Polishing pad and method for preparing a semiconductor device using the same
The present invention relates to a polishing pad for use in a chemical mechanical planarization (CMP) process of semiconductors, to a process for preparing the same, and to a process for preparing a semiconductor device using the same. The polishing pad according to an embodiment can achieve low hardness by comprising a polishing layer formed using a curing agent of specific components. It is possible to enhance the mechanical properties of the polishing pad, as well as to improve the surface defects appearing on the surface of a semiconductor substrate, by controlling the surface roughness reduction rate and the recovery elasticity index of the polishing pad to specific ranges. It is also possible to further enhance the polishing rate.
1 . A polishing pad, which comprises a polishing layer, wherein the polishing layer comprises a cured product of a composition comprising a urethane-based prepolymer, a curing agent, and a foaming agent, the curing agent comprises a tertiary amine-based polyol containing an ether bond, and the polishing pad has a surface roughness reduction rate (RSk (%)) of less than 50% as represented by the following Equation 1 and a recovery elasticity resistance index (RERI) of 40 or less as represented by the following Equation 2:
RSk
(
%
)
=
Sk
1
-
Sk
2
Sk
1
⨯
100
[
Equation
1
]
in Equation 1, Sk 1 is the core roughness depth of the polishing pad before polishing, Sk 2 is the core roughness depth of the polishing pad measured after it polishes a silicon oxide layer of a semiconductor substrate for 60 seconds under the conditions of a carrier pressurization of 4.0 psi, a carrier rotation speed of 87 rpm, and a platen rotation speed of 93 rpm while a calcined ceria slurry is sprayed at a rate of 250 ml/minute, and Sk 1 and Sk 2 are each a value calculated from data measured by an optical surface roughness meter for the polishing pad before polishing and the polishing pad after polishing in accordance with the ISO 25178-2 standard,
Recovery
elasticity
resistance
index
(
RERI
)
=
Rsk
(
%
)
100
(
%
)
⨯
H
25
[
Equation
2
]
in Equation 2, RSk (%) is as defined in Equation 1 above, H 25 is the Shore D hardness of the polishing pad measured at 25° C., and the recovery elasticity resistance index (RERI) is a ratio between values excluding units,
wherein the polishing pad has a tensile strength of 10 N/mm 2 to 25 N/mm 2 , and an elongation of 80% to 320%.
2 . The polishing pad of claim 1 , wherein the difference (Sk 1 -Sk 2 ) between Sk 1 and Sk 2 is 15 μm or less.
3 . The polishing pad of claim 1 , wherein Sk 2 is 3 μm to 30 μm.
4 . The polishing pad of claim 1 , wherein H 25 is 40 Shore D to 60 Shore D.
5 . The polishing pad of claim 1 , wherein the tertiary amine-based polyol is represented by the following formula:
in the above formula, n is an integer of 1 to 10.
6 . The polishing pad of claim 1 , wherein the curing agent comprises a methyloxirane-containing 1,2-ethanediamine polymer compound.
7 . The polishing pad of claim 1 , wherein the curing agent further comprises an aromatic amine compound.
8 . The polishing pad of claim 7 , wherein the content of the tertiary amine-based polyol is the same as, or greater than, the content of the aromatic amine compound by weight.
9 . The polishing pad of claim 8 , wherein the mixing weight ratio of the tertiary amine-based polyol to the aromatic amine compound is 5:5 to 8:2.
10 . The polishing pad of claim 5 , wherein the tertiary amine-based polyol has a weight average molecular weight of 400 to 3,000 g/mole.
11 . The polishing pad of claim 7 , wherein the aromatic amine compound has a weight average molecular weight of 450 to 600 g/mole.
12 . The polishing pad of claim 7 , wherein the aromatic amine compound comprises at least one selected from the group consisting of diethyltoluenediamine; 3,5-dimethylthio-2,4-toluene diamine; 3,5-diethyltoluene-2,4-diamine; N,N′-bis-(sec-butylamino)-diphenylmethane; 4,4′-methylene-bis-(3-chloro-2,6-diethylaniline); polytetramethyleneoxide-di-p-aminobenzoate; N,N′-dialkyldiamino diphenyl methane; p,p′-methylene dianiline; m-phenylenediamine; 4,4′-methylene-bis-(2,6-diethylaniline); 4,4′-methylene-bis-(2,3-dichloroaniline); 4,4′-diamino-3,3′-diethyl-5,5′-dimethyl diphenylmethane; 2,2′,3,3′-tetrachlorodiamino diphenylmethane; trimethylene glycol di-p-aminobenzoate; 3,5-diamino-4-chloro benzoic acid-2-methylpropyl ester; bis(4-amino-2-chloro-3,5-diethylphenyl)methane; propanediol bis-p-aminobenzoate; butyl diaminochlorobenzoate; methylene bis-methylanthranilate; chloro diethyltoluenediamine; methylene bis-o-ethylaniline; and isomers thereof.
