Silicon Carbide Epitaxial Growth Research Articles

Microscopic mechanisms of nitrogen doping in silicon carbide during epitaxial growth

We report first-principles calculations that unveil elementary processes of nitrogen donor doping during epitaxial growth of silicon carbide (SiC). We find that a N2 molecule adsorbed on the terrace migrates to a particular step edge where under-coordinated Si atoms appear, or is directly adsorbed near the step edge, and then dissociated there via the step-molecule interaction. This results in the N atom being eventually incorporated at the C substitutional site of the step. The calculated energy barriers indicate that the N incorporation reactions at the step edges occur at a typically high temperature in SiC epitaxial growth.

Chemical Behavior of Byproduct Layer in Exhaust Tube Formed by Silicon Carbide Epitaxial Growth in a System Using Chlorides

This study evaluated the chemical behavior of an oily byproduct which was formed in the exhaust tube during the silicon carbide epitaxial growth process using various precursors, such as silanes, chlorosilanes, propane, hydrogen chloride and hydrogen. Most of the precursors were spontaneously emitted from the oily byproduct, when the oily byproduct was kept under a nitrogen gas flow at atmospheric pressure and at room temperature. When the oily byproduct was exposed to 2-5 % chlorine trifluoride gas in ambient nitrogen at room temperature, various gaseous fluorides were produced, accompanying a slight temperature increase.

Behavior of Viscous Liquid Byproduct Formed in Exhaust Tube by Silicon Carbide Epitaxial Growth

The behavior of the by-product produced in an exhaust tube by the semiconductor silicon carbide epitaxial growth process was evaluated. The by-product layer was a dark-colored viscous liquid; it captured precursor gases and gaseous by-products, such as hydrogen, monosilane, propane, hydrogen chloride and chlorosilanes. These captured gases were spontaneously emitted in ambient nitrogen at room temperature. By an etching process using a chlorine trifluoride gas at low concentrations in ambient nitrogen, the by-product layer could be safely decomposed to gaseous fluorides of silicon and carbon. After finishing the etching, there remained a small amount of residue which included particles of carbon, silicon carbide and related compounds. Based on these results, the by-product layer formation process was discussed.

Mechanisms of growth and defect properties of epitaxial SiC

In the last ten years, large improvements in the epitaxial silicon carbide processes have been made. The introduction of chloride precursors, the epitaxial growth on large area substrate with low defect density, the improvement of the surface morphology, the understanding of the chemical vapour deposition (CVD) reactions, and epitaxial mechanisms by advanced simulations are just the main results obtained in the homo-epitaxy process of 4H-SiC. After this large stride in the process of SiC epitaxial growth, it is time to collect this knowledge in a review that can be a reference point for the future work in this interesting field. The structure of the review is the following. After an introduction on the evolution and history of the epitaxial growth of 4H-SiC, the main physics parameter of this epitaxial growth process is explained in detail using the traditional Burton-Cabrera-Franck theory and the experimental observations of the surface instability due to the off-axis growths. Then the introduction of chlorinated precursors in the epitaxial process is reviewed and the effect of this new process on Schottky diodes characteristics is shown. The improvement of the epitaxy process is strictly related to the improvement of the simulation of the growth that helps the researchers to understand the effect of different parameters on such complex system. Then, a large part of the review is devoted to the simulations of the CVD systems, the reaction in the gas phase of the different precursors and the surface reaction models. Also, some important results obtained by Monte Carlo simulation on the study of different growth parameters that influence the formation of defects and their evolution are reported. Finally, the influence of different process parameters and in particular of the growth rate on the formation or the reduction of the principal defects that are observed in the epitaxial layer is reviewed. We have divided these defects in four categories: 3D defects (epi-stacking faults and inclusions), 2D defects (stacking faults), 1D defects (dislocations), and 0D defects (point defects). Also the influences of the growth parameters on the surface morphology (step-bunching) and the correlation with defects have been reviewed. In the conclusions the main results on the chloride epitaxy has been summarized and an outlook of this process in the next years has been presented with the actual understanding of the mechanism of the silicon carbide epitaxial growth.

縦型低圧CVD炉におけるSiCエピタキシャル成長に関する数値解析

縦型低圧CVD炉におけるSiCエピタキシャル成長に関する数値解析

Behavior of Particles in the Growth Reactor and their Effect on Silicon Carbide Epitaxial Growth

Formation of particles and their effect on SiC epitaxial growth in the CVD reactor is investigated. Particle induced defects in the epilayer at different gas decomposition conditions are discussed. A higher number of pits with larger diameters are observed in the epilayer for conditions where gases decompose later in the gas injector tube (i.e. nearer to the substrate). On the other hand, the number and size of these pits reduce for the condition where gas decomposes earlier in the tube. To investigate the effect of particles during the growth, various particles with different size, shape and compositions are intentionally placed on the substrate surface before epitaxial films are grown. Samples are mapped and compared at similar locations in the pre-growth, post growth and post-etch (by molten KOH) conditions. It is found that the nature of particle induced defects depends primarily on size and shape of particles.

