Paper PS2+MN-WeA9
Infinitely High Etch Selectivity and Variation of Line Edge Roughness during Etching of Hard-Mask Layer with Patterned Extreme Ultra-Violet

Wednesday, November 11, 2009, 4:40 pm, Room B2

In the nano-scale Si processing, patterning processes based on multilevel resist structures becoming more critical due to continuously decreasing resist thickness and feature size. In particular, highly selective etching of the first dielectric layer with resist patterns and control of critical dimension (CD) and ling edge roughness (LER) are of great importance. In this work, process window for the infinitely high etch selectivity of silicon oxynitride (SiON) layers to EUV resist and variation of LER of extreme ultra-violet (EUV) resist was investigated during etching of SiON/EUV resist in a CH₂F₂/N₂/Ar and CH₂F₂/N₂/O₂/Ar dual-frequency superimposed capacitive coupled plasma (DFS-CCP) by varying the process parameters, such as the CH₂F₂ and N₂ flow ratio, low-frequency source power (P_LF) and O₂ flow rate. It was found that the CH₂F₂/N₂ flow ratio was found to play a critical role in determining the process window for infinite SiON/EUV resist etch selectivity, due to the differences in change of the degree of polymerization on SiON and EUV resist. Control of N₂ flow ratio gave the possibility of obtaining the infinitely high etch selectivity by keeping the steady-state hydrofluorocarbon layer thickness thin on the SiON surface due to effective formation of HCN etch by-products and, in turn, in continuous SiON etching, while the hydrofluorocarbon layer is deposited on the EUV resist surface. On the other hand, CD size and LER tend to increase with increasing CH₂F₂/N₂ flow ratio.