阅读说明：本技术 交联度可被调节的抛光垫及其制备方法 (Polishing pad with adjustable degree of crosslinking and preparation method thereof ) 是由 尹钟旭 郑恩先 徐章源 于 2020-10-29 设计创作，主要内容包括：本发明提供了一种交联度可被调节的抛光垫及其制备方法。根据一个实施方案的抛光垫包含多官能团的低分子量化合物作为构成抛光层的聚氨酯类树脂的聚合单元之一,从而在生产过程中减少了未反应的二异氰酸酯单体,从而提高了可加工性和质量,并增加交联度。因此,可以将抛光垫应用于包含CMP工艺的半导体器件的制备工艺中,以提供具有优良品质的半导体器件,例如晶圆。(The invention provides a polishing pad with an adjustable crosslinking degree and a preparation method thereof. The polishing pad according to one embodiment includes a multifunctional low molecular weight compound as one of the polymerized units of the polyurethane-based resin constituting the polishing layer, thereby reducing an unreacted diisocyanate monomer during the production process, thereby improving workability and quality, and increasing the degree of crosslinking. Accordingly, the polishing pad can be applied to a process for manufacturing a semiconductor device including a CMP process to provide a semiconductor device, such as a wafer, having excellent quality.)

1. A polishing pad comprising a polishing layer comprising a polyurethane-based resin, wherein the polyurethane-based resin comprises diisocyanate, polyol and a multifunctional low molecular weight compound as polymerized units, the multifunctional low molecular weight compound has a molecular weight of 500 or less, and the polishing layer has a swelling ratio in dimethyl sulfoxide of 100% to 250% based on the volume or weight of the polishing layer.

2. The polishing pad according to claim 1, wherein the polyurethane-based resin comprises a polyfunctional low-molecular weight compound reactive with diisocyanate; and a polymer chain formed by crosslinking the multifunctional low molecular weight compound.

3. The polishing pad according to claim 1, wherein the multifunctional low molecular weight compound contains 3 to 10 functional groups at an end, and the functional group is at least one selected from the group consisting of a hydroxyl group, an amine group, and an epoxy group.

4. The polishing pad according to claim 1, wherein the multifunctional low molecular weight compound comprises at least one selected from the group consisting of glycerin, trimethylolpropane, ethylenediamine, diethanolamine, diethylenetriamine, triethylenetetramine, and water.

5. The polishing pad according to claim 1, wherein the polyurethane-based resin is obtained by curing a urethane-based prepolymer;

the urethane prepolymer contains diisocyanate, polyol and a polyfunctional low-molecular-weight compound as polymerization units;

and the urethane prepolymer contains 0.1 to 5 percent of polyfunctional low molecular weight compound based on the weight of the urethane prepolymer.

6. The polishing pad of claim 5, wherein the urethane based prepolymer comprises 0.1% to 5% unreacted diisocyanate based on the total weight of the diisocyanate.

7. The polishing pad of claim 1, wherein the polishing layer has a swelling ratio in dimethylsulfoxide of 100% to 200% based on the volume of the polishing layer; the polishing layer has a swelling ratio in dimethyl sulfoxide of 150% to 250% based on the weight of the polishing layer.

8. A method of preparing a polishing pad, comprising:

reacting a diisocyanate, a polyol and a polyfunctional low molecular weight compound to prepare a urethane prepolymer, and

mixing the urethane-based prepolymer with a curing agent and a foaming agent, and curing the mixture to prepare a polishing layer,

wherein the multifunctional low molecular weight compound has a molecular weight of 500 or less, and

the polishing layer has a swelling ratio in dimethylsulfoxide of 100% to 250% based on the volume or weight of the polishing layer.

9. The method of preparing a polishing pad according to claim 8, wherein the urethane prepolymer is prepared by a first reaction step of reacting a diisocyanate with a polyol; and a second reaction step of reacting the product of the first reaction with a multifunctional low-molecular-weight compound; wherein the content of unreacted diisocyanate in the product of the second reaction is less than the content of unreacted diisocyanate in the product of the first reaction.

10. A method of making a semiconductor device, comprising:

polishing the surface of the semiconductor substrate using a polishing pad,

wherein the polishing pad comprises a polishing layer comprising a polyurethane-based resin,

the polyurethane resin comprises diisocyanate, polyalcohol and polyfunctional low molecular weight compound as a polymerization unit,

the multifunctional low-molecular weight compound has a molecular weight of 500 or less, and,

the polishing layer has a swelling ratio in dimethylsulfoxide of 100% to 250% based on the volume or weight of the polishing layer.

