Correlation ofⅢ/Ⅴsemiconductor etch results with physical parameters of high-density reactive plasmas excited by electron cyclotron resonance

Reactive ion etching is the interaction of reactive plasmas with surfaces. To obtain a detailed understanding of this process, significant properties of reactive composite low-pressure plasmas driven by electron cyclotron resonance(ECR) were investigated and compared with the radial uniformity of the etch rate. The determination of the electronic properties of chlorine-and hydrogen-containing plasmas enabled the understanding of the pressure-dependent behavior of the plasma density and provided better insights into the electronic parameters of reactive etch gases. From the electrical evaluation of I(V) characteristics obtained using a Langmuir probe,plasmas of different compositions were investigated. The standard method of Druyvesteyn to derive the electron energy distribution functions by the second derivative of the I(V)characteristics was replaced by a mathematical model which has been evolved to be more robust against noise, mainly, because the first derivative of the I(V) characteristics is used. Special attention was given to the power of the energy dependence in the exponent. In particular, for plasmas that are generated by ECR with EM modes, the existence of Maxwellian distribution functions is not to be taken as a self-evident fact, but the bi-Maxwellian distribution was proven for Ar-and Kr-stabilized plasmas. In addition to the electron temperature, the global uniform discharge model has been shown to be useful for calculating the neutral gas temperature. To what extent the invasive method of using a Langmuir probe could be replaced with the noninvasive optical method of emission spectroscopy, particularly actinometry, was investigated,and the resulting data exhibited the same relative behavior as the Langmuir data. The correlation with etchrate data reveals the large chemical part of the removal process—most striking when the data is compared with etching in pure argon. Although the relative amount of the radial variation of plasma density and etch rate is approximately ?5%, the etch rate shows a slightly concave shape in contrast to the plasma density.

On the heating mechanism of electron cyclotron resonance thruster immerged in a non-uniform magnetic field

To study the heating mechanism of electron cyclotron resonance thruster(ECRT)immersed in a non-uniform magnetic field,experiments and simulations are performed based on an electron cyclotron resonance plasma source at ASIPP.It is found that the first harmonic of electron cyclotron resonance is essential for plasma ignition at high magnetic field(0.0875 T),while the plasma can sustain without the first and second harmonics of electron cyclotron resonance at low magnetic field(till 0.0170 T).Evidence of radial hollow density profile indicates that upper hybrid resonance,which has strong edge heating effect,is the heating mechanism of low-field ECRT.The heating mode transition from electron cyclotron resonance to upper hybrid resonance is also revealed.Interestingly,the evolutions of electron temperature and electron density with input power experience a‘delayed’jump,which may be correlated with the different power levels required for cyclotron and ionization.Moreover,when the field strength decreased,the variation of electron density behaves in an opposite trend with that of electron temperature,implying a possible competition of power deposition between them.The present work is of great interest for understanding the plasma discharge in ECRT especially immersed in a non-uniform magnetic field,and designing efficient ECRT using low magnetic field for economic space applications.

Relative Irradiance Measurement and Bonding Configurations of Amorphous Fluorinated Carbon Films Deposited by Electron Cyclotron Resonance Plasma

a-C:F films are deposited by microwave electron cyclotron resonance (ECR)plasma chemical vapor deposition (CVD) using trifluoromethane (CHF3) and benzene (C6H6) as source gases at different microwave powers. The radicals in plasma originating from source gases dissociation are analyzed by relative irradiance measurement. The bonding configurations and binding state of a-C:F films are measured with Fourier-transformed infrared spectrometer (FTIR) and x-ray photoelectron spectroscopy (XPS). The results show that a-C:F films are mainly composed of CF radical at lower powers but of CF2 radical at higher powers. The deposition of films is related to the radicals generated in plasma and the main bonding configurations are dependent on the ratio of CF to CF2 radicals in films.

Simulation of nonlinear behavior in an electron cyclotron resonance plasma

Some nonlinear behavior in electron cyclotron resonance plasma was investigated using a two-dimension hybrid-mode with self-consistent microwave absorption. The saturation,oscillations of plasma parameters (plasma density, potential, electron temperature) versus operating conditions (pressure, power) are discussed. Our simulation results are consistent qualitatively with many experimental measurements.

