PVD by Sputtering


Sputtering is a process whereby coating material is dislodged and ejected from the solid surface due to the momentum exchange associated with surface bombardment by energetic particles.


Sputtering Mechanism

The exact mechanisms by which atoms are ejected from a surface under ion bombardment are unknown, but we can deduce some of the details of the interaction involved.
The kinetic energy of the impinging particles largely dictates which event will happen
  1. Bounce back :
    • when very low energy (<5eV);
    • when the collision is head-on or nearly so
  2. Embedded : when much higher energy (>10KeV), the impinging particles are most likely to be embedded in the target, which is the basis of Ion Implantation
  3. Energy between the two extremes, two other effects also arise:
    • some fraction of the energy of the impinging ions is transferred to the solid in the form of heat, and lattice damage
    • another fraction of such energy causes atoms from the surface to be dislodged and ejected into the gas phase----Sputtering

Unique Characteristics

Coating Materials

Metals			Al, Cu, Zn, Au, Ni, Cr, W,  Mo, Ti
Alloys			Ag-Cu, Pb-Sn, Al-Zn, Ni-Cr
Nonmetals		i-C, graphite, MoS2, WS2, PTFE
Refractory oxides	Al2O3, Cr2O3, Al2O3-Cr2O3, SiO2, ZrO2-Y2O3
Refractory carbides	TiC, ZrC, HfC, NbC, Tic-Ni, Tic-ZrC
Refactory nitrides	TiN, Ti2N, ZrN, HfN, TiN-ZrN, TiN-AlN-ZrN
Refractory borides	TiB2, ZrB2, HfB2, CrB2, MoB2
Refactory silicides	MoSi2, WSi2, Cr3Si2

Details of Sputtering Processes