Formation of inter-device isolation in gallium nitride heterostructures on silicon

Various methods of forming inter-device insulation on AlGaN/AlN/GaN heterostructures grown on silicon substrates are considered. Methods of isolation using nitrogen (N+) ion implantation technology and isolation of devices by mesa etching are shown. To assess the resistivity on the surface of AlGaN/AlN/GaN, test structures with ohmic contacts separated by a semiconductor with known dimensions were made. The ohmic contacts were formed by electron-beam sputtering of the Ti/Al/Ni/Au metal system. Mesa insulation was formed by reactive ion etching on a plant equipped with an inductively coupled plasma source in a chlorine-containing medium based on a Cl2/BCl3/Ar gas mixture. The etching was carried out at a power of an inductively coupled plasma source of 40 W and a high-frequency power of 80 W through a photoresist mask. The specific surface resistance after mesa etching was 5.5•108ohms/sec. However, there are disadvantages of the mesa etching process associated with ion bombarding of the surfaces and the profile of the side walls. An alternative method of manufacturing inter-device insulation is ion implantation. The technology of planar ion implantation avoids the contact of the gate with a layer of two-dimensional electron gas on the side walls of the mesa, which leads to stable operation of the device. Nitrogen ions (N+) were selected as an implantable impurity for the formation of inter-device isolation by ion implantation. The dose dependences of the specific surface resistance of the inter-device insulation have been investigated. The modes of ion implantation have been established: the energy of the introduced ions is 125 keV, low doses are 3 • 1013 cm-2, the implantation is carried out without the presence of protective dielectric coatings. The insulation resistance obtained by the method of ion implantation of nitrogen N+, when exposed to temperatures in the range from 250 to 350 °C, has consistently high values.

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