Dependence of crystal structure and work function of WNx films on the nitrogen content

Abstract

The effect of nitrogen content on crystal structure ͑phase and grain size͒ and work function ͑⌽ m ͒ of WN x films is investigated. The ⌽ m of WN x films is extracted from the plot of flatband voltage versus SiO 2 thickness. For W and WN 0.4 films, the ⌽ m are 4.67 and 4.39 V, and their crystal phases are both body-centered-cubic W. For WN 0.6 film, it contains W + W 2 N mixed phases and the ⌽ m is 4.50 V. On the other hand, the ⌽ m of WN 0.8 and WN 1.5 films are 5.01 and 4.49 V, and their crystal phases are both face-centered-cubic W 2 N. The grain size of W and W 2 N phases decreases with the increase of the nitrogen content in WN x. It is concluded that the ⌽ m is affected by the crystal phase as well as the grain size of WN x film.

Enhancement of the Schottky Barrier Height using a Nitrogen-Rich Tungsten Nitride Thin Film for the Schottky Contacts on AlGaN/GaN Heterostructures

“…From the work function measurement, the value increases as the nitrogen is further incorporated. Contrary to the report by Jiang et al, 11 the grain size and phase were similar and did not contribute to the change of the work function. Thus, it is suggested that the change of the work function in the W 2 N film was due to the excessive nitrogen content of the film which caused compositional change and the lattice parameter expansion.…”

“…Furthermore, recent studies on WN x showed a variable work function, possibly influenced by either different nitrogen content in the film 10 or by the change of phase and grain size. 11 These issues have not been fully addressed in the previous studies but could contribute to different values of the Schottky barrier height and alter the electrical characteristics of the diodes.…”

Physical characterization of sputter-deposited amorphous tungsten oxynitride thin films

“…The focus of the present work is the synthesis and physical characterization of tungsten oxynitride films. Tungsten nitrides have been widely studied for their use as diffusion barriers in microelectronics [18][19][20], gate electrodes in semiconductor devices [21,22], hard coatings to protect from mechanical wear [23][24][25], or as Schottky contacts [27]. Several of the early studies have contributed extensively towards the understanding of W-N system, especially the knowledge of fundamental relationship between different parameters, such as deposition conditions and their effect on the internal stress, microstructure, and elemental concentration [18][19][20][21][22][23][24][25][26][27][28][29][30][31].…”

Low Temperature Deposition of WNxCyDiffusion Barriers Using WN(NEt2)3as a Single-Source Precursor

“…Due to their low resistivity, appropriate work function, and thermal stability, refractory metal nitrides have been proposed for a number of applications, ranging from wafer level hermetic sealing 1 to field effect transistor (FET) gate electrodes. 2 In particular, the tungsten-based materials WN x and WN x C y have been considered as an alternative for both diffusion barriers 3,4 and gate electrodes 5 due to their low resistivity, appropriate and tunable work function (4.39-5.01 eV 6 ), thermal and mechanical stability, good barrier performance, and processing simplicity. 7,8 Depositions of WN x and WN x C y typically use ammonia and WCl 6 , WF 6 or W(CO) 6 as co-reactants.…”

“…2 In particular, the tungsten-based materials WN x and WN x C y have been considered as an alternative for both diffusion barriers 3,4 and gate electrodes 5 due to their low resistivity, appropriate and tunable work function (4.39-5.01 eV 6 ), thermal and mechanical stability, good barrier performance, and processing simplicity. 7,8 Depositions of WN x and WN x C y typically use ammonia and WCl 6 , WF 6 or W(CO) 6 as co-reactants. 4,[9][10][11][12] Despite being volatile, simple, and cost-effective, these chemistries generally require high deposition temperature, can introduce impurities, and can yield corrosive byproducts.…”