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- Engelmark, Fredrik
(författare)
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AlN and High-k Thin Films for IC and Electroacoustic Applications
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Further, a highly selective dry etch process for etching Al on AlN has been developed for the fabrication of MIM, MIS, SAW and BAW test structures for electrical and electroacoustic characterization of the films. A dielectric constant of 10 for AlN and 25 for Ti doped Ta2O5 have been measured. With respect to electroacoustic characterization, BAW measurements gave a longitudinal velocity of 11350 m/s and a TCD of -25ppm/K. AlN thin film test structures on SiO2/Si yielded a SAW velocity of around 5000 m/s, while those on polycrystalline diamond exhibited a SAW velocity of 11800 m/s. The latter results illustrate one of the biggest advantages of thin film SAW technology, namely one can exploit both the piezoelectric properties of the film and the acoustic properties of the substrate and hence devise components with superior performance. The explosive development of personal communications systems, navigation, satellite communications as well as personal computer and data processing systems together with the constant demand for higher speeds and larger bandwidths has driven the fabrication technology to its limits. This in turn necessitates the development of novel functional materials for the fabrication of devices with superior performance and higher capacity at reduced manufacturing costs. This thesis focuses on the synthesis and characterization of such materials for IC and electroacoustic applications. Specifically, AlN thin films as well as Ti doped Ta2O5 thin films have been grown using both RF and pulsed-DC reactive sputter deposition on a variety of substrate materials. AlN is a piezoelectric material and hence its crystallographic structure and film texture are of prime interest, while Ta2O5 is a material with a relatively high dielectric constant. A significant part of the work deals with the optimization of the deposition processes. The latter have been optimized both empirically and theoretically by modeling the reactive sputter process. Subsequently, highly textured AlN thin films have been synthesized and characterized. The films were fully c-axis oriented with a typical value for the FWHM of the (002) rocking curve of 1.6°. In addition, epitaxial AlN films have been grown on sapphire at 500oC with relatively low defect density.
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- Madsen, Lynette D, et al.
(författare)
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Texture of Al thin films deposited by magnetron sputtering onto epitaxial W(001)
- 2000
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 87:1, s. 168-171
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Tidskriftsartikel (refereegranskat)abstract
- Highly textured epitaxial metallizations will be required for the next generation of devices with the main driving force being a reduction in electromigration. Herein a model system of 190 nm of Al on a 140 nm layer of W grown on MgO less than 00l greater than substrates was studied. The W layer was less than 00l greater than oriented and rotated 45 degrees with respect to the MgO substrate to minimize the misfit; the remaining strain was accommodated by dislocations, evident in transmission electron microscopy images. From high-resolution x-ray diffraction (XRD) measurements, the out-of-plane lattice parameter was determined to be 3.175 Angstrom, and the in-plane parameter was 3.153 Angstrom, i.e., the W film sustained a strain resulting in a tetragonal distortion of the lattice. XRD pole figures showed that the Al had four fold symmetry and two dominant orientations, less than 016 greater than and less than 3 9 11 greater than, which were twinned with multiple placements on the epitaxial W layer. The driving force for the tilted less than 001 greater than and less than 011 greater than orientations of Al on W is due to strain minimization through lattice matching. These results show that less than 00l greater than Al deposited at ambient conditions onto W is difficult to achieve and implies that electromigration difficulties are inherent.
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