《建筑施工模板安全技术规范》JGJ.ppt

Semiconductor materials
Lecturer: Aimin Liu & Weifeng Liu
刘爱民刘维峰
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Chemical vs. chemical/physical etching
Purely chemical etching
(using only reactive
neutral species)
Isotropic etching
Chemical + physical etching
(using reactive neutral species
and ionic species)
Anisotropic etching
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• Many different mechanisms proposed for this synergistic etching between physical
and ponents. Two mechanisms are shown above.
• Ion bombardment can enhance etch process (such as by damaging the surface to
increase reaction, or by removing etch byproducts), or can remove inhibitor that is
an indirect byproduct of etch process (such as polymer formation from carbon in gas
or from photoresist).
• Whatever the exact mechanism (multiple mechanisms may occur at the same time):
• need ponents for etching to occur.
• get anisotropic etching and little undercutting because of directed ion flux.
• get selectivity due to ponent and chemical reactions.
There are many applications in etching today.
Ion-Enhanced Etching
ponent selectivity
ponent anisotropy
volatility of byproducts
Roles of ions:Adsorption, Reaction, Formation of byproducts, removal
SILICON VLSI TECHNOLOGY
Fundamentals, Practice and Modeling
By Plummer, Deal & Griffin
© 2000 by Prentice Hall
Upper Saddle River NJ
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Effect of the inhibitor
w/o inhibitor
=> Isotropic
w/ inhibitor
=> Anisotropic
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Plasma assisted etching
Dry chemical etching (Plasma etching)
RF energy is applied to a separate electrode with the substrates grounded. Material is removed from the substrate by chemical means.
Purely chemical etching
Glow discharge is used to produce chemically reactive species (atoms, radicals, or ions)
Reactive-ion Etching (RIE)
If RF energy is applied to the substrates in a low pressure halogen-rich environment, material can be removed by both chemical means and ion bombardment of the substrate surface. Greater control over line widths and edge profiles is possible with oxides, nitrides, polysilicon a