 |
The first experiments |
|
 |
Propst and Kohl showed 1994 that macropores on p-type-silicon can be
etched. They used HF in acetonitril and moderatly doped p-type-wafers. |
|
| |
|
|
|
| |
|
|
|
|
Stable macropore-growth on
p-type-silicon |
| |
|
As shown in an
paper from Christophersen et al. we
showed that large (up to 300 micrometer), small diameters and very stabile
macropores in p-type-silicon can be etched. |
 |
| |
|
|
|
| |
|
|
|
|
Influence of the electrolyte |
| |
|
"Designing of an electrolyte" gives new grades of
freedom for the pore etching system. We studied the influence of additives in
the electrolyte for macropores in p-type silicon.
The important parameters are availability of H and oxidizing compontents for
the electrochemical reaction. |
 |
| |
|
|
|
| |
|
|
|
| |
|
In an aqueous HF-containing electrolyte it is possible to etch
macropores under special conditions (after V. Lehmann and S. Rönnebeck).
The oxide-formation have to be suppressed by the very low etch-potential - the
H-termination is still ecfective. |
 |
| |
|
|
|
| |
|
|
|
|
Influence of the
substrate-orientation |
| |
|
The macropore-growth is anisotropic in <100> and
<113>-direction (the same direction were found in
n-type-silicon). The growth direction
depends on the surface-orientation. The macropore-walls consists of
(111)-facettes - shown by TEM-mircographs. Pore-formation is an anisotropic
process. |
 |
| |
|
|
|
| |
|
for details see:
M. Christophersen, J. Carstensen, A. Feuerhake, H. Föll, "Crystal
Orientation and Electrolyte dependence fore Macropore Nucleation and stable
Growth on p-tye-silicon", Mat. Sci. Eng. B, 69-70, 194 (2000) |
 |
| |
|
|
|
| |
|
These macropores were etched in an aqueous electrolyte. Best
macropores in p-type silicon can be obtained in organic electrolytes. |
 |
| |
|
|
|
| |
|
|
|
