Uniformity
- It is very important to have a uniform etch
rate across the wafer, or good within-wafer (WIW) uniformity, and high
reproducibility, or good wafer-to-wafer (WTW) uniformity.
- Uniformity is measured by measuring the
thickness at certain points before and after the etching, and finding the
etch rates at these points.
- If the etch rates at these points are x1,x2,x3,…,xN
here N is the total number of data points. The mean value of the
measurement is [3]
