P.H. Giauque

Highly metastable amorphous or near-amorphous ternary films (mictamict alloys)

Thin ternary films of the generic composition (early transition metal)–Si–(nitrogen or oxygen) can be synthesized that have an amorphous or near-amorphous structure and are highly resistant to crystallization upon thermal annealing. Common to all of them is the existence of two compounds that form a quasi-binary system. Some known properties of these films are reviewed. Their similarity with amorphous binary metallic alloys is emphasized. Many ternary systems should exist with which such amorphous films can be made. The name ‘mictamict’ is proposed to identify this general class of materials.

Thermal stability of amorphous Ti 3 Si 1 O 8 thin films

Abstract Films (220 nm-thick) deposited by reactive rf sputtering from a Ti 3 Si target with an argon/oxygen gas mixture were annealed for 30 min in vacuum at temperatures between 400 and 900°C. The films were characterized by 2 MeV He 2+ backscattering spectrometry and X-ray diffraction to monitor thermally induced changes. As-deposited, the films are X-ray-amorphous. First signs of crystallization appear at 600°C. Their composition remains constant and uniform throughout that temperature range, except for the loss of argon that is initially present in the film at a concentration of about 1 at.% and that fully escapes within 5 min at 650°C. Films without silicon obtained from a pure titanium target by reactive rf sputtering with oxygen and of a composition of Ti 1 O 2 are also X-ray-amorphous but crystallize much more readily. The significance of these results is discussed relative to other ternary films of analogous compositions that also tend to form highly stable amorphous or near-amorphous phases (‘mictamict’ alloys).

Thermal stability of amorphous thin films: Ti3Si1O8 vs. TiO2 and mictamict compounds

Abstract We have synthesized amorphous Ti3Si1O8 films 220 nm thick by rf sputtering of a Ti3Si target with a mixed argon–oxygen gas. The composition and structure of the films, as-deposited and upon thermal annealing in vacuum, was monitored by 2 MeV 4He2+ backscattering spectrometry, X-ray diffraction, and transmission electron microscopy. We contrast these results against those obtained for TiO2 films 100 and 300 nm thick obtained by the same deposition process from a titanium target. The results confirm earlier reports that show that the incorporation of SiO2 in a TiO2 film raises the crystallization temperature. We point out that Ti–Si–O films share this phenomenon with other ternary films. They form a particular class of materials, the mictamict compounds, of which Ti–Si–O films are but one member.

Stability of conducting amorphous Ru—Si—O thin films under oxygen annealing

Abstract Ru 1 Si 1 O 4 thin films were deposited on Si and oxidized Si substrates by reactive rf magnetron sputtering of an Ru 1 Si 1 target in an argon/oxygen gas mixture. Two MeV He 2+ backscattering spectrometry, four-point probe measurements and X-ray diffraction techniques were applied to study the films annealed at 700°C in 100% dry oxygen at pressures from 0.2 to 760 Torr. The as-deposited films are 180 nm thick, X-ray amorphous and have a thickness normalized sheet resistance ∼3 mΩ cm. After 5 min of annealing at 700°C all films show some crystallization of RuO 2 . Above an annealing pressure of 8 Torr RuO 2 crystals are clearly visible by optical microscopy. The temporal evolution investigated below 0.4 Torr shows that the film resistivity drops by one half within the first 5 min. Beyond that both the normalized sheet resistance and the fine-grain structure change little, if at all, for durations up to 4 h. No changes in film composition were detectable by backscattering spectrometry. Films grown on Si (111) vs. oxidized Si (100) substrates evolve identically, but an interfacial layer develops between the Ru 1 Si 1 O 4 film and the Si (111) substrate within the first 5 min of annealing which electrically decouples the film from the substrate.

Electronic transport in Ru-Si-O and Ir-Si-O amorphous thin films

We present here resistivity, Hall effect and magnetoresistance measurements at low temperatures (1 K > T > 300 K) and under high magnetic field (B > 8 T) of Ru17Si16O67 amorphous thin film. These amorphous films are characterised by a mixture of metallic RuO2 or IrO2 and insulating SiO2. For Ru17Si16O67 the resistivity decreases with increasing temperature but the variation is too small to be described by a thermal activation law. The resistivity of Ir18Si15O67 is lower than that of Ru17Si16O67, increasing with temperature. The change is only about 2% over the whole temperature range. For both materials, the Hall effect is very small and negative and varies slightly with temperature. The magnetoresistance is very small and positive not exceeding 2% at lowest temperatures and highest fields.

Annealing of amorphous Ir18Si15O67 films in dry oxygen

Abstract X-ray-amorphous films 210 nm thick of Ir18Si15O67 were deposited by reactive sputtering of a target of iridium and silicon on substrates of oxidized silicon wafers, and subsequently annealed for 1 h at 700 °C in dry oxygen at pressures of 0.2, 8.0 or 760 torr. Regardless of oxygen pressure the films’ composition is preserved, their microstructure changes little, and their resistivity drops only slightly from ∼1.9 to ∼1.7 mΩcm. These films resemble those of Ru20Si14O65 and of TM–Si–N (TM=early transition metal) in the thermal stability of their amorphous structure, but Ir18Si15O67 films differ sharply from all others by their high chemical inertness against dry oxygen.

Carbon substrates for backscattering spectrometry analysis

Graphite coated with a thin layer of photoresist and annealed in an inert ambient to vitrify the coating makes light, smooth substrates that are as good as polished diamond for the analysis of thin films by MeV He backscattering spectrometry.

Diamond metallization for Mo electroplating

A metallization system for diamond compatible with Mo electroplating is presented. The deposition of the thin films is made by RF sputtering. 2 MeV /sup 4/He/sup ++/ backscattering spectroscopy, X-ray diffraction and sheet resistivity measurements are used to characterize the metallization. The stability of the metallization is tested in a tube furnace in a vacuum of 7/spl times/10/sup -7/ Torr. The metallization consists of an adhesion layer 30 nm thick of Mo, a 240 nm thick TaSi-N diffusion barrier and an additional 200 nm thick Mo layer to facilitate the subsequent electroplating of a heavy Mo film. The Mo adhesion layer is found to react with diamond and form Mo/sub 2/C after annealing at 800/spl deg/C during 30 min. The Ta/sub 24/Si/sub 39/N/sub 37/ film is stable up to 1 h annealing at 900/spl deg/C, it starts losing nitrogen close to the surface for 1 h annealing at 1000/spl deg/C. The Ta-Si-N barrier prevent diffusion of C in the top Mo layer, which needs to be free of N, C, Si and Ta. This requirement is satisfied for annealing of the complete structure at 900/spl deg/C during 1 h. Mo-Si-N and Mo-N have also been potential candidates for diffusion barrier.