Materials Science Forum Vols. 821-823

Abstract: The reduction of the growth pressure was demonstrated to have the same effect as the addition of chloride-containing gas on preventing the Si nucleation and the epitaxy with high growth rate (>50 μm/h) was achieved by using the decreasing pressure condition in a horizontal CVD reactor without chloride-containing gas. The quality of a 30-μm-thick epilayer grown with 40 μm/h was also investigated. Downfall and triangle defect density in the layer was as low as 0.16 /cm², indicating that a high quality epitaxial wafer can be easily obtained under the condition with high throughput in the sinple CVD system.

Abstract: This paper presents one of the first comparative studies of distinctive results obtained using halogenated silicon precursors, dichlorosilane (SiH₂Cl₂, DCS) and tetrafluorosilane (SiF₄, TFS) for SiC homo epitaxial growth. Both TFS and DCS possess very distinct properties that show specific influence on SiC growth. SiC epitaxial growth using TFS greatly suppresses parasitic deposition in the gas delivery system. Growth using TFS shows carbon mediated growth regime, and exhibits controlled doping concentration of the epilayer by an order of magnitude lower than that in the growth using DCS at the same C/Si ratio. Studies of epilayer surface morphology show that the epilayers from TFS growth have a specular surface in a wide C/Si range whereas in the growth using DCS, the epilayer surface roughness is strongly dependent on the C/Si ratio.

Abstract: The influence of chlorine has been investigated for high growth rates of 4H-SiC epilayers on 4o off-cut substrates. Samples were grown at a growth rate of approximately 50 and 100 μm/h and various Cl/Si ratios. The growth rate, net doping concentration and charge carrier lifetime have been studied as a function of Cl/Si ratio. This study shows some indications that a high Cl concentration in the growth cell leads to less availability of Si during the growth process.

Abstract: Quasi-thermodynamic model of SiC doping with Al in CVD from C₃H₈, SiH₄, and Al (CH₃)₃ on the Si-face is developed. The model is validated by quantitative agreement of calculated and experimental data on the Al concentration in SiC as a function of temperature, pressure, SiC growth rate, and TMAl flow rate. The model is shown to be consistent with the site competition mechanism of Al incorporation into SiC.

Abstract: An exhaustive experimental study of the influence of C/Si ratio on voluntary incorporation of nitrogen (N) and aluminum (Al) in 4H-SiC thin films is presented. The films were grown by chemical vapor deposition (CVD) in a horizontal, hot wall CVD reactor on Si- and C-face substrates, under Si-rich and C-rich conditions. Under some conditions the observed variation of dopant incorporation with C/Si ratio could be clearly attributed to the site competition effects, while in several cases other mechanisms have to be taken into account.

Abstract: Homo-epitaxial growth of 4H-SiC on 4^o off-axis 150 mm diameter substrates has been performed in a commercial warm-wall multi-wafer planetary reactor. Based on our well developed 100 mm 4H-SiC epitaxial growth process, which can achieve excellent thickness and doping uniformities (δ/mean) of <1% and <5%, respectively, the growth process and hardware were further fine-tuned and improved for 150 mm 4H-SiC homoepitaxy. After the improvement, the 6 to7 μm thick epilayer uniformity has reached 1.1% with a 5mm edge exclusion while the doping uniformity has improved to 16.5% (<10%) with an edge exclusion of 5 mm (10mm), respectively. Surface roughness of the as-grown 150 mm 4H-SiC epitaxial layer has an RMS value of 0.12 nm scanned by AFM on 20×20 μm² areas. Homo-epitaxial growth on C-face 150 mm 4H-SiC substrates has also been carried out. Other than the doping concentration and uniformity, the other results are very close to the epi-growth on Si-face.

Abstract: In this work a new epitaxial process on 6 inches has been performed on 2° off-cut substrate. This off-cut will reduce the material loss during substrate preparation from the crystal boule. The thickness and doping uniformity of the samples grown in the LPE reactor PE1O6 is extremely good and the PL map shows a low defects density. The roughness is slightly higher on 2° off-cut and the process window becomes narrower.

Abstract: This paper presents the current performance of 150mm SiC epitaxy on state-of-the-art 150mm substrates. Excellent on-wafer uniformity has been achieved with mean thickness uniformity at 1.8% and mean doping uniformity at 5.4%. The epilayer surface is smooth across wafer diameter with a typical defect density below 1 cm^-2. Within a run, wafer-to-wafer variation of 0.7 % for thickness and 5% for doping is demonstrated. The mean values of warp and bow after epitaxy are 35 um 15 μm, respectively. The above metrics are critical to enable cost effective production of 150mm SiC epiwafers suited for device fabrication.

Abstract: We present results on the homo-epitaxial growth on the Si face of 100 mm and 150 mm (0001)-oriented (4° off-orientation) 4H SiC wafers utilizing the horizontal hot-wall batch reactor Probus-SiC^TM from Tokyo Electron Limited. Standard epitaxial growth processes show very high levels of intra-wafer, intra-run wafer-to-wafer, and run-to-run uniformities in the layer thickness as well as in the n-type doping concentration. N-type background doping levels less that 5e13 /cm³ have been reached. AFM measurements reveal a surface roughness of 0.2nm (rms). The density of epitaxy related defects such as triangular defects, carrots, and ingrown particles due to downfall are very low, as confirmed by high blocking yields.

Abstract: The guidelines necessary to improve the n-type doping uniformity on C-face epitaxial growth of 4H-SiC have been examined as far as the practical throughput is maintained, e.g. 3×150 mm wafers with the growth rate higher than 20 μm/h. The flow-channel enlargement was carried out and the effect was estimated by temperature distribution estimation performed by hydrogen etching. Also, effective C/Si was simulated with the temperature distribution obtained from the hydrogen etching experiments. As a result, positional agreement was found between the region where carrier concentration begins to increase and the drastic drop in temperature and the effective C/Si ratio.