Silicon Carbide Epitaxy in a Vertical CVD Reactor: Experimental Results and Numerical Process Simulation

Abstract

In this paper an overview is given on the epitaxial growth of SiC in a vertical CVD reactor. Results concerning impurity incorporation and ways to achieve background doping levels as low as 1014 cm—3 are discussed. Precise control of the C/Si ratio in the gas phase, which is easily achieved in the described reactor, and the use of reduced pressure, lead to good control of dopant incorporation over more than three orders of magnitude, and smooth surface morphology at growth rates higher than 5 μm/h. Doping variations <±12% across 35 mm wafers can routinely be obtained. The quality of the epilayers is proven by electrical brakdown fields as high as 2×106 V/cm at NA — ND = 5×10—15 cm—3 achieved in both pn and Schottky diodes and an electron mobility higher than 700 cm2/Vs at 300 K (4H‐SiC) estimated from the on‐resistance of these test devices. Another important experimental boundary condition, the influence of the gas composition at the end of the epitaxial growth process on the surface properties of the epitaxial layer, is described. It will be shown that surfaces nearly resistant against oxidation can be generated in a hydrogen free atmosphere. As a second main topic of this paper, results of an elaborate numerical process simulation will be described including both fluid mechanical and chemical behavior. The influence of the main process parameters like total flow, chamber pressure, and rotation speed on the stability of the flow was investigated. The results achieved are compared with experimental observations showing excellent agreement. The experimental observation of an irradiant layer in the gas phase in front of the wafer under typical process conditions is explained with the help of the numerical model. The usefulness of this specific feature for the optimization of process conditions is discussed.

Silicon rich oxide powders by HWCVD: Its optical and morphological properties

“…When the distance source-substrate increases, the growth temperature decreases, and with this conditions the environment is supersaturated and it is partially condensed. A thin layer of different clusters is formed over the substrate [31,32], as shown in Fig. 6a.…”

“…It is widely accepted that the visible red emission is related to the presence of silicon nanoparticles (Si-nps) embedded in SiO 2 and defects [26,27,29,[32][33][34]. The defects that contribute to PL spectra are shown in the Table 1 and an example of the deconvolution can be seen in Fig.…”

“…Photoluminescent defects reported in a silica matrix with Si-ncs and observed in the SROP samples[26][27][28][29][30][31][32][33][34].…”

High temperature CVD growth of SiC

“…As reported in Refs. [7,8], the use of increased concentrations of the silane precursor leads to the formation of Si-clusters due to homogeneous gasphase nucleation. Chemical interactions with the hydrocarbon precursor may further stabilise the silicon clusters, possibly by formation of Si-Si x C y clusters.…”

Two- and three-dimensional simulation of chemical vapor deposition SiC epitaxial growth processes

“…[1][2][3][4] Even moderate changes in the reactor size and geometry can influence at least some of the growth conditions mentioned above. In the present study, computational fluid dynamics (CFD) simulations were used to determine factors that are the most critical for arriving at optimal process conditions.…”