Extreme ultraviolet lithography (EUVL) enables integrated circuit (IC) industry to manufacture chips with increased transistor density per volume unit, so the Moore’s law remains true to date. To support the endless requirement of reducing critical dimension (CD), chemically amplified resist (CAR) has been designed to address the resolution, line width roughness, and sensitivity (RLS) in nanoscale level. However, a good Litho performance from an EUV photoresist may not always be transferred into a good etch performance, limiting the stochastic defects after patten transfer is the key to achieve a good after etch inspection (AEI) defectivity. In this paper, we report the EUV photoresist design strategies to acquire good AEI defectivity with the understanding of CAR’s property in a defined pattern transfer scheme with special focus on small molecule in photoresist. The CAR’s Litho performance and the corelated etch performance will be discussed, the component etch rate and its correlation to photoresist etch performance will be covered.
We report on the relationship between resist make-up, filtration process & CH AEI defectivity for an advanced CAR resist with fast dose. In particular, the effect of a pattern transfer scheme on a resist platform with formulation & filtration variation is examined. Resist design & manufacturing strategies for continuous improvement of EUV CAR lithographic performance will be discussed.
Chemically amplified resists (CAR) enable the transition of extreme ultraviolet (EUV) lithography to high-volume manufacture (HVM). Novel photoresists continue to be designed to meet the simultaneous improvement of resolution, line width roughness, and sensitivity (RLS) trade-off. The absorption of EUV photons in the photoresist film leads to emission of primary electrons to form secondary electrons by inelastic scattering events which in turn leads to the activation of the photoacid generator compound. A unique challenge for the use of CAR in EUV lithography is their poor absorption at 13.5nm wavelength. Understanding the photoresist EUV absorption impact on lithographic performance parameters is critical for photoresist design. In this study, we designed photoresist polymers with tuned EUV absorption coefficients by incorporating EUV absorption group(s) onto different CAR polymers. The effect of the EUV absorption increase on polymer properties as well as on resist lithographic performance will be presented.
The drive toward tighter pitch and higher density integrated circuits requires continual advancement in lithography. Advanced photolithography tools use extreme ultraviolet (EUV) light with a wavelength of 13.5nm. The high energy nature of EUV light generates secondary electrons in the photoresist that are responsible for the photochemistry that induces the solubility switch. This distinct mechanism has provided the driving force for the development of new photoresists that are sensitive to EUV and highly reactive toward secondary electrons. Despite the considerable change in acid generation mechanism going from DUV to EUV, chemically amplified photoresists continue to be leading photoresist candidates for new process nodes at low NA EUV (0.33 NA) and their use is expected to extend into early high NA (0.55 NA). Herein the after-developer defects (ADI) and EUV P36 LS trench printing performance of a series of chemically amplified photoresists (CAR) with distinct chemistry developed specifically for EUV lithography are compared. In particular, the relationship of different leaving group chemistries and polymer manufacturing processes on stochastic defectivity is explored as well as the connection to photoresist polymer hydrophobicity and homogeneity. The insights gained from this study guide design strategies for improvement of advanced chemically amplified photoresists for EUV lithography.
Extreme ultraviolet (EUV) lithography technology empowers integrated circuit industry to mass produce chips with smaller pitches and higher density. Along with EUV tool advancement, significant progress has also been made in the development and advancement of EUV chemically amplified resist (CAR) materials, which allows for the improvement of resolution, line edge roughness, and sensitivity (RLS) trade-off. The scarce number of EUV photons has triggered the development of resist material with high absorption at 13.5 nm. However, a review of open literature reveals very limited reports on the effect of high EUV absorption elements on etch properties of advanced EUV resist. To ensure Moore’s Law continues to move forward, further resist performance improvement is required. In this regard, stochastic defects originating from photon shot noise, materials, and processing variabilities present a unique challenge for the extension of CAR platform for the patterning of smaller nodes. Notably, less attention has been paid to defects formed during the etching process used for pattern transfer. In this paper, we report on the relationship between resist make-up and etch properties. In particular, the effect of incorporation of EUV high absorbing elements are examined. New resist material design strategies for continuous improvement of EUV CAR lithographic performance will be discussed.
Chemically amplified resist (CAR) materials are widely used in advanced node patterning by extreme ultraviolet lithography (EUVL). To support the continuous requirement of reducing critical dimension (CD), CAR has been designed to process at tens of nanometer coating thickness while taking into consideration film roughness, aspect ratio, and etch transfer challenge. In this study, we investigated the impact of the photoresist’s different spin speed for same film thickness on resolution, line width roughness, and sensitivity (RLS) trade-off for Line and Space (L/S) patterns. We selected photoresists with identical chemical composition that differed only in total wt solid% in the solution. Photoresist films at constant thickness were investigated for the spin speed impacts on photoresist film density, hydrophobicity on the film surface, and film surface roughness. The corresponding EUV lithographic performance will be presented.
