In this work, electrical and optical studies of SF 6 and SF 6 /O 2 plasmas generated in a hollow cathode reactive ion etching reactor were performed using the Langmuir probe and optical emission spectroscopy techniques, respectively. We carried out an investigation aimed at understanding the influence of radio-frequency power, gas pressure and O 2 gas mixing ratio on plasma parameters, namely electron temperature, electron density and electronegativity, and also atomic fluorine density. The results indicate an increase of up to one order of magnitude in electron density and atomic fluorine in the overall gas volume when compared with a conventional reactive ion etching plasma generated under the same operation conditions.
In this work the applicability of a low pressure sulphur hexafluoride (SF 6 ) plasma jet for silicon etching was investigated by optical emission spectroscopy (OES) technique. Through the use of actinometry method the density of atomic fluorine was obtained as a function of process parameters namely radiofrequency (rf) power, axial magnetic field, SF 6 gas pressure and flow rate, and O 2 concentration in the SF 6 +O 2 mixture. The results indicate large fluorine concentrations (>10% in overall plasma volume) for the conditions studied. To confirm the applicability of these results for microelectronic material processing, we performed the etching of masked silicon (Si) substrates under some optimum process conditions. Etch rates of up to 1.2 µm/min were obtained for rf power of about 150W and operating pressures about 3.1 mTorr. These values of etching rates are comparable with those obtained in inductively coupled plasma (ICP) systems operating at similar process conditions.
The aim of this work is to study the influence of electronegative gas (oxygen at different concentrations) on the electrical characteristics of two configurations of magnetron sputtering systems, namely Hollow Cathode Magnetron Sputtering (HCMS) and Conventional Magnetron Sputtering (CMS). A comparison of the plasma impedances and magnetron efficiency of these systems were carried out through the current-voltage characteristics of the discharges operating at the same pressure and different oxygen concentration on O2/Ar mixtures. The results showed significant variations in the plasma impedance and magnetron efficiency, indicating that HCMS system presents better electrical characteristics than CMS system, i.e., low plasma impedance and high magnetron efficiency. The results indicate that HCMS system is a very interesting technique to be used as deposition system in micro and nanoelectronic processes.
In this work is proposed the automation of a gas injection (mass flow) system in order to generate timemultiplex SF 6/CH4 radiofrequency plasma applied for silicon (Si) etching process. The control of the gas injection system is important in order to better control the process anisotropy, i.e., the high-aspect-ratio of mask pattern transfer to substrate surface. In other words, this control allows the attainment of deep Si etching process. Here, the automation of the gas injection system was realized through the interface between a computer and a data acquisition board. The automation software developed allows controlling the gas flow rate switching it on and off during whole process through the use of a square waveform routine, intermittent flow, beyond the conventional condition of a fixed value for gas flow rate, continuous flow. In order to investigate the timemultiplex SF6/CH4 plasma etching of Si, the residual gas analysis was performed. The investigations were made keeping the following process parameters: flow of SF6: 10 sccm, flow of CH4: 6 sccm, 100 W rf power, wave period: 20 sec. It were monitored the partial pressure of SF + 5 (parent neutral specie: SF6), CH + 4 (CH4) and SiF + 3 (SiF4) species as a function of time for different gas flow switching and duty cycle. The results showed that with the generation of plasma occurs a drastic change in behavior of partial pressures of SF + 5 and CH + 4 species. Moreover, it is evidenced that the interactions between the SF6 and CH4 fragments promotes a high production rate of HF molecule and consequently a decrease of atomic fluorine, mainly when plasma is on. Finally, the behavior of partial pressure of SiF + 3 specie for alternatively intermittent SF6 and CH4 flow operation shows us that both the etching processes and the deposition of a polymer passivation layer are occurring alternatively, a desirable feature for multi-step etching process.
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