Polishing pad comprising window similar in hardness to polishing layer
Embodiments relate to a polishing pad, which comprises a window having a hardness similar to that of its polishing layer. Since the polishing pad comprises a window having a hardness and a polishing rate similar to those of its polishing layer, it can produce an effect of preventing scratches on a wafer during a CMP process. In addition, the polishing layer and the window of the polishing pad have a similar rate of change in hardness with respect to temperature, so that they can maintain a similar hardness despite a change in temperature during the CMP process.
1. A polishing pad, which comprises:
a polishing layer having a penetrating hole; and
a window inserted in the penetrating hole,
wherein the difference in wet hardness between the window and the polishing layer is 0.1 Shore D to 12 Shore D, and the wet hardness is a surface hardness measured upon immersion in water for 30 minutes,
wherein the polishing layer is formed from a polishing layer composition that comprises a first urethane-based prepolymer, a curing agent, and a foaming agent; and the window is formed from a window composition that comprises a second urethane-based prepolymer and a curing agent, wherein the difference in the content of the unreacted isocyanate groups (NCO) between the first urethane-based prepolymer and the second urethane-based prepolymer is 0.4% by weight to 1.0% by weight, and
wherein the content of the unreacted isocyanate group (NCO) in the first urethane-based prepolymer is 7.5% by weight to 9.5% by weight; and the content of the unreacted isocyanate group (NCO) in the second urethane-based prepolymer is 8.1% by weight to 9.0% by weight.
2. The polishing pad of claim 1 , wherein the window has a rate of reduction in wet hardness of 20 Shore D/° C. to 25 Shore D/° C. in the temperature range of 30° C. to 70° C., and the rate of reduction in wet hardness is calculated by the following Equation 1:
Rate of reduction in wet hardness=(wet hardness at 30° C.−wet hardness at 70° C.)×100/(70° C.−30° C.). [Equation 1]
3. The polishing pad of claim 1 , wherein the difference in the rate of reduction in wet hardness between the window and the polishing layer is 1 Shore D/° C. to 5 Shore D/° C. in the temperature range of 30° C. to 70° C., and the rate of reduction in wet hardness is calculated by the following Equation 1:
Rate of reduction in wet hardness=(wet hardness at 30° C.−wet hardness at 70° C.)×100/(70° C.−30° C.). [Equation 1]
4. The polishing pad of claim 1 , wherein the deviation in hardness between the window and the polishing layer is 0.1% to 13% in the temperature range of 30° C. to 70° C., and the deviation in hardness is calculated by the following Equation 2:
Deviation in hardness=(wet hardness of a window−wet hardness of a polishing layer)×100/(wet hardness of a polishing layer). [Equation 2]
5. The polishing pad of claim 1 , wherein the difference in wet hardness between the window and the polishing layer is 0.1 Shore D to 10 Shore D.
6. The polishing pad of claim 1 , wherein the polishing layer has a wet hardness of 45 Shore D to 65 Shore D in the temperature range of 30° C. to 70° C.; and the window has a wet hardness of 50 Shore D to 75 Shore D in the temperature range of 30° C. to 70° C.
7. The polishing pad of claim 1 , wherein the wear rate of the polishing layer is 80% to 100% of the wear rate of the window.