XEI Scientific, Inc.

RF Plasma Cleaning Systems for Electron Microscopes
and High Vacuum Systems

The EVACTRON® Anti-Contaminator and De-Contaminator
Stops Artifacts and Removes Hydrocarbons and Organics.

Updated January 2010

Examples of Evactron Cleaning

In CD SEM work, the modification of dimensions by the SEM measurement process can cause loss of precision in the measurement. On a very clean Hitachi 6280, the test pattern (left) began to show filling-in of the holes after a long scan (20 minutes). After EVACTRON in situ cleaning of the chamber and the specimen, a repeat of the measurement showed no filling of the holes and a much reduced scan mark.
-Andras Vladar NIST

Black focusing squares on resolution test specimens are a common problem. Before cleaning the instrument for the first time, a black square covers the scanned area. After cleaning for 5 minutes, the square is greatly reduced. Further cleaning removed all evidence of scan squares. (Below)
-Andras Vladar NIST

Courtesy of Bryan Tracy, Spansion

Carry-over or line width growth during multiple CD SEM scans is a major area of concern. After only one 30 minute Evactron cleaning session, carry-over was stopped as illustrated in the results shown on the left.

Also see Science Papers for more examples in publications.

Hitachi S4700: Spansion, Sunnyvale, California, USA
Improved resolution was observed, on a 5 year old instrument so that sputtered PT grains could be imaged at 5kV and < 3 nm resolution. The user says that the Evactron De-Contaminator is the only accessory one can buy for the SEM that will improve the performance of the instrument.

FEI 235 Dual Beam FIB: FEI Company, Hillsboro Oregon, USA
The FEI Company was having problems meeting contamination specifications on new Dual Beam 235 FIBs during the final manufacturing test. Solvent cleaning and wipe downs of chamber and stage failed to control the problem on some units. The problem was thought to be with residual machining oil on parts.

With less than four hours of Evactron cleaning over two days during a demonstration, the contamination deposition rate was brought down from being 2 times over the FEI specification amount to less that 10% of the specification. FEI purchased an Evactron unit for manufacturing to make sure all Dual Beam FIBs are clean on departure.

FEI 235 Dual Beam FIB: AMD, Sunnyvale, California, USA
The FEI FIBs make use of a Gas Injection Systems (GIS) for metal deposition using the ion beam. This technique uses organometallic gases that react with the ion beam to deposit metals on the scanned areas. Organic gases, released as a by product, contaminate the chamber and the specimen surface.

AMD uses the Dual Beam FIB to study the structure of sub 170 nm copper vias for process control. The use of GIS platinum deposition guns had released organics into the chambers, creating foggy images of these small structures. The installation of an Evactron system allows for faster and clearer imaging of these very small structures.

JEOL 6400: Kimberly Clark, Neenah Wisconsin, USA
A JEOL 6400 was used for imaging wood and paper products. The microscope had also an oily window problem on the EDS Detector. Installing an Evactron system cleaned up the chamber and periodic use prevents buildup of contamination on the wall of the chamber. Additionally, oil stopped building up on the EDS Detector.

JEOL 6400 and JEOL 845: IBM Canada, Bromont, Quebec, Canada
This semiconductor research lab had persistent problems with contamination until the Evactron system was installed on these two SEMs.

Hitachi S-4500: IBM San Jose, California, USA
The user images magnetic disks coated with a lubricant. Over time, the lubricant had heavily contaminated the chamber and images of defects had to be obtained solely on the first pass. After cleaning with an Evactron De-Contaminator (D-C), contamination problems disappeared. The user now cleans the chamber with an Evactron D-C every 2 to 4 weeks, as needed. The system also has an EDS detector and after the installation of the Evactron system, the oily window problems have stopped.

The results were presented at a 1999 Microscopy & Miroanalysis (M&M) conference in the paper “The Removal of Contamination Deposits From Defects in Thin Film Magnetic Disks By Oxidative Cleaning Inside The SEM”, by Sharon Meyers and Ronald Vane.

Hitachi S-4500: AMD, Sunnyvale, California, USA
An Evactron system was installed on this SEM when new, to prevent contamination. It has been operated by an automatic system for 2 minutes cleaning, every day. No contamination problems have ever been noted on this SEM.

