Abstract
In lithography, resist patterns are fabricated through chemical reactions induced by radiation. In the highly resolving lithography such as extreme ultraviolet (EUV) lithography, the ...stochastically generated defects (stochastic defects) are a serious concern. In this study, the variation of resist polymer caused by stochastic effects was investigated, assuming line-and-space resist patterns to assess the defect risks. Using a half pitch HP, a thermalization distance
r
0
, a total sensitizer concentration
C
s
, and an initial standard deviation of the number of protected units per polymer molecule
σ
i
as variables, the resist pattern formation was simulated on the basis of the reaction mechanisms of chemically amplified EUV resists. The frequency distribution of polymer molecules with the given number of protected units was calculated at the centers of lines and spaces. By defining a total defect risk (the sum of pinching and bridging risks), its dependences on HP,
r
0
,
C
s
, and
σ
i
were clarified.
Abstract
With the improvement of lithography resolution in the horizontal direction, the thickness of resist films becomes thin to avoid pattern collapse. The thinning of resist films is an important ...issue in the development of the next-generation lithography process. In this study, the interfacial effects on the sensitization of chemically amplified extreme ultraviolet (EUV) resists were investigated using a Monte Carlo method on the basis of their sensitization mechanism. The chemically amplified resist is a standard resist used for the fabrication of semiconductor devices. In chemically amplified resists, thermalized electrons reduce sensitizer molecules upon exposure to EUV radiation. The low-energy secondary electron dynamics at the vacuum-resist and resist-underlayer interfaces strongly affected the distribution of decomposed sensitizers. In particular, the resist bulk layer almost disappeared at 20 nm pitch in the specific cases. The control of interfaces becomes important in the development of the next-generation lithography process.
Abstract
In the nanofabrication, the interfacial effects are a serious issue. The effects of resist interfaces on the dynamics of low-energy (near thermal energy) electrons are among them for extreme ...ultraviolet lithography. In this study, the interfacial effects on the protected unit distribution (latent image) of chemically amplified resists were investigated using a simulation on the basis of their sensitization and reaction mechanisms. The formation of the latent images of line-and-space patterns with 12–32 nm pitch was calculated, assuming the chemically amplified resists consisting of an acid generator, a photodecomposable quencher, and partially protected acidic polymer. The aspect ratio was 2. The boundary conditions at the resist interfaces had a significant impact on the latent images near the resist interfaces even for the line-and-space patterns with 32 nm pitch. With a decrease of the pitch, the effects of boundary conditions became affecting the latent image even at the center (half-depth).
Abstract
The manufacturing of semiconductor devices using extreme ultraviolet (EUV) lithography started in 2019. A high numerical aperture tool under development is capable of resolving 8 nm ...line-and-space optical images and will extend the application of EUV lithography. However, resist materials have not been yet applicable to the production with 8 nm resolution. In this study, the relationships among the half-pitch of line-and-space patterns (resolution), chemical gradient an indicator of line edge roughness (LER), and sensitivity were investigated in the sub-10 nm half-pitch region for chemically amplified EUV resists. The chemical gradient was simulated on the basis of their sensitization and reaction mechanisms. The relationship was formulated as a function of total sensitizer concentration (the sum of photoacid generator and photodecomposable quencher concentrations) and the thermalization distance of secondary electrons. The effect of thermalized electrons was well incorporated into the trade-off relationships between resolution, LER, and sensitivity. (147/150)
The trade-off relationships between resolution, line edge roughness (LER), and sensitivity are a serious problem in the extreme ultraviolet (EUV) lithography. The increase of pattern formation ...efficiency is essentially required to simultaneously improve these three properties. The pattern formation efficiency is determined by the factors such as the absorption coefficient, W-value, the reduction potential of acid generator, the effective reaction radius for deprotection, and the efficiency of solubility switching. Among them, the increase of effective reaction radius requires particular attention, because the stochasticity of protected units also increases with the effective reaction radius. In this study, the relationship between defect risks and effective reaction radius for deprotection of chemically amplified resists was investigated using a Monte Carlo simulation under the condition of maximum chemical gradient. LER had a minimum value approximately at the effective reaction radius of 0.3 nm. The pinching and bridging risks decreased with the increase of effective reaction radius to 0.5 nm. However, its effect on the pinching and bridging risks differently depended on the initial standard deviation and the total sensitizer concentration.