Technical Field

Embodiments relate to a polishing pad in which a degree of cross-linking can be adjusted and a method of preparing the same. More particularly, embodiments relate to a polishing pad having a degree of crosslinking adjusted to have characteristics and properties suitable for a Chemical Mechanical Planarization (CMP) process, a method of preparing the same, and a method of preparing a semiconductor device by using the polishing pad.

Background

A Chemical Mechanical Planarization (CMP) process among processes for manufacturing a semiconductor refers to a step of fixing a semiconductor substrate such as a wafer on a magnetic head and contacting a surface of a polishing pad mounted on a platen, and then chemically treating the wafer by supplying slurry while the platen and the magnetic head are relatively moved, thereby mechanically planarizing irregularities on the semiconductor substrate.

The polishing pad is an essential component that plays an important role in such a CMP process. Generally, a polishing pad is composed of a polyurethane-based resin prepared from a composition comprising a prepolymer obtained by reacting a diisocyanate and a polyol, a curing agent, a foaming agent, and the like (see korean laid-open patent publication No. 2016-.

In addition, the polishing pad is provided on the surface thereof with grooves for flowing a large amount of slurry and pores for supporting a fine flow thereof. These pores may be formed by using a solid-phase foaming agent having voids, an inert gas, a liquid-phase material, fibers, or the like, or by generating a gas through a chemical reaction.

Disclosure of Invention

Technical problem

It is well known that the performance of a polishing pad used in a CMP process is affected by the composition of a urethane resin constituting the polishing pad, the diameter of micropores, and physical properties of the polishing pad, such as hardness, tensile strength, and elongation. In particular, among various chemical structures formed by the preparation and curing reaction of urethane prepolymers, the bonding units formed by crosslinking have a great influence on the physical properties of the polishing pad. In addition, the unreacted monomers remaining in the urethane based prepolymer also have different effects on the characteristics and physical properties of the polishing pad. This has a large impact on the performance of the CMP process.

In particular, the unreacted diisocyanate monomer present in the urethane-based prepolymer unnecessarily shortens the gel time in the curing step for producing the polishing pad, thereby making process control difficult and ultimately leading to deterioration in the quality of the polishing pad. However, if the content of diisocyanate in the raw materials is reduced to reduce the unreacted diisocyanate monomer, mechanical properties such as hardness and tensile strength of the final polishing pad may also be deteriorated accordingly, thereby deteriorating the performance of the polishing pad.

As a result of the studies of the present inventors, it has been found that a certain amount of a multifunctional low molecular weight compound contained in the raw material during the production of a polishing pad can increase the degree of crosslinking and, at the same time, can reduce the content of unreacted diisocyanate monomer in the urethane prepolymer, thereby improving the mechanical properties.

Accordingly, an object of the present embodiment is to provide a polishing pad, a cross-linking degree of which is adjusted to have characteristics and properties suitable for a CMP process, a method for preparing the same, and a method for preparing a semiconductor device using the polishing pad.

Solution to the technical problem

According to one embodiment, there is provided a polishing pad comprising a polishing layer comprising a polyurethane-based resin, wherein the polyurethane-based resin comprises diisocyanate, polyol and a multifunctional low molecular weight compound as polymerized units, the multifunctional low molecular weight compound has a molecular weight of 500 or less, and the polishing layer has a swelling rate of 100% to 250% in dimethylsulfoxide, based on the volume or weight of the polishing layer.

According to another embodiment, there is provided a method of preparing a polishing pad, the method including reacting a diisocyanate, a polyol, and a multifunctional low molecular weight compound to prepare a urethane-based prepolymer; and mixing the urethane prepolymer with a curing agent and a foaming agent, and curing the mixture to prepare a polishing layer, wherein the multifunctional low molecular weight compound has a molecular weight of 500 or less, and the polishing layer has a swelling rate of 100% to 250% in dimethyl sulfoxide based on the volume or weight of the polishing layer.

According to still another embodiment, there is provided a method for manufacturing a semiconductor device, the method including polishing a surface of a semiconductor substrate using a polishing pad, wherein the polishing pad includes a polishing layer including a polyurethane-based resin including a diisocyanate, a polyol, and a multifunctional low molecular weight compound as polymerized units, the functional multifunctional low molecular weight compound having a molecular weight of 500 or less, and the polishing layer has a swelling ratio in dimethyl sulfoxide of 100% to 250% based on the volume or weight of the polishing layer.

Advantageous effects of the invention

The polishing pad according to one embodiment includes a multifunctional low molecular weight compound as a polymerized unit of a polyurethane-based resin constituting a polishing layer, thereby reducing an unreacted diisocyanate monomer during production, improving processability and quality, and increasing a crosslinking degree. Therefore, the polishing pad can be applied to a manufacturing process of a semiconductor device including a CMP process to provide a semiconductor device such as a wafer with excellent quality.

