Low-temperature oxidation of silicon in microwave oxygen plasma

The growth of silicon dioxide at low temperature in an oxygen plasma is investigated using a simplified electrodeless microwave discharge arrangement. The growth behaviour of the oxide is discussed in terms of plasma parameters. The compositional and electrical characterization of the grown oxide have been made to examine its performance for device applications. The results are compared with earlier observations by other authors.     

Oxidation of GaAs in an oxygen multipole plasma

In a multiple plasma source (which has a hot cathode associated with a magnetic confinement) homogeneous plasmas of satisfactory density ((5–10) × 10¹⁰ cm^-3) can be obtained in large volumes. This source appears to be very convenient for the study of plasma oxidation and has been applied to the case of GaAs.Homogeneous oxides covering a few square centimetres have been obtained with typical growth rates of 200–250 Å min^-1. The electrical properties of metal- oxide-semiconductor structures are controlled by interface states in the whole band gap: in the upper half (near the middle of the gap) densities in the range 10¹³ cm^-2 eV^-1 of rather “slow” interface states (which are unable to follow a 1 MHz signal at room temperature) and in the lower half “faster” interface states are detected from C(V) measurements on n-type and p-type samples.However these interface states do not severely restrict the possibility of fabricating metal-oxide-semiconductor field effect transistors working in the depletion or the enhancement mode.     

Oxygen atom density in capacitively coupled RF oxygen plasma

The density of neutral oxygen atoms was determined in a plasma reactor for surface functionalization of polymer materials. Plasma was created in a stainless steel chamber by capacitively coupled RF generator at 13.56 MHz and adjustable forward power up to 100 W. Measurements were performed with a classical nickel catalytic probe. Systematic measurements were performed at a constant pumping speed, different flow rates from 15 to 100 sccm corresponding to pressures between 30 and 110 Pa, different powers between 40 and 100 W and different probe positions in the discharge chamber. The results showed that the O atom density did not depend much on probe position as long as it was between the powered electrode and grounded housing facing the electrode. The O density depended rather linearly with power at fixed pressure. At low power, the O density did not depend much on pressure, but at high power, it was increasing with increasing pressure. The O density was of the order of 10¹⁹ m⁻³ and increased slightly over 10²⁰ m⁻³ at the highest power and pressure. The results were explained by gas phase and surface reactions.     

Oxidation of silicon by oxygen: a rate equation

A new rate equation fits data on the oxidation of silicon by oxygen. It can be derived from a model of molecular diffusion in the oxide layer and the influence of strain on this diffusion.[/p]     

Laser induced plasma in the formation of surface-microstructured silicon

The plasma induced by femtosecond laser pulses irradiated on silicon surface has been investigated by optical emission spectroscopy. The plasma emission spectra show strong dependence on the structuring ambient gas species and pressure. Among the four ambient gases (SF₆, N₂, air and vacuum), the plasma obtained in sulfur hexafluoride (SF₆) shows the strongest signals. The emission intensities increase initially with the gas pressure, and achieve strongest at the pressure of about 70 kPa, then decrease as the pressure further increases. The stronger plasma emission signals indicate stronger reactions, resulting in sharper sample morphology, which provides an insight into the reaction process.     

Inductively coupled RF oxygen plasma characterization by optical emission spectroscopy

Optical emission spectroscopy was applied for the characterization of inductively coupled RF oxygen plasma at pressures between 10 and 300 Pa. The plasma was generated with an RF generator at a frequency of 27.12 MHz and output power of 300 W. Spectra were measured in the range 200-1100 nm by an optical spectrometer. At high pressure, the main spectral features observed were the wavelengths of the atomic oxygen transitions at 777.2 and 844.6 nm. Molecular oxygen band at 762 nm was observed as well. The atomic emission intensity showed a maximum when the pressure was about 75 Pa, while molecular band intensity increased monotonically as the total pressure increased. On decreasing the oxygen pressure, other atomic and molecular features appeared in spectra, such as H atomic lines, molecular OH band, and O₂⁺ band. The behavior of spectral features was explained by collision phenomena in the ionized gas.     

