Hajime Kawano

Superconducting magnet apparatus using superconducting multilayer composite member, method of magnetizing the same and magnetic resonance imaging system employing the same

A superconducting magnet apparatus which includes a cryostat vessel for containing therein a coolant for realizing superconductivity, a magnetic flux generating unit disposed within the cryostat vessel and including a superconducting multilayer composite member constituting a sustaining medium for a persistent current which generates a magnetic flux along a center axis of a predetermined magnetic field space, and members holding the magnetic field generating unit within the cryostat vessel.

Recent progress in cell-projection electron-beam lithography

This paper reviews and introduces recent methods for enhancing the performance of cell-projection lithography and describes various useful applications of this type of lithography. To increase the throughput, the area of the e-beam mask that is available for cell apertures was four-times increased. For enhanced lithographic resolution, the resolution in cell-beam measurement was enhanced. The method that uses transmitted electrons through a very fine hole in the stencil was improved. Much higher resolution is achieved compared as before. Moreover, several applications of cell-projection lithography were demonstrated to show its advantages. They included lithography in the fabrication of photo-masks and magnetic head devices those use plural cell apertures.

Technological capability and future enhanced performance of HL-7000M

HL-7000M electron beam lithography system has been developed as a state-of-the-art reticle writer for the generation of 90nm node production and 65nm node development. It is capable of handling relatively large volume data files such as full Optical Proximity Correction patterns and angled patterns for System on Chip. Aiming at technological requirements, a newly designed electron optics column generating a vector-scan variable shaped beam and a digital disposition system with a storage area network technology have been integrated into HL-7000M. Since the requirement on the critical dimension uniformity is extremely demanding on the ITRS roadmap, HL-7000M has also needed to improve its beam shaping performance. The ability relevant to shaping beam size has a great impact on its line width or critical dimension accuracy. To reduce an aberration caused within the shaping lens system, the dual quadrupole electrostatic shaping deflector has been utilized. By applying advanced technologies, HL-7000M with a result of critical dimension uniformity (2.5nm and 2.8nm in 3σ) has achieved meeting its target requirement of the 90nm generation for production. Additionally HL-7000M has proved its potential, allowing the industry to establish quickly the processes further beyond the requirements of the 65nm node for development.

Recent CD accuracy improvements for HL-7000M

A new electron beam mask writer, HL-7000M, has been developed for mass production of 90 nm node photomask and, research and development of 65 nm node mask. A series of adjustments to improve CD accuracy provides us a novel systematic solution for VSB system optimization. By applying a novel constant-gain method for linearity adjustment, linearity range, for designed size ranging from 0.3 um to 1.0 um, has been improved to < 3 nm for line and space pattern, the maximum XY discrepancy is 2 nm. Both experimental and theoretical studies for shot-divided patterns, which are often generated in OPC pattern conversion, have been applied. By modification of the shift term in beam size correction, exposure results for such shot-divided patterns, for divided pattern size varied from 500 nm to 1 nm, are improved to be less than 5 nm in range.

Influence of e-beam aperture angle on CD-SEM measurements for high-aspect ratio structure

The influence of e-beam aperture angle on CD-SEM measurements for a high aspect ratio (HAR) structure was investigated. The Monte-Carlo simulator JMONSEL was used to evaluate the measurement sensitivity to the variation in the bottom CD. The aperture angle of the primary electron greatly influences the measurement accuracy of the bottom CD in the HAR structure. Then, we utilized a technique for energy-angular selective detection to the Monte-Carlo simulation results and found that the measurement sensitivity for the large aperture angle was improved. In addition, the experimental results were qualitatively consistent with the results of the Monte-Carlo simulation. These results indicate that the detection is effective for the bottom CD measurement of a HAR structure.

SEM imaging capability for advanced nano-structures and its application to metrology

In recent trend of semiconductor manufacturing, accurate critical dimension (CD) metrology is required to realize miniaturized three-dimensional (3D) structures. However, the conventional edge contrast of scanning electron microscopy (SEM) is often suppressed when imaging the deep bottom of the 3D structures. In this paper, we propose effective approaches realizing the improved SEM image contrast for such metrology targets. Our approach utilizes the principle of the SEM contrast, and optimizes the three major influencing factors of SEM contrast; signal generation, signal propagation inside the specimen, and signal detection by the detectors. We show the examples of improved image contrast including, embedded voids imaging by high landing beam energy, contact-hole bottom imaging by angular selective detections, and precise edge position extraction realized by energy-angular selective imaging.

High-precision CD measurement using energy-filtering SEM techniques

Abstract. Voltage contrast (VC) images obtained using an energy filter (EF) were used to measure the bottom surface of high-aspect-ratio structures. The VC images obtained using the conventional EF were sensitive to variations in wafer potential. Since CD-SEM metrology requires precise EF voltage control when using VC images, we developed an EF voltage correction method to be used at each measurement point. Consequently, bottom-edge measurement, independent of the wafer potential fluctuations, was achieved using the newly developed EF. Our developed technique is effective for CD-SEM metrology using VC images.

Advanced CD control technologies for EB mask writer

With the rapid progress in the minimization in the device fabrication, it comes to be indispensable to reduce Critical Dimensional (CD) error in the mask production. The electron beam mask lithography system HL-7000M series has been developed, to meet the needs for mass production line below 90 nm node. A novel high-accuracy Proximity Effect Correction (PEC) method of exposure correction for pattern density variation is applied in this system. By using this high accuracy PEC method, CD error caused by proximity effects has been reduced to 4 nm, from 14 nm with the conventional PEC method.

Improved Image Placement Performance of HL-7000M

HL-7000M electron beam (EB) lithography system has been developed as a leading edge mask writer for the generation of 90 nm node production and 65 nm node development. It is capable of handling large volume data files such as full Optical Proximity Correction (OPC) patterns and angled patterns for System on Chip (SoC). Aiming at the technological requirements of the International Technology Roadmap for Semiconductors (ITRS) 2002 Update, a newly designed electron optics column generating a vector-scan variable shaped beam and a digital disposition system with a storage area network technology have been implemented into HL-7000M. This new high-resolution column and other mechanical components have restrained the beam drift and fluctuation factors. The improved octapole electrostatic deflectors with new dynamic focus correction and gain alignment methods have been built into the object lens system of the column. These enhanced features are worth mentioning due to the achievement of HL-7000Ms Image Placement (IP) performance. Its accuracy in 3σ of a 14 x 14 global grid matching result over an area of 135 mm x 135 mm measured by Leica LMS IPRO are X: 6.09 nm and Y: 7.85 nm. In addition, the shot astigmatism correction has been in the development and testing process and is expected to improve the local image placement accuracy dramatically.