Papers by Author: Elisabeth Blanquet

Abstract: In order to achieve AlN bulk growth, HTCVD chlorinated process is investigated. High growth rate and high crystalline quality are targeted for AlN films grown on (0001) 4H SiC at 1750°C. The precursors used are ammonia NH3 and aluminium chlorides AlClx species formed in situ by action of Cl2 on high purity Al wire. Influences of N/Al ratio in the gas phase on growth rate, crystalline state and microstructure are presented. Growth rates of up to 200 µm/h have been reached for polycrystalline layers. Thermodynamic calculations were carried out and correlated to the experimental results. As-grown AlN layers were characterized by SEM and X-ray Diffraction. Surface morphology is studied by SEM and FEG-SEM and crystallographic orientations were obtained by X-ray diffraction on θ/2θ.

Abstract: To achieve AlN bulk growth, HTCVD chlorinated process is investigated. High growth rate and high crystalline quality are targeted for AlN films grown on (0001) α-Al2O3 and (0001) 4H or 6H SiC substrates between 1100 °C and 1750 °C. The precursors used are ammonia NH3 and aluminium chlorides AlClx species formed in situ by action of Cl2 on high purity Al wire. Both influences of temperature and carrier gas on microstructure, crystalline state and growth rate are presented. Growth rates higher than 190 μm.h-1 have been reached. Thermodynamic calculations were carried out to understand the chemistry of AlN deposition. AlN layers were characterized by SEM and θ/2θ X-Ray Diffraction. Their epitaxial relationships with substrates were deduced from pole figures obtained by X-Ray diffraction on a texture goniometer.

Abstract: Modeling and simulation of the SiC growth processes, Physical Vapor Transport (PVT), Chemical Vapor Deposition (CVD), are sufficiently mature to help building new process equipment or up-scaling old ones. It is possible (i) to simulate accurately temperature and deposition distributions, as well as doping (ii) to quantify the limiting phenomena, (iii) to understand the important role of different precursors in CVD and hydrogen additions in PVT. The first conclusion of this paper is the importance of the "effective" C/Si ratio during CVD epitaxy in hot-wall reactors and its capability to explain the doping concentrations. The second conclusion is the influence of the C/Si ratio in alternative bulk growth technique involving gas additions.

Abstract: The transfer by wafer-bonding of single-crystalline SiC thin films to a polycrystalline SiC support to obtain a “quasi-wafer” is an attractive way for lowering the cost of silicon carbide wafers. Such a process needs high quality polycrystalline substrates, with controlled and high-level bulk properties (thermal conductivity, electrical resistivity) and with very low surface roughness and surface bowing. Currently, polycrystalline SiC wafers which are available are siliconized SiC or CVD processed SiC wafers. Siliconized ceramic wafers are very heterogeneous (mixture of 3C, 6H, 15R and silicon), while CVD ones are of better quality (homogeneous and textured 3C). However neither the siliconized SiC nor the CVD SiC can be CMP polished with low roughness over large dimension. In this paper, wafers with large and textured grains (> 1cm) are processed and characterized. The polishing of such structures is studied and optimized to obtain low surface roughness. To meet these requirements high temperature processes used for single crystal growth were selected. Structural investigations performed on the grown ingots showed an important influence of the used seed since no preferential crystallographic orientation was observed during the growth. The final polishing quality was of high level but step heights were observed between grains.

Abstract: We review the development of a modified physical vapor transport (M-PVT) growth technique for the preparation of SiC single crystals which makes use of an additional gas pipe into the growth cell. While the gas phase composition is basically fixed in conventional physical vapor transport (PVT) growth by crucible design and temperature field, the gas inlet of the MPVT configuration allows the direct tuning of the gas phase composition for improved growth conditions. The phrase "additional" means that only small amounts of extra gases are supplied in order to fine-tune the gas phase composition. We discuss the experimental implementation of the extra gas pipe and present numerical simulations of temperature field and mass transport in the new growth configuration. The potential of the growth technique will be outlined by showing the improvements achieved for p-type doping of 4H-SiC with aluminum, i.e. [Al]=9⋅1019cm-3 and ρ<0.2Ωcm, and n-type doping of SiC with phosphorous, i.e. [P]=7.8⋅1017cm-3.

Abstract: Modeling and simulation of the SiC growth process is sufficiently mature to be used as a training tool for engineers as well as a decision making tool, e.g. when building new process equipment or up-scaling old ones. It is possible to simulate accurately temperature and deposition distributions, as well as doping. The key of success would be the combined use of simulation, experiments and characterization in a "daily interaction". The main limitation in SiC growth modeling is the accurate knowledge of physical, thermal, radiative, chemical and electrical data for the different components of the reactor. This is the weakest link in developing completely predictive models. In addition, the link between the thermochemical history of the grown material and its structure and defects still needs further development and input of experimental data.