Dual-frequency CH2F2/H2/Ar capacitively coupled plasma를 이용한 실리콘질화물과 ArF PR의 무한 선택비 식각 공정

Abstract

Process window for infinite etch selectivity of silicon nitride (Si3N4) layers to ArF photoresist (PR) was investigated in dual frequency superimposed capacitive coupled plasma (DFS-CCP) by varying the process parameters such as low frequency power (PLF), CH2F2 and H2 flow rate in CH2F2/H2/Ar plasma. It was found that infinite etch selectivities of Si3N4 layers to the ArF PR on both blanket and patterned wafers can be obtained for certain gas flow conditions. The etch selectivity was increased to the infinite values as the CH2F2 flow rate increases, while it was decreased from the infinite etch selectivity as the H2 flow rate increased. The preferential chemical reaction of the hydrogen with the carbon in the polymer film and the nitrogen on the Si3N4 surface leading to the formation of HCN etch by-products results in a thinner steady-state polymer and, in turn, to continuous Si3N4 etching, due to enhanced SiF4 formation, while the polymer was deposited on the ArF photoresist surface.