U T JOHN G. EKERDT RESEARCH THEMES Using the tools of surface science we seek to develop and understand reaction chemistry and reaction kinetics at the surfaces and interfaces of electronic materials. RESEARCH INTERESTS Silicon-alloy nanoparticle (dots, wires, huts) growth. Organometallic and hydride precursor reaction kinetics. Growth of metal, multi-metal and organic thin films. Barrier materials and interface chemistry.

U T Representative Experimental System

U T Seeding in Parallel or Before Growth to Manage Nucleation Separate from Growth -- Now it is on to Precise Positioning Densities >10 12 STM 1.7  cm nm 1.1  A: 600 °C, 1.8 ML SEM 5 nm Zhu et al., J Appl Phys 92, (2002). HfO 2 SiO 2 1. Sacrificial mask definition HfO 2 SiO 2 2. Deposit seed atoms HfO 2 SiO 2 3. SiO desorption HfO 2 SiO 2 4. Defined growth

U T Site Specific Nucleation and Growth Si 2 H 6 SiH 3 3H 2 Si OH Si O Al 2 O 3 TiO 2 ZrO 2 HfO 2 MgO SiO 2

U T Cu-Diffusion Barriers for ULSI Interconnect Production year MPU 1/2 pitch (nm) Barrier thickness (nm) 1055 [1] International Technology Roadmap for Semiconductors 2002 Update, (2002). [2] International Technology Roadmap for Semiconductors 1999 Edition, (1999). Manufacturable Solutions: Known NOT Known A barrier layer (generally refractory metals and metal nitrides) must be employed to separate Cu from physical contact with other interconnect materials. ULSI Interconnect  Diffusion and electromigration resistance  Good adhesion  Low electrical resistivity (~100 μΩcm)  Deposition Good step coverage Barrier Requirements

U T TaF 5 and Si 2 H 6 Half-reactions on Ta Examine growth regime mechanisms Precursor adsorption and reaction on Ta in UHV Surface analysis techniques: XPS, SIMS, TPD Goal and Approach:  Half-reactions should enable ALD on an established film  Si may be incorporated  Not all F removed Conclusions: SIMS: TaF 5 dissociatively adsorbs on Ta Extent  with T Supports Si-F bonding TaF 5 half-rxn SiH x F y TaF x F Si 2 H 6 half-rxn SiH x F y TaSi x H y 523 K Lemonds et al., Surface Science 538 (2003) 191.

U T Film Growth via the TaF 5 /Si 2 H 6 Chemistry Employ alternating delivery of TaF 5 and Si 2 H 6 to achieve ALD growth Goal and Approach: T sample 300  C TaF 5 vapor at 88  C Ar5 sccm Si 2 H 6 20 sccm, 4% in He TaF 5 1 s Ar purge6 s Pump3 s Si 2 H 6 10 s Pump10 s 2.5 nm film comp Ta39 at.% Si45 at.% F12 at.% O 3 at.%  TaO x F y int. reactions  Si inc. as alloy  230 nm films 190  ∙cm

U T Scaling Limit of a CVD Ru Film on Ta Intensity (a.u.) E/E 0 ORu Ta 0 nm 1.6 nm 2.5 nm ISS Binding Energy (eV) Ta 4f XPS After Ru CVD deposition on Ta As-deposited PVD Ta on Si  The minimum Ru film thickness to cover the Ta film surface was ~2.5 nm, as estimated by ISS and XPS Ta 4f peak attenuation. ISS E/E 0 = f(m 2 /m 1 ) E He + E0E0 Si(100) > 5 nm Ta Ru XPS h e-e- <6 nm  /  0 = f( /t) Si(100) > 5 nm Ta Wang, et al. Applied Physics Letters 84, (2004)

U T The Wettability of Cu on CVD Ru Film A > 5 nm PVD Ta film was deposited on Si substrate. A ~3.5 nm CVD Ru film was deposited on the Ta substrate. A ~0.3 nm PVD Cu film was deposited on Ru. ISS measurement showed only 0.3 nm Cu fully covered the Ru film surface. 3.5 nm Ru Ru Si(100) > 5 nm Ta Cu  Cu showed excellent wetting on a CVD Ru surface. ISS XPS Ru 3d

U T Thermal CVD of boron-based films Precursor selected: Dimethylamine Borane complex (DMAB) BH 3 NH(CH 3 ) 2 Commercially available Crystalline solid M.p. ~36  C BC x N y deposited at 360  C on patterned 0.17  m trench SiO 2 Reactive gases: Ammonia for N Ethylene for C We have developed a thermal CVD process that deposits amorphous boron-based (BC x N y ) films on SiO 2 at temperatures less than 400  C. N:BH 3 CH 3 H

U T TTF results for BCN compared to SiCN  Research BCN films appear to be as good as a commercial SiCN. Films grown and handled outside a cleanroom, which may contribute to the spread in measurements for BCN vs SiCN.  C 2 H 4 coreactant appears to improve barrier properties vs. NH 3

U T The SFIL Process Overview template etch barrier transfer layer release treatment UV Cure Dispense Expose Separate Imprint Breakthrough Etch Transfer Etch

U T Surface Treatment for SFIL Ensure selective release for SFIL Imprint Release -Organic self-assembled monolayers such as illustrated below -F- and B-doped diamond-like carbon films -Role of OH and M-O-M surface groups in interface bonding with etch barrier molecules and polymer film Reaction Particulars: -Degree of substrate hydroxylation -Degree of substrate hydration -Reactivity of hydroxyl groups -Reactivity of precursors - Trichloro- - Trialkoxy- - tris-Dimethylamino