Top Surface Imaging

The top surface imaging process being studied in this project is a modification of the chemical amplification scheme.  It utilizes the same coating and exposure technology, but the steps that follow are much different than those used in traditional lithography processes, as shown below (with TBOC-Styrene as an example).
Figure 1: Silylation Lithographic Scheme

After the traditional exposure and bake processes, the next step is to silylate the photoresist. The resist is placed in a silylation chamber where it is exposed to the vapor of a reactive, silicon containing agent. The alcohol groups in the exposed regions of the resist can react with the silylating agent while the TBOC groups in the unexposed region cannot. The silylation of the phenolic functionality is shown below in the poly(hydroxystyrene) system, using dimethylsilyldimethylamine (DMSDMA):
The result of the silylation reaction is to incorporate silicon atoms exclusively into the exposed region of the photoresist. Many different polymer structures and silylation agents may be used.
The next step is to place the wafer into an oxygen plasma tool (reactive ion etcher) to develop the images. In the presence of an oxygen plasma, the silicon-containing regions oxidize to form a thin layer of SiO2 at the top of the resist. The SiO2 acts as an etch barrier and protects the underlying photoresist and substrate. In the regions where there has been no silicon atom incorporation, the oxygen plasma completely oxidizes the resist to carbon dioxide and water, which are pumped from the system.
Background on Thin Layer Imaging (click here for more details)