Tilted ion implantation (TII) used in conjunction with pre-existing masking features on the surface of a wafer is a promising cost-effective method for self-aligned double-patterning. Recent work experimentally demonstrated pitch-halving by masked TII into a thermally grown SiO2 hard-mask layer: the wet etch rate of SiO2 increases dramatically if the implant-induced damage exceeds a threshold level, so that implanted regions (vs. non- implanted SiO2 regions) can be selectively removed in dilute hydrofluoric acid solution. In this work, this method is extended to a silicon anti-reflection coating (SiARC) deposited by spin-coating and processed at temperatures compatible with back-end-of-line processing. Negative-tone patterning is achieved by implanting a 10 nm-thick SiARC film with Ar+ species at low energies (less than 5 keV) to reduce the wet etch rate. In general, the higher the implant dose, the greater the etch rate contrast between implanted vs. non-implanted regions of the SiARC layer. In principle, the TII method can be extended to form patterns with dimensions that extend in two orthogonal directions, i.e., two-dimensional (2D) patterns. In this work, the use of TII for 2D patterning is investigated via Monte Carlo simulations to study the effect of implantation dose and varying degrees of overlap between implanted regions extending along orthogonal directions. Stochastic effects on pattern fidelity are systematically investigated. The capability of TII to form sub-lithographic 2D patterns makes it advantageous for extending the era of Moores Law.
Extreme ultraviolet (EUV) lithography high volume manufacturing tools are expected to use laser produced plasma
sources to generate EUV radiation necessary for resist exposure. EUV light from laser sources emit light over a wide
spectral range or popularly known as out-of-band (OOB) radiation along with the desired wavelength. EUV resists are
sensitive to both EUV and OOB radiation because a fair amount of the EUV photoresists are based on materials designed
for 193 nm and 248 nm. Some of the detrimental effects of OOB radiation within the lithography process can be seen in
the form of photoresist film thickness loss, which in turn results in profile degradation. Therefore development of EUV
resists which are insensitive to OOB radiation is very important. We investigated EUV resist patterning performance and
the effect of OOB radiation specifically in the DUV (193 nm and 248 nm) wavelength range. Resist materials with
various DUV absorbance were prepared, and less OOB sensitive materials were found. Moreover, in this study effective
top-coat type material for OOB reduction was developed and its effectiveness was confirmed by EUV exposure results.
In order to resolve 16 nm half pitch and beyond upon EUV exposure, we have developed new materials for not only
resists but also for under layer materials. As for resist, short acid diffusion length photo-acid generator (PAG) was
developed for high resolution. As for under layer, new material with high contact angle (CA) improved line collapse
margin towards printing of minimum feature size. It was found that CA of under layer was one of the important factors
for resolution improvement. Furthermore, effect of development time was investigated to improve resolution. Short
development time gained resolution improvement compared with long one. Finally, combination of these results was
investigated. As a result, JSR EUV resist showed the potential of 15nm half pitch resolution.
Traditional implant layers are becoming increasingly complex in design and continuously pushing
resolution limits lower. In response, developer-soluble bottom anti-reflective coatings (DBARCs) were
introduced to meet these more challenging requirements. These DBARCs excelled over the traditional
combination of single-layer resist and dyed resist/top anti-reflective coating (TARC). DBARCs offered the
resolution and critical dimension (CD) control needed for the increasingly critical implant layers.
Lithographic performance, focusing on CD control over topography and through-pitch behavior,
demonstrated the inherent benefit of the DBARCs over the alternative solutions. Small-space residue
testing showed the benefit of photosensitive (PS) DBARCs for cleanout of sub-100 nm trenches. A study
of improved post-develop residue in various ion-implantation processes validated the use of new DBARC
materials in implant layers.
Extreme ultraviolet (EUV) lithography is one of the most promising candidates for next generation
lithography (NGL) that can print 22nmhp and beyond. In order to implement EUV technology, resist is one of
the critical items that require significant improvement in overall performance. In order to achieve these
improvements, many research groups are developing new materials such as molecular glass (MG) polymer
bound photo-acid generator (PAG) high quantum yield PAG, sensitizer and high absorption resin.
