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The diffusion barrier properties of three different kinds of chemical vapor deposited (CVD) TiN films were compared against Cu. TiN(A) film (21 nm) was deposited by the thermal decomposition of a single source of tetrakis(dimethylamido)titanium at 400°C. TiN(B) film (19 nm) was prepared by in situ plasma treatment after every 8 nm growth of TiN(A) film. Finally, TiN(C) film (28 nm) was deposited by the reaction of with at 630°C. The densities of TiN(A), TiN(B), and TiN(C) films were 2.55, 4.04, and , respectively. Both TiN(A) and TiN(B) films showed nanocrystalline microstructure with equiaxed grains, the sizes of which were about 4 and 7 nm, respectively. TiN(C) film showed a columnar grain structure with an average grain size of about 14 nm. Sheet resistance measurements, X‐ray diffractometry analyses, and etch‐pit test results consistently demonstrated that the barrier performances of TiN(A) and TiN(B) were superior to those of TiN(C). The diffusion barrier properties of CVD TiN films were discussed in view of the density and microstructure of the film. © 1999 The Electrochemical Society. All rights reserved.

Ruthenium (Ru) thin films were grown on thermally-grown SiO 2 substrates by thermal atomic layer deposition (ALD) using a sequential supply of a zero metal valence precursor, isopropyl-methylbenzene-cyclohexadiene Ru(0) (IMBCHRu, C 16 H 22 Ru) and molecular oxygen (O 2 ) at substrate temperatures ranging from 185 to 310°C. The growth rate at 185°C was approximately 0.059 nm/cycle but its resistivity was >3000 μΩ cm. When the deposition was done at 200°C, the resistivity was decreased drastically to ∼100 μΩ cm, and the film growth rate increased to 0.075 nm/cycle. An ALD temperature window from 225 to 270°C was observed. A high growth rate of 0.086―0.089 nm/cycle was obtained at this ALD temperature window. The film deposited at 270°C showed a minimum resistivity of ∼30 μΩ cm and a high density of 11.7 g/cm 3 and with no impurities in the film, such as oxygen and carbon. At 310°C, the growth rate increased to 0.136 nm/cycle due to a partial decomposition of the precursor. In addition, the film resistivity increased slightly to ∼40 μΩ cm with the incorporation of carbon and the formation of a less-dense film. The step coverage of the ALD-Ru film was dependent on the dimensions of the contact and deposition temperature. At the contact with an aspect ratio of ∼4.6 (top opening diameter: 80 nm), the step coverage was excellent irrespective of the deposition temperature. However, at the contact with an aspect ratio of ∼25, the step coverage of the film deposited at 310°C (or above ALD temperature window) was degraded, even though those prepared within ALD temperature window were ∼100%. Finally, ALD-Ru film was used successfully as a seed layer for Cu electroplating.

The effect of the Al distribution on the electrical properties of Al-doped ZnO (AZO) films deposited by atomic layer deposition (ALD) is investigated. In order to control the Al distribution, the pulsing time of trimethylaluminum (TMA) is varied from 2 (within an ALD window) to 0.1 s. As a result, the areal density of Al atoms incorporated in a single dopant layer decreases from 3.3 x 10 14 to 1.2 ×10 14 cm -2 . Hall measurements reveal that the minimum resistivity of the ALD-AZO films is decreased from 3.2 x 10 -3 to 1.7 ×10 -3 Ω cm as a result of reducing the TMA pulsing time from 2 to 0.1 s. This decrease is due to the obvious increase of the carrier concentration from 1.4 x 10 20 to 4.7 x 10 20 cm -3 . It is suggested that both the improved doping efficiency (from 13 to 58%) and the insertion of more dopant layers within the ZnO matrix are responsible for the increase of the carrier concentration.