Gas-Phase Modeling of Chlorine-Based Chemical Vapor Deposition of Silicon Carbide

Kinetic calculations of the chemical phenomena occurring in the epitaxial growth of silicon carbide are performed in this study. The main process parameters analyzed are precursor types, growth tem ...

Epitaxial growth of SiC with chlorinated precursors on different off-angle substrates

This study focuses on the epitaxial growth of silicon carbide (SiC) epitaxial layers, adopting the chloride-based chemical-vapor-deposition (CVD) process, which allows to achieve ten times higher growth rate compared to the standard process based on the mixture of a silicon-containing gas and a hydrocarbon.In order to improve the material quality, substrates with different off-angles were used, since low off-angle substrates result in a reduction of killer defects for specific devices. Different growth mechanisms dominate for different substrate off-cut and an accurate set up of dedicated surface preparation procedures and tuning of growth parameters are needed. This study demonstrates that silicon-rich gas inputs are favorable for lower off-angle (nominally on-axis) substrates, while carbon-rich are beneficial for higher off-angles (usually 8° off-axis for 4H–SiC).Methyltrichlorosilane (MTS) is shown to be the best precursor to achieve the presented results.

Investigations of defect evolution and basal plane dislocation elimination in CVD epitaxial growth of silicon carbide on eutectic etched epilayers

Defects in silicon carbide (SiC) epilayers are examined by a growth (the first epilayer)–etch–regrowth (the second epilayer) process. The first SiC epilayer is mildly etched by molten KOH–NaOH eutectic to generate etch pit sizes of 2–12 μm using a well-controlled process with good reproducibility, and then the second epilayer is grown on the etched epilayer. The evolution of defects from the first epilayer to the second epilayer is investigated. All of the individual basal plane dislocations (BPDs) in the first epilayer are converted to threading edge dislocations (TEDs) in the second epilayer, regardless of the etch pit size of the BPDs. The BPD conversion may be accompanied by dislocation migration towards the up-step direction depending on the size of the etch pits. All of the in-grown stacking faults (IGSFs) with triangular shape in the first epilayer are propagated into the second epilayer. The IGSFs are shown to be introduced only by the growth process. Due to the mild nature of eutectic etching, the etching process does not enhance the generation of any defects, especially stacking faults, or degrade the epilayer surface morphology. Since no new individual BPDs are generated in the second epilayer, a BPD-free epilayer is achieved successfully with good surface morphology.

Epitaxial Growth and Defect Control of SiC for High-Voltage Power Devices

Recent progress in fast epitaxial growth and defect control of silicon carbide (SiC) toward development of high-voltage power devices is reviewed. In chemical vapor deposition of 4H-SiC on off-axis (0001), a high growth rate of 85 µm/h and a low background doping of 1×1013 cm−3 are achieved. Conversion of basal-plane dislocations to threading edge dislocations and generation of stacking faults during epitaxial growth are discussed. Deep levels in as-grown n-type and p-type 4H-SiC epitaxial layers have been investigated. A lifetime-killing defect, Z1/2 center, can be almost eliminated by thermal oxidation, which leads to significant increase in carrier lifetimes. The obtained carrier lifetimes are long enough to fabricate 10 kV-class bipolar devices. Control of carrier lifetimes by low-energy electron irradiation is demonstrated.

Reduced Gas Phase and Surface Kinetics for Silicon Carbide Epitaxial Growth

To increase the SiC surface quality up to electronic grade the deposition of epitaxial layers is still necessary. Unfortunately, this process is very difficult to control both in terms of film composition and of flat area portion of the reactor. Moreover, the traditional deposition process using silane/hydrocarbons/hydrogen mixtures is affected by significant problems related to the nucleation of particulate that significantly limit the lifetime of the deposition chamber. To overcome these problems the addition of hydrochloric acid or directly the use of chlorosilanes or even chlorinated hydrocarbons have been proposed. In that cases the deposition mechanism is still not well established and the proposed mechanisms involve a great number of reactions and species. Here, a sensitivity analysis was performed to reduce the more general mechanism, with the particular aim to select the most important reactions to be lately studied by a fundamental quantum mechanics approach.

Gas‐Phase and Surface Kinetics of Epitaxial Silicon Carbide Growth Involving Chlorine‐Containing Species

AbstractA detailed chemical mechanism for the silicon carbide epitaxial growth using light hydrocarbons, silane, and either chlorosilanes and/or HCl as the chlorine source is presented. The mechanism involves 153 gas‐phase and 76 surface reactions among 47 gas‐phase and 9 surface species, respectively. A comparison with the performances of the standard process using silane‐hydrocarbons is presented, and the observed growth rate increase and the disappearing of the homogeneous silicon droplets in gas phase is explained.

