Hydrogen silsesquioxane for direct electron-beam patterning of step and flash imprint lithography templates

Abstract

The feasibility of using hydrogen silsesquioxane (HSQ) to directly pattern the relief layer of step and flash imprint lithography (SFIL) templates has been successfully demonstrated. HSQ is a spin-coatable oxide, which is capable of high resolution electron-beam lithography. Negative acting and nonchemically amplified, HSQ has moderate electron-beam sensitivity and excellent processing latitude. In this novel approach, 6 ×6 × 0.25 in.3 quartz photomask substrates are coated with a 60 nm indium tin oxide (ITO) charge dissipation layer and directly electron-beam written using a 100 nm film of HSQ. Direct patterning of an oxide relief layer eliminates the problems of critical dimension control associated with both chromium and oxide etches, both required processes of previous template fabrication schemes. Resolution of isolated and semidense lines of 30 nm has been demonstrated on imprinted wafers using this type of template. During this evaluation, a failure of the release layer to provide a durable nonstick surface on ITO was discovered and investigated. This problem was successfully remedied by depositing a 5 nm oxide layer over the patterned ITO/HSQ template.

Resists for sub-20-nm electron beam lithography with a focus on HSQ: state of the art

“…In the beginning, HSQ was successfully used as a low-permittivity (low-k) interlayer dielectric in IC technology [65] and afterwards as etch mask in RIE for nanophotonic structures with low roughness [89] and imprinting masters for step and flash imprint lithography (SFIL) [90]. Also, metal oxide semiconductor field effect transistor gates with small dimension and high aspect ratio [77] have been fabricated using HSQ.…”

“…Unlike NIL, this technique is done at room temperature and low pressures. Mancini et al [90] investigated the possibility of using HSQ for direct e-beam patterning of SFIL templates. Quartz photomask substrates were coated with an indium tin oxide charge dissipation layer (ITO) and patterned with an e-beam using a 100 nm thick HSQ resist layer.…”

“…Lines down to 25 and 100 nm pitch written with SFIL on (a) templates and (b) imprinted wafers [90]. Reprinted with permission from [90].…”

Extreme ultraviolet lithography with table top lasers

“…The larger exposure time might be an explanation for the lower quality printing because vibrations during the exposure significantly contribute to the image deterioration. In addition the print quality may possibly be affected by photoresist scumming that is particularly severe in 50% duty cycle lines with line widths approaching 50 nm, particularly for the HSQ photoresist [92]. The optical quality of the beam splitter and the folding mirrors is also a possible reason for the increased noise in the lines printed with this interferometer.…”

Simple fabrication of UV nanoimprint templates using critical energy electron beam lithography

“…Willson and co-workers 11,12 used very thin chromium to decrease the etch bias. As another approach to solving the pattern distortion by charge accumulation and CD loss, Mancini et al 13,14 used additive electron beam patterning of hydrogen silsesquioxane ͑HSQ͒ on top of indium tin oxide ͑ITO͒ coated quartz substrates. The ITO film was deposited as a charge dissipation layer and could be integrated within the template structure because of its UV transparency.…”