Polishing pad and method for preparing semiconductor device using the same
The present invention provides a polishing pad, a process for preparing the same, and a process for preparing a semiconductor device using the same. In the polishing pad, the surface zeta potential and its ratio of the polishing surface are controlled to specific ranges according to the type of polishing slurry, whereby it is possible to improve the characteristics of scratches and surface defects appearing on the surface of the semiconductor substrate and to further enhance the polishing rate.
1. A polishing pad after application of a polishing composition thereto and during polishing, comprising:
a polishing layer; and
a particulate layer comprising particles of a polishing composition being stably present on a polishing surface of the polishing layer,
wherein the polishing composition is selected from the group consisting of a first composition having a hydrogen ion concentration (pH) of 8 to 12, a second composition having a hydrogen ion concentration (pH) of 2 to 6, and a third composition including ceria particles and having a hydrogen ion concentration (pH) of 7.5 to 9.5,
wherein when polishing is carried out using the first composition of the polishing composition having the hydrogen ion concentration (pH) of 8 to 12, the polishing surface of the polishing layer has a first surface zeta potential (PZ1), which is a value associated with suspended particles in the first composition separated from the particulate layer by a first slipping plane present during the polishing and derived by the following Relationship 1 for the first composition;
when polishing is carried out using the second composition of the polishing composition having the hydrogen ion concentration (pH) of 2 to 6, the polishing surface of the polishing layer has a second surface zeta potential (PZ2), which is a value associated with the suspended particles in the second composition separated from the particulate layer by a second slipping plane present during the polishing and derived by the following Relationship 1 for the second composition; and
the first surface zeta potential (PZ1) and the second surface zeta potential (PZ2) satisfy the following Relationship 2:
Surface zeta potential=(−) zeta potential of the particulate layer+zeta potential of the polishing composition, [Relationship 1]
-
2
0
<
¯
PZ
1
PZ
2
≤
0
,
[
Relationship
2
]
wherein the polishing layer comprises a polyurethane foam having a porous structure comprising a plurality of pores wherein the number average diameter of the plurality of pores ranges from 10 μm to 40 μm and the polyurethane foam is a cured product of a composition comprising a urethane-based prepolymer, a curing agent, a silicone-based surfactant, and a foaming agent, and a content of an inorganic substance in the polishing layer ranges from 5 ppm to 500 ppm,
wherein a content of the curing agent ranges from 18 parts by weight to 27 parts by weight based on 100 parts by weight of the urethane-based prepolymer,
wherein a content of the silicone-based surfactant ranges from 0.2 part by weight to 2 parts by weight based on 100 parts by weight of the urethane-based prepolymer,
wherein the inorganic substance comprises at least one element selected from the group consisting of a silicon (Si) element, a phosphorus (P) element, and a calcium (Ca) element, and
wherein when polishing is carried out using the third composition of the polishing composition including the ceria particles and having the hydrogen ion concentration (pH) of 7.5 to 9.5, the polishing surface of the polishing layer has a third surface zeta potential (PZ3), which is a value of surface zeta potential of the polishing surface derived by the above Relationship 1 for the third composition, and
first surface zeta potential (PZ1) and the third surface zeta potential (PZ3) satisfy the following Relationship 3:
1
<
¯
PZ
1
PZ
3
≤
5.
[
Relationship
3
]
2. The polishing pad of claim 1 , wherein the first surface zeta potential (PZ1), the second surface zeta potential (PZ2), and the third surface zeta potential (PZ3) satisfy the following Relationship 4:
1.1
≤
PZ
1
×
PZ
2
PZ
3
≤
50.
[
Relationship
4
]
3. The polishing pad of claim 1 , wherein the first surface zeta potential (PZ1), the second surface zeta potential (PZ2), and the third surface zeta potential (PZ3) satisfy the following Relationship 5:
1
≤
(
PZ
2
-
PZ
1
)
(
PZ
2
-
PZ
3
)
≤
5.
[
Relationship
5
]
4. The polishing pad of claim 1 , wherein the zeta potential of the particulate layer for the first composition, IZ1, is +5 mV to about +30 mV, and
the zeta potential of the particulate layer for the second composition, IZ2, is −5 mV to about +15 mV.
5. The polishing pad of claim 1 , wherein PZ1 is-70 mV to −45 mV, and
PZ2 is +10 mV to +30 mV.
6. The polishing pad of claim 1 , wherein the first composition comprises silica particles having an average particle diameter of 130 nm to 160 nm, and
the second composition comprises silica particles having an average particle diameter of 30 nm to 50 nm.
7. The polishing pad of claim 6 , wherein the first composition has a zeta potential of −50 mV to −30 mV, and
the second composition has a zeta potential of +10 mV to +30 mV.
