A molecular dynamics study of 50 eV Ar ϩ ion bombardment of a Si͑100͒ crystal with a monolayer of adsorbed chlorine was conducted to simulate atomic layer etching ͑ALET͒ of Si. The total reaction yield ͑Si atoms removed per ion͒ was 0.172; 84% of silicon was removed as SiCl, 8% as elemental Si and 8% as SiCl 2. Based on the total yield, an ion dose of 1.16ϫ10 16 ions/cm 2 is necessary to remove one monolayer of silicon. Reaction occurs during the ps time scale of the ion-solid interaction. Long timescale chemistry ͑100s of ms͒ which is possible in ion-assisted etching with simultaneous exposure to neutral and ion beams does not happen in ALET. It was further found that 93% of Si originated from the top silicon layer and 7% from the layer underneath. In addition, some structural ''damage'' was induced to the top three silicon layers. It appears that perfect ALET of silicon is not possible for an ion energy of 50 eV.

dielectrics for future stackedcapacitor DRAM Thin films of barium-strontium titanate (Ba,Sr)TiO 3 (BSTO) have been investigated for use as a capacitor dielectric for future generations of dynamic random-access memory (DRAM). This paper describes progress made in the preparation of BSTO films by liquid-source metal-organic chemical vapor deposition (LS-MOCVD) and the issues related to integrating films of BSTO into a DRAM capacitor. Films of BSTO deposited on planar Pt electrodes meet the electrical requirements needed for future DRAM. The specific capacitance and charge loss are found to be strongly dependent on the details of the BSTO deposition, the choice of the lower electrode structure, the microstructure of the BSTO, the post-electrode thermal treatments, BSTO dopants, and thin-film stress. Films of BSTO deposited on patterned Pt electrodes with a feature size of 0.2 m are found to have degraded properties compared to films on large planar structures, but functional bits have been achieved on a DRAM test site at 0.20-m ground rules. Mechanisms influencing specific capacitance and charge loss of BSTO films are described, as are the requirements for the electrode and barrier materials used in stacked-capacitor structures, with emphasis given to the properties of the Pt/TaSi(N) electrode/barrier system. Major problems requiring additional investigation are outlined.

Effect of silicon substrate microroughness on gate oxide quality An experimental system and methodology were developed to realize dry etching of single crystal silicon with monolayer accuracy. Atomic layer etching of silicon is a cyclic process composed of four consecutive steps: reactant adsorption, excess reactant evacuation, ion irradiation, and product evacuation. When successful, completion of one cycle results in removal of one monolayer of silicon. The process was self-limiting with respect to both reactant and ion dose. Control of the ion energy was the most important factor in realizing etching of one monolayer per cycle.

Nearly stoichiometric silicon, germanium, and tin nitride thin films were deposited from the corresponding homoleptic dimethylamido complexes M ͑NMe 2 ͒ 4 ͑MϭSi, Ge, Sn; MeϭCH 3 ͒, and an ammonia plasma at low substrate temperatures ͑Ͻ400°C͒. Tin nitride films were also deposited from Sn ͑NMe 2 ͒ 4 and ammonia without plasma activation. The films showed little ͑Ͻfew at. %͒ or no carbon or oxygen contamination. The barrier properties of the silicon and germanium nitride films were evaluated by using backscattering spectrometry. Homoleptic dimethylamido silicon and germanium compounds are attractive alternatives to silane and germane for use in the plasma-enhanced chemical vapor deposition of nitride thin films.

Articles you may be interested inIon-surface interactions in low temperature silicon epitaxy by remote plasma enhanced chemical-vapor deposition J.Low temperature deposition of silicon nitride films by distributed electron cyclotron resonance plasmaenhanced chemical vapor deposition J. Vac. Sci. Technol. A 13, 2900 (1995); 10.1116/1.579609 Chemical vapor deposition of aluminum from dimethylaluminumhydride (DMAH): Characteristics of DMAH vaporization and Al growth kineticsNearly stoichiometric aluminum and gallium nitride thin films were prepared from hexakis͑dimethylamido͒dimetal complexes, M 2 ͓N͑CH 3 ) 2 ] 6 ͑MϭAl,Ga͒, and ammonia at substrate temperatures as low as 200°C by using low pressure thermal and plasma enhanced chemical vapor deposition ͑CVD͒. Both processes gave films that showed little or no carbon (Ͻ5 at. %͒ and no oxygen (Ͻfew at. %͒ contamination, but in all cases there was hydrogen incorporation. The films were highly transparent in the ultraviolet and visible regions. The barrier properties of the aluminum nitride films in a Si/AlN/Au metallization scheme were examined by using backscattering spectrometry. The growth rate of the aluminum nitride films was as high as 1300 Å /min. Overall, the results suggest that M 2 ͓N͑CH 3 ) 2 ] 6 ͑MϭAl,Ga͒ are promising precursors for low-temperature/ low-pressure thermal and plasma-enhanced CVD of group III nitride thin films.