Acid diffusion during the post-exposure bake of chemically amplified resists (CARs) is a major contributing factor to
line width roughness (LWR) and resolution limits at the 32 nm node and beyond. To overcome these limitations,
non-CAR materials are becoming more attractive because acid diffusion is eliminated. We have therefore focused our
effort on the synthesis of copolymers that have both a diacyldiazo side chain unit as well as a hexafluoroalcohol unit.
This copolymer shows better contrast than that of copolymers containing lactone units due to their inhibition behavior.
Furthermore, polymer blends containing hexafluoroalcohol groups show good 100 nm line and space patterning property
for 193 nm lithography. This paper describes the design, synthesis, and characterization of these non-CARs, and thier
improvement to photolithography.
ArF immersion lithography using water as a fluid medium enables production of 45 nm features. Extending immersion lithography to 32 nm or below requires increases in the refractive indices of the lens material, the immersion fluid, and the resist material. However, a material with a high refractive index generally also has high absorbance. In attempt to design a resist with high refractive index and low absorbance, we studied several types of sulfur-containing polymers and determined which sulfur groups increase the refractive index without increasing the absorbance at 193 nm. We describe new thioester and sulfone structures that enable high index with low absorbance. This chemistry has been exploited to produce polymers with a refractive index of 1.8 at 193 nm and an absorbance less than 1.4 &mgr;m-1. The compatibility of the sulfur functionality with chemically amplified imaging chemistry was demonstrated by printing at 193 nm.
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.