| AVS 64th International Symposium & Exhibition | |
| Thin Films Division | Tuesday Sessions |
| Session TF-TuM |
| Session: | Advanced CVD and ALD Processing, ALD Manufacturing and Spatial-ALD |
| Presenter: | Laurent Souqui, Linköping University, Sweden |
| Authors: | L. Souqui, Linköping University, Sweden H. Pedersen, Linköping University, Sweden H. Högberg, Linköping University, Sweden |
| Correspondent: | Click to Email |
Boron nitride (BN) is a wide bandgap semiconductor related to the other 13-nitrides (or III-nitrides), aluminium nitride (AlN) or gallium nitride (GaN). As BN is isoelectronic to carbon, it demonstrates graphite-like structure (sp2-BN) in hexagonal BN(h-BN) and rhombohedral BN, (r-BN). In addition, BN exists as disordered phases such as amorphous (a-BN) or turbostratic (t-BN). Crystalline h-BN and r-BN films are promising materials for application such as UV-devices, power electronics and neutron detectors. Furthermore the similarities between graphene and sp2-phases such as h-BN and r-BN make BN a commensurate insulating growth template for graphene.
Our previous works were focused on the CVD of epitaxial sp2-BN films on Al2O3(0001) and 6H-SiC(0001) substrates [1] and found the optimal condition for BN growth to be around 1500°C. We now study the growth of boron nitride on silicon substrates (Si) as silicon is cheap, abundant and is a mature technology. However, due to its low melting point (1414°C), Si cannot withstand such high temperature processes. Because of the necessity of growing at lower temperature, CVD BN films grown on silicon usually show low crystallinity i.e. often a-BN, t-BN or nano-crystalline BN.
In this work, thin BN films were grown on Si(111) substrates in a horizontal hot-wall CVD reactor. Triethylborane (TEB) and ammonia (NH3) were used as precursors and reacted at temperatures between 1200°C and 1300°C. The substrates were in-situ annealed in silane (SiH4) and NH3 before the deposition. Further, a small fraction of SiH4 was also introduced during the growth as this has been shown to favour growth of crystalline sp2-BN films [2]. Fourier-Transform Infra-Red spectroscopy (FTIR) confirms the presence of sp2-BN. Adjustment of the SiH4 concentration in the growth flux results in the deposition of crystalline films attributed to sp2-BN in X-ray diffraction. In contrast, films deposited on Si at the same conditions but without SiH4/NH3 pre-treatment hardly nucleates and is amorphous to X-rays. This shows the importance of surface preparation in order to grow crystalline BN films on Si. In addition to growth of boron nitride, we observe the growth of SiC grains either due to a reaction between alkyl by-products from TEB and either the substrate or SiH4 from the gas phase.
[1] M. Chubarov, H. Pedersen, H. Högberg, J. Jensen and A. Henry, Cryst. Growth Des. 2012, 12, 3215.
[2] M. Chubarov, H. Pedersen, H. Högberg and A. Henry, CrystEngComm, 2013, 15, 455.