Active species characterization in RF remote oxygen plasma using actinometry OES and electrical probes

Actinometry optical emission spectroscopy (AOES), single cylindrical Langmuir probe and electrostatic planar probe were used to investigate the active species (electrons, ions and atomic oxygen) of remote oxygen plasma in an RF (13.56 MHz) hollow cathode discharge system, as a function of applied power and gas pressure. The electron density and electron temperature were determined from Langmuir probe. The atomic oxygen (AO) density was measured using argon actinometry method. Positive ion flux rate was estimated from the positive ion saturation current of the planar probe, and the combination of the planar and Langmuir probes enabled the determination of the negative ion fraction in the discharge. The explanation of the behavior of the different active plasma species was performed on the basis of the main kinetic reactions of oxygen plasma.     

Oxidation of sintered silicon nitride

The influence of oxidation at 1200 °C in air for up to 1000 h on the mechanical properties of two Si₃N₄-Y₂O₃-Al₂O₃ materials with different Y₂O₃/Al₂O₃ ratios, Material A (Si₃N₄-13.9 wt% Y₂O₃-4.5 wt% Al₂O₃) and Material B (Si₃N₄-6.0 wt% Y₂O₃-12.4 wt% Al₂O₃), was investigated. The oxidation significantly improves the high-temperature strength and fracture toughness of both materials, but more for Material A. After oxidation, Material A at 1300 °C retains 93% of its room-temperature strength and 87% higher than that before the oxidation. The oxidation has a different effect on the room-temperature K _IC for the two materials. The room-temperature Weibull modulus of Material A decreased by more than half while the 1200 °C Weibull modulus decreased slightly after oxidation. The annealing treatment prior to oxidation had no effect on the high-temperature strengths of the materials after oxidation. The effect of oxidation on mechanical properties is discussed in terms of the microstructure change of the materials.     

高频放电等离子体引发碳化硅表面接枝聚合甲基丙烯酸甲酯

高频放电氮气等离子体表面处理纳米碳化硅粉体,进而在碳化硅表面上引发甲基丙烯酸甲酯单体接枝聚合,在纳米碳化硅表面形成一层保护膜.红外(FTIR),X射线光电子能谱(XPS)以及热失重分析(TGA)测试表明该聚合膜是通过化学键连接在碳化硅表面的,X射线衍射光谱(XRD)表明经等离子体处理改性的碳化硅粉体只是其表面性质发生了改变,其晶体结构并没有发生任何变化.     

Effect of oxygen plasma treatment on low dielectric constant carbon-doped silicon oxide thin films

Low dielectric constant (low k) carbon-doped silicon oxide (CDO) films are obtained by plasma-enhanced chemical vapor deposition. The k value of the as-deposited CDO film is less than 2.9. However, the k value may be changed during the integration process. In integration process, photoresist removal is commonly implemented with oxygen plasma ashing or by wet chemical stripping. In this work, the impact of oxygen plasma treatment has been investigated on the quality of the low-k CDO films. Different plasma treatment conditions, including variable pressure, r.f. power, and treatment time were employed. A variety of techniques, including X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, time-of-flight secondary ion mass spectrometry (TOF-SIMS), atomic force microscopy (AFM), and scanning electron microscope (SEM) were used to analyze the effect of the oxygen plasma post-treatment on the low-k CDO films. The result indicates that oxygen plasma will damage the CDO film by removing the entire carbon content in the upper part of the film with increasing treatment time, which results in an increase in the k value and film thickness loss. Our result also confirms that with low r.f. power and low pressure, the damage will be less.     

Oxidation kinetics of hot-pressed silicon carbide

The oxidation of silicon carbide, hot-pressed with 4 wt % Al₂O₃, in 1 atm dry oxygen follows classical parabolic behaviour with an activation energy of 481 kJ mol^–1 in the temperature range 1200 to 1400° C. The oxide film consists predominantly of cristobalite and a glassy phase in which additive (Al) and various impurity elements (Fe, Na, K, etc) concentrate. The desorption of CO(g) from the SiC/SiO₂ interface appears to be oxidation rate controlling.     

