Polishing pad having excellent airtightness
An embodiment relates to a polishing pad which is used in a chemical mechanical planarization (CMP) process and has excellent airtightness, wherein the polishing pad is excellent in airtightness of a window opening and thus can prevent water leakage that may occur during a CMP process.
1. A polishing pad, which comprises:
a polishing layer having a first penetrating hole formed therein;
a support layer having a second penetrating hole formed in the region in which the first penetrating hole is formed;
a first adhesive layer interposed between the polishing layer and the support layer and having a third penetrating hole formed in the region in which the first penetrating hole is formed; and
a window inserted in the first penetrating hole and having a second adhesive layer adhered to a side of the window,
wherein the second penetrating hole and the third penetrating hole are aligned with each other, and
a part of the peripheral region of the second adhesive layer is adhered to the first adhesive layer,
wherein the light transmittance of the window is 60 to 80% and the refractive index thereof is 1.45 to 1.60, and
wherein the thickness of the second adhesive layer is 20 to 50 μm, the light transmittance of the second adhesive layer is 90 to 99% and the refractive index thereof is 1.4 to 1.6.
2. The polishing pad of claim 1 , wherein, when the ratio of the thickness of the window to the thickness of the second adhesive layer is 100:1, the difference in the light transmittance between the window and the second adhesive layer is 1 to 10%, and the difference in the refractive index between them is 0.01 to 0.1.
3. The polishing pad of claim 1 , wherein the first adhesive layer and the second adhesive layer are formed of a hot-melt adhesive having a melting point of 90 to 130° C.
4. The polishing pad of claim 1 , wherein the other side of the window is surface treated, and the surface-treated side has a surface roughness (Ra) of 2.0 to 4.0 μm.
5. A process for preparing a polishing pad, which comprises:
(1) providing a polishing layer having a first penetrating hole formed therein;
(2) providing a support layer opposite to the polishing layer;
(3) interposing a first adhesive layer between the polishing layer and the support layer, and adhering the polishing layer and the support layer to each other with the first adhesive layer;
(4) forming a third penetrating hole passing through the first adhesive layer in a predetermined region of the first adhesive layer and a second penetrating hole passing through the support layer in a predetermined region of the support layer, based on the first penetrating hole; and
(5) inserting a window having a second adhesive layer adhered to a side of the window into the first penetrating hole and adhering a part of the peripheral region of the second adhesive layer and the first adhesive layer,
wherein the light transmittance of the window is 60 to 80% and the refractive index thereof is 1.45 to 1.60, and
wherein the thickness of the second adhesive layer is 20 to 50 μm, the light transmittance of the second adhesive layer is 90 to 99% and the refractive index thereof is 1.4 to 1.6.
6. The process for preparing a polishing pad of claim 5 , wherein the third penetrating hole is formed in the region in which the first penetrating hole is formed,
the planar area of the third penetrating hole is smaller than the planar area of the first penetrating hole,
the second penetrating hole is formed in the region in which the first penetrating hole is formed, and
the planar area of the second penetrating hole is smaller than the planar area of the first penetrating hole.
7. The process for preparing a polishing pad of claim 5 , wherein the second penetrating hole and the third penetrating hole are formed, so that the second penetrating hole and the third penetrating hole correspond to each other.
8. The process for preparing a polishing pad of claim 5 , wherein the adhesion in the above step (5) of claim 5 is carried out by a part or the entire of each of the first adhesive layer and the second adhesive layer being melted and adhered to each other.
9. The process for preparing a polishing pad of claim 8 , wherein the first adhesive layer and the second adhesive layer are formed of a hot-melt adhesive having a melting point of 90 to 130° C., and
the adhesion in the above step (5) is carried out at 100 to 120° C.