E6700 Test Pumping Speeds
With regard to the pump down speeds of sputter coaters and vacuum evaporators. When assesing vacuum performance claims it should be noted that they tend to be measured under ideal conditions, and do not take into account or mention variables, such as:
Preconditioning of the system (how long and under what conditions was
the system pumped prior to the test).
Whether the system was vented to nitrogen gas.
Vacuum chamber ‘furniture’. Most ‘tests’ are conducted
with an empty vacuum chamber
Typical pump down times for the E6700 Bench Top Turbo Evaporator
The following test was carried out on a newly built E6700 Bench Top Turbo Evaporator
The E6700 was tested and pumped down for the first time on the day prior to the test and achieved the typical pressure of 3x10-6mbar overnight. This pressure will improve as the unit becomes vacuum conditioned and the cleaning solvents are fully desorbed. For the purposes of the pumping speed tests this should be taken as the base pressure.
The tests were carried out with the E6700 configured for a typical application as follows:
10" Pyrex belljar with standard chamber support jigging, sample platform and 1 x metal evaporation source. A calibrated Penning gauge was mounted in the chamber baseplate. The standard Edwards EXT250 turbo pump was backed with an Edwards RV5, 90l/min, rotary pump. The system was pumped overnight to achieve 3x10-6mbar base pressure.
The system was then vented to dry nitrogen for 1 minute before pumping and the following figures obtained:
Atm to 10-1mbar, 80 seconds
Atm to 10-2mbar, 90 seconds
Atm to 10-3mbar, 105 seconds
Atm to 10-4mbar, 120 seconds
Atm to 2 x 10-5mbar, 160 seconds
Atm to 10-5mbar, 400 seconds
It should be noted that the vacuum level required for typical TEM applications (carbon and metal evaporation) is somewhere between 10–4 and 10-5mbar.
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