Drawings

FIG. 1 schematically shows that in a reaction of urethane based prepolymer to prepare a polishing pad, a multifunctional low molecular weight compound is combined with an unreacted diisocyanate monomer while a polymeric chain is attached, according to one embodiment.

Detailed Description

Best mode for carrying out the invention

In the description of the entire embodiments, in the case where it is mentioned that one element is formed over or under another element, it means not only that the element is directly formed over or under another element but also that the element is indirectly formed over or under another element with the other element interposed therebetween.

In this specification, when a component is referred to as "comprising" an element, it is understood that it may also comprise other elements, but not exclude other elements, unless specifically stated otherwise.

Moreover, unless otherwise indicated, all numerical ranges relating to physical properties, dimensions, etc. of components used herein are to be understood as modified by the term "about".

In this specification, the singular forms should be interpreted in the context of the singular or plural forms unless the context clearly dictates otherwise.

In the present specification, "polymerized unit" refers to a monomer, oligomer or additive used in the process of preparing a corresponding polymer or prepolymer. It refers to a compound that participates in or is derived from a unit that actually constitutes the polymer chain.

Polishing pad

The polishing pad according to one embodiment includes a polishing layer including a polyurethane-based resin, wherein the polyurethane-based resin includes diisocyanate, polyol and a multifunctional low molecular weight compound as polymerized units, the multifunctional low molecular weight compound has a molecular weight of 500 or less, and the polishing layer has a swelling rate of 100% to 250% in dimethyl sulfoxide based on the volume or weight of the polishing layer.

Multifunctional low molecular weight compound

The polishing pad according to one embodiment includes a multifunctional low molecular weight compound as one of the polymerized units of the polyurethane-based resin constituting the polishing layer, thereby reducing unreacted diisocyanate monomer during the production process to improve processability and quality, and increasing the degree of crosslinking.

FIG. 1 schematically shows that in a reaction of urethane based prepolymer to prepare a polishing pad, a multifunctional low molecular weight compound is combined with an unreacted diisocyanate monomer while a polymeric chain is attached, according to one embodiment.

Referring to fig. 1, (a) first, a diisocyanate, a polyol and a multifunctional low molecular weight compound are mixed as polymerization units, (b) wherein the diisocyanate and the polyol form a prepolymer chain, and (c) the multifunctional low molecular weight compound can react with the unreacted diisocyanate while being connected to the prepolymer chain.

Thus, the polyurethane-based resin may include a multifunctional low molecular weight compound reacted with diisocyanate; and a polymer chain formed by crosslinking a multifunctional low molecular weight compound.

The reaction and crosslinking reaction of diisocyanates and polyfunctional low molecular weight compounds comprises a urethane reaction in which NCO groups and OH groups react to form urethane groups (-NH — C (═ O) -O-). In addition, the crosslinking reaction may further include a crosslinking reaction that forms allophanate groups or biuret groups.

The multifunctional low molecular weight compound may include one or more compounds having two or more functional groups at the end and a molecular weight of 500 or less. For example, the multifunctional low molecular weight compound may include 3 or more, 3 to 10, 3 to 7, or 3 to 5 functional groups at the end.

Specifically, the multifunctional low molecular weight compound comprises 3-10 functional groups at the terminal, and the functional groups can be at least one selected from the group consisting of hydroxyl groups, amine groups and epoxy groups.

The multifunctional low-molecular-weight compound may have a molecular weight of 500 or less, 400 or less, 300 or less, 200 or less, 150 or less, or 100 or less. Specifically, the molecular weight of the multifunctional low molecular weight compound can be 15-500, 30-500, 50-400, 50-300 or 50-200.

Specifically, the multifunctional low molecular weight compound may include at least one selected from the group consisting of glycerin, trimethylolpropane, ethylenediamine, diethanolamine, diethylenetriamine, triethylenetetramine, and water.

The urethane prepolymer may contain 0.1 to 10% of a multifunctional low molecular weight compound, particularly 0.1 to 5% (by weight), based on the weight of the urethane prepolymer. More specifically, the multifunctional low molecular weight compound may be 0.1 to 3 wt%, 0.1 to 2 wt%, 2 to 5 wt%, or 3 to 5 wt%, based on the weight of the urethane prepolymer.

Polyurethane resin

The polyurethane-based resin constituting the polishing layer contains diisocyanate, polyol and a multifunctional low-molecular-weight compound.

The diisocyanate can be at least one aromatic diisocyanate and/or at least one aliphatic diisocyanate. For example, it may be selected from at least one of the group consisting of Toluene Diisocyanate (TDI), 1, 5-naphthalene diisocyanate (naphthalene-1,5-diisocyanate), p-phenylene diisocyanate, dimethylbiphenyl diisocyanate (tolidine diisocyanate), diphenylmethane diisocyanate (MDI), Hexamethylene Diisocyanate (HDI), dicyclohexylmethane diisocyanate (H12MDI), and isophorone diisocyanate.

