A Study of the Effectiveness of the Removal of Hydrocarbon Contamination by Oxidative Cleaning Inside the Sem

Sullivan, Neal P.; Mai, Tung; Bowdoin, Scott; Vane, Ronald

doi:10.1017/s1431927602106234

Cited by 12 publications

(8 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, such a carbon-rich contamination coating could be scavenged by the radical oxygen in combination with thermal heating. A similar oxygen radical scavenging process has also been reported as being successful for removing hydrocarbon surface residue in electron microscope vacuum environments [15]. Fig.…”

Section: The Epi-yig Layersmentioning

confidence: 57%

The enhancement of magnetically ordered oxide layered structures using oxygen radical processing

Rios¹,

Bandyopadhyay²,

Smith³

et al. 2005

Journal of Magnetism and Magnetic Materials

View full text Add to dashboard Cite

Section: The Epi-yig Layersmentioning

confidence: 57%

The enhancement of magnetically ordered oxide layered structures using oxygen radical processing

Rios¹,

Bandyopadhyay²,

Smith³

et al. 2005

Journal of Magnetism and Magnetic Materials

View full text Add to dashboard Cite

“…Several published studies [1,2,3] have found that the origins of the contamination are both the sample itself and the vacuum in the SEM. Although the pumping system is a major contributor to this problem, the history of the specimen prior to entering the vacuum system must also be considered relative to the deposition of hydrocarbon contamination.…”

mentioning

confidence: 99%

Electron Beam-Induced Sample Contamination in the SEM

Vladár

Postek

2005

MAM

View full text Add to dashboard Cite

Electron beam induced contamination, i.e. the deposition of carbonaceous material over the sample surface bombarded by the electron beam is almost always present after viewing in the scanning electron microscope (SEM). This is one of the most troublesome problems in high-resolution scanning electron microscopy since it induces physical change the actual structure of the material being viewed, generally by obscuring the fine detail. Its importance is growing, especially for nanometer resolution imaging, where small surface structures can easily be buried in even few seconds. Therefore, it is essential to find the origins of electron beam induced contamination and regularly measure it and keep it at acceptable levels.Several published studies [1,2,3] have found that the origins of the contamination are both the sample itself and the vacuum in the SEM. Although the pumping system is a major contributor to this problem, the history of the specimen prior to entering the vacuum system must also be considered relative to the deposition of hydrocarbon contamination. All this leads to problems especially at low accelerating voltages where the carbonaceous layer deposited by the electron beam becomes extremely obvious. It is common that instruments with "good" vacuum will still exhibit unacceptable rates of electron beam induced contamination because of residual organic materials in the vacuum. (Figure 1.) Deposition rates of a few tens of nanometers per second have been observed, but smaller rates are more common especially with the more "modern" instruments. In many cases the presence of contamination is not obvious; it only leads to a change in the amount of electrons leaving the sample, hence a drop of signal. In other cases, surface contamination will lead to serious measurement errors and thus, will rule out collection of any useful data.Reimer [4] describes a process of drift of large molecular weight molecules under the electron bombardment. The deposition of the material forming the contamination layer is a dynamic process. Molecules arrive at and leave the sample surface at the same time. The amount of contamination deposited depends on the electron dose, (i.e. the length of time the beam dwells on the sample and the beam current). The longer the dwell time, the thicker the contamination becomes.In this study we report the results of contamination rate measurements, the dependence of the deposition of contaminants on electron beam current and landing energy and sample composition. We also report the results effective cleaning methods that were successfully used to diminish electron beam induced sample contamination. For sample cleaning a Model 1020 Plasma Cleaner** from Fischione Instruments [5] was used and for cleaning of the SEM sample chamber an Evactron® RF Plasma Cleaner -Anti-Contaminator unit from XEI Scientific [6] was used. The SEMs used in this study were high vacuum and environmental type microscopes. These results were obtained both before and after cleaning of the SEM and samples.

show abstract

“…

…”

mentioning

confidence: 99%

Quantification of Contamination Using Quartz Thickness Monitors

Morgan¹,

Gleason²,

Vane³

2007

MAM

View full text Add to dashboard Cite

Hydrocarbon (HC) contamination is a persistent problem for users of electron microscopes, often leading to image distortion and interference with nanoprobing [1][2][3][4]. Quantifying the amount of contamination present by easy, low cost methods has been a challenging problem. Contamination levels in Electron Microscopes are usually determined by measuring electron beam deposition of HC on a clean surface and imaging the resulting HC mound or black square [5]. If the specimen can be tilted the height of the deposited mound can be measured. The problem with this technique is that in a relatively clean instrument, it may take 20 to 200 minutes to accumulate a significant deposit for measurement.As an alternative, a quartz monitor could be mounted on the stage for a new method of quantifying contamination. Quartz crystal thin film thickness monitors are a standard technique for measuring the vacuum deposition of thin films and are available from many manufacturers [6]. Commonly used for measuring sputter coating, they can be adapted to measure contamination in electron microscopes and the rate of contamination removal by plasma cleaning. Liquid cooling of the monitor is not needed as it is for Sputter coating processes, but an RF feedthrough port is needed for the monitor. The electron beam is scanned on the monitor and the thickness build rate of HC is available almost immediately.The Evactron® De-Contaminator (D-C) has been available for contamination removal in SEMs since 1999 [7]. The Evactron D-C uses low power radio frequency (RF) generator plasma in order to produce oxygen radicals which clean an electron microscope (EM). The oxygen radicals chemically react with the HCs to form volatile oxidation products such as H 2 O, CO and CO 2 . These volatile compounds can be pumped out of the EM chamber. The efficiency of the Evactron process has been demonstrated qualitatively. A light HC deposit can be removed from a mirrored surface in minutes, but achieving a reproducible deposit and removal data is difficult.Efforts have been made to provide quantitative tests of the efficiency of the Evactron cleaning process using a quartz crystal thickness monitor. A picture of the quartz crystal thin film thickness monitor is shown in Figure 1. The thickness monitor (McVac -MCM 160) was placed inside the vacuum chamber ~1 cm directly in front of a port fitted with an 11 cm long piece of steel vacuum tube containing 5 to 7 drops of oil. The end of the vacuum tube was capped with an adapter flange fitted with a needle valve that was used to bleed air through the tube. The chamber pressure was adjusted to 0.15 mbar with the needle valve. The tube containing the oil was heated for 5-7 minutes and then allowed to cool for ca. 5 minutes. Visual inspection normally revealed a thin film of oil on the thickness meter, on the end cap, and lining the opening into vacuum chamber. This method produced more contamination than would normally be seen in an EM; however, enough oil was placed on the thickness monitor so that the rate of oil re...

show abstract

A Study of the Effectiveness of the Removal of Hydrocarbon Contamination by Oxidative Cleaning Inside the Sem

Cited by 12 publications

References 0 publications

The enhancement of magnetically ordered oxide layered structures using oxygen radical processing

The enhancement of magnetically ordered oxide layered structures using oxygen radical processing

Electron Beam-Induced Sample Contamination in the SEM

Quantification of Contamination Using Quartz Thickness Monitors

Contact Info

Product

Resources

About