Attenuated phase shift masks using MoSi as an opaque layer

The use of phase shifting masks (PSM) causes revolutionary improvements of the performance of existing wafer steppers. Nowadays the attenuated PSM, also referred to as halftone, is found to be most attractive, as the technique is self aligned. Moreover, the number of additional process steps in mask fabrication is limited to a dry etching step. As linewidths on mask shrink towards 1 μm (a critical dimension of 0.2 μm, at 5× magnification) and below, the required CD control becomes much tighter. Sputtered molybdenum silicide (MoSi) is easier to dry etch than chrome and is therefore an important candidate as alternative opaque material on masks. This paper will discuss the use of MoSi for attenuated PSMs. This approach has the advantage over the use of an SOG/Cr combination, that only a single dry etch process is required