Patterning of the resist features down to 10 nm node is crucial for futuristic integrated circuits (ICs) technology advancements. In this regard, we design and developed a novel hybrid non-chemically amplified resist (n-CAR) i.e. MAPDST-co-ADSM (where MAPDST = (4-(methacryloyloxy)phenyl) dimethylsulfonium trifluoromethanesulfonate and ADSM = (acetyldibutylstannyl methacrylate)) for high-resolution Helium Ion (He+) Beam Lithography (HIBL) studies. The developed resist exhibits the high sensitivity toward Helium ion radiation and patterned sub-15 nm features at the dose ∼50 μC/cm2 onto negative tone resist formulation. In order to recognize the critical dimension (CD), the resist thin films were analyzed for single pixel exposure dose analysis at He+ exposure dose ranging from ∼30 pC/cm to ∼100 pC/cm. These investigations apparently reveal that 10 nm single pixel line features of the MAPDST-co-ADSM resist is patterned with the dose ∼50.48 pC/cm. The improved patterning resolution of the resist down to 10 nm is due to the inclusion of hybrid tin sensitizer in the resist structures. The MAPDST-co-ADSM showed coherent line edge roughness (LER) and line width roughness (LWR) values for 15 nm lines features as ∼1.67±0.27 nm and ∼2.20 nm respectively.
Monte Carlo-based simulation technique is a standard method for statistical analysis and modelling of stochastic processes; such as noise in circuits, carrier transport and study of ion implantation/interaction/trajectory on materials for integrated circuits. Thus Monte Carlo ion trajectory simulation for MAPDST-co-ADSM resist formulation showed that the negligible (∼0.5%) target damage and recoil generation (atom displacement) of total energy delivered to the system (MAPDST-co-ADSM/Si) in novel HIBL exposure due to much larger stopping power of He+ ion and low proximity effect.
Proc. SPIE. 10583, Extreme Ultraviolet (EUV) Lithography IX
KEYWORDS: Thin films, Lithography, Electron beam lithography, Atomic force microscopy, Line width roughness, Extreme ultraviolet lithography, Line edge roughness, Photoresist developing, Resolution enhancement technologies, Tin
MAPDST (4-(methacryloyloxy)phenyl)dimethylsulfoniumtrifluoromethanesulfonate)) based resist analogous are reported to pattern high-resolution nano features (20 nm) under wide range of lithography tools including electron beam lithography (EBL), extreme ultraviolet lithography (EUVL), 193 nm immersion lithography etc. However, these resists have not yet patterned lower node features, especially at sub-15 nm regime with ultra-low line edge roughness (LER) and line width roughness (LWR). One of the methods to improve the resolution of a resist is the structural modification. Towards this, we have developed two new hybrid copolymer resists i.e MAPDST-co-ADSM and MAPDST-co-TPMA by the copolymerization of radiation sensitive organic MAPDST with hybrid tin monomers ADSM and TPMA (ADSM = acetyldibutylstannyl methacrylate; TPMA = triphenyl tin methacrylate) for high-resolution EBL applications. The developed resists were studied for their sub-15 nm line patterns with low LER and LWR features. Various line features, starting from 30-12 nm with different line/space (L/S to L/10S) characteristics were studied at various e-beam doses 200- 1200 μC/cm2. Isolated 12 nm line features have been achieved with the resist MAPDST-co-ADSM at a dose 1200 μC/cm2. Meanwhile, the MAPDST-co-TPMA resist patterned 15 nm features at the dose 700 μC/cm2. The estimated sensitivity and contrast of resists MAPDST-co-ADSM and MAPDST-co-TPMA were 1.60; 450 μC/cm2 and 1.55; 380 μC/cm2 respectively. Similarly, the computed LER and LWR parameters exhibited by the resists MAPDST-co-ADSM and MAPDST-co-TPMA for sub-30 nm features were 0.99; 1.22 and 1.8; 3 nm respectively. The e-beam studies revealed a resolution enhancement of the hybrid resists at 12 nm regime as compared to the neat poly(MAPDST) resist (where the resist resolution was 20 nm) indicating improvements in the lithography properties of these resists.