Technologischer Einsatz von Jodwasserstoff-Plasmen für die Polysilicium-Gate-Strukturierung in einer Sub-Quarter-Micron-Technologie
Dry etching has become an essential tool for transferring mask patterns in sub-quarter-micron technology. In MOS technology the minimum feature size is determined by the polysilicon gate length. Therefore, strict requirements are being imposed on etching. Applications such as dry etching of polysilicon gates require etch processes with high selectivity, anisotropic profiles, and minimal charge damage of gate oxide.
This work investigates the application of a novel chemistry hydrogen iodide for patterning of polysilicon gates. To characterize the hydrogen iodide plasma optical emission spectroscopy and self excited electron plasma resonance spectroscopy are used. These investigations have the aim to determine internal plasma parameters and furthermore using these methods for process control. Plasma damage during dry etching is characterized by x-ray photoelectron spectroscopy and photoluminiscence.
Keeping these results in mind a dry etch process based on hydrogen iodide is developed for polysilicon gate etching in 0.18 μm technology. Etching is also performed in hydrogen bromide and hydrogen chloride plasmas for comparing the results. The investigations show using hydrogen iodide for polysilicon gate patterning we achieve a higher selectivity of polysilicon to oxide. Without any passivation gases an anisotropical profile is achievable. To investigate possible plasma damage during etching electrical measurements are performed at MOS structures. The results show, there is an interaction between plasma damage and the chemistry used.
Hydrogen iodide is an alternative to conventional chlorine and bromine chemistries. Hydrogen iodide based etching satisfies all demands for polysilicon gate etching in advanced technologies, and this new etch chemistry makes low-damage etching (compared to conventional chemistries) possible.