In this study, we focused on innovative PAG materials and correlated PAG acid diffusion length to
lithography performance. As a result, new resist designs with improved resolution, LWR,
sensitivity are reported.
In order to achieve targeted resist performance for EUV in practical applications, we have developed new materials such
as molecular glass (MG), PAG, and acid amplifiers (AA). Protected NORIA, a molecular glass, was examined for
extending resolution limits. The resist with protected NORIA showed 22 nm hp resolutions under EUV exposure. PAG
acid diffusion effect on LWR was also investigated. It was found that acid diffusion control was one of the most
important factors for LWR improvement. To improve sensitivity, application of AA (acid amplifier) was investigated.
The resist with AA gained 25% sensitivity improvement over the original formulation. Elemental technologies for major progress of EUV resist were made.
The synthesis and characterization data for a new sulfonium photoacid generator (PAG),
diphenyltrimethylsilylmethylsulfonium triflate (I), is reported. It is shown that the molecule undergoes rapid silyl group
transfer to water or phenol in the presence of a strong, nucleophilic base such as trioctylamine (TOA). The resulting
PAG, diphenyl-methylsulfonium triflate (II), is subsequently degraded by TOA via methyl group transfer from S to N
leading to the formation of Ph2S and methyltriocylammonium triflate. Both I and II are stable when non-nucleophilic
base quenchers are used. Dose-to-clear and patterning results obtained from EUV exposures at Intel-MET are presented,
illustrating that increased sensitivity can be obtained with PAGs I and II relative to triphenylsulfonium triflate (TPSOTf),
but that LWR is compromised.
While much work has been done in the design of photo resist for EUV lithography, these materials have typically been
optimized for so called "standard developer" i.e., 2.38% tetra methyl ammonium hydroxide. However we felt that it
would be reasonable to consider specifically the developer as opposed to the resist design. Indeed it has been suggested
that the polarity and cation size in developer are important positive tone resist performance. It is our hypothesis that a
base that could wet and penetrate faster into partially deprotected resist could result in a faster photo speed, and thus
make more process margin available for resist design; for example a slower system incorporating higher quencher
loadings. Additionally, we sought to probe the effects of solvent polarity with varying amounts of non-aqueous solvent
additive. By reorganization of the nascent solvent shell with the non aqueous additives, we sought to perturb the
development kinetics and thus change the resist's performance envelope by accelerating photo speed and potentially
increasing contrast. This approach has been applied to non chemically amplified resist to good effect. In the three
positive tones EUV and a 193nm photo resist was evaluated with the prototype developers we found that the
performance was profoundly impacted by these two probes (i.e. solvent polarity and cation hydrophobicity).
Concentration gradients of photoacid generator through the thickness of the photoresist film can profoundly affect the
material's performance. To engineer the acid concentration through resist thickness, we have developed a new type of
resist adhesion promoting layer that incorporates photo acid generator chemistry. These adhesion promoting photo acid
generators, called as a class "APPAG" enhance acid concentration at interface between the resist and the substrate. We
will provide an overview on the preparation and characterization of two siloxane based APPAG materials along with a
performance comparison of commercial DUV, EUV and E-beam photoresists on APPAG.
Nonaflate analog (APPAG 6) with shorter acid diffusion length was found to have a mild impact on 250nm node DUV
lithography. However the triflate analog (APPAG 9), owing to the larger acid diffusion length, was shown to provide a
greater influence. APPAG 9 was found to give nearly a 50% improvement in depth of focus.
For EUV lithography, both APPAG 6 and APPAG 9 will be shown to substantially improve performance envelope for
100nm dense lines and spaces and at reduced post exposure bake (PEB) temperatures. This indicates that this approach
can be used to gain margin at reduced PEB which is desirable to minimize thermally driven diffusion effects. Thus the
materials represent an important new approach to extending photoresist performance margins.