Three-dimensional pattern transfer on quartz substrates

Abstract

This paper describes a single-step pattern transfer process for three-dimensional (3D) structures onto quartz substrates. The 3D patterns were defined on a negative resist (ma-N2403) using variable controlled acceleration voltage in the electron beam lithography (EBL) process. The developed 3D patterns on the negative resist were utilized as the masking layer and later transferred onto quartz substrate by employing fluorinated plasma etching process. The etching chemistry of CHF 3 plasma on both 3D masking layer and quartz substrate was analysed to guide etching process optimization. The 3D etching mechanism was also analysed to help in achieving the desired final 3D pattern profiles for imprint process. The causes of surface roughness formation were analysed and appropriate remedies were suggested. The Oxford Plasmalab 80plus etcher was employed for transferring the 3D patterns on quartz substrate using a gas mixture of CHF 3/Ar with a ratio of 9.0/6.25 sccm, etching pressure of 5 mTorr, RF power of 125 W and at room temperature. This setting was found to achieve a 10 nm/min etch rate, better control of 3D profiles and surface roughness of less than 2 nm.