Thermal reaction of polycrystalline AlN with XeF2

Abstract

Articles you may be interested inComprehensive surface analysis of GaN-capped AlGaN/GaN high electron mobility transistors: Influence of growth method J. Appl. Phys. 110, 083527 (2011); 10.1063/1.3653825 AlGaAs/InGaAs metal-oxide-semiconductor pseudomorphic high-electron-mobility transistor with low temperature liquid phase deposited Al 2 O 3 gate insulator Low coverage spontaneous etching and hyperthermal desorption of aluminum chlorides from Cl 2 / Al (111) J. Chem. Phys. 121, 9018 (2004); 10.1063/1.1805495 Selected energy epitaxial deposition of GaN and AlN on SiC(0001) using seeded supersonic free jets of NH 3 in helium J.Detailed studies on the thermal reaction behavior of polycrystalline aluminum nitride ͑AlN͒ with effusive xenon difluoride ͑XeF 2 ͒ have been carried out over the sample temperature ͑T s ͒ range from 300 to 920 K using molecular beam mass spectrometry combined with a time-of-flight technique and ex situ surface analyses, i.e., X-ray photoelectron spectroscopy, Auger electron spectroscopy, and scanning electron microscopy ͑SEM͒. The species desorbed from the AlN / XeF 2 system were monitored using molecular beam mass spectrometry, as a function of sample temperature. Above T s = 800 K, the desorbed reaction products were identified as N 2 and AlF 3 , and their flux intensities increase monotonically as the sample temperature is increased. The flux intensity of XeF 2 desorbed after physisorption to the AlN surface is found to decrease as T s is raised above T s = 800 K, and approximately one half of the incoming XeF 2 is consumed by the thermal reaction at 920 K. The results of surface analyses show that the thermal reaction of AlN with XeF 2 starts at approximately T s = 700 K, forming a reaction layer composed of AlF 3 . The AlF 3 layer becomes thick as T s is increased from T s = 700-800 K. Above T s = 800 K, however, as a result of fast desorption of AlF 3 and F atoms from the AlF 3 layer, only partially fluorinated AlF x ͑x = 1 and/or 2͒ layers are formed and the bulk AlN is revealed again. The SEM photographs indicate that the surfaces exposed above T s = 850 K are strongly etched but a slight change is observed at T s ഛ 800 K. On the basis of these results, three reaction stages are proposed for the AlN / XeF 2 reaction depending on the sample temperature range: Stage 1 ͑300ഛ T s Ͻ 700 K͒; no reaction, stage 2 ͑700ഛ T s Ͻ 800 K͒; surface fluorination, and stage 3 ͑800ഛ T s ͒; etching. At stage 3, AlF 3 formed on the surface starts to evaporate and fast etching proceeds, since the vapor pressure of AlF 3 is high enough in this temperature range.