Controlled Growth of Conductive AlN Thin Films by Plasma-Assisted Reactive Evaporation
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ny outstanding properties such as wide band gap energy (6.2 eV), excellent chemical stability, high hardness, high thermal conductivity, high volume resistivity, and low dielectric constant.[1,2] AlN thin films are intensively studied as a potential material for many applications including bulk acoustic wave and surface acoustic wave devices, deep ultraviolet (UV) light-emitting diodes, laser diodes, field emission displays, and thermoelectric devices.[3,4] Recently, AlN was widely used in semiconductor manufacturing equipment, such as plasma etchers and electrostatic chucks, due to its significant plasma resistance, high thermal expansion coefficients, and thermal conductivity, which are similar to those of silicon and, therefore, are favorable for silicon-based applications.[5,6] However, due to the intrinsically insulating nature of AlN and its excellent ability for accumulation of static electricity, the
M. ALIZADEH is with the UM Power Energy Dedicated Advanced Centre (UMPEDAC), Level 4 Wisma R&D, University of Malaya, Jalan Pantai Baharu, 59990 Kuala Lumpur, Malaysia, and also with Low Dimensional Materials Research Centre (LDMRC), Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia. Contact e-mail: [email protected] B.T. GOH and S.A. RAHMAN are with the LDMRC, Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur. Manuscript submitted 22 November 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
discharge of static electricity causes silicon wafer damage.[6] To inhibit discharge of static electricity, AlN must exhibit an electrical conductivity (more than 105 s cm1).[6] It was shown that AlN with a conductivity between 1011 and 107 s cm1 can be used as an electrostatic chuck for the silicon wafers.[7] Furthermore, conductive AlN films were applied for nonvolatile memory devices, adjusting solar absorption of a surface built up and serving as the cathode electron emission materials for surface-conduction electron-emitter displays.[8–12] The distribution of Al particles in the AlN structure could induce the current conduction in AlN, though pure AlN possesses a low conductivity due to its wide band gap (6.2 eV). Also, it was reported that compositionally gradient conductive–insulative AlN films can lead to a much larger thermal conductivity and a higher resistance against thermal stress.[13] However, high participation of the metallic particles in the deposited films degrades transparency and electrical resistivity of AlN thin films. In addition, it was shown that stresses due to overincorporation of aluminum particles shorten the life of AlN thin films and deteriorate the performance of the aforementioned devices.[14] To avoid such problems, a precise control on the composition of the deposited films must be taken account via optimizing the parameters in the growth process. Wu et al.[15] and Shukla and Khare[16] showed that the metallic composition of AlN films deposited by pulsed laser deposition is significantly decreased when the depo
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