A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

4.1. Nanomachining with Scanning Probes 1831 4.2. Soft Lithography 1832 4.3. Embossing with Rigid Masters 1835 4.4. Near-Field Phase-Shifting Photolithography 1835 4.5. Topographically Directed Photolithography 1837 4.6. Topographically Directed Etching 1837 4.7. Lithography with Neutral Metastable Atoms 1838 4.8. Approaches to Size Reduction 1839 5. Techniques for Making Regular or Simple Patterns 1839

https://www.engr.colostate.edu/ECE581/fall07/xia%20chem%20rev%2099.pdf

Unconventional Methods for Fabricating and Patterning Nanostructures.

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

The phase-shifting mask consists of a normal transmission mask that has been coated with a transparent layer patterned to ensure that the optical phases of nearest apertures are opposite. Destructive interference between waves from adjacent apertures cancels some diffraction effects and increases the spatial resolution with which such patterns can be projected. A simple theory predicts a near doubling of resolution for illumination with partial incoherence σ < 0.3, and substantial improvements in resolution for σ < 0.7. Initial results obtained with a phase-shifting mask patterned with typical device structures by electron-beam lithography and exposed using a Mann 4800 10× tool reveals a 40-percent increase in usuable resolution with some structures printed at a resolution of 1000 lines/mm. Phase-shifting mask structures can be used to facilitate proximity printing with larger gaps between mask and wafer. Theory indicates that the increase in resolution is accompanied by a minimal decrease in depth of focus. Thus the phase-shifting mask may be the most desirable device for enhancing optical lithography resolution in the VLSI/VHSIC era.

Improving resolution in photolithography with a phase-shifting mask

A lithographic apparatus configured to project a patterned beam of radiation onto a target portion of a substrate is disclosed. The apparatus includes a first radiation dose detector and a second radiation dose detector, each detector comprising a secondary electron emission surface configured to receive a radiation flux and to emit secondary electrons due to the receipt of the radiation flux, the first radiation dose detector located upstream with respect to the second radiation dose detector viewed with respect to a direction of radiation transmission, and a meter, connected to each detector, to detect a current or voltage resulting from the secondary electron emission from the respective electron emission surface.

Lithographic apparatus, and device manufacturing method

An illumination optical apparatus successfully realizes mutually different illumination conditions in orthogonal two directions on an illumination objective plane. A magnification-varying optical system for similarly changing the entire size of a secondary multiple light source is arranged in an optical path between a first optical integrator for forming a first multiple light source on the basis of a light beam from a light source and a second optical integrator for forming the second multiple light source having light sources of a larger number on the basis of a light beam from the first multiple light source. The apparatus further comprises an aspect ratio-changing element for changing the aspect ratio of the incoming light beam in order to change the angle of incidence of the incoming light beam into the first optical integrator in a predetermined direction.

Illumination optical apparatus and exposure apparatus provided with illumination optical apparatus

We present a new type of quadrature phase-shifting interferometer, which utilizes wave plates, a diffraction grating, and two lasers with different wavelengths, in order to acquire two sets of two quadrature fringe patterns in each wavelength formed on a single image sensor. This method for calculating with four phase-shifted fringe patterns gives us the phase sum and difference distributions between the phases in two wavelengths. This is also substantiated by results of our experiments.

Simultaneous formation of four fringes by using a polarization quadrature phase-shifting interferometer with wave plates and a diffraction grating

We present a new type of phase-shifting interferometer, which utilizes a polarizing prism to form quadrature phase-shifted fringe patterns onto a single imaging sensor. By changing the direction of linear polarization of the incident light orthogonally, four phase-shifted fringe patterns in quadrature are obtained by taking images twice; thus it is possible to reduce phase errors caused by mechanical vibrations and air turbulence that occur in temporal phase-shifting interferometers. We present the principle of this interferometer with its theoretical analysis, using the Jones matrix, along with experimental results.

Phase-shifting interferometer based on changing the direction of linear polarization orthogonally.

A novel method for optical lithography using a resist with nonlinear photosensitivity and the multiple exposure technique is described. By means of this method, the diffraction-limited optical cutoff frequency is raised markedly, which cannot be realized by any of the other methods proposed previously. A brief explanation of the principle is given and computer simulations are demonstrated.

A Novel Super-Resolution Technique for Optical Lithography—Nonlinear Multiple Exposure Method

PROBLEM TO BE SOLVED: To provide optical illumination equipment which can realize different lighting conditions in two orthogonal directions on the surface to be irradiated. SOLUTION: In this optical illumination equipment, a variable power optical system (7), which is used for similarly changing the whole size of second multiple light sources, is arranged in the optical path between a first optical integrator (6) which is used for forming first multiple light sources, based on the luminous flux from a light source means (1) and a second integrator (8), which is used for forming the second multiple light sources, the number of which is larger than that of the first multiple light sources, based on the luminous fluxes from the first multiple light sources. This illumination equipment is also provided with an aspect ratio changing element (10), which changes the aspect ratio of the incident luminous flux to the first optical integrator (6) for changing the incident angle of the luminous flux in the prescribed direction.

Masato Shibuya

Papers

Illumination optical apparatus and exposure apparatus provided with illumination optical apparatus

Simultaneous formation of four fringes by using a polarization quadrature phase-shifting interferometer with wave plates and a diffraction grating

Phase-shifting interferometer based on changing the direction of linear polarization orthogonally.

A Novel Super-Resolution Technique for Optical Lithography—Nonlinear Multiple Exposure Method

Optical illumination equipment and aligner equipped with the same