SUB-PAD FOR POLISHING PAD, POLISHING PAD INCLUDING SAME, AND METHOD FOR MANUFACTURING SUB-PAD FOR POLISHING PAD

Description

TECHNICAL FIELD

The present application claims the benefit of priority based on Korean Patent Application No. 10-2022-0046457 filed on Apr. 14, 2022, all the contents of which are incorporated herein as part of the present application.

The present invention relates to a sub-pad for polishing pad, a polishing pad including the same, and a method for manufacturing the sub-pad for the polishing pad.

BACKGROUND ART

A chemical mechanical polishing (CMP) process is, for example, a core process for planarizing and mirror-finishing wafers in a semiconductor industry, and performs polishing by the mechanical and chemical action of a polishing pad and a slurry containing nanoparticles.

The chemical mechanical polishing (CMP) pad consists of a top pad that is brought into contact with the wafer to perform polishing, and a soft sub-pad for load distribution as shown in FIG. 1. Since the top pad is used in a frequent contact environment with nanoparticles, wafers, and diamond conditioners, polyurethane which has strong mechanical properties and excellent chemical resistance is mainly used. On the other hand, the sub-pad has a porous structure in which soft polyester fiber material is impregnated with polyurethane to perform a buffering function of the load applied to the top pad (ex. SUBA IV, DuPont).

However, slurry may penetrate into the pad side surface due to a porous structure of such a conventional sub-pad, which may change the mechanical properties of the polishing pad during the polishing process.

Therefore, in order to improve this drawback, an “edge sealing” technique is applied to the sub-pad (U.S. Pat. No. 6,464,576B1). However, the above-mentioned “edge sealing” process increases the manufacturing cost of the sub-pads, and is also difficult to provide sufficient effects.

DISCLOSURE

Technical Problem

The present invention has been devised to solve the above-mentioned problems of the related art, and an object thereof is to provide a sub-pad for a polishing pad that can effectively prevent slurry from penetrating through the side surface during the polishing process.

Another object of the present invention is to provide a polishing pad that effectively prevents changes in physical properties caused by the slurry during the polishing process and provides excellent durability, by including the sub-pad.

Yet another object of the present invention is to provide a method for manufacturing a sub-pad for a polishing pad, which can manufacture a sub-pad with excellent quality by a simple method.

Technical Solution

To achieve the above objects, the present invention provides a sub-pad for a polishing pad, the sub-pad being stacked under a top pad that is brought into contact with a wafer to perform polishing, and including a nanofiber nonwoven fabric pad, wherein the nanofiber nonwoven fabric pad has a nanofiber density of an outer circumferential part that is formed to be 1.2 to 5 times higher than the nanofiber density of other portions inside the outer circumferential part.

In addition, the present invention provides a polishing pad including:

• • a top pad that is brought into contact with a wafer to perform polishing; and
  • a sub-pad of the present invention stacked under the top pad.

In addition, the present invention provides a method for manufacturing a sub-pad for the polishing pad, the method comprising the steps of:

• • a) electrospinning a polymer solution;
  • b) recovering a nanofiber nonwoven fabric formed by the electrospinning; and
  • c) thermally compressing the nanofiber nonwoven fabric,
  • wherein the collector during electrospinning of the step a) includes a circular electrode corresponding to the outer circumferential part of the sub-pad.

Advantageous Effects

The sub-pad for a polishing pad of the present invention provides the effect of effectively preventing slurry from penetrating through the side surfaces during the polishing process.

In addition, the polishing pad of the present invention effectively prevents changes in physical properties due to slurry during the polishing process by including the above sub-pad, thereby providing excellent durability.

In addition, a method for manufacturing a sub-pad for a polishing pad of the present invention provides a method for manufacturing a sub-pad having excellent quality by a simple method.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram schematically showing a shape of a sub-pad for a polishing pad as an embodiment of the present invention, and a configuration of a polishing pad including the same.

FIG. 2 is a diagram schematically showing a shape of a sub-pad for a polishing pad according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view schematically showing a shape of a polishing pad according to an embodiment of the present invention.

FIG. 4 is a diagram schematically showing an electrospinning apparatus used in a method for manufacturing a sub-pad for a polishing pad according to the present invention.

FIG. 5 is a diagram schematically showing a shape of a nanofiber nonwoven fabric manufactured by a method for manufacturing a sub-pad for a polishing pad according to the present invention.

FIG. 6 is a diagram schematically showing a thermal compression step in the method for manufacturing a sub-pad for the polishing pad according to the present invention.

FIG. 7 is a diagram illustrating a photograph of a nanofiber nonwoven fabric manufactured by the method for manufacturing a sub-pad for a polishing pad according to the present invention.

