In the deposition chamber1 the substrate heater/holder assembly is fitted with a reflective deposition shield in such a way as to prevent evaporated Al from shorting the electrical components of the tantalum heater array (Fig. 4.7a). The shield presents a small aperture in front of the substrate that causes the two evaporation sources (Si electron beam and Al effusion cell) to deposit in respective areas of the substrate. Fig. 4.7b depicts the respective Al and Si deposition patterns formed from this configuration on the patterned 3-inch Si wafer (cf. Fig. 4.2a).

(a) (b) Figure 4.7. Substrate Heater/Holder Assembly. a) The substrate assembly includes a reflective shield to prevent Al deposition on electrical heater components. b) The shield also permits several experiments to be conducted simultaneously. Si or Al can be analyzed separately for the procedure used for the complete Si + Al on oxide deposition. As well, each oxide pattern region may be utilized separately with Si, Al, or Si/Al.

By virtue of the cross-patterned deposition on the substrate, several analytical experiments can be conducted on the same wafer. For example, in Fig. 4.7b, region $p$ allows for Al on substrate, $q$ for Al on the 5/10 $\mu$m oxide pattern, $r$ for Al + Si on the 5/10 $\mu$m pattern, $s$ for Al + Si on 2/2 $\mu$m oxide, $t$ for Si on 50/500 $\mu$m pattern, and $u$ for Si on substrate analyses. Taken together, these regions permit extensive analytical investigative possibilities of the entire SMM-SOI process subjected to identical fabrication conditions. Such opportunities have been exploited and presented in the following chapter.

• 1. An overview of components in the MBE deposition chamber is provided in Appendix B.4.1.