One of the most prospective alternative lithography ways prior to EUV implementation is the reverse imaging by means of a negative tone development (NTD) process with solvent-based developer. Contact and trench patterns can be printed in CAR (Chemically amplified resist) using a bright field mask through NTD development, and can give much better image contrast (NILS) than PTD process. Not only for contact or trench masks, but also pattering of IIP (Ion Implantation) layers whose mask opening ratio is less than 20% may get the benefit of NTD process, not only in the point of aerial imaging, but also in achievement of vertical resist profile, especially for post gate layers which have complex sub_topologies and nitride substrate. In this paper, we present applications for the NTD technique to IIP (Ion Implantation) layer lithography patterning, via KrF exposure, comparing the performance to that of the PTD process. Especially, to extend 248nm IIP litho to sub-20nm logic device, optimization of negative tone imaging (NTI) with KrF exposure is the main focus in this paper. With the special resin system designed for KrF NTD process, even sub 100nm half-pitch trench pattern can be defined with enough process margin and vertical resist profiles can be also obtained on the nitride substrate with KrF exposure.
Silicon-containing antireflection coating (SiARC) and spin-on carbon (SOC) under-layers have been
widely implemented for advanced semiconductor manufacturing since the 45 nm node. The combination
of SiARC and SOC promises a superior solution for reflection control and a high etch selectivity. With
the industry marching towards 22 nm and beyond, the tri-layer materials and processes are being finely
tuned to meet the requirements. We report comprehensive evaluation results of the SiARC (with high
silicon content) and carbon under-layer from manufacturing perspective. It focuses on the performances
that are required to extend the tri-layer applications from the original 45 nm nodes to 22 nm and beyond,
such as thickness selection, etch selectivity, resist compatibility, rework capability, and under-layer
pattern wiggling issues.
Underlayers (UL), such as organic planarizing layers (OPLs) or spin-on carbon (SOC) layers, play a very important role
in various integration schemes of chip manufacturing. One function of OPLs is to fill in pre-existing patterns on the
substrate, such as previously patterned vias, to enable lithographic patterning of the next level. More importantly, OPL
resistance to reactive ion etch (RIE) processes used to etch silicon-containing materials is essential for the successful
pattern transfer from the resist into the substrate. Typically, the pattern is first transferred into the OPL through a two-step
RIE sequence, followed by the transfer into the substrate by a fluorine-containing RIE step that leaves the OPL
pattern mainly intact. However, when the line/space patterns are scaled down to line widths below 35 nm, it was found
that this last RIE step induces severe pattern deformation ("wiggling") of the OPL material, which ultimately prevents
the successful pattern transfer into the substrate.
In this work, we developed an efficient process to evaluate OPL materials with respect to their pattern transfer
performance. This allowed us to systematically study material, substrate and etch process parameters and draw
conclusions about how changes in these parameters may improve the overall pattern transfer margin.
The topography effect of Opaque MoSi on Glass (OMOG) mask on 32nm contact hole patterning is analyzed by
examining the difference of image intensity profile between thin mask approximation and rigorous electro-magnetic
field (EMF) simulation. The study shows that OMOG topography results in more than a 20% decrease of image intensity.
The impact of OMOG mask topography on lithography modeling of a 32nm contact hole process is explored by fitting
lithography simulation with experimental results for both thin mask model and EMF model. This study shows that thin
mask modeling is a good approximation of EMF modeling for a contact pitch larger than 120nm, but yields about 10nm
prediction error for a 110nm contact pitch. Thin mask modeling is shown to be inaccurate in predicting critical
dimension of contact arrays with sub-resolution assistant feature (SRAF). In addition, thin mask modeling is too
pessimistic in predicting SRAF printability. In contrast, EMF model shows good prediction of contact arrays with and
without sub-resolution feature. A modified thin mask modeling technique utilizing an effective SRAF size is proposed
and verified with experimental results.
In this paper we investigate fundamental resist properties to enhance resolution and focus margin for immersion
contact hole patterning. Basic chemistry factors have been used to manipulate the iso-focal region (the region of
smallest critical dimension variation through focus) of the photoresist and study the impact on resolution and focus
margin for small isolated contact holes. Acid diffusion length is one of the key factors investigated, which can be
controlled by polymer, PAG, quencher, bake temperature and bake time. The various criteria investigated for this study
were: focus and exposure latitude for dense L/S, dense C/H and semi-dense C/H. The effect of manipulating the acid diffusion of the photoresist on imaging small contact holes was verified using ultra-high NA immersion imaging at 1.35
NA.
KEYWORDS: Reflectivity, Lithography, Critical dimension metrology, Line width roughness, Immersion lithography, Optical lithography, Photomasks, Scanning electron microscopy, Electroluminescence, Control systems
Reflectivity comparison study of bottom anti reflectivity coating (BARC) was investigated at 30nm node devices with same gate width at different pitch sizes. The goal of this study is to elucidate the practical target of reflectivity for high NA immersion lithography especially focusing on the changes in the CD variation. Using double patterning technology (DPT) and single patterning technology (SPT) patterns in high NA systems, we studied the impact of reflectivity to the lithography performance for various ARC thicknesses.
