Tantalum annealing

Niobium is always found in nature associated with tantalum and it closely resembles tantalum in its chemical and mechanical properties. It is a soft ductile metal which, like tantalum, work hardens more slowly than most metals. It will in fact absorb over 90% cold work before annealing becomes necessary, and it is easily formed at room temperature. In addition, welds of high quality can be produced in the metal. In appearance the metal is somewhat similar to stainless steel it has a density slightly higher than stainless steel and a thermal conductivity similar to 1% carbon steel. 

MOCVD reactions are used increasingly, such as the pyrolysis of tantalum ethylate, Ta(OC2H5)5, in oxygen and nitrogen at 340-450°C and at a pressure of <1 Torr. This is followed by an annealing cycle at 600-900°C.P l Tantala is also deposited by the pyrolysis of the tantalum dichlorodiethoxy acetylacetonate at 300-500°C.P ]... 

Tantalum Nitride as Diffusion Barrier. Tantalum nitride (TaN) produced by MOCVD has excellent potential as a barrier material, comparable to TiN. The resistivity of TaN thin films can be lowered by rapid thermal annealing in nitrogen. 

We use commercial Ti02 crystals (Pi-Kent) cut and polished to within 0.3° of the (110) face and we prepare them further with cycles of Ar + bombardment and U H V annealing to approximately 950-1100 K, typically 5-10 min for each cycle. The samples are mounted onto tantalum back-plates via strips of tantalum spot-welded to the back-plate. Annealing is performed by high-energy electron bombardment of the back-plate from a hot filament. Temperatures are measured from optical pyrometers (Minolta) focused on the back-plate. The temperatures are not measured directly from the samples because they are translucent and get darker with each sputter/anneal cycle. 

The use of tantalum wire along with the two-zone technique ensures a safe reaction rate. When the sulfur has reacted completely with the tantalum wire (usually within 7-10 days) the ampule is removed from the furnace, shaken vigorously to break up clumps of unreacted material, and placed in the center of me furnace. It may be necessary to repeat this procedure several times to ensure that all the wire has reacted. After 1 or 2 days at 850-900°, the cooling process may be started. The sample is cooled initially to 750° and annealed for 1 day. It is then annealed at 650° for about a day and at 550° for another 2 to 3 days. The furnace is then shut off and the sample is allowed to cool for 5-6 hours to room temperature. 

The polycrystalline 2H(a)-TaS2 should be free flowing and in the form of black platelets. Any gold-colored material indicates the presence of the IT phase and results from improper annealing. Further, the presence of a fibrous or needlelike material indicates incomplete reaction of the tantalum. This fibrous material is most likely TaS3, which decomposes above 650°.14... 

La-Pt-Sb. LaPtSb crystallizes with the Cahi2-type structure, a = 0.4560, c = 0.8263 (Rossi et al., 1981 powder X-ray diffraction data). The starting elements (La 3N, Pt 4N, Sb 4N) were melted under argon in tantalum crucible, and annealed at 773 K for one week. 

The silicon carbide-based ceramic layer is obtained by CVD activated by a microwave plasma (2.45 GHz) on the tantalum previously cleaned by an argon plasma (56 min, 133 Pa, 250 W) at a temperature identical to the deposition temperature (T = 570°C), lower than the substrate annealing temperature. After readjustment of the total pressure and microwave power by introduction of a precursor (TMS) in the argon flow, the SiC coating is produced under selected conditions (66 Pa, TMS/Ar = 0.2/5.5 l.h-, T = 570°C, 350 W) derived from a previous parametric study. Coatings obtained then presented low dry friction coefficients. The mechanical properties, which are essential in order to be able to appreciate the mechanical stability, were acquired by several methods ... 

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