Integral Field Spectropolarimetry (IFS) makes feasible the simultaneous measurement of a 2D field with the use of an Integral Field Unit (IFU). Slicer-based IFUs rearrange an input 2D Field of View (FoV) to an output long-slit that is used to feed a standard spectrograph. The spatial resolution reachable with this technique is determined by the slicer width. As a technology demonstrator for a future EST instrument development, here we describe an IFU for the GREGOR solar telescope. It is an evolution from the first IFU installed at GREGOR with 100 μm width slicer mirror. A novel technique was applied to produce a 35 μm-width metallic image slicer, which has been manufactured in collaboration with NAOJ and Canon Inc. for the SOLARNET project. The IFU transforms an input FoV of 4.4” x 2.1” into 16 mini-slits rearranged in two parallel output long-slits to feed the GRIS infrared spectrograph for simultaneous 2D field spectropolarimetric measurements in several wavelengths. A collimator and camera mirror concept was applied to control the pupil and stray light contamination, leading to a telecentric configuration with a 1:1 magnification. Because of the thin dimensions of the slicer mirrors, diffraction effects are not negligible. An study on the impact of the diffraction effects on the whole IFU and the spectrograph, has been carried out. Another important issue that has been taken into account in the design is the individual mini-slit tilt induced by the compact multi-mirror design. Different solutions were considered and the final design is presented.
Wave Front Phase Imaging (WFPI), a new wafer geometry technique, is presented, that acquires 7.65 million data points in 5 seconds on a full 300mm wafer providing lateral resolution of 96µm. The system has high repeatability with root-mean-square (RMS) standard deviation (σRMS) in the single digit nm for the global wafer geometry and in the sub ångström (Å = 10-10 m) range for the full-wafer nanotopography for both 200mm and 300mm blank silicon wafer. WFPI can collect data on the entire wafer to within a single pixel, in our case 96µm, away from the wafer edge roll off. The flatness of the silicon wafers used to manufacture integrated circuits (IC) is controlled to tight tolerances to help ensure that the full wafer is sufficiently flat for lithographic processing. Advanced lithographic patterning processes require a detailed map of the wafer shape to avoid overlay errors caused by depth-of-focus issues. We present WFPI as a new technique with high resolution and high data count acquired at very high speed.
Wave Front Phase Imaging (WFPI) is used to measure the stria on an artificial, transparent plate made of Schott N-BK7® glass material by accurately measuring the Optical Path Difference (OPD) map. WFPI is a new technique capable of reconstructing an accurate high resolution wave front phase map by capturing two intensity images at different propagation distances. An incoherent light source generated by a light emitting diode (LED) is collimated and transmitted through the sample. The resultant light beam carries the wave front information regarding the refraction index changes inside the sample1. Using this information, WFPI solves the Transport Intensity Equation (TIE) to obtain the wave front phase map. Topography of reflective surfaces can also be studied with a different arrangement where the collimated light beam is reflected and carrying the wave front phase, which again is proportional to the surface topography. Three Schott N-BK7® glass block samples were measured, each marked in which location the wave front phase measurement will be performed2. Although WFPI output is an OPD map, knowing the value of refractive index of the material at the wavelength used in the measurements will lead to also knowing the thickness variations of the plate.
The flatness of the silicon wafers used to manufacture integrated circuits (IC) is controlled to tight tolerances to help ensure that the full wafer is sufficiently flat for lithographic processing. Advanced lithographic patterning processes require a detailed map of the wafer shape to avoid overlay errors caused by depth-of-focus issues. A large variety of new materials are being introduced in Back-End of Lines (BEOL) to ensure innovative architecture for new applications. The standard in-line control plan for the BEOL layer deposition steps is based on film thickness and global stress measurements which can be performed on blanket wafers to check the process equipment performance. However, the challenge remains to ensure high performance metrology control for process equipment during high volume manufacturing. With the product tolerance getting tighter and tighter and architecture more and more complex, there is an increasing demand for knowledge of the wafer shape. In this paper we present Wave Front Phase Imaging (WFPI), a new wafer geometry technique, where 7.65 million data points were acquired in 5 seconds on a full 300mm wafer enabling a lateral resolution of 96μm.
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