High sensitivity nonchemically amplified molecular resists based on photosensitive dissolution inhibitors

Abstract

A new class of nonchemically amplified molecular resists has been made based on the use of photosensitive protecting groups. The deprotection during exposure converts a dissolution inhibiting compound into a dissolution promoter. The key benefit of the use of molecular resists in this application is that they can exhibit a sharp solubility transition with relatively low levels of deprotection. Two different inhibiting compounds were made that use a 2-nitrobenzyl protecting group; NBnDCh, an aliphatic molecular resist based on deoxycholic acid, and NBnHPF, based on an aromatic molecular resist containing two phenol groups. Blending these compounds with a calixarene dissolution promoter allowed the contrast and sensitivity of the resist formulations to be tuned. Contrast ratios as high as 27 and deep ultraviolet ͑DUV͒ sensitivities between 150 and 400 mJ/ cm 2 were obtained using NBnDCh. NBnHPF based systems not only showed somewhat lower contrasts but also exhibited much lower clearing doses of only 60 mJ/ cm 2 and smaller. One particular NBnHPF formulation possessed a sensitivity of 10 mJ/ cm 2 and a contrast of 8.3, and it was even possible to formulate one resist with an extremely low dose-to-clear value of only 1 mJ/ cm 2 . Such low dose-to-clear values in nonchemically amplified resists have, to the authors' knowledge, not been reported before. The Dill C parameter for each of the two systems was quantified using Fourier transform infrared spectroscopy. The sensitivity of the NBnHPF systems was found to be very good because they undergo a solubility transition at 75 mol % inhibitor; this means that some formulations only need 0.5% photoconversion to pattern. Despite the excellent DUV sensitivity of these systems, it was found that they do not possess high sensitivity when exposed using extreme ultraviolet or e-beam exposure sources.

Fast simulation of stochastic exposure distribution in electron-beam lithography

“…One of the approaches to modeling the LER, which can lead to realistic results, is to employ the Monte Carlo simulation [18][19][20] in obtaining the stochastic distribution of exposure in the resist layer. Then, the LER is estimated from the remaining resist profile derived through the simulation of developing process.…”

New non-chemically amplified molecular resist design with switchable sensitivity for multi-lithography applications and nanopatterning

“…However, most of the existing polymers are reaching to their resolution limit beyond 20 nm node mainly because of their large intermolecular chain entanglement, which eventually leads to the internal stress or swelling induced pattern collapse at lower nodes [2,[12][13][14]. To address these issues, attention has been focused on the development of molecular resists with smaller size (3-5 nm) and improved properties like monodispersity, unique dissolution behaviour and smooth thin film formations as compared to the polymers [2,[15][16][17][18][19][20][21][22][23]. In addition, line edge roughness (LER) is a critical parameter for higher resolution patterning applications.…”

Polyarylenesulfonium Salt as a Novel and Versatile Nonchemically Amplified Negative Tone Photoresist for High-Resolution Extreme Ultraviolet Lithography Applications

“…However, traditionally used chemically amplified resists (CARs) that depend on blended or polymer-bound photoacid generators (PAGs) , for achieving solubility differentiation are often associated with inherent problems such as high line edge roughness (LER), line width roughness (LWR), low sensitivity, post exposure instability, and process complexity for high-resolution patterning applications. − Therefore, increased attention is now being focused on the development of novel nonchemically amplified resists (n-CARs) to meet the targets set by ITRS-2015. n-CARs are materials that are directly sensitive to radiation and do not require PAGs in their formulation. , In this context, a wide range of novel organic, inorganic, organometallic, and hybrid resists have been developed in recent years for high-resolution lithography applications. − Nevertheless, the number of organic polymer based n-CARs is highly limited compared to the number of CARs reported to date. Therefore, the development of high-end organic polymer-based n-CARs with strong lithographic potentials is highly important, especially for sub-20 nm patterning applications with low LER/LWR features.…”