Methods for processing semiconductor wafers having a polycrystalline finish
A method of processing a semiconductor wafer includes depositing a silicon layer on the semiconductor wafer. The silicon layer has a substantially uniform thickness. The silicon layer is polished to smooth the silicon layer such that the thickness is substantially uniform after polishing.
1. A method of processing a semiconductor wafer comprising:
depositing a silicon layer on the semiconductor wafer, the silicon layer having a substantially uniform thickness;
inspecting the semiconductor wafer to determine an initial wafer profile prior to polishing the silicon layer, the initial wafer profile having a shape;
dressing a polishing pad based on the shape of the initial wafer profile including dressing at least one of a center area and an edge area of a pad surface of the polishing pad based on the initial wafer profile of the semiconductor wafer, wherein the center area of the pad surface is dressed if the initial wafer profile of the semiconductor wafer is classified as dome-shaped and the edge area of the pad surface is dressed if the initial wafer profile of the semiconductor wafer is classified as dish-shaped; and
polishing the silicon layer using the polishing pad to smooth the silicon layer such that the thickness is substantially uniform after polishing and such that the semiconductor wafer has a polished shape that matches the shape of the initial wafer profile.
2. The method of claim 1 wherein the silicon layer is a polycrystalline silicon layer, the layer having a reduced roughness after polishing and the polycrystalline grain boundary being reduced by polishing.
3. The method of claim 1 wherein the edge area is dressed, the pad surface having a circular shape and the edge area extending radially between about 2.5 cm and about 5 cm from an outer edge of the polishing pad.
4. The method of claim 1 wherein the center area is dressed, the pad surface having a circular shape and the center area being spaced radially inward from an outer edge of the polishing pad between about 15 cm and about 20 cm.
5. The method of claim 1 further comprising applying slurry to an outer surface of the silicon layer, the slurry including abrasive particles and a base.
6. The method of claim 1 further comprising positioning the semiconductor wafer in a polishing apparatus, the polishing apparatus including the polishing pad.
7. The method of claim 1 further comprising inspecting the semiconductor wafer to determine a post-polishing wafer profile after removal of a portion of the silicon layer.
8. The method of claim 7 further comprising comparing the initial wafer profile to the post-polishing wafer profile to determine variations between the profiles.
9. The method of claim 8 further comprising dressing one of the center area and the edge area of the pad surface of the polishing pad based on the variations between the initial wafer and the post-polishing wafer profiles.
10. A method of processing a semiconductor wafer comprising:
depositing a silicon layer on the semiconductor wafer, the silicon layer including an inner surface facing the semiconductor wafer and an outer surface opposite the inner surface, the silicon layer having a first thickness defined between the inner surface and the outer surface, the first thickness being substantially uniform throughout the silicon layer;
inspecting the semiconductor wafer to determine an initial wafer profile prior to contacting the outer surface of the silicon layer with a pad surface;
classifying a shape of the initial wafer profile;
positioning the semiconductor wafer in a polishing apparatus, the polishing apparatus including a polishing pad having a pad surface, the pad surface defining a center area and an edge area;
dressing the center area of the pad surface if the initial wafer profile of the semiconductor wafer is classified as dome-shaped and the edge area of the pad surface if the initial wafer profile of the semiconductor wafer is classified as dish-shaped;
contacting the outer surface of the silicon layer with the pad surface;
applying slurry to the outer surface of the silicon layer; and
rotating the polishing pad while the pad surface is in contact with the outer surface of the silicon layer such that a portion of the silicon layer is removed to provide a smooth surface of the silicon layer, a second thickness being defined between the inner surface and the smooth surface, the second thickness being substantially uniform throughout the silicon layer.
11. The method of claim 10 wherein one of the center area and the edge area is dressed based on the initial wafer profile such that the dressed pad surface polishes the semiconductor wafer to have a polished shape that matches the shape of the initial wafer profile.
12. The method of claim 10 further comprising inspecting the semiconductor wafer to determine a post-polishing wafer profile after removal of a portion of the silicon layer.
13. The method of claim 12 further comprising comparing the initial wafer profile to the post-polishing wafer profile to determine variations between the profiles.
14. The method of claim 13 further comprising dressing one of the center area and the edge area of the pad surface based on the variations between the initial wafer and the post-polishing wafer profiles.
15. The method of claim 10 wherein the edge area is dressed, the pad surface having a circular shape and the edge area extending radially between about 2.5 cm and about 5 cm from an outer edge of the polishing pad.
16. The method of claim 10 wherein the center area is dressed, the pad surface having a circular shape and the center area being spaced radially inward from an outer edge of the polishing pad between about 15 cm and about 20 cm.