FIG. 8 is a graph illustrating a comparison of the results of a mechanical indentation test of a sub-pad for a polishing pad according to the present invention.

BEST MODE

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that a person having ordinary knowledge in the technical field to which the present invention pertains can easily carry out the present invention. However, the present invention can be implemented in various different forms and is not limited to the embodiments described herein. Similar parts are denoted by the same reference numbers throughout the specification.

When a certain component is said to be “connected, equipped, or installed” to another component, it should be understood that it may be directly connected or installed to the other component, but there may be other components between them.

In the present invention, the term “comprising” means that other components may be further included in addition to an included component, but it also means that it consists of only the above-mentioned components without other components.

The sub-pad for polishing pad of the present invention is a sub-pad stacked under a top pad that is brought into contact with a wafer to perform polishing, and includes a nanofiber nonwoven fabric pad, wherein the nanofiber nonwoven fabric pad has a characteristic that a nanofiber density of an outer circumferential part is formed to be 1.2 to 5 times higher than the nanofiber density of another portions inside the outer circumferential part.

Conventional sub-pads have a porous structure to perform a role of buffering the load applied to the top pad that is brought into contact with a wafer to perform polishing. However, due to the porous structure, there is a problem that the mechanical properties are changed by the slurry that penetrates into the side surface of the pad during the polishing process. Therefore, in order to solve such a problem, an “edge sealing” technique is applied to the sub-pad. However, the application of the “edge sealing” technique causes an increase in cost and has the drawback of not being effectively enough.

The sub-pad of the present invention is manufactured using a nanofiber nonwoven fabric, and is characterized in that the nanofiber density of the outer circumferential part is formed to be higher than that of other portions other than the outer circumferential part to solve the above-mentioned problems of the related art.

In the sub-pad of the present invention, the nanofiber density of the outer circumferential part is more preferably 1.5 to 5 times higher than the nanofiber density of other portions inside the outer circumferential part.

The outer circumferential part of the sub-pad provides an effect of effectively preventing the penetration of the polishing slurry due to its high density and low porosity.

In an embodiment of the present invention, the nanofiber nonwoven fabric pad may preferably contain a hydrophobic polymer, and more preferably contain superhydrophobic polymer fibers to prevent the penetration of the slurry. Although the hydrophobic polymer is not particularly limited, for example, at least one selected from the group consisting of polystyrene, Teflon (PTFE, Polytetrafluoroethylene), or the like may be used. When the hydrophobic or superhydrophobic polymer as described above is contained, the penetration of the slurry into the sub-pad may be more effectively prevented.

The hydrophobic or superhydrophobic polymer may be included in an amount of 50 to 99 wt %, more preferably 65 to 99 wt %, on the basis of a total weight of the entire sub-pad. The sub-pad may also include polymer components that are not hydrophobic polymers and other additives in the content other than the content described above. The other additives may be components that are added during electrospinning, for example, components that impart electrical conductivity to the nanofibers.

In an embodiment of the present invention, the nanofiber nonwoven fabric may be used as a sub-pad as it is, or may be used by further performing hydrophobic or superhydrophobic coating treatment, edge sealing, or the like, by a method that is known in the field.

As shown in FIG. 3, a polishing pad 200 of the present invention includes a top pad 20 that is brought into contact with a wafer to perform polishing; and a sub-pad 100 of the present invention stacked under the top pad 20.

The top pad 20 and the sub-pad 100 may be stacked by a method known in the field. For example, they can be bonded by a method for forming an adhesive layer 40 using an adhesive or adhesive tape. It is also possible to bond them by a method for directly coating a composition for forming the top pad 20 on the upper part of the sub-pad 100.

As an embodiment of the present invention, the lower surface of the sub-pad 100 may further include an adhesive layer 50 for fixing the polishing pad to the platen. The adhesive layer is usually formed of a double-sided adhesive tape, but is not limited thereto. In addition, a release film 30 may be further provided on the lower surface of the adhesive layer 50.

As the top pad 20, a polyurethane pad having strong mechanical properties and excellent chemical resistance is generally used because it is used in a frequent contact environment with nanoparticles contained in the polishing slurry, wafers, and diamond conditioners. In the present invention, since the polishing pad 200 is characterized by including the sub-pad 100 of the present invention, the type of the top pad 20 is not limited, and top pads known in the field may be used without limitation.

In an embodiment of the present invention, the cross section of the outer circumferential part of the sub-pad 100 may be stacked in a form exposed to the outer circumferential surface of the polishing pad 200 as shown in FIG. 3.

The present invention also provides a method for manufacturing a sub-pad for a polishing pad of the present invention.

The manufacturing method includes the steps of:

• • a) electrospinning a polymer solution;
  • b) recovering the nanofiber nonwoven fabric formed by the electrospinning; and
  • c) thermally compressing the nanofiber nonwoven fabric,
  • wherein the collector during electrospinning of the step a) is characterized by including a circular electrode corresponding to the outer circumferential part of the sub-pad.

