Toshiba has developed a high resolution photoresist (photo-sensitive film) essential for future application of EUV (extreme ultraviolet) lithography in semiconductor fabrication, and proved its viability with the world's first 20nm-scale generation process technology.

This achievement will be announced at 22nd International Microprocesses and Nanotechnology Conference on November 19.

When semiconductors circuit patterns scale down into the 20nm-scale generation, current photoresists will no longer resolve circuit patterns precisely, resulting in roughness in pattern sidewalls. The biggest factor is that conventional photoresists consist of polymer compounds. While such compounds are easier to spin-cast on wafers, the size of their molecules and entangling of their molecular chains limit resolution. To overcome this, Toshiba has developed a photoresist with smaller molecular compounds.

Once a photoresist is exposed to light, it is removed from the substrate with a developer solution in one of two ways, positive tone and negative tone. In positive-tone development, the area exposed to the light source is removed from the wafer (i.e. that part of the photoresist becomes more soluble), leaving a channel. In negative-tone development, the area that has not been exposed to the light source is removed from the wafer (i.e, that part of the photoresist becomes more soluble), leaving a raised area. Application of both processes is essential for etching wafers.

Toshiba identified truxene, a material with a fine, durable structure, as a candidate material. The company has established the fundamental composition of a truxene derivative for photoresist, and demonstrated its use as a positive-tone photoresist in EUV generation. Moving beyond this, Toshiba has now demonstrated its application as a higher resolution negative-tone photoresist in 20nm-scale generation. Photoresists must be able to support both positive- and negative-tone processes in the lithography process, and Toshiba has how established basic technology for both.

Toshiba said it would further improve the performance of the molecular resist and apply it to the fabrication of 20nm-scale generation LSIs. According to the International Technology Roadmap for Semiconductors (ITRS), high volume production of this generation is expected to start in 2013.