Andrew J. Blakeney

Bilayer resist approach for 193-nm lithography

Tremendous efforts to extend optical lithography beyond the quarter micrometer boundary, which is currently achievable with KrF-excimer laser lithography, are ongoing. One-hundred- ninety-three nm lithography, using ArF-excimer lasers, is believed to be the technology of choice to approach the ambitious sub-0.2 micrometer resolution target. Single layer, positive tone resist systems, which can be developed with aqueous base, would be preferred. However, it might well turn out that the targeted requirements can only be fulfilled by resist systems which involve some type of dry etch steps. This paper focuses on a positive tone bilayer resist system, which is based on novel silicon containing methacrylate polymers bearing acid labile side groups. Due to a unique combination of monomeric building blocks, polymers with high silicon concentrations and, at the same time, high thermal flow stability are obtained. Hardbaked novolac is used as the planarizing layer. Resists systems based on the new silicon containing polymers demonstrated 0.175 micrometer resolution capability, a thermal flow stability greater than 120 degrees Celsius, and an etch selectivity ratio greater than 20.

Structural effects of DNQ-PAC backbone on resist lithographic properties

Model backbones without hydroxyl groups and fully esterified diazonaphthoquinone PACs were studied to identify critical structural parameters for dissolution inhibition in conventional diazonaphthoquinone/novolac photoresist systems. Hydrophobicity, presence of a site interactive with novolac, and proximaity of DNQ groups were identified as critical parameters. In general, the inhibiting ability of model compounds or PACs were found to be correlated with their retention time on reverse phase HPLC, a measure of hydrophobicity. Evidence is shown there to support the suggestion that the DNQ group provides a strong hydrogen bonding site to enhance efficiency of inhibition. PACs having DNQ groups in close proximity had lower inhibition than PACs with DNQs far apart.

Lithographic properties of novel acetal-derivatized hydroxy styrene polymers

Lithographic properties of a variety of acetal-derivatized styrene based polymers are reported. The structural modifications in the polymers involve varying the size of the pendent acetal moiety. the lithographic performances of the resists containing structurally modified acetals were found to be superior to the conventional acetals. In the cases where the acidolysis products of the modified acetals are non-volatile alcohols, the post-exposure volatilization, film shrinkage and plasma etch resistance were found to be significantly improved.

Studies of dissolution inhibition mechanism of DNQ-novolak resist (II): effect of extended ortho-ortho bond in novolak

A p-cresol trimer sequence was incorporated into a polymeric chain of novolak by copolymerization with m-cresol of a reactive precursor which was prepared by attaching two units of m-cresol to the terminal ortho positions of p-cresol trimer. The resulting novolak was characterized by 13C NMR and FTIR in an attempt to correlate novolak structure with dissolution inhibition function based on physicochemical analysis of molecular interactions between novolak and DNQ-PAC in solid films.

Optimization of etch conditions for a silicon-containing methacrylate-based bilayer resist for 193-nm lithography

The 193 nm photoresist generation will need several technological approaches in order for it to be successfully integrated into manufacturing. These approaches include bilayer, single layer and top surface imaging resists. Bilayer resists offer the advantages of thin film imaging (resolution, depth of focus) and potential advantages in plasma etch resistance due to the possibility of incorporating aromatic components into the undercoat. We have developed a prototype bilayer resist system based on a silicon containing methacrylate imageable layer and a crosslinked styrenic copolymer undercoat which has shown 0.13 micrometers resolution. In this paper we will discuss the effects of O2-RIE and polysilicon etch on resist and substrate profile, selectivity and iso-dense resist.

Novolacs With Alternating P-Cresol & Polyhydroxyphenyl Monomer Units: Developer Cationic Effects And Thermal Properties

Novolacs which alternate p-cresol monomer units with polyhydroxyphenyl monomer units have been synthesized by acid catalyzed condensation of 2,6-bis(hydroxymethyl)-p-cresol with polyhydroxybenzenes such as resorcinol or 4-chlororesorcinol. These novolacs are highly alkaline soluble and exhibit improved glass transition temperatures relative to conventional novolacs. Unexpected developer cation effects have been observed on the dissolution times of some of these novolacs. The effect of molecular weight on these effects will be discussed for one system. The dissolution discrimination and inhibition of a 4- chlororesorcinol containing novolac was examined relative to a standard m-,p-cresol novolac and polyvinyl phenol. Images produced from a resist using a p-cresol/ 4-chlororesorcinol novolac showed no significant image degradation at 200 degrees C.

Characteristics of an improved chemically amplified deep‐ultraviolet positive resist

Chemically amplified positive resist formulations have been shown to exhibit high photospeed, excellent resolution, and tolerance to process parameters such as softbake, exposure, postexposure bake, developer concentration, and temperature. Many chemically amplified positive resists, however, adhered poorly to some substrates (e.g., Si3N4), required considerable optimization of the etch process to achieve desired etch selectivities and were sensitive to airborne basic contaminants. Many chemically amplified negative resists while not as sensitive to contaminants in the clean room air, show retrograde wall angles especially on antireflection coatings, demonstrate poor latitude in defining contact holes and are difficult to strip after pattern transfer steps. In this article we discuss our efforts toward designing new deep‐ultraviolet (UV) matrix resins and resist formulations as well as efforts toward defining an optimized process. The optimized resist process demonstrates 0.25 μm line and space (L/S) and ...

Second-generation 193-nm bilayer resist

We have recently developed a bilayer resist system based on a methacrylic silicon-containing imageable layer and a UV curable copolymer undercoat which has exhibited 0.13 micrometers resolution for dense features and 0.12 micrometers resolution for isolated features after substrate etch. In this paper, we will discuss recent advancements in the design of the second generation bilayer resist. In particular, we will discuss the development of two new thermally curable undercoats for use in both 193 nm and 248 nm applications. The optical properties of these new materials have been optimized to reduce reflectivity at the desired wavelength.

Thermal stability of silicon-containing methacrylate-based bilayer resist for 193-nm lithography

Thermal decomposition of silyl substituted methacrylate terpolymers containing acid sensitive groups was studied using thermogravimetric analysis. The onset of decomposition was found to be a function of the microenvironment, i.e. the molar% composition of the acid sensitive group monomer. The Flynn and Wall method of estimating Ea was used to estimate the Ea for decomposition of the terpolymer and where possible, for the acid sensitive group.

Structural basis for high thermal stability of a resist

A new class of novolaks capable of self associating has been synthesized. The associating structures are resulted via extended network of hydrogen bonding. Softening temperatures of the associating novolaks are found to be 15 - 25 degree(s)C higher than their non-associating analogs. The photoresist formulated with such associating novolaks have heat deformation temperature in the range of 130 - 140 degree(s)C. Features with sub 0.35 micrometers could be resolved using i-Line exposure. Site specific hydrogen bonding in such associating novolaks is studied by NMR and molecular simulations.