We developed negative-tone chemically amplified molecular resists based on a fullerene derivative and evaluated the
lithographic performance using 75 keV electron beam (EB) exposure tool to explore the potential of fullerene derivatives
as a negative-type EB resist with high resolution and high etching durability. The etching rate of fullerene derivatives is
lower than that of conventional resist materials such as PHS, ZEP530 and UVIII. Although a dose of 800 μC/cm<sup>2</sup> is
required, 60 nm line resolution and aspect ratio five was obtained in best of four kinds of fullerene derivative films. Also,
the effect of acid generators to a fullerene derivative resists were investigated. Fullerene derivative resists are a
promising candidate for nanolithography because it is essential for next generation lithography to have high aspect ratio related collapse of high resolution pattern and high etching durability in ultra-thin films.
We report the development and applications of ArF negative tone resist for ArF immersion lithography. New developed
topcoat-free ArF negative tone resists has sufficient water repellent capability that is applicable to over 700mm/s scan
speed water immersion exposure tool and suitable leaching suppression capability within reaching specification of
exposure tool. We demonstrated lithographic performance of topcoat-free negative tone resist utilizing 1.07NA
immersion tool and confirmed the lithographic window of 55nm 1L1S and 50nm 1L1S. And 27.4nm of isolated space
pattern at over dose condition of 55nm 1L1S patterning. This result shows the possibility of topcoat free negative tone
resist for dual trench based litho-etch-litho-etch double patterning. Additionally we have demonstrated contact hole
patterning utilizing double exposure and generated 65nm gridded contact hole patterns utilizing 0.92NA ArF scanner
with applicable pattern profiles.
Double patterning is considered the most viable option for 32- and 22-nm complementary metal-oxide semiconductor (CMOS) node development and has seen a surge of interest due to the remaining challenges of next-generation lithography systems. Most double patterning approaches previously described require intermediate processing steps (e.g., hard mask etching, resist freezing, spacer material deposition, etc.). These additional steps can add significantly to the cost of producing the double pattern. Alternative litho-only double patterning processes are investigated to achieve a composite image without the need for intermediate processing steps. A comparative study between positive–negative (TArF-P6239+N3007) and positive–positive tone (TArF-P6239+PP002) imaging is described. In brief, the positive–positive tone approach is found to be a superior solution due to a variety of considerations.
Double patterning based on existing ArF immersion lithography is considered the most viable option for 32nm and below CMOS node. Most of double patterning approaches previously described require intermediate process steps like as hard mask etching, spacer material deposition, and resist freezing. These additional steps can significantly add to the cost of production applied the double patterning. In this paper, pattern freezing free litho-litho-etch double patterning process is investigated to achieve a narrow pitch imaging without the intermediate processing steps. Pattern freezing free litho-litho-etch double patterning utilizing positive-positive resist combination demonstrated composite pattern generation.
We developed a chemically amplified molecular resist based on a fullerene derivative and evaluated the lithographic
performance using 75 keV electron beam (EB) exposure tool to explore the potential of fullerene derivatives as a
positive-type EB resist with high resolution and high sensitivity properties. The etching rate of fullerene derivative is
almost similar to that of ZEP and UVIII. Also, the fullerene derivative resist containing 6 wt% acid generator shows a
sensitivity of 33 &mgr;C/cm2 when it was exposed to 75 keV electron beam and postbaked at 170 °C. Although it required a
dose of 800 &mgr;C/cm2, a fullerene derivative film yielded line resolution of better than 30 nm. Moreover, the effect of the
types of acid generators to the resist performance of fullerene derivatives was investigated. It is very important for a
fullerene derivative resist to select appropriate acid generator and process conditions. Fullerene derivative resists are a
promising candidate for nanolithography.
A dynamic receding contact angle (RCA) is a well-known guideline to estimate the degree of watermark (WM)
defects, which shapes circle and bridges inside of the defect and reduces with enlarging the RCA of topcoat (TC).
However, our recent investigation revealed the occurrence of the circular shape defects in spite of using the TC with a
large RCA, bringing about a change of line and space pattern pitch. In this paper, we clarify the origin of these defects
and propose a new key factor of the dynamic surface properties of immersion-specific defects. It was found that the
pitch-change defect is caused by the lens effect of the air bubbles embedded between advancing water meniscus and the
TC. To well understand generation of the bubble defects, we defined the "effective" hysteresis (EH) as the hysteresis of
dynamic contact angle taken the effects of water-absorption into account. An analysis with the EH indicates that the
bubble defect arises from not only to the large ACA but also small amount of water uptake and the amount of
water-absorption could be substituted by the dissolution rate of TC. It was demonstrated that the EH proposed is a new
key factor for estimating the number of bubble defects. The EH is very useful for analyzing the bubble defects in
immersion lithography. The characteristics of the bubble defect are also discussed with a focus on the structure of the
polymer attached to water.
193nm immersion lithography is the most promising lithographic technology for the semiconductor device manufacturing of 65nm node and below. The advantage of 193nm immersion lithography is the possibility of wider depth of focus (DOF) and higher resolution through the hyper NA lens design greater than 1.0<sup>(1-3)</sup>. In this paper, we investigated the topcoat material film characteristics and evaluated its performance to determine the chemical properties needed for a practical level. The stage scan speed capability evaluation, which is one of the best available method to test the suppression or generation of small water droplet remains on the topcoat film at high-speed stage scan during immersion exposure, was used. And finally we investigated the defectivity of topcoat process utilizing the Nikon EET. The static and dynamic contact angles of water droplet were investigated to characterize the topcoat material. The tilting sliding and receding angle, the contact angle of water droplet at the dynamic state, were important parameters to characterize the topcoat materials and have good correlation to wafer stage scan speed capability and immersion defect count reduction.
