Controlled polarity of sputter-deposited aluminum nitride on metals observed by aberration corrected scanning transmission electron microscopy

Harumoto, Takashi; Sannomiya, Takumi; Matsukawa, Yasuko; Muraishi, Shinji; Shi, Ji; Nakamura, Yoshio; Sawada, Hidetaka; Tanaka, Takayuki; Tanishiro, Y.; Takayanagi, Kunio

doi:10.1063/1.4792942

Cited by 24 publications

(21 citation statements)

References 44 publications

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“…AlN was deposited from a gun with an Al target and metallic Pt from another gun with a Pt target. Details of the deposition conditions were given in our previous report (Harumoto et al, 2013). It should be noted that a small number of nitrogen atoms are incorporated into the Pt lattice when the Pt film is deposited under Ar-N 2 atmosphere.…”

Section: Specimen Preparationmentioning

confidence: 99%

Rhombohedral distortion analysis of ultra-thin Pt(111) films deposited under Ar–N₂atmosphere

et al. 2014

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A rhombohedral analysis method for analysing the lattice distortion in a (111)‐textured face‐centred cubic film under rotationally symmetric stress is proposed. Because no material constants, such as diffraction elastic constants, are required, the expressions of the distortion, namely the angle and the lattice parameter, are universal and can be readily used to compare different films. Using this rhombohedral distortion analysis method, (111)‐textured Pt films deposited under argon–nitrogen atmosphere are systematically investigated, and the thickness‐dependent lattice deformation in as‐deposited and annealed films is described by the two geometrical parameters of the rhombohedral cell.

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Section: Specimen Preparationmentioning

confidence: 99%

Rhombohedral distortion analysis of ultra-thin Pt(111) films deposited under Ar–N₂atmosphere

et al. 2014

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“…In addition, it is reported that the polarity distribution of the piezoelectric film has a strong impact on the etch behavior. 16,21 Bulk AlN which shows N-polarity is etched faster in a wet-chemical etching solution (KOH, H3PO4) than AlN with Al-polarity. 14 The considerable lower |d33| values of the AlN synthesized on Ti films support the assumption of a mixed Al-and N-polarity of the layer.…”

Section: Resultsmentioning

confidence: 99%

Impact of titanium layer and silicon substrate properties on the microstructure of c-axis oriented AlN thin films

2015

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Highly c-axis orientated sputter deposited aluminium nitride (AlN) thin films are widely used as piezoelectric layers in micro-electro-mechanical systems (MEMS). Therefore, stable and reliable deposition and patterning of the AlN thin films in the fabrication process of such devices is of utmost importance. In this work, we study the wet chemical etching behavior of highly c-axis oriented AlN layers as well as the film-related residuals after the etching procedure. To investigate the impact of the underlying material on the quality of the AlN films they are either deposited on pure silicon (Si) substrates or on Si substrates covered with a sputter-deposited thin titanium (Ti) film. The 620 nm thin AlN layers are synthesized simultaneously onto both substrate types and subsequently wet-chemical etched in a phosphorous acid based etching solution at a temperature of 80°C. We demonstrate a significant difference in surface roughness of the untreated AlN films when sputter-deposited on Ti or pure Si. Furthermore, we analyze the piezoelectric properties of the deposited films. Although the XRD analyses indicate a high c-axis orientated wurtzite structure for all deposited films, the absolute value of the piezoelectric coefficients |d33| of AlN thin films synthesized on Ti are 0.4-4.3 pC/N, whereas corresponding values of 5.2-6 pC/N are determined at those deposited on pure Si substrates,. Finally, after wet chemically etching a porous, but homogeneous AlN microstructure is observed for samples synthesized onto Ti layers, whereas AlN layers deposited directly on Si substrate are either etched very inhomogenously or almost completely with some etch resistant pyramidal-shaped residues. This might be due to a local change in polarity within the AlN layer.

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“…These nanoscale voids could be the result of the incomplete coalescence of the nucleation islands. Literatures proposed that a few monolayers of Al were deposited on the sapphire's surface [29,30] and formed the nucleation islands before NH3 came into the reaction chamber, creating a quasi-threedimensional (quasi 3D) growth mode at the beginning of the growth. Later, the high-temperature AlN began to grow on these quasi-3D islands, which was followed by the islands' coalescing and finally the growth transferred to a 2D mechanism.…”

Section: Resultsmentioning

confidence: 99%

Structural properties, crystal quality and growth modes of MOCVD-grown AlN with TMAl pretreatment of sapphire substrate

Sun

Tahtamouni

et al. 2017

J. Phys. D: Appl. Phys.

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The growth of high quality AlN epitaxial films relies on precise control of the initial growth stages. In this work, we examined the influence of the trimethylaluminum (TMAl) pretreatment of sapphire substrates on the structural properties, crystal quality and growth modes of heteroepitaxial AlN films on (0001) sapphire substrates. Without the pretreatment, the AlN films nucleated on the smooth surface but exhibited mixed crystallographic Al-(N-) polarity, resulting in rough AlN film surfaces. With increasing the pretreatment time from 1 to 5 s, the N-polarity started to be impeded. However, small islands were formed on sapphire surface due to the decompostion of TMAl. As a result, small voids became noticeable at the nucleation layer (NL) because the growth started as quasi three-dimensional (3D) but transformed to 2D mode as the film grew thicker and got coalesced, leading to smoother and Al-polar films. On the other hand, longer pretreatment time of 40 s formed large 3D islands on sapphire, and thus initiated a 3D-growth mode of the AlN film, generating Al-polar AlN nanocolumns with different facets, which resulted into rougher film surfaces. The epitaxial growth modes and their correlation with the AlN film crystal quality under different TMAl pretreatments are also discussed.

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Controlled polarity of sputter-deposited aluminum nitride on metals observed by aberration corrected scanning transmission electron microscopy

Cited by 24 publications

References 44 publications

Rhombohedral distortion analysis of ultra-thin Pt(111) films deposited under Ar–N₂atmosphere

Rhombohedral distortion analysis of ultra-thin Pt(111) films deposited under Ar–N₂atmosphere

Impact of titanium layer and silicon substrate properties on the microstructure of c-axis oriented AlN thin films

Structural properties, crystal quality and growth modes of MOCVD-grown AlN with TMAl pretreatment of sapphire substrate

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Controlled polarity of sputter-deposited aluminum nitride on metals observed by aberration corrected scanning transmission electron microscopy

Cited by 24 publications

References 44 publications

Rhombohedral distortion analysis of ultra-thin Pt(111) films deposited under Ar–N2atmosphere

Rhombohedral distortion analysis of ultra-thin Pt(111) films deposited under Ar–N2atmosphere

Impact of titanium layer and silicon substrate properties on the microstructure of c-axis oriented AlN thin films

Structural properties, crystal quality and growth modes of MOCVD-grown AlN with TMAl pretreatment of sapphire substrate

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Rhombohedral distortion analysis of ultra-thin Pt(111) films deposited under Ar–N₂atmosphere

Rhombohedral distortion analysis of ultra-thin Pt(111) films deposited under Ar–N₂atmosphere