Electron beam lithography process using radiation sensitive carboxylate metalorganic precursors

Abstract

A bilayer process has been developed for electron beam lithography using radiation sensitive metalorganic precursors as imaging layers in conjunction with organic planarizing layers. Upon electron beam irradiation, the precursor is converted to a metal oxide which serves as an etch mask for subsequent pattern transfer through the planarizing layer. In this article, a titanium(n-butoxide) 2 (2-ethylhexanoate) 2 precursor was investigated that exhibits sensitivity and contrast of 495 C/cm 2 and 2.75, respectively, 10 keV accelerating potential. The sensitivity was further enhanced to 72 C/cm 2 using a pre-exposure thermal bake to partially convert the precursor to metal oxide prior to electron beam imaging. Additionally, it was found that combining the titanium(n-butoxide) 2 (2-ethylhexanoate) 2 precursor with a similar precursor containing a higher atomic number metal center, barium(2-ethylhexanoate) 2 in this work, also enhanced the sensitivity to 157 C/cm 2 for a 1:1 molar mixture of the precursors. After imaging and development, the patterns were completely converted to metal oxide by thermal baking to improve the etch resistance of the hard mask. This postdevelopment thermal conversion step was found to result in vertical shrinkage of the features and minimal lateral shrinkage. For bilayer processing, the titanium precursor was imaged on top of hard baked novolac and the pattern was transferred through the novolac using an O 2 reactive ion etch. Sub-100 nm patterning is demonstrated using both single layer and bilayer processes with these materials, with aspect ratios greater than five achieved with the bilayer process.

X-ray absorption fine structure study of amorphous metal oxide thin films prepared by photochemical metalorganic deposition

“…Metal 2-ethylhexanoates are used as precursors to metal oxides [22], and are converted using methods such as thermal decomposition [23][24][25], exposure to light [26][27][28][29][30][31][32][33], or exposure to high-energy electron [34][35][36] or ion [31] beams. Our previous efforts have focused on the latter two methods, as they are conducive to the direct patterning of metal oxide [26,[28][29][30] and nanocomposite [27,37] thin films onto a substrate.…”

Fabrication of sub 50-nm direct-patterned Pb(Zr,Ti)O3 films by electron beam-induced metal-organic deposition

“…2(a)) that the films were partially crystallized with a preferred <111> orientation due to (111) plane matching with Pt substrate [8]. Jeyakumar et al [9] and Saifullah et al [10] report that an exposure of electron beam sensitive precursor films to an electron beam results in the cleavage of organic ligands from the central metal atom and converts the metal atom to a metal oxide. In our case, the oxygen content was enough for the metal to convert to a metal oxide during the electron beam exposure because the ratio of metal (Pb, Zr, and Ti) to oxygen was 1 to 5 in the PZT starting precursors.…”

Direct Photopatterning of Metal Oxide Structures Using Photosensitive Metallorganics

“…It has been demonstrated that feature sizes below 100 nm can be achieved using similar metallorganic precursor films in conjunction with electron beam lithography. 25,26 Following exposure and development, the resulting oxide features were examined by SEM. The features were found to be slightly wider at the top than at the bottom.…”