New Polymers with Acid Labile Crosslinked Units and their Performance in Deep-UV Photoresists (original) (raw)
Related papers
1999
The performance of water-and solvent-cast, two-component photoresist films containing poly(2-isopropenyl-2-oxazoline) or poly(2-isopropenyl-2-oxazoline-costyrene) with a photoacid generator has been investigated. These materials afford negative-tone images after deep-UV exposure and development in a suitable medium (water or toluene). Resist solutions prepared from polymers containing at least 80 mol % 2-isopropenyl-2-oxazoline may be cast from and developed in pure water. Features of higher quality can be obtained when the resist is cast from 2-methoxyethanol, probably because side reactions such as partial hydrolysis of the pendant oxazoline rings in aqueous environments are avoided. It was possible to resolve micrometer scale patterns using ca. 200 mJ/cm 2 of irradiation at 254 nm, followed by heating 2 min at 130°C and development in water alone. Image quality and etch resistance were improved using copolymers containing up to 20 mol % of styrene repeat units.
A family of water-soluble, negative-tone, high-resolution, chemically amplified photoresists based on partially or fully deprotected poly(1,2:5,6-di-O-isopropylidene-3-O-methacryloyl-R-D-glucofuranose) is described. Both the molecular weight of the parent ketal-protected polymer and the extent of its deprotection to a water-soluble polymer containing 3-O-methacryloyl-D-glucopyranose repeat units must be carefully controlled to provide good coating and imaging properties. The two ketal protecting groups of the poly(1,2:5,6-di-O-isopropylidene-R-D-glucofuranose) have different reactivity, and their complete removal requires long reaction times under hydrolytic conditions. The detailed deprotection chemistry of the polymer is readily understood through model studies with the fully and partially protected analogues of the polymer pendant groups: 1,2:5,6-di-O-isopropylidene-R-D-glucofuranose and 1,2-isopropylidene-R-D-glucopyranose. When combined with a water-soluble photochemical precursor of acid such as (4methoxyphenyl)dimethylsulfonium trifluoromethanesulfonate, films of the deprotected or partially deprotected poly(1,2:5,6-di-O-isopropylidene-3-O-methacryloyl-R-D-glucofuranose) undergo acid-catalyzed cross-linking. The enhanced performance of the partially deprotected polymers over that of poly(3-Omethacryloyl-D-glucopyranose) suggests that the presence of remaining hydrophobic groups that afford water dispersibility rather than full solubility may be key to their performance. Imaged negative-tone features as small as 0.2 µm are obtained with these materials that have sensitivities of ca. 30 mJ/cm 2 with wholly aqueous casting and processing.
Journal of Polymer Science Part A-polymer Chemistry, 1999
The performance of water-and solvent-cast, two-component photoresist films containing poly(2-isopropenyl-2-oxazoline) or poly(2-isopropenyl-2-oxazoline-costyrene) with a photoacid generator has been investigated. These materials afford negative-tone images after deep-UV exposure and development in a suitable medium (water or toluene). Resist solutions prepared from polymers containing at least 80 mol % 2-isopropenyl-2-oxazoline may be cast from and developed in pure water. Features of higher quality can be obtained when the resist is cast from 2-methoxyethanol, probably because side reactions such as partial hydrolysis of the pendant oxazoline rings in aqueous environments are avoided. It was possible to resolve micrometer scale patterns using ca. 200 mJ/cm 2 of irradiation at 254 nm, followed by heating 2 min at 130°C and development in water alone. Image quality and etch resistance were improved using copolymers containing up to 20 mol % of styrene repeat units.
Some resists based on chemically-amplified crosslinking of phenolic polymers
Journal of Photopolymer Science and Technology, 1990
Imageable thin films that contain phenolic polymers, acid activated crosslinking agents, and Bronsted acid generators have been developed into a variety of high resolution, high sensitivity resists suitable for use in semiconductor fabrication. Formulations have been optimized for use as DUV photoresists, electron beam resists and X-ray resists. Resists for g-and i-line exposure require the addition of a photosensitizer. Negative imaging versions of these resists contain radiation activated acid generators. Positive imaging versions contain radiation activated base generators and thermally activated acid generators. In either case the imaged resist is crosslinked and stable to temperatures in excess of 200.
Alkylated poly(4-hydroxystyrene) derivatives for deep ultraviolet lithography
Journal of Photopolymer Science and Technology
Alkylated Poly(4-hydroxystyrene) copolymers have been prepared and evaluated for use in deep-uv lithography. These materials have been modified to lower the dissolution rates of poly(4-hydroxystyrene) while maintaining the other desirable properties such as optical absorbance, glass transition temperature, and etch resistance. Lower dissolution rates make these polymers more attractive for application in dissolution inhibition resist schemes. The application of these materials to resists employing diazo compound inhibitors and three component resists using acid photogenerators and acid-sensitive dissolution inhibitors is described.
