Jeong Soo Byun

Epitaxial growth of CoSi2 layer on (100)Si and facet formation at the CoSi2/Si interface

The epitaxial nature of the CoSi2 formed on the (100)Si substrate as a result of annealing a Co/Ta bilayer at 500–1000 °C for 20 s in N2 atmosphere is described. At the early stage of annealing, diffusion of Co and Si occurs across the interlayed Ta layer, first forming a CoSi layer on the Si substrate. After that, CoSi2 grains nucleate at the CoSi/Si interface and grow laterally parallel to the surface. Due to a difference in mobility the CoSi2 grains at the interface of the CoSi/Si impede the interface movement, leading the facet formation. Even after annealing below 600 °C, the epitaxial CoSi2 grains are nucleated at the limited area of the nonepitaxial CoSi/Si interface and the faceted corner, and grow laterally along the Si surface. By increasing the annealing temperature, the epitaxiality of CoSi2 improves due to the increased lateral growth rate of the CoSi2. However, annealing above 900 °C impairs the CoSi2 crystallinity because the interlayered Ta loses its function as a diffusion barrier due to ...

The effect of substrate temperature on the composition and growth of tantalum oxide thin films deposited by plasma-enhanced chemical vapour deposition

Tantalum oxide (Ta2O5) thin films were deposited on silicon substrates by plasma-enhanced chemical vapour deposition using tantalum ethylate (Ta(C2H5O)5) and nitrous oxide (N2O). The growth rate of the tantalum oxide thin films showed Arrhenius behaviour and the apparent activation energy was 3.75 kcal mol−1. The composition of tantalum oxide, determined from Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy analyses, showed a dependence on the substrate temperature. The refractive index of the tantalum oxide thin films measured by ellipsometry showed a strong relation to the composition of thin films, However, the growth rate and composition of the thin films were somewhat independent of the r.f. input power. The deposition behaviour of tantalum oxide films was regarded as the competitive reaction between the tantalum-containing species and oxidant species on the silicon substrate surface. The structure of the deposited films was amorphous, but it changed to a polycrystalline structure after annealing at 900°C in a N2 ambient. The electrical properties of the deposited films were also characterized by capacitance-voltage and current-voltage characteristics.

Epitaxial growth of CoSi2 on Si wafer using Co/Ta bilayer

A CoSi2 epitaxial layer was grown by thermal annealing of Co/Ta bilayer on a Si(100) wafer in the NH3 ambient. During thermal annealing an intermediate Ta layer between a Co layer and a Si wafer played two important roles for epitaxial growth of CoSi2. One was a reduction of a native oxide on a Si substrate, which resulted in an atomically clean Si surface. The other was a limitation of a flux of Co atoms to the Si surface, which made CoSi2 the most stable phase among several cobalt silicide ones. Both roles of the Ta layer made it possible to produce an epitaxial layer of CoSi2 with a coherent interface with a Si substrate, even at the early stage of thermal annealing.

TiN/TiSi2 Formation Using TiNx Layer and Its Feasibilities in ULSI

A new technique for the formation of the TiN/TiSi2 bilayer using a TiNx layer was described. The TiNx layer was deposited by sputtering in a mixed gas atmosphere of argon and nitrogen, wherein the concentration of nitrogen was controlled to be lower than that required in the formation of stoichiometric TiN. The nitrogen atoms in the Ti matrix relaxed the mechanical stress of the deposited film and also limited the number of Ti atoms available for the interaction with the Si substrate (i.e., silicidation reaction). Upon thermal annealing, TiNx changed to the bilayer structure of TiN/TiSi2, in which the thickness of the overlying TiN was so great that only a rather thin TiSi2 was formed between TiN and the Si substrate. Moreover, TiN had the (111) texture, and TiSi2 formed on the (100)Si substrate was found to show well-aligned epitaxial properties with an extremely uniform thickness.

Layer Reversal of Co/Zr Bilayer and Epitaxial Growth of CoSi2 Layer on Si(001) Substrate

The layer reversal phenomenon of the cobalt/zirconium (Co/Zr) bilayer during rapid thermal annealing (RTA) and the epitaxial growth of a cobalt disilicide (CoSi 2 ) layer have been investigated. The interlayed Zr layer effectively limited the flux of Co atoms by forming the Co-Zr intermediate phase and the Zr-O (or Zr-N) compound as well as effectively removing the native oxide formed on the Si substrate which interferes with the direct Co-Si interaction. Below 600°C, the Co-Zr intermediate alloy with ZrO 2 (i.e., Co-Zr-O) were formed without any silicide formation of cobalt. However, the layer reversal occurred after RTA above 700°C, resulting in the epitaxial CoSi 2 formation on (001) Si substrate. The CoSi 2 layer improved with increasing temperature, so that both the interface of the Zr-Co-Si alloy layer/CoSi 2 and the CoSi 2 /Si were extremely smooth after RTA at 900°C.

