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Epitaxial layers of 4H-SiC are grown on (0001) substrates inclined toward <1120> and <1100> directions. Defects in these films are characterized by deep level transient spectroscopy (DLTS) in order to clarify the dependence of concentrations and activation energies on substrate inclination. DLTS results show no such dependence on substrate inclination but show thickness dependence of the concentration.
Single crystalline 3C-SiC films have been grown on Si(111) substrate at 1200°C by conventional CVD process using HMDS (Hexamethyldisilane). Before columnar growth of SiC, columnar Si was made by depositing Au on Si(111) substrate as a solvent of VLS mechanism. Si growth was carried out by disproportional reaction in halide transport method. The columnar Si was produced on the patterned substrates. The columnar Si was covered by SiC. Needle like columns of SiC can be used for MEMS application such as micro-heat exchanger.
High quality SiC and AlN films allow the fabrication of metal/AlN/SiC MIS structures and SiC/AlN heterostructures that require a low lattice mismatch and excellent thermal stability. Epitaxial SiC on AlN/sapphire was grown using hexamethyldisilane (HMDS) by MOVPE. 2HAlN is epitaxially grown on sapphire by MOCVD, and subsequently SiC is deposited on it. The growth of high quality SiC was achieved in a one step process without any nucleation step using dilute hydrogen in argon (12% H2 + Ar) as the carrier gas, which is less explosive than pure H2. The effect of growth temperature and thickness of AlN on the SiC crystal quality and the surface smoothness were studied. All films were analyzed using reflection high energy electron diffraction (RHEED), Nomarski differential interference contrast microscopy (NDIC), X-ray diffraction (XRD), and atomic force microscopy (AFM). Optimum temperature for SiC growth was between 1300°C and 1350°C. At these temperatures, the grown films show strong epitaxial relationship with AlN and very smooth surfaces (RMS ∼ 0.1- 0.75 nm). At temperatures below 1300°C, the film becomes polycrystalline. At 1400°C, the films show highly textured features, observed by XRD. In the RHEED, however, weak rings appear superimposed on the spot pattern, which implies the grown films are polycrystalline but highly textured. In order to evaluate the effect of underlying AlN thickness on the SiC film, layers with various thicknesses (50, 200, 400 nm) have been used at 1350°C. The SiC film on a 50 nm thick AlN layer shows a very smooth surface (RMS ∼ 0.1 nm) compared to the SiC film on a 400 nm (RMS ∼ 0.7 nm) AlN layer. This seems to be caused by the increasing roughness of the underlying AlN, as it becomes thicker. However, all the films show highly epitaxial growth features, which implies that 50 nm is sufficient to relieve the mismatch strain of the underlying AlN/sapphire.
To reduce the defect density inherent in conventional heteroepitaxial growth of SiC on Si, selective epitaxy followed by lateral epitaxial growth was performed in a conventional atmospheric pressure chemical vapor deposition (APCVD) system. The source gas was primarily hexamethyldisilane (HMDS). Hydrogen was used as the carrier gas and small amounts of hydrogen chloride (HCl) were added to improve the selectivity. Si(001) wafers, with an oxide layer (∼ 700 nm thick) as a mask, were used as substrates. The grown films were analyzed using optical microscopy and scanning electron microscopy (SEM). In earlier work, we had demonstrated the problems associated with the application of this technique – viz., oxide degradation and high growth temperature. Using HMDS, the growth temperature has been considerably reduced allowing the continued use of an oxide mask. Selective growth was demonstrated in films grown at 1250° and below.
We have grown epitaxial layer introducing buffer layer using N2 doping on 6H-SiC (1120) and (1100) substrate. The improvement of morphology could be obtained for (1120) and (1100) epilayers. Morphologies of (1120) epilayers were independent on off-orientations, Morphologies of (1100) epilayers were very sensitive to the off-orientations. The quality of epilayer, and impurity incorporation for a-plane were very influenced by the surface treatment before CVD growth compared to (0001) epilayers.
Cubic SiC was grown on Si substrates by a combination of carbonization and consecutive chemical vapor deposition. Grown layers on the (100) and (111) substrates were single crystalline cubic SiC. Those on the (110) and (211) were poly-crystalline. A model for the mechanism of carbonization was proposed as a result of these observations. Based on this model, the origin of antiphase boundaries were made clear, and antiphase boundaries were expected to be eliminated by controlling atomic steps of the Si surface. In fact, antiphase boundaries were eliminated by introduction of off orientation of Si(lO0) substrates. The relationship between generation of antiphase boundaries and off orientation of the surface was investigated by using spherically polished Si(100) substrates. Off orientation towards (011) was found to be effective for elimination of antiphase boundaries. Off orientation except for towards (011) resulted in generation of antiphase boundaries.
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