Jason W. Klaus

Al3O3 thin film growth on Si(100) using binary reaction sequence chemistry

Al2O3 films with precisely controlled thicknesses and excellent conformality were grown on Si(100) at low temperatures of 350–650 K using sequential surface chemical reactions. This controlled deposition was achieved by separating a binary reaction for Al2O3 chemical vapor deposition (2Al(CH3)3 + 3H2O → Al 2O3 + 6CH4) into two half-reactions:(A)A1OH*+A1(CH3)3→A1OA1(CH3)2*+CH4(B)A1CH3*+H2O→A1OH*+CH4 In the above reactions, the trimethylaluminum [Al (CH3)3] (TMA) and H2O reactants were employed alternately in an ABAB… binary reaction sequence where the asterisks designate the surface species. At the optimal reaction conditions, a growth rate of 1.1 A per AB cycle was measured on the Si (100) substrate using ellipsometry. These Al 2O3 films had an index of refraction of n= 1.65 and a corresponding density of ρ = 3.50 g cm−3. Additional ellipsometric measurements revealed that the Al2O3 deposition rate per AB cycle decreased at substrate temperatures >450 K. The decrease in the growth rate closely matched the thermal stability of the AlOH*and AlCH3* surface species previously measured with FTIR spectroscopy. This correlation supports a reaction mechanism based on self-limiting surface chemistry. Atomic force microscope images revealed that the deposited Al 2O3 films were exceptionally flat with a surface roughness of only ± 3 A (rms) after 500 AB cycles and the deposition of a film thickness of ∼ 560 A. The power spectra of the surface topography measured by AFM also demonstrated that the surface roughness was nearly identical for the initial Si(100) substrate and the deposited Al2O3 filmsafter 20–500 AB reaction cycles.

Atomic layer deposition of tungsten using sequential surface chemistry with a sacrificial stripping reaction

Tungsten (W) films were grown with atomic layer control using a novel sequence of self-limiting surface reactions. The tungsten film growth was achieved by dividing the binary reaction WF6+Si2H6→W+2SiHF3+2H2 into two separate half-reactions. Alternating exposures to WF6 and Si2H6 in an ABAB… sequence produced tungsten deposition at temperatures between 425 and 600 K. The Si2H6 reactant served only a sacrificial role to strip fluorine from tungsten without incorporating into the film. FTIR spectroscopic investigations demonstrated that the WF6 and Si2H6 half-reactions were complete and self-limiting at T>400 K. In situ spectroscopic ellipsometry measurements determined a tungsten growth rate of 2.5 A/AB cycle with WF6 and Si2H6 reactant exposures sufficient for complete half-reactions. The surface topography of the deposited tungsten films was flat indicating smooth film growth. The tungsten films were either amorphous or composed of very small crystalline grains and contained no measurable silicon or fluorine. These results represent the first demonstration of atomic layer deposition of smooth single-element metal films using sequential surface chemistry.

Atomically controlled growth of tungsten and tungsten nitride using sequential surface reactions

Abstract Thin films of tungsten (W) and tungsten nitride (W 2 N) were grown with atomic layer control using sequential surface reactions. Tungsten atomic layer deposition was accomplished by separating the reaction WF 6 +Si 2 H 6 →W+2SiHF 3 +2H 2 into two half-reactions. The tungsten nitride atomic layer growth was performed by dividing the reaction 2WF 6 +NH 3 →W 2 N+3HF+9/2F 2 into two half-reactions. Successive exposure to WF 6 and Si 2 H 6 (NH 3 ) in an ABAB… reaction sequence produced W (W 2 N) deposition at substrate temperatures between 425–600 K (600–800 K). The W deposition rate was 2.5 A/AB cycle for WF 6 and Si 2 H 6 reactant exposures >800 and 3000 L, respectively. The W 2 N deposition rate was also 2.5 A/AB cycle for WF 6 and NH 3 reactant exposures >3000 and 10,000 L, respectively. Atomic force micrographs of the deposited films on Si(100) were remarkably flat indicating smooth deposition. X-ray diffraction investigations revealed that the deposited tungsten and tungsten nitride films were either amorphous or composed of very small crystalline grains. X-ray photoelectron spectroscopy demonstrated that the films contained very low impurity concentrations. The results for tungsten represent the first demonstration of atomic layer deposition (ALD) of smooth single-element films using sequential surface reactions.

Atomic layer deposition of SiO2 using catalyzed and uncatalyzed self-limiting surface reactions

SiO2 thin films were deposited with atomic layer control using self-limiting surface reactions. The SiO2 growth was achieved by separating the binary reaction SiCl4+2H2O→ SiO2+4HCl into two half-re...

