Scanning x-ray microscopy investigations into the electron-beam exposure mechanism of hydrogen silsesquioxane resists

Abstract

Electron-beam exposed hydrogen silsesquioxane cross-linking chemistry is investigated by Scanning Transmission X-ray Microscopy (STXM) and Atomic Force Microscopy (AFM). Using STXM, a maximum in the chemical contrast is obtained by measuring the x-ray absorption at 534.5 eV, corresponding to the 1s K-edge transition in oxygen. An area-dependent and dose-dependent chemical conversion is observed for feature sizes between 150 nm and 10 μm and doses between 0.4 mC and 40 mC. The activated (cross-linked) regions extend beyond the exposure zones, especially for higher dosed exposures. With AFM, density changes in the latent images (e-beam exposed but undeveloped) are observed, which also display a dependence on exposed area.Potential mechanisms, involving chemical diffusion outside the exposure zone, are discussed.

Influence of hydrogen silsesquioxane resist exposure temperature on ultrahigh resolution electron beam lithography

“…Heating of the resist under electron beam exposure was considered negligible ͑i.e., Ͻ1°C͒ taking into account the small e-beam probe size, relatively low beam current and accelerating voltage, thin resist thickness, and good heat conductivity of the Si substrate. This assumption is consistent with data from reports on direct measurement 9 as well as with modeling 10 and analytical evaluation 11,12 of e-beam induced temperature rise. A cascade of Peltier elements was mounted on the stage equipped with an Al heat absorber allowing us to control the temperature of the substrate in range from −20 up to 90°C.…”

Electron-beam exposure mechanisms in hydrogen silsesquioxane investigated by vibrational spectroscopy and in situ electron-beam-induced desorption

“…Even if a water reaction product was consumed in the reaction via reaction scheme (2), water would be expected to escape at the edges of the reaction front and be detected at higher levels in the EBID. However, because we have observed that exposed, undeveloped films that showed a thickness reduction after exposure 17 would recover their original thickness after a few weeks (suggesting absorption of ambient H 2 O or O 2 by the film), we cannot rule out that reactions (2) and (3) occur after removal from the lithography system.…”

“…In terms of the observed area-dependent exposure dose for HSQ, 15,17 dehydrogenation of silicon may be playing an important role. In radiation exposed polydimethyl silsesquioxane films, hydrogen radicals diffuse considerable distances before reacting.…”

“…15 Investigations using scanning transmission x-ray microscopy show that the types of chemical changes induced by electronbeam exposure show an usual dependence on both exposure area and electron dose. 17 These chemical changes are initiated by the beam, and unfortunately can extend well beyond exposed area. These instabilities must be understood and controlled to take advantage of HSQ type materials for productionworthy processes such as EUV lithography or even to expect repeatability in smaller-scale electron beam prototyping.…”

Fabrication of Advanced Functional Devices Combining Soft Chemistry with X‐ray Lithography in One Step

“…[16] Only a few studies have been published combining DXRL with metallorganic precursors. [17][18][19][20][21][22][23] These previous studies show successful patterning of sol-gel polymethylsisesquioxane-based films but require a buffer coating [17,18] or a crosslink promoter [19] to achieve adequate patterning. In the case of hydrogensilsesquioxanes, sol-gel polymer hybrid films have been patterned using EBL; [21,22] however, these high organic content photoresists present some drawbacks, such as irreproducibility, reaction front propagation beyond the exposed regions, and thermal stability, that need to be overcome.…”