Search

Extreme ultraviolet (EUV) lithography (13.5 nm) is the newest technology that allows high-throughput fabrication of electronic circuitry in the sub-20 nm scale. It is commonly assumed that low-energy electrons (LEEs) generated in the resist materials by EUV photons are mostly responsible for the solubility switch that leads to nanopattern formation. Yet, reliable quantitative information on this electron-induced process is scarce. In this work, we combine LEE microscopy (LEEM), electron energy loss spectroscopy (EELS), and atomic force microscopy (AFM) to study changes induced by electrons in the 0–40 eV range in thin films of a state-of-the-art molecular organometallic EUV resist known as tin-oxo cage. LEEM–EELS uniquely allows to correct for surface charging and thus to accurately determine the electron landing energy. AFM postexposure analyses revealed that irradiation of the resist with LEEs leads to the densification of the resist layer because of carbon loss. Remarkably, electrons with energies as low as 1.2 eV can induce chemical reactions in the Sn-based resist. Electrons with higher energies are expected to cause electronic excitation or ionization, opening up more pathways to enhanced conversion. However, we do not observe a substantial increase of chemical conversion (densification) with the electron energy increase in the 2–40 eV range. Based on the dose-dependent thickness profiles, a simplified reaction model is proposed where the resist undergoes sequential chemical reactions, first yielding a sparsely cross-linked network and then a more densely cross-linked network. This model allows us to estimate a maximum reaction volume on the initial material of 0.15 nm3 per incident electron in the energy range studied, which means that about 10 LEEs per molecule on average are needed to turn the material insoluble and thus render a pattern. Our observations are consistent with the observed EUV sensitivity of tin-oxo cages.

Organic-inorganic hybrid compounds are arising as promising resist materials for extreme-ultraviolet (EUV) lithography, a new technique introduced in the semiconductor industry for the fabrication of integrated circuits of sub-10 nm feature size. In this work, we show that the sensitivity to EUV radiation of zirconium oxo clusters with methacrylate ligands is substantially enhanced when a small fraction of the ligands are replaced by trifluoromethylacrylates. We studied the details of the chemical changes that occur in thin films of the precursor and the partially fluorinated materials using scanning transmission X-ray microscopy (STXM) and X-ray photoelectron spectroscopy (XPS). Evidence is presented for radical chain polymerization as a mechanism for the solubility switch. Yet, XPS results also indicate that Zr-F bonds are formed during the exposure to EUV light in the fluorinated material, dissociative electron attachment being likely involved. Our observations show that, while fluorinated ligands enhance EUV absorption, their effect on the reactivity of the material might be more critical, thereby contributing to an increase in the sensitivity of the resist in both ways.

Inorganic molecular materials such as tin oxo cages are a promising generation of photoresists compatible with the demands of the recently developed Extreme UltraViolet (EUV) lithography technology. Therefore, a detailed understanding of the photon-induced reactions which occur in photoresists after exposure is important. We used XUV broadband laser pulses in the range of 25-40 eV from a table-top high-harmonic source to expose thin films of the tin oxo cage resist to shed light on some of the photo-induced chemistry via XUV absorption spectroscopy. During the exposure, the transmitted spectra were recorded and a noticeable absorbance decrease was observed in the resist. Dill parameters were extracted to quantify the XUV induced conversion and compared to EUV exposure results at 92 eV. Based on the absorption changes, we estimate that approximately 60% of tin-carbon bonds are cleaved at the end of the exposure., 8 pages, 8 figures

We report on the dual-tone property of the tin-oxo cage (BuSn)l20I4(0H)6](0H)2 photoresist. After exposing the resist film to a low dose extreme ultraviolet radiation or electron beam, applying a post exposure bake step and development with isopropanol/H20 (2:1), a positive tone image is observed. The previously observed negative tone is found at higher doses. Atomic force microscopy and scanning electron microscopy were used to characterize the topography of the patterns. X-ray photoelectron spectroscopy was used to elucidate the chemical changes of the tin-oxo cages under different conditions. The photoresist, which has dual-tone property, paves the way to fabricate sophisticated structures in a single photoresist layer or may lead to metal-containing resists with improved sensitivity. Keywords: Dual-tone photoresist, EUV photoresist, Inorganic photoresist, Tin-oxo cages, Tone conversion, Mechanism

Organotin oxo cage compounds have an electronic absorption band in the UV spectral range (λmax ~220 nm) associated with a σd electronic transition. Irradiation at 225 nm of thin films of these materials leads to loss of carbon, as shown by X-ray Photoelectron Spectroscopy. Photolysis of solutions of the compounds causes a decrease and slight broadening of the absorption band, consistent with replacement of the organic groups. Quantum chemical calculations support the breaking of the tin-carbon bonds as the primary process, both in electronically excited states and in oxidized states that can be expected to be the result of EUV photoionization.

Tin-oxo cage materials are of interest for use as photoresists for EUV (Extreme­ Ultraviolet) lithography (13.5 run, 92 eV), owing to their large absorption cross section for EUV light. In this work we exposed an n-butyl tin-oxo cage dication in the gas phase to photons in the energy range 4-14 eV to explore its fundamental photoreactivity. At all energies above the onset of electronic absorption at 5 eV (250 run) cleavage of tin-carbon bonds was observed. With photon energies >12 eV (

We report on the extreme ultraviolet (EUV) patterning performance of tin-oxo cages. These cage molecules were already known to function as a negative tone photoresist for EUV radiation, but in this work, we significantly optimized their performance. Our results show that sensitivity and resolution are only meaningful photoresist parameters if the process conditions are optimized. We focus on contrast curves of the materials using large area EUV exposures and patterning of the cages using EUV interference lithography. It is shown that baking steps, such as postexposure baking, can significantly affect both the sensitivity and contrast in the open-frame experiments as well as the patterning experiments. A layer thickness increase reduced the necessary dose to induce a solubility change but decreased the patterning quality. The patterning experiments were affected by minor changes in processing conditions such as an increased rinsing time. In addition, we show that the anions of the cage can influence the sensitivity and quality of the patterning, probably through their effect on physical properties of the materials.