8. The polishing pad of claim 1 , wherein the zeta potential of the particulate layer for the first composition, IZ1, is +5 mV to about +30 mV, and
the zeta potential of the particulate layer for the third composition, IZ3, is −15 mV to about +10 mV.
9. The polishing pad of claim 1 , wherein PZ1 is-70 mV to −45 mV, and PZ3 is −45 mV to −30 mV.
10. The polishing pad of claim 1 , wherein the first composition comprises silica particles having an average particle diameter of 130 nm to 160 nm and has a zeta potential of −50 mV to −30 mV, and
the third composition comprises the ceria particles having an average particle diameter of 130 nm to 170 nm and has a zeta potential of −55 mV to −35 mV.
11. The polishing pad of claim 1 , wherein the urethane-based prepolymer has an isocyanate end group content (NCO %) of 5% by weight to 11% by weight.
12. The polishing pad of claim 1 , wherein the foaming agent comprises a solid phase foaming agent having an average particle diameter of 5 μm to 200 μm, a gas phase foaming agent, or a combination thereof.
13. The polishing pad of claim 1 , wherein when a first polishing rate of the polishing surface of the polishing layer for an oxide layer using the first composition is OR1,
when a second polishing rate of the polishing surface of the polishing layer for a tungsten layer using the second composition is WR2, and
when a third polishing rate of the polishing surface of the polishing layer for an oxide layer using the third composition is OR3,
OR1 is 2,750 Å/min to less than 2,955 Å/min, or
WR2 is 730 Å/min to 850 Å/min, or
OR3 is 2,200 Å/min to 2,955 Å/min.
14. A process for preparing a semiconductor device, which comprises:
providing a) a polishing pad comprising a polishing layer and b) a polishing composition providing a particulate layer comprising a layer of particles being stably present on a polishing surface of the polishing layer, wherein the polishing composition is selected from the group consisting of a first composition having a hydrogen ion concentration (pH) of 8 to 12, a second composition having a hydrogen ion concentration (pH) of 2 to 6, and a third composition including ceria particles and having a hydrogen ion concentration (pH) of 7.5 to 9.5; 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 object to be polished comprises an oxide layer, a tungsten layer, or a composite layer thereof,
when polishing is carried out using the first composition having the hydrogen ion concentration (pH) of 8 to 12, the polishing surface of the polishing layer has a first surface zeta potential (PZ1), associated with suspended particles in the first composition separated from the particulate layer by a first slipping plane present during the polishing and derived by the following Relationship 1 for the first composition;
when polishing is carried out using the second composition having the hydrogen ion concentration (pH) of 2 to 6, the polishing surface of the polishing layer has a second surface zeta potential (PZ2), associated with the suspended particles in the second composition separated from the particulate layer by a second slipping plane present during the polishing and derived by the following Relationship 1 for the second composition; and
the first surface zeta potential (PZ1) and the second surface zeta potential (PZ2) satisfy the following Relationship 2:
Surface zeta potential=(−) zeta potential of the particulate layer+zeta potential of the polishing composition, [Relationship 1]
-
2
0
<
¯
PZ
1
PZ
2
≤
0
,
[
Relationship
2
]
wherein the particulate layer is a layer formed by particles being present on the polishing surface,
wherein the polishing layer comprises a polyurethane foam having a porous structure comprising a plurality of pores wherein the number average diameter of the plurality of pores ranges from 10 μm to 40 μm and the polyurethane foam is a cured product of a composition comprising a urethane-based prepolymer, a curing agent, a silicone-based surfactant, and a foaming agent, and a content of an inorganic substance in the polishing layer ranges from 5 ppm to 500 ppm,
wherein a content of the curing agent ranges from 18 parts by weight to 27 parts by weight based on 100 parts by weight of the urethane-based prepolymer,
wherein a content of the silicone-based surfactant ranges from 0.2 part by weight to 2 parts by weight based on 100 parts by weight of the urethane-based prepolymer,
wherein the inorganic substance comprises at least one element selected from the group consisting of a silicon (Si) element, a phosphorus (P) element, and a calcium (Ca) element, and
wherein when polishing is carried out using the third composition including the ceria particles and having the hydrogen ion concentration (pH) of 7.5 to 9.5, the polishing surface of the polishing layer has a third surface zeta potential (PZ3), which is a value of surface zeta potential of the polishing surface derived by the above Relationship 1 for the third composition, and
the first surface zeta potential (PZ1) and the third surface zeta potential (PZ3) satisfy the following Relationship 3:
1
<
¯
PZ
1
PZ
3
≤
5.
[
Relationship
3
]
15. The process for preparing a semiconductor device of claim 14 , which further comprise, in the step of polishing the object to be polished, supplying any one of a slurry for polishing an oxide layer and a slurry for polishing a tungsten layer; or
sequentially supplying the slurry for polishing an oxide layer and the slurry for polishing a tungsten layer to the polishing surface.