Extreme ultraviolet patterning of tin-oxo cages

Abstract

We report on the extreme ultraviolet (EUV) patterning performance of tin-oxo cages: molecular building blocks that are known to turn insoluble upon EUV exposure, thus having the properties of a negative tone photoresist. In this work, we focus on contrast curves of the materials using open-frame EUV exposures and their patterning capabilities using EUV interference lithography. It is shown that baking steps, such as post-exposure baking (PEB) can significantly affect both the sensitivity and contrast in the open-frame experiments as well as the patterning experiments. In addition, we show that the exchange of the anions of the cage can make a difference in terms of their physical properties. Our results demonstrate the significance of process optimization while evaluating the resist performance of novel molecular materials.

XUV Induced Bleaching of a Tin Oxo Cage Photoresist Studied by High Harmonic Absorption Spectroscopy

“…TinOH films were spin-coated on free-standing silicon nitride (Si 3 N 4 ) membranes (NORCADA; 30 nm thickness) [9,10]. With the same spin coating method film thicknesses of 30 -40 nm were obtained on other substrates [12,17].…”

“…In previous work, TinOH and related compounds were exposed to EUV, Deep UV (DUV), and electrons of various energies [8,12,[17][18][19]. In the work presented here we used broadband extreme ultraviolet (XUV) pulses with energies in the range 25 -40 eV to induce photo-reactions in thin films of the tin oxo cage resist, and to simultaneously study the transmission changes.…”

Photochemical conversion of tin-oxo cage compounds studied using hard x-ray photoelectron spectroscopy

“…The formation of such an oxidation-sensitive but otherwise stable reaction product could be the explanation of our finding that the formation of insoluble material after exposure to EUV is enhanced by postexposure baking. 28…”

Photoreactions of Tin Oxo Cages, Model EUV Photoresists

“…Preparation of the compounds, largely following the literature [15,16] and of thin films of TinOAc has been described recently [9]. The thickness of the films was 30 nm, as determined by means of AFM and ellipsometry.…”

“…These systems combine several advantages: the demonstrated EUV patterning underscores their relevance for the EUVL field [7,9], the absorption cross sections are 2 -3 times higher than those of organic polymers [5], and the materials are of a molecular nature, consisting of small (~1 nm) and fully defined building blocks. The goal of our research in this field is to boost the fundamental level of understanding of the photoresist performance in relation to the chemical processes that take place upon activation of these materials by high energy sources such as UV and EUV photons as well as electrons.…”