The circular electrode functions to allow more nanofibers to be stacked on the top of the electrode during electrospinning. That is, since more nanofibers are stacked on the top of the circular electrode as described above compared to a portion in which the electrode is not formed, the sub-sheet formed in this way is formed so that nanofiber density on the outer circumferential part is higher than the density of a portion excluding the outer circumferential part.

In an embodiment of the present invention, the circular electrode may be printed on the surface of the electrospinning-induced film. The printing method of the electrode may be performed by a method known in the art, and for example, may be performed by a screen printing method.

The circular electrode may be formed using a conductive material, and the conductive material is not particularly limited, and for example, a silver (Ag) electrode may be used.

All the contents described about the sub-pad for the polishing pad may be applied to the manufacturing method of the present invention. Therefore, overlapping contents below will be omitted.

In an embodiment of the present invention, the polymer solution of the step a) may be manufactured according to a method for manufacturing an electrospinning solution known in the art.

In the present invention, since it is preferable for the sub-pad to contain a hydrophobic or superhydrophobic polymer to prevent the penetration of the slurry, the polymer solution may be manufactured to contain a hydrophobic or superhydrophobic polymer. The hydrophobic or superhydrophobic polymer is not particularly limited, but may be, for example, one or more type selected from the group consisting of polystyrene, Teflon (PTFE, Polytetrafluoroethylene), etc. In particular, since it is preferable for the polymer solution to have electrical conductivity, the polymer solution may further contain components that can impart electrical conductivity to the solution. As the component that imparts the electrical conductivity, components known in the art may be used without limitations, and for example, when a polystyrene is used, it may make it have electrical conductivity by adding a small amount of nitric acid.

In addition, when a Teflon is used, it is preferable to be used by mixing with other polymer components, and for example, it may be used by mixing it with PVA (Polyvinyl Alcohol) component. At this time, the Teflon and PVA may be preferable to be used by mixing in a weight ratio of 1:0.5 to 1.

In an embodiment of the present invention, the method may be performed in a manner of stacking two or more nanofiber nonwoven fabrics recovered in the step b) such that high density portions of the nanofibers formed on the circular electrode overlap each other, and thermally compressing the stacked nanofiber nonwoven fabrics in the step c).

In an embodiment of the present invention, the thermal compression of the step c) may be performed by a method known in the art, as shown in FIG. 6. The thermal compression may be performed by compressing while heating at the glass transition temperature of the nanofibers. The density of the nanofibers may be further increased by the thermal compression.

In addition, when two or more nanofiber nonwoven fabrics recovered in the step b) are stacked such that the high density portions of the nanofibers formed on the top of the circular electrode overlap each other, and when thermally compressed, each nanofiber nonwoven fabric is fused to each other and is firmly bonded.

In an embodiment of the present invention, as shown in FIG. 4, the circular electrodes are formed in plural on the surface of an electrospinning-induced film, and each electrode may be electrically connected to each other by a conductive material.

In addition, the electrospinning-induced film may collect nanofibers spun while moving horizontally, or collect nanofibers spun while rotating in the state of being wound around a circular drum (FIG. 4). In this case, the circular drum may be included in the collector as a work die.

When the electrospinning-induced film collects nanofibers spun while moving horizontally, the electrospinning-induced film may, for example, move while being fixed to a conveyor belt. In this case, the collector may further include a conveyor device as a work die.

When electrospinning is performed by the method of the present invention to form a nanofiber nonwoven fabric as described above, the shape of the nanofiber nonwoven fabric may be formed as shown in FIG. 5(a). At this time, when the nanofiber nonwoven fabric is separated from the electrospinning-induced film, a nanofiber nonwoven fabric in the form shown in FIG. 5(b) may be obtained. The nanofiber nonwoven fabric may be stacked by being folded or cut so that the high density portions of nanofiber formed on the top of circular electrode overlap each other. Thereafter, the stacked nanofiber nonwoven fabric may be thermally compressed to manufacture a nanofiber nonwoven fabric.

The nanofiber nonwoven fabric manufactured above may be used as a sub-pad by cutting the outer end of the outer circumferential part of the high density portion of the nanofibers.

The sub-pad may be directly stacked with a top pad to be used as a polishing pad, or the sub-pad may also be used after performing a hydrophobic or superhydrogenation coating treatment, edge seal treatment, etc. by a method known in the art.

Hereinafter, the present invention will be described in detail with examples to specifically describe the present invention. However, the embodiment according to the present invention may be modified into various other forms, and the scope of the present invention should not be interpreted as being limited to the embodiment described below. The embodiment of the present invention is provided to more completely describe the present invention to those with average knowledge in the art.

