Organoiodine Functionality Bearing Resists for Electron-Beam and Helium Ion Beam Lithography: Complex and Sub-16 nm Patterning

Abstract

Given the current need for resist materials for patterning transistors with ultralow nodes, there has been a quest for developing resists with improved performance for nanoscale patterning with good contrast. The present work demonstrates polymeric resists (MAPDST-TIPMA) developed through the integration of a radiation-sensitive monomer (MAPDST) with an organoiodine functionality (TIPMA) for sub-16 nm patterning using electron-beam and helium ion beam lithography. The structural integrity was established by several spectroscopic techniques particularly NMR, FTIR, XPS, and GPC. These polymeric resists possess weight-average molecular weight (M w) in the range of 10000–12000 with low PDI. While the resists 3a and 3b were synthesized with feed ratios of 80:20 and 70:30 of the monomers MAPDST and TIPMA, respectively, the actual microstructure compositions were calculated, using XPS and GPC data, to be ∼94:6 and 91:9, respectively. The present resists have the potential for patterning 16 nm line/space features when exposed to e-beam. Also, 15 nm features were successfully patterned using MAPDST-TIPMA resists. The line edge roughness (LER) and line width roughness (LWR) of the 20 nm L/3S features were calculated to be 2.48 and 3.6 nm, respectively. Moreover, complex nanofeatures of different shapes were successfully patterned using 3b. A critical analysis of nanofeatures using AFM revealed that the patterns are very well developed with a sharp wall profile. The normalized resist thickness (NRT) curve was established to evaluate the sensitivity of the present resist which was calculated to be 341 μC/cm2 at 20 keV. The nature and slope of the NRT curve indicated that MAPDST-TIPMA is a negative tone resist with good contrast. Finally, the resist was found to be highly sensitive to He+ beam (sensitivity ∼6.21 μC/cm2) resulting in 20 nm L/S as well as 15 nm features with a good wall profile.

Sulfonium-Functionalized Polystyrene-Based Nonchemically Amplified Resists Enabling Sub-13 nm Nanolithography

“…In the past decades, the miniaturization and improvement of electronic devices were mainly enabled by the rapid development of lithography technology and the improvement of resist performance . Electron beam lithography (EBL) and extreme ultraviolet lithography (EUVL), as the most advanced high-resolution lithography technologies, are widely used in research and high-volume production for feature sizes lower than 20 nm half-pitch (HP). − Accordingly, the development of resist materials fulfilling the stringent requirements of high resolution ( R ), sensitivity ( S ), and low line edge roughness (LER) is still a great challenge for advanced lithography. ,, Although traditional chemically amplified resists (CARs) have been widely used in the semiconductor industry due to their high sensitivity, the stochastic distribution of photoacid generators (PAGs) and the diffusion of acids in the resist film result in poor LER and limit the resolution of CARs. ,, To overcome these limitations, researchers have proposed methods to accomplish the uniform distribution of PAGs and diffusion minimization of acids in a resist film. , It has been demonstrated that incorporating the PAGs into the polymer backbone and increasing the volume of anions of PAG can effectively improve the uniformity of PAG distribution and control the acid diffusion. − However, as the feature size becomes smaller and smaller, it is difficult to achieve the required resolution due to the acid diffusion blur, which is intrinsic for CARs.…”

“…At present, various types of n-CARs containing various radiation-sensitive groups, e.g., sulfone, , carbonate, , Sn–C bond, oxalate, and sulfonium groups, ,− have been reported. The resolution of resist materials containing sulfone, carbonate, , and oxalate was demonstrated to be around 20–30 nm.…”

“…A high-resolution pattern with a line width of 15 nm at a 1:15 pitch ratio and a linewidth of 20 nm at a 1:1 pitch ratio was successfully fabricated by EBL. A series of novel negative-tone copolymer resists bearing a radiation-sensitive sulfonium functionality have been studied by Gonsalves’ group in recent years. , Line patterns (12.3 nm) were achieved at a dose of 400 μC cm –2 , and well-developed sub-15 nm line patterns of a low LER of ∼1.29 nm were achieved by using EBL at an e-beam energy of 20 keV. Furthermore, the sensitivity of the resist can be modulated by changing the tin content in the copolymer.…”

A novel dual-tone molecular glass resist based on adamantane derivatives for electron beam lithography

“…Finally, the phenolic hydroxyl groups of AD-10OH were protected with the t-Boc group in the presence of 4-dimethylaminopyridine, which provided monodisperse AD-10Boc in an 81% yield. Formation of the final product AD-10Boc was confirmed by 1 H NMR, 13 C NMR, FT-IR, and high-resolution ESI-TOF mass spectra, which are displayed in Fig. S5-S8 (ESI †).…”

“…However, it is still a challenge to develop resist materials fulfilling the requirements such as high sensitivity and low line-edge roughness (LER) simultaneously. [13][14][15] The commercially available non-chemically amplified resists (n-CARs), poly(methyl methacrylate) (PMMA) and hydrogen silsesquioxane (HSQ) achieved sub-10 nm patterns at the expense of high exposure dose. 2,3,[16][17][18][19][20] Gonsalves et al designed a nonchemically amplified polymeric hybrid resist based on the radiation-sensitive sulfonium functionality and organotin.…”