Polishing pad and method for preparing semiconductor device using same
Embodiments relate to a polishing pad for use in a chemical mechanical planarization (CMP) process of semiconductor devices. The polishing pad may secure excellent polishing rate and within-wafer non-uniformity by controlling the physical properties such as initial load resistivity and compressive elasticity of the cushion layer and/or the laminate as defined by Equations 1 and 2: L R L ( % ) = T 1 L - T 2 L T 1 L - T 3 L × 100 [ Equation 1 ] C E L ( % ) = T 4 L - T 3 L T 2 L - T 3 L × 1 00. [ Equation 2 ]
1. A polishing pad, which comprises a laminate composed of a polishing layer, an adhesive layer, and a cushion layer,
wherein a hardness of the cushion layer is 68 to 74 Asker C,
wherein the polishing layer comprises a cured product of a composition comprising a urethane-based prepolymer, a curing agent, and a foaming agent, and satisfying at least one of the following (i), (ii), and (iii):
(i) the urethane-based prepolymer comprises a reaction product of at least one isocyanate compound and at least one polyol,
(ii) the curing agent is at least one selected from the group consisting of an amine compound and an alcohol compound, and
(iii) the foaming agent is at least one selected from the group consisting of a solid phase foaming agent and a gas phase foaming agent, and
wherein a initial load resistivity (LR L ) of the laminate defined by the following Equation 1 is 88% or more:
L
R
L
(
%
)
=
T
1
L
-
T
2
L
T
1
L
-
T
3
L
×
1
0
0
[
Equation
1
]
in Equation 1,
the T1 L is the thickness of the laminate in the no-load state,
the T2 L is the thickness of the laminate when a stress load of 30 kPa is maintained for 60 seconds from the no-load state, and
the T3 L is the thickness of the laminate when a stress load of 50 kPa is maintained for 60 seconds from the T2 L state.
2. The polishing pad of claim 1 , wherein the laminate has a compressive elasticity (CE L ), defined by the following Equation 2, of 50% or more:
C
E
L
(
%
)
=
T
4
L
-
T
3
L
T
2
L
-
T
3
L
×
1
0
0
[
Equation
2
]
in Equation 2,
the T4 L is the thickness of the laminate when the laminate is left for 60 seconds after the stress load has been released from the T3 L state, and a stress load of 30 kPa is then maintained for 60 seconds.
3. The polishing pad of claim 1 , wherein the thickness (T1 L ) of the laminate in the no-load state is 2.0 to 4.5 mm.
4. The polishing pad of claim 1 , wherein the polishing pad has an elastic modulus L of 100 to 160 kgf/cm 2 .
5. The polishing pad of claim 1 , wherein the polishing pad is capable of achieving a polishing rate of 3,840 Å/min or less for tungsten (W), and a within-wafer non-uniformity of 4.3% or less for tungsten (W),
wherein the polishing rate and the within-wafer non-uniformity are determined according to the following equations and measured under the following measurement conditions:
polishing rate(Å/min)=polished thickness(Å) of tungsten layer formed on silicon wafer/polishing time(minute)
measurement conditions of polishing rate: the tungsten layer formed on silicon wafer is polished by the polishing pad under a polishing load of 2.8 psi and rotation speed of 115 rpm for 30 seconds, and the difference in thickness of the silicon wafer before and after the polishing is measured using a contact sheet resistance measuring instrument with a 4-point probe; and
within-wafer non-uniformity(%)=(standard deviation of polished thickness(Å) of tungsten layer formed on silicon wafer/average polished thickness(Å) of tungsten layer formed on silicon wafer)×100(%)
measurement conditions of within-wafer non-uniformity: the tungsten layer formed on silicon wafer is polished by the polishing pad under a polishing load of 2.8 psi and rotation speed of 115 rpm for 1 minute, and in-film thickness at 98 points of the silicon wafer is measured.
