Influence of the development process on ultimate resolution electron beam lithography, using ultrathin hydrogen silsesquioxane resist layers

Grigorescu, Anda E.; Krogt, Marco C. van der; Hagen, C. W.; Kruit, P.

doi:10.1116/1.2794316

Cited by 25 publications

(26 citation statements)

References 8 publications

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“…HSQ is also an excellent resist for testing e-beam machine resolution limits because HSQ lines on silicon can be imaged directly in a SEM without the need for gold evaporation for conduction or 'lift-off' techniques [58]. Sub-10-nm isolated and dense features have been successfully fabricated using 100 keV EBL [59][60][61]. Low LER (below 2 nm) and high etch resistance (for single and bilayers) have been reported in several papers [22,59,62].…”

Section: Overviewmentioning

confidence: 99%

“…Sub-10-nm isolated and dense features have been successfully fabricated using 100 keV EBL [59][60][61]. Low LER (below 2 nm) and high etch resistance (for single and bilayers) have been reported in several papers [22,59,62]. The properties of the resist (e.g.…”

Section: Overviewmentioning

confidence: 99%

“…Grigorescu et al [59] studied the effect of different developers on resolution. Lines with widths between 7 and 12 nm at 20 nm pitch were successfully fabricated, and an optimum dose to define such lines was found for all developers.…”

Section: Development Processmentioning

confidence: 99%

“…In the search for the ultimate resolution, several other developers have been tested such as a potassium hydroxide (KOH) buffered solution (AZ 400 K from Clariant) or a sodium hydroxide (NaOH) buffered solution (Microposit 351 from Rohm and Haas) [59,22,75]. Grigorescu et al [59] studied the effect of different developers on resolution.…”

Section: Development Processmentioning

confidence: 99%

“…In the other situation, the uncertainty in the measured linewidth increases and one way to prevent this is to write dense lines and spaces. Grigorescu et al [59,72] studied the effect of the development process on the ultimate resolution of EBL using ultrathin HSQ layers. They showed that the fabrication of small structures is very complicated due to several interconnected factors which influence the final result of the e-beam patterning.…”

Section: Development Processmentioning

confidence: 99%

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Resists for sub-20-nm electron beam lithography with a focus on HSQ: state of the art

2009

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In the past decade, the feature size in ultra large-scale integration (ULSI) has been continuously decreasing, leading to nanostructure fabrication. Nowadays, various lithographic techniques ranging from conventional methods (e.g. photolithography, x-rays) to unconventional ones (e.g. nanoimprint lithography, self-assembled monolayers) are used to create small features. Among all these, resist-based electron beam lithography (EBL) seems to be the most suitable technique when nanostructures are desired. The achievement of sub-20-nm structures using EBL is a very sensitive process determined by various factors, starting with the choice of resist material and ending with the development process. After a short introduction to nanolithography, a framework for the nanofabrication process is presented. To obtain finer patterns, improvements of the material properties of the resist are very important. The present review gives an overview of the best resolution obtained with several types of both organic and inorganic resists. For each resist, the advantages and disadvantages are presented. Although very small features (2-5 nm) have been obtained with PMMA and inorganic metal halides, for the former resist the low etch resistance and instability of the pattern, and for the latter the delicate handling of the samples and the difficulties encountered in the spinning session, prevent the wider use of these e-beam resists in nanostructure fabrication. A relatively new e-beam resist, hydrogen silsesquioxane (HSQ), is very suitable when aiming for sub-20-nm resolution. The changes that this resist undergoes before, during and after electron beam exposure are discussed and the influence of various parameters (e.g. pre-baking, exposure dose, writing strategy, development process) on the resolution is presented. In general, high resolution can be obtained using ultrathin resist layers and when the exposure is performed at high acceleration voltages. Usually, one of the properties of the resist material is improved to the detriment of another. It has been demonstrated that aging, baking at low temperature, immediate exposure after spin coating, the use of a weak developer and development at a low temperature increase the sensitivity but decrease the contrast. The surface roughness is more pronounced at low exposure doses (high sensitivity) and high baking temperatures. A delay between exposure and development seems to increase both contrast and the sensitivity of samples which are stored in a vacuum after exposure, compared to those stored in air. Due to its relative novelty, the capabilities of HSQ have not been completely explored, hence there is still room for improvement.Applications of this electron beam resist in lithographic techniques other than EBL are also discussed. Finally, conclusions and an outlook are presented.

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