As a specific example, the diisocyanate comprises at least one aromatic diisocyanate comprising toluene 2, 4-diisocyanate and toluene 2, 6-diisocyanate.

As another specific example, the at least one diisocyanate may further comprise at least one aliphatic diisocyanate, and the at least one aliphatic diisocyanate may be diphenylmethane diisocyanate (MDI), Hexamethylene Diisocyanate (HDI), dicyclohexylmethane diisocyanate (H12MDI), or the like.

The polyol is a conventional polyol which is widely accepted in the field of polyurethane preparation. The polyol may contain one, two or more hydroxyl groups, which may include oligomers to high molecular weight polyols having a certain or higher weight average molecular weight. For example, the polyol may comprise a polyether polyol, a polyester polyol, a polycarbonate polyol, or a polycaprolactone polyol, and the like. Specifically, the polyether polyol is a compound containing two or more repeating units of alkylene ether (or alkylene glycol). Depending on the number of repeating alkylene ether units, it can reach various sizes of oligomers to polymers. Further, the polyol may refer to a composition in which compounds of various sizes are mixed.

In addition, the polyurethane-based resin may include one or more diols as a polymerization unit. Specific examples of the diol may include Ethylene Glycol (EG), diethylene glycol (DEG), 1, 2-Propanediol (PG), 1, 3-Propanediol (PDO), methyl propanediol (MP-diol), and the like.

The weight average molecular weight (Mw) of the polyurethane resin can be 500-1,000,000, 5,000-1,000,000, 50,000-1,000,000, 100,000-700,000 or 500-3,000.

The polyurethane resin may be derived from a urethane prepolymer. For example, the polyurethane-based resin may be obtained by curing a urethane-based prepolymer, which may contain, as polymerized units, a diisocyanate, a polyol and a multifunctional low-molecular weight compound.

Specifically, the urethane based prepolymer may comprise a prepolymerization product of a diisocyanate monomer, a polyol and a multifunctional low molecular weight compound.

The prepolymerization generally refers to a reaction for preparing a polymer having a relatively low molecular weight, in which the degree of polymerization is adjusted to an intermediate level in order to conveniently shape a product in the production process. Thus, the prepolymer comprising the prepolymerized reaction product may be shaped by itself or after further reaction with another polymerizable compound or curing agent to form the final product. For example, the urethane prepolymer may have a weight average molecular weight (Mw) of 500 to 5,000, 500 to 3,000, 600 to 2,000, or 700 to 1,500.

The urethane prepolymer contains polymerization reactants with various molecular weights formed by diisocyanate and polyalcohol. For example, in a urethane based prepolymer, the diisocyanate may form a chain in the prepolymer by reaction of at least one NCO group.

The reaction of the NCO group includes a reaction with a polyol or a side reaction with another compound, but is not particularly limited. For example, the reaction of the NCO groups may comprise a chain extension reaction. For example, the reaction of the NCO groups includes a urethane reaction in which an NCO group and an OH group are reacted during the reaction of a diisocyanate and a polyol to form a urethane group (-NH — C (═ O) -O-), to prepare a urethane prepolymer.

In addition, some of the monomers used in the reaction to prepare the urethane prepolymer may not participate in the reaction. Therefore, monomers not participating in the reaction may be present in the urethane based prepolymer. Specifically, the urethane based prepolymer may contain unreacted diisocyanate. In the present specification, "unreacted diisocyanate" refers to a diisocyanate in which all NCO groups are unreacted.

The unreacted diisocyanate present in the urethane-based prepolymer unnecessarily shortens the gel time in the curing step for producing the polishing pad, thereby making process control difficult and deteriorating the quality of the final polishing pad. According to this embodiment, the content of unreacted diisocyanate in the urethane prepolymer can be reduced by adding a multifunctional low-molecular weight compound. Thus, the urethane based prepolymer may contain a small amount of unreacted diisocyanate.

Thus, the urethane based prepolymer may comprise 10% or less (by weight), 7% or less (by weight), 5% or less (by weight), 0 to 7% or less (by weight), 1 to 7% or less (by weight), 0 to 5% or less (by weight), 0.1 to 5% or 1 to 5% or less (by weight) of unreacted diisocyanate based on the total weight of the diisocyanate. Specifically, the urethane based prepolymer may include 0.1 to 5 wt% of unreacted diisocyanate, based on the total weight of the diisocyanate. In this case, the unreacted diisocyanate may be an unreacted aromatic diisocyanate.

