Ar Electron Cyclotron Resonance Plasma Research Articles

ECR-Ectching of Submicron and Nanometer Sized 3C-SiC(100) Mesa Structures

Anisotropic etching processes for mesa structure formation using fluorinated plasma atmospheres in an electron cyclotron resonance (ECR) plasma etcher were studied on Novasic substrates with 10 µm thick 3C-SiC(100) grown on Si(100). To achieve reasonable etching rates, a special gas inlet system suitable for injecting SF6 into the high density downstream Ar ECR plasma was designed. The influence of the etching mask material on the sidewall morphology was investigated. Masking materials with small grain sizes are preferable to achieve a desired shape. The evolution of the mesa form was investigated in dependence on the gas composition, the applied bias, the pressure and the composition of the gas atmosphere. The achieved sidewall slope was 84.5 deg. The aspect ratios of the fabricated structures in the developed residue free ECR plasma etching process were between 5 and 10. Mesa structures aligned to [100] and [110] directions were fabricated.

Roles of Ions and Free Electrons in the Synthesis of Mechanically Hard Amorphous-CNx Films Using a Dissociative Excitation Reaction of BrCN with the Ar Electron Cyclotron Resonance Plasma

A dissociative excitation reaction of BrCN with the Ar electron cyclotron resonance (ECR) plasma was applied to synthesize mechanically hard amorphous carbon nitride (a-CNx) films. The hardness of the films has been measured by a nanoindenter to be at most 15 GPa under the maximum loading force of 50 mN. The self-bias voltage, -Vself, and the I–V characteristics have been measured to discuss the mechanism of hardening of the a-CNx films. It was confirmed that -Vself causes the Ar ion bombardment on the surface of the films, leading to the high hardness value of the films without applying an external bias voltage.

Electron Cyclotron Resonance Plasma Etching of n-SiC and Evaluation of Ni/n-SiC Contacts by Current Noise Measurements

The Si surface of n-SiC is etched by an Ar electron cyclotron resonance plasma in order to smooth the as-received substrates. Low-frequency current noise characteristics of Ohmic contacts of the wide-band-gap semiconductor n-SiC are investigated. Ohmic contacts with a diameter of 200 µm have a minimum Ohmic contact resistance of the order of 10-4 Ω·cm2 at an alloying temperature of 1000°C for 30 min. These low resistance Ohmic contacts show typical 1/f current noise characteristics that increase with the square of the sample current I2. A sample with a higher contact resistance exhibits, however, current noise power increase with increasing sample current I. The relevant total electron number between the electrodes of the bulk substrate is estimated from the resistance and by finite element method simulation, from which the Hooge parameter αH is estimated to be approximately 40.

Cleaning of CHF 3 Plasma‐Etched SiO2/SiN/Cu Via Structures with Dilute Hydrofluoric Acid Solutions

After etching in a /Ar electron cyclotron resonance plasma, /SiN/Cu via structures for multilevel Cu interconnection were investigated with angle‐resolved x‐ray photoelectron spectroscopy. Photoelectron shadowing, determined by x‐ray photoelectron spectroscopy takeoff angle, and electrostatic charging were used to determine the chemical composition and amount of contamination on the dielectric horizontal surfaces and via sidewalls, as well as on the Cu at the bottoms of the via holes. All surfaces were covered with one to two monolayers of a layer . The dielectric surfaces were also covered with a small amount (∼0.1 monolayers) of Cu, and the Cu at the bottom of the via was contaminated with O (mainly CuO) and F. After cleaning with dilute HF solution, the dielectric surfaces were free of Cu and most of the F and C. CuO was also removed from the Cu surface by this treatment; however, and remained.

Electron Cyclotron Resonance Plasma Etching of AlGaN in Cl2/Ar and BCl3/Ar Plasmas

A comparison of etch rates for alloys was performed in /Ar and /Ar electron cyclotron resonance plasmas. The etch rates were generally found to decrease with increasing AlN concentration, due to the increasing average bond strengths at higher Al compositions. The fastest rates were found in the /Ar chemistry, with rates of ∼3500 Å/min for GaN, 1700 Å/min for AlN, 2500 Å/min for , and 3300 Å/min for . The etched surfaces were also smoother with the /Ar plasma chemistry than the /Ar plasma chemistry. The etch selectivities for GaN over , and AlN were quite low, ⩽5 for all conditions, and this is due to the ion‐driven nature of the removal mechanism.

