Effects of gas flow rate on the etch characteristics of a low-k sicoh film with an amorphous carbon mask in dual-frequency CF4/C4F8/Ar capacitively-coupled plasmas

Abstract

Highly selective nanoscale etching of a low-dielectric constant (low-k) organosilicate (SiCOH) layer using a mask pattern of chemical-vapor-deposited (CVD) amorphous carbon layer (ACL) was carried out in CF4/C4F8/Ar dual-frequency superimposed capacitively-coupled plasmas. The etching characteristics of the SiCOH layers, such as the etch rate, etch selectivity, critical dimension (CD), and line edge roughness (LER) during the plasma etching, were investigated by varying the C4F8 flow rate. The C4F8 gas flow rate primarily was found to control the degree of polymerization and to cause variations in the selectivity, CD and LER of the patterned SiCOH layer. Process windows for ultra-high etch selectivity of the SiCOH layer to the CVD ACL are formed due to the disproportionate degrees of polymerization on the SiCOH and the ACL surfaces.