19 July 1989 Endpoint Detection Of Photoresist Development Using Multiple Wavelengths And Polarized Light
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Abstract
A novel methodology for development endpoint detection is presented which utilizes a polarizing optical head (Tritec Industries) to monitor dissolution of exposed photoresist by interferometry. We have found significant improvement in the interferometric signal modulation when using circularly polarized illumination and detection. This result is attributed to a reduction in ambient light effects and to rejection of depolarized light due to scattering from resist sidewalls, aerosol droplets, suspended particles, and bubbles in the developer. Additional improvement in the interferometric signal modulation has been obtained by monitoring an infrared wavelength at which the developer absorption is minimized. This approach tends to ameliorate the problem of "red cloud" opacity that sometimes plagues single-wavelength laser endpoint detection systems. Interferometric data at 660, 830, and 890nm wavelengths are compared using robust fast Fourier transform and finite difference algorithms.
© (1989) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Kevin M. Monahan, "Endpoint Detection Of Photoresist Development Using Multiple Wavelengths And Polarized Light", Proc. SPIE 1087, Integrated Circuit Metrology, Inspection, and Process Control III, (19 July 1989); doi: 10.1117/12.953104; https://doi.org/10.1117/12.953104
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