Opto-Curling Probe for Simultaneous Monitoring of Optical Emission and Electron Density in Reactive Plasmas

Abstract

An advanced robust probe called opto-curling probe (OCP) is presented, which enables the simultaneous monitoring of electron density and optical emission of reactive plasma. The electron density is obtained from the microwave resonance frequency of a small antenna set on the probe surface while the optical emission spectra are observed through an optical fiber tip located at the probe surface. The ratio of the measured optical emission intensity to the electron density readily provides the radical density without relying on actinometry. The usefulness of OCP was experimentally demonstrated in the oxygen plasma cleaning of a carbonized wall with endpoint detection.

Real-time curling probe monitoring of dielectric layer deposited on plasma chamber wall

“…On the other hand, an example of in situ monitoring of etching=cleaning process is end point detection based on optical emission. 3,4) A real-time on-wafer monitoring of deposition process has been performed with use of infrared reflection-absorption spectroscopy (IRRAS) 5,6) and attenuated total internal reflection (ATR). 7) However, there has been lacking a direct real-time monitoring of the thickness of films deposited on a wall surface of plasma chamber.…”

“…Conversely, a microwave resonator probe called a curling probe (CP) has been developed for measuring the electron density in reactive plasmas. 4,[8][9][10][11][12][13][14][15][16][17][18] Unlike the previous microwave resonator probe using a U-shaped wire antenna, [19][20][21][22] the CP adopts a spiral slot antenna of length L, as shown in Fig. 1(a).…”

Generation of slowly rotating microwave plasma by amplitude-modulated resonant cavity

“…These plasma images are useful in monitoring the two-dimensional (2D) uniformity of the plasma near the quartz plate. To measure the spaceand time-resolved values of electron density, a curling probe [30][31][32] of 15 mm in diameter is radially inserted at the distance ζ = 5 cm from the quartz plate surface. The curling probe enables us to accurately measure an absolute electron density from an up-shift in microwave resonance frequency of a spiral antenna using a network analyzer.…”

Recent innovations in microwave probes for reactive plasma diagnostics

“…2(c) was modified to a spiral shape on a flat pane and called a curling probe (CP). 11) Furthermore, the CP was extended to an opto-curling probe (O-CP), 12) which enables simultaneous monitoring of the local densities of both radical species and electron density.…”