PHOTON EFFECTS IN DAMAGE OF POROUS LOW-k SIOCH DURING PLASMA CLEANING* Juline Shoeb a) and Mark J. Kushner b) a) Department of Electrical and Computer Engineering Iowa State University, Ames, IA 50011 [email protected]b) Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor, Ann Arbor, MI 48109 [email protected]http://uigelz.eecs.umich.edu Nov. 2011 * Work supported by Semiconductor Research Corporation
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PHOTON EFFECTS IN DAMAGE OF POROUS LOW- k SIOCH DURING PLASMA CLEANING *
PHOTON EFFECTS IN DAMAGE OF POROUS LOW- k SIOCH DURING PLASMA CLEANING * Juline Shoeb a) and Mark J. Kushner b) a) Department of Electrical and Computer Engineering Iowa State University, Ames, IA 50011 [email protected] b) Department of Electrical Engineering and Computer Science - PowerPoint PPT Presentation
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PHOTON EFFECTS IN DAMAGE OF POROUS LOW-k SIOCH DURING PLASMA CLEANING*
Juline Shoeba) and Mark J. Kushnerb)
a) Department of Electrical and Computer EngineeringIowa State University, Ames, IA 50011
The capacitance of the insulator contributes to RC delays in interconnect wiring.
Low-k porous oxides, such as C doped SiO2 (CHn lining pores) reduce the RC delay.
Porosity 0.5, Interconnectivity 0.5.
Plasmas may remove hydrophobic -CH3 groups. Free radical sites adsorb H2O and increase k.
Desire to maintain low-k value by minimizing -CH3
damage.AVS_03
LOW-k PLASMA DAMAGE
University of MichiganInstitute for Plasma Science & Engr.
Mask
Si
Porous Low-kSiCOH
Typical porous SiO2 has CH3 lining pores with Si-C bonding – referred to as SiOCH.
Ave pore radius: 0.8-1.1 nm Porosity: up to 50% Etching, damage, cleaning,
sealing and H2O uptake of SiOCH is modeled as multistep process Etch Ar/C4F8/O2 CCP Damage/Clean Ar/O2 or He/H2 ICP Low-k H2O Uptake Sealing To Prevent H2O Uptake
University of MichiganInstitute for Plasma Science & Engr.
O atoms can abstract H from –CH3 groups and remove -CH3: O + Si-CH3 (s) Si-CH2(s) + OH(g) O + Si-CH2(s) Si(s) + CH2O(s) O + CH2O(s) CO(g) + H2O(g).
O atoms can cause Si-C bond scission and remove –CH3 groups:
O + Si-CH3 (s) -CH3(s) + Si(s) + O(g)
O + -CH3 (s) -CH2O(s) + H(g)
O + CH2O(s) CO(g) + H2O(g).
H removes -CH3 as CH4(g) and abstracts H forming Si-CHx-1 groups:
H + Si-CH3 (s) -Si(s) + CH4 (g)
H + Si-CHx(s) Si-CHx-1(s) + H2(g).Ref: M.F.A.M. van Hest et al., Thin Solid Films 449 40 (2004) O. V. Braginsky et al., Journal of Aplied Physics 108 073303 (2010) A. M. Urbanowicz et al., Journal of The Electrochemical Society, 157 5 H565-H573 (2010).
AVS_05
PHOTON GENERATION AND DAMAGE: Ar/O2, He/H2 ICP Photons penetrate into the porous SiCOH, are adsorbed by SiO2 and
University of MichiganInstitute for Plasma Science & Engr.Ref: J. Lee and D. B. Graves, J. Phys. D 43, 425201 (2010). AVS_06
LOW-k DEGRADATION: WATER VOLUME
University of MichiganInstitute for Plasma Science & Engr.
Ref: T. Kikkawa, S. Kuroki, S. Sakamoto, K. Kohmura, H. Tanaka, andN. Hata, Journal of The Electrochemical Society, 152(7), G560-G566 (2005).
Since H2O has a high k (~80), water adsorption can seriously degrade k of porous SiCOH.
Even a small percentage of H2O addition degrades the low-k.
Only 2.5% of water volume makes the k as high as solid SiO2 (~3.9).
Degradation of k and adsorbed water volume are related:
AVS_07
LOW-k DAMAGE BY H2O UPTAKE AND SEALING O2 Plasma :
O2 plasmas remove CH3 groups and increases the k (water adsorption from humid air).
He Plasma Power Increase in power of He
plasma improves surface activation.
A better activated surface seals the pores better (blocks water uptake) during NH3 plasma treatment.
Ref: K. Maex, M. Baklanov, D. Shamiryan, F. Iacopi, S. H. Brongersma, K. Maex, and Z. S. Ya novitskaya, J. Appl. Phys. 93, 8793 (2003).
Ref: A. M. Urbanowicz, D. Shamiryan, A. Zaka, P. Verdonck, S. De Gendt and M. R. Baklanov, J. Electrochem. Soc. 157, H565 (2010). Iowa State University
Optical and Discharge PhysicsAVS_08
University of MichiganInstitute for Plasma Science & Engr.
N/NHx species are adsorbed by activated sites (generated by He treatment) forming Si-N and C-N bonds to seal pores.
Further Bond Breaking M+ + SiO2(s) SiO(s) + O(s) + M
M+ + SiO(s) Si(s) + O(s) + M
N/NHx Adsorption NHx + SiOn(s) SiOnNHx(s)
NHx + Si(s) SiNHx(s)
NHx + CHn-1 (s) CHn-1NHx(s)
SiNHx-NHy/CNHx-NHy compounds seal the pores where end N are bonded to Si or C by C-N/Si-N
NHy + SiNHx(s) SiNHx-NHy(s)
NHy + CHn-1NHx(s) CHn-1NHx-NHy(s)
SEALING MECHANISM IN Ar/NH3 PLASMA
AVS_09
MODELING : PLASMA DAMAGE OF LOW-k
Hybrid Plasma Equipment Model (HPEM)
Plasma Chemistry Monte Carlo Module (PCMCM)
Monte Carlo Feature Profile Model (MCFPM)
Energy and angular
distributions for ions and
neutrals
He/H2 or Ar/O2
PLASMA DAMAGE
Porous Low-k
Coils
Wafer Substrate
Metal
Plasma
HUMID AIR(H2O)
University of MichiganInstitute for Plasma Science & Engr.AVS_10
MONTE CARLO FEATURE PROFILE MODEL (MCFPM) The MCFPM resolves the surface topology
on a 2D Cartesian mesh to predict etch profiles.
Each cell in the mesh has a material identity. (Cells are 4 x 4 A ).
Gas phase species are represented by Monte Carlo pseuodoparticles.
Pseuodoparticles are launched towards the wafer with energies and angles sampled from the distributions obtained from the PCMCM.
Adsorption of photons and photon-surface interactions considered.
Cells identities changed, removed, added for reactions, etching, and deposition.
PCMCM
Energy and angular distributions for ions
and neutrals
HPEM
MCFPM
Provides etch rateAnd predicts etch
profile
University of MichiganInstitute for Plasma Science & Engr.AVS_11
LOW-k DAMAGE :PLASMA REACTOR
University of MichiganInstitute for Plasma Science & Engr.