Shoko Manako

Calixarene Electron Beam Resist for Nano-Lithography

New electron beam (EB) resists made of calixarene resists are introduced. Typical sensitivities of calixarene resists range from 700 µ C/cm2 to 7 mC/cm2. High-density dot arrays with 15 nm diameter constructed using calixarene resist were easily delineated using a point EB lithography system. Our results suggest that the resolution limit of calixarene resists is dominated by a development process such as adhesion to a substrate rather than by the EB profile. Calixarene resists are resistant to etching by halide plasma. We also demonstrated nanoscale devices processed by using calixarene resists. Calixarene resists are promising materials for nanofabrication.

Nanometer-Scale Patterning of Polystyrene Resists in Low-Voltage Electron Beam Lithography

We studied nanometer-scale patterning using a polystyrene negative resist in electron beam lithography. We found that the use of a low-molecular-weight polystyrene enables 10-nm-level patterning at low-acceleration voltage. We also found that the spot dose of such ultrasmall patterns formed at a 5 kV acceleration voltage was one-tenth of that formed at 50 kV. Low-voltage electron beam lithography is a suitable technique for organic resist nanopatterning. The Charlesby theory can still be applied to nanodot formation, and we can therefore estimate the dot sensitivity for various polystyrene molecular weights. We suppose that an exposure model is based on polymer aggregation to explain the formation of a 10-nm-level pattern with a height of 40 nm can be formed by using a small molecule, not a large one.

Sub‐10 nm lithography and development properties of inorganic resist by scanning electron beam

We report the self‐developing properties of an AlF3‐doped LiF inorganic resist under irradiation by a scanning electron beam with an energy of 20–50 keV are reported. The self‐development properties strongly depended on both AlF3 concentration and film thickness. To explain this behavior, we presented an exposure model that takes into account a balance between a carbon contamination and a diffusion process. By optimizing resist qualities, we were able to delineate 5 nm linewidth patterns with 60 nm periodicity using a 30 kV electron beam.

High resolution organic resists for charged particle lithography

Exposure of resist with electron or ion beams is a common nanolithography technology which is used to fabricate electronic devices and microstructures. The resolution mainly depends on the beam size and the resolution of the resist. We have developed two new high resolution organic resists, which are calixarene derivatives. 50 keV electron beams and 260 keV Be2+ ion beams were used to expose the resist, and 10 nm resolution was achieved with the Gaussian electron beam. The electron beam sensitivities of the two resists were 7 and 0.7 mC/cm2. By using them, we produced 10-nm-order resolution patterns, which we exposed with a Gaussian electron beam. We also achieved 10-nm-level resolution by using a low molecular weight (Mw=1100) polystyrene resist, almost the same Mw as that of the calixarene. The resolution of the polystyrene resist improved as lower molecular weights were used. Therefore, the resist resolution depends on the molecular weight or molecular size.

Nanometer-scale resolution of a chloromethylated calixarene negative resist in electron-beam lithography: Dependence on the number of phenolic residues

We have investigated a chloromethylated calixarene, p-chloromethylmethoxcalix[n]arene (CMC[n]AOMe) (n=5,6,7), as a negative resist in electron-beam lithography. Each CMC[n]AOMe resist has a resolution of about 12 nm and a sensitivity of about 0.8 mC/cm2 which varies slightly with n (or molecular weight). A sub-10-nm Si wire has been fabricated by halide plasma etching and a CMC[n]AOMe resist as an etching mask. Because the resist pattern edge is smooth, Si wires with 7-nm width and 10-μm length were performed without any breaking.

High-purity, ultrahigh-resolution calixarene electron-beam negative resist

Calixarene is a promising high-resolution negative electron-beam resist having a resolution of the order of 10 nm because of its low molecular weight. We have made a purified calixarene resist containing metal contaminants whose concentrations are measured in parts per billion and which therefore do not degrade the performance of silicon-based electron devices. The purity of the calixarene itself was also improved and we obtained high-purity calix[6]arene and high-purity calix[7]arene, both of which contain the main component, which is more than 95% of all the calixarene present. The resolution of both purified calixarene resists is almost the same as that of the unpurified calixarene, but the sensitivity of calix[7]arene is higher than that of calix[6]arene because its molecular weight is higher.

Accurate nano-EB lithography for 40-nm gate MOSFETs

Nanometer electron beam lithography has been used for fabrication of sub-0.1 μm MOSFETs. Chemically amplified resist as a single layer mask showed high resolution by optimizing the resist process. Proximity effect correction was applied and showed a good line width control. Operation of a 40nm-polysilicon gate NMOSFET was confirmed.

Sub‐10 nm lithography and development properties of inorganic resist by scanning electron beams

We report the self‐developing properties of a AlF3‐doped LiF inorganic resist under irradiation by a scanning electron beam with an energy of 50 keV. The self‐development properties strongly depended on both AlF3 concentration and film thickness. The required dose to complete the development seemed to be proportional to the volume under the irradiation area. To explain this behavior, we presented an exposure model that takes into account a balance between a carbon contamination and a transfer process. By optimizing resist qualities, we were able to delineate 5 nm linewidth patterns with 60 nm periodicity using a 30 kV electron beam, and pattern transfer by liftoff was demonstrated.

Nanolithography Using a Chemically Amplified Negative Resist by Electron Beam Exposure

We study the resolution limit for dot patterns using a chemically amplified negative resist by the nanometer electron beam lithography system. It is confirmed that the substrates baked at 270° C after HMDS coating are suitable for fine resist dot patterning. In addition, the post exposure bake (PEB) dependencies of sensitivity and resolution are investigated. As a result, 20-nm-diameter dot resist patterns with a 30 nm height, and 35-nm-diameter dot resist patterns with a 50 nm height are fabricated on Si substrates.

Resolution of calixarene resist under low energy electron irradiation

Abstract The resolution and sensitivity of calixarene resists in relation to incident electron energy were studied. While the sensitivity of the resists was varied in compliance with Bethe theory for the changes of the electron energy, resolution of the resists in terms of the minimum dot size, shows almost the same value of about 10 nm for each electron energy. A Monte Carlo simulation suggests the electron dose at the edge of the dot pattern was only one hundredth of that at the center of the electron beam. This means the major factor in limiting the resolution in calixarene resists was not the electron beam. This means the major factor in limiting the resolution in calixarene resists was not the electron beam profile, but other factors such as a limit due to development processes.