Expanding Plasma Process for Nitriding Mo–Ti Bilayer Thin Films

Abstract

Owing to the reducing effect of NHx radicals and H species produced in (Ar-N2-H2) expanding plasma, chemical reactions are promoted in thin metal films in contrast with other plasma treatments where the impinging energetic ions play the main role. Multi layers of Mo, Ti, and their nitrides are used in very recent applications such as supercapacitors or solar cells. They combine the interesting properties of the constituents. This work reports on the formation and the structure of Ti nitrides and Mo silicides in Mo–Ti bilayer films coated on Si wafers exposed to (Ar-N2-H2) plasma for 1 to 3 h. Nitrogen diffuses into the surface layers from 400 °C and TiN starts to crystallize from 600 °C. Interdiffusion of Mo, Ti, and Si through Mo–Ti bilayer films gives rise to the formation of Mo–Ti alloys and MoSi2 of hexagonal structure, which transforms into MoSi2 of tetragonal structure at longer treatment durations. A 1 h 30 min plasma exposure at 800 °C leads to the formation of three layers of nearly equal thickness with clear interfaces, which consist of TiN and MoSi2 of nanometric size in the vicinity of the Mo–Ti bilayer film surface.

Interface study of thermally driven chemical kinetics involved in Ti/Si3N4 based metal-substrate assembly by X-ray photoelectron spectroscopy

“…Here, one of the key observations is that the appearance of TiN as the majority phase for each of the studied Ta unambiguously. Therefore, this thermally driven metal-substrate interaction technique can be used as an efficient nitridation technique, which is different than the other conventional methods requiring external source of nitrogen [18,[22][23][24][25][26] to produce TiN. Of particular interest towards the superconducting properties, ultrathin films of disordered TiN have exhibited various fundamental quantum phenomena such as superconductor-insulator (SIT) quantum phase transition [27], quantum criticality [28], quantum phase slip etc.…”

Double side nanostructuring of microcantilever sensors with TiO2-NTs as a route to enhance their sensitivity

“…After sputter deposition on a silicon wafer, we observed the (100), (002), (101) and (102) planes corresponding to the Ti crystal structure (JCPDS: 00-44-1294). 38,39 After anodization, we observe that the peaks corresponding to the Ti crystal structure remain present on the XRD pattern. However, we noticed that their intensity is reduced indicating the titanium consumption during the anodization.…”

Large Transfer of Nitrogen, Silicon and Titanium through Various Thin Mo–Ti/Si and Ti–Mo/Si Bilayer Films Processed in Expanding Microwave Plasma: Formation of Nitrides and Silicides

“…It is worth noting that Ti can form complete solid solutions with Mo, which promotes the stability of the β phase of the body-centered cubic structure as Ti0.9Mo0.1 (JCPDS card n • 04-018-6034) with the most intense (110) reflection line at 2θ = 39.08 • , in contrast with the α phase of hexagonal structure. More details are given in [29,[33][34][35][36]. The diffraction pattern (c) in Figure 2 corresponding to the TiMo2 bilayer film displays the features of pure Ti of hexagonal structure as well as those of pure Mo.…”

“…A similar effect has been observed in the case of a MoSi 2 layer coated with a TiN layer in our previous work. The surface layer of TiN was sufficient to block any Raman emissions from MoSi 2 [29]. At higher wave numbers, from approximately 490 cm −1 , the series of broad spectral features of low intensity correspond to ill-crystallized and/or disordered oxides.…”

“…Only 20 min of treatment produces MoN thin films, 500 nm thick, at low power and low temperature. Mo-Ti bilayers consisting of Mo and Ti films, 250 nm thick each, deposited on Si wafers, respectively, have been successfully nitrided and resulted in the formation of faceted grains of TiN of nanometric sizes on the bilayer surface [29]. The aim of this work is to investigate the formation and the crystallization of compounds such as silicides and nitrides in four Mo-Ti bilayer thin films of different thicknesses and locations with respect to the Si substrate, heated up to 873 K and exposed to (Ar-N 2 -H 2 ) plasma.…”