Conception et réalisation de composants de puissance à superjonction et à tranchées profondes pour des applications 600 V et 1200 V

Sylvain Noblecourt 1
1 LAAS-ISGE - Équipe Intégration de Systèmes de Gestion de l'Énergie
LAAS - Laboratoire d'analyse et d'architecture des systèmes [Toulouse]
Abstract : New technological ways allowing the realization of deep trench Superjunction devices (diodes or MOS transistors) with a deep trench termination are investigated. The aim of this work is to propose an alternative to conventional MOSFETs in high voltage range (600 V and above): the major challenge is to find the best trade-off between the two main parameters characteristics of these structures: specific on-resistance / breakdown voltage. We developed a technology based on a single N- epitaxial layer (thus reducing the realization cost) and the use of BCB filled, wide and deep trenches associated to boron doping on the trenches sidewalls. Previous works have demonstrated the feasibility of such junction termination and have led to the fabrication of a 1200 V Deep Trench Termination Diode (DT2-Diode). We chose to validate our termination technology by fabricating a Deep trench Superjunction Diode (DT-SJDiode) for 600 V applications. By means of Sentaurus TCAD 2D-simulations, we have first determined the optimal physical and geometrical parameters leading to a best "Breakdown voltage/on-resistance" trade-off. We presented technological results focusing on the more critical points: the control of deep trenches verticality by Deep Reactive Ion Etching technique, according to the Bosch process, and the trench filling with dielectric. We have studied the influence of SF6 etch and C4F8 passivation times on resulting trench verticality: the best anisotropy for 6 µm wide central trenches and 40 µm wide termination trenches is obtained for the couple SF6 (2 s)/ C4F8 (3.5 s). A thermal oxidation after the etch step allows to reduce the size of the scallops that appear on the trenches sidewalls and characteristics of the Bosch process (alternation of etch and passivation steps): the related peak-to-valley distance is lowered from 100 nm to 50 nm. Finally we have successfully filled deep and wide trenches by optimising the BCB spin-coating parameters, the high viscosity of this material rending difficult its spreading all over the wafer. We found that a dispensing rotation speed down to 100 rpm, an implementation of two 10 min rest steps improve BCB spreading and its flowing along the trenches. The BCB excess removing by reactive ion etching is under study: first encouraging results give an etch rate of 0.75 µm.min-1 with a SF6/02 gas mixture.
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Electronique. Université Paul Sabatier - Toulouse III, 2016. Français. 〈NNT : 2016TOU30230〉
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Sylvain Noblecourt. Conception et réalisation de composants de puissance à superjonction et à tranchées profondes pour des applications 600 V et 1200 V. Electronique. Université Paul Sabatier - Toulouse III, 2016. Français. 〈NNT : 2016TOU30230〉. 〈tel-01451021v2〉

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