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High Power Pulsed Optimized Plasma Process for the deposition of highly insulating large band gap nitrides (AlN, BN) – HIPPOPP

Submission summary

Devices made with wide bandgap semiconductors are able to work at elevated temperature and aggressive environments. Among the wide band gap semiconductors family, the III-V family provides interesting candidates as GaN, AlN and c-BN. Gallium nitride has extensive applications in large sphere of life. Both AlN and BN have a much larger band gap than GaN that confers to them other applications in environmental, military and solar applications like UV astronomy, lithography systems, UV radiation dosimetry, pollution monitoring. Furthermore, AlN and c-BN are a promising materials for Surface acoustic wave (SAW) and bulk acoustic wave (BAW) electro-acoustic devices. Nowadays, these devices are widely used in a variety of applications both in consumer electronics as well as in specialized scientific and military equipment. Epitaxial growth of AlN has already been achieved by CVD or reactive MBE at temperature higher than 1000°C but in the case of c-BN no deposition was reported by these techniques even at high temperature). In order to reduce drastically the deposition temperature and obtain the cubic phase, Physical Vapor Deposition (PVD) methods which use ion assistance were involved. Nevertheless, this high level of ion bombardment has some drawbacks: bad crystalline quality, high level of stress, bad adhesion which inhibits the deposition of thick films. The principal objective of this project is to synthesize thick, oriented, stress free AlN and c-BN films with good crystalline quality at temperature down to 400°C by High Power Pulsed Magnetron Sputtering method (HPPMS). This new and very promising PVD process based on pulsed magnetron sputtering at high level of power has shown to modify the intrinsic plasma parameters, which, in turn may have a strong influence on film structure and properties. In fact, for a few tens of µs a high target current density (several A/cm2) sustains very dense plasma near the cathode which induces efficient sputtered vapour ionisation. This method was limited by a relative high probability of arc development, self sputtering, loss of deposition rate,... Nevertheless, one of the partners, namely LPGP, recently developed a novel technique of HPPMS by using a fast pulsed-magnetron discharge operating in a preionization regime. This technique allows faster current growth, higher current density on the target, high ion-to-neutral flux ratio at the substrate, arc-free regime, and good stability with very large instantaneous power. At the same time, the arc development is greatly reduced when using short pulses. Moreover they demonstrated large pressure range operation (3-300 mTorr) capability of a HPPMS process. By ensuring the thermalization of energetic particles through neutral-neutral and ion-neutral collisions, it permits an easier control of the power transferred to the depositing film compatible with low thermal budget operation and in particular the reduction the destructive effect on the substrate and the growing film by the fast neutrals reflected on the cathode. The challenge of the present project is to use HPPMS for the synthesis of complicated films as AlN and c-BN at low temperature by HPPMS. Potentialities of this technique were initially demonstrated for the deposition of metallic films and, recently, are being explored for conducting oxides by using reactive plasma conditions. But until now, this process has not been involved for insulating material in a reactive gas as nitrogen, and thus an adaptation of the whole process including the pulsed power supply is necessary. This objective is the first challenge of our project. After overcoming this first step, we will explore the set of plasma conditions which can be used for the deposition of first AlN films and second c-BN ones. This phase implies an interaction between the team concerned by the discharge engineering, including modelling and diagnostics of the transient plasma because the physics' of such a kind of discharge is not known at all, the specialists of the synthesis and characterizations of thin films and the specialists of their application. Thanks to their complementarity's, the close collaboration and synergy between the three partners makes possible a complete physico-chemical, structural and electrical characterization of the deposited films and their full optimisation through a better knowledge and control of the synthesis process, i.e. transfer of the HPPMS deposition method for nitrides films deposition. The last objective will be to test the films performances for challenging and promising applications and to validate the functional properties of the synthesized material. Thanks to the microelectronic facilities of IEMN three demonstrators, UV/VUV/EUV detectors, SAW microwave devices and c-BN passivated transistor will be realized and tested. The realization of such a kind of demonstrators may certainly have an impressive impact from the economical point of view.

Project coordination

Abdou DJOUADI (Organisme de recherche)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

Help of the ANR 330,000 euros
Beginning and duration of the scientific project: - 36 Months

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