Abstract
We studied the exposure behavior of low molecular weight polystyrene as a negative tone electron beam lithography (EBL) resist, with the goal of finding the ultimate achievable resolution. It demonstrated fairly well-defined patterning of a 20-nm period line array and a 15-nm period dot array, which are the densest patterns ever achieved using organic EBL resists. Such dense patterns can be achieved both at 20 and 5 keV beam energies using different developers. In addition to its ultra-high resolution capability, polystyrene is a simple and low-cost resist with easy process control and practically unlimited shelf life. It is also considerably more resistant to dry etching than PMMA. With a low sensitivity, it would find applications where negative resist is desired and throughput is not a major concern.
Highlights
Electron beam lithography (EBL) [1], focused ion beam (FIB) lithography [2], and nanoimprint lithography (NIL) [3] are currently the three most widely employed nanolithography techniques
It is preferable to have a negative resist like poly(methyl methacrylate) (PMMA), which is a simple polymer with low cost and practically unlimited shelf life, and can be dissolved using various solvents to give the preferred film thickness
We investigate the ultimate resolution that can be achieved with polystyrene, and demonstrate the patterning of 20-nm-period lines and 15-nm-period 2D dot arrays, which are the highest densities achieved using organic EBL resists
Summary
Electron beam lithography (EBL) [1], focused ion beam (FIB) lithography [2], and nanoimprint lithography (NIL) [3] are currently the three most widely employed nanolithography techniques. Calixarene has been studied as a candidate resist for fabricating using EBL bit-patterned recording media that have achieved areal density of 1.4 and 1.6 Tbits/in (corresponding to a dot array of 20-nm period) [8,9] using very thin (sub-20 nm) film It has low sensitivity despite being a chemically amplified resist, and the acid generated in the exposed area may diffuse into the unexposed area, blurring the latent image. It is preferable to have a negative resist like PMMA, which is a simple polymer with low cost and practically unlimited shelf life, and can be dissolved using various solvents to give the preferred film thickness Polystyrene is such a resist, as it undergoes crosslinking when exposed to deep UV light or an electron beam. We have developed the samples using xylene (o-, m-, p-mixed), chlorobenzene, and cyclohexane
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