Oxidation mechanism of porous silicon nitride

The oxidation of reaction-bonded silicon nitride (RBSN) has been studied in air between 800 and 1500° C. The extent of internal oxidation is governed by the radius of the pore channels allowing the oxygen to penetrate the specimen. The velocity of oxygen transport into narrow channels is very low compared to the reaction rate of oxygen with Si₃N₄. Because of these two concurrent processes an oxygen gradient is built up along the channel axis leading to SiO₂ formation mainly at the channel mouth. The typical oxidation isotherm of RBSN is represented by an asymptotic law. The mass gain and the penetration depth of oxidation is calculated, based on reaction-rates of Si₃N₄-powder, oxygen-diffusion-data and the pore-characteristics of the RBSN-materials, and compared with the experimental results. The results clearly indicate, that high quality RBSN may wel be used in oxidizing atmosphere without extensive internal oxidation.     

Oxidation kinetics of reaction-sintered silicon carbide

The oxidation kinetics of reaction-sintered silicon carbide has been studied over the temperature range 1200° to 1350°C. The material has a bulk density of 3·00 g/cm³ and the unreacted Si content is 22·5% (v/v). The activation energy for oxidation is 28·75 ± 2·61 kcal/mol. It is proposed that the diffusion of oxygen through the growing oxide film is the rate-controlling process.     

Oxidation stacking faults in epitaxial silicon crystals

Oxidation stacking faults (SFs) in epitaxial silicon crystals have been studied by means of preferential etch and X-ray topography. SFs lie on {111} planes and are surrounded by a partial Frank dislocation. Nucleation takes place at crystallographic defects located near the surface of epitaxial layers. These defects appear as etch hillocks after preferential etch. SF length as a function of temperature and time for different thermal treatments is reported. The SF length is controlled by an activation energy of 2.6 eV. This energy, which is nearly half the self diffusion activation energy of silicon, supports a SF growth mechanism controlled by vacancy emission.     

Oxidation of silicon nitride in a wet atmosphere

The effect of water vapour on oxidation was studied with hot-pressed silicon nitride containing both yttria and alumina as sintering aids in wet air flow with 10, 20, 30, and 40 vol% H₂O at 1300°C for 100 h. The oxidation kinetics were determined in a wet air flow with 20 vol% H₂O and in a dry air flow at 1300°C for oxidation times up to 360 h. The water vapour in the atmosphere slightly influenced the oxidation and accelerated the reaction, and the weight gained on oxidation in a wet atmosphere had an increasing tendency with increasing water vapour content. The oxidation proceeded in a diffusion-controlled manner in both wet and dry atmospheres. The values of weight gained in wet oxidation varied to a greater degree than in dry oxidation. Water vapour had a strong effect on the devitrification of the amorphous oxide. This process was presumed to promote the rate of oxidation more than in dry atmosphere. The water vapour also had a strong roughening effect on the surface oxide layer grown during oxidation. The flexural strength at room temperature was degraded by oxidation in a wet atmosphere and it is presumed to be degraded by wet oxidation slightly and consecutively with time.     

Oxidation of silicon carbide in a wet atmosphere

The effects of water vapour on oxidation of pressureless-sintered silicon carbide containing alumina as a densifying aid were studied in a wet air flow with 10, 20, 30 and 40vol% H₂O at 1300° C for 100h. The oxidation kinetics were determined in a wet air flow with 20 vol % H₂O and in a dry air flow at 1300° C for times up to 360 h. The weight gain on oxidation showed an increasing tendency with increasing water vapour content. Water vapour in the atmosphere strongly influenced oxidation and accelerated the reaction. Oxidation in a wet atmosphere proceeded in a diffusion-controlled manner, in the same process as that for the dry atmosphere. No remarkable differences were noticed in the microstructure of the oxide layer and the surface roughness between the samples oxidized under the four wet conditions, but the surface roughness increased with increasing oxidation time. Water vapour evidently accelerated the devitrification of amorphous silica and promoted oxidation. Oxidation in a wet atmosphere (10 to 40 vol % H₂O for 100 h and 20 vol % H₂O up to 360 h) had a slight degrading effect on the flexural strength. The microstructure or surface roughness of the oxide layer formed during oxidation presumably had very little effect on the room-temperature strength.