Resist heating effects in 25 and 50 kV e-beam lithography on glass masks

Abstract

Electron sensitive resists have been exposed on optical masks in a variably shaped spot electron beam lithography system, EL3, at 25 and 50 kV and beam current densities up to 50 A/cm2 to evaluate the effects of resist heating during electron exposure. Resist heating effects are primarily observed in dense patterns at high electron exposure dose. For the purpose of comparison resist heating effects are quantified in terms of the development rate change that is caused by the temperature rise in the resist during electron beam exposure. From an energy density point of view the maximum temperature rise in the resist during exposure is very similar for both 25 and 50 kV exposures. The area on the mask over which the temperature rise in the resist can change resist properties is significantly larger at 50 kV: up to 20 μm at 50 kV compared to ∼5 μm at 25 kV. Using sensitive electron beam resists requiring 1–5 μC/cm2 exposure dose no resist heating effects are observed at beam current densities up to 50 A/cm2.

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

“…Resist temperature during exposure has been reported to have a substantial influence on sensitivity for the variety of both positive and negative tone electron beam resist materials. [5][6][7][8] Thermal effects were reported either as a consequence of high current exposure or by applying well-defined substrate temperature variation by using a heated/cooled chuck. It is the latter approach we adopt in this work as it enables to study more accurately the high resolution capabilities under impact of the temperature during exposure.…”

Submicron thermocouple measurements of electron-beam resist heating

“…1 Pattern distortion caused by the resist heating due to electron-beam energy deposition can be a major contributor to errors in feature size and pattern placement. [2][3][4] We have developed an analytical model employing multilayer Green's functions, which facilitates computation of four-dimensional temperature distributions in space and time. 5 In prior work there have been different simplifications to facilitate computation for multilayer structures.…”

Localized resist heating due to electron-beam patterning during photomask fabrication

“…An increased sensitivity means that it now requires fewer electrons (lower dose) to develop the same resist. Due to this increased sensitivity in the surrounding areas, unexpected development of the resist may occur 11,14,15 .…”