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Optically monitoring and controlling nanoscale topography during semiconductor etching

2012; Springer Nature; Volume: 1; Issue: 9 Linguagem: Inglês

10.1038/lsa.2012.30

2095-5545

Chris Edwards, Amir Arbabi, Gabriel Popescu, Lynford L. Goddard,

Optical Coatings and Gratings

We present epi-diffraction phase microscopy (epi-DPM) as a non-destructive optical method for monitoring semiconductor fabrication processes in real time and with nanometer level sensitivity. The method uses a compact Mach–Zehnder interferometer to recover quantitative amplitude and phase maps of the field reflected by the sample. The low temporal noise of 0.6 nm per pixel at 8.93 frames per second enabled us to collect a three-dimensional movie showing the dynamics of wet etching and thereby accurately quantify non-uniformities in the etch rate both across the sample and over time. By displaying a gray-scale digital image on the sample with a computer projector, we performed photochemical etching to define arrays of microlenses while simultaneously monitoring their etch profiles with epi-DPM. Semiconductor etching can now be monitored in real time at nanoscale resolution using a non-destructive optical imaging technique that combines a conventional microscope with a compact Mach–Zehnder interferometer. Developed by Chris Edwards, Amir Arbabi, Gabriel Popescu, and Lynford Goddard at the University of Illinois at Urbana-Champaign in the United States, epi-diffraction phase microscopy makes it possible to collect three-dimensional videos of semiconductor fabrication processes using a CCD camera. The approach is able to measure etch rates at each location across the sample with a resolution of 0.085 nm s−1 per pixel. Such an in situ monitoring capability could be useful for improving the manufacturing quality of a wide variety of semiconductor devices.