POLISHING PAD AND PREPARATION METHOD OF SEMICONDUCTOR DEVICE USING THE SAME

Abstract

According to embodiments of the present invention, there are provided a polishing pad and a process for preparing a semiconductor device using the polishing pad. The polishing pad comprises a polishing layer comprising a polishing surface and having a plurality of pores formed therein, wherein the contact area ratio of the polishing surface according to Equation 1 is 0.76% or more. Surface defects of a film substance to be polished can be suppressed, and polishing efficiency and uniformity can be improved.

Claims

1. A polishing pad, which comprises a polishing layer comprising a polishing surface and having a plurality of pores formed therein, wherein the contact area ratio (CAR) of the polishing surface according to the following Equation 1 is 0.76% or more: $\begin{array}{cc}\mathrm{CAR}=\frac{{\mathrm{CA}}_{50}}{\mathrm{TA}}100\%& \left[\mathrm{Equation}1\right]\end{array}$ in Equation 1, TA is a unit area, which is 1,000 m.sup.2 or more, and when the polishing surface is measured using an optical surface roughness measuring device based on the unit area, and when an imaginary surface that is parallel to the center plane of the polishing surface and located at a height of 50% of the maximum peak height (Sp) of the polishing surface is defined as a reference surface, CA.sub.50, which is a contact area, is calculated as the total area of the regions where the peaks formed on the polishing surface are in contact with the reference surface.

2. The polishing pad of claim 1, wherein the contact area ratio (CAR) of the polishing surface is 0.76% to 1.5%.

3. The polishing pad of claim 1, wherein when a measurement region of the polishing surface, the measurement region having a size of 1,200 m900 m, is arbitrarily selected and measured with an optical surface roughness measuring device to measure the contact area, the contact area per unit area of the measurement region of the polishing surface is 8,200 m.sup.2/1,080,000 m.sup.2 to 11,000 m.sup.2/1,080,000 m.sup.2.

4. The polishing pad of claim 1, wherein the contact counts ratio (CCR) of the polishing surface according to the following Equation 2 is 280/1,000,000 m.sup.2 or more: $\begin{array}{cc}\mathrm{CCR}=\frac{k{\mathrm{CC}}_{50}}{\mathrm{TA}}\frac{1,000,000}{1,000,000}& \left[\mathrm{Equation}2\right]\end{array}$ in Equation 2, TA is a unit area, which is k m.sup.2, and k is 1,000 or more, and wherein when the polishing surface is measured using an optical surface roughness measuring device based on the unit area, and when an imaginary surface that is parallel to the center plane of the polishing surface and located at a height of 50% of the maximum peak height (Sp) of the polishing surface is defined as a reference surface, CC.sub.50 is calculated as the total number of the regions where the peaks formed on the polishing surface are in contact with the reference surface.

5. The polishing pad of claim 4, wherein the contact counts ratio (CCR) of the polishing surface is 280/1,000,000 m.sup.2 to 1,000/1,000,000 m.sup.2.

6. The polishing pad of claim 1, wherein the pore uniformity represented by the following Equation 3 is 0.6 or less: $\begin{array}{cc}\mathrm{Pore}\mathrm{uniformity}=\frac{D90-D10}{D50}& \left[\mathrm{Equation}3\right]\end{array}$ in Equation 3, D10, D50, and D90 are the diameters of the pores at the cumulative volume fractions of 10%, 50%, and 90%, respectively, in a volume distribution obtained by accumulating the pores in order of diameter from smallest to largest.

7. The polishing pad of claim 1, wherein the ratio of D50 to the average diameter (Dn) of the plurality of pores is 1.4 or less.

8. The polishing pad of claim 1, wherein the D50 of the diameters of the plurality of pores is 15 m to 30 m.

9. The polishing pad of claim 8, wherein the D10 of the diameters of the plurality of pores is 5 m to 20 m, and the D90 thereof is 20 m to 40 m.

10. The polishing pad of claim 1, wherein the arithmetic mean height (Sa) measured from a three-dimensional roughness profile of the polishing surface is 2 m to 7 m.

11. The polishing pad of claim 1, wherein the reduced peak height (Spk) measured from a three-dimensional roughness profile of the polishing surface is 1 m to 7 m.

12. The polishing pad of claim 1, wherein the reduced valley depth (Svk) measured from a three-dimensional roughness profile of the polishing surface is 10 m to 20 m.

13. A process for preparing a semiconductor device, which comprises: mounting the polishing pad of claim 1 on a platen; mounting a semiconductor substrate on a polishing head such that the surface, to be polished, of the semiconductor substrate is brought into contact with the polishing surface of the polishing pad; and rotating the polishing pad and the semiconductor substrate relative to each other to polish the surface, to be polished, of the semiconductor substrate.

14. The process for preparing a semiconductor device according to claim 13, wherein the area where the polishing surface comes into contact with the semiconductor substrate is 8,200 m.sup.2/1,080,000 m.sup.2 or more.

15. The process for preparing a semiconductor device according to claim 13, wherein the number of contact points between the polishing surface and the semiconductor substrate is 300/1,080,000 m.sup.2 or more.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a surface roughness graph for explaining the S-parameter.

[0016] FIGS. 2a and 2b are schematic cross-sectional views showing the number of contact points according to the shape of peaks formed on the polishing surface.

[0017] FIG. 3 is a schematic cross-sectional view for explaining the contact area ratio according to the present invention.

[0018] FIG. 4 is a schematic process flow diagram for illustrating a process for preparing a semiconductor device according to an embodiment of the present invention.

[0019] FIG. 5 is a 3D image of the polishing layer surface of the polishing pad of Example 1.

[0020] FIG. 6 is a 3D image of the polishing layer surface of the polishing pad of Comparative Example 1.

[0021] FIG. 7 is a 3D image of the polishing layer surface of the polishing pad of Comparative Example 2.

[0022] FIG. 8 is an SEM image of a cross-section of the polishing pad of Example 1.

[0023] FIG. 9 is an SEM image of a cross-section of the polishing pad of Comparative Example 1.

[0024] FIG. 10 is an SEM image of a cross-section of the polishing pad of Comparative Example 2.

[0025] FIG. 11 is an image of the surface of the monitoring wafer of Comparative Example 1.

[0026] FIG. 12 is an image of the surface of the monitoring wafer of Comparative Example 2.

BEST MODE FOR CARRYING OUT THE INVENTION

[0027] Hereinafter, the present invention will be described in detail with reference to various embodiments. The embodiments are not limited to what has been disclosed below. The embodiments may be modified into various forms as long as the gist of the invention is not altered.

[0028] In this specification, terms referring to the respective components are used to distinguish them from each other and are not intended to limit the scope of the embodiment. In addition, in the present specification, a singular expression is interpreted to cover a plural number as well unless otherwise specified in the context.

[0029] Throughout the present specification, when a part is referred to as comprising an element, it is understood that other elements may be comprised, rather than other elements are excluded, unless specifically stated otherwise.

[0030] In the present specification, when one component is described to be disposed or formed on or under another component or connected or coupled to each other, it covers the cases where these components are directly or indirectly disposed, formed, connected, or coupled through another component. In addition, it should be understood that the criterion for the terms on and under of each component may vary depending on the direction in which the object is observed.

[0031] All numerical ranges related to the physical properties, dimensions, and the like of a component used herein are to be understood as being modified by the term about, unless otherwise indicated.

[0032] In the numerical range that limits the size of components, physical properties, and the like described in the present specification, when a numerical range limited with the upper limit only and a numerical range limited with the lower limit only are separately exemplified, it should be understood that a numerical range combining these upper and lower limits is also encompassed in the exemplary scope.

Polishing Pad

[0033] The polishing pad according to embodiments of the present invention comprises a polishing surface. The polishing surface may refer to the surface of the polishing pad that faces or comes into contact with an object to be polished to polish the object in a polishing procedure.

[0034] Surface roughness may be measured for the polishing surface using an optical surface roughness measuring device. A three-dimensional optical profiler may be used as the optical surface roughness measuring device. For example, the roughness profile of the polishing surface may be measured using Bruker's Contour X-100, and the surface roughness may be obtained from the roughness profile.

[0035] A plurality of unevennesses may be present on the polishing surface. An imaginary plane located at the average height of the plurality of unevennesses may be defined as the average surface. The plurality of unevennesses may comprise peaks that protrude above the average surface and valleys that are sunken below the average surface. For example, the average surface may be an imaginary plane in which the sum of the heights (+) of the peaks and the depths () of the valleys is 0 (zero).

