Nanolithography and direct exposure of SiO2 layers

The ultimate resolution of electron optical systems far exceeds that of conventional electron resists. Electron beams less than 0.5 nm in diameter can be produced but the smallest features that can be written with these beams in standard resists are about 10 nm–20 nm in size and the minimum spacing for closely spaced lines is about 40 nm. The reason for this loss of resolution is not clear. It may be due to the range of the Coulomb interaction between the beam electrons and the resist molecules, due to the straggling of secondary electrons away from the primary beam, due to the high molecular weight of the resist or due to the mechanism of the development process. In the first two cases resolution would improve if the photon energy required to effect exposure was increased. With PMMA, the most studied resist, the energy required for exposure is about 5 eV. We have been working with an alternative nanolithography process using SiO2 layers that has about three times better resolution than PMMA. We assume th...