1 / 23

Arvind Sankaran 1 and Mark J. Kushner 2 1 Department of Chemical Engineering 2 Department of Electrical and Computer En

AVS 2002 Nov 3 - Nov 8, 2002 Denver, Colorado INTEGRATED MODELING OF ETCHING, CLEANING AND BARRIER COATING PVD FOR POROUS AND CONVENTIONAL SIO 2 IN FLUOROCARBON BASED CHEMISTRIES *. Arvind Sankaran 1 and Mark J. Kushner 2 1 Department of Chemical Engineering

qamra
Download Presentation

Arvind Sankaran 1 and Mark J. Kushner 2 1 Department of Chemical Engineering 2 Department of Electrical and Computer En

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. AVS 2002Nov 3 - Nov 8, 2002Denver, ColoradoINTEGRATED MODELING OF ETCHING, CLEANING AND BARRIER COATING PVD FOR POROUS AND CONVENTIONAL SIO2 IN FLUOROCARBON BASED CHEMISTRIES* Arvind Sankaran1 and Mark J. Kushner2 1Department of Chemical Engineering 2Department of Electrical and Computer Engineering University of Illinois, Urbana, IL 61801, USA email: asankara@uiuc.edu mjk@uiuc.edu http://uigelz.ece.uiuc.edu *Work supported by SRC, NSF and SEMATECH

  2. AGENDA • Low dielectric constant materials • Surface reaction mechanism and validation • Fluorocarbon etching of SiO2/Si • Ar/O2 etching of organic polymer • High aspect ratio etching of porous and non porous SiO2 • Integrated Modeling: Ar/O2 strip of polymer and IMPVD • Concluding Remarks University of Illinois Optical and Discharge Physics AVS03_AS_02

  3. LOW DIELECTRIC CONSTANT MATERIALS • The increase in the signal propagation times due to RC delay has brought the focus onto low dielectric constant (low-k) materials (inorganic and organic) • Inorganics such as porous silica (PS) are etched using fluorocarbon chemistries; organics are etched using oxygen chemistries. University of Illinois Optical and Discharge Physics AVS03_AS_03

  4. GOAL FOR INTEGRATED MODELING • Plasma processing involves an integrated sequence of steps, each of which depends on the quality of the previous steps. University of Illinois Optical and Discharge Physics CFDRC_0503_05

  5. SURFACE REACTION MECHANISM - ETCH • CFx and CxFy radicals are the precursors to the passivation layer which regulates delivery of precursors and activation energy. • Chemisorption of CFx produces a complex at the oxide-polymer interface. 2-step ion activated (through polymer layer) etching of the complex consumes the polymer. • Activation scales as  1/L and the L scales as  1/bias. • In Si etching, CFx is not consumed, resulting in thicker polymer layers. • Si reacts with F to release SiFx. University of Illinois Optical and Discharge Physics AVS03_AS_05

  6. SURFACE REACTION MECHANISMS - STRIP • Ar/O2 is typically used for polymer stripping after fluorocarbon etching and resist removal. • Little polymer removal is observed in absence of ion bombardment suggesting ion activation. • For SiO2 etching in mixtures such C4F8/O2, the fluorocarbon polymer is treated as an organic. Resists are treated similarly. University of Illinois Optical and Discharge Physics AVS03_AS_06

  7. MONTE CARLO FEATURE PROFILE MODEL (MCFPM) • The MCFPM predicts time and spatially dependent profiles using energy and angularly resolved neutral and ion fluxes obtained from equipment scale models. • Arbitrary chemical reaction mechanisms may be implemented, including thermal and ion assisted, sputtering, deposition and surface diffusion. • Energy and angular dependent processes are implemented using parametric forms. • Mesh centered identity of materials allows “burial”, overlayers and transmission of energy through materials. University of Illinois Optical and Discharge Physics INTELTALK_AS_17

  8. MODELING OF POROUS SILICA • MCFPM may include “two phase” materials characterized by porosity and average pore radius. • Pores are incorporated at random locations with a Gaussian pore size distribution. Pores are placed until the desired porosity is achieved with/without interconnects. • Interconnected structures can be addressed. University of Illinois Optical and Discharge Physics AVS03_AS_07

  9. TYPICAL PROCESS CONDITIONS • Process conditions • Power: 600 W • Pressure: 20 mTorr • rf self-bias: 0-150 V • C4F8 flow rate: 40 sccm • The fluxes and energy distributions are obtained using the HPEM. University of Illinois Optical and Discharge Physics AVS03_AS_08

  10. BASE CASE ION AND NEUTRAL FLUXES • Self-bias = - 120 V. Decrease in neutral and ion fluxes along the radius have compensating effects. • Ions have a narrow energy and angular distribution, in contrast to neutrals. University of Illinois Optical and Discharge Physics AVS03_AS_09

  11. VALIDATION OF REACTION MECHANISM: C4F8 • The mechanism was validated with experiments by Oehrlein et al using C4F8, C4F8/Ar and C4F8/O2.1 • Threshold for SiO2 etching was well captured at self-bias  -40 V. Polymer formation is dominant until the threshold bias • As polymer thins at higher biases, the etching proceeds. 1 Li et al, J. Vac. Sci. Technol. A 20, 2052, 2002. University of Illinois Optical and Discharge Physics AVS03_AS_10