Ion heat transport in electron cyclotron resonance heated L-mode plasma on the T-10 tokamak

Anomalous ion heat transport is analyzed in the T-10 tokamak plasma heated with electron cyclotron resonance heating(ECRH) in second-harmonic extra-ordinary mode. Predictive modeling with empirical scaling for Ohmical heat conductivity shows that in ECRH plasmas the calculated ion temperature could be overestimated, so an increase of anomalous ion heat transport is required. To study this effect two scans are presented: over the EC resonance position and over the ECRH power. The EC resonance position varies from the high-field side to the low-field side by variation of the toroidal magnetic field. The scan over the heating power is presented with on-axis and mixed ECRH regimes. Discharges with high anomalous ion heat transport are obtained in all considered regimes. In these discharges the power balance ion heat conductivity exceeds the neoclassical level by up to 10 times. The high ion heat transport regimes are distinguished by three parameters: the ratio Te/Ti, the normalized electron density gradient R/■, and the ion–ion collisionality νii~*. The combination of high Te/Ti, high νii~*, and R/■=6-10 results in values of normalized anomalous ion heat fluxes up to 10 times higher than in the low transport scenario.

The research progress of an E//B neutral particle analyzer

An E//B neutral particle analyzer(NPA)has been designed and is under development at Sichuan University and Southwestern Institute of Physics.The main purpose of the E//B NPA is to measure the distribution function of fast ions in the HL-2A/3 tokamak.The E//B NPA contains three main units,i.e.the stripping unit,the analyzing unit and the detection unit.A gas stripping chamber was adopted as the stripping unit.The results of the simulations and beam tests for the stripping chamber are presented.Parallel electric and magnetic fields provided by a NdFeB permanent magnet and two parallel electric plates were designed and constructed for the analyzing unit.The calibration of the magnetic and electric fields was performed using a 50 kV electron cyclotron resonance ion source(ECRIS)platform.The detection unit consists of 32lutetium-yttrium oxyorthosilicate(LYSO)detector modules arranged in two rows.The response functions ofα,hydrogen ions(H^(+),H_(2)^(+)and H_(3)^(+))andγfor a detector module were measured with^(241)Am,^(137)Cs and^(152)Eu sources together with the 50 kV ECRIS platform.The overall results indicate that the designed E//B NPA device is capable of measuring the intensity of neutral hydrogen and deuteron atoms with energy higher than 20 keV.

Interaction between plasma and electromagnetic field in ion source of 10 cm ECR ion thruster

Through diagnosing the plasma density and calculating the intensity of microwave electric field,four 10 cm electron cyclotron resonance(ECR)ion sources with different magnetic field structures are studied to reveal the inside interaction between the plasma,magnetic field and microwave electric field.From the diagnosing result it can be found that the plasma density distribution is controlled by the plasma generation and electron loss volumes associated with the magnetic field and microwave power level.Based on the cold plasma hypothesis and diagnosing result,the microwave electric field intensity distribution in the plasma is calculated.The result shows that the plasma will significantly change the distribution of the microwave electric field intensity to form a bow shape.From the boundary region of the shape to the center,the electric field intensity varies from higher to lower and the diagnosed density inversely changes.If the bow and its inside lower electric field intensity region are close to the screen grid,the performance of ion beam extracting will be better.The study can provide useful information for the creating of 10 cm ECR ion source and understanding its mechanism.

Frictional behavior of nanostructured carbon films

We propose a new path for preparing nanostructured carbon films(NCFs)by using electron cyclotron resonance(ECR)plasma sputtering with ion-electron hybrid irradiation for controlling the frictional behavior.The frictional behavior of the NCF was measured by using a pin-on-disk tribometer with a nanoprobe displacement sensor,and the transition curves of the friction coefficient and microdisplacement of the NCFs were examined.The friction mechanism was discussed by transmission electron microscopy(TEM)observation on the wear track.From the results,we found a new method to prepare NCFs,which has the potential to achieve low friction at the early stage of sliding contact.In addition,the technology of ECR plasma with ion-electron hybrid irradiation provides a new vision to rebuild a nanostructured surface from an original surface for controlling the frictional behavior.