Ruthenium (Ru) thin films were successfully grown on the TiN substrate using plasma enhanced atomic layer deposition (PEALD) by using a zero metal valence precursor, IMBCHRu [(η6-1-Isopropyl-4-MethylBenzene)(η4-CycloHexa-1,3-diene) Ruthenium(0)] and direct plasma of ammonia (NH 3 ) as a reactant at the substrate temperature ranging from 140 and 400°C. The wide atomic layer deposition (ALD) temperature window from 225 to 400°C was shown and a high growth rate of 0.094 nm/cycle at the ALD temperature window was obtained, which is twice that of PEALD Ru results deposited by Cp (Cyclopentaldienyl)-based Ru precursors previously reported. No incubation cycle for the growth on the TiN underlayer was observed, indicating the fast nucleation of Ru. The PEALD-Ru films formed polycrystalline and columnar grain structures with a hexagonal-close-packed phase that was confirmed by X-ray diffractometry and transmission electron microscopy analysis. Its resistivity was dependent on the microstructural features characterized by grain size and crystallinity as well as its density, which could be controlled by varying the deposition parameters such as deposition temperature and reactant pulsing condition. Resistivity of ∼12 μΩ cm was obtained at the deposition temperature as low as 225°C by optimizing (NH 3 ) plasma power and pulsing time.

We report on the deposition properties of W nucleation layers prepared using a sequential supply of B 2 H 6 and WF 6 and their effects on the growth of the subsequent chemical vapor deposited (CVD)-W. The structural properties of the W nucleation layers such as their phase, crystallinity, and grain size depended on the deposition temperature, B 2 H 6 flow rate, and B 2 H 6 pulsing time. The formation of an amorphous and two forms of crystalline W film [primitive cubic p-phase and body-centered-cubic (bcc) α-one] was observed, depending on the deposition temperature. X-ray diffractometry and transmission electron microscopy diffraction analysis showed that the amorphous W was dominantly deposited at temperatures of up to 350°C and that when the deposition temperature was increased to 395°C, the film formed the p-phase. At a deposition temperature of 425°C, the phase of the film started to be transformed into α-phase and was completely transformed to single phase α-W with a very large grain size of approximately 120-180 nm at 450°C. We were also able to deposit the α-phase W film at 395°C with a lower B 2 H 6 flow rate, but its grain size was only approximately 20-30 nm. The W nucleation layers had a significant effect on the final grain size and resistivity of the CVD-W films deposited on them. The minimum resistivity of the 50 nm thick CVD-W film with the optimized B 2 H 6 -based nucleation layer was ∼ 10 μΩ cm, while the conventional CVD-W film with a SiH 4 -based nucleation layer showed a resistivity of 25 μΩ cm at the same thickness.

Diffusion barrier performances of atomic layer deposited (ALD)-Ru thin films between Cu and Si were improved with the use of an underlying 2 nm thick ALD-TaCN interlayer as diffusion barrier for the direct plating of Cu. Ru was deposited by a sequential supply of bis(ethylcyclopentadienyl)ruthenium [Ru(EtC p ) 2 ] and NH 3 plasma and TaCN by a sequential supply of (NEt 2 ) 3 Ta = Nbu t (tert-butylimido-trisdiethylamido-tantalum), and H 2 plasma. Sheet resistance measurements, X-ray diffractometry, and Auger electron spectroscopy analysis showed that the bilayer diffusion barriers of ALD-Ru (12 nm)/ALD-TaCN (2 nm) and ALD-Ru (4 nm)/ALD-TaCN (2 nm) prevented the Cu diffusion up to annealing temperatures of 600 and 550°C for 30 min, respectively. This is because of the excellent diffusion barrier performance of the ALD-TaCN film against the Cu, due to its amorphous structure. A 5 nm thick ALD-TaCN film was even stable up to annealing at 650°C between Cu and Si. Transmission electron microscopy investigation, combined with energy-dispersive spectroscopy analysis, revealed that the ALD-Ru/ALD-TaCN diffusion barrier failed by the Cu diffusion through the bilayer into the Si substrate. This is due to the ALD-TaCN interlayer preventing the interfacial reaction between the Ru and Si.