The urethane based prepolymer may have an unreacted NCO group at the terminal of the polymer, oligomer or monomer contained therein. As a specific example, the urethane based prepolymer may include 5% to 13% (by weight), 5% to 10% (by weight), 5% to 9% (by weight), 6% to 8% (by weight), 7% to 9% (by weight), or 7% to 8% (by weight) of unreacted NCO groups, based on the weight of the urethane based prepolymer. As a specific example, the urethane based prepolymer may contain 5% to 10% (wt%) of unreacted NCO groups, based on the weight of the urethane based prepolymer.

Polishing layer

The polishing layer comprises a polyurethane-based resin, more specifically, a porous polyurethane-based resin.

That is, the polishing layer may include a polyurethane-based resin and a plurality of micropores distributed in the polyurethane-based resin.

The thickness of the polishing layer can be 0.8 mm-5.0 mm, 1.0 mm-4.0 mm, 1.0 mm-3.0 mm, 1.5 mm-2.5 mm, 1.7 mm-2.3 mm or 2.0 mm-2.1 mm.

The polishing layer may have a specific gravity of 0.6g/cm³～0.9g/cm³Or 0.7g/cm³～0.85g/cm³。

The polishing layer may have a hardness of 30 Shore D (Shore D) to 80 Shore D (Shore D), 40 Shore D (Shore D) to 70 Shore D (Shore D), 50 Shore D (Shore D) to 70 Shore D (Shore D), 40 Shore D (Shore D) to 65 Shore D (Shore D), or 55 Shore D (Shore D) to 65 Shore D (Shore D).

The polishing layer may have a tensile strength of 5N/mm²～30N/mm²、10N/mm²～25N/mm²、10N/mm²～20N/mm²Or 15N/mm²～30N/mm²。

The polishing layer may have an elongation of 50% to 300%, for example 50% to 150%, 100% to 300%, 150% to 250%, or 120% to 230%.

As a specific example, the polishing layer may have a hardness of 55 Shore D (Shore D) to 65 Shore D (Shore D, tensile strength may be 10N/mm)²～25N/mm²The elongation can be 50% to 150%.

SaidThe polishing rate (or removal rate) of the polishing layer can be OrThe polishing rate may be an initial polishing rate that is performed immediately after the polishing layer is prepared (i.e., immediately after it is cured).

In addition, the polishing layer may have a pad cut rate of 30 μm/hr to 60 μm/hr, 30 μm/hr to 50 μm/hr, 40 μm/hr to 60 μm/hr, or 40 μm/hr to 50 μm/hr.

The micropores are present in a form dispersed in the polyurethane resin.

The average diameter of the micropores can be 10-50 μm, 20-40 μm, 20-30 μm, 20-25 μm or 30-50 μm.

Further, the total area of the micropores may be 30% to 60%, 35% to 50%, or 35% to 43%, based on the total area of the polishing layer. In addition, the total volume of the micropores may be 30 to 70% or 40 to 60%, based on the total volume of the polishing layer.

The polishing layer can have grooves on its surface for mechanical polishing. The grooves may have a depth, width and pitch required for mechanical polishing, which are not particularly limited.

Swelling ratio

By adjusting the swelling ratio of the polishing layer in dimethyl sulfoxide (DMSO), the degree of crosslinking of the polyurethane-based resin can be more effectively achieved, which is closely related to the characteristic of the polishing pad affecting its CMP performance.

The polishing layer may have a swelling ratio in dimethylsulfoxide of 100% to 250%, 100% to 200%, 100% to 150%, 150% to 250%, or 200% to 250%, based on the volume or weight of the polishing layer.

For example, the polishing layer can have a swelling ratio in dimethylsulfoxide of 100% to 200%, 100% to 150%, or 150% to 200%, based on the volume of the polishing layer. Further, the polishing layer can have a swelling ratio in dimethyl sulfoxide of 150% to 250%, 150% to 200%, or 200% to 250%, based on the weight of the polishing layer.

Specifically, in dimethyl sulfoxide, the polishing layer can have a swelling ratio of 100% to 200% based on the volume of the polishing layer and a swelling ratio of 150% to 250% based on the weight of the polishing layer.

Supporting layer

In addition, the polishing pad can further comprise a support layer disposed on one side of the polishing layer. The support layer functions to support the polishing layer and to absorb and distribute impact applied to the polishing layer.

The support layer may comprise non-woven fabric or suede. The thickness of the alloy can be 0.5 mm-1 mm, and the hardness can be 60 Shore (Asker C) to 90 Shore (Asker C).

Adhesive layer

The polishing pad may further comprise an adhesive layer interposed between the polishing layer and the support layer.

