We have developed a transparent, high refractive index inorganic photoresist with significantly higher etch resistance
than even the most robust polymeric resist. As feature sizes continue to decrease, film thickness must be reduced in
order to prevent pattern collapse. Normally thinner films prevent sufficient pattern transfer during the etch process,
creating the need for a hardmask, thus increasing production cost. Compared to PHOST, we have shown over 10 times
better etch resistance. Organic photo-crosslinkable ligands have been attached to a hafnium oxide nanoparticle core to
create an imageable photoresist. This resist has shown superior resolution with both E-beam and 193 nm lithography,
producing sub-50 nm patterns. In addition to improved etch resistance, the inorganic photoresist exhibits a high
refractive index, increasing the depth of focus (DOF). The nanoparticle size of ~ 1-2 nm has the potential to reduce line
edge roughness (LER).
Future demands of the semiconductor industry call for robust patterning strategies for critical dimensions
below twenty nanometers. The self assembly of block copolymers stands out as a promising, potentially lower cost
alternative to other technologies such as e-beam or nanoimprint lithography. One approach is to use block
copolymers that can be lithographically patterned by incorporating a negative-tone photoresist as the majority
(matrix) phase of the block copolymer, paired with photoacid generator and a crosslinker moiety. In this system,
poly(α-methylstyrene-block-hydroxystyrene)(PαMS-b-PHOST), the block copolymer is spin-coated as a thin film,
processed to a desired microdomain orientation with long-range order, and then photopatterned. Therefore, selfassembly
of the block copolymer only occurs in select areas due to the crosslinking of the matrix phase, and the
minority phase polymer can be removed to produce a nanoporous template. Using bulk TEM analysis, we
demonstrate how the critical dimension of this block copolymer is shown to scale with polymer molecular weight
using a simple power law relation. Enthalpic interactions such as hydrogen bonding are used to blend inorganic
additives in order to enhance the etch resistance of the PHOST block. We demonstrate how lithographically
patternable block copolymers might fit in to future processing strategies to produce etch-resistant self-assembled
features at length scales impossible with conventional lithography.
The trend of ever decreasing feature sizes in subsequent lithography generations is paralleled by the need to reduce resist
thickness to prevent pattern collapse. Thinner films limit the ability to transfer the pattern to the substrate during etch
steps, obviating the need for a hardmask layer and thus increasing processing costs. For the 22 nm node, the critical
aspect ratio will be less than 2:1, meaning 40-45 nm thick resists will be commonplace. To address this problem, we
have developed new inorganic nanocomposite photoresists with significantly higher etch resistance than the usual
polymer-based photoresists. Hafnium oxide nanoparticles are used as a core to build the inorganic nanocomposite into an
imageable photoresist. During the sol-gel processing of nanoparticles, a variety of organic ligands can be used to control
the surface chemistry of the final product. The different ligands on the surface of the nanoparticles give them unique
properties, allowing these films to act as positive or negative tone photoresists for 193 nm or electron beam lithography.
The development of such an inorganic resist can provide several advantages to conventional chemically amplified resist
(CAR) systems. Beyond the etch resistance of the material, several other advantages exist, including improved depth of
focus (DOF) and reduced line edge roughness (LER). This work will show etch data on a material that is ~3 times more
etch-resistant than a PHOST standard. The refractive index of the resist at 193 nm is about 2.0, significantly improving
the DOF. Imaging data, including cross-sections, will be shown for 60 nm lines/spaces (l/s) for 193 nm and e-beam
lithography. Further, images and physical characteristics of the materials will be provided in both positive and negative
tones for 193 nm and e-beam lithography.
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.