Reduced Gas Phase and Surface Kinetics for Silicon Carbide Epitaxial Growth

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Silicon carbide growth mechanisms from SiH4, SiHCl3 and nC3H8

AbstractA detailed chemical mechanism for the silicon carbide epitaxial growth using chlorinated precursors is presented here. The mechanism involves 155 gas phase and 66 surface reactions among 47 gas phase and 9 surface species, respectively. A comparison with the performances of the standard process using silane is presented and the observed growth rate increase and the disappearing of the homogeneous silicon droplets in gas phase is explained. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Reducing stress in silicon carbide epitaxial layers

A susceptor for the epitaxial growth of silicon carbide, with an up-lifted substrate holder, is investigated and compared to other susceptor designs both experimentally and by the use of computational fluid dynamics simulations. It is shown that the wafer bending due to temperature gradients is diminished in a hot-wall reactor compared to growth in a cold-wall reactor. The substrate backside growth is diminished using the up-lifted substrate holder, limiting the substrate bending due to the backside growth. Thereby the stress built into the epitaxial layers during growth is significantly reduced. Simulations indicate a lower effective C/Si ratio over the wafer, and a lower preferable growth temperature, as compared to the original susceptor design. In addition a slightly higher growth rate is achieved.

Low Temperature Selective and Lateral Epitaxial Growth of Silicon Carbide on Patterned Silicon Substrates

Low Temperature Selective and Lateral Epitaxial Growth of Silicon Carbide on Patterned Silicon Substrates

Computational modeling of SiC epitaxial growth in a hot wall reactor

A computational model for chemical vapor deposition (CVD) of silicon carbide (SiC) in a hot-wall reactor is developed, where the susceptor is tapered with a rectangular cross-section. The present work focuses on the advection–diffusion-reaction process in the susceptor. The precursors are propane and silane, and the carrier gas is hydrogen with mass fraction higher than 99%. Computed growth rates under different system pressures and precursor concentrations are compared to the experimental data measured on samples grown in the Linköping CVD reactor. The gas composition distribution in the susceptor and the growth rate profile on the susceptor floor are shown and analyzed. Dependence of the growth rate on precursor concentrations is investigated. It is demonstrated that the growth rate of SiC may either be carbon transport limited or silicon controlled, depending on the input carbon-to-silicon ratio.

SiC Epitaxial Growth by Vertical Hot-Wall Type Chemical Vapor Deposition.

Epitaxial growth of silicon carbide (SiC) by “Vertical hot-wall type chemical vapor deposition (CVD)” has been investigated. Higher growth rates over 10μm/h has been realized at a growth temperature of 1700oC. The surface morphology has been observed by atomic force microscopy to examine formation of macroscopic steps. In addition to conventional (0001) face, 6H- and 4H-SiC epitaxial layers with smooth surfaces have been realized on (11-20) and (1-100) faces. Crystallographical quality of epitaxial layers has been evaluated by X-ray diffraction. Furthermore, we developed a novel doping method, “Pulse doping”, during epitaxial growth for a well-controlled doped layer. A pulse valve that could open and close within a very short period less than 10 μs was used in this study to supply the dopant gases. Carrier concentrations of the doped layers have been precisely controlled, and their abrupt doping profiles have been achieved.

Modeling of Silicon Carbide Epitaxial Growth in Hot‐Wall Chemical Vapor Deposition Processes

A complete two‐dimensional axisymmetric model for chemical vapor deposition (CVD) is presented, incorporating induction heating by a radio frequency coil, flow, heat transfer (radiation included), and gas and surface chemistry, applied to epitaxial growth of silicon carbide (SiC) with as the carrier gas and and as precursors. Temperatures range from 1873 to 1923 K. Predictions are compared to full‐scale experiments carried out in the Linköping hot‐wall CVD reactor for epitaxial growth. Temperature predictions have previously shown to agree well with experiments; consequently, this paper focuses on the reaction mechanism model. Three different reaction mechanisms are compared to experiments where mechanisms contain 35 gas, seven surface, and two bulk species including gas and surface reactions. The predicted growth rate agrees well with experiments for 300 mbar but is slightly low for 50 mbar and somewhat high for 550 mbar. By including a recent mechanism for decomposition of , morphological conditions can be predicted comparing partial pressures of Si and to experimental data from the literature. The predicted growth rate is not influenced by this additional model. It is demonstrated that when a model for hydrogen etching of the susceptor graphite is included, correct growth limitation is predicted. © 2000 The Electrochemical Society. All rights reserved.

Selective epitaxial growth of silicon carbide on SiO2 masked Si(100): The effects of temperature

The effect of substrate temperature on the growth rate, crystal grain size, and SiO2 mask stability in the selective epitaxial growth of silicon carbide deposited from SiH4, C2H4, and HCl1 on silicon dioxide masked silicon (100) was examined. Depositing at atmospheric pressure and a Cl/Si input ratio of 50 to achieve good selectivity, increasing the substrate temperature from 950 to 1000 °C increased the growth rate and the crystal size, and improved the film’s surface morphology, but also enhanced the SiO2 mask degradation rate, causing a loss of selectivity for long deposition times. For prolonged deposition times at 1000 °C, SiC nucleation occurred at both voids formed in the mask from its reaction with the silicon substrate and on the SiO2 mask itself—a consequence of increasing oxide surface roughness.