Bulk-type all-solid-state batteries (ASSBs) consisting of composite electrodes of homogeneously mixed fine particles of both active materials and solid electrolytes (SEs) exhibit a high safety, high ...energy density, and long cycle life. SE nanoparticles are required for the construction of ion-conducting pathways as a response to the particle size reduction of active materials; however, simple and low-cost milling processes for producing nanoparticles cause a collapse in the crystal structure and eventually amorphization, decreasing the conductivity. This study develops a heat treatment process in water vapor for the low-temperature crystallization of ultrafine SE amorphous particles and the size control of crystalline nanoparticles. An ultrafine (approximately 5 nm) amorphous powder of Li1.3Al0.3Ti1.7(PO4)3 (LATP), as a typical oxide-type SE, is produced via wet planetary ball milling in ethanol. The water vapor induces a rearrangement of the crystal framework in LATP and accelerates crystallization at a lower temperature than that in air. Further, since particle growth is also promoted by water vapor, depending on the heating temperature and time, this heat treatment process can be also applied to the size control of crystalline LATP nanoparticles. A combination of the wet planetary ball milling and heat treatment in water vapor will accelerate the practical application of bulk-type ASSBs.
Extreme ultraviolet (EUV) lithography will be soon applied to high-volume production of semiconductor devices. A high numerical aperture tool is planned to extend the use of EUV lithography. The ...trade-off relationships between resolution, line edge roughness (LER), and sensitivity are a significant concern for the extendability of EUV lithography. In this study, the dependences of chemical gradient (an indicator of LER) on the half-pitch of line-and-space patterns, the sensitizer concentration, and the effective reaction radius for deprotection were investigated using a simulation on the basis of the sensitization and reaction mechanisms of chemically amplified EUV resists. The relationships between resolution, LER, and sensitivity were formulated. In sub-10 nm half-pitch resolution region, the effect of thermalized electrons became clear. The increase of sensitizer concentration and/or effective reaction radius is required for the suppression of the effect of thermalized electrons.
The fluctuation of the line edge of resist patterns, called line edge roughness (LER), has been the most serious problem in the development of next-generation lithography. The major root cause of LER ...is the chemical inhomogeneity at the boundary between the insoluble and soluble regions of the resist. In this study, the stochastic effect induced in the processes of formation of resist patterns was investigated using a Monte Carlo method. The relative standard deviation of acid concentration was smaller than that of absorbed photons. The relative standard deviation of protected units was smaller than that of acid concentration. By comparing the simulation results with the reported values of LER, it was found that the stochastic effect is further reduced in the development and rinse processes.
Line edge roughness (LER) is a serious issue for the fine patterning in electron beam (EB) lithography. LER is formed as a consequence of the accumulation of stochastic events induced in resist ...materials. In this study, the dissolution factor a of LER formation was investigated. The line-and-space patterns of a highly resolving chemically amplified EB resist were analyzed using a Monte Carlo simulation. From the dependence of the relationship between the dissolution factor, exposure dose, and pitch on the initial standard deviation of the number of protected units per polymer molecule, the initial distribution of protected units was estimated to be random for the resist analyzed in this study. a/2 was estimated to be roughly 1.0-1.6. The fluctuation of the number of protected units ±aσp/2 was considered to contribute to the LER formation, where σp is the standard deviation of the number of protected units per polymer molecule after postexposure baking. The resist performance is considered to be improved by decreasing the initial standard deviation of the number of protected units and/or the dissolution factor.
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.
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