly, an elastomer is filled in the non-woven fabric so as to form a sheet.

Thirdly, the ultrafine fiber-generating fibers (a) are converted to bundles of ultrafine fibers while the ultrafine fiber-generating fibers (b) are converted to bundles of ultrafine fibers not more than 0.03 dtex in fineness.

Fourthly, at least one side of the sheet is grinded so that the ultrafine fibers under 0.03 dtex in fineness form nap.

A polishing layer is formed on the side of the sheet on which the nap is formed. However, in the step of converting the fibers (a) and (b) to the ultrafine fibers, since the polishing layer includes the polymer and the fibers, the polishing layer cannot adequately be opened so that the nap is not fine enough and that the nap may get entangled. If the polishing layer contains too much polymer, when it is used to polish an object, particles (polishing synthetic materials, sheet materials, polishing particles, particles of sheet materials and debris of the object) will stick to the polymer of the polishing layer and cannot smoothly be removed by a polishing solution. These redundant particles will wear away the object and jeopardize the polishing of the object.

The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.

SUMMARY OF INVENTION

It is the primary objective of the present invention to provide a polishing pad with ultrafine fibers that are highly opened and therefore do not cause damages to an object.

According to the present invention, a method is provided for making a polishing pad. In the method, ultrafine fiber-generating fibers are made into a non-woven fabric with two sides. At least one of the sides of is made a dense layer. The dense layer may be made by heating the side or coating the side with a dissolvable substance. The non-woven fabric is coated with a polymer. Because of the dense layer, the polymer cannot penetrate the non-woven fabric. The ultrafine fiber-generating fibers are converted to ultrafine fibers. Since the dense layer prevents the polymer from penetrating the ultrafine fiber-generating fibers, the ultrafine fibers includes a high concentration of fiber. The ultrafine fibers are transformed into nap. A polishing pad is completed.

In use, the nap of a polishing layer of the polishing pad will not get entangled and cause damages to an object polished by the polishing pad.

The dense layer can be made by heating the surface of the non-woven fabric higher than 100 degrees Celsius so that the surfaces of the ultrafine fiber-generating fibers are transformed and made dense.

Alternatively, the dense layer can be made by coating the non-woven fabric with a dissolvable substance such as polyvinyl alcohol, methyl cellulose, sodium bicarbonate and amylase. The dissolvable substance can be washed away with water.

In an aspect of the present invention, a method is provided making a polishing pad. The method includes the step of making ultrafine fiber-generating fibers into a non-woven fabric with two sides, the step of making at least one of the sides a dense layer, the step of coating the non-woven fabric with a polymer that forms a coating, the step of converting the ultrafine fiber-generating fibers to ultrafine fibers and the step of processing the coating on the dense layer so that the fineness of the ultrafine fibers on the dense layer is lower than 0.05 dtex.

In an aspect of the present invention, a method is provided making a polishing pad. The method includes the step of making ultrafine fiber-generating fibers into a non-woven fabric with two sides, the step of coating at least one of the sides with a dissolvable substance, the step of coating the non-woven fabric with a polymer that forms a coating, the step of washing away the dissolvable substance, the step of converting the ultrafine fiber-generating fibers to ultrafine fibers and step of processing the coating on the dense layer so that the fineness of the ultrafine fibers on the dense layer is lower than 0.05 dtex.

The sequence of the step of washing away the dissolvable substance and the step of converting the ultrafine fiber-generating fibers to ultrafine fibers is changeable.

In still another aspect of the present invention, a polishing pad includes ultrafine fibers and a polymer that binds the ultrafine fibers. The polishing pad includes a polishing layer that is made dense in order to include a concentration of fiber higher that of the remaining portion of the polishing pad.

The polishing pad can be used to polish any substrate made of glass, metal, metal oxide, metal alloy or semi-conductor or any combination thereof.

The substrate may include any proper metal such as copper, aluminum, tantalum, titanium, tungsten, gold, platinum, iridium, ruthenium and any combination thereof such as alloy and mixture.

The substrate may include any proper metal oxide such as aluminum oxide, silicon oxide, titanium oxide, cerium oxide, zirconium oxide, germanium oxide, magnesium oxide and any combination thereof.

The substrate may include any proper metal alloy such as metal nitride (such as tantalum nitride, titanium nitride and tungsten nitride), metal carbide (such as silicone carbide and tungsten carbide), nickel-phosphorous, aluminum-silicone-boron, silicone-boron glass, silicone-phosphorous glass, silicone-phosphorous-boron glass, silicone-germanium alloy, silicone-germanium-carbon alloy.

The substrate may include any proper semi-conductor such as mono-crystalline silicone, multi-crystalline silicone, amorphous silicone, silicon-on-insulator and gallium arsenide.

Other objectives, advantages and features of the present invention will become apparent from the following description referring to the drawings.

BRIEF DESCRIPTION OF DRAWINGS

A polishing pad according to the preferred embodiment of the present invention will be described referring to the drawings.

FIG. 1 is a SEM view of a conventional polishing pad.

FIG. 2 is a SEM view of the polishing pad according to the preferred embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

In a method according to a general concept of the present invention, ultrafine fiber-generating fibers are made into a non-woven fabric with two sides. At least one of the sides of the non-woven fabric is made a dense layer. The non-woven fabric is coated with a polymer such as a polyurethane resin, a polyvinylchloride resin, a polystyrene resin, a polyvinyl resin, a polyamide resin, a propylene resin and a vinyl-vinylacetate resin. Because of the dense layer, the polymer cannot penetrate the non-woven fabric.

