Automatic Pinhole-filter Alignment of a Diffraction Phase Microscope for Wafer Defect Inspection Melissa Crawford, Renjie Zhou, and Prof. Lynford Goddard Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign My experiment Introduction Results Replicated part of a defect inspection setup for automatic pinhole alignment experiment Created code using Labview to align the system for “first light” from the pinhole Organized and put together parts for creating interchangeable pinhole holders Aligning the system as new parts are added Semiconductor manufacturers want to be able to detect defects Main methods of defect inspection: Scanning electron microscopy Optical microscopy- favored for inline inspection given it is nondestructive The alignment system works most of the time, but there are still some runs that have to be repeated We are still working on figuring out the best scanning protocol to use Motivation 1 2 3 7 6 5 4 First order The DPM system has to be very precisely aligned: Manual alignment can take from hours to days An automatic system could shorten the time to minutes and allow anyone to align the system Zero order Diffraction Phase Microscopy (DPM) Preliminary results for a one axis test +1 The plot above was generated from a one axis scan. The initial peak is where the zero order beam goes through the filter. The secondary smaller peak only occurs when the first order beam passes through the pinhole. -1 My setup in the lab Diffraction Orders This half of the setup I replicated! Future Work Integrating this alignment system with the entire microscope inspection setup is the next step Ongoing modifications in order to achieve higher success rates in less time Pinhole filter +1 order 0 order 1 Collimator 2 Collimation lens 635 nm laser incident on the wafer surface Reflected beam goes through a diffraction grating, creating multiple beam orders The first order beam is filtered through a 10 µm pinhole, while the zero order passes through unchanged Interferogram is formed on the camera for retrieving the phase and amplitude information from the wafer. Acknowledgments 3 Diffraction grating 4 Fourier lens Thanks go to Renjie Zhou and Prof. Lynford Goddard for their support and guidance throughout this project and also to the Semiconductor Research Corporation (SRC), the PURE committee, and to Rockwell Collins for giving me the chance to work on this project. 5 Pinhole filter 6 Image lens 7 detector