These findings are in regard to 22 nm circuitry, which is currently in design for 2011-2012. For this circuitry we will be concerned with all particles >10nm.
There are some new issues that may reveal a need for cleaner, torque elimination metal face seal fittings.
One new challenge is that with these extremely small geometries, the process gas flows have been reduced to a point where some filters have had to be removed. The filters are removed because the PDL (Pulsed Deposition Layer) processes have very short pulsed bursts of gas and a filter in these processes disallow this short pulse to be accurately controlled.
Filters also have large gas volumes that make it problematic to quickly change gas blends for process needs. Ballistic particle penetration for filters of current design is an issue that stems from having order of magnitude pressure differentials across the filters. These are just a few of the issues related to gas system design for the future nodes.
In a publication by Unit Instruments and Lam Research it was shown that the current “VCR type” fittings produce particles in the 1.0 to 0.1 micron size range. These particles are more of a concern now that the filters are no longer in place on the gas delivery system before the chamber. Torque elimination fittings do not produce particles when mate/demated.
Another concern is fitting loosening due to shock & vibration during transportation and installation. In a study by AMAT conducted at Quanta Labs, two out of three “VCR type” fittings failed to pass Mil Std 810E which simulated normal transportation vibration. The higher leak rates in these “VCR type” fittings loosened by shock & vibration are a continual source of micro amounts of moisture or oxygen. This fits a pattern where certain pieces of identical process equipment have a history of not operating optimally.
Torque elimination fittings are flight qualified and are not loosened by shock & vibration. Leak checks at tool install do not normally catch the leaking fittings because the installation specification is usually substantially less stringent than the manufacturing specification due to the difficulty of leak checking a complete tool gas distribution manifold in the Fab.