For patterning organic resists, optical and electron beam lithography are the most established methods; however, at resolutions below 30 nanometers, inherent problems result from unwanted exposure of the resist in nearby areas. We present a scanning probe lithography method based on the local desorption of a glassy organic resist by a heatable probe. We demonstrate patterning at a half pitch down to 15 nanometers without proximity corrections and with throughputs approaching those of Gaussian electron beam lithography at similar resolution. These patterns can be transferred to other substrates, and material can be removed in successive steps in order to fabricate complex three-dimensional structures.
The success of the semiconductor industry is based on the ability to fabricate hundreds of millions of devices on a single chip. In order to fulfill the ever‐shrinking feature sizes, the industry requires new patternable materials in order to operate in the sub‐50 nm regime. Molecular glass (MG) resists are a new type of patterning material that has gained considerable attention over the past few years. This Research News article describes the chemical and structural aspects of MGs as well as important concepts of MG resist design. We also highlight some of the recent advances in high‐resolution patterning capabilities with next‐generation imaging tools.
Selective area atomic layer deposition (SA-ALD) offers the potential to replace a lithography step and provide a significant advantage to mitigate pattern errors and relax design rules in semiconductor fabrication. One class of materials that shows promise to enable this selective deposition process are self-assembled monolayers (SAMs). In an effort to more completely understand the ability of these materials to function as barriers for ALD processes and their failure mechanism, a series of SAM derivatives were synthesized and their structureproperty relationship explored. These materials incorporate different side group functionalities and were evaluated in the deposition of a sacrificial etch mask. Monolayers with weak supramolecular interactions between components (for example, van der Waals) were found to direct a selective deposition, though they exhibit significant defectivity at and below 100 nm feature sizes. The incorporation of stronger noncovalent supramolecular interacting groups in the monolayer design, such as hydrogen bonding units or pi–pi interactions, did not produce an added benefit over the weaker interacting components. Incorporation of reactive moieties in the monolayer component that enabled the polymerization of an SAM surface, however, provided a more effective barrier, greatly reducing the number and types of defects observed in the selectively deposited ALD film. These reactive monolayers enabled the selective deposition of a film with critical dimensions as low as 15 nm. It was also found that the selectively deposited film functioned as an effective barrier for isotropic etch chemistries, allowing the selective removal of a metal without affecting the surrounding surface. This work enables selective area ALD as a technology through (1) the development of a material that dramatically reduces defectivity and (2) the demonstrated use of the selectively deposited film as an etch mask and its subsequent removal under mild conditions.
Our approach to determine reaction-diffusion parameters uses reflection-based Fourier transform infrared (FTIR) spectroscopy. The choices of spectroscopic bands that quantify the extent of film reaction are described in Section 2.3. Since FTIR provides a film-average is quantitative for photoacid generator-containing (PAG) single-layer films where the reaction is treated as uniform. For the bilayer films, there is extra reaction as the acid-containing layer reacts, but additional reaction takes place by photoacid diffusion into the PAG-free bottom layer. This scheme was referred to as the one-dimensional gradient methodology with the sample preparation provided in detail in Section 2.2. The experimental approach to normalize the deprotection extent for singlelayer and bilayer measurements was described in detail in Section 2.4. Following the experimental procedures of ultraviolet light exposure to photo-initiate all PAG, we convert the known-formulation concentration into photoacid 1,2. Therefore, the experimental results provide measures of film deprotection extent versus PEB time. These measurements are interpreted by a reaction kinetics model using both single-layer and bilayer experiments. The data analysis is provided in detail below that are only coupled partial differential equations that are evaluated by widely-available scientific software. The overall summary of the sample preparation, measurement, data analysis and modeling is provided in Figure S1.
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