International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

A self-scanned 1024 element photodiode array and minicomputer are used to measure the phase (wavefront) in the interference pattern of an interferometer to lambda/100. The photodiode array samples intensities over a 32 x 32 matrix in the interference pattern as the length of the reference arm is varied piezoelectrically. Using these data the minicomputer synchronously detects the phase at each of the 1024 points by a Fourier series method and displays the wavefront in contour and perspective plot on a storage oscilloscope in less than 1 min (Bruning et al. Paper WE16, OSA Annual Meeting, Oct. 1972). The array of intensities is sampled and averaged many times in a random fashion so that the effects of air turbulence, vibrations, and thermal drifts are minimized. Very significant is the fact that wavefront errors in the interferometer are easily determined and may be automatically subtracted from current or subsequent wavefrots. Various programs supporting the measurement system include software for determining the aperture boundary, sum and difference of wavefronts, removal or insertion of tilt and focus errors, and routines for spatial manipulation of wavefronts. FFT programs transform wavefront data into point spread function and modulus and phase of the optical transfer function of lenses. Display programs plot these functions in contour and perspective. The system has been designed to optimize the collection of data to give higher than usual accuracy in measuring the individual elements and final performance of assembled diffraction limited optical systems, and furthermore, the short loop time of a few minutes makes the system an attractive alternative to constraints imposed by test glasses in the optical shop.

Digital wavefront measuring interferometer for testing optical surfaces and lenses

For measuring machines and machine tools, geometrical accuracy is a key performance criterion. While numerical compensation is well established for CMMs, it is increasingly used on machine tools in addition to mechanical accuracy. This paper is an update on the CIRP keynote paper by Sartori and Zhang from 1995 [Sartori S, Zhang GX (1995) Geometric error measurement and compensation of machines, Annals of the CIRP 44(2):599–609]. Since then, numerical error compensation has gained immense importance for precision machining. This paper reviews the fundamentals of numerical error compensation and the available methods for measuring the geometrical errors of a machine. It discusses the uncertainties involved in different mapping methods and their application characteristics. Furthermore, the challenges for the use of numerical compensation for manufacturing machines are specified. Based on technology and market development, this work aims at giving a perspective for the role of numerical compensation in the future.

Geometric error measurement and compensation of machines : an update

Laser Doppler Vibrometry: Development of advanced solutions answering to technology's needs

Recent interest in high-speed scanning probe microscopy for high-throughput applications including video-rate atomic force microscopy and probe-based nanofabrication has sparked attention on the development of high-bandwidth flexure-guided nanopositioning systems (nanopositioners). Such nanopositioners are designed to move samples with sub-nanometer resolution with positioning bandwidth in the kilohertz range. State-of-the-art designs incorporate uniquely designed flexure mechanisms driven by compact and stiff piezoelectric actuators. This paper surveys key advances in mechanical design and control of dynamic effects and nonlinearities, in the context of high-speed nanopositioning. Future challenges and research topics are also discussed.

/pdf/invited-review-article-high-speed-flexure-guided-4qdbjhhogg.pdf

Invited review article: high-speed flexure-guided nanopositioning: mechanical design and control issues.

Non-destructive profiling of the front and rear surfaces of a transparent media by optical interferometry is described. Interferometric measurement of a transparent parallel media leads to problems of multiple-beam interference noise between the two surfaces. A wavelength scanning interferometer with new sampling functions can determine both surface shapes simultaneously suppressing internal reflection noises less than order of R 2 (lambda) where R is the reflection index of the media and (lambda) is the source wavelength.

Wavefront sensing of a rear-surface reflection through a transparent media suppressing multiple-beam interference effect

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 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. Repeated 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. We detail instrumentation, performance, and measurement results.

/pdf/ultraprecision-cd-metrology-for-sub-100-nm-patterns-by-afm-4hsvznvjud.pdf

Ultraprecision CD Metrology for Sub‐100 nm Patterns by AFM

Key techniques for optical frequency measurements including laser stabilization, frequency conversion using nonlinear devices and a phase loc kare presented. Also described are conventional frequency comparison systems which link the 133Cs frequency standard to the infrared or the visible by a heterodyne or an interferometric method. Novel schemes proposed for optical frequency divisionand synthesis are reviewed. Applications of optical frequency measurements are discussed.

https://www.jstage.jst.go.jp/article/lsj1973/19/8/19_8_746/_pdf

New Era in Optical Frequency Measurements

Joint experiments on the calibration of the ball-plate by Poland and Japan

PROBLEM TO BE SOLVED: To provide a light tracking laser interferometer for measuring range capable of minimizing the movement of the origin of interference measurement even in the case that an optical axis orientation is changed. SOLUTION: A light lever with oscillational movement is disposed in an optical path of an interference optical system, and a laser light is projected on the center of reflective surface of the optical lever with oscillational movement. A reflected light can be changed in arbitrary directions by controlling the optical lever with oscillational movement. The reflected light is projected onto a retro-reflector as an object to be measured, and the tracking is carried out. COPYRIGHT: (C)2002,JPO

Tomizo Kurosawa

Papers

Wavefront sensing of a rear-surface reflection through a transparent media suppressing multiple-beam interference effect

Ultraprecision CD Metrology for Sub‐100 nm Patterns by AFM

New Era in Optical Frequency Measurements

Joint experiments on the calibration of the ball-plate by Poland and Japan

Light tracking type laser interferometer for measuring range using optical lever with oscillational movement