Surface cleaning and etching of CdZnTe and CdTe in H2/Ar, CH4/H2/Ar, and CH4/H2/N2/Ar electron cyclotron resonance plasmas

This paper compares H2/Ar, CH4/H2/Ar, and CH4/H2/N2/Ar plasma etch processes for CdZnTe and CdTe substrates in view of their potential to provide high-quality substrate surfaces for subsequent HgCdTe epitaxy. An electron cyclotron resonance source was used as plasma generator, and ellipsometry, angle-resolved x-ray photoelectron spectroscopy and low energy electron diffraction were applied to characterize roughness, composition, and order of the resulting substrate surfaces. It was found that CdZnTe is much more susceptible to evolving surface roughness under H2/Ar plasma exposure than CdTe. The severe roughening observed at 100°C sample temperature was found to be correlated with a buildup of ZnTe at the surface, which suggests that the roughness formation may result from a preferential etching of the CdTe component. This surface degradation could be reduced by the addition of CH4 to the process gases. However, only a further addition of nitrogen gas balanced and substantially improved the plasma process so that atomically clean, very smooth, and stoichiometrically composed CdZnTe surfaces of long-range order were eventually obtained.

Kinetic-energy measurement of a neutral stream extracted from Ar electron cyclotron resonance plasma

The kinetic energy of a neutral stream within Ar electron cyclotron resonance plasma was evaluated by means of time-of-flight mass spectroscopy. The median energy in the distribution of the neutral stream ranged between 10 and 20 eV for pressure from 1.4 to 2.9×10−4 Torr. This energy is almost equal to that of the ions. The energy of the neutral stream could be controlled by adjusting the gas pressure. A higher pressure broadened the energy distribution of the neutral stream.

A study of silicon epitaxial growth on silicon substrates exposed to Ar electron cyclotron resonance plasmas

Epitaxial growth of Si on Si(100) wafers was carried out at 700 °C in an Ar microwave electron cyclotron resonance plasma chemical vapor deposition system. Both plasma exposure prior to growth and epitaxial growth were monitored by real‐time single‐wavelength ellipsometry, first to determine an optimum end point for Ar plasma cleaning which would favor quality epitaxial growth, and second to follow the growth of the epitaxial film. Spectroscopic ellipsometry combined with cross‐sectional transmission electron microscopy and atomic force microscopy were used to characterize the epitaxial films, the epitaxial film/substrate interface, and the surface morphology. Secondary‐ion mass spectroscopy was used to evaluate the contamination levels at the film/substrate interface. Epitaxial films were successfully grown on both, smooth and rough (20–30 nm roughness layer) Si substrates. For both cases the top surface of the epitaxial film was smooth, but the interfaces were different.

Ellipsometric Monitoring of Defects Induced by Electron Cyclotron Resonance Etching of GaAs

AbstractSpectroscopic ellipsometry (SE) measurements were made during and after electron cyclotron resonance (ECR) etching of GaAs. The spectral range for ex situ measurements, 1.24–5 eV, included the E1, E1+A1 critical points. The Ej, Ei+Aj structure was red shifted by about 50 meV, and broadened, by etching with a mixture of methane, argon, and hydrogen. Exposure to a pure H2 plasma caused greater red shifting and broadening, while a pure Ar ECR plasma produced only a slight red shift. The red shift is consistent with an increase in lattice constant of the order of 1%, in the top 10-30 nm. Broadening is consistent with crystalline lattice damage.

Characterization and stabilization of an electron-cyclotron resonance plasma source using an automatic microwave tuner

An automatic microwave stub tuner (AST) has been developed and used to characterize and stabilize an electron-cyclotron resonance (ECR) plasma source. The tuner provides a new method for measuring plasma impedance dynamically without disturbing the plasma. The Ar ECR plasmas were excited by a 2.45 GHz microwave (<800 W) in the presence of the static axial magnetic fields ranging from 875 to 2000 G, and the characteristics were investigated using a double probe and the AST. Results of these measurements indicated that the Ar ECR plasma had discrete stable modes where the plasma parameters and impedance varied continuously. For certain operating conditions, slight shifts of microwave power and/or magnetic-field strength brought about discontinuous mode transitions. In the transition regions, the drastic changes of plasma characteristics were observed, resulting in the instability of the plasma. It was quite effective for stabilizing the unstable plasmas to control the reflection coefficient of the microwave transmission line.