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Etching of β-SiC with electron cyclotron resonance (ECR) system was investigated. Anisotropic and smooth etching of SiC was demonstrated with SF6/O2 based discharges. The root-mean-square roughness increases from 35 nm to 56 nm for as deposit and etched sample, respectively. The addition of small amount oxygen enhanced the etch rate of SiC slightly, but further increase of oxygen content reduced the etch rate which resulted from dilution of F ion and free radical densities. NF3/O2 based discharges also showed same trends and produced anisotropicly etching. However, the smoothness is not as good as SF6/O2 based discharges.
A 280 V 6H-SiC thyristor has been fabricated and characterized. The switching characteristics of the SiC thyristor were investigated over a temperature range from 23 °C to 400 °C, with a switched current density of 4900 A/cm2 being observed under pulse bias condition. The thyristor has shown a dV/dt of 400 V/ms. Both the turn-on time and turn-off time increase significantly at 400 °C. The thyristor forward breakover voltage decreases by only 5% when the operating temperature is increased from 23 °C to 400 °C.
In this paper we review and compare most of the published results on dry etching of silicon carbide using various techniques. The vast majority of reports have used RIE methods due to the wide availability of such reactors. Recently, alternative methods of magnetron enhanced RIE (MIE) and electron cyclotron resonance (ECR) plasmas have been demonstrated. MIE has resulted in extremely high etch rates and ECR etching has resulted in smooth, residue-free surfaces with an ability to control the etched profiles.
Electron cyclotron resonance (ECR) plasma etching of single crystal 6H-SiC has been investigated using a CF4/O2 gas mixture and compared to conventional reactive ion etching (RIE) in a radio frequency (13.56 MHz) reactor. The use of ECR results in higher etch rates, lower levels of bias and smoother etched surfaces than rf-RIE. ECR etch rates exceeding 100 nm/min have been obtained at a substrate bias of-100 V. Etch rate and surface morphology have been studied as a function of pressure, bias and power. Auger electron spectroscopy shows that ECR etching leaves no residues unlike rf-RIE which leaves residues containing Al, F, O and C. The current-voltage and capacitance-voltage measurements of Schottky diodes show that there is far less damage induced by ECR etching compared to rf-RIE.
We report on the material properties of SiNx:H films deposited using a 2% SiH4/N2 mixture with additional N2 in an ECR reactor. Deposition rates, refractive index, and stoichiometry have been characterized using ellipsometry, Rutherford backscattering spectroscopy, and infrared spectroscopy. Reactor conditions of 2m Torr total pressure, 650W microwave power, and substrate temperature of 250°C result in high quality, stoichiometric silicon nitride. With a SiH4/N2 ratio = 0.003, hydrogen incorporation is approximately 1.5% and the refractive index is nr =2.0. Lower microwave power and a higher SiH4/N2 ratio result in slightly N-rich films which is attributable to increased H-incorporation. Higher total pressure results in significantly enhanced deposition rates, but with greatly increased H and O content.
Observation of Arsenic antisites (AsGa) in GaAs layers grown by molecular beam epitaxy (MBE) at low substrate temperatures (∼ 200°C) is reported, using electron paramagnetic resonance (EPR), magnetic circular dichroism in absorption (MCDA), and MCDA tagged by optically detected magnetic resonance (MCDA-ODMR). This experiment confirms that there is a MCD absorption band directly associated with AsGa in the GaAs layers. The AsGa concentration in the GaAs layers is found to decrease by about one order of magnitude after annealing at 600°C for two minutes.
This study presents novel methods for chemically preparing back-side and double-side etched, plan-view TEM samples without use of jet thinning instrumentation in order to examine both surfaces and interfaces. Examples are drawn from the semiconductor industry, but this technique can be generalized for use in most materials systems. The methodology for single-sided etching consists of flat lapping and mechanical dimpling followed by material selective chemical etching to electron transparency. Interface defect analysis of heterostructures is achieved via double-sided etching to electron transparency using the proper selective chemical etchants. These techniques are presented not as replacements for conventional cross-sectional preparatory techniques, but instead, as a means for rapid sample preparation for situations where a large number of samples must be analyzed quickly, or in cases where the necessary equipment is lacking for crosssection preparation.
Determining the composition of quaternary epitaxial films requires accurate measurements of both the lattice parameter and the bandgap energy. Complications arise in lattice-mismatched material, because the mismatch produces tetragonal distortion of the epi-layer and splitting of the valence band energies in a manner which depends on the film composition. We present studies on strained InGaAsP grown on (100) InP. Using room temperature photoreflectance (PR) we observe shifting of the band gap and splitting of the valence band energies, and using the (115) and (004) reflections from double crystal x-ray diffraction (DXRD) we determine the values of the parallel and perpendicular lattice constants. By combining the lattice parameter measurements with band splitting data, we accurately determine the quaternary composition from a self-consistent model using an iterative procedure. By linear interpolation of the elastic-stiffness constants, C11 and C12. as well as the shear and hydrostatic deformation potentials for the four binary compounds in the InGaAsP system, we relate the state of biaxial stress to the induced shifts in the valence band energies.
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