Group 2 Element Precursors for the

Group 2 Element Precursors for the Chemical Vapor Deposition of Electronic Materials Jason S. Matthews and William S. Rees Jr. 

GROUP 2 ELEMENT PRECURSORS FOR THE CHEMICAL VAPOR DEPOSITION OF ELECTRONIC MATERIALS... 

Because of the low volatility of Group 2 compounds, even more extreme methods to ensure that the precursor can reach the substrate have been used. In many cases described in Section IV, a container with the Group 2 element precursor was placed directly inside the CVD reactor adjacent to the substrate. A schematic diagram of a typical reactor setup is shown in Fig. 3.31 This has often led to successful transport of the Group 2 precursor to the heated substrate surface, but it is unlikely that these conditions can be scaled up for practical applications. 

Although the problems described above for barium precursors also are associated, albeit less severely, with the other two group 2 elements used for obtaining SMO, that is, calcium and strontium, the major research effort in several groups has been focused towards the substantially more difficult volatilization of barium. 

It is important to note that in none of these examples of intermolecularily stabilized barium bis( -diketonate) complexes was found complete achievement of the criteria for CVD precursors for SMO given at the outset of this section. Therefore, other routes had to be explored in the search for the required higher volatility, higher stabihty vapor transport vehicles to be employed for the heavy group 2 elements desired for electronic materials applications. 

This class of compounds was, until recently, almost completely unexplored for the group 2 elements. Lappert s treatise on metal amides gives brief mention to the existence of such species. Although the compounds have not yet been proven as precursors for metal oxides, several examples of compounds employing the bis[bis(trimethylsilyl)] ligand were discussed above in the section on compounds formed between group 2 elements and group 15 elements. Perhaps there will be some additional work here, which is directed towards SMO CVD, that will eventually come out ft om this same approach. 

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