In most cases, the exact numerical solutions of intermediate steps during process simulation are not of pronounced interest to the process designer. Rather, overall trends of the system behavior should be modeled accurately to guide design decisions. To make the simulation results comparable to target specifications, only the very last stages of the simulation task - usually device simulation - need calibration. Figure 2.3 shows the principal mechanism for globally calibrating a sequence of tools.
Figure 2.3:
Global tool calibration. Combined parameter
settings of all tools together are used for fitting with measured
data during calibration.
All calibration data is subsumed in a single set of calibration data that encapsulates all previous - potentially unknown - calibration information.
In a more general approach, the complete sequence of tools can be replaced by a single model - a response surface model, table lookup, or other - that is calibrated for some sets of input parameter values. Figure 2.4 show the principle structure of global modeling and calibration.