Formation of a large grain sized TiN layer using TiNx, the epitaxial continuity at the Al/TiN interface, and its electromigration endurance in multilayered interconnection

A new technique on the formation of TiN film with large grain size from TiNx is described. The TiNx layer (defined in Sec. II A) was deposited by sputtering in argon and nitrogen. The nitrogen atoms in Ti matrix relaxed the mechanical stress of the deposited film and limited the surface mobility during the deposition process, resulting in a nanocrystalline structure with extremely uniform thickness. After rapid thermal annealing (RTA), the TiNx yielded a bilayer structure of TiN/TiSixOy, in which the TiN showed (111) preferred texture, extremely smooth surface, and large grain size without any columnar structure. In addition, the resistivity of the bilayered TiN was as low as 40 μΩ cm. In the TiN multilayered aluminum structure (i.e., TiN/Al/TiN), epitaxial continuity and the intermetallic compound such as TiAl3 were clearly observed at the aluminum/TiN interface. The multilayered structure showed better endurance against EM in comparison with the same structure using the conventional TiN (also defined in...

Layer sequence and silicide formation of a Co/(refractory metal) bilayer on (100)Si substrate

The solid state reactions of bilayer systems, such as Co/Cr and Co/V, with a silicon substrate have been investigated. The layer sequence could be explained in terms of competitive relations between the diffusion of cobalt atoms toward the substrate and the surface reaction (i.e., silicide formation at the silicon substrate). It was also found that the intermixing between the cobalt and the refractory beneath it is related to the solid solubility between them, and the layer reversal phenomenon critically depends on the silicide formation temperature of the interlayer refractory metal. For example, in the Co/Cr bilayer, where the silicide formation temperature of the chromium is not higher than that of the cobalt, only a partial layer reversal occurs. However, in the Co/V bilayer, where vanadium has a higher silicide formation temperature than cobalt, a complete layer reversal occurs.

Effect of NH3 thermal treatment on an atomic layer deposited on tungsten films and formation of W–B–N

The effect of ammonia (NH3) ambient annealing on a tungsten (W) film deposited by atomic layer deposition at temperatures ranging from 400–700 °C is discussed. The as-deposited film contains approximately 20 at. % of boron which is chemical bound to W (W–B) having a resistivity of 128 μΩ cm. The film has an amorphous structure, which does not transform into crystalline phase during annealing. As a result of annealing in NH3 ambient, a tungsten ternary phase (W–B–N) forms at the surface; its binding configuration depends on the annealing temperature. Below 500 °C, nitrogen is chemically bonded to tungsten (W–N) while maintaining a W–B bond. Above 600 °C, nitrogen-rich W–B–N forms, in which nitrogen atoms have chemical binding with boron (B–N) and tungsten (W–N). It was found that a film annealed at higher temperatures has a resistivity of 107 μΩ cm, and thermal desorption of boron and nitrogen containing species is not observed during the thermal process. In addition, tungsten oxide formed at the surface d...

Electrical properties of the p+-gate electrode of an a-Si/poly-Si double layer

Abstract The single and mixed p + -gate electrodes of a-Si and poly-Si layers were fabricated and analyzed by cross-sectional transmission electron microscopy, Raman, X-ray diffraction, secondary ion mass spectrometry and electrical measurements. The as-deposited a-Si layer, which transformed to a large grain polycrystalline structure during annealing, showed lower resistivity and less gate electrode-induced strain than the single poly-Si layer. The interface in the mixed layer of a-Si and poly-Si layers showed a discontinuity of grains of upper and lower layers. The mixed electrode layers on 80 A thick N 2 O oxide were implanted with BF 2 + at 30 keV and annealed at 900 °C to fabricate p + -gate MIS capacitors. The high frequency and quasi-static C - V measurements of the MIS capacitors showed the formation of a shallow p + -n junction in the Si substrate of MIS capacitors, caused by B and F atoms penetrating into the Si substrate through the ultrathin N 2 O gate oxide during annealing. However, the mixed layer including the a-Si layer partially restricted B penetration into the Si substrate during furnace annealing, and thus MIS capacitors with the mixed layer had better electrical properties, such as time dependent dielectric breakdown and charge trapping, than those with the single poly-Si electrode structure. This might be due to less B penetration into the oxide layer and relaxation of residual stress in gate electrodes owing to phase transformation of a-Si to poly-Si.