Contribution to the contamination problem in transmission electron microscopy

Reimer, Ludwig; Wächter, M.

doi:10.1016/s0304-3991(78)80023-0

Cited by 48 publications

(17 citation statements)

References 3 publications

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“…If a large beam is used, nonuniform height distributions are found, as, for instance, reported by Fourie 110 and Reimer and Wächter. 111 They studied contamination growth in early electron optical systems. When irradiating a substrate with a beam with a diameter of some micrometers, deposition of carbon occurred only along the edge of the beam and not in the center.…”

Section: Height and Widthmentioning

confidence: 99%

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A critical literature review of focused electron beam induced deposition

Dorp

Hagen

2008

Journal of Applied Physics

486

577

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An extensive review is given of the results from literature on electron beam induced deposition. Electron beam induced deposition is a complex process, where many and often mutually dependent factors are involved. The process has been studied by many over many years in many different experimental setups, so it is not surprising that there is a great variety of experimental results. To come to a better understanding of the process, it is important to see to which extent the experimental results are consistent with each other and with the existing model. All results from literature were categorized by sorting the data according to the specific parameter that was varied ͑current density, acceleration voltage, scan patterns, etc.͒. Each of these parameters can have an effect on the final deposit properties, such as the physical dimensions, the composition, the morphology, or the conductivity. For each parameter-property combination, the available data are discussed and ͑as far as possible͒ interpreted. By combining models for electron scattering in a solid, two different growth regimes, and electron beam induced heating, the majority of the experimental results were explained qualitatively. This indicates that the physical processes are well understood, although quantitatively speaking the models can still be improved. The review makes clear that several major issues remain. One issue encountered when interpreting results from literature is the lack of data. Often, important parameters ͑such as the local precursor pressure͒ are not reported, which can complicate interpretation of the results. Another issue is the fact that the cross section for electron induced dissociation is unknown. In a number of cases, a correlation between the vertical growth rate and the secondary electron yield was found, which suggests that the secondary electrons dominate the dissociation rather than the primary electrons. Conclusive evidence for this hypothesis has not been found. Finally, there is a limited understanding of the mechanism of electron induced precursor dissociation. In many cases, the deposit composition is not directly dependent on the stoichiometric composition of the precursor and the electron induced decomposition paths can be very different from those expected from calculations or thermal decomposition. The dissociation mechanism is one of the key factors determining the purity of the deposits and a better understanding of this process will help develop electron beam induced deposition into a viable nanofabrication technique.

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Section: Height and Widthmentioning

confidence: 99%

“…111 If gF / N 0 Ӷ J the area under the beam will quickly become depleted of mobile precursor molecules. The supply of new molecules will have to come from outside the irradiated area.…”

Section: Height and Widthmentioning

confidence: 99%

A critical literature review of focused electron beam induced deposition

Dorp

Hagen

2008

Journal of Applied Physics

486

577

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“…ited from the atmosphere can be drastically reduced when washing the specimen in methanol or ethanol overnight (Harada et al 1979, Reimer andWachter 1978). We also applied this method successfully in SEM and if possible it should also be used when reducing the contamination to very small rates by specimen cooling.…”

Section: Cleaning Procedures Organic Molecules Depos-mentioning

confidence: 99%

Contamination in a scanning electron microscope and the influence of specimen cooling

et al. 1994

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Summary: Solutions of the stationary and timedependent equations of diffusion are presented for contamination when scanning a rectangular area in the scanning electron microscope (SEM). A method is described to record the thickness of the contamination layer by the signal of secondary or backscattered electrons and to measure the influence of electron current density, beam energy, and specimen cooling on the contamination rate.

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“…Vaughan (1976) avoided contamination by heating a wire. One can also decrease the contamination rate by washing the specimen stub with the grids overnight in pure methanol (Reimer and Wachter 1978) because most of the contamination is caused by surface diffusion of adsorbed organic molecules. If this does not decrease the contamination one should try other precautions (Bottoms 1973) to decrease the partial pressure of organic molecules before starting a high resolution test.…”

Section: Testing Resolution and Astigmatismmentioning

confidence: 99%