In the lithography machine, there is a field diaphragm, which is a kind of edge structure. In the process of exposure, it is linearly synchronous movement with the die, so when developing the slit, it is necessary to measure its movement characteristics precisely. A method of velocity measurement based on machine vision is adopted, by detecting edge position in sequential images, and then through the transformation between image coordinate and world coordinate, the object displacement in real space is calculated and finally instantaneous velocity of the object is got. Firstly, through the simulation model in CODE V, correctness of the measurement principle is verified, Next, some error sources that affect the precision of the machine vision measurement system are analyzed, and corresponding solutions are given.
To overcome the accuracy limitation due to the aberration of reference wavefront in the interferometer testing, the point diffraction interferometer (PDI) uses the pinhole to create an ideal diffraction sphere wavefront as the reference wavefront. Because the perfect pinhole is hard to manufacture, then the imperfect pinhole will cause the wavefront errors which will influence the test accuracy. In this paper we use the absolute testing method to test the wave front of the pinhole. Then the testing accuracy of point diffraction interferometer can be improved by subtracting the error of the pinhole. In this paper a Phase-shifting point diffraction interferometer system is designed to testing the pinhole. We use three pinholes to test each other. According the algorithm of the absolute testing method, we can calculate the wavefront error of the pinhole. Then the testing accuracy of point diffraction interferometer can be improved by subtracting the error of the pinhole.
In order to eliminate the measurement errors caused by the instability of laser beams, a real-time compensation algorithms for the random drifts of laser beams based on moving average (MA) correction mechanism was presented. By establishing a correction model with two fast steering mirrors in the beam delivery path and analyzing the pulse to pulse beam fluctuation, a real-time beam drifts correction is implemented based on closed loop feedback control, which especially focuses on reducing the pulse to pulse drifts and ground fluctuations. The simulation results show that this algorithm can control beam drifts effectively. Optimal MA can be reduced to 3n-1/2 times (n--pulse numbers in a window) without the ground vibrations. There are a series of improvements on the moving standard deviation (MSD) as well. MSD get a sudden decline at the window pulse. Meanwhile, the drifts can be restrained while loading the ground vibrations without any big jump, and the dropping amplitude is bigger than without the ground vibration. MSD drop while the whole system is controlled by this compensation method and the results are stable. The key of this compensation method for random drifts of laser beams based on moving average feedback control lies in the appropriate corrections formula. What is more, this algorithm which is practical can achieve high precision control of direction drifts.
Result of the testing contain the reference surface errors and test surface errors in the high-accuracy Phase shifting
interferometer which test the relative phase between the two surface. The test accuracy can be achieved by removing the
error of reference surface. In this case, one of body of so-called absolute testing must be used which can test the
systematic errors, including the reference surface, of the instrument to be used to improve the test accuracy. The
accuracy of the interferometer needs different methods to determine in the high accuracy testing. Even-Odd function
method and rotation shear method is introduced in this paper. We use the Zygo interferometer Verifire Asphere to do the
experiment and analyze the errors caused by data processing and interpolation. The result of the experiment can
determine the accuracy of our arithmetic.
Recently most of modern absolute measurement rotation the flats or spheres in the interferometer. We review traditional
absolute testing of flats methods and emphasize the method of even and odd functions. The rotation of the lens can lead
to some errors such as angle rotation error, center excursion error and other coordinate system motion error. We analyze
the errors by using Zernike polynomial. The flat or sphere can be expressed as Zernike polynomial which can also be
divided into even-odd, odd-even, even-even and odd-odd functions. We can use 36 Zernike polynomials to generate 3
plats A, B, C. Then the six measurements can be generated from the three plats. For the angle rotation error, we can
simulate the angle error distribution and substitute in the systems. According the error distribution we can change the
arithmetic to improve the measurement accuracy. The results of errors analyzed by means of Matlab are shown that we
can change the arithmetic according the coordinate direction motion errors which can be detected to improve the accuracy. The analysis results can also be used in other interferometer systems which have the motion of the coordinate system.
Diffractive optical elements (DOEs) are more flexible and powerful than tradition refractive-reflective optical
elements in correcting chromatic aberration of an optical system. In this paper the principle of correcting
secondary spectrum is described. In order to compare the effect of DOEs on correcting secondary spectrum, we
use CODE V to design a refractive telephoto system with different strategies: (I) All surfaces are spherical; (II)
One surface is diffractive in the system; (III) Two or more surfaces are diffractive (Multi-layer diffractive
system). It is found that multi-layer diffractive elements used in a telephoto system can easily correct
secondary spectrum without high dispersion glasses, such as calcium fluoride, at the same time high diffraction
efficiency and broad spectral bandwidth can be obtained. And the most important of all, the length of the
telephoto system can be shortened by about 30%, and the weight can be greatly cut.
The use of lasers in a projection display enables the creation of vibrant images with extensive color coverage. By
adding a phase modulators in illumination systems and keeping the most part structures of the classic projection,
speckle on the screen and retinas of the observers were restrained. The speckle's form and restraining were
simulated. It was obtained form simulations that the contrasts of residual speckle on screen and on retinas are
0.0107 and 0.0132. The simulation proves that speckle on screen and on retinas can be suppressed by phase
modulation of the illumination light in projection. It also indicated that the numerical aperture of projector affect
the residual speckle on retinas. Experiments of speckle restraining were performed. It confirmed the results of the
simulations.
Optical tunnels are widespread in mircolithographic illumination systems. It reshapes the rays and illuminates masks
with dose-and-directional uniformity. Rays were focused the input end, reflected by the walls of the optical tunnel and
lapped over the output end. According to rays reflecting by walls, optical tunnel was expanded along the reflecting
walls. The approaches of rays' propagation in the optical tunnel were given. It indicates the luminance of the source is
important for the optical tunnel performance; the defect of small inclination between bottom and top walls are
neglectable for the uniformity of the output end. The taper of tunnel leads to the dissimilar of rays NA between output
end and input end. The relation of the NA was given. The indications were confirmed by the simulations. When a
collimated beam was focused on the input end, simulations show that the dropping of nonuniformity was unsmooth as
the optical tunnel length increasing. When the luminance turned to a Gaussian distribution, the uniformity improved
greatly. The uniformity of the output will be insensitivity with a fitting luminance. The nonuniformity would be less
than 0.7% when the radius diminished less than the half. The edges' defect degrade the uniformity greatly both
confirmed by the simulations and experiments. It shows that optical tunnels with sharp edges are excellent optical
integrators with fitting luminance sources.
We present the lithography scheme that use high-numerical-aperture photon sieves array as focusing elements in a
scanning X-ray maskless nanolithography system. The system operating at wavelength of 0.5~2nm synchrotron light
sources radiated, each of a large array of photon sieves focuses incident X-ray into a diffraction-limited on-axis
nanoscale spot on the substrate coated photoresist. The X-ray intensity of each spot is modulated by means of a spatial
light modulator. Patterns of arbitrary geometry are exposed and written in a dot matrix fashion while the substrate on a
stepping stage is precisely driven in two dimensions according to the computer program. The characteristics of
synchrotron radiation light, resolution limits and depth of focus of the lithographic system are discussed. The design and
fabrication of photon sieve are illustrated with a low-numerical-aperture amplitude-photon sieve fabricated on a chrome-coated
quarts plate by means of laser-beam lithographic process, which minimum size of pinhole was 5.6um. The
focusing performance of the photon sieve operating at wavelength of 632.8nm was simulated and tested.
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