Graham Johnson, EMEA Product Manager for Parker Veriflo Ultra High Purity Fluoropolymer Valves, looks at the benefits of two point seal valves for semiconductor applications.
The corrosive nature of high concentration acids and bases, clear chemistries and slurries used in semiconductor applications mean that pneumatic valves specified for these applications need to be particularly robust.
When a single seal is used, it can lead to a limited lifespan of the valve, due to rapid deterioration of the premier seal faces caused by constantly being exposed to chemicals and slurries.
It was against this background that Parker developed its 22 Series valves which feature two point seals. It is a labyrinth type seal with one seal inside the other seal.
It has been proven that having a back-up seal improves the integrity of the valve and therefore its lifespan. Rigorous in-house laboratory tests showed that the 2 point seal when slurry tested could withstand over 2.1 million cycles. It was also tested with hydrochloric and sulphuric acid and achieved over 2.1 million cycles. With clean chemicals or water, it was found to deliver over 3 million cycles. It also underwent rigorous temperature cycle tests.
Fig 1. Parker's Ultra High Purity Fluoropolymer Valve, 22 Series.
As a result of these tests, two-point seals were found to deliver greater seal integrity over the entire cycle life of the valve in slurry applications. Parker currently has a patent pending for a dual point seal, as this is an industry first.
Fig 2. Patent-pending two-point seal. Finite Element Analysis.
With increased safety requirements within a semiconductor fab, lock-out tag-out (LOTO) requirements are needed for system work. This feature is not widely available in the industry for any size of valve. The 22 Series is an industry first in offering this feature as standard on its valves. The designs are unique in preventing the misapplication of the LOTO feature, by not allowing the valve to be locked in the open position.
Fig 3. Parker's unique LOTO feature, Ultra High Purity Fluoropolymer Valve, 22 Series.
In semiconductor applications, it is also important that a valve is able to deliver full flow within a compact design, therefore achieving optimum flow-through and space efficiency. The 22 Series manual and pneumatic valves were designed to achieve a better flow characteristic throughout its design.
The semiconductor industry continues to seek valves which offer long cycle life in acids. Valves that are able to offer extended cycle life and design optimisation for slurry applications are an appealing choice for Chemical Mechanical Planarization (CMP) equipment because of their durability and performance.
Graham Johnson is product manager, downstream analytical, Parker Hannifin, Instrumentation Products Division Europe