Evaluation of Thermal and Radiation Induced Chemistries of Metal Oxo–Hydroxo Clusters for Next-Generation Nanoscale Inorganic Resists

Abstract

Thin films formed by the condensation of metal oxo–hydroxo clusters offer a promising approach to ultrahigh-resolution patterning including next-generation photolithography using extreme ultraviolet (EUV) radiation and electron-beam lithography. In this work, we elucidate the thermal and radiative mechanisms that drive the chemical transformations in these materials and therefore control the patterning performance. Beginning from aqueous hafnium clusters, peroxide and sulfate additions serve to modify the clusters and, upon spin coating to form a thin film, provide the chemical contrast necessary to create resist. The coordination and functionality of peroxide and sulfate in hafnium-based metal oxo–hydroxo clusters were monitored at various stages of the patterning process which provided insight into the chemical and structural evolution of the material. Peroxide serves as the radiation sensitive species while sulfate enhances solubility and controls the concentration of hydroxide in the films. Peroxide and hydroxide species decompose via radiative and thermal energy, respectively, to form hafnium oxide; controlling these processes is central to the function of the resist.

Ambient-Pressure X-ray Photoelectron Spectroscopy Characterization of Radiation-Induced Chemistries of Organotin Clusters

“…It is expected that further removal of butyl ligands or oxidation of Sn occurs during the development process, which includes a 170 °C anneal in air and soaking in 2-heptanone. Further investigation of the composition following both anneal and developer soak are necessary to obtain a complete understanding of the solubility transition mechanism . By investigating ambient gases with different oxidative strength, we can also determine how they could be added during the EUV processes using a DGL membrane or how related species could be integrated into the resist to improve EUV sensitivity.…”

XUV Induced Bleaching of a Tin Oxo Cage Photoresist Studied by High Harmonic Absorption Spectroscopy

“…Compared to the traditional organic resists the metal atoms in the inorganic cores provide high etch resistance and high absorption cross sections, which may help to reduce stochastic noise. The small and well-defined sizes of molecular materials potentially allow small lineedge roughness [2][3][4][5][6][7].…”

Organotin Carboxylate Reagents for Nanopatterning: Chemical Transformations during Direct-Write Electron Beam Processes

“…Although there are a wide variety of chemistries that can occur for each of these types of materials, the products formed during the patterning reaction are often presumed to be dense metal oxides . For example, in metal oxide sulfate (MSO x ) cluster materials mixed with hydrogen peroxide, radiation-induced peroxide desorption and subsequent condensation lead to M–O–M crosslinking, prompting a solubility change. ,, Metal oxide nanoparticle resists have been developed that are stabilized by photosensitive ligands or photoacid generators that decompose under UV irradiation, causing changes in solubility that lead to particle agglomeration. ,,, In other cases, nanoparticles stabilized by long-chain organic ligands undergo crosslinking when exposed to electrons or X-rays . For organometallic clusters, it is hypothesized that irradiation drives the decomposition of organic groups, followed by crosslinking of metal and oxygen bonds to create an insoluble network. ,,, We have previously demonstrated the loss of butyl ligands in resists deposited from two model organotin species. − The irradiation products that form from each of these inorganic resists, or reagents, have the potential to be used for a variety of direct-write applications.…”

“…11 For example, in metal oxide sulfate (MSO x ) cluster materials mixed with hydrogen peroxide, radiation-induced peroxide desorption and subsequent condensation lead to M−O−M crosslinking, prompting a solubility change. 8,19,20 Metal oxide nanoparticle resists have been developed that are stabilized by photosensitive ligands or photoacid generators that decompose under UV irradiation, causing changes in solubility that lead to particle agglomeration. 1,4,18,21 In other cases, nanoparticles stabilized by long-chain organic ligands undergo crosslinking when exposed to electrons or X-rays.…”