Chemically amplified molecular resists for electron beam lithography

Robinson, Alex P. G.; Zaid, Hasnah Mohd; Gibbons, Francis P.; Palmer, Richard E.; Manickam, M.; Preece, Jon A.; Brainard, Robert L.; Zampini, T.; O’Connell, Kathleen

doi:10.1016/j.mee.2006.01.151

Cited by 30 publications

(11 citation statements)

References 14 publications

(14 reference statements)

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“…By adding an epoxy crosslinker (Dow DEN438) for chemical amplification and by spin coating the resist on freshly cleaved substrates, the defect density in the resist film was decreased to very low values [47]. Robinson et al [48] studied the effect of chemical amplification on the sensitivity of fullerene and triphenylene derivatives. The sensitivity of a MF03-04 fullerene (which is a mixture of tetra, penta and hexa methanofullerenes with hydroxyl terminated polyether add-ends) was significantly enhanced from 550 to 8 μC cm −2 when it was chemically amplified with a photoacid generator in combination with a crosslinker.…”

Section: Organic Resistsmentioning

confidence: 99%

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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Section: Organic Resistsmentioning

confidence: 99%

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

2009

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“…Negative tone resists often require an additional material known as a crosslinker, which is mixed with the PAG and resist molecule, and several CA fullerene resist compositions have been explored. [19,20] An example of this type of system is cationic ring opening of pendant epoxide groups, resulting in crosslinked material of different solubility relative to the unirradiated material. Furthermore, the limiting factor in the performance of most CA resist materials is the resolution, [18] which is very dependent on the acid diffusion length and the exposure method whether it is e-beam, extreme ultraviolet (EUV) or immersion lithography.…”

Section: Introductionmentioning

confidence: 99%

Fullerene Resist Materials for the 32 nm Node and Beyond

Gibbons

Robinson

Palmer

et al. 2008

Adv Funct Materials

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Current resist materials cannot simultaneously meet the sensitivity, resolution and line width roughness (LWR) requirements set out by the International Technology Roadmap for Semiconductors (ITRS) for the 32nm node and beyond. Here we present a fullerene‐based, chemically amplified resist system, which demonstrates the potential to fulfill these requirements for next generation lithography. A chemically amplified fullerene resist was prepared, consisting of the derivative MF07‐01, an epoxide crosslinker, and a photoacid generator, such as triarylsulfonium hexafluoroantimonate. The sensitivity of this resist was shown to be between 5 and 10 µC cm−2 at 20 keV for various combinations of post‐application bake and post‐exposure bake conditions. Using 30 keV electron beam exposure, sparse patterns with 15 nm resolution were demonstrated, whilst for dense patterns a half‐pitch of 25 nm could be achieved. The LWR for the densely patterned features is ∼4 nm. The etch durability of the fullerene CA system was shown to be comparable to that of SAL601, a common novolac‐based commercial resist, at almost four times that of silicon.

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“…26 A three-component CA molecular resist system based on a fullerene derivative has recently been presented. [27][28][29] The resist is composed of a methanofullerene with hydroxyl terminated polyether addends, a commercially available epoxy novolac crosslinker (CL), and a commercial available photoacid generator (PAG). The resist showed a sensitivity enhancement to better than 10 µC/cm 2 , whilst remaining capable of linewidths of 20 nm for sparse features.…”

Section: Introductionmentioning

confidence: 99%

Chemically amplified fullerene resists for e-beam lithography

Manyam

Gibbons

Diegoli

et al. 2008

Advances in Resist Materials and Processing Technology XXV

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The minimum lithographic feature size for microelectronic fabrication continues to shrink, and resist properties are beginning to dominate the achievable resolution. There is a strong need for a high resolution, high sensitivity resist for future nodes that is not met by conventional polymeric resists at this time. Molecular resists, such as fullerene derivatives have the potential for lower LWR and improved resolution, but have typically been insufficiently sensitive to irradiation. Here we present a fullerene based three component chemically amplified resist system with high resolution and sensitivity, and wide process latitude. The sensitivity of this resist is between 5 and 10 µC/cm 2 at 20 keV for various combinations of post application bake and post exposure bake conditions. Using 30 keV electron beam exposure, sparse patterns with 12 nm resolution were demonstrated, at a line dose of 300 pC/cm, whilst dense patterns with half-pitch 20 nm were achieved at 200 pC/cm. The LWR for the densely patterned resist (measured at 20 nm half pitch) is ~ 4.4 nm, whilst for the 12 nm sparse feature the measured LWR is ~ 2.5 nm. The etch durability is comparable with commercial novolac resists

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Chemically amplified molecular resists for electron beam lithography

Cited by 30 publications

References 14 publications

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

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

Fullerene Resist Materials for the 32 nm Node and Beyond

Chemically amplified fullerene resists for e-beam lithography

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