[0036] Surface roughness refers to a parameter indicating the size of the unevenness formed on the polishing surface by processing or polishing a polishing pad. Parameters derived from the roughness profile of the polishing surface include S-parameters, which are parameters that convert the size of the unevennesses into height in three dimensions. Examples of S-parameters include Sa, Sp, Sv, Spk, Svk, and Sz. The S-parameters may be measured according to the ISO 25178 standard.

[0037] FIG. 1 is a surface roughness graph for explaining the S-parameter. In FIG. 1, surface roughness is expressed in two dimensions for the convenience of explanation.

[0038] Sa is the arithmetic mean height measured from a roughness graph of the polishing surface. For example, Sa is a parameter that extends the surface roughness parameter Ra into three dimensions. It may be measured by converting the heights of peaks and the depths of valleys on a three-dimensional roughness graph into absolute values and taking the arithmetic mean of the converted values.

[0039] Sp is the maximum peak height measured from a roughness graph of the polishing surface. For example, it is the height of the highest peak among the peaks protruding above the average surface (P) in a three-dimensional roughness graph for the polishing surface. In the present invention, an imaginary plane located at a height of 50% of Sp may be defined as the reference surface (R).

[0040] Sv is the maximum valley depth measured from a roughness graph of the polishing surface. For example, it is the depth of the deepest valley among the valleys sunken below the average surface (P) in a three-dimensional roughness graph for the polishing surface.

[0041] Spk is the reduced peak height, which may be calculated as the average height of peaks measured in a roughness graph of the polishing surface.

[0042] Svk is the reduced valley depth, which may be calculated as the average depth of valleys measured in a roughness graph of the polishing surface.

[0043] Sz is the maximum height, which is the sum of the maximum peak height (Sp) and the maximum valley depth (Sv).

[0044] The polishing pad according to embodiments of the present invention may comprise a polishing surface on which a plurality of unevennesses are formed. The plurality of unevennesses may comprise peaks and valleys with reference to the average surface, which is the center plane of the polishing surface.

[0045] The average surface is defined as an imaginary plane located at the average height of the plurality of unevennesses. The peak is defined as a portion protruding above the average surface, and the valley is defined as a portion sunken below the average surface.

[0046] As the surface roughness and peak shape of the polishing layer are controlled, the contact area and the number of contact portions between the polishing pad and the object to be polished (e.g., semiconductor substrate) can be adjusted.

[0047] FIGS. 2a and 2b are schematic cross-sectional views showing the number of contact points according to the shape of peaks formed on the polishing surface.

[0048] In FIGS. 2a and 2b, the dotted circles indicate the portions where the polishing layer and the semiconductor substrate come into contact.

[0049] Referring to FIG. 2a, as peaks of a certain height or higher are formed sparsely on the polishing surface, the number of contact points between the polishing layer (112) and the semiconductor substrate (200) may be small. Referring to FIG. 2b, as peaks of a certain height or higher are formed densely on the polishing surface, the polishing layer (112) and the semiconductor substrate (200) may come into contact with each other at relatively many peaks.

[0050] As peaks having a uniform height are formed more densely on the polishing surface of the polishing layer (112), the number of contact points and contact area of the polishing layer for a semiconductor substrate can be sufficiently secured, and the stress between the polishing surface and the semiconductor substrate can be relieved during a polishing process, thereby preventing defects in the semiconductor substrate.

[0051] The polishing pad may comprise a polishing layer comprising a polishing surface having a plurality of pores formed therein. For example, the polishing layer has a porous structure, and the polishing layer may comprise a plurality of pores on the surface and inside. The pores support the fine flow of a polishing slurry, so that the supply or discharge of the polishing slurry can be appropriately controlled by the pores.

[0052] The contact area ratio (CAR) of the polishing surface according to the following Equation 1 is 0.76% or more.

[00002]$\begin{array}{cc}\mathrm{CAR}=\frac{{\mathrm{CA}}_{50}}{\mathrm{TA}}100\%& \left[\mathrm{Equation}1\right]\end{array}$

[0053] In Equation 1, TA is a unit area, which is 1,000 m.sup.2 or more, and when the polishing surface is measured using an optical surface roughness measuring device based on the unit area, and when an imaginary surface that is parallel to the center plane of the polishing surface and located at a height of 50% of the maximum peak height (Sp) of the polishing surface is defined as a reference surface, CA.sub.50, which is a contact area, is calculated as the total area of the regions where the peaks formed on the polishing surface are in contact with the reference surface.

[0054] FIG. 3 is a schematic cross-sectional view for explaining the contact area ratio according to the present invention. For the convenience of explanation, the polishing layer and peaks and valleys in FIG. 3 are depicted in two dimensions.

[0055] Referring to FIG. 3, an imaginary plane located at a height of 50% of Sp may be defined as a reference surface (R). The reference surface (R) extends parallel to the average surface (P) and may intersect at least some of the peaks. The contact area may refer to the sum of the regions where the peaks come into contact with the reference surface (R), for example, the cross-sectional areas of the cut peaks when the peaks are cut along the reference surface (R).

[0056] The total area of the regions where the reference surface and the peaks come into contact may be measured by obtaining a three-dimensional image or three-dimensional graph that represents the surface roughness profile of the polishing surface using an optical surface roughness measuring device; and calculating the area of pixels located at the height of the reference surface from the three-dimensional image using an image analysis program or the like.

[0057] As the contact area ratio of the polishing surface is 0.76% or more, the real contact area between the polishing pad and an object to be polished can increase in a polishing process. As a result, the polishing pressure applied to an object to be polished can be evenly distributed, and surface defects that may be caused by strong stress can be prevented.

[0058] For example, if the contact area ratio of the polishing surface is less than 0.76%, the actual contact area between the polishing pad and an object to be polished is small, so that stress may be concentrated in a local region, and polishing defects such as residues, scratches, or chatter marks on the surface of the polished object may increase. In addition, since the pressure applied to the object to be polished is not uniform, the surface roughness of the polished object may increase, and the polishing flatness may deteriorate.

[0059] In addition, in the polishing pad according to an embodiment of the present invention, as the cross-sectional area of peaks located at a height of 50% of Sp is controlled within the above range, not only the initial contact area but also the contact area provided during a polishing process can be increased, thereby further enhancing the reliability of the polishing process. For example, in the procedure of conditioning or polishing, the peaks formed on the surface of the polishing surface may be chipped or removed, thereby reducing the height of the peaks, which changes the actual contact area between the polishing pad and the polished object. According to an embodiment of the present invention, as the cross-sectional area of peaks located at a height of 50% of Sp is controlled, the desired contact area can be provided even at peaks reduced by conditioning or polishing.

[0060] In some embodiments, the contact area ratio of the polishing surface may be 1.5% or less. As a result, the polishing speed and removal rate can be enhanced together while surface defects of the polished object are suppressed. For example, if the contact area ratio exceeds 1.5%, the stress acting on an object to be polished may be reduced, resulting in a deterioration in mechanical polishing properties and frictional properties, and polishing performance may not be provided at the level required for a polishing process.

[0061] In some embodiments, the contact area ratio of the polishing surface may be 0.76% or more, 0.765% or more, 0.77% or more, 0.775% or more, 0.78% or more, or 0.782% or more, and may be 1.5% or less, 1.2% or less, 1.0% or less, 0.98% or less, 0.96% or less, 0.94% or less, 0.92% or less, 0.90% or less, 0.85% or less, 0.83% or less, 0.81% or less, 0.80% or less, or 0.79% or less.

[0062] For example, the contact area ratio (CAR) of the polishing surface may be 0.76% to 1.5%, 0.76% to 1.2%, 0.76% to 1.0%, 0.76% to 0.98%, 0.76% to 0.96%, 0.76% to 0.94%, 0.77% to 0.90%, 0.77% to 0.85%, 0.775% to 0.83%, 0.775% to 0.81%, 0.78% to 0.81%, 0.78% to 0.80%, 0.78% to 0.79%, or 0.782% to 0.79. Within the above range, polishing performance, such as polishing rate and polishing flatness, can be further enhanced, while surface defects, such as residues, scratches, and chatter marks, on the surface of the polished object can be further reduced.

[0063] In an embodiment, when a measurement region of the polishing surface is arbitrarily selected and measured with an optical surface roughness measuring device to measure the contact area, the contact area per total area (unit area) of the measurement region may be 8,200 m.sup.2/1,080,000 m.sup.2 or more. The measurement region may have a size of 1,200 m900 m. For example, the area of the measurement region may be 1,080,000 m.sup.2. Since the polishing surface has a uniform surface roughness, even if the measurement region is arbitrarily selected, the contact area per unit area may be measured to be relatively constant.

