These tests will quickly identify all of the problem areas involving these components and repairs can be made quickly. If the problem does not involve any of the gas handling components, the VDS quickly eliminates those subsystems from consideration and allows the focus of the investigation to move on to the problem system. This in-situ adjustment is many times all that is needed to get a system back into specification and processing wafers as quickly as possible . The need to remove components from the system with all of the time, personnel risk and risk of contamination that accompanies this work is eliminated. It is quite common for identical machines, running the same basic process on the same types of wafers, to require different process recipes to get similar results.
Every time service is performed the recipe has to be re-tweaked in order to get optimum results.
These recipe variations are necessary to accommodate the uncharacterized differences between machines. The VDS provides a common reference standard against which the performance of each process machine in the fab can be compared. The components on each machine can then be adjusted so that they perform in the same manner and the same recipe can be run on every identical machine. If adjustment is not possible, at least the reason for the recipe alteration can be documented and explained, so when the machine is changed during service or by simple aging, it can be quickly re characterized and the recipe adjusted accordingly. During process development and process research it is critical to know exactly how the machine is performing.