Estimation of exposure parameters of chosen e-beam resists using variable shaped e-beam pattern generator

Abstract

In this article we present results from lithography experiments on PMMA (positive tone), and HSQ resists carried out on the ZBA variable shaped e-beam pattern generators. In order to obtain the necessary information needed for the optimization of the exposure control Point Spread Function PSF, several lithography tests are mentioned. The carried out measurements and analysis of the results help us in obtaining important information about the resists and exposure processes and enable us to practically verify the suggested methods of parameters extraction for a reliable exposure model. IntroductionPrimary structures that are required in microtechnology are usually realized by means of projection photolithographic methods through a mask using image reduction. One of nonoptical imaging processes using charged particles is the Electron Beam Direct Write lithography (EBDW), which enables to overcome the limiting diffraction in the photolithography and considerably increases the resolution limit as well as the image fidelity in the high-end mask and/or chip fabrication. The final resolution in this technique is limited by beam parameters and by the electron interaction processes in the resist/substrate stack. However, EBDW suffers from the so called proximity [1] effects that limit the resolution [2], and so proximity-effect corrections of the exposure data based on experimental measurements [3] should be incorporated. To achieve this, a method which optimizes the Point Spread Function (PSF) for the proximity effect correction must be implemented especially in the case of large and complex chips [4].With modern e-beam writing tools, the resolution and throughput of the electron beam lithography is often limited by the resists used in the process. Resists for advanced maskmaking with high-voltage e-beam writing tools have undergone dramatic changes over the last three decades. However, new materials are developed for nanopatterning and detailed knowledge of resist characteristics is needed due to diverse application of nanolithography. ExperimentalIn this paper we present results from EBDW lithography experiments which have been carried out on the ZBA 10 (30keV mode, thermal emission cathode), ZBA 21 (20keV) and ZBA 23 (20 and 40keV modes, LaB 6 cathode) variable shaped e-beam pattern generators, respectively. Positive-as well as negative-tone e-beam resists were chosen for these experiments, and in order to obtain the necessary information needed for the optimization of the exposure control PSF, some lithography tests were used and the results taken from these experiments are presented.

Comparative study of the sidewall shape and proximity effect in bilayer electron beam resist systems

“…Direct writing electron beam lithography was employed for the experiments. Exposure tests were performed using the variable-shaped electron beam lithography system ZBA23 (Vistec Electron Beam, GmbH) at an electron energy of 40 keV [4,5]. The following electron beam resist materials were selected: polymethyl methacrylate -950 PMMA A2, 495 PMMA A6 (Kayaku), copolymer (methyl methacrylate-co-methacrylic acid) -MMA (8.5) MAA EL11 (Kayaku), SML 300 (EM Resist), AR-P 6200 (CSAR 62) series (Allresist).…”