Papers by Author: Andrea Canino

Abstract: In this paper the epitaxial process with chloride precursors has been described. In particular it has been shown that the growth rate can be increased to about 100 μm/h but higher growth rate can be difficult to reach due to the limited surface diffusion at the usual temperature of SiC epitaxy. This process gives several advantages because it gives the opportunity to increase the throughput and consequently to reduce the cost of epitaxy, using new reactor structures, and to reduce several kind of defects (Basal Plane Dislocations, Stacking Faults, Threading Dislocations) and to decrease the surface roughness at the same time.

Abstract: 3C-SiC shows encouraging physical properties for the development of low cost high power compatible silicon based technology. The fundamental capability of grown 3C-SiC on silicon substrates leads to the possibility of a full integration of Si based process technologies. This is the driving force for the efforts for development a high quality heteroepitaxial film. The fundamental issue is the reduction of defects and stress due to the lattice mismatch between the 3C-SiC epilayer and the Silicon substrate. In this paper we show a way to reduce macroscopic structural features and to enhance the material quality and the surface quality by simply using a process based on a multilayer (ML) buffer structure with n++ and n doping alternation. This process leads to an evident improvement of both surface roughness, morphology and crystal quality.

Abstract: we study the surface morphology of homoepitaxially grown 4H silicon carbide in terms of growth rate, miscut direction of the substrate and post growth argon thermal annealings. All the results indicate that the final surface morphology is the result of a competition between energetic reorganization and kinetic randomness. Because in all observed conditions energetic reorganization favors surface ondulations (“step bunching”), out-of-equilibrium conditions are one of the keys to favor the reduction of the surface roughness to values below ~0.5 nm. We theoretically support these results using kinetics superlattice Monte Carlo simulations (KslMC)

Abstract: In this paper we study the surface morphology of <11-20> 4° degree off, silicon terminated, 4H Silicon Carbide (4H-SiC) in terms of growth parameters and post growth argon thermal annealing. We find that out-of-equilibrium conditions favor the reduction of the surface roughness. Furthermore, we find preliminary indications that the same growth parameters that lead to the reduction of the surface roughness promote also a reduction of (1,3) and (4,4) stacking faults density.

Abstract: A review of recently achieved results with the chloride-based CVD on 8° and 4° off axis and nominally on-axis 4H-SiC wafers is done to clarify the epitaxial growth mechanisms on different off-angle substrates. The process conditions selected for each off-axis angle become even more difficult when running at growth rates of 100 µm/h or more. A fine-tuning of process parameters mainly temperature, C/Si ratio and in situ surface preparation is necessary for each off-angle. Some trends related to the surface properties and the effective C/Si ratio existing on the surface prior to and during the epitaxial growth can be observed.

Abstract: Using several characterization techniques (μ-Raman, mechanical profilometer and microstructure deflections) together with a recent stress model[ ] we study the heteroepitaxial growth of cubic silicon carbide on silicon (100). We show that the observed inconsistency between experimental results might be the result of defects generated on the silicon substrate during the carbonization process. In such a situation wafer curvature techniques do not allow the determination of the stress field in the grown films neither quantitatively nor qualitatively.

Abstract: Micro-Raman spectroscopy has been used to study the dependence between the carrier concentration and electrical mobility in n-doped 3C-SiC films grown on (111) and (100) Si oriented substrates. Local stacking variations observed on the (111) 3C-SiC surface lead to a worse crystal morphology compared to (100) 3C-SiC films resulting in a decrease of the average bulk mobility.

Abstract: SiC is a candidate material for micro- and nano-electromechanical systems (MEMS and NEMS). The fabrication of SiC MEMS-based sensors requires new processes able to realize microstructures on either bulk material or on the SiC surface. The hetero-epitaxial growth of 3C-SiC on silicon substrates allows one to overcome the traditional limitations of SiC micro-fabrication, but the high residual stress created during the film grow limits the development of the material for these applications. In order to evaluate the amount of residual stress released from the epi-film, different micro-machined structures were developed. Finite elements simulations of the micro-machined structures have also been carried out in order to evaluate, in detail, the stress field inside the structures and to test the analytical model used. With finite element modeling a exponential approximation of the stress relationship was studied, yielding a better fit with the experimental data. This study shows that this new approximation of the total residual stress function reduces the disagreement between experimental and simulated data.

Abstract: Spatially resolved micro-photoluminescence has been used to study the Single Shockley faults surface density and properties on 4H-SiC epitaxial layers. The improvement of quality of epitaxial layers due to the chemical vapor deposition process has been studied by measuring the reduction of mean density of Single Shockley faults. The change of faults density has been correlated to the different precursor gas used for the growth. In fact trichlorosilane has been used instead of silane. The change of precursor led to two different advantages: the reduction of basal plane dislocation surface density and the capability to increase the growth rate of the process. Both these features allow reducing the density of Single Shockley faults.

Abstract: Single Shockley faults have been studied in 4H-SiC epitaxial layers by using a spatial resolved micro-photoluminescence technique. In particular the Effect of the UV pumping laser has been investigated. We demonstrated that high power density exposition at 325 nm affects drastically the structural properties of the epitaxial layers leading to a growth of this defect. We also demonstrated that by opportunely tuning the power density of the UV laser on the sample it is possible to analyze a wide area without producing any negative effect.