Specific Process Knowledge/Etch/DRIE-Pegasus/showerheadchange: Difference between revisions

The showerhead that distributes the process gasses inside the Pegasus plasma source was changed. In the old design, the showerhead had a number of holes intended to distribute the gas uniformly inside the plasma source. The passage through the holes had a flow resistance that would cause the gasses coming from the MFC in a Bosch process to get mixed up - in this way working against the separation of the etch and dep cycles.

In the new design, the gas flow resistance has been reduced by increasing the diameter holes in the showerhead instead. This has no impact on processes that have a continuous gas flow - i.e. processes that are not switched. However, for processes with several gas flows that switch on and off, the switching from one gas flow to another will be much more well defined. This has enabled us to run Bosch processes with shorter cycles times. Shorter cycles times means smaller scallops and hence lower roughness and better control. We have not seen any changes to the uniformity of the plasma nor any other side effect. The modification was also done on Pegasus 2 and 3 before we started using them.