EUV lithography has been realized to use the mass production. Therefore, the greatest interest of the EUV lithography is sub 10nm resolution patterning capability using high NA optics system. Currently, some of the new resist platform have been investigated and metal oxide resist and dry film resist were particularly achieved good patterning performance and etching durability as negative type resist by using metal component in the systems. Previously, we proposed a novel positive tone organometal chemically amplified resist by making dissolution contrast though chain scission and polarity change to develop for nonpolar solvent. After some modification of the resist material, we demonstrate positive and negative tone pattering by using 125keV EB drawing system with alkyl acetates as developers. We will share some of the progress to improve sensitivity and resolution of positive and negative tone organometallic resist in the conference.
While metal oxide resists showing good patterning performance and etching durability have been developed for a next generation resist as negative type resist, high performance positive tone resists are still needed for logic device manufacturing. We recently developed an organometal resist based on polarity change and chain scission, which resolved 22nm HP L/S pattern in EB drawing. However, it has some problems including film thickness loss and scum formation after development in the unexposed and exposed area, respectively. In this work, to resolve these problems, we attempted modification of our polymer-type resists in terms of chemical reactions that occurs in the exposed area. The results were discussed from their dissolution behavior by QCM method and printability by EB patterning. We found that newly designed anion D improved dissolution rate of exposed area and suppressed scum formation in exposed area. Our resist in this work resolved less than 20nm line and space patterns by such alkyl acetates as butyl acetate and PGMEA as developers.
A single-component silsesquioxane (SQ)-based material was developed and investigated for patterning in extreme ultraviolet (EUV) lithography. This negative-tone SQ-material is soluble in the industry standard aqueous alkali developer 2.38wt% tetramethylammonium hydroxide (TMAH). Early experiments using electron beam (EB) lithography showed pattern capability in resolving 18nm line patterns (exposure dose: 2000 μC/cm2). After numerous screening evaluations using EB lithography, one variant was selected for patterning evaluation with EUV lithography. Patterning resolution was confirmed at 19nm line patterns (exposure dose: 200 mJ/cm2), with evidence of pattern modulation down to 15nm. As revealed in these preliminary patterning investigations, low sensitivity is the obvious issue. To understand the reaction mechanisms of this SQ-based material, various analyses were also carried out. Results reveal the occurrence of direct photo-crosslinking (no main scission) of Si-O-Si bonds from the decomposition of Si-OH components on exposure, resulting in insolubility in the developer solution (negative tone). Lastly, to address the sensitivity issue, the application of what we refer to as “Sensitivity Enhancer Unit” was utilized. EB lithography results show an improvement in sensitivity indicating a possible solution to the low sensitivity issue. These results show the potential applicability of the single-component SQ-based patterning material for both EUV and EB lithography.
Electron beam (EB) lithography is indispensable for the fabrication of photomasks including extreme ultraviolet masks. With the miniaturization of electronic devices, the requirement for photomasks becomes severe. When the feature size was decreased, the resist patterns collapse due to the surface tension of liquid. The decrease of resist film thickness is required for the high-resolution patterning in order to avoid pattern collapse. However, the quality of resist patterns is known to be degraded.
In this study, the resist film thickness dependence of the pattern formation of a chemically amplified electron beam resist on chromium nitride substrate was investigated.
The transistors have been miniaturized to increase their integration. With the miniaturization, the thickness of resist has been decreased to prevent them from collapsing. In this study, the resist thickness dependence of the pattern formation of a chemically amplified electron beam resist was investigated. The line width roughness (LWR) of resist patterns increased with the decrease of initial resist film thickness. It was found that the dissolution kinetics depended on the initial resist film thickness. The escape of low-energy electrons to the substrates is considered to have resulted in the difference in the dissolution kinetics and LWR
The photo-mask in lithographic process of semiconductor device has an important role to transfer the downsized target image to the wafer. Due to the development of information society, demand for semiconductor devices has been growing. In order to increase photo-mask manufacturing throughput, the current density of electron beam (EB) has been getting higher. EB exposure increases the resist temperature on mask substrate inhomogeneous depending on its current density, shot size, writing order and etc. It is known that the resist sensitivity increases with irradiated resist temperature (heating effect). So, inhomogeneous temperature increase of resist on mask substrate disturbs precise pattern formation. However, the physical or chemical mechanism of heating effect has been still unknown. Here, we examined temperature dependence of acid generation process in chemically amplified resists (CARs). Poly(4- hydroxystyrene) (PHS) and poly(4-[(tert-butoxycarbonyl)oxy]styrene-co-4-hydroxystyrene) (PTBSHS) were used as CAR resin. Monte Carlo simulation moving thermalized electron under the electric field between polymer radical cations were performed with changing the temperature. From the simulation, it was revealed that the energy increase of thermalized electron contributes to the acid yield by 0.038 %/K. Quantification of the acid yields in resist films upon exposed to EB were performed with changing the temperature by titration method using Coumarin 6 (C6) as an acid sensitive dye. The acid yield increased by 0.14 %/K in PHS film and 0.21 %/K in PTBSHS film, respectively. Both values were higher than the simulation value (0.038 %/K). Pulse radiolysis experiment was also performed to observe deprotonation of polymer radical cations at 298 and 343 K. The decay of dimer radical cation of PTBSHS became 1.6 times faster at 343 K than that at 298 K. From the results, it is suggested that the heating effect mainly caused by the temperature dependence of deprotonation rate from the radical cations of PTBSHS.
Ionizing radiations such as extreme ultraviolet (EUV) and electron beam (EB) are the most promising exposure source for next-generation lithographic technology. In the realization of high resolution lithography, it is necessary for resist materials to improve the trade-off relationship among sensitivity, resolution, and line width roughness (LWR). In order to overcome them, it is essential to understand basic chemistry of resist matrices in resist processes. In particular, the dissolution process of resist materials is a key process. Therefore, it is essential for next-generation resist design for ionizing radiation to clarify the dissolution behavior of the resist film into developer. However, the details in dissolution process of EUV and EB resist films have not been investigated thus far. In this study, main chain scission and dissolution behavior of poly(methyl methacrylate) (PMMA) as main chain scission type resist was investigated using quartz crystal microbalance (QCM) method and gel permeation chromatography (GPC) in order to understand the relationship between the degree of PMMA degradation and dissolution behavior. The relationship between the molecular weight after irradiation and the swelling behavior was clarified.
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