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All the samples were prepared in a similar manner. A film
was grown on the silicon substrate and then silicon from the back
side of the wafer was
etched away in a circular opening approximately 0.5 centimeter in
diameter. The etching stops when the film is reached.
This results in an extremely thin film sitting on the top of the silicon frame.
The cross section of such structure is shown in Fig. 4.55.
The following samples were prepared at Lincoln Lab for the
1. Thin SiO2 film (dry oxidation of Si wafer at 1000o C, a process identical to the one used for CCD gate oxide growth), nominally 0.14 microns thick.
2. Thick SiO2 film (wet oxidation at 1000o C, a process used for channel stop oxide growth), approximately 1.5 microns thick.
3. A sandwich of SiO2+Si3N4+SiO2, a copy of the CCD gate insulator structure, nominal thicknesses 0.06 + 0.03 + 0.015 microns.
4. Phosphorus doped polycrystalline silicon, 0.6 microns thick.
5. The same polycrystalline silicon film partially oxidized, nominally 0.46 + 0.2 microns of Si+SiO2 respectively.