Example 1: Manufacturing of Sub-Pad

1) Configuration of Electrospinning Device

An electrospinning device as shown in FIG. 4 was configured. That is, the conductive nozzle and the drum-type collector were positioned in the state of being spaced apart by 100 to 150 mm, and on the outer circumferential surface of the drum-type collector, a non-conductive electrospinning-induced film made of polyethylene terephthalate (PET) or polycarbonate (PC) material, on which a plurality of circular silver (Ag) paste electrodes were formed on the surface to be spaced apart from each other through a screen printing process, was wound so that the electrodes were exposed to the surface. At this time, the circular silver (Ag) paste electrodes were screen-printed in a state of being connected to other adjacent circular silver (Ag) paste electrodes by a silver (Ag) paste pattern. In addition, the circular silver (Ag) paste electrodes were formed according to the outer circumferential size of the sub-pad (or polishing pad).

Next, an electrospinning device was configured so that a high-voltage power source was applied to the conductive nozzle and the silver (Ag) paste electrodes to form an electrical ground.

2) Preparation of Electrospinning Solution

12.5 g of polystyrene with a weight average molecular weight of 170, 000 was dissolved in 50 ml of DMF solvent to prepare an electrospinning solution. In addition, 0.2 g of nitric acid was added to impart an appropriate electrical conductivity for electrospinning.

3) Electrospinning, Stacking, and Thermal Compression

While supplying the electrospinning solution prepared above to the nozzle of the electrospinning device at a flow rate of 0.8 ml/h, a high voltage of 10 kV was applied to the conductive nozzle, and electrospinning was performed with the drum-type collector electrically grounded to manufacture a nanofiber nonwoven fabric with a thickness of 0.05 mm. At this time, electrospinning was performed while rotating the drum-type collector, and the nanofiber nonwoven fabric was stacked on the electrospinning-induced film as shown in FIG. 5(a). After the electrospinning was completed, the induction film was detached from the drum-type collector to peel off the stacked nanofiber nonwoven fabric (see FIG. 5(b)). After that, the sub-pad was folded along the fold lines as shown in FIG. 5(b) to be overlapped.

The overlapping sub-pads were thermally compressed at 100 to 300° C. as shown in FIG. 6 to complete a sub-pad with a thickness of 1 mm.

Example 2: Manufacture of Sub-Pad

A sub-pad was manufactured in the same manner as in Example 1, except that the electrospinning solution was prepared and used in Example 1 as follows.

1) Preparation of Electrospinning Solution

26 g of 60% Teflon (PTFE, Polytetrafluoroethylene) emulsion and 11 g of PVA (Polyvinyl Alcohol) with a weight average molecular weight of 180,000 were dissolved in 63 ml of water to prepare an electrospinning solution.

Test Example 1: Analysis of Morphology and Physical Properties of Sub-Pad

1) Morphological Analysis

According to the SEM image shown as an example in FIG. 7(b), it can be known that the nanofiber electrospun in the portion in which the electrodes are located has a significantly higher density than the nanofiber in the portion in which the electrodes are not located, resulting in a lower porosity.

In addition, as shown in FIG. 7(c), the density of the nanofiber sheet may be adjusted in the thermal compression process (0.112 mg/mm³, 0.128 mg/mm³, and 0.144 mg/mm³) to adjust the porosity, thereby controlling the density and porosity of the nanofibers.

Therefore, according to these morphological characteristics, the sub-pad of the present invention has a significantly high nanofiber density at the circumferential part (see FIG. 2), which results in a significantly low porosity at the circumferential part, and as schematically shown in FIG. 1, it can be seen that the penetration of the slurry (containing nano abrasive particles of <100 nm) during polishing can be effectively prevented.

2) Physical Property Analysis

(1) Contact Angle Measurement

The contact angle of the sub-pad manufactured in Example 1 above was measured as shown in FIG. 7(a). As a result of the measurement, it was confirmed that the sub-pad of the present invention has a high contact angle of 140 degrees or more due to the use of a superhydrophobic material.

(2) Mechanical indentation

The relationship between the compressive force and the indentation depth was measured by applying pressure to the sub-pad manufactured in Example 1 above using a ball tip with a diameter of 1 mm. The experiment was conducted by dividing into an indentation in ordinary air (dry) and an indentation in water (wet), and the results are shown in FIG. 8.

According to FIG. 8 above, it can be confirmed that the higher the density of the sub-pad of the present invention, the stronger the compressive strength, and that the sub-pad also shows similar compressive characteristics even when submerged in water.

EXPLANATION OF SYMBOLS

• • 20: Top pad
  • 30: Release film
  • 40, 50: Adhesive layer
  • 100: Sub-pad
  • 200: Polishing pad