The dense layer can be made by heating the side of the non-woven fabric at a temperature higher than 100 degrees Celsius so that the surfaces of the ultrafine fiber-generating fibers are transformed and made dense. While being heated, the side of the non-woven fabric can be pressed.

Alternatively, the dense layer can be made by coating the non-woven fabric with a dissolvable substance such as polyvinyl alcohol, methyl cellulose, sodium bicarbonate and amylase. The concentration of the dissolvable substance is 5% to 15% and provided with a roller at 100 to 200 g/m². Thus, when the polymer is coated on the non-woven fabric, the polymer cannot penetrate the non-woven fabric since the dissolvable substance has occupied the superficial space. The dissolvable substance can be washed away with water.

The ultrafine fiber-generating fibers are converted to ultrafine fibers. Since the dense layer prevents the polymer from penetrating the ultrafine fiber-generating fibers, the ultrafine fibers includes a high concentration of fiber. The ultrafine fibers are transformed into nap. A polishing pad is completed. In use, the nap of a polishing layer of the polishing pad will not get entangled and cause damages to an object polished by the polishing pad.

According to a first embodiment of the present invention, ultrafine fiber-generating fibers are made into a non-woven fabric. The side of the non-woven fabric is heated at 120 degrees Celsius and hence made dense. The non-woven fabric is coated with a polyurethane resin that forms a coating. At least one of the sides of the non-woven fabric is grinded so that a polishing pad is formed with a polishing layer that includes nap less than 0.05 dtex. The dense layer remains a high concentration of fiber.

According to a second embodiment of the present invention, ultrafine fiber-generating fibers are made into a non-woven fabric. A gravure roll is used to coat the non-woven fabric with a 5% to 15% dissolvable solution of methyl cellulose at 100 to 200 g/m². The side of the non-woven fabric is made dense in order to prevent polymers from penetrating the non-woven fabric. The non-woven fabric is coated with a polyurethane resin that forms a coating. The non-woven fabric is washed in order to remove the methyl cellulose. At least one of the sides of the non-woven fabric is grinded so that a polishing pad is formed with a polishing layer that includes nap less than 0.05 dtex. The dense layer still includes a high concentration of fiber.

Referring to FIG. 2, there is shown a polishing pad made in a method according to the present invention. The nap on the polishing layer is even and dense. The concentration of fiber of the dense layer is higher than 80%. On the contrary, referring to FIG. 1, the concentration of polyurethane of a polishing pad made in a conventional method is 45% to 50%. The concentration of polyurethane of the polishing pad of the present invention is 30% less than that of the conventional polishing pad. The polishing pad of the present invention is more flexible and hangs better than the conventional polishing pad. The polishing pad of the present invention makes fewer scratches than the conventional polishing pad. The scratches made by the polishing pad of the present invention are lower than 1000/μm². The scratches made by the conventional polishing pad are 2000/μm² to 25000/μm².

It is noted that the ultrafine fiber-generating fibers may be conjugate fibers or composite fibers.

The present invention has been described by the detailed description of the embodiments. Those skilled in the art can derive variations from the embodiments without departing from the scope of the present invention. Therefore, the embodiments shall not limit the scope of the present invention defined in the claims.

Claims

1. A polishing pad comprising ultrafine fibers and a polymer that binds the ultrafine fibers, the polishing pad comprising a polishing layer that is made dense in order to include a concentration of fiber higher that of the remaining portion of the polishing pad.

2. The polishing pad according to claim 1 wherein the concentration of fiber of the polishing layer is higher than 80%.

3. The polishing pad according to claim 1 wherein the fineness of the ultrafine fibers is lower than 0.05 dtex.

4. A method for making a polishing pad, the method comprising the following steps of:

making ultrafine fiber-generating fibers into a non-woven fabric with two sides;

making at least one of the sides into a dense layer;

coating the non-woven fabric with a polymer that forms a coating;

converting the ultrafine fiber-generating fibers to ultrafine fibers; and

processing the coating on the dense layer so that the fineness of the ultrafine fibers on the dense layer is lower than 0.05 dtex.

5. The method according to claim 4 wherein the step of making the dense layer includes the step of heating the side of the non-woven fabric at a temperature higher than 100 degrees Celsius.

6. The method according to claim 5 wherein the step of making the dense layer includes the step of pressing the side of the non-woven fabric while heating the side of the non-woven fabric.

7. The method according to claim 4 wherein the step of processing the coating comprises the step of grinding the coating.

8. A method for making a polishing pad, the method comprising the following steps of:

making ultrafine fiber-generating fibers into a non-woven fabric with two sides;

coating at least one of the sides with a dissolvable substance;

coating the non-woven fabric with a polymer that forms a coating;

washing away the dissolvable substance;

converting the ultrafine fiber-generating fibers to ultrafine fibers; and

processing the coating on the dense layer so that the fineness of the ultrafine fibers on the dense layer is lower than 0.05 dtex.

9. The method according to claim 8 wherein the dissolvable substance is selected from a group consisting of polyvinyl alcohol, methyl cellulose, sodium bicarbonate and amylase.

10. The method according to claim 8 wherein the step of processing the coating comprises the step of grinding the coating.

11. The method according to claim 8 wherein the sequence of the step of washing away the dissolvable substance and the step of converting the ultrafine fiber-generating fibers to ultrafine fibers is changeable.