Extending extreme ultraviolet (EUV) single exposure patterning to its limits requires more than photoresist development. The hardmask film is a key contributor in the patterning stack that offers opportunities to enhance lithographic process window, increase pattern transfer efficiency, and decrease defectivity when utilizing very thin film stacks. This paper introduces the development of amorphous silicon (a-Si) deposited through physical vapor deposited (PVD) as an alternative to a silicon ARC (SiARC) or silicon-oxide-type EUV hardmasks in a typical trilayer patterning scheme. PVD offers benefits such as lower deposition temperature, and higher purity, compared to conventional chemical vapor deposition (CVD) techniques. In this work, sub-36nm pitch line-space features were resolved with a positive-tone organic chemically-amplified resist directly patterned on PVD a-Si, without an adhesion promotion layer and without pattern collapse. Pattern transfer into the underlying hardmask stack was demonstrated, allowing an evaluation of patterning metrics related to resolution, pattern transfer fidelity, and film defectivity for PVD a-Si compared to a conventional tri-layer patterning scheme. Etch selectivity and the scalability of PVD a-Si to reduce the aspect ratio of the patterning stack will also be discussed.
The Cost of Ownership (CoO) for semiconductor processing has been primarily dominated by lithography. In multiple
patterning processes, additional materials and the impact to throughput of multiple patterning passes appear to become
additional major contributors to manufacturing cost as well. We introduce SiOxNy hardmask as a new memorization
layer for multiple patterning that addresses the non-lithographic cost contributor to manufacturing. The optical constants
of the SiOxNy hardmask are matched to those of the photoresist at the imaging wavelength, and that makes it invisible at
the exposure wavelength, enabling lithography directly over the hardmask topography, while at the same time it will be
visible to those wavelengths that are used for alignment and overlay. The SiOxNy hardmask is inserted below the
photoresist which will make the rework and integration schemes much simpler and result in cost savings by replacing
only photoresist layers during multiple patterning processes. Additionally, by eliminating the need for traditional spincast
planarization and the associated tri-layer etch we can improve the critical dimension uniformity (CDU) and reduce
proximity contributions from etch, and their respective etch proximity corrections. In this work, we engineered the
lithographic stack to be compatible with the invisible SiOxNy hardmask. Lithographic process windows, CDU, and
LER/LWR are compared with conventional tri-layer stack and we demonstrate triple patterning memorized into the
SiOxNy hardmask after which patterns are then transferred, at once, into the bottom integrated stack. Finally, major
benefits of using the invisible hardmask on device scaling and patterning challenges are discussed, such as for LE2, LE3,
and trench and cut patterning.
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