Hitachi S-4700: NIST Gaithersburg, Maryland, USA
NIST borrowed and later purchased an Evactron D-C for controlling contamination in an Hitachi S-4700 SEM. Their research on contamination control resulted in the paper "Active Monitoring and Control of Electron Beam Induced Contamination" Proc. SPIE Vol. 4344 (2001), 835, by András E. Vladár, Michael T. Postek and Ronald Vane. This study found that the Evactron device was "effective in cleaning the vacuum of the specimen chamber of laboratory and production metrology SEMs."

Hitachi S-4700: Oak Ridge National Laboratory, High Temperature Materials Lab, Oak Ridge, Tennessee, USA
Roughing pump oil backstreaming through the sample exchange chamber was causing dirty specimens and chamber contamination that could not be controlled with a liquid nitrogen (LN) cold finger. Contamination is controlled by use of both the plasma cleaning and the nitrogen purge features of an automatic Evactron system.

Hitachi S-4700: University of Illinois, Champaign-Urbana, Illinois, USA
A three year old Hitachi S-4700 SEM had constant contamination problems since being installed. The user had added a turbomolecular pump and heated micromaze foreline trap, but they made little difference. LN traps, top and bottom, had been kept in service constantly, but failed to stop contamination problems.

The user purchased an Evactron system with the automation package. The automation package operates the Hitachi SEM evacuation system with the proper delays to allow for the cooling of the heated aperture before venting the chamber to Evactron operating pressure. The automatic package then operates the plasma clean cycle for 2 minutes. The system is then ready to image specimens again, 40 minutes after the Evactron cleaning cycle.

Multiple cleaning cycles were done during installation for testing and demonstration purposes over two days. After installation was completed, an old gold on carbon specimen was imaged. This specimen had shown chronic contamination problems in the past with black squares forming quickly. After Evactron cleaning of the chamber, the specimen showed no black square formation even with dry LN traps during this first test. Cleanliness is maintained by operating the Evactron system on a weekly maintenance cycle.

LEO 1550 and JEOL 6400: University of California, Berkeley, California, USA Microfabrication Laboratory
The student-used SEMs were heavily contaminated by student use on dirty specimens. The SEM maintenance technician does not have time to watch over every user. LEO 1550 SEM has a valveless turbopump pumping system and no load lock. The SEM technician did not want to teach users how to clean with Evactron system and did not want to spend time doing cleaning himself.

The Evactron De-Contaminator (D-C)was set up to operate during every pump down cycle for 100 seconds. By adjusting the gas leak and the vacuum set points for plasma operation, the cleaning takes place while the SEM chamber pumps down through the 0.9 Torr to 0.4 Torr pressure zone. Operating the Evactron D-C adds less than one minute to pump down time and was not noticed by most users. Pump down to high vacuum was speeded up because UV light generated by the plasma is effective at desorbing water vapor from walls during the cleaning cycle in the roughing mode.

Cross contamination between specimens has disappeared. Higher resolutions are being observed. UCB Physics Department ordered a third Evactron D-C for the new FEI Sirion SEM in 2003, for use at Lawrence Berkeley Labs.

LEO 1525: NIST, Boulder, Colorado, USA
NIST purchased an Evactron De-Contaminator to assist in backscatter electron diffraction measurements. The slightest layer of carbon interferes with these measurements. Evactron cleaning of the specimen and chamber before measurement ensures the cleanest possible measurements. By adjusting the leak rate, pressure can be maintained in the Evactron cleaning zone for up to five minutes, if needed.

LEO 1550: Intel, Sacramento, California, USA
The microscope is staying clean and pump-down speeds are increased. UV light from the Evactron system, desorbs water from chamber walls during pump-down with Evactron cleaning. This system has no sample airlock so the Evactron De-Contaminator is used to remove both hydrocarbons and water vapor from the chamber.

Leica S360 SEMs, FEI FIBs, FEI XL30 SEM and FEI Sirion SEM: Wright Patterson AFB, Dayton Ohio, USA
WPAFB purchased two Evactron De-Contaminators in 2002 for use on two Leica S360 SEMs. In 2003, they purchased 4 more Evactron units for use on two FEI FIBs and two FEI SEMs, an XL30 and a new Sirion.