Journal of Photopolymer Science and Technology
Low stochastics, high sensitivity photoresists remain a goal for EUV lithography. Here we present studies of two polymer systems that attempt to make improvements to these resist characteristics using two different chemical approaches. In one system we work on scissionable poly(phthalaldehyde) modified to enable incorporation of photoactive units on each repeat unit of the polymer chain. In a second system we explore peptoid polymers that possess identical molecular size and composition with much higher molecular uniformity than possible by conventional synthetic techniques. We report the results of exposure of these materials to EUV exposures and the chemical changes that occur.
Positive deep UV resist based on poly(.ALPHA.-acetoxystyrene)
Journal of Photopolymer Science and Technology, 1990
a-Acetoxystyrene (ACOST) undergoes radical polymerization in contrast to a-methylstyrene. However, the polymerization is a slow equilibrium process with a ceiling temperature (Ta) of 47°C at 1 mol/L. Poly(a-acetoxystyrene) (PACOST) possesses a tertiary benzylic carbon adjacent to an ester oxygen in its backbone and is converted upon heating to ca. 220°C to poly(phenylacetylene) and acetic acid. The temperature of deesterification involving the polymer main chain can be lowered by generating a strong acid in the film. However, the acid-catalyzed deesterification of PACOST is accompanied by simultaneous depolymerization. Due to the solubility alteration through the structural modificatY~n and the molecular weight reduction by depolymerization, PACOST containing triphenylsulfonium hexafluoroantimonate functions as a sensitive positive resist incorporating "chemical amplification." PACOST is very transparent in the deep UV region and the resist containing 4.8 wt% of Ph3SSbF6 has an optical density (OD) of 0.3/gum at 248 nm. The resist has a sensitivity of ca. S mJ/cm2 and a contrast (y) of 4.3 when postbaked at 130°C for 5 min and developed with xylenes. Owing to its high glass transition temperature (Tg>200°C), the positive images do not show any thermal flow at 180°C and owing to the aromatic nature of the matrix polymer, the resist is as stable as novolac-based resist systems in CF4 plasma. Unfortunately, however, the resist film tends to suffer from solvent-induced cracking during development due to the stiff polymer chain.
Journal of Applied Polymer Science, 2008
Three-component acrylic copolymers used as a binder for negative-type photoresists were synthesized and characterized. First, free radical polymerization was employed to synthesize two-component binders, i.e., acrylic ester copolymers with different ratios of benzyl methacrylate (BZMA) and methacrylic acid (MAA). Thermal behavior, viscosity and molecular weight of the prepared two-component binders were studied. Then, a series of three-component binders were prepared through incorporation of another monomer, 2-hydroxyethyl methacrylate (2-HEMA). FTIR was used to examine the evolution of chemical bonds at various stages of the synthetic process. Thermal analyses, TGA and DSC, were used to evaluate the level of enhancement on thermal stabilities of the prepared three-component binders. Finally, an optimal region in the ternary composition diagram of BZMA, MAA, and 2-HEMA can be identified by comparing the results of acid value, viscosity, and molecular weight of the binder. A negative-type photoresist was prepared using an optimized composition, for which resolution of the circuit could reach the level of 6 lm.
Delay-time stable chemically amplified deep-UV resist
Advances in Resist Technology and Processing X, 1993
This paper describes a newly developed acetal-based positve tone Deep UV photoresist called DX 46. The material consists of a 4-hydroxystyrene/4-hydroxy-3 -methylstyrene copolymer, a polymeric dissolution inhibitor and a bleachable diazo-photoactive compound. Each of the three compounds is specially designed to fit to each other for high performance sub-halfmicron resolution. The main idea is the use of a poly-N,O-acetal for dissolution inhibition which undergoes efficient acid catalyzed bond cleavage that produces strong dissolution promoting fragments in the exposed area. We determined the activation energy for hydrolysis reaction of our polyacetal to be 10 Kcal/mol. The radiation induced acid catalized hydrolysis reaction starts right after exposure and is accomplished by a mild post exposure bake at low temperature. This resist system is not sensitive to airborne contamination and no charcoal filtered air or diffusion barrier top coats are necessary for T-top free performance. We apply a photosensitive base to the resist in order to stabilize the latent acid image. The base is converted with high quantum yield to neutral molecules in the exposed area while the unexposed region remains strongly basic and neutralizes acid that diffuses into the unexposed side walls. The intrinsic chemistry of low activation energy hydrolysis together with latent image stabilization via photobase results in a high resolution chemically amplified Deep UV resist that shows resolution down to 0.26 tm (NA=0.45) and consideralbly improved process stability. DX 46 works with a high absorbing photobleachable photoacidgenerator that favourably influences the swing curve amplitude. Together with AZ®Aquatar linewidth control upon topography is possible in Deep UV lithography. Due to our chemical concept of a thermally stable polymeric dissolution inhibitor linewidth is also controlled during pattern transfer as this resist does not shrink neither during curing nor during etch processes. Thermally stable up to 150° C, this resist is viable in 64MB process environment.