Liquid-phase silylation characterisation of Shipley SPR500A-series resists using PRIME Top Surface Imaging process

Top Surface Imaging (TSI) is a well-established technique used to improve resolution for optical, ultraviolet and electron-beam lithography. The Positive Resist Image by Dry Etching (PRIME) [1] is an advanced lithographic process incorporating electron beam exposure, near UV flood exposure, silylation and dry development. In this paper, the liquid-phase silylation process step in PRIME with Shipley SPR500A-series resists has been experimentally investigated as the most critical part of the process. FT-IR spectroscopy, UV spectroscopy, SIM spectrometry and crosssectional SEM and TEM were used to characterise the silylation process. Electron-beam exposure with dose in the range of 25-100muC/cm(2) at 30KeV was used to crosslinks the resist. Results show that an e-beam dose of 50muC/cm(2) was sufficient to prevent. silylation in the crosslinked areas. Two bifunctional silylating agents, the cyclic Hexamethylcyclotrisilazane (HMCTS) and the linear Bis[Dimethylamino] dimethylsilane (B[DMA]DMS), were examined and found that they silylate SPR505A much more efficiently than the previously reported Hexamethylcyclotrisiloxane (HMCTSx). The silylation contrast of the PRIME process using HMCTS silylating agent and SPR505A resist was found to be 11:1. The obtained silylated profiles of 1mum lines/spaces gratings for Shipley SPR510A resist have almost vertical sidewalls resulting in very high contrast between the silylated and unsilylated parts of the resist.