Process simulation is more difficult in many ways than device simulation.
- The physics for process simulation is almost always newer and less well understood. For leading edge processes, the technique and or equipment is new, and often has been made to work with an imperfect knowledge of the science.
- It is also harder to get the input parameters from the manufacturing or development line, in a way that is accurate and understood. See the discussion of precision vs accuracy.
- Manufacturing variability adds a lot of uncertainty, and many of the distributions are not a neat gaussian.