6. The system as claimed in claim 2 , wherein said first AVM server is used for retraining or tuning said set of VM models therein by using said set of first process data and said first actual measurement value to replace the oldest data in said sets of historical process data and said historical measurement value.
2. The system as claimed in claim 1 , wherein said first AVM server uses said set of VM models to conduct virtual metrology on said first workpiece.