A strong dependence of n, k values (of BARC and substrate) on reflectivity was confirmed by simulation. Standing wave effects were investigated by vertical profiles inspection and changes in lithographic performances. Finally, we investigated the critical dimension uniformity (CDU), and line width roughness (LWR) variations for various reflectivities using hard mask substrates. Our experimental and simulation results clearly show that a 0.1% reflectivity target is highly recommendable for the sub-30 nm device process using high NA immersion lithography.
Quartz dry etching is critical to realize the resolution enhancement technology (RET) mask, such as chromeless phase lithography (CPL) mask, alternating phase shift mask, and RIM type phase shift mask. Quartz etching is one of challenging processes in photomask manufacturing due to the absence of etch stopper. The requirements of quartz etching are sidewall angle, phase uniformity, depth linearity, and micro/macro loading effect in wide range of feature sizes. In this paper, we will discuss the improvement of quartz dry etching using Cr hardmask without any hardware modifications. We can control the tendency of phase uniformity across mask surface in convex or concave curvature with nearly vertical sidewall angle. Two-step quartz etching recipe, which consists of two kinds of sub-etching recipe, is introduced to meet the phase uniformity and quartz profile at the same time. We have optimized quartz dry etching with vertical sidewall angle, low depth uniformity, and low micro/macro loading effect.
Recently, the design rule shrinkage of DRAM devices has been accelerated. According to International Technology Roadmap for Semiconductor (ITRS) 2001, 90 nm node will start in 2004. For this achievement, lithography has been standing especially in the forefront and leading the ultra fine patterning technologies in the manufacturing of semiconductor devices. We are now in the moment of transition from the stronghold of KrF to the prospective of ArF. In this paper, we applied ArF process to the real DRAM devices of 90nm node. We proved good pattern fidelity and device performance. The ArF process, however, has still some weak points - resist shrinkage and LER (Line Edge Roughness). Resist shrinkage is very crucial problem for measuring CD. To overcome it, we applied ASC (Anti-Shrinkage Coating) process to ArF resist and improved the CD measurement. LER also becomes an issue, as the design rule is shrink. It is found that they are very dependent on resist type. However, it could be cured effectively by VUV treatment. Finally we will mention the current status of low k1 factor and the future lithographic strategy of which technologies will be most feasible based on current situation.
We have designed and synthesized a number of unique polymer systems composed of acrylate and styrene even though it had moderate transparency. Our first model of 157nm photoresist was based on a (alpha) trifluoromethylacrylate and styrene bearing a pendent hexafluoroisopropanol with pentafluoroisopropyl t-butyl carbonate (PFITBC) as the transparent enhancer and acid labile compound. PFITBC was obtained from perfluorinated enolate with di-t-butyl carbonate with high yield. All of the absorbance of our system ranged over 3.0~3.4micrometers -1 for base resin, which corresponded to a resist thickness of 110~125 nm at the optical density of 0.4. We have formulated several resists based on these polymers and these formulations have shown high resolution and contrast at 248 nm. We were able to obtain 240nm 1:1 image when exposed at 248 nm by a Nikon stepper with 0.45NA. To overcome the weak etch resistance with thin thickness film, we investigated the vapor phase silylation treatment (SILYAL) in which the treated pattern was more persistent against the O2 plasma and turned to smoother surface. DMSMDA with Bi(DMA)MS of 30-40 wt% showed not only good control resist flow but also the improvement of line-edge roughness. Our results suggested that a facile approach to fluorine incorporated resin with SILYAL process can accelerate the 157nm lithography.
In this work we have studied new types of olefin-containing alicyclic lactones such as (alpha) -angelicalactone(AGL), (gamma) -methylene- (gamma) -butyrolactone((gamma) -MBL), (alpha) -methylene- (gamma) -butyrolactone((alpha) -MBL) and their derivatives. Particular attention was given to (alpha) -BML derivatives, which are readily synthesized. The relative monomer reactivities of the various lactones were found to be quite different. However in the case of (alpha) -MBL and its derivatives they have good radical reactivities with methacrylates and maleic anhydride. Methacrylate derivatives with acid-labile protecting groups were introduced for dissolution contrast. To further promote adhesion the relative ratios of maleic anhydride and norbornylene derivatives was optimized. These novel resists resolve 120nm L/S with conventional illumination (NA=0.6, (sigma) =0.7) and 0.6micrometers DOF with annular illumination (NA=0.6, (sigma) $=0.6/0.8). And also 100nm L/S resolution was achieved using strong off-axis illumination. Oxide etch resistance was found to be equivalent to acetal based KrF resists. Post exposure delay (PED) stability of more than 1 hour was achieved.
A series of new cycloaliphatic olefin monomers protected by alicyclic hydrocarbon groups were synthesized. New polymers of cycloaliphatic olefins and cycloolefin-maleic anhydride (COMA) systems were also designed and prepared using the new monomers for 193 nm resist applications. These polymers were synthesized by free radical polymerization technique, utilizing azobisisobutyronitrile (AIBN) or di-t-butyl peroxide initiators. The cycloolefin polymers synthesized by free radical polymerization method were not good for ArF lithography because of their poor transparency at 193 nm, although they showed a good dry etch resistance. However, the new COMA polymers had good transparency at 193 nm and had an etch rate in CF4 mixture plasma of approximate 1.0 times that of DUV resists. Using ArF exposure tools (NA equals 0.6, (sigma) equals 0.7), 130 nm line/space patterns were resolved. Using Off-Axis illumination, 100 nm line/space patterns were resolved.
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