Process Hierarchy

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  Alumina (Al2O3) Atomic Layer Deposition (ALD)
Process characteristics:
must be 100 .. 177 °C
100 .. 177 °C
must be 5 .. 150 nm
5 .. 150 nm
Batch size 1
Material alumina
Pressure of process chamber during processing
1 Torr
Refractive index 1.65
Relative dielectric constant 7.5 .. 7.8
Sides processed either
Equipment Viscous flow reactor
Equipment characteristics:
MOS clean no
Piece dimension
Range of wafer piece dimensions the equipment can accept
1 .. 150 mm
Piece geometry
Geometry of wafer pieces the equipment can accept
triangular shard, other, rectangular, irregular, circular
Piece thickness
Range of wafer piece thickness the equipment can accept
100 .. 1000 µm
Wafer materials
List of wafer materials this tool can accept (not list of all materials, just the wafer itself).
fused silica, silicon on insulator, alumina, silicon, polycarbonate
  • The coating is deposited using Atomic Layer Deposition (ALD), which is a coating process capable of depositing ultra-thin, conformal films of a variety of materials. Compared to traditional CVD processes, ALD allows for Angstrom-level thickness control with super-conformal films. The ALD process relies on a sequence of two self-limiting reactions between gas phase precursor molecules and a solid surface. During the reaction sequence, only one reactant is present in the reaction zone at a time. This procedure prevents unwanted gas phase reactions and particle formation. Films that are pinhole-free result when these two reactions are allowed to go to completion. The substrate will be conformally coated as long as the gaps between the different parts or devices are larger than the ALD precursor molecules, thus large aspect ratios structures can be coated. The ALD films will cover all sides of a released MEMS device including bottom surfaces, such as underneath cantilever beams.
  • Another advantage of the ALD process is that it can be carried out at relatively low temperatures significantly cooler than typical CVD temperatures. For this process, alumina films are deposited between 100 and 200C, which allows for coating composite devices.
  • The batch size for the ALD process is the number of die that will fit in a 6" diameter area.
ALD_summary.pdf (205.0 KB, application/pdf)
attached by ozgur (Mehmet Ozgur) on 2005-07-18 10:10