Satoshi Takei

Silicon-Containing Spin-on Underlayer Material for Step and Flash Nanoimprint Lithography

Nanoimprint lithography is a newly developed patterning method that employs a hard template for the patterning of structures at micro- and nanometer scales. This technique has many advantages such as cost reduction, high resolution, low line edge roughness (LER), and easy operation. However, resist peeling, defects, low degree of planarization, and low throughput issues present challenges that must be resolved in order to mass produce advanced nanometer-scale devices. In this study, the new approach of using a silicon-containing spin-on hard mask underlayer material with high adhesion by reacting methacrylate groups of the underlayer to the acrylate groups of resist material during ultraviolet irradiation was demonstrated to obtain the excellent patterning dimensional accuracy and increase the process latitudes. The performance of this process is evaluated by using step and flash imprint lithography. The obtained high adhesion between the underlayer and resist material was found to lead a silicon-containing underlayer material to excellent patterning dimensional accuracy and 80 nm straight profiles. We expect that the silicon-containing a spin-on hard mask material under organic resist will be one of the most promising materials in the next generation of nanoimprint lithography.

Ultraviolet Nano Imprint Lithography Using Fluorinated Silicon-Based Resist Materials

Fluorinated silicon-based resist materials have recently been applied as ultraviolet crosslinkable materials for nano imprint lithography. I report and demonstrate the step and flash nano imprint lithography process using the newly fluorinated silicon-based resist materials for next generation technologies. This paper presents progress in the formulation of advanced resist materials design, the development of suitable ultraviolet imprint conditions and etch processes to achieve thin residual resist layers, low volumetric shrinkage of the resist film, and low imprint pressures for defect reduction. High quality imprint images were produced with multiple pattern-structured templates on wafers using these developed fluorinated silicon-based resist materials.

Step and Flash Nano Imprint Lithography of 80 nm Dense Line Pattern Using Trehalose Derivative Resist Material

High resolution trehalose derivative resist which had specific desired properties was successfully developed for step and flash nano imprint lithography as one of advanced alternative lithography techniques. Step and flash nano imprint lithography is expected to be a high resolution, thin residual resist thickness, an ambient temperature and cost reduction technique in manufacturing. Excellent 80 nm dense line patterning was demonstrated in nano imprint lithography with ultraviolet crosslinking process. Lower film thickness shrinkage of the newly developed liquid trehalose derivative resist than that of acrylate type resist was one of key to achieve high resolution nano imprint patterns.

CORRELATION BETWEEN SIMULATION AND EXPERIMENT USING UV CURABLE GAP FILL MATERIALS FOR GLOBAL PLANARIZATION

This study focuses on the correlation between simulation and experiment using UV curable gap fill materials for global planarization in advanced lithographic and nanoimprinting techniques. A novel gap fill material has been optimized and developed for global planarization properties. Gap fill materials planarize irregular substrates such as patterned steps, vias, and trenches to increase depth of focus and patterning resolution. After planarizing the substrate surface, the gap fill materials provide dry etching selectivity to the under-layer to avoid damaging the dielectric materials. In the characterization of UV curable gap fill materials, two key factors were identified. The factors were the specific dependence of planarization on the spin speed and film thickness. By optimizing these factors, an appreciable reduction in via topography was realized. An array of 1.1 μm deep, 300 nm diameter holes was planarized to 10 nm thickness bias with a 380 nm thick planarizing film. In addition of global planarization, a final design consideration was to reduce the amount of outgassing during the process. UV curable gap fill material was optimized for sublimate reduction resulting in a defect-free coating. The sublimate produced from the developed gap fill material during baking was significantly decreased when compared with that produced from a thermal curable material. And, the third evaluation of UV curable gap fill materials was reported, to avoid resist poisoning issues in an advanced via-first dual damascene process. The resist poisoning properties in UV curable gap fill material were observed better performance than that of thermal curable material. The resulting UV curable gap fill materials based on this study will be extremely useful for lithographic and nanoimprinting techniques.

Plant-based resist materials for ultraviolet curing nanoimprint lithography

Plant-based resist materials with liquid trehalose derivatives are investigated to achieve low volumetric shrinkage in ultraviolet curing nanoimprint lithography. This procedure is proven to be suitable for resist material design in the process conditions of ultraviolet curing nanoimprint lithography. The developed plant-based resist material using liquid trehalose derivatives with epoxy groups produces high-quality imprint images of 65-nm line and space. The distinctive bulky glucose structure in trehalose derivatives is considered to be effective for minimizing volumetric shrinkage of resist film during ultraviolet polymerization.

