PE2-5.2 Materials for MEMS

Work through these

• Substrates and wafers

  What the device is built on, before any material properties. The choice of substrate constrains every process step that follows.

• Active substrate materials

  Substrates that do something rather than merely support, which is a distinction specific to this field. It is what allows the substrate itself to be part of the device.

• Silicon as a substrate material and its mechanical properties

  The dominant material, and the mechanical properties that make it good: it is stronger than steel and perfectly elastic to fracture. That second property is why it makes good springs.

• Silicon compounds

  The oxide and nitride, used as insulators, masks and structural layers. Their residual stress is a design parameter here rather than an afterthought.

• Piezoelectric crystals

  Materials that turn force into charge and back, which is how many actuators work. It is the same principle as the transducer subject, at small scale.

• Polymers

  The plastics, used where silicon is too stiff, too expensive or not biocompatible. They dominate the microfluidic end of the field.

• Packaging materials

  What the finished device is put in, which matters more here than in ordinary chips because something has to move or be exposed.