Electron Cyclotron Resonance Plasma Generation Research Articles

Influence of microwave driver coupling design on plasma density at Testbench for Ion sources Plasma Studies, a 2.45 GHz Electron Cyclotron Resonance Plasma Reactor

A comparative study of two microwave driver systems (preliminary and optimized) for a 2.45 GHz hydrogen Electron Cyclotron Resonance plasma generator has been conducted. The influence on plasma behavior and parameters of stationary electric field distribution in vacuum, i.e., just before breakdown, along all the microwave excitation system is analyzed. 3D simulations of resonant stationary electric field distributions, 2D simulations of external magnetic field mapping, experimental measurements of incoming and reflected power, and electron temperature and density along the plasma chamber axis have been carried out. By using these tools, an optimized set of plasma chamber and microwave coupler has been designed paying special attention to the optimization of stationary electric field value in the center of the plasma chamber. This system shows a strong stability on plasma behavior allowing a wider range of operational parameters and even sustaining low density plasma formation without external magnetic field. In addition, the optimized system shows the capability to produce values of plasma density four times higher than the preliminary as a consequence of a deeper penetration of the magnetic resonance surface in relative high electric field zone by keeping plasma stability. The increment of the amount of resonance surface embedded in the plasma under high electric field is suggested as a key factor.

Temperature and density evolution during decay in a 2.45 GHz hydrogen electron cyclotron resonance plasma: Off-resonant and resonant cases

Time resolved electron temperature and density measurements during the decay stage in a hydrogen electron cyclotron resonance (ECR) plasma are presented for a resonance and off-resonance magnetic field configurations. The measurements are conducted on a ECR plasma generator excited at 2.45 GHz denominated test-bench for ion-sources plasma studies at ESS Bilbao. The plasma parameters evolution is studied by Langmuir probe diagnostic with synchronized sample technique developed for repetitive pulsed plasmas with a temporal resolution of 200 ns in typical decay processes of about 40 μs. An afterglow transient is clearly observed in the reflected microwave power signal from the plasma. Simultaneously, the electron temperature evolution shows rebounding peaks that may be related to the interplay between density drop and microwave coupling with deep impact on the Electron Energy Distribution Function. The correlation of such structures with the plasma absorbed power and the coupling quality is also reported.

Development of an H− ion source based on the electron cyclotron resonance plasma generator at CEA/Saclay

Electron cyclotron resonance (ECR) plasma generators have demonstrated their efficiency, reproducibility, and long lifetime for the production of light positive ions like protons or deuterons. These sources generally work in cw mode. A 2.45 GHz ECR test stand based on a pure volume H− ion production is currently under development. This negative ion source is working in pulsed mode, 1 ms at 10 Hz. The first H− ions have been observed at the beginning of 2002 with a poor efficiency. Only a few μA were produced. To avoid negative ions destruction by a nonabsorbed microwave close to the extraction aperture, a stainless steel grid was installed in the rectangular plasma chamber. As a result, the chamber is now effectively separated into two zones: the ECR plasma generator and the H− production zone. By plotting the extracted current versus the production zone length, the H− ion intensity reached more than 100 μA with the grid located 25 mm from the aperture. A voltage difference on the order of 10 V can be applied between the two parts of the plasma chamber in order to modify the electron energy entering the production zone.

Formation of high-quality silicon dioxide films by electron cyclotron resonance plasma oxidation and plasma-enhanced chemical vapour deposition

High-quality silicon dioxide films have been deposited by plasma-enhanced chemical vapour deposition and plasma oxidation using a single magnet electron cyclotron resonance plasma generator with both oxygen and nitrous oxide as the oxygen source, Langmuir probe measurements were used to characterise both molecular oxygen and nitrous oxide discharges. Low electron temperatures, resulting in low sheath potential drops, coupled with the shape of the field lines results in low sputtering from the chamber walls between the source region and substrate. The resulting buildup of an insulating layer of oxide on the chamber walls results in a very clean process. In situ thermal desorption and ellipsometry measurements coupled with X-ray photoelectron spectroscopy have allowed us to characterise the quality of the silicon surface prior to deposition and just after initiation of the plasma. Plasma oxidation dominates over chemical vapour deposition during the early stages of oxide film growth using either oxygen or nitrous oxide as the oxygen source gas. Extensive ex-situ spectroscopic ellipsometry (SE) indicates that the bulk properties of the films arc comparable to those of high-temperature thermal oxides. There is no interface layer measurable by SE for any of the films produced by plasma oxidation or chemical vapour deposition with silane using either molecular oxygen or nitrous oxide as the oxygen source gas even though the latter results in approximately a monolayer of nitrogen at the Si/SiO 2 interface. Chemical analysis by the total reflected X-ray fluorescence technique and by vapour-phase deposition coupled with graphite furnace atomic absorption spectroscopy found no impurities in the films made with silane and molecular oxygen. The high quality of the Si/SiO 2 interface made with these two gases was confirmed by capacitance-voltage measurements on Al-gate capacitors. After a 1 min anneal at 950°C interface state densities below 3×10 10 eV −1 cm −2 were obtained.

