Vibration Inertia Platofrms

The TRH cleanroom is a bay and chase design with the main fabrication equipment located in each of the bays of the cleanroom and the ancillary equipment located, for the most part, in the chases on either side of each bay. The cleanroom has a suspended floor, 1.5m above the concrete subfloor of the building, which comprises a lattice arrangement of 600 x 600 mm tiles inset within an aluminium frame and with 1.5m length aluminium legs at each corner that are bolted into the subfloor. Vibration sensitive equipment that will be sited on the suspended floor ranges from optical microscopes and other metrology equipment which will sit on passive anti vibration tables, to micron-scale mask aligners which require dedicated AV tables with active air legs and, most sensitive of all, nanometre-scale electron beam imaging and pattern writing equipment which require, as a minimum, air leg platforms and additional quiet islands located beneath the tools in the subfloor. Appendix C is a map of the cleanroom and shows the required different vibration criteria for different areas of the cleanroom. Vibration measurements of the floor were conducted by Colin Gordon and Associates and the raised access floor was shown to meet or exceed required vibration levels, see appendix D. It should be noted that the data recorded for the floor is representative of the cleanroom “as built”, i.e. the air-handling plant was running but no local sources of vibration such as pumps and chillers were in place or operational.A significant source of vibration within a cleanroom is from ancillary tools located within the chases, spatially separate from the main tools but connected via the continuous floor and connecting service pipework. Chief examples are pumps and chillers, but any equipment with moving parts is a potential source of vibration.Therefore, to maintain, as far as possible, the vibration levels as measured for the “as built” cleanroom, in particular in key critical areas as shown in appendix C, it is considered essential that passive anti-vibration inertia platforms are used to isolate ancillary tooling from the floor. The use of the inertia bases will act to lower the centre of gravity of the equipment to be isolated thus stabilising the equipment and the amplitude of movement of the equipment will also be reduced, thereby reducing the extent of the transmission of vibration across the floor to vibration sensitive tooling, and consequently reducing the risk of equipment within the cleanroom being unable to operate to its full potential due to vibration.