F 2 gas mixtures offer ideal properties to be employed as chamber cleaning gas: low dissociation energy and high reactivity, which leads to superior efficiency and ease of abatement. In this work, a new F 2 gas mixture was used with a combination ratio of 10% Ar, 20% F 2 and 70% N 2 in order to obtain a maximum of 20% fluorine in inert gases. This novel Ar/N 2 /F 2 gas mixture has been evaluated as a candidate to replace conventional cleaning gases, like NF 3 , C 2 F 6 and CF 4 in an industrial AMAT P5000 CVD chamber tool. Standard equipment has been used, showing complete compatibility with the new gas. The tested Ar/N 2 /F 2 mixture shows improvements in both parameters, cleaning at a faster rate (up to more 27%), even requiring a lower amount of gas (minus 96% versus NF 3 ). The higher etching rate and the lower gas consumption assure a sensible CoO (Cost of Ownership) advantage to any potential user. The superior etch rate performance of the Ar/N 2 /F 2 gas mixture was combined with excellent etch non uniformities values, of ±3% (1sigma) on SiO 2 and of ±8% (1sigma) on Si 3 N 4 , respectively. Also amorphous Silicon (a-Si) was etched completely and uniformly. The particle performance data showing in average just 14 particle adders (0.25µm), indicating that no significant particle contamination was induced by the process and Ar/N 2 /F 2 can be used as a highly clean and efficient etching gas as well as an ideal drop-in replacement for the conventional cleaning gases.

The properties of cobalt as a contaminant in p-type silicon are studied by using cobaltimplanted wafers annealed by RTP or by RTP plus a low temperature furnace annealing. It is shown that after RTP most cobalt is under the form of CoB pairs. A quantification of cobalt contamination is provided based upon SPV measurements and optical pair dissociation. However, this quantification fails in furnace-annealed wafers because of the formation of a different level. It is shown that the CoB level is located near the band edges, whereas the level formed upon a low temperature furnace annealing is located near midgap. Besides, when the cobalt concentration is high enough a small fraction of cobalt is in a level different from the CoB pair even in RTP samples. This level can probably be identified with a previously observed midgap level. It is suggested that the same level is formed in RTP plus low temperature furnace annealed samples and in high concentration RTP annealed samples, and that this level may consist in some cobalt agglomerate.