Effect of Oxygen Content and Sinter Conditions on Dislocation Formation

4 Effect of Oxygen Content and Sinter Conditions on Dislocation Formation 

The bulk oxygen content in the Ta anode strongly affects this crystallization process in the dielectric oxide film [249, 250], If the oxygen concentration in the bulk approaches the solubility limit (about 3.200 wt. ppm for Ta at room 

Ta2Os film, this sliding will cause mechanical cutting of the crystals away from the metal surface. Loosing intimate contact with the metal surface undermines their further ability to grow. They are passively buried in the amorphous matrix of the anodic oxide film. 

Reduction of Crystallization by Purity Improvement One root cause for crystallization even with a reduced oxygen content can be attributed to further impurities at the particle surface. The trivial fix for this would be an improvement in purity, which is actually difficult to achieve with the conventional K2-salt Na-reduction process described above (see p. 63). However, the second route, that is the Ta metal powder production by Mg reduction of the oxides, delivers purer metal powder grades (at least with respect to alkali elements). Therefore, this route may be superior for ultra-high CV powders. Moreover, higher purity is beneficial to achieve a higher BDV (break down voltage) as is known from E-beam melted powder. 

Moreover, from semiconductor manufacturing processes (e.g. the DRAM process as will be described later) it is known that doping of the film can also stabilize an amorphous matrix. Such a doping could potentially also be achieved electrochemically by a corresponding addition of the dopants to the electrolyte. 

---