Papers by Author: Peter Friedrichs

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Authors: Dethard Peters, Adolf Schöner, Peter Friedrichs, Dietrich Stephani
Authors: Christian Hecht, Bernd Thomas, René A. Stein, Peter Friedrichs
Abstract: In this paper, we present results of epitaxial layer deposition for production needs using our hot-wall CVD multi-wafer system VP2000HW from Epigress with a capability of processing 7×3” or 6×100mm wafers per run in a new 100mm setup. Intra-wafer and wafer-to-wafer homogeneities of doping and thickness for full-loaded 6×100mm and 7×3” runs will be shown. Results on Schottky Barrier Diodes (SBD) processed in the multi-wafer system will be given. Furthermore, we show results for n- and p-type SiC homoepitaxial growth on 3”, 4° off-oriented substrates using a single-wafer hot-wall reactor VP508GFR from Epigress for the development of PiN-diodes with blocking voltages above 6.5 kV. Characteristics of n- and p-type epilayers and doping memory effects are discussed. 6.5 kV PiN-diodes were fabricated and electrically characterized. Results on reverse blocking behaviour, forward characteristics and drift stability will be presented.
Authors: Dietrich Stephani, Reinhold Schörner, Dethard Peters, Peter Friedrichs
Abstract: We have carefully investigated a number of more than 120 selected chips fabricated on one wafer, by I-V measurements at two different precisely controlled temperatures and precision CV measurements at room temperature. From these measurements the net-doping concentration, the C-V (flat-band) barrier ΦCV, the ideality n, the apparent Richardson constant Aapp and the apparent I-V barrier Φapp have been extracted for each chip. An extremely unique C-V barrier was determined showing a relative standard deviation (sigma over mean) of only 0.086%. Moreover, the average ideality n was found to be as low as 1.028 exhibiting a relative standard deviation of only 0.35%. A clear linear correlation (ρ2 = 0.968) between ideality n and apparent I-V barrier was observed. The effective Richardson constant A** of 4H-SiC in 〈0001〉 directions could therefore be extracted to be most likely in the interval 70 Acm-2K-2 < A** < 80 Acm-2K-2.
Authors: Martin Rambach, Anton J. Bauer, Lothar Frey, Peter Friedrichs, Heiner Ryssel
Abstract: Furnace annealing and lamp annealing of aluminum implanted layers in 4H silicon carbide (SiC) were investigated with respect to surface degradation and electrical parameters. A sheet resistance of about 20kW/ı was obtained for an aluminum implantation dose of 1.2×1015cm-2 and annealing in the furnace at 1700°C for 30min. For the same implantation dose, lamp annealing at 1770°C for 5min resulted in a three times higher sheet resistance of 60kW/ı. The surface roughness was best for the lamp system and stayed below 1nm for Al doses lower than 1×1015cm-2.
Authors: Peter Friedrichs, Heinz Mitlehner, Reinhold Schörner, Karl Otto Dohnke, Rudolf Elpelt, Dietrich Stephani
Authors: Heinz Mitlehner, Peter Friedrichs, Rudolf Elpelt, Karl Otto Dohnke, Reinhold Schörner, Dietrich Stephani
Authors: Bernd Thomas, Christian Hecht, René A. Stein, Peter Friedrichs
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.
Authors: Dethard Peters, Peter Friedrichs, Reinhold Schörner, Dietrich Stephani
Authors: Michael Grieb, Masato Noborio, Dethard Peters, Anton J. Bauer, Peter Friedrichs, Tsunenobu Kimoto, Heiner Ryssel
Abstract: The electrical characteristics and the reliability of different oxides on the 4H-SiC Si-face for gate oxide application in MOS devices are compared under MOSFET operation conditions at room temperature, at 100°C and at 130°C. The oxides are either an 80nm thick deposited oxide annealed in NO or an 80nm thick grown oxide in diluted N2O. The deposited oxide shows significant higher QBD- and lower Dit-values as well as a stronger decrease of drain current under stress than the grown oxide. Although for the deposited oxide, the leakage current below subthreshold increases more than one order of magnitude during constant circuit stress at room temperature, for the thermal oxide it is quite constant, but at higher level for higher temperatures.
Authors: Masato Noborio, Michael Grieb, Anton J. Bauer, Dethard Peters, Peter Friedrichs, Jun Suda, Tsunenobu Kimoto
Abstract: In this paper, nitrided insulators such as N2O-grown oxides, deposited SiO2 annealed in N2O, and deposited SiNx/SiO2 annealed in N2O on thin-thermal oxides have been investigated for realization of high performance n- and p-type 4H-SiC MIS devices. The MIS capacitors were utilized to evaluate MIS interface characteristics and the insulator reliability. The channel mobility was determined by using the characteristics of planar MISFETs. Although the N2O-grown oxides are superior to the dry O2-grown oxides, the deposited SiO2 and the deposited SiNx/SiO2 exhibited lower interface state density (n-MIS: below 7x1011 cm-2eV-1 at EC-0.2 eV, p-MIS: below 6x1011 cm-2eV-1 at EV+0.2 eV) and higher channel mobility (n-MIS: over 25 cm2/Vs, p-MIS: over 10 cm2/Vs). In terms of reliability, the deposited SiO2 annealed in N2O exhibits a high charge-to-breakdown over 50 C/cm2 at room temperature and 15 C/cm2 at 200°C. The nitrided-gate insulators formed by deposition method have superior characteristics than the thermal oxides grown in N2O.
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