Masahiro Hatakeyama

Fast Atom Beam Etching of Glass Materials with Contact and Non-Contact Masks.

Fast atom beam (FAB) etching of multicomponent glass and silica glass was performed using a contact mask (electron beam resist) and two non-contact masks (typically 5-µ m-diameter particles and a copper mesh with a 5 µ m line width and 20 µ m line spacing). FAB etching of a multi component glass substrate with the micro-particle mask successfully fabricated a precisely projected, 1.0-µ m-high outline pattern on the substrate. FAB etching of a silica glass substrate with the copper-mesh mask, which was separated from the substrate by about 100 µ m, successfully produced a projected, 34-nm-high outline pattern on the substrate. A combination of electron beam lithography with FAB etching on silica glass successfully fabricated nano-scale ultrafine patterns whose aspect ratio was higher than 7 (50 nm line width and 360 nm height). In all three fabrications, the side walls and etched surfaces were very smooth and were perpendicular to each other.

Development of extreme ultraviolet mask pattern inspection technology using projection electron beam optics

Abstract. Extreme ultraviolet (EUV) lithography with a 13.5 nm exposure wavelength is a leading candidate for the next-generation lithography because of its excellent resolution for 16 nm half pitch (hp) node devices and beyond. High sensitivity EUV mask pattern defect detection is one of the major issues to realize device fabrication with EUV lithography. First, to estimate targeted pattern defect detection size, a simulation for defect printability was carried out. In order to achieve the required inspection sensitivity applicable for 1X nm node, a projection electron microscopy (PEM) system was employed, which enabled us to do inspection in higher resolution and with higher speed in comparison to those of the conventional deep ultraviolet and electron beam inspection systems. By incorporating high electron energy and low optical aberration into the PEM, we designed a system for 16 nm hp node defect inspection. To guarantee the quality of the 16 nm node EUV mask, corresponding sized programmed defect masks were designed, and a PEM system defect detection was evaluated by using the current system for 2X nm generation.

Patterned mask inspection technology with projection electron microscope technique on extreme ultraviolet masks

Abstract. High-sensitivity extreme ultraviolet (EUV) mask pattern defect detection is one of the major issues remaining to be addressed in device fabrication using extreme ultraviolet lithography. In order to achieve inspection sensitivity and suitability for the 1× nm node, a projection electron microscope (PEM) system is employed that enables high-speed/high-resolution inspection, which is not possible using conventional deep ultraviolet or electron beam inspection systems. By employing higher electron energy in the electron optics (EO) exposure system and by improving the PEM design, we have minimized the aberration that occurs when working with EO systems and we have improved the transmittance of the system. Experimental results showing the improved transmittance were obtained by making electron throughput measurements. To guarantee the tool’s aptness for 16-nm node EUV mask inspection, corresponding sized programmed defects on masks were designed, and the defect detection sensitivity of the EO system was evaluated. Improvements in image resolution and electron throughput have enabled us to detect 16-nm sized defects. The PEM system was integrated into a pattern inspection system for defect detection sensitivity evaluation.

Performance of EBeyeM for EUV Mask Inspection

According to the ITRS Roadmap, the EUV mask requirement for 2X nm technology node is detection of defect size of 20 nm. The history of optical mask inspection tools involves continuous efforts to realize higher resolution and higher throughput. In terms of productivity, considering resolution, throughput and cost, we studied the capability of EUV light inspection and Electron Beam (EB) inspection, using Scanning Electron Microscope (SEM), including prolongation of the conventional optical inspection. As a result of our study, the solution we propose is EB inspection using Projection Electron Microscope (PEM) technique and an image acquisition technique to acquire inspection images with Time Delay Integration (TDI) sensor while the stage is continually moving. We have developed an EUV mask inspection tool, EBeyeM, whole design concept includes these techniques. EBeyeM for 2X nm technology node has the following targets, for inspection sensitivity, defects whose size is 20 nm must be detected and, for throughput, inspection time for particle and pattern inspection mode must be less than 2 hours and 13 hours in 100 mm square, respectively. Performance of the proto-type EBeyeM was reported. EBeyeM for 2X nm technology node was remodeled in light of the correlation between Signal to Noise Ratio (SNR) and defect sensitivity for the proto-type EBeyeM. The principal remodeling points were increase of the number of incident electrons to TDI sensor by increasing beam current for illuminating optics and realization of smaller pixel size for imaging optics. This report presents the performance of the remodeled EBeyeM (=EBeyeM for 2X nm) and compares it with that of the proto-type EBeyeM. Performances of image quality, inspection sensitivity and throughput reveal that the EBeyeM for 2X nm is improved. The current performance of the EBeyeM for 2X nm is inspection sensitivity of 20 nm order for both pattern and particle inspection mode, and throughput is 2 hours in 100 mm square for particle inspection mode.

EUV patterned mask inspection system using a projection electron microscope technique

The concept and the current status of a newly developed PEM pattern inspection system are presented. An image-processing technique with learning functions to enhance the system’s detection capability is investigated. Highly accelerated electrons employed here in electron-optics function as an enabler to improve the image resolution and transmittance in the system, and to acquire an image contrast of 0.5 in a half pitch (hp) 64 nm lines and space pattern. This process also results in the formation of an electron image with more than 3000 electrons per pixel on a sensor. The image-processing system was also developed for die-to-die inspection. The alignment error is minimized to a negligibly small size by a continuous 2D pattern matching. An ensemble of signal characteristics enables the identification of any defect signal in a noisy electron image. The developed detection system met the requirements for hp16 nm generation.

