This paper communicates the use of cobalt-containing polymers in extreme ultra-violet lithography (EUVL). The
polymers were synthesized in a two-step process through the complexation of dicobalt octacarbonyl, Co2(CO)8 to a mainchain
alkyne-functional polyester obtained by polycondensation protocol. As indicated by thermal analysis, the cobaltcontaining
polymers are characterized by a thermal transition around 110 °C assigned to a crosslinking process, a key
factor in considering these materials as candidates for patterning assist layers (PAL) in EUVL. Positive and negative
impacts of the metal component introduced through PAL upon the resolution, line-width roughness (LWR), and
sensitivity (RLS) of the resist were investigated. The potential utility of these materials as wet developable PAL is also
A new type of scissionable polymer based on main-chain acid-labile acetal linkages is reported as a photoresist for
e-beam and EUV lithography. Four kinds of copolymers were synthesized via ring-opening metathesis polymerization
(ROMP) using various ratios of acetal and norbornene-derivative monomers. Differential scanning calorimetry (DSC)
analysis demonstrated that incorporation of bulky structure, i.e., norbornene-derivatives, provided copolymers with high
T<sub>g</sub>. According to thermogravimetric analysis (TGA), these copolymers had slight weight loss in the temperature range
from 100 to 250°C. This weight loss is tentatively assigned to a cleavage process due to the presence of the acetal units.
Both GPC and NMR analyses revealed that the main-chain of these copolymers was steadily chopped at scission
moieties of acetal units by strong acids in solution, and was also chopped by photo-generated acid from PAG in thin-film.
A steric barrier to the scissionable moiety is considered to hinder acidolysis, leading to improvement of main-chain
stability. These copolymers were confirmed to make fine patterns by e-beam exposure, demonstrating them to be
promising materials as photoresists for EUV lithography. Significant improvements are needed to meet the required resolution and photospeed performance for incorporation into viable EUV resists.
We present the results of both theoretical and experimental investigations of materials for application either as a
reversible Contrast Enhancement Layer (rCEL) or a Two-Stage PAG. The purpose of these materials is to enable Litho-
Litho-Etch (LLE) patterning for Pitch Division (PD) at the 16nm logic node (2013 Manufacturing). For the rCEL, we
find from modeling using an E-M solver that such a material must posses a bleaching capability equivalent to a Dill A
parameter of greater than 100. This is at least a factor of ten greater than that achieved so far at 193nm by any usable
organic material we have tested.
In the case of the Two-Stage PAG, analytical and lithographic modeling yields a usable material process window, in
terms of reversibility and two-photon vs. one-photon acid production rates (branching ratio). One class of materials,
based on the cycloadduct of a tethered pair of anthracenes, has shown promise under testing at 193nm in acetonitrile.
Sufficient reversibility without acid production, enabled by near-UV exposure, has been achieved. Acid production as a
function of dose shows a clear quadratic component, consistent with a branching ratio greater than 1. The experimental
data also supports a acid contrast value of approximately 0.05 that could in principle be obtained with this molecule
under a pitch division double-exposure scenario.