ECE6450L12-Physical Deposition

ECE6450L12-Physical Deposition - Lecture 12 Physical Vapor...

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ECE 6450 - Dr. Alan Doolittle Georgia Tech Lecture 12 Physical Vapor Deposition: Evaporation and Sputtering Reading: Chapter 12
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ECE 6450 - Dr. Alan Doolittle Georgia Tech Evaporation Evaporation and Sputtering (Metalization) For all devices, there is a need to go from semiconductor to metal. Thus we need a means to deposit metals. Many of these techniques used for metal deposition can be used to deposit other materials as well. Several methods are currently used for deposition of metal layers. Physical Vapor Deposition techniques (PVD) 1.) Evaporation 2.) Sputtering 3.) Chemical Vapor Deposition (CVD) 4.) Electrochemical techniques 1.) Evaporation : Advantages: Highest purity (Good for Schottky contacts) due to low pressures. Disadvantages: Poor step coverage, forming alloys can be difficult, lower throughput due to low vacuum. Evaporation is based on the concept that there exists a finite “vapor pressure” above any material. The material either sublimes (direct solid to vapor transition) or evaporates (liquid to vapor transition).
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ECE 6450 - Dr. Alan Doolittle Georgia Tech Two main types of evaporators: E-beam and filament. Evaporator Systems Rough Pump Cryo or Turbo Pump Air Inlet Valve Valve Valve Wafers Heated Material Vacuum Chamber
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ECE 6450 - Dr. Alan Doolittle Georgia Tech Px T e P e evaporation H NkT o Ea kT =≈ 310 12 3 2 1 2 σ // J P kTm = 2 2 π R m k P T Area r d evaporation = 24 22 πρ For evaporation, the vapor pressure is, where σ is the surface tension of the liquid, N is avagadro’s number, and H is the enthalpy of evaporation (the energy required to convert from a liquid to gas phase).
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This note was uploaded on 08/23/2011 for the course ECE 6450 taught by Professor Doolittle during the Fall '10 term at University of Florida.

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ECE6450L12-Physical Deposition - Lecture 12 Physical Vapor...

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