The mechanical pre-preparation took place using the methods described in this chapter using a Ti grid. The individual steps are shown in Fig.1-3.
SEM images of the individual steps in the preparation with Ti grids:
Double sided polishing:
Leica EM TXP:
Diamond foils: 15 μm, 9 μm, 6 μm, 3 μm, 1 μm and 0.5 μm at 2200 rpm until the final sample thickness of 30 μm was reached.
|Acceleration voltage:||7 kV and 2.5 kV (final step)|
|Milling angle:||4° (milling on both sides)|
|Sample movement:||Rotation and oscillation (alternating)|
The effects of the ion beam preparation are shown in Figures 4 to 9. As a result of the ion beam milling with sample rotation, multi-layer systems with different sputter rates lead to the formation of a wall. This can be moved away from the area of interest by the use of a flatter milling angle and sample oscillation.
It was possible to carry out a target preparation of the structure of interest. The sample is electron-transparent over an area of approximately 200µm. All components can be irradiated to approximately the same extent, with the exception of the W plugs. If you wish to examine the grain structure of the W plugs and their boundary surfaces to other semiconductor structures, the sample must be re-thinned. As a consequence, this frequently causes the loss of the surrounding, more sputterable areas.
XTEM image of a layer - W plug boundary surface with eletron transparent W plug