Electron projection lithography (EPL) has high-resolution capability of meeting the 45-nm technology node, especially for the “hole” process. A first-generation EPL has been developed and improved at Nikon and Selete. Defect free mask is indispensable for successful introduction of this technology into the production stage. However, an EPL mask is considerably different from today's optical photomask, especially due to its 3-D structure. Hence the conventional methods of quality assurance used for optical photomask are not applicable for EPL mask. Selete is now developing a series of defect inspection and repair systems for an EPL stencil mask infrastructure. In our previous work we verified a number of defect inspection and repair systems through a sequential process. We confirmed good sensitivity for ”hole” inspection, and accuracy of consistent template repair method through the various hole-defect types. Based on our previous work, here in this work we focus on Gas Assisted Etching (GAE) because the majority of the defects are black type defects in smaller features, especially at 45-nm node. The motivation here is to investigate on GAE repair for real usage at 45-nm node. In this paper we verified the capability of repair technology for isolated holes including smaller features. Moreover, we confirmed that the problems encountered in dense hole forming can be resolved.
We have studied stencil mask repair technology with focused ion beam and developed an advanced mask repair tool for electron projection lithography. There were some challenges in the stencil mask repair, which were mainly due to its 3-dimensional structure with aspect ratio more than 10. In order to solve them, we developed some key technologies with focused ion beam (FIB). The transmitted FIB detection technique is a reliable imaging method for a 3-dimensional stencil mask. This technique makes it easy to observe deep patterns of the stencil mask and to detect the process endpoint. High-aspect processing can be achieved using gas-assisted etching (GAE) for a stencil mask. GAE enables us to repair mask patterns with aspect ratio more than 50 and very steep sidewall angle within 90±1°precisely. Edge placement accuracy of the developed tool is about 14nm by manual operation. This tool is capable to achieve less than 10nm by advanced software. It was found that FIB technology had capability to satisfy required specifications for EPL mask repair.
ZnO nanodots have been successfully fabricated on a (001) Al<SUB>2</SUB>O<SUB>3</SUB> substrate by photo-enhanced chemical vapor deposition (PE-MOCVD) combined with near-field optical technology. The optical near-field generated from an optical fiber probe tip allowed ZnO dots to selectively grow on the irradiated substrate surface, with a size smaller than the wavelength of the light source (λ=244 nm). The crystallinity and composition of ZnO were evaluated from planar films using x-ray diffraction analysis, optical transmittance and x-ray photoelectron spectroscopy. The planar films were grown using PE-MOCVD with a direct irradiation by an ultraviolet light source without probe tip. Above a deposition temperature of 150°C, stoichiometric ZnO films (R O:Zn=1), strongly the c-axis oriented and exhibiting a band gap of about 3.3 eV were obtained.
In-situ patterning of nano-scale Zn dots and lines has been succeeded by photodissociation of a gas-phase diethylzinc in optical near-field. By using an optical fiber probe with the aperture diameter of 60 nm, dots with full width at half maximum of approximately 60 nm and approximately 70 nm, closely separated by 100 nm were fabricated. It implies that finer patterns of a metal can be fabricated by using optical fiber probe with smaller aperture, allowing control of the size and position of nano-scale structures. Consequently, the technique is the one of most suitable for nano-photonic device fabrication.