[0064] The contact area per unit area of the polishing surface may be 8,200 m.sup.2/1,080,000 m.sup.2 or more, 8,300 m.sup.2/1,080,000 m.sup.2 or more, 8,350 m.sup.2/1,080,000 m.sup.2 or more, 8,400 m.sup.2/1,080,000 m.sup.2 or more, 8,450 m.sup.2/1,080,000 m.sup.2 or more, 8,500 m.sup.2/1,080,000 m.sup.2 or more, 8,550 m.sup.2/1,080,000 m.sup.2 or more, or 8,600 m.sup.2/1,080,000 m.sup.2 or more, and may be 11,000 m.sup.2/1,080,000 m.sup.2 or less, 10,000 m.sup.2/1,080,000 m.sup.2 or less, 9,500 m.sup.2/1,080,000 m.sup.2 or less, 9,000 m.sup.2/1,080,000 m.sup.2 or less, 8,950 m.sup.2/1,080,000 m.sup.2 or less, 8,900 m.sup.2/1,080,000 m.sup.2 or less, 8,850 m.sup.2/1,080,000 m.sup.2 or less, or 8,800 m.sup.2/1,080,000 m.sup.2 or less.

[0065] For example, the contact area per unit area of the polishing surface may be 8,200 m.sup.2/1,080,000 m.sup.2 to 11,000 m.sup.2/1,080,000 m.sup.2, 8,300 m.sup.2/1,080,000 m.sup.2 to 10,000 m.sup.2/1,080,000 m.sup.2, 8,300 m.sup.2/1,080,000 m.sup.2 to 9,000 m.sup.2/1,080,000 m.sup.2, 8,350 m.sup.2/1,080,000 m.sup.2 to 9,000 m.sup.2/1,080,000 m.sup.2, 8,400 m.sup.2/1,080,000 m.sup.2 to 9,000 m.sup.2/1,080,000 m.sup.2, 8,400 m.sup.2/1,080,000 m.sup.2 to 8,950 m.sup.2/1,080,000 m.sup.2, 8,400 m.sup.2/1,080,000 m.sup.2 to 8,900 m.sup.2/1,080,000 m.sup.2, or 8,450 m.sup.2/1,080,000 m.sup.2 to 8,800 m.sup.2/1,080,000 m.sup.2.

[0066] The contact counts ratio (CCR) of the polishing surface according to the following Equation 2 may be 280/1,000,000 m.sup.2 or more.

[00003]$\begin{array}{cc}\mathrm{CCR}=\frac{k{\mathrm{CC}}_{50}}{\mathrm{TA}}\frac{1,000,000}{1,000,000}& \left[\mathrm{Equation}2\right]\end{array}$

[0067] In Equation 2, TA is a unit area, which is k m.sup.2, and k is 1,000 or more.

[0068] When the polishing surface is measured using an optical surface roughness measuring device based on the unit area, and when an imaginary surface that is parallel to the center plane of the polishing surface and located at a height of 50% of the maximum peak height (Sp) of the polishing surface is defined as a reference surface, CC.sub.50 is calculated as the total number of the regions where the peaks formed on the polishing surface are in contact with the reference surface. For example, CC.sub.50 may be the number of peaks having a height greater than 50% of Sp in the unit area.

[0069] The number of peaks that meet the reference surface may be measured by obtaining a three-dimensional image or three-dimensional graph that represents the surface roughness profile of the polishing surface using an optical surface roughness measuring device; and calculating the number of pixels located at the height of the reference surface from the three-dimensional image using an image analysis program or the like.

[0070] As the contact counts ratio of the polishing surface is 280/1,000,000 m.sup.2 or more, the number of contact points between the polishing pad and an object to be polished can increase in a polishing process. As the number of contact points increases, stress can be prevented from being concentrated in a local region, and less debris may be formed in the procedure of polishing or conditioning, which can reduce surface defects of the polished object. For example, if the contact counts ratio of the polishing surface is less than 280/1,000,000 m.sup.2, the peaks brought into contact with the object to be polished are sparsely distributed, whereby stress may not be smoothly distributed and relieved.

[0071] In addition, as the polishing pad has a high contact area for an object to be polished, while the contact counts per unit area increase, stress can be distributed more efficiently, and uniform polishing can be performed overall on the surface of the object to be polished.

[0072] The contact counts per unit area of the polishing surface may be 1,000/1,000,000 m.sup.2 or less. As a result, the polishing speed, removal rate of a film substance to be polished, and polishing efficiency can be further enhanced.

[0073] For example, if the contact counts per unit area exceeds 1,000/1,000,000 m.sup.2, the individual contact area of each peak in contact with the film substance to be polished is excessively reduced, whereby the mechanical stress and friction for the film substance to be polished are not sufficiently secured, which may rather reduce the polishing characteristics, and the surface roughness of the object to be polished may actually increase upon polishing, which may deteriorate the polishing uniformity.

[0074] In an embodiment, the contact counts per unit area of the polishing surface may be 280/1,000,000 m.sup.2 or more, 285/1,000,000 m.sup.2 or more, 290/1,000,000 m.sup.2 or more, 295/1,000,000 m.sup.2 or more, or 300/1,000,000 m.sup.2 or more, and may be 1,000/1,000,000 m.sup.2 or less, 800/1,000,000 m.sup.2 or less, 600/1,000,000 m.sup.2 or less, 500/1,000,000 m.sup.2 or less, 450/1,000,000 m.sup.2 or less, 400/1,000,000 m.sup.2 or less, 350/1,000,000 m.sup.2 or less, or 330/1,000,000 m.sup.2 or less.

[0075] In an embodiment, the contact counts per unit area of the polishing surface may be 280/1,000,000 m.sup.2 to 1,000/1,000,000 m.sup.2, 280/1,000,000 m.sup.2 to 800/1,000,000 m.sup.2, 280/1,000,000 m.sup.2 to 600/1,000,000 m.sup.2, 280/1,000,000 m.sup.2 to 500/1,000,000 m.sup.2, 290/1,000,000 m.sup.2 to 500/1,000,000 m.sup.2, 290/1,000,000 m.sup.2 to 450/1,000,000 m.sup.2, 290/1,000,000 m.sup.2 to 400/1,000,000 m.sup.2, 290/1,000,000 m.sup.2 to 350/1,000,000 m.sup.2, or 300/1,000,000 m.sup.2 to 330/1,000,000 m.sup.2.

[0076] In an embodiment, when a measurement region of the polishing surface is arbitrarily selected and measured with an optical surface roughness measuring device to measure the contact area, the contact counts per total area (unit area) of the measurement region may be 300/1,080,000 m.sup.2 or more. The measurement region may have a size of 1,200 m900 m. For example, the area of the measurement region may be 1,080,000 m.sup.2. Since the polishing surface has a uniform surface roughness, even if the measurement region is arbitrarily selected, the contact counts per unit area may be measured to be relatively constant.

[0077] The contact counts per unit area of the polishing surface may be 300/1,080,000 m.sup.2 or more, 305/1,080,000 m.sup.2 or more, 310/1,080,000 m.sup.2 or more, 315/1,080,000 m.sup.2 or more, 320/1,080,000 m.sup.2 or more, or 325/1,080,000 m.sup.2 or more, and may be 1,000/1,080,000 m.sup.2 or less, 800/1,080,000 m.sup.2 or less, 600/1,080,000 m.sup.2 or less, 500/1,080,000 m.sup.2 or less, 450/1,080,000 m.sup.2 or less, 400/1,080,000 m.sup.2 or less, 350/1,080,000 m.sup.2 or less, 340/1,080,000 m.sup.2 or less, or 330/1,080,000 m.sup.2 or less.

[0078] For example, the contact counts per unit area of the polishing surface may be 300/1,080,000 m.sup.2 to 1,000/1,080,000 m.sup.2, 300/1,080,000 m.sup.2 to 800/1,080,000 m.sup.2, 300/1,080,000 m.sup.2 to 600/1,080,000 m.sup.2, 300/1,080,000 m.sup.2 to 500/1,080,000 m.sup.2, 310/1,080,000 m.sup.2 to 500/1,080,000 m.sup.2, 310/1,080,000 m.sup.2 to 450/1,080,000 m.sup.2, 310/1,080,000 m.sup.2 to 400/1,080,000 m.sup.2, 310/1,080,000 m.sup.2 to 350/1,080,000 m.sup.2, 320/1,080,000 m.sup.2 to 350/1,080,000 m.sup.2, 320/1,080,000 m.sup.2 to 340/1,080,000 m.sup.2, or 320/1,080,000 m.sup.2 to 330/1,080,000 m.sup.2.

[0079] A measurement region for measuring the contact area and the contact counts of the polishing surface may be randomly selected from the polishing surface. In light of measurement errors and deviations, the contact area and the contact counts are measured in one, two, three, or five or more measurement regions of the polishing surface, respectively, and the contact area and the contact counts are obtained by taking the arithmetic mean of the measured values.