The adhesive layer may comprise a hot melt adhesive. The hot melt adhesive may be at least one selected from the group consisting of polyurethane resins, polyester resins, ethylene-vinyl acetate resins, polyamide resins, and polyolefin resins. Specifically, the hot melt adhesive may be at least one selected from polyurethane resins and polyester resins.

Method for preparing polishing pad

A method of manufacturing a polishing pad according to one embodiment includes reacting a diisocyanate, a polyol, and a multifunctional low molecular weight compound to prepare a urethane prepolymer, and mixing the urethane prepolymer with a curing agent and a foaming agent, and curing the mixture to prepare a polishing layer, wherein the multifunctional low molecular weight compound has a molecular weight of 500 or less, and the polishing layer has a swelling ratio of 100% to 250% in dimethyl sulfoxide based on the volume or weight of the polishing layer.

Preparation of urethane prepolymer

First, diisocyanate, polyol and a polyfunctional low-molecular-weight compound are reacted to prepare a urethane prepolymer.

The urethane based prepolymer can be prepared by reacting at least one diisocyanate monomer as described above, at least one polyol as described above and at least one multifunctional low molecular weight compound as described above, wherein the polymerization is terminated in an intermediate stage to have a relatively low molecular weight.

The step of preparing the urethane based prepolymer may include a first reaction step of reacting a diisocyanate and a polyol; and a second reaction step of reacting the product of the first reaction with a multifunctional low-molecular-weight compound.

In this case, the content of the unreacted diisocyanate in the product of the second reaction may be less than the content of the unreacted diisocyanate in the product of the first reaction.

In addition, the content of each compound and the reaction conditions employed in the preparation of the urethane-based prepolymer may be adjusted to control the content of unreacted diisocyanate in the prepolymer and the degree of crosslinking of the final polyurethane-based resin.

The urethane prepolymer may include 0.1 to 10% of a multifunctional low molecular weight compound based on the weight of the urethane prepolymer.

In addition, the urethane based prepolymer may include 0.1% to 10% of an unreacted diisocyanate based on the total weight of the diisocyanate.

In addition, additional isocyanate, alcohol or other additives may be further added during the preparation of the prepolymer.

Preparation of polishing layer

Thereafter, the urethane prepolymer is mixed with a curing agent and a foaming agent, and the mixture is cured to prepare a polishing layer.

The mixing can be carried out at a temperature of 50 ℃ to 150 ℃. If necessary, the reaction may be carried out under vacuum defoaming conditions.

In addition, the curing may be at 60 ℃ to 120 ℃ and 50kg/m²～200kg/m²Under the pressure conditions of (1).

The curing agent can be at least one of amine compounds and alcohol compounds. Specifically, the curing agent may include at least one selected from the group consisting of aromatic amines, aliphatic amines, aromatic alcohols, and aliphatic alcohols. The curing agent may have, for example, two or more reactive groups. Further, the curing agent has a molecular weight of, for example, greater than 50, greater than 100, greater than 150, greater than 200, greater than 300, or greater than 500. Specifically, the curing agent may be selected from at least one of the group consisting of 4,4' -methylenebis (2-chloroaniline) (MOCA), diethyltoluenediamine (DETDA), diaminodiphenylmethane, diaminodiphenylsulfone, 1, 3-xylylenediamine, isophoronediamine, polypropylene diamine, and polypropylene triamine.

The urethane based prepolymer and the curing agent may be mixed in a ratio of 1: 0.8-1: 1.2 or 1: 0.9-1: 1.1 molar equivalent ratio. Here, "the number of moles of the reactive group per molecule" means, for example, the number of moles of NCO groups in the urethane-based prepolymer and the number of moles of the reactive group (e.g., amine group, alcohol group, etc.) in the curing agent. Therefore, the urethane based prepolymer and the curing agent can be fed at a constant rate during the mixing by controlling the feed rate so that the feed amounts of the urethane based prepolymer and the curing agent per unit time satisfy the molar equivalent ratio as described above.

The foaming agent is not particularly limited as long as it is generally used to form voids in the polishing pad.

For example, the blowing agent may be at least one selected from a solid-phase blowing agent having a hollow structure, a liquid-phase blowing agent using a volatile liquid, and an inert gas.

The solid-phase foaming agent can be a thermal expansion microcapsule. They can be obtained by thermally expanding thermally expandable microcapsules. Since the thermally expandable microcapsules in the thermally expandable microsphere structure have a uniform particle diameter, they have an advantage in that the pore size can be uniformly controlled. Specifically, the solid-phase foaming agent can be a microsphere structure with the average particle diameter of 5-200 mu m.

The thermally expandable microcapsule may include an outer shell including a thermoplastic resin; and a blowing agent encapsulated within said shell. The thermoplastic resin may be at least one selected from the group consisting of a vinylidene chloride copolymer, an acrylonitrile-based copolymer, a methacrylonitrile-based copolymer, and an acrylic-based copolymer. In addition, the foaming agent can be at least one selected from hydrocarbons with 1-7 carbon atoms.