Conventional chemically amplified resists for extreme ultraviolet (EUV) lithography are comprised of three fundamental components: a photoreactive, acid-generating species (PAG), an acid reactive polymer for solubility switching, and a basic component for acid diffusion control. The PAG component is typically derived from an organic onium salt, wherein the cation’s capacity to capture secondary electrons generated upon EUV irradiation of the resist underscores their reactivity in lithographic applications. Thus, effective rational design of these materials is critical for controlling both sensitivity of the resist and feature regularity. Herein, we describe a robust method for in silico prediction of fundamental properties of onium cations including electron affinity, LUMO energy, and relative charge distribution. We correlate these theoretical values to experimental measurements and further to the influence of PAG cation properties on resist performance under EUV exposure. In addition to the reactive properties of these cations, we analyze these lithographic data in the context of the physicochemical properties of the cations, particularly polarity. In all, the results of this study suggest that while electron affinity of the PAG cation may drive reactivity in response to EUV exposure, multiple factors must be considered in the design of cations for optimal overall resist performance.
KEYWORDS: Etching, Absorbance, Carbon, Resistance, System on a chip, Reactive ion etching, Polymers, Image processing, Photoresist materials, Optical lithography
The continued miniaturization of integrated circuit features has been made possible through multilayer patterning processes where different etch steps transfer the patterned photoresist image through various hardmasks and ultimately to the underlying substrate. Spin-on carbons (SOCs) are a type of a solution-dispensable carbon hardmask that can offer excellent resistance to various etch gases for good pattern transfer fidelity, while simultaneously conferring desirable gap fill and planarization properties onto the underlying substrate. We recently reported on the development of a new SOC platform with excellent etch resistance, having a relative reactive ion etch (RIE) rate of 1.08 compared to amorphous carbon. However, one drawback we observed for this polymer was its relatively high absorbance between 400-700 nm which can complicate lithographic alignment. Here we report our work on reducing the absorbance of our SOC platform while maintaining its excellent etch resistance. We identify that the origin of high absorbance is from side reactions that occur during curing and discuss the various polymer modifications or additives that prevent these unwanted processes. We additionally look at any trade-offs that are observed between decreasing absorbance and etch resistance and optimize the SOC’s composition to minimize absorbance while having a minimal effect on its etch resistance.
The development of Chemically Amplified Resists (CARs) for Extreme Ultra-Violet Lithography (EUVL) requires unique molecular and macromolecular design considerations. The combination of photon-induced variation effect coupled with material and processing variabilities makes stochastic consequences in EUV resist significantly more severe than that in ArF resist. Among the other factors, conversion of the scarce number of absorbed EUV photons into imaging events is directly modulated by acid generation quantum yield. In this study, we measure the EUV acid generation efficiency of different Photoacid Generators (PAGs). Our results show that in addition to PAG electronic properties, other structural-driven PAG properties can have a significant impact on resist sensitivity. In a complementary part of this study, we have measured PAG acid generation efficiency under EUV exposure in newly designed polymer matrixes. Such polymers comprise high absorption EUV elements and EUV-specific sensitizers. Insights into the effect of the polymer matrix on EUV acid generation quantum yield are presented.
KEYWORDS: System on a chip, Etching, Thin film coatings, Polymers, Resistance, Carbon, Chemical vapor deposition, Coating, Reactive ion etching, Silicon
In the multilayer patterning process, underlayer material is often used to enable device size shrinkage for advanced integrated circuit manufacturing. This underlayer material, spin on carbon (SOC), with high etch resistance plays an important role in both gap fill and process of transferring high aspect ratio patterns. Good global planarization (PL) performance over various pattern topographies not only impacts on the following lithography process window but also boosts the overall device integration yield (Figure 1). As critical dimension (CD) size decreases in the advanced nodes such as 10 nm and beyond with multiple patterning steps, long range planarizing SOC material is needed to control the CD uniformity. During the single coat and single bake process, thermal flow ability of these carbon rich materials is one of the key property to achieve long range planarization performance. In addition, our strategy for designing long distance thermal flow polymers will be applied to both low/high thermal stability SOC materials. Herein, we report the development of a novel planarized SOC materials with good Fab drain line compatibility. As for material global planarization performance, the observation of flow ability can be monitored through the various cure conditions. Other key performance such as gap fill, etch rate toward various gases, solvent strip resistance and cured film thermal stability will be also highlighted in this paper.
As the critical dimension (CD) in semiconductor devices continues to shrink, the multilayer patterning process to transfer fine line patterns into an underlying substrate is becoming increasingly important. The trilayer processes consist of a photoresist film, a silicon-containing layer and a carbon rich underlayer. The distinctive difference in etch selectivity toward fluorine and oxygen based reactive ion etching (RIE) chemistry is critical to provide highly selective pattern transfer to the substrate. In response to the need for high etch resistant underlayers, we have developed carbon rich spin-on carbon (SOC) materials with good solubility in preferred casting solvents, high thermal stability and high dry etch resistance. To better understand structure-property relationships of high etch resistant SOC films, cured SOC films were analyzed by Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-Vis), X-ray reflectivity (XRR), X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The design considerations for high etch resistance SOC underlayers, such as Ohnishi parameter, crosslinking and film density, will be discussed in this paper.
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