[0080] In some embodiments, the arithmetic mean height (Sa) measured from a three-dimensional roughness profile of the polishing surface may be 7 m or less. For example, the Sa of the polishing surface may be 2 m to 7 m, 3 m to 7 m, 4 m to 7 m, 5.0 m to 6.5 m, 5.0 m to 6.2 m, 5.2 m to 6.2 m, 5.4 m to 6.1 m, or 5.5 m to 6.0 m. Within the above range, the surface roughness of the polishing surface can be appropriately controlled to increase the removal rate and polishing speed while surface defects of the semiconductor substrate are more efficiently suppressed.

[0081] In some embodiments, the reduced peak height (Spk) measured from a three-dimensional roughness profile of the polishing surface may be 7 m or less. For example, the Spk of the polishing surface may be 1 m to 7 m, 1.0 m to 6.5 m, 2.0 m to 6.5 m, 3.0 m to 6.5 m, 4 m to 6 m, 5 m to 6 m, or 5.5 m to 6 m. Spk may affect the contact stress between the polishing pad and the film substance to be polished. As the Spk of the polishing surface is within the above range, the polishing rate can be further enhanced while surface defects such as scratches and chatter marks are suppressed.

[0082] In some embodiments, the reduced valley depth (Svk) measured from a three-dimensional roughness profile of the polishing surface may be 20 m or less in absolute value. For example, the Svk of the polishing surface may be an absolute value of 10 m to 20 m, 10 m to 19 m, 10 m to 18 m, 13 m to 17 m, or 15 m to 17 m. SVK may have an impact on the polishing slurry holding capacity or debris capture capacity. As the Svk of the polishing surface is within the above range, the polishing pad can have enhanced polishing performance while surface defects of the film substance to be polished are further suppressed.

[0083] In some embodiments, the maximum peak height (Sp) measured from a three-dimensional roughness profile of the polishing surface may be 30 m or less. For example, the Sp of the polishing surface may be 20 m to 30 m, 22 m to 30 m, 25 m to 30 m, 25 m to 29 m, or 27 m to 29 m.

[0084] In some embodiments, the maximum valley depth (Sv) measured from a three-dimensional roughness profile of the polishing surface may be 60 m or less in absolute value. For example, the Sv of the polishing surface may be an absolute value of 40 m to 60 m, 45 m to 60 m, 50 m to 60 m, 52 m to 60 m, 54 m to 60 m, or 54 m to 58 m.

[0085] As the Sp and Sv of the polishing surface are within the above ranges, the friction parts between the polishing pad and the film substance to be polished, and the reaction regions between the film substance to be polished and the slurry can be sufficiently secured while the polishing surface can have a relatively uniform surface roughness. Thus, the occurrence of surface defects and the deterioration in polishing flatness due to a locally excessively different structure of the polishing surface can be prevented.

[0086] The surface roughness, and the contact area and the contact counts per unit area of the polishing surface may be measured after conditioning the polishing layer for 100 minutes. The equipment used for conditioning is PWR 300 of G&P Technology. The conditioning pressure is 6 lbf, the rotation speed is 10 to 110 rpm, and the disk used for conditioning is CI45 of Sasol.

[0087] The pore uniformity of the polishing layer represented by the following Equation 3 may be 0.6 or less.

[00004]$\begin{array}{cc}\mathrm{Pore}\mathrm{uniformity}=\frac{D90-D10}{D50}& \left[\mathrm{Equation}3\right]\end{array}$

[0088] In Equation 3, D10, D50, and D90 are the diameters of the pores at the cumulative volume fractions of 10%, 50%, and 90%, respectively, in a volume distribution obtained by accumulating the pores in order of diameter from smallest to largest.

[0089] The diameter and volume of the pores may be measured using a scanning electron microscope (SEM). For example, a cross-section of the polishing layer is photographed using a scanning electron microscope to obtain an image, and the diameter, area, volume, and number of pores may be calculated from the obtained image using image analysis software. For example, the volume of a pore with a radius of r may be calculated as 4r.sup.3/3.

[0090] The pores may be accumulated in order of diameter from smallest to largest to obtain a volume distribution, and the D10, D50, and D90 of the pores may be measured, respectively, from the volume distribution. D10 is the diameter of the pore at a cumulative volume fraction of 10% in the volume distribution. D50 is the diameter of the pore at a cumulative volume fraction of 50% in the volume distribution. D90 is the diameter of the pore at a cumulative volume fraction of 90% in the volume distribution.

[0091] The pore uniformity represented by the above Equation 3 may be an indicator of the degree to which the size of the pores contained in the polishing layer is uniform. For example, as D90 becomes smaller and D10 becomes larger, the pore uniformity may become lower. To the contrary, as D90 becomes larger and D10 becomes smaller, the pore uniformity may become higher. In addition, as D50 decreases relative to the difference between D90 and D10, the pore uniformity may increase. The smaller the pore uniformity, the more uniform the size of the pores distributed within the polishing layer.

[0092] Uniform pore size within the polishing layer may have an impact on the surface roughness of the polishing layer. For example, pores with a small size push the surface of the polishing layer less, and pores with a large size push the surface of the polishing layer more. Thus, as the deviation in the sizes of pores distributed within the polishing layer increases, the difference in elevation between regions on the polishing layer surface may increase. In such a case, the height deviation between peaks on the surface of the polishing layer may increase, or the spacing between peaks may be widened, resulting in a sparse distribution of peaks. Accordingly, the contact area or the contact counts between the polishing pad and the film substance to be polished may be reduced.

[0093] According to embodiments of the present invention, as the pore uniformity of the polishing layer is controlled to 0.6 or less, the deviation in the sizes of pores within the polishing layer can be reduced. As a result, the surface roughness on the polishing surface can be readily controlled, so that the number and area of peaks located at a desired height on the surface of the polishing layer can be further increased.

[0094] The pore uniformity of the polishing layer may be 0.55 or less, 0.50 or less, 0.49 or less, 0.48 or less, or 0.47 or less, and may be 0.1 or more, 0.2 or more, 0.25 or more, 0.30 or more, 0.40 or more, or 0.45 or more. For example, the pore uniformity of the polishing layer may be 0.1 to 0.6, 0.1 to 0.55, 0.1 to 0.50, 0.2 to 0.49, 0.2 to 0.48, 0.30 to 0.48, 0.40 to 0.48, or 0.45 to 0.47.

[0095] In some embodiments, the D50 of the diameters of the plurality of pores may be 15 m to 30 m. For example, the D50 of the diameters of the plurality of pores may be 15 m to 28 m, 18 m to 28 m, 20 m to 28 m, or 20 m to 25 m.

[0096] In an embodiment, the D90 of the diameters of the plurality of pores may be 20 m to 40 m. For example, the D90 of the diameters of the plurality of pores may be 20 m to 35 m, 20 m to 30 m, 22 m to 30 m, or 25 m to 30 m.

[0097] For example, the D50 of the diameters of the plurality of pores may be 15 m to 30 m, and the D90 thereof may be 20 m to 40 m.

[0098] Within the above ranges, smaller and more uniform pores are distributed to facilitate the inflow and diffusion of a slurry on the polishing surface, and the generation and agglomeration of debris can be suppressed, thereby further enhancing the processing quality of the surface of an object to be polished.

[0099] In an embodiment, the D10 of the diameters of the plurality of pores may be 5 m to 20 m. For example, the D10 of the diameters of the plurality of pores may be 8 m to 20 m, 10 m to 20 m, 10 m to 18 m, or 14 m to 18 m. Within the above range, as fine-sized pores are formed within the polishing layer, the surface properties of the polishing surface can be readily controlled within a desired range, and as the inflow and movement of a slurry can be facilitated through pores larger than a certain size, the polishing performance and efficiency can be further enhanced.

[0100] In some embodiments, the ratio of D50 to the average diameter (Dn) of the plurality of pores (D50/Dn) may be 1.4 or less. The average diameter (Dn) may be calculated by dividing the sum of the diameters of the plurality of pores by the number of the plurality of pores. The smaller the difference between Dn, which is the arithmetic mean of the diameters of the pores, and D50, which is measured from the volume cumulative distribution, the more uniform the size of the pores distributed within the polishing layer may be.

[0101] The ratio of D50 to the average diameter (Dn) of the plurality of pores (D50/Dn) may be 0.7 or more, 0.8 or more, or 0.9 or more, and may be 1.3 or less, 1.25 or less, 1.2 or less, or 1.1 or less. For example, the ratio (D50/Dn) may be 0.7 to 1.4, 0.7 to 1.3, 0.8 to 1.3, 0.8 to 1.2, 0.9 to 1.2, or 0.9 to 1.1. Within the above range, surface defects of a film substance to be polished can be further suppressed, so that the polishing and processing quality can be further enhanced.

