Polymer-supported Schiff base complexes in oxidation reactions

Historically, in the mass production of semiconductor devices, exposure tools have been repeatedly replaced with those with a shorter wavelength to meet the resolution requirements projected in the International Technology Roadmap for Semiconductors issued by the Semiconductor Industry Association. After ArF immersion lithography, extreme ultraviolet (EUV; 92.5 eV) radiation is expected to be used as an exposure tool for the mass production at or below the 22 nm technology node. If realized, 92.5 eV EUV will be the first ionizing radiation used for the mass production of semiconductor devices. In EUV lithography, chemically amplified resists, which have been the standard resists for mass production since the use of KrF lithography, will be used to meet the sensitivity requirement. Above the ionization energy of resist materials, the fundamental science of imaging, however, changes from photochemistry to radiation chemistry. In this paper, we review the radiation chemistry of materials related to chemically amplified resists. The imaging mechanisms from energy deposition to proton migration in resist materials are discussed.

https://iopscience.iop.org/article/10.1143/JJAP.49.030001/pdf

Radiation Chemistry in Chemically Amplified Resists

Au nanoparticles modified with electroactive Prussian blue (PB) were for the first time synthesized by a simple chemical method. Transmission electronic microscopy showed that the average size of the Prussian blue shell/Au core hybrid composite (PB@Au) was about 50 nm, and Fourier transform IR, UV−vis spectra, and cyclic voltammetry confirmed the existence of PB on the surface of Au nanoparticles. Using the LbL technique, multilayer thin films of PB@Au nanoparticles were prepared by the alternate adsorption of oppositely charged linear polyelectrolyte poly(allylamine hydrochloride) (PAH) onto ITO glass for the construction of a hydrogen peroxide sensor. The novel multilayer films were characterized by SEM, cyclic voltammetry, and UV−visible absorption spectroscopy. The {PAH/PB@Au}n multilayer-modified electrode showed a well-defined pair of redox peaks and dramatic catalytic activity toward the reduction of hydrogen peroxide.

Synthesis, Characterization, and Immobilization of Prussian Blue-Modified Au Nanoparticles: Application to Electrocatalytic Reduction of H2O2

Core/shell-type titania nanocapsules containing a single Ag nanoparticle were prepared. Ag nanoparticles were prepared using the reduction of silver nitrate with hydrazine in the presence of cetyltrimethylammonium bromide (CTAB) as protective agent. The sol-gel reaction of titanium tetraisopropoxide (TTIP) was used to prepare core/shell-type titania nanocapsules with CTAB-coated Ag nanoparticles as the core. TEM observations revealed that the size of the core (Ag particle) and the thickness of the shell (titania) of the core/shell particles obtained are about 10 nm and 5-10 nm, respectively. In addition, the nanocapsules were found to be dispersed in the medium as individual particles without aggregation. Moreover, titania coating caused the surface plasmon absorption of Ag nanoparticles to shift toward the longer wavelength side.

Preparation of highly dispersed core/shell-type titania nanocapsules containing a single Ag nanoparticle.

A positive resist composition having excellent size controllability, and a resist pattern forming method are provided. This positive resist composition contains a resin component (A) comprising an alkali soluble constituent unit (a1) which comprises a constituent unit (a11) derived from (α-methyl)hydroxystyrene, and a constituent unit (a2) which has an acid dissociable dissolution inhibiting group including an acid dissociable dissolution inhibiting group (II) represented by the following general formula (II) and/or a specific chain acid dissociable dissolution inhibiting group (III); an acid generator component (B) which generates an acid upon exposure; and preferably contains an aromatic amine (C).

Positive resist composition and resist pattern forming method

A guideline for evaluating LER and total procedure to estimate effects of measured LER on device performance were proposed. Spatial-frequency distributions of LER in various resist materials were investigated and general characteristics of spatial-frequency distribution of LER were obtained. Measurement parameters for accurate LER measurement can be calculated according to the guideline. Measured line-width distribution was used for predicting degradation and variation in MOS transistor performance using the 2D device simulation. Effect of long-period component of LER was clarified as well as short-period component.

