Miwa Igarashi

A New Single-Layer Resist for 193-nm Lithography

A positive chemically amplified resist for 193-nm lithography has been developed. The resist consists of a copolymer of tetrahydro-4-methyl-2-oxo- 2H-pyran-4-yl methacrylate and 2-methyl-2-adamantyl methacrylate and a photoacid generator. The acid-catalyzed deprotection of the protective groups leads to a large polarity change in the exposed region of the resist films and it allows for high-contrast patterning with high sensitivity. Using an ArF excimer laser exposure system, a 0.17-µ m lines and spaces pattern has been resolved.

Overcoat materials for acrylate resists to enhance their resolution

We have developed a series of water developable overcoat materials to enhance the resolution of acrylate resists. The overcoat materials are water solutions that consist of a water-soluble polymer, a cross-linker, and non-ionic surfactant with a small amount of IPA (2-propanol). They exhibit affinity for acrylate resists that make them penetrate and react at the surface of the patterned resists. The resolution of the resist can be improved below the resolution limit of the exposure wavelengths by using the optimized materials. Additionally, the line edge roughness of the resist patterns can be reduced with only a small change in the pattern size when a low baking temperature (<95°C) and/or a small change of the composition of the material is applied. These materials are compatible with both acrylate-based 193-nm chemically amplified resists and PMMA (poly(methyl methacrylate)) resists. This indicates that the reaction can proceed even without acids, which are generally generated from photo acid generators (PAGs). The opitimized material affords sub 100-nm patterns for hole and L/S (line and space) with an alicyclic acrylate resist. A 28-nm shrinkage is also obtained with a PMMA resist to formulate the 68-nm trench pattern.

Conductive bilevel resist system based on polysilphenylenesiloxane and polyaniline for nanometer lithography

We propose a new bi-level resist system for nanometer lithography based on a polysilphenylenesiloxene resist over a conductive polianiline bottom layer for nanometer lithography. By introducing suitable polar functional groups, the polysilphenylenesiloxane negative electron-beam resist exhibits high sensitivity and high resolution with tetramethylammoniumhydroxide development. The sulfonated polyaniline in the conductive bottom layer can reduce resist charging and width shifts in the oxygen plasma etching. This conductive bi-level resist system can reduce pattern distortion from alignment errors and the proximity effect. The conductive resist system can also reduce the gate oxide leakage or breakdown caused by resist charging during the plasma etching process in MOS-LSI device fabrication. This system shows high pattern accuracy and process reliability, demonstrating its high potential for application in nanometer generation ULSI production.

Heat- and oxygen-RIE-resistant polysiloxane resist with three-dimensional structure for high-aspect-ratio microfabrication

An organosiloxane resist, 3D structure polysiloxane, had been developed for use as a high resolution bi-layer resist for high-aspect ratio microfabrication. The resist molecule is structured as a rigid 3D siloxane core surrounded by functional groups. The advantages of such a structure are lower degree of swelling, a high oxygen-reactive ion etching resistance, and a high softening temperature. A 100 nm line- and-space pattern is well-defined after electron beam exposure. The resist can be also used for UV lithography. Sub-half micron UV pattern with aspect-ratio or more than 10 can be delineated with the 3D structure siloxane/novolak bi- layer resist system after high density oxygen plasma etching. The novolak bottom layer is etched at about 1000 nm/min, and the etching selectivity ratio is more than 20. The excellent etching resistance of the 3D siloxane is due to its high silicon content and good film quality. The softening temperature of the 3D siloxane is more than 400, although ladder structure siloxanes softening temperature is 150. This suggests the 3D siloxane resist exhibits high heat resistance due to its rigid structure. Bi-layer resist systems with the 3D siloxane show high resolution with high- aspect ratio, demonstrating its great potential for application in microfabrication process of electronic devices.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Environmentally stable chemically amplified resist effects of organic salt additives

Incorporation of organic salt additives consisting of an organic acid and organic base improves the resist stability. The sensitivity of a t-BOC resist without the salt decreased to 1/4 after standing for one hour after deep-UV exposure. Typical T-top patterns were obtained on this resist by a KrF excimer laser stepper (NA equals 0.45), and a half-micron resolution was barely obtained. On the other hand, a t-BOC resist, with an organic salt, consisting of p- toluenesulfonic acid and dicyclohexylamine (PTS/DCHA), showed no change in sensitivity after one hour. The resist with the PTS/DCHA achieved a 0.3-micrometers resolution line-and- space pattern without environmental control or a protective topcoat.