Characteristics of Selective MoSiON Etching in a Chlorine Plasma

The etch characteristics of MoSiON were investigated when chlorine was utilized as the main etch gas in an ICP dry etch system. MoSiON and glass are easily etched with fluorine-based plasmas such as: CF 4, SF 6, and CHF 3. These plasma chemistries generate carbon-containing and fluorine-containing polymers as byproducts, which can be responsible for generating particles or hard defects on the mask during the MoSiON etch step. They also cause damage to the glass surface, manifesting themselves as a phase or transmission errors. In this paper, new plasma chemistry was applied to etch MoSiON, and its characteristics were examined focusing on the effects of each parameter. These parameters included: ICP power, bias power, pressure, and gas concentration. It is difficult to etch MoSiON with good selectivity to Cr because MoSiON and Cr can be etched simultaneously after the photoresist layer has been removed. It will be shown how to increase the selectivity to Cr using an optimized process leveraging a new hardware modification. The etch characteristics of the chlorine plasma will also be compared to that of fluorine plasmas. It was found that using a chlorine plasma to etch MoSiON instead of a fluorine plasma yields good etch properties and good morphology.