Design and implementation of the next generation electron beam resists for the production of EUVL photomasks

Abstract

A new class of resist materials has been developed that is based on a family of heterometallic rings. The work is founded on a Monte Carlo simulation that utilizes a secondary and Auger electron generation model to design resist materials for high resolution electron beam lithography. The resist reduces the scattering of incident electrons to obtain line structures that have a width of 15 nm on a 40 nm pitch. This comes at the expense of lowering the sensitivity of the resist, which results in the need for large exposure doses. Low sensitivity can be dramatically improved by incorporating appropriate functional alkene groups around the metal-organic core, for example by replacing the pivalate component with a methacrylate molecule. This increases the resist sensitivity by a factor of 22.6 and demonstrates strong agreement between the Monte Carlo simulation and the experimental results. After the exposure and development processes, what remains of the resist material is a metal-oxide that is extremely resistant to silicon dry etch conditions; the etch selectivity has been measured to be 61:1.

Resists for Helium Ion Beam Lithography: Recent Advances

“…79 Lewis et al have developed a chromium-based negative tone metal−organic resist for the application toward the fabrication of field emission transistor. 76,80 The structure of the resist is shown in Figure 16 . This resist showed the capability to produce sub-10 nm structures on silicon and tungsten by HIBL.…”

Plasma-Etched Pattern Transfer of Sub-10 nm Structures Using a Metal–Organic Resist and Helium Ion Beam Lithography

“…In comparison with a previous study of Cr 8 F 8 (pivalate) 16 with EBL (100 keV, 300 pA), HIBL required a dose three orders of magnitude smaller to achieve its smallest pitched lines. (EBL achieved 40 nm pitch lines at a 30 500 pC/cm line dose compared with a 16 nm pitch at 22 pC/cm here.)…”

“…The next smallest transferred patterns found in the literature are on a 22 nm pitch via thermal scanning probe lithography. 25 In comparison with a previous study of Cr 8 F 8 (pivalate) 16 with EBL (100 keV, 300 pA), 15 HIBL required a dose three orders of magnitude smaller to achieve its smallest pitched lines. (EBL achieved 40 nm pitch lines at a 30 500 pC/cm line dose compared with a 16 nm pitch at 22 pC/cm here.)…”

“…In this Letter, a metal–organic, negative tone resist candidate, Cr 8 F 8 (O 2 C t Bu) 16 (Figure ), first introduced by our group in ref and henceforth denoted as Cr 8 F 8 (pivalate) 16 , is presented. It is formed by the binding of eight chromium atoms (in green in Figure ) in a ring-like structure, with an exterior composed entirely of tert- butyl groups (pivalates) . The pivalates provide a high solubility in nonpolar solvents, which allows the resist molecule to be dissolved in hexane and spun onto substrates (e.g., Si and W).…”

“…It is formed by the binding of eight chromium atoms (in green in Figure 1) in a ring-like structure, with an exterior composed entirely of tert-butyl groups (pivalates). 15 The pivalates provide a high solubility in nonpolar solvents, which allows the resist molecule to be dissolved in hexane and spun onto substrates (e.g., Si and W). The molecule achieves high-resolution patterning because it is simultaneously low density (ρ = 1.212 g cm −3 ), meaning that it does not have many lateral scattering centers for the lithography beam to interact with as it travels through, and has a high molecular weight (2192 g mol −1 ), meaning that the number of resist molecules that are required to produce a thin film is significantly reduced, leading to a high-resolution pattern.…”