[0102] In an embodiment, the average diameter (Dn) of the plurality of pores may be 10 m to 25 m. For example, the Dn of the plurality of pores may be 10 m to 22 m, 12 m to 22 m, 15 m to 22 m, or 15 m to 20 m.

[0103] The pores may be derived from a solid phase foaming agent. For example, the size, shape change, agglomeration, distribution, and the like of pores formed within the polishing layer may be controlled by the type, content, injection conditions, average particle size, and purification of the solid phase foaming agent.

[0104] The polishing layer may have a thickness of 0.5 mm to 5 mm. For example, the thickness of the polishing layer may be 0.8 mm to 4.0 mm, 1.0 mm to 3.0 mm, 1.5 mm to 2.5 mm, 1.7 mm to 2.3 mm, or 2.0 mm to 2.2 mm. Within the above range, the physical properties of the polishing pad required for a CMP process can be more readily secured.

[0105] The polishing pad may further comprise a support layer. For example, the polishing pad may comprise a support layer and a polishing layer disposed on the support layer. The support layer is positioned under the polishing layer to stably support the polishing layer while absorbing and/or dispersing the impact imposed on the polishing layer.

[0106] The support layer may be prepared using a nonwoven fabric, suede, or a porous pad.

[0107] The support layer may be a resin-impregnated nonwoven fabric. The nonwoven fabric may be a fibrous nonwoven fabric comprising one selected from the group consisting of a polyester fiber, a polyamide fiber, a polypropylene fiber, a polyethylene fiber, and combinations thereof.

[0108] The resin impregnated in the nonwoven fabric may comprise a polyurethane resin, a polybutadiene resin, a styrene-butadiene copolymer resin, a styrene-butadiene-styrene copolymer resin, an acrylonitrile-butadiene copolymer resin, a styrene-ethylene-butadiene-styrene copolymer resin, a silicone rubber resin, a polyester-based elastomer resin, a polyamide-based elastomer resin, and combinations thereof.

[0109] The thickness of the support layer may be, for example, 0.5 mm to 4 mm, 0.6 mm to 3.5 mm, 0.8 mm to 3 mm, or 1 mm to 2 mm. Within the above range, the support layer can stably support the polishing layer to readily disperse impact, and the polishing pad can be made lighter.

[0110] The polishing pad may further comprise an adhesive layer. For example, the adhesive layer may come into contact with the upper side of the support layer and the lower side of the polishing layer (the side opposite to the polishing surface) to serve to bond the support layer and the polishing layer. Further, the adhesive layer may also serve as a barrier layer to prevent a polishing slurry supplied to the polishing layer from leaking into the support layer.

[0111] For example, the polishing pad may have a laminated structure of a support layer, an adhesive layer, and a polishing layer.

[0112] In an embodiment, the adhesive layer may be formed using a hot melt adhesive composition.

[0113] The hot melt adhesive composition may comprise a hot melt adhesive commonly known. In an embodiment, the hot melt adhesive may comprise a polyurethane resin, a polyester resin, an ethylene-vinyl acetate resin, a polyamide resin, and/or a polyolefin resin. They may be used alone or in combination of two or more.

[0114] The thickness of the adhesive layer may be, for example, 5 m to 30 m, 10 m to 30 m, 20 m to 27 m, or 23 m to 25 m. Within the above range, the bonding strength between the polishing layer and the support layer can be further enhanced, and the polishing pad can be made thinner and lighter.

[0115] The polishing layer may comprise a resin. For example, the polishing layer may comprise a urethane-based resin.

[0116] The polishing layer may be prepared from a raw material mixture that comprises a urethane-based prepolymer, a curing agent, and a foaming agent.

[0117] A prepolymer generally refers to a polymer having a relatively low molecular weight wherein the degree of polymerization is adjusted to an intermediate level for the sake of conveniently molding a product in the process of producing the same. A prepolymer may be molded by itself or after a reaction with another polymerizable compound. For example, a prepolymer may be prepared by reacting an isocyanate compound with a polyol.

[0118] The urethane-based prepolymer may be prepared by reacting an isocyanate compound with a polyol.

[0119] For example, the isocyanate compound may comprise at least one compound selected from the group consisting of toluene diisocyanate (TDI), naphthalene-1,5-diisocyanate, p-phenylene diisocyanate, tolidine diisocyanate, 4,4-diphenyl methane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate.

[0120] For example, the polyol may comprise at least one compound selected from the group consisting of a polyether polyol, a polyester polyol, a polycarbonate polyol, and an acryl polyol. In an embodiment, the polyol may have a weight average molecular weight (Mw) of 300 g/mole to 3,000 g/mole.

[0121] In an embodiment, the urethane-based prepolymer may be a polymer prepared by reacting an isocyanate compound comprising toluene diisocyanate and a polyol comprising polytetramethylene ether glycol.

[0122] In some embodiments, the urethane-based prepolymer may have a weight average molecular weight of 500 g/mole to 3,000 g/mole. Specifically, the urethane-based prepolymer may have a weight average molecular weight of 600 g/mole to 2,000 g/mole or 800 g/mole to 1,000 g/mole.

[0123] In an embodiment, the urethane-based prepolymer may have an isocyanate terminal group (terminal NCO) content (NCO %) of 5% by weight to 15% by weight based on the total weight of the urethane-based prepolymer. For example, the terminal NCO content (NCO %) of the urethane-based prepolymer may be 6% by weight to 13% by weight, 7% by weight to 12% by weight, 7.5% by weight to 11% by weight, or 8% by weight to 10% by weight.

[0124] The curing agent may comprise an amine compound and/or an alcohol compound. For example, the curing agent may comprise at least one compound selected from the group consisting of an aromatic amine, an aliphatic amine, an aromatic alcohol, and an aliphatic alcohol.

[0125] For example, the curing agent may comprise at least one selected from the group consisting of 4,4-methylenebis(2-chloroaniline) (MOCA), diethyltoluenediamine, diaminodiphenylmethane, diaminodiphenyl sulphone, m-xylylene diamine, isophoronediamine, ethylenediamine, diethylenetriamine, triethylenetetramine, polypropylenediamine, polypropylenetriamine, ethylene glycol, diethylene glycol, dipropylene glycol, butanediol, hexanediol, glycerin, trimethylolpropane, and bis(4-amino-3-chlorophenyl) methane.

[0126] The content of the curing agent may be 3.0 parts by weight to 40 parts by weight based on 100 parts by weight of the raw material mixture.

[0127] The urethane-based prepolymer and the curing agent may be mixed at a molar equivalent ratio of 1:0.8 to 1:1.2, or a molar equivalent ratio of 1:0.9 to 1:1.1, based on the number of moles of the reactive groups in each molecule. Here, the number of moles of the reactive groups in each molecule refers to, for example, the number of moles of the isocyanate group in the urethane-based prepolymer and the number of moles of the reactive groups (e.g., amine group, alcohol group, and the like) in the curing agent. The urethane-based prepolymer and the curing agent may be added during the mixing process so as to satisfy the molar equivalent ratio described above and react with each other. As the curing reaction is carried out at the above reaction ratio, the curing reaction can be optimized, whereby it is possible to provide a polishing pad with the physical properties required for a CMP process.

[0128] The foaming agent may comprise a solid phase foaming agent, a liquid phase foaming agent, or a gas phase foaming agent. Specifically, the foaming agent may comprise a solid phase foaming agent and/or a gas phase foaming agent, more specifically, a solid phase foaming agent. Pores may be formed on the surface and inside of the polishing layer by the foaming agent.

[0129] The solid phase foaming agent may have an average particle diameter (D.sub.50) of 1 m to 15 m. The average particle diameter (D.sub.50) of the solid phase foaming agent may be defined as the particle diameter at a volume fraction of 50% in a volume particle distribution obtained by accumulating the particles in order of increasing particle diameter. For example, the purification system can filter out particles having excessively small or large particle sizes, so that the average particle size of the solid phase foaming agent can be controlled within the above range.

[0130] The average particle diameter (D.sub.50) of the solid phase foaming agent may be 3 m to 15 m, 3 m to 12 m, 3 m to 10 m, 4 m to 10 m, 5 m to 10 m, or 6 m to 9 m. Within the above range, the size and distribution of pores within the polishing layer, or the surface roughness of the polishing surface, can be readily controlled within the above range.

