17 - ECE331 Diffusion Diffusion in materials can happen at...

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1 Lu ECE331 Diffusion Diffusion in materials can happen at different levels: Molecular diffusion Atomic diffusion Carrier diffusion (electrons and holes, more in ECE432) Lu ECE331 Atomic Diffusion Why do we study atomic diffusion? Atomic diffusion is common in semiconductor device processing : For example: Impurities in semiconductors (doping) Metal-semiconductor contacts (Ohmic or Schottky) Metal-metal alloys Semiconductor/oxide and oxide/poly-Si interfaces,…. Same principles can be applied to carrier diffusion.
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2 Lu ECE331 Interstitial Diffusion Generally happens for small atom diffusion. Smaller the atomic size, the higher diffusion probability Temperature dependent Size dependent Time dependent Lu ECE331 Vacancy Diffusion Two conditions: Empty adjacent lattice sites Sufficient energy
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3 Lu ECE331 Steady State Diffusion- Time Independent 1. Diffusion Flux (J): (Kg/(s.m 2 ) Rate of Mass transfer per unit time and area. 2. If J is independent with time (t)-----
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  • Spring '09
  • RAJAN
  • Semiconductor device fabrication, Chemical vapor deposition, Epitaxy, State Diffusion, diffusion Atomic diffusion

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17 - ECE331 Diffusion Diffusion in materials can happen at...

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