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19 August 2005 Hafnium oxide for optical applications deposited by different CMOS compatible methods
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Hafnium oxide is a promising candidate for electronic applications. It also offers interesting properties for a wide variety of optical applications as antireflective coatings, dielectric mirrors or protective coatings. Besides favorable optical properties, the mechanical stability and chemical inertness of hafnium oxide offers further advantages. Microelectronics require ultra thin layers in the 3-5nm range for gate dielectrics. For optical applications a wider range is necessary. As optical coatings should be capable to be integrated in a CMOS or MEMS technology, only compatible deposition processes can be used. In this presentation we report on atomic layer deposition (ALD) for thicknesses in the 2-30nm range and r.f. sputtering from 30 to above 150nm. Thus almost every wavelength from EUV to NIR can be covered for λ/4 applications, keeping in mind, that the refractive index is 2.1 at 586nm. Deposition took place on 2x2 cm2 silicon substrates for ALD and on 150mm silicon wafers for sputtering each either HF etched of thermally oxidized. The layers have been analyzed by AFM, XPS, XRD, TEM to gather information about morphology, composition, bonding and structural properties. Optical properties have been evaluated by ellipsometry. The different deposition methods are compared as well as the effects of thermal annealing after deposition. All layers are very smooth and reveal optical properties close to bulk HfO2. As deposited the layers are predominately amorphous, thermal annealing leads to crystallization.
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Matthias Albert, Thorsten Roessler, Barbara Adolphi, Johann W. Bartha, Heinrich Grueger, Christian Kunath, and Stephan Sorge "Hafnium oxide for optical applications deposited by different CMOS compatible methods", Proc. SPIE 5870, Advances in Thin-Film Coatings for Optical Applications II, 58700M (19 August 2005);

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