Polishing pad and method of fabricating semiconductor device using the same
The present disclosure relates to an endpoint detection window of a polishing pad for use in a polishing process. The polishing pad may prevent an error in detection of the endpoint of the polishing process by preventing a difference in endpoint detection performance from occurring due to a difference in the wavelength of a laser between polishing apparatuses. The present disclosure may also provide a method of fabricating a semiconductor device using the polishing pad.
1. A polishing pad comprising a polishing layer and an endpoint detection window,
wherein the window comprises a cured product obtained by curing a window composition containing a urethane-based prepolymer and a curing agent, and the urethane-based prepolymer has an unreacted isocyanate group (NCO) content (%) of 8 to 10%,
wherein an isocyanate compound for producing the urethane-based prepolymer includes an aromatic diisocyanate compound,
wherein the curing agent is 4,4′-methylenebis(2-chloroaniline) (MOCA),
wherein the content of the curing agent is 15 parts by weight to about 28 parts by weight, based on 100 parts by weight of the urethane-based prepolymer,
wherein the window has an absorbance change uniformity (ACU) of 1.5 to 2.5 as calculated by the following Equation 1,
wherein the window has an absorbance difference (AD) of 0.0004 to 0.0008 calculated by the following Equation 2,
ACU
=
Ax
+
Ay
Az
[
Equation
1
]
wherein:
Ax is an absorbance of the window, measured with light having a wavelength of 550 nm,
Ay is an absorbance of the window, measured with light having a wavelength of 750 nm, and
Az is an absorbance of the window, measured with light having a wavelength of 650 nm,
and
AD
=
❘
"\[LeftBracketingBar]"
Ax
-
Ay
x
-
y
❘
"\[RightBracketingBar]"
.
[
Equation
2
]
2. The polishing pad of claim 1 , wherein the window has a second absorbance change uniformity (ACU 2 ) of 2 to 3.5 calculated by the following Equation 3,
ACU2=( Aa+Ab )/ Ac [Equation 3]
wherein:
Aa is an absorbance of the window, measured with light having a wavelength of 400 nm,
Ab is an absorbance of the window, measured with light having a wavelength of 800 nm, and
Ac is an absorbance of the window, measured with light having a wavelength of 600 nm.
3. The polishing pad of claim 1 , wherein the window has a second absorbance change uniformity (ACU 2 ) of 1.5 to 2.5 calculated by the following Equation 3,
ACU2=( Aa+Ab )/ Ac [Equation 3]
wherein:
Aa is an absorbance of the window, measured with light having a wavelength of 600 nm,
Ab is an absorbance of the window, measured with light having a wavelength of 750 nm, and
Ac is an absorbance of the window, measured with light having a wavelength of 675 nm.
4. The polishing pad of claim 1 , wherein when a plurality of absorbances of the window is measured by irradiating the window with light having a wavelength of 400 nm to 800 nm, an average of the plurality of absorbances is 0.61 to 0.80.
5. A method for producing a polishing pad, the method comprising steps of:
preparing a urethane-based prepolymer composition;
preparing a composition for producing a window containing the prepolymer composition and a curing agent;
producing the window by curing the composition for producing a window;
preparing a prepolymer composition;
preparing a composition for producing a polishing layer containing the prepolymer composition, a foaming agent and a curing agent;
producing a polishing layer by curing the composition for producing a polishing layer, and
forming a through-hole in the polishing layer and inserting and bonding the produced window into and to the through-hole,
wherein the urethane-based prepolymer has an unreacted isocyanate group (NCO) content (%) of 8 to 10%,
wherein the curing agent is 4,4′-methylenebis(2-chloroaniline) (MOCA),
wherein an isocyanate compound for producing the urethane-based prepolymer includes an aromatic diisocyanate compound,
wherein the content of the curing agent is 15 parts by weight to about 28 parts by weight, based on 100 parts by weight of the urethane-based prepolymer,
wherein the window has an absorbance change uniformity (ACU) of 1.5 to 2.5 as calculated by the following Equation 1,
wherein the window has an absorbance difference (AD) of 0.0004 to 0.0008 calculated by the following Equation 2:
ACU
=
Ax
+
Ay
Az
[
Equation
1
]
wherein:
Ax is an absorbance of the window, measured with light having a wavelength of 550 nm,
Ay is an absorbance of the window, measured with light having a wavelength of 750 nm, and
Az is an absorbance of the window, measured with light having a wavelength of 650 nm,
and
AD
=
❘
"\[LeftBracketingBar]"
Ax
-
Ay
x
-
y
❘
"\[RightBracketingBar]"
.
[
Equation
2
]
6. The method of claim 5 , wherein the window has a second absorbance change uniformity (ACU 2 ) of 2 to 3.5 calculated by the following Equation 3,
ACU2=( Aa+Ab )/ Ac [Equation 3]
wherein:
Aa is an absorbance of the window, measured with light having a wavelength of 400 nm,
Ab is an absorbance of the window, measured with light having a wavelength of 800 nm, and
Ac is an absorbance of the window, measured with light having a wavelength of 600 nm.
