Research Interest    
   
��研 究 方 向
  
         
  ALD ( atomic layer deposition )
  Introduction
    Atomic Layer deposition (ALD) as a technique which allows film deposition with monolayer precision has matured substantially and is now being introduced into semiconductor processing. Key ALD application include the deposition of high-k dielectrics, metal electrodes, barriers, and spacers.
 
  ALD growth process

    ALD is based on the sequential deposition of individual monolayer or fractions of a monolayer in a well controlled manner. The growth surface is alternately exposed to only one of two complementary chemical environments, i.e. individual precursors are supplied to the reactor one at a time. Exposure steps are separated by inert gas purge or pump-down steps in order to remove any residual chemically active source gas or by-products before another precursor is introduced into the reactor.
 
 

    Thus, ALD consists of a repetition of individual growth cycles. Each cycle is made up of a typical sequence :

Flow of precursor A → Purge → Flow of precursor B → Purge. During each exposure step, precursor molecules react with the surface until all available surface sites are saturated.

 

The advantages of ALD film

  • Film thickness is given by the numbers of deposition cycle
  • 100% step coverage even at high aspect ratios
  • Lower deposition temperatures
  • Films are very uniform, smooth