[0131] The solid phase foaming agent may have a density of 25 kg/m.sup.3 or less. As a result, agglomeration and coalescence of pores can be prevented during the mixing and curing process of the raw material mixture, and pores having a uniform size and distribution can be formed inside the polishing layer. For example, the density of the solid phase foaming agent may be greater than 0 kg/m.sup.3 to 25 kg/m.sup.3 or less, 5 kg/m.sup.3 to 25 kg/m.sup.3, or 10 kg/m.sup.3 to 25 kg/m.sup.3 or less. In some embodiments, the solid phase foaming agent may have a thermal decomposition initiation temperature (Tstart) of 95 C. to 110 C. The thermal decomposition initiation temperature may refer to the temperature at which the weight of the solid phase foaming agent begins to decrease when it is heated at a heating rate of 10 C./minute from 0 C. in a nitrogen gas atmosphere. For example, the thermal decomposition initiation temperature of the solid phase foaming agent may be 98 C. to 110 C., 100 C. to 110 C., or 100 C. to 108 C.

[0132] In some embodiments, the solid phase foaming agent may have a maximum thermal decomposition temperature (Tmax) of 130 C. to 170 C. The maximum thermal decomposition temperature of the solid phase foaming agent may refer to the temperature at which the solid phase foaming agent is completely melted when it is heated at a heating rate of 10 C./minute from 0 C. in a nitrogen gas atmosphere. For example, the maximum thermal decomposition temperature of the solid phase foaming agent may be 135 C. to 170 C., 140 C. to 165 C., or 143 C. to 160 C.

[0133] When the thermal decomposition initiation temperature and maximum thermal decomposition temperature of the solid phase foaming agent are each within the above ranges, the pore characteristics such as size, distribution, and content of pores to be formed within the polishing pad can be more precisely controlled. Accordingly, it is possible to readily prepare a polishing pad that provides a desired range of polishing amounts and dishing values.

[0134] In some embodiments, the solid phase foaming agent may comprise thermally expanded particles. When the solid phase foaming agent comprises thermally expanded particles, the D50 of the solid phase foaming agent may refer to the average particle diameter in a thermally expanded state. The thermally expanded particles may be obtained by thermally expanding thermally expandable particles.

[0135] The thermally expandable particles may comprise a shell comprising a thermoplastic resin and a foaming agent encapsulated inside the shell. The thermoplastic resin may comprise at least one copolymer selected from the group consisting of a vinylidene chloride-based copolymer, an acrylonitrile-based copolymer, a methacrylonitrile-based copolymer, and an acryl-based copolymer.

[0136] In an embodiment, the foaming agent encapsulated in the inside may comprise a hydrocarbon compound having 1 to 7 carbon atoms. For example, the foaming agent encapsulated in the inside may comprise a low molecular weight hydrocarbon such as ethane, ethylene, propane, propene, n-butane, isobutane, butene, isobutene, n-pentane, isopentane, neopentane, n-hexane, heptane, petroleum ether, and the like; a chlorofluorohydrocarbon such as trichlorofluoromethane (CCl.sub.3F), dichlorodifluoromethane (CCl.sub.2F.sub.2), chlorotrifluoromethane (CClF.sub.3), tetrafluoroethylene (CClF.sub.2CClF.sub.2), and the like; or tetramethylsilane, trimethylethylsilane, trimethylisopropylsilane, trimethyl-n-propylsilane, and the like. They may be used alone or in combination of two or more.

[0137] The content of the solid phase foaming agent may be 0.5 part by weight to 5.0 parts by weight based on 100 parts by weight of the raw material mixture. For example, the content of the solid phase foaming agent may be 0.5 part by weight to 3.5 parts by weight, 0.5 part by weight to 3.0 parts by weight, 0.5 part by weight to 2.0 parts by weight, 0.5 part by weight to 1.5 parts by weight, or 0.8 part by weight to 1.4 parts by weight, based on 100 parts by weight of the raw material mixture. Within the above range, the size, distribution, and content of pores within the polishing layer can be controlled within desired ranges while the physical properties of the polishing pad, such as hardness, tensile strength, and elongation, are not deteriorated.

[0138] In some embodiments, the raw material mixture may comprise 55 parts by weight to 96.5 parts by weight of the urethane-based prepolymer, 0.5 part by weight to 5.0 parts by weight of the foaming agent, and 3.0 parts by weight to 40 parts by weight of the curing agent based on 100 parts by weight of the raw material mixture. For example, the raw material mixture may comprise 66.5 parts by weight to 96.5 parts by weight of the urethane-based prepolymer, 0.5 part by weight to 3.5 parts by weight of the foaming agent, and 5.0 parts by weight to 35 parts by weight of the curing agent based on 100 parts by weight of the raw material mixture.

[0139] In some embodiments, the raw material mixture may further comprise a surfactant. The surfactant may prevent the pores from cohesion and coalescing with each other. For example, the surfactant may be a silicone-based nonionic surfactant. But other surfactants may be variously selected depending on the physical properties required for the polishing pad.

[0140] As the silicone-based nonionic surfactant, a silicone-based nonionic surfactant having a hydroxyl group may be used alone, or a silicone-based nonionic surfactant having a hydroxyl group and a silicone-based nonionic surfactant having no hydroxyl group may be used together.

[0141] The content of the surfactant may be 0.1 part by weight to 2 parts by weight, 0.2 part by weight to 1.8 parts by weight, 0.2 part by weight to 1.7 parts by weight, 0.2 part by weight to 1.6 parts by weight, or 0.2 part by weight to 1.5 parts by weight, based on 100 parts by weight of the raw material mixture. Within the above range, pores derived from the foaming agent can be stably formed and maintained during the curing or molding process.

[0142] The raw material mixture may be reacted to form a solid polyurethane. For example, the isocyanate terminal group (NCO group) in the urethane-based prepolymer can react with an amine group, an alcohol group, and the like in the curing agent during the reaction. The solid phase foaming agent can be uniformly dispersed in the solid polyurethane to form a plurality of pores without participating in the curing reaction.

[0143] In an embodiment, the solid polyurethane may be prepared in a sheet form.

[0144] In some embodiments, the forming or curing process may be carried out using a mold. For example, the raw material mixture may be injected into a mold and molded. Specifically, the raw material mixture stirred in a mixing head or the like may be injected into a mold to fill the inside thereof.

[0145] In an embodiment, in the process of mixing and dispersing the urethane-based prepolymer, the solid phase foaming agent, and the curing agent, they are mixed at a rotational speed of the mixing head of 500 rpm to 10,000 rpm, specifically, 1,000 rpm to 9,000 rpm, 2,000 rpm to 9,000 rpm, 3,000 to 8,000 rpm, 4,000 to 8,000 rpm, or 5,000 rpm to 7,000 rpm. Within the above range, the shape of the pores contained in the polishing pad can be more readily controlled within a desired range.

[0146] The reaction between the urethane-based prepolymer and the curing agent is completed in the mold to thereby produce a molded body in the form that conforms to the shape of the mold.

[0147] The molded body may be appropriately sliced or cut into a sheet for the production of a polishing layer. For example, the raw material mixture may be molded in a mold having a height of 5 times to 50 times the thickness of a polishing layer to be finally produced, and the molded body is then sliced in the same thickness to produce a plurality of sheets for the polishing layers at the same time.

[0148] In an embodiment, a reaction retarder as a reaction rate controlling agent may be further mixed in order to secure a sufficient solidification time.

[0149] The reaction retarder may comprise at least one selected from the group consisting of triethylenediamine, dimethylethanolamine, tetramethylbutanediamine, 2-methyl-triethylenediamine, dimethylcyclohexylamine, triethylamine, triisopropanolamine, 1,4-diazabicyclo(2,2,2) octane, bis(2-methylaminoethyl) ether, trimethylaminoethylethanolamine, N,N,N,N,N-pentamethyldiethyldimethylaminoethylamine, dimethylaminopropylamine, benzyldimethylamine, N-ethylmorpholine, N,N-dimethylaminoethylmorpholine, N,N-dimethylcyclohexylamine, 2-methyl-2-azanobornene, dibutyltin dilaurate, stannous octoate, dibutyltin diacetate, dioctyltin diacetate, dibutyltin maleate, dibutyltin di-2-ethylhexanoate, and dibutyltin dimercaptide.

Process for Preparing a Semiconductor Device

[0150] In the process for preparing a semiconductor device according to embodiments of the present invention, a semiconductor substrate may be polished using the polishing pad described above.

[0151] The polishing pad may be mounted on a platen. The polishing pad may be mounted on the platen with the polishing surface of the polishing layer facing upward. A semiconductor substrate may be positioned on the polishing pad such that the polishing surface of the polishing pad and the surface (surface to be polished) of the semiconductor substrate are in contact. For example, the semiconductor substrate is mounted on a polishing head and can be in direct contact with the polishing surface of the polishing pad.

[0152] FIG. 4 is a schematic process flow diagram for illustrating a process for preparing a semiconductor device according to an embodiment of the present invention.

