Enabling Manufacturing Technologies - Implications of Emerging Micro-and Nanotechnologies - page 132

MICRO-
MECHANICS

MICRO-
OPTI CS

MICRO-
MAGNETICS MICRO-

ELECTRONICS

MATERIALS

FIGURE 4-5 Integrated circuit production. The number of materials and associated pro-
cesses for the production of micromechanics, -optics and -magnetics greatly exceeds the
number of materials and processes used to manufacture microelectronics.

nology that has no role in IC manufacture. Such etching is done by one of two
processes. The use of solvents, which attack different planes in silicon at widely
varying rates, is called orientation-dependent etching. It now plays a role in the
production of some MEMS products. The alternative is deep reactive-ion etching
(DRIE). In this case, the plasma ambient over a silicon substrate is alternated
every few seconds between etching and passivation (coating) conditions. This
process, invented by the Bosch Corporation, can result in deep, narrow trenches
in the substrate, the walls of which are scalloped on a very fine scale. Figure 4-6
shows examples, and it also indicates that the rate at which the Bosch process
etches into the silicon is geometry dependent. 13
The role of pattern transfer for the production of nanoscale structures and
devices will probably be similar to that for the production of microscale struc-
tures and devices involving mechanics, optics, and magnetics. That is, the trans-
fer processes used in microelectronics manufacture will remain important in
many cases. The self-assembly of complex structured materials, as discussed in
the next section, is playing an increasingly important role in nanoscale fabrica-
tion. New approaches using lithography to direct self-assembly are already emerg-
ing in fields as disparate as semiconductor crystal growth (discussed below) and
carbon nanotube formation and are likely to play a significant role in the develop-
ment of nanotechnology. The wider variety of materials that will play a role in
nanotechnology will probably involve additional techniques for pattern transfer.
This will almost certainly be the case for nanoscale structures that use organic
and biomaterials.