The solid phase blowing agent may be used in an amount of 0.1 to 2.0 parts by weight, based on 100 parts by weight of the urethane prepolymer. Specifically, the solid phase blowing agent may be used in an amount of 0.3 to 1.5 parts by weight or 0.5 to 1.0 parts by weight, based on 100 parts by weight of the urethane based prepolymer.

The kind of the inert gas is not particularly limited as long as it does not participate in the reaction between the urethane based prepolymer and the curing agent. For example, the inert gas may be selected from nitrogen (N)₂) Carbon dioxide (CO)₂) At least one of the group consisting of argon (Ar) and helium (He). Specifically, the inert gas may be nitrogen (N)₂) Or carbon dioxide (CO)₂)。

The inert gas may be fed in a volume of 10% to 30% based on the total volume of the polyurethane-based resin composition. Specifically, the inert gas may be fed in a volume of 15% to 30% based on the total volume of the polyurethane-based resin composition.

Thereafter, the method may further comprise the steps of cutting the surface of the polishing layer obtained as described above, forming grooves on the surface thereof, bonding to a lower portion, inspecting, packaging, and the like.

These steps may be performed in a conventional manner for preparing polishing pads.

Method for manufacturing semiconductor device

According to one embodiment, a method of manufacturing a semiconductor device includes polishing a surface of a semiconductor substrate using the polishing pad according to the embodiment.

That is, according to one embodiment, a method for manufacturing a semiconductor device includes polishing a surface of a semiconductor substrate using a polishing pad, wherein the polishing pad includes a polishing layer including a polyurethane-based resin including diisocyanate, polyol, and a multifunctional low molecular weight compound as a polymerization unit, the multifunctional low molecular weight compound having a molecular weight of 500 or less, and the polishing layer has a swelling ratio in dimethyl sulfoxide of 100% to 250% based on the volume or weight of the polishing layer.

Specifically, when the polishing pad according to one embodiment is mounted on a platen, a semiconductor substrate is placed over the polishing pad. In this case, the surface of the semiconductor substrate is in direct contact with the polishing surface of the polishing pad. The polishing slurry may be sprayed on the polishing pad for polishing. Thereafter, the semiconductor substrate and the polishing pad are rotated relative to each other, so that the surface of the semiconductor substrate is polished.

Detailed Description

Hereinafter, the present invention is explained in detail by the following examples. However, the scope of the present invention is not limited thereto.

Examples and comparative examples

Step (1) preparation of prepolymer

Toluene Diisocyanate (TDI), dicyclohexylmethane diisocyanate (H12MDI), polytetramethylene ether glycol (PTMEG) and diethylene glycol (DEG) were charged in a four-necked flask, and then reacted at 80 ℃ for 3 hours. Thereafter, a multifunctional low molecular weight compound was added in an amount shown in the following Table 1, and then reacted at 80 ℃ for 2 hours to prepare a urethane based prepolymer. The NCO% and unreacted TDI content of the prepolymer are shown in Table 1 below.

Step (2) preparation of polishing pad

A casting machine equipped with a storage tank and a feed line for a prepolymer, a curing agent, an inert gas and a blowing agent is provided. Mixing the prepared urethane prepolymer, a curing agent (bis (4-amino-3-chlorophenyl) methane, Ishihara) and an inert gas (N)₂) Liquid phase blowing agents (FC3283, 3M), solid phase blowing agents (Akzonobel) and silicone surfactants (siloxy surface)surfactant-Evonik) was added separately to each reservoir. While the raw materials are being stirred, they are fed at a constant speed to the mixing head through the respective feed lines. In this case, the prepolymer and curing agent were fed in an equivalent ratio of 1:1 and at a total rate of 10 kg/min.

A mold (1,000 mm. times.1, 000 mm. times.3 mm) was prepared and preheated at a temperature of 80 ℃. And injecting the prepared mixed raw materials into a mold, and reacting to obtain a solid-phase cake-shaped molded product. Thereafter, the top and bottom of the molded product were separately ground to obtain polishing layers.

Specific process conditions and prepolymer compositions are shown in the following table.

TABLE 1

Test example

The following items of the urethane prepolymers or polishing pads obtained in the examples and comparative examples were tested.

(1) Content of unreacted TDI

The composition of the prepolymer was analyzed to determine the content of unreacted TDI. A5 mg sample of the carbamate prepolymer was first dissolved in CDCl₃And at room temperature using a Nuclear Magnetic Resonance (NMR) apparatus (JEOL 500MHz,90 ℃ pulse)¹H-NMR and¹³C-NMR analysis. The peaks of the reacted or unreacted TDI methyl groups in the NMR data thus obtained were integrated to calculate the content of the reacted or unreacted TDI monomer in the urethane based prepolymer.

