Tomography-based spatial uniformity diagnostics for meter-sized plasmas

Abstract

Optical emission spectral tomography diagnostics have been developed to measure the spatial uniformity of meter-sized processing plasmas. The lines of sight and detector location are selected based on tomographic reconstruction tests using synthetic (phantom) images. The developed collection optics system is composed of slits, a plano-convex lens, optical interference filters and photodiode arrays. Using the collection optics, the line-integrated emission intensity is acquired from a meter-sized rectangular argon plasma (inductively coupled plasma at a frequency of 13.56 MHz), which was developed for display panel manufacturing. From the measured intensity, two-dimensional (2D) spatial distributions of argon atomic line intensity (675.3 nm and 852.1 nm) are obtained via the tomographic reconstruction technique based on the Phillips–Tikhonov regularization. In addition, 2D profiles of the electron excitation temperature (Texc) are obtained from those of Ar intensity at the wavelengths 675.3 nm and 852.1 nm via two line method (in essence, a Boltzmann plot). The 2D argon plasma emission and Texc profiles match well with the shape of the electrode and etch rate profile.