[0153] Referring to FIG. 4, a polishing pad (100) may be mounted on a platen (310). The polishing pad (100) may be mounted on the platen (310) with the polishing surface (110) of the polishing layer facing upward.

[0154] A semiconductor substrate (200) may be positioned on the polishing pad (100) such that the polishing surface (110) of the polishing pad (100) and the surface (surface to be polished) of the semiconductor substrate (200) are in contact. For example, the semiconductor substrate (200) is mounted on a polishing head (320) and can be in direct contact with the polishing surface of the polishing pad (100).

[0155] In an embodiment, a polishing slurry (340) may be sprayed onto the polishing pad (100) for polishing. The polishing slurry (340) may be sprayed through a nozzle (330). The flow rate of the polishing slurry (340) sprayed through the nozzle (330) may be controlled within the range of 10 ml/minute to 1,000 ml/minute, 50 ml/minute to 500 ml/minute, 150 ml/minute to 500 ml/minute, or 150 ml/minute to 350 ml/minute.

[0156] The polishing pad (100) and the semiconductor substrate (200) may be rotated relative to each other to polish the surface, to be polished, of the semiconductor substrate (200) to be polished. In an embodiment, the rotation direction of the polishing pad (100) and the rotation direction of the semiconductor substrate (200) may be the same. In an embodiment, the rotation direction of the polishing pad (100) and the rotation direction of the semiconductor substrate (200) may be opposite to each other.

[0157] As described through FIGS. 2a and 2b above, as the contact area and the contact counts per unit area of the polishing surface are adjusted within the above ranges, the area and the number of contact points where the polishing surface (110) and the semiconductor substrate (200) come into contact with each other can be appropriately controlled. As a result, while excellent polishing properties for a semiconductor substrate (200) are provided, the surface properties of the semiconductor substrate upon polishing can be enhanced by preventing the agglomeration of debris and suppressing an increase in stress.

[0158] In an embodiment, the area where the polishing surface (110) comes into contact with the semiconductor substrate (200) may be 8,200 m.sup.2/1,080,000 m.sup.2 or more. The above contact area may be obtained by arbitrarily selecting a measurement region having a size of 1,200 m900 m among the areas where the polishing surface (110) and the semiconductor substrate (200) overlap; and measuring the entire area where the polishing surface (110) comes into contact with the semiconductor substrate (200) within the measurement region.

[0159] For example, the contact area between the polishing surface (110) and the semiconductor substrate (200) may be 8,200 m.sup.2/1,080,000 m.sup.2 to 11,000 m.sup.2/1,080,000 m.sup.2, 8,300 m.sup.2/1,080,000 m.sup.2 to 10,000 m.sup.2/1,080,000 m.sup.2, 8,300 m.sup.2/1,080,000 m.sup.2 to 9,000 m.sup.2/1,080,000 m.sup.2, 8,350 m.sup.2/1,080,000 m.sup.2 to 9,000 m.sup.2/1,080,000 m.sup.2, 8,400 m.sup.2/1,080,000 m.sup.2 to 9,000 m.sup.2/1,080,000 m.sup.2, 8,400 m.sup.2/1,080,000 m.sup.2 to 8,950 m.sup.2/1,080,000 m.sup.2, 8,400 m.sup.2/1,080,000 m.sup.2 to 8,900 m.sup.2/1,080,000 m.sup.2, or 8,450 m.sup.2/1,080,000 m.sup.2 to 8,800 m.sup.2/1,080,000 m.sup.2.

[0160] In an embodiment, the number of contact points between the polishing surface (110) and the semiconductor substrate (200) may be 300/1,080,000 m.sup.2 or more. The above number of contact points may be obtained by arbitrarily selecting a measurement region having a size of 1,200 m900 m among the areas where the polishing surface (110) and the semiconductor substrate (200) overlap; and measuring the total number of contact points where the polishing surface (110) comes into contact with the semiconductor substrate (200) within the measurement region.

[0161] For example, the number of contact points between the polishing surface (110) and the semiconductor substrate (200) may be 300/1,080,000 m.sup.2 to 1,000/1,080,000 m.sup.2, 300/1,080,000 m.sup.2 to 800/1,080,000 m.sup.2, 300/1,080,000 m.sup.2 to 600/1,080,000 m.sup.2, 300/1,080,000 m.sup.2 to 500/1,080,000 m.sup.2, 310/1,080,000 m.sup.2 to 500/1,080,000 m.sup.2, 310/1,080,000 m.sup.2 to 450/1,080,000 m.sup.2, 310/1,080,000 m.sup.2 to 400/1,080,000 m.sup.2, 310/1,080,000 m.sup.2 to 350/1,080,000 m.sup.2, 320/1,080,000 m.sup.2 to 350/1,080,000 m.sup.2, 320/1,080,000 m.sup.2 to 340/1,080,000 m.sup.2, or 320/1,080,000 m.sup.2 to 330/1,080,000 m.sup.2.

[0162] In an embodiment, the rotation speed of the polishing pad (100) and the rotation speed of the semiconductor substrate (200) may be 10 rpm to 500 rpm, 30 rpm to 200 rpm, or 50 rpm to 150 rpm, respectively.

[0163] In an embodiment, the semiconductor substrate (200) mounted on the polishing head (320) is pressed against the polishing surface of the polishing pad (100) at a predetermined load. The load applied to the polishing surface of the polishing pad (100) and the surface, to be polished, of the semiconductor substrate (200) by the polishing head (320) may be 1 gf/cm.sup.2 to 1,000 gf/cm.sup.2, or 10 gf/cm.sup.2 to 800 gf/cm.sup.2.

[0164] In an embodiment, in order to maintain the polishing surface of the polishing pad (100) in a state suitable for polishing, the process for preparing a semiconductor device may further comprise processing the polishing surface of the polishing pad (100) with a conditioner. The conditioning process for the polishing surface may be carried out simultaneously with the polishing of the semiconductor substrate (200).

[0165] Hereinafter, the present invention is explained in detail by the following Examples. However, these examples are set forth to illustrate the present invention, and the scope of the present invention is not limited thereto.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Example 1

Preparation of a Urethane-Based Prepolymer

[0166] Toluene diisocyanate (TDI, BASF) as an isocyanate compound and polytetramethylene ether glycol (PTMEG, Korea PTG) as a polyol were mixed such that the content of the NCO group was 9.1% by weight and then reacted. In order to minimize side reactions during the synthesis, they were stirred at a reaction temperature of 75 C. for 3 hours to carry out the reaction, thereby preparing a urethane-based prepolymer having a content of the NCO group of 9.1% by weight.

Preparation of a Polishing Layer

[0167] The urethane-based prepolymer prepared above, a curing agent, and a foaming agent were mixed to prepare a raw material mixture. Triethylenediamine (Dow) as a curing agent and microcapsules (Expancel 044DU20, Noutyon) as a solid phase foaming agent were used. The elemental composition of the solid phase foaming agent was measured using an inductively coupled plasma emission spectrometer (Aglient 5110 ICP-OES). The composition ratio of elements contained in the solid phase foaming agent was measured as Ca:Fe:Mg:Na:Si:Zn=38:128:76:242:39,267:32 on a weight basis.

[0168] Specifically, in a casting machine equipped with feeding lines for a urethane-based prepolymer, a curing agent, an inert gas (N.sub.2), and a solid phase foaming agent, the urethane-based prepolymer prepared in the preparation example above was charged, and the curing agent of triethylenediamine was charged to the curing agent tank. The urethane-based prepolymer, the curing agent, and the solid phase foaming agent were fed at constant rates through the respective feeding lines to the mixing head and stirred at a rotation speed of 6,000 rpm.

[0169] In such an event, the molar equivalent ratio of the NCO group in the urethane-based prepolymer to the reactive groups in the curing agent was adjusted to 1:1, and the total feed rate was maintained at a rate of 10 kg/minute. The solid phase foaming agent was quantified in an amount of 2.0 parts by weight based on 100 parts by weight of the urethane-based prepolymer, curing agent, and solid foaming agent and charged. Nitrogen (N.sub.2), an inert gas, was fed at a rate of 1 liter/minute.

[0170] The mixed raw materials were injected into a mold (1,000 mm1,000 mm3 mm) and reacted to obtain a molded body in the form of a solid cake. The top and bottom of the molded body were each ground by a thickness of 0.5 mm and subjected to surface milling and groove forming processes to obtain a polishing layer having a thickness of 2 mm.

Preparation of a Polishing Pad

[0171] A support layer with a thickness of 1.1 mm was prepared in which a polyester fiber nonwoven fabric was impregnated with a polyurethane resin. The polishing layer and the support layer were combined using a hot melt adhesive to prepare a polishing pad (thickness: 3.3 mm) having a structure of a polishing layer, an adhesive layer, and a support layer.

