Al-Si interdiffusion (Al in Si and Si in Al)

• At 400oC junction spiking takes place (Al diffuses through the n-type Si until it reaches the p-type Si, destroying the junction)
• Solutions:
  • Sputtering an alloy of Al-Si (1wt%) - therefore presaturatting Al with Si, thus no need to diffuse in Si
  • Diffusion barriers - a kinetic barrier can be inserted against interdiffusion between the two materials
    • The material need to be inert for both Si and Al and has to have low resistance, so that it does not slow the junction efficiency
    • Possible materials: TiW, silicides

Technology of silicides, salicides

• Examples: MSi₂, TiSi₂, etc
• Purpose: low resistance contacts
• Formed: annealing a layer of metal deposited on Si
• How: one diffuses more, the marker moves whole lattice in the other sense to avoid stress