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 (T exc ) 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 T exc profiles match well with the shape of the electrode and etch rate profile.

Electron characterization in weakly ionized collisional plasmas: from principles to techniques

“…For quite periodic plasmas during interesting time periods, a rotating plasma source or an imaging device is one straightforward solution for performing tomographic reconstruction or confirming the reconstruction results with a sparser data set. As the demands for characterizing meter-sized plasma increased, Jang et al [191] attempted to apply tomographic optical diagnostics to an 8th generation plasma device (an electrode with a size of 2.6 × 2.2 m 2 ) for the real-time monitoring of the spatial plasma information as detailed in Figure 14.…”

“…The combination of plasma and solid catalyst promises dramatic improvements in catalytic or energy efficiency compared with that of plasma or catalyst alone in relevant engineering. Active attempts to employ plasma-catalysis [191].…”

Sparse data recovery of tomographic diagnostics for ultra-large-area plasmas

“…The inner configuration of the detector assembly and its description can be found in our previous paper [29]. The identical detector assembly reported in [29] was used without the optical interference filters in this work. Each detector unit was aligned according to the same configuration presented in figure 1(b).…”

Reconstruction of plasma density profiles by measuring spectra of radiation emitted from oscillating plasma dipoles

“…Furthermore, quantitative knowledge of the electron density, its fluctuation and profile type is required for developing fusion plasma devices [2][3][4][5][6][7][8][9][10] and for understanding laser-plasma interactions in general [11][12][13][14]. It is also necessary for characterising plasma-related instruments, including those used for material processing [15][16][17][18][19]. Many plasma diagnostics techniques currently exist; their operating principles depend on the plasma parameter regimes.…”

“…However, the technique has limitations: the phase change is integrated along the path, and the local density cannot be determined at specific points along them unless particular symmetries are assumed. Tomographic methods are useful in deducing the density distribution by applying inversion algorithms to significant amount of data from many data acquisition channels, but are not suitable for measuring the local density at desired positions [19]. In contrast, reflectometry is designed to measure the local electron density [6][7][8][9][10] and is often used for fluctuation analysis and edge plasma density probing.…”