Comparison of single-, bi-, and tri-layer resist process

A comparison study of single-, bi-, and tri-layer resist (SLR, BLR, and TLR, respectively) process was investigated. The goal of this study is to clarify the advantage of each process for the pattern transfer etching process. Conventional ArF photoresist and bottom anti-reflective coating process were applied to SLR. Novel silsesquioxane (SSQ) resist and spin-on organic hard mask (SOHM) were used for BLR process. The SSQ consists of siloxane backbone which contains three components, protective group, solubility control group, and higher silicon containing group to increase etch selectivity to SOHM. The main polymer in SOHM contains naphthalene type unit, for both anti-reflective and etch-durable properties. SOHM layer is highly cross-linked film with more than 85wt% carbon content which contributes to higher etch selectivity. A conventional ArF photoresist as an imaging layer, spin-on glass (SOG) as an intermediate layer, and the SOHM as a bottom layer were applied to TLR process. Multi-layer materials of each process were spin-coated on the stacks of cap-oxide/low-k/SiC on Si substrate and exposed with ArF 0.75NA scanner for 100nm line and space imaging. SLR showed better lithographic performance than BLR and TLR. However after pattern transfer etching process into SiOC layer, the different performance among each process has been observed. SLR process after pattern transfer etching showed severe surface roughness, striation and line width roughness (LWR). On the other hand, BLR and TLR showed significant improvement of pattern transfer performance. Multi-layer process can improve LWR during etching process.