Hazard Prevention Professionals Inc.

Hydrocarbon oil : Oxygen

The Oxygen will mix with the hydrocarbon oil to form Hydrogen peroxide, Carboxylic Acid and Polymeric Esters. This will cause the oil to breakdown into sludge and resin will for into the pump. The resin is insoluble in oil and strongly adherent to metal surfaces. As a result the vane will stick and the oil filter will get plugged. Changing the oil frequentlly will help but will not remove the resin that has adhered to the metal surfaces inside the pump.

Hydrocarbon oil is not recommended for pumping concentrations of oxygen greater than that found in atmosphere due to the explosion potential when mixing oilvapours and oxygen.

Lewis Acids

Lewis Acids are electron pair acceptors such as BF3, BCL3,AlCl3.

The lewis acid will quickly polymerize a hydrocarbon oil and turn it into a polymer. It will also cause the PFPE oil molecules to break at the ether link into toxic fragments.The PFPE oil will then loose it's lubrication properties and will have to be sent out to get reclaimed where it will be filtered and possibly refluorinated.

Special care must be used when dealing with gases that causes Lewis Acids to form. The oil should be PFPE and filtered using Alumina filter to remove the acid in the oil. Periodic test should be performed on the oil to determine if the oil has become acidic. If the oil is acidc the oil should be sent out for reclaim and the oil in the pump and filter should be change to prevent any damage to the pump. The other alternative is to use Dry vacuum pump where the oil never comes in contact with the process gases.

Oil Backstreaming

The main cause of oil backstreaming happens when the pressure at the pump is the same as the pressure at the process chamber. When there is nolonger any flow of gas molecule the oil molecules inside the pump then becomes free to move around in the entire area that is under vacuum. To avoid this a nitrogen purge should be installed at the inlet of the vacuum pump.

Safety Around Contaminated Oil

Special care should always be used when performing oil change. Oil vapour will always be present when changing hot vacuum pump oil. The technician performing the task should be wearing a full face mask respirator with a Volatile Organic Compound cartridge. The technician shouls also be wearing Neopreme gloves in case he comes in contact with the used oil.

Most people make the mistake of not treating waste oil like a chemical because they know that the equipment that they are using doesn't have any toxic gases. What they don't realize is that what goes into the equipment is always what comes out. Some inert gases are mixed with other inert gases to form a plasmawith RF tremove the substrate.

For example if you take CF4 a widelly used Freon in Semiconductor manufacturing and expose it to RF. You will find that the Hydrocarbon oil has traces of Carbon, Fluoride and Hydrogen Fluoride

The same is true for: Boron Trichloride will form HCL and Aluminum Trichloride ( aluminum etching)