Lithography options for the 32nm half pitch node and beyond

There are still three major technological lithography options for high volume manufacturing at the 32 nm half pitch node: 193 nm immersion lithography with high index materials, enabling NA > 1.6; 193 nm double patterning and EUV lithography. In this paper the pros and cons of these three options are discussed. The extendibility of these options beyond 32 nm half pitch is important for the final choices to be made. High index 193 nm immersion lithography requires high index resist materials, which are under development but still far removed from the target refractive index and absorbance specifications and not to mention lithographical performance. For double patterning the pitch may be relaxed, but the resists still need to be able to print very narrow lines and/or trenches. Moreover, it is preferred for the resists to support pattern or image freezing techniques in order to step away from the litho-etch-litho-etch approach and make double patterning more cost effective. For EUV, besides the high power light source, the resist materials need to meet very aggressive sensitivity specifications. In itself this is possible, but it is difficult to simultaneously maintain performance in terms of resolution and line width roughness.