Masataka Endo

Study of the resist deformation in nanoimprint lithography

Numerical simulations and experimental studies are carried out to understand the deformation process of thin polymer film in nanoimprint lithography. Deformation of a thin polymer above its glass transition temperature is studied for various imprinting conditions such as the aspect ratios of a mold pattern, initial thickness of the polymer, and imprinting pressure. Cross-sectional profiles of the deformed polymers are simulated by the finite element method based on a rubber elastic model. The results are compared with experimental data. The areal penetration ratio of the polymer into the recessed groove of the mold and residual thickness underneath the mold are quantitatively evaluated. The simulations and the experimental results agree well with each other.

Quarter micron KrF excimer laser lithography

For quarter-micron KrF excimer laser lithography, a chemically amplified positive resist with high stability and process compatibility has been developed. 0.25- mu m line and space patterns and 0.35- mu m contact hole patterns have been obtained using this resist. The multiple interference effect due to reflection from air and substrate is reduced by using an overcoat film or antireflective coating. The overcoat film is made of a water-soluble polyvinylalcohol derivative. The refractive index of this polymer is 1.3, which is suitable for the resist (index

Characterization of diazonaphthoquinone–novolac resin‐type positive photoresist for g‐line and i‐line exposure using water‐soluble contrast enhancement materials

We describe the characterization of conventional diazonaphthoguinone–novolac resin‐type positive photoresist for g‐line (436‐nm) and i‐line (365‐nm) exposure using water‐soluble contrast enhancement materials. In the experiments, the Rayleigh’s theoretical resolution and contrast enhancement capability of the water‐soluble contrast enhancement materials were set to be equal between the each wavelength exposure. As a result, the pattern profiles of the resist were better, however, the latitude of depth of focus was worse for g‐line exposure than for i‐line exposure. Mask linearity had no difference between them. It was found that the improvement of the pattern profiles for i‐line exposure was achieved by using a higher photobleachable photoresist at i‐line.

Excimer laser lithography using contrast enhancing material

A new process of excimer laser lithography is presented in this paper. A water soluble, contrast enhancing material, we have developed for the KrF (248 nm) excimer laser has made this new process possible. This material, named WSP‐EX (water soluble photopolymer for excimer laser), is characterized by the use of 5‐diazo‐Meldrum’s acid and has good contrast enhancing capability in both photobleaching and photoreactive speed at 248 nm. By utilizing this new material, we can obtain large focus‐depth lattitude. In this paper, the problem of matching the contrast enhancing material with the resist is also discussed.

High-aspect-ratio resist pattern fabrication by alkaline surface treatment

A new and simple high‐aspect‐ratio, single‐layer resist process for the manufacture of very large scale integration (VLSI) devices is described. Before the exposure step in the conventional process, an alkaline surface treatment is added to the positive photoresist. This treatment inhibits the dissolution of the unexposed resist layer during development, which leads to a high‐aspect‐ratio resist pattern. Excellent submicron resist patterns are obtained with a large focus latitude using this simple method.

New portable conformable masking excimer laser lithography using water‐soluble contrast enhanced material

A new portable conformable masking (PCM) using excimer laser lithography has been developed. This method is characterized by the combination of poly(dimethylglutarimide) and the water‐soluble contrast enhanced material developed here and the use of KrF excimer laser exposure. Using this lithography, we obtained good resist pattern profiles and submicron region resolution by a very simple process.

New Pattern Transfer Technology For G-line Lithography

New pattern transfer technology for G-line lithography has been developed. G-line lithography using steppers have become the main tool in the production of submicron design rule VLSI. To adapt G-line lithography for half-micron design rule VLSI production, we have developed new and simple pattern transfer technology. High contrast patterns and resolution were obtained in this technology. This was achieved by using a soak process to treat the resist surface before exposure in the conventional resist process. The surface treatment was done by dipping the wafer in a solution of tetramethyl ammonium hydroxide(TMAH) rather than a chlorobenzene solution. And also, we combined with new pattern transfer technology with CEL (contrast enhanced lithography) to control the aerial image. The resists were imaged by using G-line steppers with NA value of 0.54 and 0.45. The positive photoresists used were S1400(Shipley), TSMR-Vl(Tokyo Ohka) and TSMR-CRB2(Tokyo Ohka dyed resist). A conventional developer for positive photoresist was used for the surface treatment by TMAH alkaline solution. In this process, we have evaluated the baking step either before or after the image exposure in the conventional process in order to compare pattern profiles.

Application of water-soluble contrast enhancing material to g-line lithography

In this paper, we report the application of contrast enhanced lithography to g‐line (436 nm) lithography using our new water‐soluble contrast enhancing material, named WSP (water‐soluble photopolymer). It has been found that the WSP is effectively utilized about resist pattern profile, resolution, and pattern width control for exposure energy, depth of focus, mask linearity. By use of WSP, submicron lithography has been successfully attained without decrease of throughput and complexity.

High-performance 157 nm resist based on fluorine-containing polymer

A new high-performance resist for F/sub 2/ laser (157 nm) VUV (vacuum ultraviolet) lithography has been developed. The resist polymers consist of fluorinated-alicyclic methacrylate (MA), fluorinated-alkyl MA, acid labile unit, etch-resistant unit and adhesive unit. These polymers can be easily synthesized at low cost. A resist based on this polymer has over 40% transmittance per 100 nm thickness and the same etch-resistance as adamanthyl MA type-ArF resists. Fine images with vertical profiles of 200 nm thickness are obtained by contact exposure with the F/sub 2/ laser. Simulations showed that the resolution of this resist with a F/sub 2/ laser stepper (NA 0.85) has 70 nm L/S and 40 nm isolated line pattern capability at 200 nm thickness. Based on the developed 157 nm resist, 157 nm VUV lithography can be accepted as a 70 nm node.

Advanced surface modification process for sub-quarter micron pattern fabrication

Advanced surface modification process with selective chemical vapor deposition method was developed for sub-quarter micron fabrication. With the advanced surface modification process, the high surface modification contrast was achieved and 0.2 micron geometry was successfully fabricated. It has been confirmed that sub-quarter micron ULSIs will be fabricated by optical lithography with the advanced surface modification process.<<ETX>>