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4 1 From Optical MEMS to Micromechanical Photonics
Al (sacrificed layer)
Si substrate
Resist

Exposure (UV light)

Mask

Development

Fig. 1.2. Basic process of photolithography using a negative resist

Top view
F 2
F 1

Stators
Rotor
+V
A A 9 F 2 F 1
T 9 T
Phasing scheme
9 F 1
F 3 F 3 F 3
F 2
T T 9 F 3
9 F 9
+ - V F 1 2
F 1
F 2 Silicon
Polysilicon
Fixed axle nitride
Silicon dioxidie
Cross section
Fig. 1.3. Top view, cross-section, and the phasing scheme of a micromotor fabricated
by surface micromachining [1.2] c 1988 IEEE

In the case of thick microstructures, SU-8 resists are widely used [1.23].
Physical properties of SU-8 can be found at http://aveclafaux.freeservers.com/
SU-8.html. To view typical SU-8 applications, visit http://www.mimotec.ch/.
As an example of optical MEMS, the process for fabricatingoptical pres-
sure rotors having anisotropic geometry on the side is shown in Fig. 1.4. First,
the SiO 2 layer is deposited on a GaAs substrate, and then the SiO 2 is etched
down to the GaAs substrate by reactive ion beam etching(not by UV light).
The substrate is then immersed in a wet-etchingsolution to dissolve the GaAs