Ali AMMAR will defend his PhD on February 15th, 2024 at 10AM.
Place : INSA Lyon, building G. Eiffel, Amphitheatre A2
Jury :
Rapporteurs :
M. Andrea IRACE, Professeur des Universités, Université de Naples Federico II
M. Stéphane LEFEBVRE, Professeur des Universités, Université Paris-Saclay
Examinateurs :
Mme. Marie-Laure LOCATELLI, Chargée de Recherche CNRS , UT3-Toulouse INP (UMR 5213)
Encadrement :
M. Dominique PLANSON, Professeur des Universités, Directeur de thèse
M. Luong VIET-PHUNG, Maître de Conférences
Abstract :
There has been a rapid improvement in silicon carbide (SiC) materials and SiC power devices during the last few years. SiC unipolar devices such as Schottky diodes, JFETs and MOSFETs have been developed extensively and advantages of integration of such devices in power systems have been demonstrated. However, for high-power systems such as high-voltage converters, bipolar devices are preferable due to their low on-resistance. In this thesis high voltage bipolar devices such as NPN transistors and PiN diodes are being demonstrated. The main objective of this thesis is to design and fabricate a high-voltage npn BJT (2x2 mm2 ) based on 4H-SiC with the ability to withstand and block more than 10 kV in addition to a decent current gain (β). Features that improve the efficiency of bipolar device peripheral protection and increase the blocking voltage such as junction termination extension and guard rings were studied and integrated in a fully optimized model validated by TCAD simulations before the fabrication process. Eleven photolithographic levels have been processed during the fabrication of the power devices. The peripheral protection is made up of a 360 µm long JTE done by Al implantation with a dose of 1013 cm-2 verified from simulations. Six guard rings are added each long 5 µm with an initial space of 4-µm between the JTE and the first ring. After that a space increment of 0.5 µm is added to the initial one, each time a ring is added (i.e., the space between 1st and 2nd ring is 4.5 µm, between 2nd and 3rd is 5 µm). Four wafers have been processed in a clean room at ESIEE Paris, and high-voltage reverse characterizations were performed using a vacuum probe station at Institute of Saint-Louis, France. The fabricated npn BJT recorded an open-emitter breakdown voltage BVCBO up to +11 kV with a leakage current density of 0.1 mA/cm2. Forward I-V characterizations were done at room temperature in Ampere Laboratory in Lyon. The maximum DC current gain achieved by the 0.56mm2 active area is (β = 27) at a base current (IB = 80 mA) and collector voltage VCE= 13 V, giving a current density of 123 A/cm2. The thesis goals were accomplished, and the next target will be packaging and characterizing optical controlled BJTs, which have been designed in the same project High-Voltage Photo-Switch.
Keywords:
Silicon Carbide, High Voltage Components, Bipolar Transistor, Optical Control