Atomic Layer Deposition of Tungsten Nitride Films Using Sequential Surface Reactions

Tungsten nitride films were deposited with atomic layer control using sequential surface reactions. The tungsten nitride film growth was accomplished by separating the binary reaction 2WF 6 + NH 3 → W 2 N + 3HF + 9/2F 2 into two half-reactions. Successive application of the WF 6 and NH 3 half-reactions in an ABAB... sequence produced tungsten nitride deposition at substrate temperatures between 600 and 800 K. Transmission Fourier transform infrared (FTIR) spectroscopy monitored the coverage of WF* x and NH y * surface species on high surface area particles during the WF 6 and NH 3 half-reactions. The FTIR spectroscopic results demonstrated that the WF 6 and NH 3 half-reactions were complete and self-limiting at temperatures ≥600 K. In situ spectroscopic ellipsometry monitored the film growth on Si(100) substrates as temperature and reactant exposure. A tungsten nitride deposition rate of 2.55 A/AB cycle was measured at 600-800 K for WF 6 and NH 3 reactant exposures ≥3000 L and 10,000 L, respectively, X-ray photoelectron spectroscopy depth-profiling experiments determined that the films had a W 2 N stoichiometry with low C and O impurity concentrations. X-ray diffraction investigations revealed that the tungsten nitride films were microcrystalline. Atomic force microscopy measurements of the deposited films observed remarkably flat surfaces indicating smooth film growth. These smooth tungsten nitride films deposited with atomic layer control should be useful as diffusion barriers for Cu on contact and via holes.

Atomic layer controlled growth of SiO2 films using binary reaction sequence chemistry

SiO2 thin films were deposited with atomic layer control using binary reaction sequence chemistry. The SiO2 growth was accomplished by separating the binary reaction SiCl4+2H2O→SiO2+4HCl into two half-reactions. Successive application of the half-reactions in an ABAB… sequence produced SiO2 deposition at temperatures between 600 and 800 K and reactant pressures of 1–10 Torr. The SiO2 growth was monitored using ellipsometry versus substrate temperature and reactant exposure time. The maximum SiO2 deposition per AB cycle was 1.1 A/AB cycle at 600 K. The surface topography measured using atomic force microscopy was extremely flat with a roughness nearly identical to the initial substrate.

Atomic layer controlled deposition of Al2O3 films using binary reaction sequence chemistry

Al2O3 films with precise thicknesses and high conformality were deposited using sequential surface chemical reactions. To achieve this controlled deposition, a binary reaction for Al2O3 chemical vapor deposition (2Al(CH3)3 + 3H2O → Al2O3 + 6CH4) was separated into two half-reactions: (A) AlOH∗ + Al(CH3)3 → AlOAl(CH3)2∗ + CH4, (B) AlCH3∗ + H2O → AlOH∗ + CH4, where the asterisks designate the surface species. Trimethylaluminum (Al(CH3)3) (TMA) and H2O reactants were employed alternately in an ABAB … binary reaction sequence to deposit Al2O3 films on single-crystal Si(100) and porous alumina membranes with pore diameters of ∼ 220 A. Ellipsometric measurements obtained a growth rate of 1.1 A/AB cycle on the Si(100) substrate at the optimal reaction conditions. The Al2O3 films had an index of refraction of n = 1.65 that is consistent with a film density of ϱ = 3.50 g/cm3. Atomic force microscope images revealed that the Al2O3 films were exceptionally flat with a surface roughness of only ±3 A (rms) after the deposition of ∼ 270 A using 250 AB reaction cycles. Al2O3 films were also deposited inside the pores of Anodisc alumina membranes. Gas flux measurements for H2 and N2 were consistent with a progressive pore reduction versus number of AB reaction cycles. Porosimetry measurements also showed that the original pore diameter of ∼ 220 A was reduced to ∼ 130 A after 120 AB reaction cycles.

Surface chemistry of In2O3 deposition using In(CH3)3 and H2O in a binary reaction sequence

Abstract Sequential surface chemical reactions for the controlled deposition of In2O3 were examined using transmission Fourier transform infrared (FTIR) spectroscopy. In this study, the binary reaction (2In(CH3)3+3H2O→In2O3+6CH4) was separated into two half-reactions: (A) InOH ∗ +In(CH 3 ) 3 →In–O–In(CH 3 ) ∗ 2 +CH 4 ; (B) InCH ∗ 3 +H 2 O→InOH ∗ +CH 4 , where the asterisks designate the surface species. The InOH* and InCH3* surface species were monitored by the infrared absorbances of the InO–H and InC–H3 stretching vibrations. The reactions were thermally activated and the maximum reaction temperature was limited to 525 K because of trimethylindium (TMIn) pyrolysis. At 525 K, the (A) reaction saturated after depletion of ∼60% of the InOH* coverage. In contrast, the (B) reaction went to completion and was self-limiting. Despite these observed surface reactions, the growth of conformal In2O3 films was not achieved on Si(100) at 525 K. Very rough In2O3 films with low growth rates were also observed at 675–775 K in previous studies using InCl3 and H2O in a binary reaction sequence. The thermal stabilities of the InOH* and InCH3* surface species were measured from 300–900 K. The low coverage of surface species at the various reaction temperatures may explain the rough In2O3 films and low In2O3 growth rates.