Sheet-shaped ECR plasma generation using permanent magnets for material processing

A 30 cm-class long electron cyclotron resonance (ECR) plasma source using slot antennas on a rectangular waveguide was developed for large-area processing. Microwaves of 2.45 GHz were radiated efficiently from the slot antennas into a discharge chamber. The plasma source was generated for Ar, O 2 and N 2 at pressures of 0.01–0.2 Pa. The plasma parameters were measured, and the current entering a target located downstream of the plasma source was also measured for sputtering deposition process. The ECR plasma source achieved the production of uniform Ar plasmas above 0.059 Pa. The Ar plasma uniformity was 10% in a 200 mm length at 437 W and 0.094 Pa. The Ar plasma density was beyond the cutoff density, although the plasma densities for O 2 and N 2 were below it. The target current reached about 150 mA for Ar.

Large volume electron cyclotron resonance plasma generation by use of the slotted antenna microwave source

A new electron cyclotron resonance plasma source, the slotted antenna (SLAN) is presented. The microwave power is coupled to the plasma inside a quartz bell jar by ten equally spaced slot antennae positioned equidistantly around the inside wall of a cylindrical ring cavity. A total of 10 SmCo magnet stacks are positioned between each two slots yielding the required 87.5 mT magnetic field strength for electron cyclotron resonance inside the plasma excitation volume. The source plasma ignition/extinction performance and operational range for different atomic (Ar, He) and molecular gases (O2, N2) were studied in detail. Due to the external magnetic field either in toroidal or hybrid symmetry, a shift of the minimum ignition pressure from 0.4 to 2×10−3 mbar and the minimum extinction pressure from 4×10−3 to 2×10−4 mbar for argon was observed. The radial and downstream ion density as well as electron temperature were measured by double-Langmuir-probe techniques. Microwave power coupled to the source was varied from 600 to 2000 W and pressure was ranged from 2×10−4 to 10−2 mbar. Typical data achieved for 1000 W microwave power are ion density 2.8×1011 cm−3 at a pressure of 5×10−3 mbar, corresponding to an ionization ratio of 1.3% (center of SLAN).

Optimally Stable Electron Cyclotron Resonance Plasma Generation and Essential Points for Compact Plasma Source

This study examines the strong dependence of electron cyclotron resonance (ECR) plasma generation on the microwave conditions and the magnetic field profiles in the ECR plasma. When an introduced microwave frequency oscillates and has a large ripple, the ECR plasma around the ECR region vibrates and regularly turns on and off. The microwave oscillation and the microwave ripple must be eliminated to prevent poor etching anisotropy. Moreover, the nonuniform plasma causes disturbed ion motions due to magnetohydrodynamic (MHD) plasma instability. It is found that uniform and high-density ECR plasma is generated by optimizing the waveguide, the location of the ECR region and the magnetic field profiles for precise ULSI patterning. Based on these results, we determine the essential features for realizing a compact ECR plasma source.

400 kHz radio-frequency biased electron cyclotron resonance plasma etching for Al–Si–Cu patterning

A radio-frequency (rf) biased electron cyclotron resonance (ECR) plasma etching technology with efficient ion acceleration in high density and uniform ECR plasma for accurate Al–Si–Cu alloy film etching has been developed. Substrate is located at the ECR position (875 G position) and etching is carried out with 400 kHz rf bias power. This technology achieves high etching rate (more than 5000 Å/min), excellent uniformity (±5%), highly anisotropic and Cu residue-free etching using only Cl2 and Cl2/BCl3 gas plasma at a low 100 °C substrate temperature. These characteristics are achieved by the combination of dense and uniform ECR plasma generation and efficient accelerated ion flux at the ECR position by using 400 kHz rf bias.

Low radio frequency biased electron cyclotron resonance plasma etching

A radio frequency (rf) biased electron cyclotron resonance (ECR) plasma etching technology has been developed to realize an efficient ion acceleration in high density and uniform ECR plasma for accurate Al-Si-Cu alloy film etching. In this technology, the substrate is located at the ECR position (875 G position) and the etching is carried out with a 400 kHz rf bias power. This Al-Si-Cu etching technology achieves a high etching rate (more than 5000 A/min), excellent etching uniformity (within ±5%), highly anisotropic etching, and Cu residue-free etching in only Cl2 gas plasma. These etching characteristics are accomplished by the combination of the dense and uniform ECR plasma generation at the ECR position with the efficient accelerated ion flux at the ECR position by using 400 kHz rf bias.