Nanometer-Sized Etching of Polysilicon Thin Films in a High Density Plasma

초록

Intensive researches on nonvolatile semiconductor memories (NVSMs) have been performed for the development of new memories for the next generation. NVSM with the polysilicon oxide nitride oxide silicon (SONOS) structure is proposed as a viable candidate over the floating-gate structure. The polysilicon thin films are used as the gate metal, and SiO2 and Si3N4 are employed as the gate dielectrics. Among the various process technologies required to realize this novel device, the nanometer-sized patterning of gate polysilicon is one of the key technologies to be developed for the fabrication of the SONOS device. In this study, nanometer-sized patterning of polysilicon thin films has been carried out using high density inductively coupled plasma system. The gas chemistries for the etching are chlorine-based and bromine-based gases and the process parameters are coil rf power, chamber pressure and dc-bias to wafer susceptor. The etch rate and etch selectivity as well as the etch profile of polysilicon and silicon dioxide are examined using various etch chemistries and etch parameters. Nanometer-sized etching of 30~90 nm on the polysilicon thin films masked with only e-beam resist or with hard mask is attempted by optimizing the etch gases and process parameters.