TEOS oxide films deposited by LPCVD, were polished by CMP polisher. The variables of the polishing were the down load, the relative velocity, and the curvature of wafer carrier. The oxide thickness was measured pre-CMP and post-CMP, using an 89-points mapping with 15mm edge exclusion. The polishing rate is the thickness difference averaged over the 89 points and normalized by the polishing time. Each wafer was polished for 3 minutes.
From the relative velocity modeling, all points on the wafer would have the same relative velocity if the platen rotation speed equals that of the wafer carrier. Polishing rate fall-off decreased as the pad conditioning time and the interval time between each polishing increased. Our optimum condition was 10 minutes of pad conditioning and 1 hour of interval time.
For the flat wafer carrier, average polishing rate increased as the down load and the relative velocity increased. The polishing rate was more dependent to the down load than the relative velocity. Preston's coefficient calculated from Preston's equation was proportional to the applied down load. However, Preston's coefficient was constant for the relative velocity. Preston's coefficient according to the distance from wafer center became the constant function of the relative velocity. However, the slope of Preston's coefficient decreased as the down load increased.
For the 40㎛ convex wafer carrier, average polishing rate increased as the down load and the raelative velocity increased. The polishing rate on the down load was more effective than that of the relative velocity as the flat wafer carrier. Average polishing rate is higher than the that of flat wafer carrier as the distribution of the contact pressure between wafer and pad surface is the bell-type.
The uniformity of the polishing rate improved by the mechanical polishing effect with the different carriers as the down load and relative velocity increased. The uniformity with the 40㎛ convex wafer carrier was lower than that of the flat wafer carrier due to the distribution of the contact pressure.
