Topic
Point diffraction interferometer
About: Point diffraction interferometer is a research topic. Over the lifetime, 346 publications have been published within this topic receiving 3545 citations.
Papers published on a yearly basis
Papers
TL;DR: A novel interferometer design suitable for highly accurate measurement of wave-front aberrations over a wide range of wavelengths, from visible to x ray is described, applicable to at-wavelength testing of many optical systems, including short-wa wavelength projection lithography optics.
Abstract: Disclosed is a point diffraction interferometer for evaluating the quality of a test optic. In operation, the point diffraction interferometer includes a source of radiation, the test optic, a beam divider, a reference wave pinhole located at an image plane downstream from the test optic, and a detector for detecting an interference pattern produced between a reference wave emitted by the pinhole and a test wave emitted from the test optic. The beam divider produces separate reference and test beams which focus at different laterally separated positions on the image plane. The reference wave pinhole is placed at a region of high intensity (e.g., the focal point) for the reference beam. This allows reference wave to be produced at a relatively high intensity. Also, the beam divider may include elements for phase shifting one or both of the reference and test beams.
254 citations
TL;DR: In this article, the authors describe various LSI implementations and demonstrate the use of a cross-grating, carrier-frequency configuration to characterize a large-field 4×-reduction EUV lithography optic.
Abstract: The phase-shifting point diffraction interferometer (PS/PDI) has recently been developed to address the problem of at-wavelength metrology of extreme ultraviolet (EUV) optical systems. Although extremely accurate, the fact that the PS/PDI is limited to use with coherent EUV sources, such as undulator radiation, is a drawback for its widespread use. An alternative to the PS/PDI, with relaxed coherence requirements, is lateral shearing interferometry (LSI). Here we describe various LSI implementations and demonstrate the use of a cross-grating, carrier-frequency configuration to characterize a large-field 4×-reduction EUV lithography optic. The results obtained are directly compared with PS/PDI measurements.
85 citations
TL;DR: In this paper, a point diffraction interferometer (PDI) for extreme ultraviolet lithography (EUVL) aspheric mirror measurement has been developed and the optimal pinhole diameter has been determined as 0.5 μm.
Abstract: A point diffraction interferometer (PDI) for extreme ultraviolet lithography (EUVL) aspheric mirror measurement has been developed. In order to realize an accuracy of 0.1 nm rms, various optical error factors have been numerically analyzed and the maximum tolerable error has been determined. From the error estimation results, the optimal pinhole diameter has been determined as 0.5 μm. In a PDI, air turbulence reduces the precision and accuracy because of the long optical path. In order to avoid this problem, the apparatus is filled with helium gas, which has a smaller refractive index than that of air. By using this apparatus, precision of 0.03–0.04 nm rms and a system error of 0.10 (0.16) nm rms have been obtained for a spheric mirror with numerical aperture (NA) 0.08 (0.15). In aspheric mirror measurement, an accuracy of 0.74 (1.18) nm rms for NA 0.08 (0.15) has been obtained. The accuracy becomes 0.34 (0.97) nm rms for NA 0.08 (0.15) with 36-term Zernike polynomial fitting.
79 citations
Journal Article•
78 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 7 |
| 2020 | 11 |
| 2019 | 7 |
| 2018 | 11 |
| 2017 | 18 |
| 2016 | 16 |