Improved Pump Down Time with Evactron® Turbo Plasma™ Cleaning

Abstract

.As the need for higher throughput of samples in Scanning Electron Microscopes (SEMs) and Focused Ion Beam (FIB) systems increases, so does the necessity to shorten pump down times between loading samples. Industry demands SEM/FIB systems to be operational 24/7 and ideally maintained in pristine condition with uncompromised image quality. Frequent venting of the SEMs or FIBs to load samples introduces moisture and contamination into the vacuum chamber, leading to much longer pump down times and decreased efficiency.The new Evactron Turbo Plasma™ De-Contaminators remove hydrocarbon (HC) contamination [1] from SEMs, FIBs and other analytical tools using a gentle, down-stream plasma afterglow process. At turbo pump pressures, Evactron cleaning becomes faster and spreads throughout the chamber. This is due to longer mean-free-paths that cause less recombination of oxygen radicals in the required three body collisions and decreased scattering to chamber walls [1]. In most cases, short plasma cleaning cycles are sufficient to remove contamination and significantly shorten pump down time, allowing for high throughput of sample processing and analysis.To demonstrate the effect of Evactron Turbo Plasma Cleaning on pump down time and HC contamination removal, the study was done using an EP model Evactron Plasma DeContaminator on a large, highly oil-contaminated 50 L vacuum chamber equipped with a 450 L/sec turbo molecular pump, 14 CFM scroll pump, MKS 972B dual range pressure gauge and a residual gas analyzer (RGA). Evactron Cleaning was done at 20 Watts for 30 minutes. RGA spectra ( Fig. 1 and 2) and pump down curves (Fig. 3) were obtained before and after contamination and plasma cleaning in order to demonstrate the effects of Evactron Turbo Plasma cleaning on pump down time and hydrocarbon removal. The chamber is considered to be in pristine condition when the HC peaks on the RGA spectrum were less than a partial pressure of 2 X 1 -10 Torr.The length of the pump down time shows dependence on hydrocarbon contamination levels [2] in SEMs and FIBs. Therefore, this time could be used as an indicator of the cleanliness of the vacuum system. The data shows that Evactron plasma cleaners significantly reduce both the pump down time of the SEMs and FIBs as well as hydrocarbon contamination, and thus help increase sample processing throughput without compromising the quality of analysis.Typically, vacuum chambers can be cleaned with the Turbo Plasma Cleaning process at turbo molecular pressures of 10 -2 to 10 -3 Torr with typical cleaning times of 2 -10 minutes to maintain pristine conditions, and returning to typical operating pressures in < 20 minutes. Current users of Evactron Plasma Cleaners report significant reduction in pump down time after using Evactron De-Contaminators as well as easier maintenance of the pristine state of cleanliness of their SEMs and FIBs. A more detailed analysis and data from multiple experiments will be presented.

The Benefits of Plasma Cleaning for TKD/EBSD Analysis

“…The oxygen radicals combine with surface hydrocarbons to form gaseous phases which are removed by the pumping system. The benefits of plasma cleaning include faster pumpdown times [3], improved image quality of serial block-face SEM volumetric sets [4], prevention of hydrocarbon deposition during imaging [5] and no damage to EDS detectors or xray windows due to oxygen radical generation [6].…”

20th Anniversary of Evactron® Plasma Cleaners for SEMs and FIBs

“…Chamber residue on surfaces, components, and traces residing on specimens are all sources of hydrocarbons that are polymerized by the electron beam on scanned areas, causing image blurring and loss of resolution. Periodic Evactron plasma cleaning has been proven to be effective for controlling these hydrocarbons [2,3].…”

Visualizing Evactron® Turbo Plasma™ Cleaning in nanoflight® Movies

“…This new Evactron E50 plasma cleaner operates from a lower base pressure compared to previous models and rapidly removes most hydrocarbons from a vacuum chamber. At turbo pump pressures, Evactron cleaning becomes faster and the downstream plasma afterglow spreads throughout the chamber, removing contamination and significantly shortening pump down time, allowing for high throughput of sample processing and analysis [1].…”