13 . The polishing pad of claim 1 , wherein the foaming agent comprises a solid phase foaming agent comprising unexpanded particles.
14 . The polishing pad of claim 1 , wherein the urethane-based prepolymer has a content of isocyanate terminal groups (NCO %) of 9% by weight to 12% by weight.
15 . The polishing pad of claim 1 , wherein the composition comprises the curing agent in an amount of 18 parts by weight to 27 parts by weight based on 100 parts by weight of the urethane-based prepolymer.
16 . The polishing pad of claim 1 , wherein the curing agent does not comprise 4,4′-methylenebis(2-chloroaniline) (MOCA).
17 . The polishing pad of claim 1 , having a polishing rate for an oxide layer of 1,600 Å/minute to 3,300 Å/minute.
18 . A process for preparing a polishing pad, which comprises:
mixing a urethane-based prepolymer, a curing agent, and a foaming agent to prepare a composition for preparing a polishing layer; and
injecting the composition for preparing a polishing layer into a mold and curing it to obtain a polishing pad comprising a polishing layer,
wherein the curing agent comprises a tertiary amine-based polyol containing an ether bond, and the polishing pad has a surface roughness reduction rate (RSk (%)) of less than 50% as represented by the following Equation 1 and a recovery elasticity resistance index (RERI) of 40 or less as represented by the following Equation 2:
RSk
(
%
)
=
Sk
1
-
Sk
2
Sk
1
⨯
100
[
Equation
1
]
in Equation 1, Sk 1 is the core roughness depth of the polishing pad before polishing, Sk 2 is the core roughness depth of the polishing pad measured after it polishes a silicon oxide layer of a semiconductor substrate for 60 seconds under the conditions of a carrier pressurization of 4.0 psi, a carrier rotation speed of 87 rpm, and a platen rotation speed of 93 rpm while a calcined ceria slurry is sprayed at a rate of 250 ml/minute, and Sk 1 and Sk 2 are each a value calculated from data measured by an optical surface roughness meter for the polishing pad before polishing and the polishing pad after polishing in accordance with the ISO 25178-2 standard,
[Equation 2]
Recovery
elasticity
resistance
index
(
RERI
)
=
Rsk
(
%
)
100
(
%
)
⨯
H
25
[
Equation
2
]
in Equation 2, RSk (%) is as defined in Equation 1 above, H 25 is the Shore D hardness of the polishing pad measured at 25° C., and the recovery elasticity resistance index (RERI) is a ratio between values excluding units,
wherein the polishing pad has a tensile strength of 10 N/mm 2 to 25 N/mm 2 , and an elongation of 80% to 320%.
19 . The process for preparing a polishing pad of claim 18 , wherein the foaming agent comprises an unexpanded solid phase foaming agent, and, when the composition for preparing a polishing layer is injected into the mold, nitrogen (N 2 ) gas is not be injected.
20 . A process for preparing a semiconductor device, which comprises:
providing a polishing pad comprising a polishing layer; and
relatively rotating the polishing surface of the polishing layer and the surface of an object to be polished while they are in contact with each other to polish the object to be polished,
wherein the polishing pad comprises a polishing layer comprising a cured product of a composition comprising a urethane-based prepolymer, a curing agent, and a foaming agent, the curing agent comprises a tertiary amine-based polyol containing an ether bond, and the polishing pad has a surface roughness reduction rate (RSk (%)) of less than 50% as represented by the following Equation 1 and a recovery elasticity resistance index (RERI) of 40 or less as represented by the following Equation 2:
RSk
(
%
)
=
Sk
1
-
Sk
2
Sk
1
⨯
100
[
Equation
1
]
in Equation 1, Sk 1 is the core roughness depth of the polishing pad before polishing, Sk 2 is the core roughness depth of the polishing pad measured after it polishes a silicon oxide layer of a semiconductor substrate for 60 seconds under the conditions of a carrier pressurization of 4.0 psi, a carrier rotation speed of 87 rpm, and a platen rotation speed of 93 rpm while a calcined ceria slurry is sprayed at a rate of 250 ml/minute, and Sk 1 and Sk 2 are each a value calculated from data measured by an optical surface roughness meter for the polishing pad before polishing and the polishing pad after polishing in accordance with the ISO 25178-2 standard,
Recovery
elasticity
resistance
index
(
RERI
)
=
Rsk
(
%
)
100
(
%
)
⨯
H
25
[
Equation
2
]
in Equation 2, RSk (%) is as defined in Equation 1 above, H 25 is the Shore D hardness of the polishing pad measured at 25° C., and the recovery elasticity resistance index (RERI) is a ratio between values excluding units,
wherein the polishing pad has a tensile strength of 10 N/mm 2 to 25 N/mm 2 , and an elongation of 80% to 320%.