Impact of sputter deposition parameters on molybdenum nitride thin film properties

Abstract

Molybdenum and molybdenum nitride thin films are presented, which are deposited by reactive dc magnetron sputtering. The influence of deposition parameters, especially the amount of nitrogen during film synthesization, to mechanical and electrical properties is investigated. The crystallographic phase and lattice constants are determined by x-ray diffraction analyses. Further information on the microstructure as well as on the biaxial film stress are gained from techniques such as transmission electron microscopy, scanning electron microscopy and the wafer bow. Furthermore, the film resistivity and the temperature coefficient of resistance are measured by the van der Pauw technique starting from room temperature up to 300 °C. Independent of the investigated physical quantity, a dominant dependence on the sputtering gas nitrogen content is observed compared to other deposition parameters such as the plasma power or the sputtering gas pressure in the deposition chamber.

Molybdenum Nitride Films: Crystal Structures, Synthesis, Mechanical, Electrical and Some Other Properties

“…In a very recent paper, Stöber et al [32] have reported results quite consistent with the previous work. The molybdenum nitride films about 150 nm thick are deposited by reactive dc magnetron sputtering at power ranging from 300 to 700 W and a total pressure ranging from 2 to 8 × 10…”

“…Stöber et al [32] have also reported an increase of the resistivity of Mo2N films with increasing nitrogen fraction in (Ar-N2) gas mixtures. The resistivity of Mo2N films deposited at 20% of nitrogen fraction, a pressure of 500 W and a total pressure of 8 × 10…”

“…Among all molybdenum nitride phases, γ-Mo2N can be synthesized over a large range of nitrogen pressure from some thousandths of Pascal in (Ar-N2) gas mixture [29] to dozens of Pascal in pure N2 gas [25,40]. Hence, depending on the range of pressure, an increase of pressure leads to contrasting results: A transition from γ-Mo2N to stoichiometric MoN phases occurs at large nitrogen partial pressure in (Ar-N2) gas mixture [40] or in pure N2 gas [25,40], whereas transitions from randomly oriented crystallites to oriented crystallites [29] or amorphous structures [31,32] occur at low nitrogen partial pressure. Such phenomena are related to an excess of nitrogen in the lattice and/or the occurrence of stresses during the film growth and so, discrepancies in the values of lattice parameters corresponding to γ-Mo2N are clearly seen in Table 1 compared with the bulk and theoretical values.…”

“…Stöber et al [32] have shown that a minimum film stress of −60 MPa is measured in Mo2N films produced with N2 fraction in (Ar-N2) gas mixture of 20% in a reactive dc magnetron sputtering process. The compressive stress increases with increasing nitrogen fraction up to a value of −4 GPa, which leads to adhesion problems and delamination due to an excess of nitrogen in the structure.…”

Correlation between mechanical and microstructural properties of molybdenum nitride thin films deposited on silicon by reactive R.F. magnetron discharge

“…On the other hand, Stöber et al reported that at 50% nitrogen content the Mo-N thin form crystallite sizes of 6.4 nm and a more pronounced texture of the γ-Mo 2 N structure [34]. Saito and Asada have reported a phase change from the cubic γ-Mo 2 N to a B1-type MoN by increasing the N 2 + ions implanted in sputtered Mo thin films at room temperature [35].…”