Highly Selective Plasma Etching Technique for Molybdenum

This work presents the results of the study of plasma-chemical etching of molybdenum in SF 6 inductively coupled plasma using a photoresist mask. The dependences of etching rate and selectivity on high-frequency (HF) power, pressure and temperature of the substrate holder are determined. It is shown that increasing the pressure from 1.5 to 3.5 Pa insignificantly decreases the etching rate of molybdenum and does not change the etching rate of photoresist. Changing the HF power from 500 to 1500 W leads to a significant increasing not only the molybdenum etching rate, but also the photoresist etching rate and, consequently, to decreasing the etching selectivity of molybdenum in relation to photoresist mask. It is determined that changing the temperature of the substrate holder in the range from − 28 to 40 °C leads to gradual increasing the etching rate of molybdenum and does not affect the etching of photoresist. Thus, the optimal ratio of technological parameters was selected in terms of achieving the highest molybdenum etching rate with maximum etching selectivity. Using the developed technology of ultra-selective etching, the removal of molybdenum film with a thickness of 200 nm was performed without reducing the thickness of the photoresist.