Temperature-Dependent Strain-stress Characterization in GaN (Gallium Nitride) Thin Films
The stress induced in thin films of GaN at elevated temperatures is studied by in-situ XRD. The internal stress is determined during temperature cycling and a change from tensile to compres-sive stress is observed. The effect of the mismatch of thermal properties between film and sub-strate is shown to determine the stress relaxation behavior.
Internal strain-stress fields in thin deposits can decisively influence mechanical behavior and can significantly modify some important electronic characteristics of microelectronic structures (e.g. bandgap of semiconductors). The understanding of origin and the characterization of strain-stress fields in thin films represents therefore a very important issue within microelectronic technology (1). Mechanical and ther-mal phenomena are, however, among the least understood and most complex phenomena encountered in microelectronic systems. Investigations of strains and stresses at elevated temperatures can therefore bring relevant insight into the understanding of strain-stress fields, their origin and contributing phenomena. In this report residual stresses in GaN/Al2O3 (0001) structures prepared by three different methods are studied using X-ray diffraction at elevated temperatures. Gallium nitride is a widely used semiconductor mostly applied in blue light-emitting devices. This study was performed with the DHS 1100 heating attachment by Anton Paar which offers the possibility to evaluate residual stresses and unstressed lattice parameters in the thin films at elevated temperature.
1. J.H. Lau, Thermal stress and strain in microelectronic packaging, ITP, New York, 1993.
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