Reactive Ion etching

1
Reactive Ion etching
Advantages of dry etching no dangerous liquid
(but, toxic corrosive gases) anisotropic etch
profile high resolution, faithful pattern
transfer
Basic configuration of RIE
RF(13.56MHz)
2
Reactive Ion etching
Etch species for specific materials
Si fluorine/chlorine SiO2 CF4 Organics
O2 Metals compound semiconductor Cl-based
Effect of process parameters on etch behavior in
RIE anisotropiy etch rate uniformity
selectivity damage RF power ?
? ? ?
? ? Pressure
? ? ?
? ? ?
Gas flow rate greater the better (limited by
pumping system)
3
Reactive Ion etching

• Some selected etch recipes (PlasmaTherm RIE in
  MRL)
• (anisotropic etch, if pressure is below 50mTorr
  and DC voltage is larger than 200V)
• SF6, 40sccm, 50mTorr, 100W 1um/min. Si
• 150W
  1.5um/min. Si
• SF6 isotropic etch for Si (similar to wet
  chemical etching)
• mix with O2 for anisotropic
  sidewall
• high selectivity over SiO2
  (almost no etch of SiO2 at low power)
• SF6/O2, 20/20sccm, 150mTorr, 300W 1um/min. Si
• 20nm/min. SiO2
• CF4, 40sccm, 50mTorr, 100W 12nm/min. SiO2
• 30nm/min. Si
• CHF3/CF4, 15/5sccm, 150mTorr, 300W, 100nm/min.
  SiO2
• CHF3/O2, 40/5 sccm, 20mTorr, 150W 15nm/min.
  SiO2
• O2, 10sccm, 20mTorr, 100W 80nm/min. PR
  (anisotropic etching ? de-scum)
• O2, 20sccm, 50mTorr, 200W for PR ashing
• O2, 20sccm, 100mTorr, 100W 40nm/min.
• SF6/O2, 10/10sccm, 20mTorr, 200W 25nm/min. Ta
  (sputtered)
• CF4/O2, 25/5sccm, 100mTorr, 200W 40nm/min. Mo
  (evaporated)