Low-temperature plasma-assisted growth of optically transparent, highly oriented nanocrystalline AlN

Abstract

Optically transparent, highly oriented nanocrystalline AlN(002) films have been synthesized using a hybrid plasma enhanced chemical vapor deposition and plasma-assisted radio frequency (rf) magnetron sputtering process in reactive Ar+N2 and Ar+N2+H2 gas mixtures at a low Si(111)/glass substrate temperature of 350 °C. The process conditions, such as the sputtering pressure, rf power, substrate temperature, and N2 concentration were optimized to achieve the desired structural, compositional, and optical characteristics. X-ray diffractometry reveals the formation of highly c-oriented AlN films at a sputtering pressure of 0.8 Pa. Field emission scanning electron microscopy suggests the uniform distribution of AlN grains over large surface areas and also the existence of highly oriented in the (002) direction columnar structures of a typical length ∼100−500 nm with an aspect ratio of ∼7−15. X-ray photoelectron and energy dispersive x-ray spectroscopy suggest that films deposited at a rf power of 400 W feature a chemically pure and near stoichiometric AlN. The bonding states of the AlN films have been confirmed by Raman and Fourier transform infrared spectroscopy showing strong E2 (high) and E1 transverse optical phonon modes. Hydrogenated AlN films feature an excellent optical transmittance of ∼80% in the visible region of the spectrum, promising for advanced optical applications.

Self-limiting low-temperature growth of crystalline AlN thin films by plasma-enhanced atomic layer deposition

“…Metal-organic chemical vapor deposition (MOCVD) [16], molecular beam epitaxy (MBE) [17], pulsed laser deposition [18], and sputtering [19] are the most common techniques employed for the growth of AlN. Although MOCVD offers the most efficient process due to its ability to deposit high quality materials with significant growth rates, deposition of AlN requires high temperatures (>1000°C) [16].…”

The influence of N2/H2 and ammonia N source materials on optical and structural properties of AlN films grown by plasma enhanced atomic layer deposition

“…Moreover, AlN can be a good template for the fabrication of short wavelength emitters and detectors owing to its thermal stability and high thermal conductivity. As a result of these properties, a significant amount of effort has been devoted towards the synthesis of epitaxial, polycrystalline, and amorphous grade AlN thin films [1,[4][5][6][7]. While high-temperature grown epitaxial AlN films are used in active electronic and opto-electronic device layers, polycrystalline and amorphous AlN films grown at CMOS-compatible temperatures are widely used as dielectrics and passivation layers for microelectronic devices [8,9].…”

Low-temperature growth of stoichiometric aluminum nitride films prepared by magnetic-filtered cathodic arc ion plating

“…Highly pure stoichiometric AlN films with c-axis orientation could be fabricated by chemical vapor deposition (CVD) [1,3,4], yet the high deposition temperature and toxic exhaust emission form its main disadvantages. Reactive magnetron sputtering [5][6][7][8] is a preferred choice because of its low deposition temperature (about 200-500°C). However, direct current (DC) reactive sputtering suffers from the hysteresis behavior [9], and radio frequency (RF) reactive sputtering has disadvantage of low deposition rate [5,10].…”