Characterization of line-edge roughness in resist patterns and estimations of its effect on device performance

The influence of line-edge roughness (LER) on transistor performance was investigated experimentally and the preciously proposed guideline for CD and LER measurements was examined. First, regarding the transistor-performance measurements, a shift of roll-off curves caused by LER within a gate pattern was observed. Moreover, the effect of transistor-width fluctuation originating from long-period LER was found to cause a variation in transistor performance. Second, regarding LER and CD metrology, the previously reported guideline was validated by using KrF and ArF resist-pattern samples. It was found that both CD and LER should be evaluated with the 2-μm-long inspection area. Based on this guideline, a comprehensive approach for evaluating LER and CD for transistor fabrication process is presented. The authors consider that this procedure can provide useful information for the 65-nm-node technology and beyond.

Metrology of LER: influence of line-edge roughness (LER) on transistor performance

We propose a new method for the evaluation of line-edge or linewidth roughness (LER/LWR). Conventional, directly measured LER/LWR values always contain a random noise contribution, which is called LER/LWR bias. Our method can separate this bias artifact from the true LER/LWR by using a single image of the sample pattern. The idea is based on the dependency of a measured LER/LWR value on the image-processing parameter for noise reduction. Both, the conventional and the new bias-free LER were calculated on series of images with different frame integration numbers but a fixed field of view. In addition, the validity of this method to the gate-LWR measurement on an ArF resist line pattern was examined. The LER/LWR obtained by our method was independent of the frame number, and agreed with the conventional LER/LWR as measured on an image with a sufficiently large frame-number. That is, our method can evaluate LER/LWR without random-noise contribution, suggesting that the method can be applied to images recorded under low-sample-damage conditions (i.e., low signal-to-noise ratio). It is concluded that the proposed bias-free LER/LWR measurement method will be a powerful tool in lithography metrology especially for achieving practical and accurate LER/LWR measurement with low sample damage.

Bias-free measurement of LER/LWR with low damage by CD-SEM

Resists using polyphenol resin are introduced to reduce line-edge roughness (LER), and the spatial frequency characteristics of LER are evaluated. It is found that the long-period components of LER are suppressed in our low molecular-weight polyphenol resists. Device simulation using the measured LER shows that our polyphenol-based resist can drastically reduce the number of low-threshold-voltage (Vth) transistors compared with a conventional resist due to reduced long-period LER. Because LER impact is more serious as the transistor width shrinks, our results suggest that the use of the polyphenol-type resist will be more effective in improving device performance in future lithography process. In addition, it is shown that spectral analysis is a powerful tool for LER evaluation, especially from the viewpoint of device performance estimation.

Spectral analysis of line-edge roughness in polyphenol EB-resists and its impact on transistor performance

We have investigated the possibility of using amorphous low-molecular-weight polyphenols as chemically amplified positive-tone electron-beam (EB) resists. Low-molecular-weight polyphenol, 4,4'-methylenebis[2-[di(2-methyl-4-hydroxy-5-cyclohexylphenyl)]methyl] phenol (3M6C-MBSA) as a base matrix, was protected by 1-ethoxyethyl (EE) groups to control the dissolution rate in aqueous 0.26 N tetramethylammonium hydroxide developer. The film distribution in the depth direction for resist components determined with time-of-flight secondary ion mass spectometry (TOF-SIMS) and the Fourier amplitude spectra of line-edge roughness (LER) have been investigated to understand the relationship between them for the resists formulated with 3M6C-MBSA and two photo-acid generators (PAG), triphenylsulfonium perfluoro-1-butanesulfonate (TPS-PFBS) and triphenylsulfonium n-octanesulfonate (TPS-nOS). From these results, it was found that the resist film consisting of TPS-nOS showed more homogeneity in the depth direction of the film than did TPS-PFBS, which showed low surface energy and diffused easily to the resist surface through the matrix during a coating and post-applied bake step. The resist with TPS-nOS indicated a lower LER value of 5.1 nm in the wide frequency range, especially in the lower frequency region below 10 µm-1. Therefore, the homogeneity of the film is one of important factors for LER control.

https://iopscience.iop.org/article/10.1143/JJAP.44.5484/pdf

Atsuko Yamaguchi

Papers

Characterization of line-edge roughness in resist patterns and estimations of its effect on device performance

Metrology of LER: influence of line-edge roughness (LER) on transistor performance

Bias-free measurement of LER/LWR with low damage by CD-SEM

Spectral analysis of line-edge roughness in polyphenol EB-resists and its impact on transistor performance

Depth Profile and Line-Edge Roughness of Low-Molecular-Weight Amorphous Electron Beam Resists