SiO 2 ETCH RATE AND PROFILE CONTROL USING PULSE POWER IN CAPACITIVELY COUPLED PLASMAS* Sang-Heon Song a) and Mark J. Kushner b) a) Department of Nuclear Engineering and Radiological Sciences University of Michigan, Ann Arbor, MI 48109, USA [email protected]b) Department of Electrical Engineering and Computer Science University of Michigan, Ann Arbor, MI 48109, USA [email protected]http://uigelz.eecs.umich.edu September 21 st , 2011 * Work supported by DOE Plasma Science Center and Semiconductor Research Corp.
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SiO 2 ETCH RATE AND PROFILE CONTROL USING PULSE POWER IN CAPACITIVELY COUPLED PLASMAS* Sang-Heon Song a) and Mark J. Kushner b) a) Department of Nuclear.
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SiO2 ETCH RATE AND PROFILE CONTROL USING PULSE POWER IN CAPACITIVELY
COUPLED PLASMAS*
Sang-Heon Songa) and Mark J. Kushnerb)
a)Department of Nuclear Engineering and Radiological Sciences University of Michigan, Ann Arbor, MI 48109, USA
* Work supported by DOE Plasma Science Center and Semiconductor Research Corp.
AGENDA
Motivation for controlling f()
Description of the model
Typical Ar/CF4/O2 pulsed plasma properties
Etch property with different PRF
Constant Power with DC Bias
Constant Voltage with DC Bias
Without DC Bias
Concluding remarks
University of MichiganInstitute for Plasma Science & Engr.
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CONTROL OF ELECTRON KINETICS – f() Controlling the generation of reactive species for technological
devices benefits from customizing the electron energy (velocity) distribution function.
University of MichiganInstitute for Plasma Science & Engr.
, , , , ,, , ,
df v r t qE r t f v r tv f r v f v r t
dt m tx ve c
1 2
0
2, , ,ij
ek r t f r t d
m
,
,,k
e ij ji j
dN r tn k r t N
dt
e + CF4 CF3 + F + ek
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ETCH RATE vs. FLUX RATIOS
University of MichiganInstitute for Plasma Science & Engr.
Ref: D. C. Gray, J. Butterbaugh, and H. H. Sawin, J. Vac. Sci. Technol. A 9, 779 (1991)
Flux Ratio (F/Ar+) Flux Ratio (CF2/Ar+)
Etc
hin
g Y
ield
(S
i/Ar+
)
Etc
hin
g Y
ield
(S
i/Ar+
)
Large fluorine to ion flux ratio enhance etching yield of Si.
Large fluorocarbon to ion flux ratio reduce etching yield of Si.
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Ref: K. Ono, M. Tuda, H. Ootera, and T. Oomori, Pure and Appl. Chem. Vol 66 No 6, 1327 (1994)
Large chlorine radical to ion flux ratio makes undercut in etch profile due to too much chemical reactions.
Etch profile result in ECR Cl2 plasma after 200% over etch with different flux ratios
p-Si p-Si
University of MichiganInstitute for Plasma Science & Engr.
ETCH PROFILE vs. FLUX RATIOS
Flux Ratio (Cl / Ion) = 0.3 Flux Ratio (Cl / Ion) = 0.8
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HYBRID PLASMA EQUIPMENT MODEL (HPEM)
Fluid Kinetics Module: Heavy particle and electron continuity, momentum,
energy Poisson’s equation
Electron Monte Carlo Simulation: Includes secondary electron transport Captures anomalous electron heating Includes electron-electron collisions
E, Ni, ne
Fluid Kinetics ModuleFluid equations
(continuity, momentum, energy)Poisson’s equation
Te, Sb, Seb, kElectron Monte Carlo Simulation
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MONTE CARLO FEATUREPROFILE MODEL (MCFPM) The MCFPM resolves the surface
topology on a 2D Cartesian mesh.
Each cell has a material identity. Gas phase species are represented by Monte Carlo pseuodoparticles.
Pseuodoparticles are launched with energies and angles sampled from the distributions obtained from the HPEM
Cells identities changed, removed, added for reactions, etching deposition.
PCMCM
Energy and angular distributions for ions
and neutrals
MCFPM
Etch rates and profile
University of MichiganInstitute for Plasma Science & Engr.
Poisson’s equation solved for charging
HPEM
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REACTOR GEOMETRY: 2 FREQUENCY CCP
2D, cylindrically symmetric
Ar/CF4/O2 = 75/20/5, 40 mTorr, 200 sccm
Base conditions
Lower electrode: LF = 10 MHz, 500 W, CW
Upper electrode: HF = 40 MHz, 500 W, Pulsed
University of MichiganInstitute for Plasma Science & Engr.
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PULSE POWER
Time = 1/PRF
Duty Cycle
Power(t)
Pmin
0
1dttPPave
Pmax
University of MichiganInstitute for Plasma Science & Engr.
Use of pulse power provides a means for controlling f().
Pulsing enables ionization to exceed electron losses during a portion of the ON period – ionization only needs to equal electron losses averaged over the pulse period.