epdf.pub_nanotechnology-and-nanoelectronics-materials-devic

3.5 Evaluation and Future Prospects 37
Another concept is the sequential coverage of the inner cylinder walls with
metals and insulators. This is a way to produce cylinder capacitors.
By using the nuclear tracks as a via, coils and inductances can be manufactured,
provided that they are arranged in a skillful way. By combining capacitors, coils
and hybrid applied plastic electronics are even conceivable as complete analog
circuits.
3.5 Evaluation and Future Prospects
Ever it has been possible to grow suitable semiconductor materials for electronic
devices, the defects contained in the material have been regarded as hostile and
harmful. On the whole this finding is still correct but in the meantime, niches have
developed in which defects deliver positive applications. The first example is of
course the procedure described above for the switching time adjustment of power
devices. Although it has been worked on for more than 30 years, it is still the
subject of intensive investigations [40]. Historically, the next application is the
back side gettering which works with different methods such as back side implantation,
mechanical graining, coverage with phosphorus silicates etc. [41]. The
idea common to all procedures is that the defects of the back side are supposed to
attract impurities inside the silicon and catch them permanently. Today’s solution
is based on the same principle, even if the getter center is now inside the silicon.
Moreover, this procedure is still investigated thoroughly despite certain experiences
by manufacturers of semiconductor material. With procedures such as smart
and soft cut, nanodefects play a new role in the device production. They are directly
used for the production of certain structures. In process engineering, this
procedure is referred to as defect engineering. In the meantime, smart cut has
found a parallel application in solar cell production [42]: the surface of originally
monocrystalline silicon is converted into porous silicon by current. This occurs by
forming two thin layers of different properties. In particular the upper layer can be
recrystallized by for instance, a laser treatment while the lower one remains porous.
This lower layer is removable from the wafer so that a thin layer structure is
gained which can be applied on a ceramic substrate for further treatment. In this
way the economical production of many thin layer solar cells from one wafer is
desirable. In the whole area of photovoltaics, defects which are produced by the
exposure of silicon in a hydrogen plasma are expected to substantially improve the
properties of the solar cell. This applies particularly to the surface whose free
silicon bonds are to be saturated by hydrogen.
Fig. 3.28
Nanometric capacitor