Specifically, when the weight of 2,4-TDI (hereinafter referred to as "4-reacted 2,4-TDI") in which only NCO group located at the 4-position among two NCO groups was reacted with a polyol was 100 parts by weight, the corresponding weight of 2,4-TDI (hereinafter referred to as "2, 4-reacted 2,4-TDI") in which both NCO groups were reacted with a polyol to form a chain was calculated; the weight of 2,6-TDI (hereinafter referred to as "unreacted 2,6-TDI") having no NCO group reacted with the polyol was calculated, and the weight of 2,6-TDI (hereinafter referred to as "2-reacted 2,6-TDI") having only NCO at the 2-position or 6-position of the two NCO groups reacted with the polyol was calculated. (in addition, it was hardly detected that 2,4-TDI which had reacted only at the 2-position NCO and 2,6-TDI which had reacted both NCO groups.) the results are shown in the following Table.

TABLE 2

(2) Swelling ratio

The polishing layer before the grooves were formed was cut into a sample having a diameter of 20 mm and a thickness of 2 mm. The exact dimensions of the sample thus prepared were measured with a vernier caliper. The sample was weighed using a four digit scale to decimal point. A250 mL beaker was filled with 50mL of solvent (DMSO), and the sample was placed therein and stored at room temperature (20-25 ℃) for 24 hours. Thereafter, the sample is taken out, and the solvent remaining on the surface of the sample is wiped with gauze 2 to 3 times. Then, the size and weight of the sample were measured.

The swelling ratio (%) was calculated by the following formula.

The swelling ratio (%, volume) — (initial volume × volume after storage in a solvent)/initial volume × 100.

The swelling ratio (%, by weight) — (initial weight × weight after storage in a solvent)/initial weight × 100.

(3) Hardness of

Each sample was cut into 5cm × 5cm (thickness: 2mm), stored at room temperature and at a temperature of 30 deg.C, 50 deg.C, 70 deg.C for 12 hours, and measured for Shore hardness (Shore D) and Asker C hardness with a durometer.

(4) Specific gravity of

Each sample was cut into 2cm by 5cm (thickness: 2mm), stored at 25 ℃ for 12 hours, and measured for specific gravity with a densitometer.

(5) Tensile strength

Each sample was cut into 4cm by 1cm (thickness: 2 mm). The ultimate strength before fracture was measured when the sample was tested at a rate of 50mm/min using a Universal Testing Machine (UTM).

(6) Elongation percentage

Each sample was cut into 4cm X1 cm (thickness: 2 mm). The maximum deformation before fracture was measured when the sample was tested at a rate of 50mm/min using a Universal Testing Machine (UTM). The ratio of the maximum deformation to the initial length is expressed in percent (%).

(7) Modulus of elasticity

Each sample was cut into 4cm by 1cm (thickness: 2 mm). When the sample was tested at a rate of 50mm/min using a Universal Testing Machine (UTM), the modulus was measured as the slope between 70% elongation and 20% elongation.

(8) Polishing rate

Immediately after the completion of the polishing pad preparation, the polishing rate was measured according to the method shown below. Wafers with a diameter of 300mm were deposited with silicon oxide by the CVD method. The polishing pad was mounted on a CMP machine with the silicon oxide layer on the silicon wafer facing the polishing surface of the polishing pad. The silicon oxide layer was polished under a polishing load of 4.0psi while rotating at 150rpm for 60 seconds, and a calcined silicon oxide (silicon dioxide) slurry was supplied to the polishing pad at a rate of 250 mL/min. After completion of polishing, the silicon wafer was separated from the carrier, mounted in a spin dryer, washed with distilled water, and then dried with nitrogen gas for 15 seconds. Changes in film thickness of the silicon wafers dried before and after polishing were measured using a thickness measuring instrument of the spectral reflectometer type (SI-F80R, Keyence). The polishing rate was calculated using the following equation.

(9) Pad cut rate

Each polishing pad was pretreated with deionized water for 10 minutes, and then treated while spraying deionized water for 1 hour. The thickness variation of the polishing pad was measured during the process to calculate the cut rate of the pad. The device used for processing is a CTS AP-300 HM. The treatment pressure is 6lbf, the rotating speed is 100-110 rpm, and the disc for treatment is CI-45 of Sasol.

The results are shown in the following table.

TABLE 3

As shown in the above table, the polishing pads of examples 1 to 3 had a smaller swelling ratio than the polishing pad of comparative example 1, and were excellent in hardness, tensile strength, elongation and polishing rate.