7. The method of claim 5 , wherein the window has a second absorbance change uniformity (ACU 2 ) of 1.5 to 2.5 calculated by the following Equation 3,
ACU2=( Aa+Ab )/ Ac [Equation 3]
wherein:
Aa is an absorbance of the window, measured with light having a wavelength of 600 nm,
Ab is an absorbance of the window, measured with light having a wavelength of 750 nm, and
Ac is an absorbance of the window, measured with light having a wavelength of 675 nm.
8. The method of claim 5 , wherein when a plurality of absorbances of the window is measured by irradiating the window with light having a wavelength of 400 nm to 800 nm, an average of the plurality of absorbances is 0.61 to 0.80.
9. A method for fabricating a semiconductor device, the method comprising steps of:
1) providing a polishing pad comprising a polishing layer and an endpoint detection window;
2) performing a polishing process on a semiconductor substrate while allowing the semiconductor substrate and the polishing layer to rotate relative to each other in a state in which a polishing-target surface of the semiconductor substrate is in contact with a polishing surface of the polishing layer; and
3) detecting a thickness of the semiconductor substrate and detecting an endpoint of the polishing process, through the window of the polishing pad,
wherein the window comprises a cured product obtained by curing a window composition containing a urethane-based prepolymer and a curing agent, and the urethane-based prepolymer has an unreacted isocyanate group (NCO) content (%) of 8 to 10%,
wherein the curing agent is 4,4′-methylenebis(2-chloroaniline) (MOCA),
wherein an isocyanate compound for producing the urethane-based prepolymer includes an aromatic diisocyanate compound,
wherein the content of the curing agent is 15 parts by weight to about 28 parts by weight, based on 100 parts by weight of the urethane-based prepolymer,
wherein the window has an absorbance change uniformity (ACU) of 1.5 to 2.5 as calculated by the following Equation 1,
wherein the window has an absorbance difference (AD) of 0.0004 to 0.0008 calculated by the following Equation 2:
ACU
=
Ax
+
Ay
Az
[
Equation
1
]
wherein:
Ax is an absorbance of the window, measured with light having a wavelength of 550 nm,
Ay is the absorbance of the window, measured with light having a wavelength of 750 nm, and
Az is the absorbance of the window, measured with light having a wavelength of 650 nm,
and
AD
=
❘
"\[LeftBracketingBar]"
Ax
-
Ay
x
-
y
❘
"\[RightBracketingBar]"
.
[
Equation
2
]
10. The method of claim 9 , wherein step 3) comprises detecting the endpoint of the polishing process through the window by irradiating the polishing-target surface with light having any one wavelength within another wavelength range of 550 nm to 750 nm and detecting light reflected from the polishing-target surface.
11. The method of claim 9 , wherein step 3) comprises detecting the endpoint of the polishing process through the window by irradiating the polishing-target surface with light having any one wavelength within another wavelength range of 400 nm to 800 nm and detecting light reflected from the polishing-target surface, and
the window has a second absorbance change uniformity (ACU 2 ) of 2 to 3.5 calculated by the following Equation 3,
ACU2=( Aa+Ab )/ Ac [Equation 3]
wherein:
Aa is an absorbance of the window, measured with light having a wavelength of 400 nm,
Ab is an absorbance of the window, measured with light having a wavelength of 800 nm, and
Ac is an absorbance of the window, measured with light having a wavelength of 600 nm.
12. The method of claim 9 , wherein step 3) comprises detecting the endpoint of the polishing process through the window by irradiating the polishing-target surface with light having any one wavelength within another wavelength range of 600 nm to 750 nm and detecting light reflected from the polishing-target surface, and
the window has a second absorbance change uniformity (ACU 2 ) of 1.5 to 2.5 calculated by the following Equation 3,
ACU2=( Aa+Ab )/ Ac [Equation 3]
wherein:
Aa is an absorbance of the window, measured with light having a wavelength of 600 nm,
Ab is an absorbance of the window, measured with light having a wavelength of 750 nm, and
Ac is an absorbance of the window, measured with light having a wavelength of 675 nm.
13. The method of claim 9 , wherein when a plurality of absorbances of the window is measured by irradiating the window with light having a wavelength of 400 nm to 800 nm, an average of the plurality of absorbances is 0.61 to 0.80.
14. The method of claim 9 , wherein
the semiconductor substrate comprises a silicon dioxide (SiO 2 ) layer,
the polishing-target surface is a surface of the silicon dioxide (SiO 2 ) layer, and
the silicon dioxide (SiO 2 ) layer has an average removal rate of 2,500 Å/min to 4,000 Å/min.
15. The method of claim 9 , wherein the polishing pad has a cutting rate of 35 to 55 μm/hr.