Effect of NH3 thermal treatment on an atomic layer deposited on tungsten films and formation of W–B–N

Abstract

The effect of ammonia (NH 3 ) ambient annealing on a tungsten ͑W͒ film deposited by atomic layer deposition at temperatures ranging from 400-700°C is discussed. The as-deposited film contains approximately 20 at. % of boron which is chemical bound to W ͑W-B͒ having a resistivity of 128 ⍀ cm. The film has an amorphous structure, which does not transform into crystalline phase during annealing. As a result of annealing in NH 3 ambient, a tungsten ternary phase ͑W-B-N͒ forms at the surface; its binding configuration depends on the annealing temperature. Below 500°C, nitrogen is chemically bonded to tungsten ͑W-N͒ while maintaining a W-B bond. Above 600°C, nitrogen-rich W-B-N forms, in which nitrogen atoms have chemical binding with boron ͑B-N͒ and tungsten ͑W-N͒. It was found that a film annealed at higher temperatures has a resistivity of 107 ⍀ cm, and thermal desorption of boron and nitrogen containing species is not observed during the thermal process. In addition, tungsten oxide formed at the surface during exposure to air is reduced during the NH 3 annealing process. X-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, and thermal desorption spectroscopy were used for film characterization.

Dependence of Gate Interfacial Resistance on the Formation of Insulative Boron–Nitride for p-Channel Metal–Oxide–Semiconductor Field-Effect Transistor in Tungsten Dual Polygate Memory Devices

“…During postdeposition thermal treatment, nitrogen in the WN layer could easily be out-diffused 19,20) in regions where the B-N compound reaction could take place. 21,22) The change in Gibbs free energy 23) during the formation of B-N is as large as À225 kJ/mol, which is higher than that of Si-N (À216 kJ/mol). This stable insulative B-N interlayer could lead to an increase in gate R c .…”

W-B-N sputter-deposited thin films for mechanical application

“…Compared to sputtered Ti-B-N coatings, little research work has been carried out on the W-B-N system. The few exploratory investigations [5][6][7][8] showed that this ternary system is an excellent diffusion barrier, due to a dense amorphous structure, relatively high crystallisation temperature and chemical inertness.…”