Papers by Keyword: 4H-SiC Power Device

Abstract: This study investigates the electric dipole effect at Al₂O₃/SiO₂ interfaces deposited by Atomic Layer Deposition (ALD) on 4H-silicon carbide (SiC) substrates for threshold voltage (V_T) modulation. By incorporating an ultrathin 3nm Al₂O₃ layer onto ALD-deposited 30nm SiO₂, they created an electric dipole that produces a 0.65±0.15V positive shift in threshold voltage after N₂O post-deposition annealing. The dipole-induced voltage shift was validated through both MOS capacitor measurements and lateral MOSFET characterization. Importantly, the threshold voltage enhancement occurred without degradation in field-effect mobility, demonstrating that the dipole effect does not introduce additional scattering centers. This technique offers an effective approach for threshold voltage tuning in alternative semiconductor devices where thermal SiO₂ growth is not feasible, addressing critical challenges in SiC power electronics that require high threshold voltages (>3V) for reliable operation.

Abstract: Infineon’s 5^th Generation of 1200V SiC diodes uses a new compact chip design, realized by an optimized hexagonal merged-pn cell structure in the active area. This allows a higher n-doping in the epi layer due to improved E-field shielding resulting in a smaller differential resistance per chip area. Thanks to the merged-pn cell structure, depending on the diode ampere rating, a surge current capability now rated up to 14 times the nominal current ensures robust diode operation during surge current events in the application. The previous generations of 1200V SiC diodes could not make full use of the high breakdown field strength of the SiC material due to the instable avalanche which occurs at the edge termination only, and therefore, requiring a significant safety margin between rated voltage and breakdown voltage. Now the 5^th Generation is designed in a way that each cell contributes to the avalanche, enabling a much more avalanche rugged device.

Abstract: In this paper we compare the thermal behavior of identical SiC Schottky diodes mounted in i) a standard TO220 package (TO220) with non-isolated backside applying standard soft solder and diffusion solder die attach with ii) a so called FULLPAK TO220 package (TO220FP, only diffusion soldering). Depending on the solder technique the heat transport from the junction area of the SiC Schottky diode to the heat sink or to the package backside is improved for the diodes mounted via diffusion solder. For small chips this holds even for TO220FP in comparison to TO220 with standard solder. Simulations of the vertical temperature distribution after electrically heating with a half sine wave for 10ms up to 190W show a decrease of the maximal junction temperature of the SiC Schottky diode from TJ=260 °C to TJ=180 °C if the diffusion solder is used independent from the package type.

Abstract: In this work we studied different Schottky contacts to 4H-SiC with the aim to obtain Schottky Barrier diodes (SBDs) and Junction Barrier Schottky diodes (JBS) able to operate at high temperatures, frequencies and power densities with low power losses. Schottky contacts were fabricated using Mo and Mo/Al layers annealed up to 600 °C using a Rapid Thermal Process (RTP). A comparison with previous results obtained with Ni, Ti and Ti/Al layers annealed up to 400 °C is also proposed. The Schottky contacts were characterized by means of standard Current-Voltage (I-V) and Capacitance-Voltage (C-V) techniques. X-ray Photoelectron Spectroscopy (XPS) analyses were performed in depth profile mode in order to study the structural evolution of the interface Mo/SiC and Al/Mo during annealing treatments. Mo/Al contacts show a lower barrier height and better overall performances in forward polarization when compared to the Ti- and Ni-based contacts, and they are very promising for Schottky contact fabrication on SBD and JBS.

Abstract: We have studied different Schottky and ohmic contacts on 4H-SiC with the aim to obtain Schottky barrier diodes (SBDs) capable to operate at high temperatures, frequencies and power densities for long periods of time, and showing low power losses. The control of the Schottky barrier plays an important role in minimizing the power loss of a SBD, and the metal-semiconductor interface properties strongly affect the overall performances of such a device. Schottky contacts were deposited using Ni, Ti, Ti/Al, Mo and Mo/Al layers, and the annealing treatments have been performed up to 600 °C using a rapid thermal annealing process (RTA). Ohmic contacts have been deposited on the wafer backside using Ti/Al or Ti/Ni/Ag layers. The Schottky diodes have been characterized by means of standard current-voltage (I-V) and capacitance-voltage (C-V) techniques. Schottky diodes with Mo and Mo/Al barriers show a lower barrier height and better overall performances in forward polarization when compared to the Ti- and Ni-based contacts.

Abstract: We present a theoretical and experimental study on the design, fabrication and characterization of Schottky Barrier Diodes (SBD) on commercial 4H-SiC epitaxial layers. Numerical simulations were performed with a commercial tool on different edge termination structures, with the aim of optimizing the device behavior. For each termination design, SBD were fabricated and characterized by means of electrical measurements vs. temperature. Simulations provided also useful data for the assessment of the device process technology.