Hironori Noguchi

High-performance laser tracker using an articulating mirror for the calibration of coordinate measuring machine

A high-performance laser tracker that is used for the calibration of a coordinate measuring machine (CMM) is introduced. A specially designed hemispherical-shape articulating mirror is used in the tracking mechanism, which enables reduction of the measurement uncertainties so that they are not more than 0.3 ?m. The uncertainty analysis of the laser tracker is also described.

Development of a ball step-gauge and an interferometric stepper used for ball-plate calibration

We propose a new design artifact for the calibration of ball-plates, which are used to assess the performance of coordinate-measuring machines (CMMs) and to calibrate those. Though transferring a length standard is necessary for ball-plate calibration, gauge-blocks are usually used for it. We think that the gauge-blocks are not appropriate gauges for transferring the length standard because of their shape. Therefore, we develop a new artifact, which we call a ball step-gauge. The ball step-gauge consists of a steel bar having the shape of an H and seven ceramic balls. It is rigid and lightweight. In addition, it can be calibrated precisely using special equipment with a laser interferometer; thus it can be used as a transfer length standard in the ball-plates calibration; furthermore, we discuss the uncertainties in measurements using the new interferometric equipment we developed.

Evaluation of the performance of a novel laser tracker used for coordinate measurements

A laser tracking interferometer system (LTS), which can measure 3D coordinates, has been developed in our laboratory. The LTS makes use of the principle of laser trilateration. The principle satisfies Abbes principles and the coordinates are calculated solely form length measurements. Consequently, measurements directly traceable to length standard can be achieved. The first generation trackers, however, were large, heavy and not so accurate. So, we developed a compact, accurate laser tracker. It has a hemisphere mirror, which is used as a tracking mirror and is driven by an X-Y moving table. The performance of this laser tracker was checked by a high precision coordinate measuring machine. The results of the experiments show that the displacement measuring error of this laser tracker is below 0.6 micrometers , which is much better than any other conventional laser trackers.

AFM measurement of linewidth with sub-nanometer scale precision

A critical-dimension atomic force microscope system equipped with an ultra-high resolution, three-axis laser interferometer was constructed and tested. The MIRAI (Millennium Research for Advanced Information Technology) project has been improving the precision of critical dimension measurements with atomic force microscopy (AFM) by implementing modularized laser interferometers, to meet requirements for dimensional measurement in 45 nm technology node. The stability of the cross-sectional profile of an AFM image for a rectangular cross-section was greatly improved by optimizing interferometer linearity and resolution with DSP signal processing and reducing the angular motion and mechanical vibration of the monolithic three-dimensional probe scanner with a unique parallel spring mechanism. The repeatability of linewidth measurement of a nominal 100 nm linewidth along the same scanned line showed a standard deviation of 0.5-1.0 nm (3-sigma). This shows AFM to be one of the most promising metrological tools for next-generation nanodevice fabrication processes. Instrumentation, measurement results, and precision will be discussed.

Compact high-resolution homodyne interferometer for nanometer-scale multidimensional AFM metrology

A design of a high-resolution homodyne interferometer is presented, modularized, and installed in a prototype, critical-dimension atomic force microscope (CD-AFM). A newly designed symmetrical layout of the optical path of the homodyne interferometers enabled highly stable measurements of the mechanical displacements of a wafer-positioning stage and an AFM scanner. In the performance measurement of the wafer-positioning stage, the mechanical drift after long-stroke travel and unlocking of the servo control was reduced to less than ten nanometers per minute by optimizing the preceding motion before stopping. An AFM scanner with a three-dimensional (3D) parallel spring structure has been implemented for the interferometer modules. Using a DSP-based electronic interpolation technique, displacement of the scanner was resolved and calibrated at better than 50 pm and 200 pm, respectively.

Ultraprecision CD Metrology for Sub‐100 nm Patterns by AFM

The MIRAI project has been improving the precision of critical dimension measurements with atomic force microscopy (AFM) by implementing modularized laser interferometers to meet requirements for dimensional measurement at the 45 nm technology node. Recent advances in semiconductor process technologies require a breakthrough in nanometer‐pattern dimensional measurement on large wafers such as linewidth, hole diameter, and depth. AFM is promising method to meet this need because of its spatial atomic‐level resolution along three axes. The higher the resolution is, the better we can know geometrical shape of a target pattern. We discuss the design of a high‐resolution homodyne interferometer modularized and installed in a critical‐dimension AFM (CD‐AFM) prototype. The symmetrical optical path layout of the homodyne interferometer makes measurement of the mechanical displacements of an AFM scanner highly stable. The stability of the cross‐sectional AFM profile for a pattern with a rectangular cross‐section w...