We present a comprehensive study of pitch 20 nm (P20) and pitch 18 nm (P18) metal logic designs, including regular tip-to-tip (T2T) and logic structures using bright-field masks in combination with dry metal-oxide resist. Patterning performance is evaluated across multiple source configurations and resist process conditions. For P20 T2T, we demonstrate a ∼13 nm T2T-CD (critical dimension) with local CD uniformity (LCDU) below 3 nm. For P18, single high-NA EUV exposure enables 18 nm T2T-CD with LCDU<3 nm. Further scaling is achieved using a directional etch at resist, reducing T2T-CD to ∼9 nm while maintaining LCDU ∼3 nm in P18 structure. To assess manufacturability, large-area defectivity is investigated using e-beam inspection after etch into hardmask for P20 metal logic structures. These results demonstrate the feasibility of single-patterning approaches for advanced metal logic and support the adoption of High-NA EUV for damascene integration.
BackgroundRecently, High Numerical Aperture Extreme Ultraviolet Lithography (High-NA EUVL) started delivering its first wafers, showing its potential by printing 18 and 16 nm pitch line/space. However, as feature sizes drop below 10 nm, questions are raised on the ability of the current metrology procedures and tools to properly characterize such small targets. In particular, it is critical to assess the impact of limited spatial resolution and identify possible ways forward.AimA high-resolution, low damage strategy based on high-landing energy (LE) is proposed.ApproachHigh-LE setting (15 keV) and standard low LE (500 eV) best-known methods are compared using both rigorous simulation and experiments. The comparison is performed for metal oxide resist (MOR) as well as for chemical amplified resist, after development inspection (ADI), and after etch inspection (AEI).ResultsOur results indicated that the 15 keV setting provides 3× better resolution and less ADI damage as compared with the 500 eV setting. AEI damages, throughput, and precision are comparable.ConclusionsUsing high LE provides the needed resolution for High-NA EUVL, with similar or better impact on damages compared with low LE.
BackgroundNonchemically amplified resists (n-CARs) have emerged as a promising candidate for the next-generation of resists. Sulfonium-based n-CARs exhibit the capability of forming patterns with high resolution and low LER. However, their practical application is severely hindered by the low sensitivity.AimIt is expected to improve the sensitivity of sulfonium-based n-CARs by enhancing the absorption of extreme ultraviolet (EUV) or electron irradiation, thereby increasing the yield of secondary electrons and promoting the subsequent chemical reactions.ApproachFluorine has a higher EUV absorption cross-section than that of carbon and oxygen elements. Introduction of F-C bonds to resist matrix will boost the EUV photons or electrons absorption and induce the occurrence of new photochemical reactions. We synthesized a multisulfonium-based molecular glass (MG) functionalized with pentafluorobenzylphenylmethylsulfonium (AD-4PF), together with the nonfluorinated MG of AD-4Ph. The lithographic performances of both resists were evaluated by electron beam lithography (EBL) and extreme ultraviolet lithography (EUVL).ResultsThe sensitivity of AD-4PF resist (2487 μC cm−2) was 30% higher than that of AD-4Ph model resist (3559 μC cm−2) in EBL, achieving well-defined 20 nm line/space (L/S) patterns at a dose of 2900 μC cm−2. A similar sensitivity improvement (112 versus 172 mJ cm−2) was observed in EUVL. Photochemical reaction confirmed that the solubility switch of both MG resist films originated from the cleavage of the bond of benzylic S+−CH2PF to form nonpolar methyl thioether.ConclusionsThe fluorinated AD-4PF molecular resist demonstrates high resolution and improved sensitivity, which has been confirmed by EBL and EUVL. The difference in sensitivity between the AD-4PF and AD-4Ph resists is mainly attributed to the significantly enhanced absorption cross-section, the reduced bond energy, and the additional possible dissociative electron attachment (DEA) process by fluorine incorporation.
BackgroundSince the birth of the integrated circuit, electronics industry growth and innovation have relied on semiconductor manufacturers putting ever smaller features (described by their critical dimensions or CDs) into production. Yet today, stochastics, the randomness inherent to chip making near the atomic scale, is threatening the continued ability to manufacture the smallest possible features in volume production.AimTo understand the impact of stochastics on semiconductor manufacturing today, the stochastic resolution gap is defined and used as a framework assessing the value of reducing stochastic variability.ApproachWe provide an introduction to stochastics, their emerging limitations on lithography resolution, technology solutions for improving resolution and yield, and the importance of accurate measurement technology for bridging the stochastic resolution gap.ResultsUsing one stochastics-aware design rule example, a method for determining the optimum via size in a specific 28-nm pitch process is presented to minimize the detrimental role of stochastics.ConclusionsThe stochastic resolution gap is a real limitation, but it is not fixed. Further efforts are needed to continue to close this gap.
BackgroundThe development in photolithography proceeds through multiple steps that require precise monitoring to capture each procedure. Although standard sensitivity analysis defines the static dose-to-clear endpoint, these conventional metrics fail to resolve the time-dependent physical and chemical pathways that dictate final pattern quality.AimWe aim to determine the effect of photoacid generator (PAG) loading and quencher additives on the sensitivity and time-resolved development pathways of a model chemically amplified photoresist exposed under extreme ultraviolet (EUV).ApproachInitial sensitivity analysis on silicon substrates established a dose-to-clear reference window for all resist formulations. Using this defined exposure range, a quartz crystal microbalance with resistance monitoring tracked real-time dissolution kinetics from low doses through full clearance in a diluted developer.ResultsDevelopment behavior was categorized into four distinct modes based on resonant frequency and motional resistance. Increasing PAG concentration or exposure dose systematically shifted the observed development behavior from diffusion-dominated uptake toward rapid bulk dissolution.ConclusionsSamples exhibiting similar final thicknesses can evolve through fundamentally distinct time-resolved development pathways. Here, we report a model photoresist formulation that transitions from swelling (at 5 wt.% PAG) to nonswelling behavior (at 10 and 20 wt.% PAG) during dissolution in a diluted developer. In addition, resists containing a photo-decomposable quencher required a higher exposure dose than their quencher-free counterparts to achieve similar dissolution behavior. Ultimately, these findings demonstrate that real-time kinetic measurements are essential to capture the critical, transient interfacial states that govern EUV resist dissolution.