6. The polishing pad of claim 1 , wherein the cushion layer comprises a nonwoven fabric or a suede.
7. The polishing pad of claim 1 , wherein the adhesive layer comprises a hot-melt adhesive.
8. A polishing pad, which comprises a polishing layer and a cushion layer,
wherein the hardness of the cushion layer is 69 to 80 Asker C,
wherein the polishing layer comprises a cured product of a composition comprising a urethane-based prepolymer, a curing agent, and a foaming agent, and satisfying at least one of the following (i), (ii), and (iii):
(i) the urethane-based prepolymer comprises a reaction product of at least one isocyanate compound and at least one polyol,
(ii) the curing agent is at least one selected from the group consisting of an amine compound and an alcohol compound, and
(iii) the foaming agent is at least one selected from the group consisting of a solid phase foaming agent and a gas phase foaming agent, and
wherein a initial load resistivity (LR C ) of the cushion layer defined by the following Equation 5 is 45% or more:
L
Rc
(
%
)
=
T
1
c
-
T
2
c
T
1
c
-
T
3
c
×
1
0
0
[
Equation
5
]
in Equation 5,
the T1 C is the thickness of the cushion layer in the no-load state,
the T2 C is the thickness of the cushion layer when a stress load of 30 kPa is maintained for 60 seconds from the no-load state, and
the T3 C is the thickness of the cushion layer when a stress load of 50 kPa is maintained for 60 seconds from the T2 C state.
9. The polishing pad of claim 8 , wherein a compressive elasticity (CES) of the cushion layer is less than 90% defined by the following Equation 6:
C
Ec
(
%
)
=
T
4
c
-
T
3
c
T
2
c
-
T
3
c
×
1
0
0
[
Equation
6
]
in Equation 6,
the T4 C is the thickness of the cushion layer when the cushion layer is left for 60 seconds after the stress load has been released from the T3 C state, and a stress load of 30 kPa (300 g/cm 2 ) is then maintained for 60 seconds.
10. The polishing pad of claim 8 , wherein the thickness (Tic) of the cushion layer in the no-load state is 0.5 to 2.5 mm.
11. The polishing pad of claim 8 , wherein the polishing pad has an elastic modulus L of 80 to 170 kgf/cm 2 .
12. The polishing pad of claim 8 , wherein the polishing pad is capable of achieving a polishing rate of 2,700 Å/min or less for silicon oxide (SiO x ), and a within-wafer non-uniformity of 5.5% or less for silicon oxide (SiO x ),
wherein, the polishing rate and the within-wafer non-uniformity are determined according to the following equations and measured under the following measurement conditions:
polishing rate(Å/min)=polished thickness(Å) of silicon oxide(SiO x ) layer formed on silicon wafer/polishing time(minute)
measurement conditions of polishing rate: the silicon oxide (SiO x ) layer formed on silicon wafer is polished by the polishing pad under a polishing load of 1.4 psi and rotation speed of 115 rpm for 60 seconds, and the difference in thickness of the silicon wafer before and after the polishing is measured using a spectral reflectometer thickness measuring instrument; and
within-wafer non-uniformity(%)=(standard deviation of polished thickness(Å) of silicon oxide(SiO x ) layer formed on silicon wafer/average polished thickness(Å) of silicon oxide(SiO x ) layer formed on silicon wafer)×100(%)
measurement conditions of within-wafer non-uniformity: the silicon oxide (SiO x ) layer formed on silicon wafer is polished by the polishing pad under a polishing load of 1.4 psi and rotation speed of 115 rpm for 60 seconds, and in-film thickness at 98 points of the silicon wafer is measured.
13. The polishing pad of claim 8 , wherein the polishing pad further comprises an adhesive layer between the polishing layer and the cushion layer, wherein the adhesive layer comprises a hot-melt adhesive.
14. A process for preparing a semiconductor device, which comprises:
preparing a polishing pad comprising a laminate composed of a polishing layer, an adhesive layer, and a cushion layer; and
relatively rotating the surface of the polishing layer of the polishing pad and the surface of a wafer while they are in contact with each other to polish the surface of the wafer,
wherein a initial load resistivity (LR L ) of the laminate defined by Equation 1 is 88% or more:
L
R
L
(
%
)
=
T
1
L
-
T
2
L
T
1
L
-
T
3
L
×
1
0
0
[
Equation
1
]
in Equation 1,
the T1 L is the thickness of the laminate in the no-load state,
the T2 L is the thickness of the laminate when a stress load of 30 kPa is maintained for 60 seconds from the no-load state, and
the T3 L is the thickness of the laminate when a stress load of 50 kPa is maintained for 60 seconds from the T2 L state;
wherein a hardness of the cushion layer is 68 to 74 Asker C; and
wherein the polishing layer comprises a cured product of a composition comprising a urethane-based prepolymer, a curing agent, and a foaming agent, and satisfying at least one of the following (i), (ii), and (iii):
(i) the urethane-based prepolymer comprises a reaction product of at least one isocyanate compound and at least one polyol,
(ii) the curing agent is at least one selected from the group consisting of an amine compound and an alcohol compound, and
(iii) the foaming agent is at least one selected from the group consisting of a solid phase foaming agent and a gas phase foaming agent.