Biomedical Engineering Reference
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process corresponds to the pattern of the shallow starter pits. The
cross section of the pores is usually square with rounded corners
and their size can be varied by changing the etching current. More
complex cross sections can be generated by overlapping of pores
using additional etching steps and corresponding pattern definition
(e.g. by means of lithography).
Macroporous silicon structure generated by means of
electrochemical etching of single-crystalline silicon (Source: V. Lehmann,
Siemens AG) [108]. Reproduced by kind permission from the publisher.
Figure
1.6
Such confined etchant layer technique has been applied to
achieve effective three-dimensional (3D) micromachining on n-GaAs
and p-Si. It operates via an indirect electrochemical process and is
a maskless, low-cost technique for microfabrication of arbitrary
3D structures in a single step [109]. It has also been presented that
free-standing Si quantum wire arrays can be fabricated without
the use of epitaxial deposition or lithography by electrochemical
and chemical dissolution of wafers [110]. This novel approach uses
electrochemical and chemical dissolution steps to define networks
of isolated wires out of bulk wafers.
Electrochemical methods, either alone or in combination with
other techniques, have been developed for shaping materials. 3D
microstructures with extremely high precision and aspects ratio
can be manufactured by means of LIGA technology, which combines
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