193nm immersion lithography is the most promising lithography candidate for 45nm node technology and beyond. However, immersion specific issue, such as the immersion specific defect and the leaching of resists compound into immersion fluid, still exists without any effective countermeasure. To realize a productive 193nm immersion lithography process, we have to develop a cost effective material that might be immersion dedicated resist. In this paper, we investigated the leaching with different polymer protective agents and hydrophobicity. It was found that the leaching amount was strongly related to the activation energy of the protective agent and hydrophobicity of the polymer. Higher activation energy of protective agents and higher hydrophobicity of polymer showed less amount of leaching. In this paper, newly developed developable type topcoat TILC<sup>TM</sup>-031 demonstrated the excellent ability of immersion defect prevention.
It is a well-known strategy for the improvement of resist performance to halogenate resist materials especially in electron beam and X-ray resists. However, the halogenation of polymers requires special caution for chemically amplified resists, because it may interfere with acid generation. In this work, the acid generation in poly[4-hydroxystyrene-co-4-(1,1,1,3,3,3-hexafluoro-2-hydroxypropyl)-styrene] films was investigated. Acid yields decrease as the ratio of hexafluoroalcohol units increases. This study showed that the reactivity of the polymers with low energy electrons (~0eV) correlates to the decrease of acid yields.
In the past several years, ArF immersion lithography has been developed rapidly for practical applications. One of the most important topics is the elucidation of a mechanism and its solution of immersion specific defects. In this paper, we report several analytical results of immersion specific defects. First, we classify several possible origins of specific defects that are proposed based on our experiment on the actual immersion process and previous literature. We focused on a droplet of immersion water that was the origin of circular and deformed circular-type defects. Further, a watermark (WM) was created on some types of film stacks with or without the topcoat (TC) on the resist. We observed that all samples exhibited the trace of the WM. From chemical surface analyses, we obtained different types of components in the residue of the WM, which dried spontaneously. These components depended on the tested film stack. Some types were not always derived from leaching materials in the resist. Some components in the residue appeared to be airborne contaminants that were unregulated in machines used in the photolithography process. Based on the results of these tests, we discussed some methods for avoiding defects according to the droplet WM.
193 nm lithography is one of the most promising technologies for next-generation lithography and is being actively evaluated for making it practicable <sup>(1,2)</sup>. First, we evaluated an immersion lithography tool (engineering evaluation tool (EET)) <sup>(3)</sup> and a dry lithography tool (S307E) with the same numerical aperture (NA = 0.85), manufactured by Nikon Corporation. As a result, an increase in the depth of focus (DOF) of the EET to 200 nm in comparison with the DOF (110 nm) of the dry exposure tool was confirmed in a 90 nm isolated space pattern. Next, the optical proximity effect (OPE) in this pattern was evaluated. Generally, when an immersion lithography tool is compared with a dry one with the same NA or both the tools, only an increase in the DOF is found. However, we confirmed that the OPE (The OPE of the 90 nm isolated space pattern is defined as the difference in the space width between a dense space and an isolated space.) of the dry exposure tool for the 90 nm isolated space pattern reduced from 33.1 nm to 14.1 nm by immersion lithography. As the effect of the reduction of 19 nm, the OPE reduced to 15.2 nm by the effect of the top coatings (TCs) and to 3.8 nm by the optical characteristics. An impact of about 5 nm on the OPE was confirmed by the process parameters-film thickness and the pre-bake temperature of the TC. In the case that the solvent was replaced with a high boiling point solvent, the impact changed from 5 to 20 nm further, the replacement of the solvent had a considerable impact on the OPE. However, this influence differs considerably according to the kind of resists; further, it was shown that the addition of acid materials and a change in the polymer base resulted in a high impact on the OPE for a certain resist. Thus, it was demonstrated that the selection of TC is very important for the OPE in immersion lithography.
The Electron Projection Lithography (EPL) has already presented high resolution capabilities and been developed as one of the candidates of post optical lithography. However, much discussion has not been made for resist chemistry, especially on outgassing during exposure, regardless of utilizing high acceleration voltage and applying vacuum system. Moreover, two types of resist system, positive and negative tones, are required for a complete device manufacturing due to its stencil mask structure. Both resist tones with chemically amplified system were experimentally formulated to examine the partial and total pressure changes after exposure. The mass number of outgassing species was also measured in vacuum. The positive tone resist sample indicated many peaks at high mass numbers, in contrary to that negative tone resist sample showed strong peaks at low mass numbers. In addition, it was found that there was a clear trend between the total exposure doses and the total pressure changes in a certain positive-tone resist formulation. The fact may suggest the necessity of high sensitivity resists for EPL from the different standpoint of high throughput in mass production. The dependency of resist base polymer backbone was also examined under an accelerated exposure condition. The resist comprising of methacrylate base polymer indicated high amount of outgassing than that of poly(hydroxystyrene) (PHS) base polymer, with the same resist formulation. The polymer decomposition other than deprotection was considered since the exposure energy in EPL was much greater than that of optical lithography. We developed a new resist adopting the low outgassing concepts such as high sensitivity, non-methacrylate part, and low protecting ratio. The resist presented 56nm 1:2 contact resolution with resist sensitivity of 5.7μC/cm<sup>2</sup>.