  12. VALIDATION: C4F8/Ar and C4F8/O2 • Larger ionization rates result in larger ion fluxes in Ar/C4F8 mixtures. This increases etch rates. • With high Ar, the polymer layers thins to submonolayers due to less deposition and more sputtering and so lowers etch rates. • O2 etches polymer and reduces its thickness. Etch rate has a maximum with O2, similar to Ar addition. University of Illinois Optical and Discharge Physics AVS03_AS_11

  13. PROFILE COMPARISON: MERIE REACTOR V. Bakshi, Sematech • Process conditions • Power: 1500 W CCP • Pressure: 40 mTorr • Ar/O2/C4F8: 200/5/10 sccm University of Illinois Optical and Discharge Physics AVS03_AS_12

  14. VALIDATION OF POROUS SiO2 ETCH MODEL • Two porous substrates • 2 nm pore radius, 30% porosity • 10 nm pore radius, 58% porosity • Process conditions • Power: 1400 W (13.56 MHz) • Pressure: 10 mTorr • rf self-bias: 0-150 V • 40 sccm CHF3 • Etch rates of P-SiO2 are higher than for NP-SiO2 due to lower mass densities of P-SiO2. Exp: Oehrlein et al, J. Vac. Sci.Technol. A 18, 2742 (2000) University of Illinois Optical and Discharge Physics AVS03_AS_13

  15. WHAT CHANGES WITH POROUS SiO2? • The “opening” of pores during etching of P-SiO2 results in the filling of the voids with polymer, creating thicker layers. • Ions which would have otherwise hit at grazing or normal angle now intersect with more optimum angle. • An important parameter is L/a (polymer thickness / pore radius). • Adapted: Standaert, JVSTA 18, 2742 (2000) University of Illinois Optical and Discharge Physics INTELTALK_AS_30

  16. EFFECT OF PORE RADIUS ON HAR TRENCHES 4 nm 10 nm 16 nm • With increase in pore radius, L/a decreases causing a decrease in etch rates. • Thicker polymer layers eventually lead to mass corrected etch rates falling below NP-SiO2. There is little variation in the taper. University of Illinois Optical and Discharge Physics AVS03_AS_15

  17. HAR PROFILES: INTERCONNECTED PORES 100% 0% 60% Interconnectivity University of Illinois Optical and Discharge Physics INTELTALK_AS_40

  18. EFFECT OF PORE RADIUS ON CLEANING • Larger pores are harder to clean due to the view angle of ion fluxes. • Unfavorable view angles lead to a smaller delivery of activation energy, hence lower activated polymer sites. 4 nm 16 nm • Ar/O2=99/1, 40 sccm, 600 W, 4 mTorr University of Illinois Optical and Discharge Physics ANIMATION SLIDE AVS03_AS_17

  19. CLEANING INTERCONNECTED PORES • Cleaning is inefficient with interconnected pores. • Higher interconnectivity leads to larger shadowing of ions. 0% 60% 100% • Ar/O2=99/1, 40 sccm, 600 W, 4 mTorr Interconnectivity University of Illinois Optical and Discharge Physics ANIMATION SLIDE CHEME_AS_19

  20. EFFECT OF ASPECT RATIO ON STRIPPING • Cleaning decreases with increasing aspect ratios. • Pores at the top of the trench are stripped better due to direct ions (view angle). • Pores near the bottom see ions reflected from the bottom of the trench and are cleaned better. 1 3 Aspect Ratio 5 • Ar/O2=99/1, 40 sccm, 600 W, 4 mTorr University of Illinois Optical and Discharge Physics ANIMATION SLIDE AVS03_AS_19

  21. EFFECT OF PORE RADIUS ON Cu DEPOSITION • Larger pores require longer deposition times for conformal coverage. • This produces thicker bottom and open field films. • Voids are created or initiated by larger pores. NP 4 nm 10 nm 16 nm • Surrogate study for seed layer deposition and barrier coating. University of Illinois Optical and Discharge Physics AVS03_AS_20

  22. EFFECT OF INTERCONNECTIVITY ON Cu IMPVD • Interconnected pores need to be sealed to avoid pin-hole formation. • Pore sealing by Cu IMPVD ineffective at larger interconnectivities. • Thicker layers to seal pores produces trench narrowing, which can lead to pinch off. 0% 30% 60% 100% Interconnectivity University of Illinois Optical and Discharge Physics AVS03_AS_21

  23. CONCLUSIONS • Etching of PS obeys scaling laws as that of SS. Etch rate increases for smaller pores and slows for larger pores (at high porosities). • L/a determines etch rate variation of P-SiO2. Polymer filling increases the net thickness. • Stripping is inefficient for interconnected pore networks and for larger pores due to the unfavorable view angles for the ion fluxes. Low aspect ratio pores are better cleaned. • Cu IMPVD is non-conformal for closed pore networks with larger pores. Pin-hole formation and trench narrowing is seen for interconnected networks. University of Illinois Optical and Discharge Physics AVS03_AS_22

More Related