Example 2

[0172] A polishing pad was prepared in the same manner as in Example 1, except that the composition ratio of elements of the solid phase foaming agent in Example 1 was changed to Ca:Fe:Mg:Na:Si:Zn=35:3:63:354:38,558:3 on a weight basis.

Example 3

[0173] A polishing pad was prepared in the same manner as in Example 1, except that the composition ratio of elements of the solid phase foaming agent in Example 1 was changed to Ca:Fe:Mg:Na:Si:Zn=111:2:50:383:43,917:15 on a weight basis.

Comparative Example 1

[0174] A polishing pad was prepared in the same manner as in Example 1, except that the composition ratio of elements of the solid phase foaming agent in Example 1 was changed to Ca:Fe:Mg:Na:Si:Zn=45:65:38:184:27,020:19 on a weight basis.

Comparative Example 2

[0175] A polishing pad was prepared in the same manner as in Example 1, except that the composition ratio of elements of the solid phase foaming agent in Example 1 was changed to Ca:Fe:Mg:Na:Si:Zn=21:64:27:189:27,500:5 on a weight basis.

Measurement of Surface Roughness

[0176] A three-dimensional image that represents the surface roughness profile of the polishing surface of each polishing pad was obtained using an optical surface roughness measuring device (Bruker, Contour X-100), and the three-dimensional image was analyzed using an image analysis program to measure surface roughness. Specifically, Sp, Sv, Sa, Spk, and Svk were measured as three-dimensional surface roughness values at the relief portion of the groove at a point with a radius of 40 mm from the center of the polishing pad. The measurement was carried out 5 times in total per polishing pad, and an average value of the measured values was obtained. The measurement conditions for surface roughness were set to USI measurement mode, an eyepiece magnification of 5, an objective lens magnification of 1.5, and a pixel size of 0.859 m, and the measurement was performed under scan options of a scan speed of 1, a back scan of 10 m, and a length of 80 m.

[0177] The contact area per unit area (1,080,000 m.sup.2) was measured by calculating the area of pixels located at a height of 50% of Sp in the 3D image, and the contact counts per unit area (1,080,000 m.sup.2) was measured by calculating the number of pixels. The contact area ratio (CAR) and the contact count ratio (CCR) were calculated using the above Equations 1 and 2 through the measured contact area per unit area and the contact counts per unit area, respectively.

[0178] The measurement results are shown in Tables 1 and 2 below.

TABLE-US-00001 TABLE 1 Contact count Contact area Contact area Contact counts ratio (CCR) (m.sup.2/1,080,000 ratio (CAR) (/1,080,000 (/1,000,000 m.sup.2) (%) m.sup.2) m.sup.2) Ex. 1 8,458 0.783 326 301 Ex. 2 10,087 0.934 502 465 Ex. 3 8,646 0.801 364 337 C. Ex. 1 8,172 0.757 184 170 C. Ex. 2 7,942 0.735 298 276

TABLE-US-00002 TABLE 2 Sa Sp Spk Sv Svk (m) (m) (m) (m) (m) Ex. 1 5.912 27.516 5.623 56.917 16.656 Ex. 2 6.054 28.120 5.496 55.632 16.885 Ex. 3 6.254 27.550 5.516 52.632 16.915 C. Ex. 1 6.018 31.547 6.057 55.229 17.537 C. Ex. 2 6.220 31.875 6.047 56.010 17.201

[0179] FIG. 5 is a 3D image of the polishing layer surface of the polishing pad of Example 1. FIG. 6 is a 3D image of the polishing layer surface of the polishing pad of Comparative Example 1. FIG. 7 is a 3D image of the polishing layer surface of the polishing pad of Comparative Example 2.

[0180] Referring to FIG. 5, peaks with red height are densely formed in the surface roughness extent of the polishing pad measured in the 3D image of Example 1, and the red area is relatively large. In contrast, referring to FIGS. 6 and 7, peaks with red height are sparsely formed in the surface roughness extent of the polishing pads measured in the 3D images of Comparative Examples 1 and 2, and the red area is relatively small. In addition, in the 3D images of Comparative Examples 1 and 2, the color distribution from red to blue is relatively wide, the surface roughness is not smooth, and the height deviation between peaks and valleys increases.

Measurement of Pore Distribution

[0181] Each polishing pad was cut into a square of 1 cm1 cm (thickness: 2 mm), and the cross-section was photographed using a scanning electron microscope (SEM) to obtain an image magnified 200 times. The diameter of the entire pores was measured from the obtained image using image analysis software. The volume of a pore with a radius of r was calculated as 4r.sup.3/3.

[0182] The pore volume distribution was obtained by listing the pores in order of increasing pore diameter. In the volume distribution of pores, D50 was measured as the pore diameter at a volume fraction of 50%, D10 was measured as the pore diameter at a volume fraction of 10%, and D90 was measured as the pore diameter at a volume fraction of 90%.

[0183] In addition, the average diameter Dn of the pores was measured by dividing the sum of the diameters of the measured pores by the total number of pores.

[0184] The measurement results are shown in Table 3 below.

TABLE-US-00003 TABLE 3 D10 D50 D90 Dn (m) (m) (m) (m) (D90 D10)/D50 D50/Dn Ex. 1 16.9 22.4 27.4 18.2 0.469 1.231 Ex. 2 14.9 20.4 25.4 18.9 0.514 1.079 Ex. 3 15.8 21.1 26.2 18.4 0.492 1.146 C. Ex. 1 20.9 33.3 47.9 23.3 0.810 1.429 C. Ex. 2 18.2 27.3 38 22.7 0.725 1.202

[0185] FIG. 8 is an SEM image of a cross-section of the polishing pad of Example 1. FIG. 9 is an SEM image of a cross-section of the polishing pad of Comparative Example 1. FIG. 10 is an SEM image of a cross-section of the polishing pad of Comparative Example 2.

[0186] Referring to FIGS. 8 to 10, pores with a small size are uniformly formed within the polishing pad of Example 1. In contrast, the polishing pads of Comparative Examples 1 and 2 had pores with a relatively large size, and the size deviation between the pores was also increased.

Test Example 1: Evaluation of Polishing Rate

[0187] A silicon wafer having a diameter of 300 mm with silicon oxide (SiO.sub.2) deposited by a CVD process was prepared. Each polishing pad was fixed onto the platen of CMP equipment, and the silicon wafer was set with the silicon oxide layer thereof facing downward. Then, a CMP process was carried out. The silicon oxide layer was polished under a polishing load of 4.0 psi while the platen was rotated at a speed of 150 rpm for 60 seconds and a calcined silica slurry was supplied onto the polishing pad at a rate of 250 ml/minute. Upon completion of the polishing, the silicon wafer was detached from the carrier, mounted in a spin dryer, washed with deionized water (DIW), and then dried with nitrogen for 15 seconds. The changes in the film thickness (polished thickness) of the silicon wafer before and after the polishing were measured using a spectral reflectometer type thickness measuring instrument (SI-F80R, Keyence).

[0188] Polishing rate (/minute)=average polished thickness of a silicon wafer ()/polishing time (minute)

Test Example 2: Evaluation of Surface Defects

[0189] After the polishing process in Test Example 1 was carried out, the residues, scratches, and chatter marks appearing on the surface of the wafer (monitoring wafer) upon the polishing were measured using wafer inspection equipment (AIT XP+, KLA Tencor).

TABLE-US-00004 TABLE 4 Polishing rate Surface defect (/min.) (count) Ex. 1 3,218 0 Ex. 2 2,907 1 Ex. 3 2,820 1 C. Ex. 1 3,129 2 C. Ex. 2 3,245 3

[0190] Referring to Table 4, the polishing pads of the Examples provided excellent polishing rates suitable for the CMP process, and the number of surface defects such as residues, scratches, and chatter marks appearing on the wafer surface after the polishing process using the polishing pads of the Examples was small.

[0191] In contrast, in the Comparative Examples, the polishing rates for the wafers were excessively increased, and the number of surface defects appearing after the polishing process was significantly increased relative to the Examples.

[0192] FIG. 11 is an image of the surface of the monitoring wafer of Comparative Example 1. FIG. 12 is an image of the surface of the monitoring wafer of Comparative Example 2. Referring to FIGS. 11 and 12, the polishing pads of Comparative Examples 1 and 2 caused surface defects such as scratches and chatter marks on the surface of the wafer during the polishing process.

TABLE-US-00005 [Reference Numeral of the Drawings] 100: polishing pad, 110: polishing surface, 200: semiconductor substrate, 310: platen, 320: polishing head, 330: nozzle, 340: polishing slurry