Computerized tomography (CT), in association with optical emission spectroscopy (OES), is used to investigate the three-dimensional image of radio frequency inductively coupled plasma (RF-ICP) in low-pressure hydrogen in E-mode. As a series of CT studies in this paper, we demonstrate a distinct image in H 2 ICP in the E-mode, i.e., the presence of two independent plasmas in a low-pressure region.Index Terms-Computerized tomography, E-mode, hydrogen, inductively coupled plasma, optical emission spectroscopy. I NDUCTIVELY coupled plasmas (ICPs) have been widely used as a high-density plasma source in various applications such as etching, deposition, ashing, surface modification, and mass spectroscopy, etc. ICPs are generally driven by an external current coil which is set at the side wall or top surface of the plasma reactor under a wide range of operating conditions. We have performed systematic studies of the spatiotemporal emission and absorption profile of the ICP by using CT of both the OES and laser absorption spectroscopy (LAS) [1].It is well known that there are two operating modes in ICP. One is a high-density H (inductively coupled) mode sustained by the induced electromagnetic field, and the other is a low-density E (capacitively coupled) mode sustained by the static electric field caused by the local potential difference of the induction coil. The studies of the transition mechanism between the two modes are mostly performed by electrical properties [2]. In the E-mode operated at a low-dissipated power, the electron density is low while the mean energy of electrons with a non-Maxwellian energy distribution is high. In the H-mode, it is exactly the opposite: high power dissipation, operated with a relatively large threshold of the coil current or power. The electron number density in the H-mode is high and the mean energy is lower as compared to those in the E-mode. In addition, in our previous study [4], we visualized that the spatial structure of the E-mode in CF /Ar RF-ICP is quite different from that of the H-mode by using CT-OES. In this paper, we show the presence of two separate plasma region even in a low pressure in H ICP in the E-mode by using CT-OES.Experimental system consists of ICP reactor, photo detector with movable 4-axes robot arm, and wavelength-selectedphoton counting system. The details of the system are described in our previous paper [5]. Plasma is sustained in a quartz cylinder with a diameter of 10 cm and a length of
Highly selective etching of SiO2 over Si is central to the manufacture of ultralarge scale integration devices; the process is generally one of reactive ion etching using polymerizing fluorocarbon chemistry. A number of species including electrons, ions, and radicals are generated by reactions in the gas phase and on the surface in the plasma process. A large number of highly reactive fluorine atoms, fluorocarbon radicals, and ions interact with the substrate and produce etch products. These etch products, primarily SiF4 and SiF2, diffuse back into the bulk plasma where they are dissociated and ionized by interactions with electrons, and the resultant products are transported and redeposited onto the substrate and/or wall surface. That is, the plasma structure may differ depending on whether the Si (or SiO2) surface has been exposed to etching or not. Hence, it is essential to investigate the spatiotemporal characteristics of the plasma structure during etching. In this study, measurements of plasma structure during Si or SiO2 etching in CF4∕Ar radio-frequency inductively coupled plasma (rf-ICP) were performed using computerized tomography of optical emission spectroscopy to investigate plasma-surface interactions. We focused on the characteristics of etch products, their daughter products, and the etchant in the gas phase during Si and SiO2 etching in CF4∕Ar rf-ICP and the disturbance of the plasma structure at high amplitudes of LF bias.
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