Novel Classes of Cyclic Olefin Polymers for 193nm Lithography

Abstract

In previous papers we have reported on the lithographic and etch performance of IBM's internally developed 193nm single layer photoresist system which is based on functionalized poly(norbornenes). These polymers are unique in that they offer potentially superior etch resistance when compared to other polymer systems being investigated for 193nm lithography, and in addition, have the requisite transparency which could lead to superior imaging performance as well. However, this class of polymers is unusual in that the dissolution properties are very different when compared to 248nm or other 193nm polymer platforms as has been previously reported by Ito. This paper will focus on the design, properties and lithographic performance of functionalized norbornene polymers we used for 193nm resist materials development.

Mechanistic understanding of post-etch roughness in 193-nm photoresists

“…While the control 248 nm photoresist, UV6, (A) exhibits smooth surface, 193 nm photoresists (B-D) exhibit significant surface roughness as can be seen from both top-down and cross-sectional SEM images. As reported by Varanasi et al, 3 that cyclo-olefin copolymer exhibits smoother surface than COMA hybrid copolymer or (meth)acrylate copolymer. This is more conspicuous when AFM images are compared as shown in Figure 3.…”

“…1 Compared to commercial 248 nm resists, 193 nm photoresists exhibit significant roughness especially under the etch conditions for dielectrics, such as silicon dioxide and silicon nitride. [2][3][4] For instance, while AFM analysis of DUV resists exhibit the mean roughness (R a ) of ~1 nm after bulk oxide etch, R a 's of 193 nm resists were found to be in the range of 4 to 7 nm depending on the chemical structure of the resist backbone. This seemingly minor increase in PER with 193 photoresists can cause the formation of pinholes and the loss of pattern integrity during the etch process.…”

Evolution of patterning materials towards the Moore’s Law 2.0 Era

“…27) The realization by Fujitsu chemists 28) that acceptable plasma etch resistance and 193 nm transparency can be simultaneously achieved in an acrylic resin through incorporation of alicyclic components (fused carbon rings) inspired the creation of a second generation of 193 nm resists that used cyclo-olefinic groups (norbornenes), which were incorporated as the polymer main chain and carried different functional units that worked as protecting groups, aqueous solubility enhancers, substrate adhesion promoters and PAG compatibilizers. 29) The high etch resistance afforded by the polynorbornene polymers was countered by complex synthetic procedures, limited design flexibility, swelling during dissolution and repeatability issues. Subsequently, a third generation of 193 nm resists became what is known as the state-of-the-art CAR for 193 nm lithography and is used commercially today, utilizing methacrylate moieties bearing pendant alicyclic groups that consist on cycloalkyl-fused rings, 18) which reduces the hydrogen content and increases the carbon content in the film, thus increasing etch resistance while providing the solubility switch (e.g.…”

Relationship between Sensitivities of Chemically Amplified Resist Based on Adamantane Derivatives upon Exposure to ArF Excimer Laser, Electron Beam, and Extreme Ultraviolet Radiation

“…As a method of post KrF lithography, ArF lithography was developed and has been widely used in mass production. For ArF lithography, resist polymers based on alicyclic hydrocarbon compounds such as adamantane, norbornane, and tricyclodecane have been developed [4][5][6][7][8][9] to replace PHS because of the transparency to the wavelength of 193 nm. These polymers have been widely used for sub-60-nm fabrication and may be used for 32 nm fabrication with immersion and/ or double-patterning technologies.…”