Characterization of neutral beam source using dc cold cathode discharge and its application processes

Fast atom beam (FAB) sources using dc cold cathode discharge, comprising parallel plate electrodes and thick carbon plate cathodes with multiple beam extracting apertures, were developed to generate parallel and straight energetic neutral beams for precise etching of three-dimensional microstructures consisting of insulating materials. Conventional FAB sources and their applications are briefly reviewed, and the advantages of newly developed FAB sources and new applications are introduced. By using SF6 gas, a precise etching of quartz glass with an etch rate of 30 nm min−1, a uniformity of within 4% (P–V) in O76 mm, vertical etch profile, smooth etch surface and long-term etch rate stability over 250 min were realized. The neutralization coefficient and the beam current density were also measured using a secondary electron method and a pulse-counting method, making it possible to measure the neutralization coefficient without referring to databases for secondary electron yields. A neutralization coefficient of 98% was obtained at maximum, although, under practical etching conditions, the neutralization coefficient is less than 70%. By comparing the results of the simple model calculation with the experimental data, it was determined that the neutralization mechanism was dominated by charge transfer. The importance of neutralization in a process chamber is also discussed.

Development of inspection system for EUV mask with novel projection electron microscopy (PEM)

In order to realize EUV mask pattern defect inspection in 16nm node, we have developed new optics on a novel projection electron microscopy (PEM) and a new inspection system with the new optics and a new mask handling and imaging units, e.g., a high precision stage, an imaging detector, an imaging processing system, and so. on. This inspection system enables us to make the inspection in high resolution and high speed as compared with conventional DUV and EB inspection systems. The new optics on the novel PEM comprises an exposure and an imaging electron beam optics (EOs). The optics is based on the new design concept to meet the required progress for 1Xnm EUV mask inspection as compared to the current inspection system for 2Xnm node; The concept employs new techniques to achieve the features: high energetic electron imaging optics to have low aberration, high transmittance efficiency, e.g., on the ratio of exposure current/emitted current, in the exposure and the imaging optics, respectively. The new handling and imaging system are also based on the design concept of imaging in high resolution by combination operation among the new optics on the novel PEM, the stage, and the detector. In this paper, we describe the basic performance evaluation as concerning these features and the operation: 1) MTF inclination in hp44~100nm L/S pattern of the developed imaging optics. 2) Secondary electron imaging by the integrated optics, i.e., both of the exposure and the imaging EOs, on the novel PEM, 3) Secondary electron image acquisition operation in still mode on the new inspection system assembled with the new optics on the novel PEM, the high precision stage, the detector, and so. on.. The results show the new optics on the novel PEM is capable to meet the required progress for 1Xnm EUV mask inspection and the new inspection system with the novel PEM operates in much feasibility in the electron image acquisition.

Development of EB inspection system EBeyeM for EUV mask

We are developing new electron beam inspection system, named EBeyeM, which features high speed and high resolution inspection for EUV mask. Because EBeyeM has the projection electron microscope technique, the scan time of EBeyeM is much faster than that of conventional SEM inspection system. We developed prototype of EBeyeM. The aim of prototype system is to prove the concept of EBeyeM and to estimate the specification of system for 2Xnm and 1Xnm EUV mask. In this paper, we describe outline of EBeyeM and performance results of the prototype system. This system has two inspection mode. One is particle inspection and the other is pattern defect inspection. As to the sensitivity of EBeyeM prototype system, the development target is 30nm for the particle inspection mode and 50nm for pattern defect inspection mode. The performance of this system was evaluated. We confirmed the particle inspection mode of the prototype system could detect 30nm PSL(Polystyrene Latex) and the sensitivity was much higher than conventional optical blank inspection system. And we confirmed that the pattern defect sensitivity of the prototype system was around 45nm. It was recognized that both particle inspection mode and pattern defect inspection mode met the development target. It was estimated by the performance results of the prototype system that the specification of EBeyeM would be able to achieve for 2Xnm EUV mask. As to 1Xnm EUV mask, we are considering tool concept to meet the specification.

Printing Sub-100 Nanometer Features Near-Field Photolithography

In this paper, a near-field photolithographic method which can realize ultra high resolution beyond the diffraction limit of light is described. Evanescent light generated on a transparent mold with a micro-relief illuminated on the condition of total internal reflection is used to expose a photoresist in contact with the mold. The plastic replica mold is flexible to eliminate the difficulty of close contact with the photoresist, and the replica mold damaged by the contact with the photoresist is disposable to maintain a high yield rate. We printed sub-100 nm features on a commercially available photoresist using 442-nm-wavelength light.

Integration of 3-D shape construction and assembly to realize micro systems

In order to make micro 3-D structures, we are designing a table-sized factory, namely “Nano Manufacturing World (NMW)”. In NMW, we challenged to use a new process fused by semiconductor process for preciseness and machine process for 3-dimensionality. In order to realize the new process, we designed three new mechanisms in this paper: multi-face shape making beam, co-focus rotational robot and micro mechanical tools. Through an evaluation to actually make a micro “Gojunoto” with the mechanisms, we confirmed their validities for functions of integration of 3-D shape construction and assembly.