New advanced BARC and gap fill materials based on sublimate reduction for 193nm lithography

Innovative technologies are required by integrated circuit manufacturers to create smaller feature sizes on chips. According to the semiconductor roadmap, feature sizes are slated to be as small as 45nm in 2007, and sizes will be continued to decrease in the following years. Suitable absorbance, Lower etch resistance, straight photoresist profiles, wider D.O.F., thinner film thickness, more effective barrier properties to reduce resist poisoning, and sublimate reduction for defect free coating are the major concerns to be taken into consideration for new BARC and gap fill materials. In this paper, the study of sublimate reduction in the new BARC and gap fill materials was investigated. The effect of sublimate reduction from BARC in bake process is related to decrease defect number. We will introduce new BARC and gap fill material consisted of the polymers with self crosslink-reaction system. In addition of sublimate reduction data, resist profiles and 130 nm via fill performance in via- first dual damascene process presented here would show clearly these materials are ready to be investigated into mass production of 90 nm node IC devices and beyond.

Step and Flash Imprint of Fluorinated Silicon-Containing Resist Materials for Three-Dimensional Nanofabrication

Advanced fabrication of multiple-level three-dimensional nanostructures by step and flash nanoimprint lithography was studied. This study has been shown to be applicable to future nanofabrication endeavors in the industrial production of electronic devices and optical materials. Step and flash nanoimprint technologies using the newly fluorinated silicon-containing resist materials to prevent resist pattern collapse, contamination problem of the quartz template, and defect problems were demonstrated. High-quality nanoimprint patterning of 65 nm dense lines and other multiple-level three-dimensional nanostructures was achieved using the proposed material design and under ultraviolet nanoimprint conditions. The developed fluorinated silicon-containing resist material as a hard mask layer with a nonsilicon spin-on carbon material was found to be useful in producing high-aspect-ratio patterned structures by step and flash nanoimprint lithography.

New chemical approach for resist poisoning problem in via first dual-damascene process

The resist poisoning, development defect of photo-resist pattern, has become more serious problem in via-first dual damascene process for 65-nm technology node and beyond. Suppression of the resist poisoning using by novel gap fill (GF) materials is investigated and the influence of GF materials properties on the poisoning is also clarified. It is concluded that the poisoning suppression is associated with chemical reaction between functional groups in the GF film and basic contamination causing the poisoning. On the other hand, the film properties such as film density and hardness do not influence on the poisoning. A mechanism for the poisoning generation is proposed that the GF material can capture the poisoning-contamination in polymer matrix during cross-linking reaction. The capture-reaction can prevent the contamination from diffusion into the photo-resist. Finally, a new GF material, sample-D, suppresses the poisoning to the same level as a process with annealing treatment.

Design and development of next-generation bottom anti-reflective coatings for 45nm process with hyper NA lithography

Integrated circuit manufacturers are consistently seeking to minimize device feature dimensions in order to reduce chip size and increase integration level. Feature sizes on chips are achieved sub 65nm with the advanced 193nm microlithography process. R&D activities of 45nm process have been started so far, and 193nm lithography is used for this technology. The key parameters for this lithography process are NA of exposure tool, resolution capability of resist, and reflectivity control with bottom anti-reflective coating (BARC). In the point of etching process, single-layer resist process cant be applied because resist thickness is too thin for getting suitable aspect ratio. Therefore, it is necessary to design novel BARC system and develop hard mask materials having high etching selectivity. This system and these materials can be used for 45nm generation lithography. Nissan Chemical Industries, Ltd. and Brewer Science, Inc. have been designed and developed the advanced BARCs for the above propose. In order to satisfy our target, we have developed novel BARC and hard mask materials. We investigated the multi-layer resist process stacked 4 layers (resist / thin BARC / silicon-contained BARC (Si-ARC) / spin on carbon hard mask (SOC)) (4 layers process). 4 layers process showed the excellent lithographic performance and pattern transfer performance. In this paper, we will discuss the detail of our approach and materials for 4 layers process.

ARC and gap fill material with high etch rate for advanced dual damascene process

In the case of LSI pattern rules with linewidth of 0.1μm or less, the conventional LSI process is no longer adequate and new process and materials are needed to further enhance the performance of LSI. The materials used to reduce delay include a wiring material, Cu, and a low-k film for interlayer insulation. The technology specially developed for using Cu instead of Al as a wiring material is Dual Damascene process (DD process). In DD process, bottom anti-reflective coating (BARC) and gap fill materials are applied on a substrate of huge topography. Therefore, the gap fill material has to provide a coating of reduced thickness bias between the areas of isolated-via and dense-via, have a higher etch rate than ArF resists, be void free, and have no intermixing with resists and BARC. In order to achieve lower dielectric constant, porous low-k materials will be used at BEOL for the next generation. Etch rates of porous low-k materials are higher than that of conventional low-k materials, which in turn requires a gap fill material of even higher etch rate. This paper describes the new BARC and gap fill material with high etch rate for 45 - 65 node DD processes. The polymer of new materials applies high oxygen content for high etch rate. The performance and via-filling properties in BARC (NCA4401C) and gap fill material (NCA2131) are discussed.