Papers by Keyword: Hot-Wall CVD

Abstract: The rapid market development for SiC-devices during the last years can be attributed particularly to the success in supplying high-quality SiC wafers and corresponding epitaxial layers. The device quality could be enhanced and the costs were reduced by enlarging the wafer size as well as by a significant progress in epitaxial growth of active layers by using multi-wafer CVD systems. In this paper we want to give an overview of CVD multi-wafer systems used for SiC growth in the past and today. We present recent results of SiC homoepitaxial growth using our multi-wafer hot-wall CVD system. This equipment exhibits a capacity of 5×3” wafers per run and can be upgraded to a 7×3” or 5×4” setup. By optimizing the process conditions epitaxial layers with excellent crystal quality, purity and homogeneity of doping and thickness have been grown. Issues like reproducibility, drift of parameters and system stability over several runs will be discussed.

Abstract: From the engineering point of view, SiC hot-wall epitaxy is a very important process in SiC semiconductor processes. There are lots of experimental reports on SiC hot-wall epitaxy. They discussed the growth rate, surface morphology, doping concentration, etc. Recently, the effect of face polarity is also made clear. However, each report mentioned the particular results that strongly depend on the experimental conditions and reactor design. In addition, the discussion with inlet condition such as source gas C/Si ratio, not the depositing surface condition, leads to the confusion. In order to understand and try to design and optimize the hot-wall CVD reactor, a numerical approach is attempted. The authors have tried to make it clear that depositing surface condition might be a universal parameter of SiC CVD, and the numerical simulation could predict the growth rate, surface morphology and doping concentration by taking account of the depositing surface condition. In this study, at first, the recent progress of SiC hot-wall epitaxy in experiment is summarized. Then, the present status of its numerical modeling is explained.

Abstract: The ZnSe epilayers were grown on the GaAs substrate by hot wall epitaxy. After the ZnSe epilayers treated in the vacuum-, Zn-, and Se-atmosphere, respectively. The defects of the epilayer were investigated by means of the low-temperature photoluminescence measurement. The dominant peaks at 2.7988 eV and 2.7937 eV obtained from the PL spectrum of the as-grown ZnSe epilayer were found to be consistent with the upper and the lower polariton peak of the exciton, I2 (Do, X), bounded to the neutral donor associated with the Se-vacancy. This donorimpurity binding energy was calculated to be 25.3 meV. The exciton peak, I1 d, at 2.7812 eV was confirmed to be bound to the neutral acceptor corresponded with the Zn-vacancy.

Abstract: Large area 4H-SiC PIN diodes have been fabricated which exhibit a stable avalanche ranging between 4.5 and 5.5 kV. The avalanche occurs at an electrical field strength of 2.1 MV/cm at the pn junction. The temperature coefficient of the avalanche is positive (0.3 V/K). The avalanche is tested in DC mode. The device concept as well as the fabrication process is described in detail. Static and dynamic characteristics are shown.

Abstract: In this paper we present recent results of epitaxial growth of 4H-SiC on 3” (0001) 8° and 4° off-oriented wafers using a multi-wafer hot-wall CVD system. This equipment exhibits a capacity of 5x3” or 7x2” wafers per run. By optimizing the process conditions epitaxial layers with excellent crystal quality, purity and homogeneity in doping and thickness were grown. The intra-wafer as well as the wafer-to-wafer homogeneity will be illustrated by doping and thickness mappings of a full-loaded run. Surface morphology of epitaxial layers on 8° and 4° off-oriented wafers was investigated by atomic force microscopy.

Abstract: Mechanisms and consequences of silicon vapor condensation during SiC epitaxial growth or implant annealing with silane overpressure were investigated. The model for the silicon liquid droplets formation in the gas phase and their deposition on the surface of the SiC substrate was developed. The droplet formation dependence on the silane flow rate, temperature profile in the reactor, and the local temperature variations introduced by the wafer carrier and SiC substrate were investigated.

Abstract: 4H-SiC layers have been homoepitaxially grown on off-axis 4H-SiC(000-1) under various conditions by horizontal hot-wall CVD. Improvement of surface morphology and reduction of background doping concentration have been achieved. Surface morphology grown on the (000-1) C face strongly depends on the C/Si ratio at 1500 °C, and hillock-like surface defects can be eliminate by increasing growth temperature to 1600 °C. Site-competition behavior is clearly observed under low-pressure growth conditions even on the (000-1) C face. The lowest doping concentration has been determined to be 6.0x1014 cm-3. A trial of high-speed growth on the (000-1) C face and deep level analysis are also discussed.

Abstract: The results of the initial experiments with halogenated carbon precursor chloromethane (CH3Cl) for epitaxial growth of 4H-SiC are presented. The growth rate for mirror-like morphology was easily increased up to about 7 µm/hr at C-rich conditions without detectable surface morphology degradation. Further increase of the silane flow resulted in island formation. The growth with the traditional silane-propane system at the same conditions (and optimized Si/C ratio) produced a very different result, with the growth rate decreasing from upstream to downstream, and morphology degradation taking place for much lower growth rate than in CH3Cl growth. Consequently, the epitaxial growth with chloromethane appears to have significantly different kinetics of the gas-phase precursor decomposition and different mechanisms of the surface reactions, which favors the step-flow growth. In addition, these preliminary data indicated that the maximum achievable growth rate corresponding to the good surface morphology may be noticeably larger for the CH3Cl+SiH4+H2 growth system.

Abstract: Hydrogen chloride (HCl) was added to a standard SiC epitaxial growth process as an additive gas. A low-pressure, hot-wall CVD reactor, using silane and propane precursors and a hydrogen carrier gas, was used for these experiments. It is proposed that the addition of HCl suppresses Si cluster formation in the gas phase, and possibly also preferentially etches material of low crystalline quality. The exact mechanism of the growth using an HCl additive is still under investigation, however, higher growth rates could be obtained and the surfaces were improved when HCl was added to the flow. The film morphology was studied using SEM and AFM and the quality with LTPL analysis, which are reported.

Abstract: The Hot-Wall CVD reactor was developed for the thick epitaxial SiC layers needed for high voltage power devices but its inherent better properties – better cracking efficiency of the precursor gases and better lateral and vertical temperature homogeneity – should also influence the growth of other materials such as the III-nitrides. We will give some examples of thick SiC layers grown on either off- or on-axis substrates with this technique. We will also show that high-quality III-nitride materials can be grown.