Tungsten nitride (WN x ) thin films were grown by atomic layer deposition (ALD) within the temperature range of 200-350°C from diborane (B 2 H 6 ), tungsten hexafluoride (WF 6 ), and ammonia (NH 3 ) for application to a contact barrier layer in dynamic random access memory (DRAM). Herein, B 2 H 6 was used as an additional reducing agent to produce a low-resistivity ALD-WN x film, and its resistivity was in the range of 300-410 μΩ cm, depending on the deposition conditions for the ∼ 10 nm thick film. An increase in the growth rate was observed with increasing deposition temperature, but an almost constant growth rate of ∼0.28 nm/cycle was obtained in the temperature range from 275 to 300°C. The properties of the as-deposited film, including the resistivity, W/N ratio, density, B and F impurity content, and phase, were affected by the deposition temperature and B 2 H 6 flow rate during the process. As the deposition temperature and B 2 H 6 flow rate increased, the W/N ratio and film density increased and the impurity content decreased, leading to a reduction in the resistivity of the film. An increased W/N ratio was found to be favorable to the formation of a face-centered-cubic β-W 2 N phase. Excellent step coverage was obtained even on a 0.14 μm diameter contact hole with an aspect ratio of 16:1. The ALD-WN x film in this study was thermally stable to annealing at 800°C for 30 min, but after annealing at 900°C, it converted to body-centered-cubic α-W with the accompanying release of N. The ALD-WN x film was evaluated as a barrier layer for W-plug deposition for 70 nm design-rule DRAM. The results showed that the integration scheme with ALD-WN x showed lower contact resistance than metallorganic chemical vapor deposition TiN or TiCl 4 -based chemical vapor deposited TiN.

The properties of three different kinds of atomic-layer-deposited (ALD) W thin films were comparatively characterized and investigated as nucleation layers for the W-plug process of 70 nm design-rule dynamic random access memory. ALD-W (A) film was deposited using alternating exposures of WF 6 and SiH 4 and ALD-W (B) film was treated with B 2 H 6 for 5 s prior to W ALD using WF 5 and SiH 4 . Finally, ALD-W (C) film was deposited using alternating exposures of WF 6 and B 2 H 6 . All the ALD-W films showed excellent step coverage at the contact with an aspect ratio of ∼ 14, but their resistivities were as high as 125-145 μΩ cm at the thickness of 20 nm. High resistivities of ALD-W films are discussed on the basis of impurities cooperation such as Si and B, phase (body-centered-cubic α-W or primitive cubic β-W), crystallinity (crystalline or amorphous), and grain size. It was found that ALD-W (C) film formed an amorphous phase, which was stable until 900°C annealing. This is clearly different from ALD-W (A) and ALD-W (B) with polycrystalline grains of α-W and β-W, and β-W was transformed to α-W after 800°C annealing. The formation of amorphous W resulted in the formation of large-size grains of chemical-vapor-deposited W film deposited on ALD-W (C) and the reduction in the resistivity of W-plug stack. The integration results showed that the reduced resistivity of W-plug stack with ALD-W (C) provided a significantly lower resistance at the W bit line contact. Another advantage of the integration scheme with ALD-W (C) was its stable contact resistance at the ultrahigh aspect ratio (UHAR) contact even though the step coverage of the underlayer, TiN, was poor. It was also found that the B 2 H 6 pretreatment was effective for obtaining the low and stable contact resistance at UHAR contact.

Tungsten (W) thin films were deposited using a modified chemical vapor deposition (CVD) process, called pulsed CVD, and the film properties were characterized as nucleation layers for a W-plug fill process. In this study,the deposition stage is composed of four steps, resulting in one deposition cycle: (i) reaction of WF 6 with SiH 4 , (ii) inert gas purge, (iii) SiH 4 exposure, and (iv) inert gas purge. The W growth per cycle was extremely linear with a growth rate of ∼ 1.32 nm/cycle at 400°C. The growth rate was further enhanced to 1.5-1.9 nm/cycle by increasing the SiH 4 flow rate in the first step and/or by adding H 2 in the first and the third steps. The W film deposited by pulsed CVD showed a much lower roughness (∼0.7 nm) and a better conformality at the contact holes with an aspect ratio of 14, compared to W films deposited by conventional CVD using WF 6 and SiH 4 . The film resistivity was closely related with its phase (body-centered cubic α-W or primitive cubic β-W) and microstructure characterized by grain size as well as the film thickness (the "size effect"). Transmission electron microscopy analysis showed that H 2 addition into the first and third steps increased the grain size from ∼7 to ∼13 nm and prevented the film from forming a β-W phase with high resistivity, resulting in a lower resistivity of 100 Ω-cm compared to that of the W film deposited without H 2 addition (210 μΩ-cm). H 2 addition was also effective in reducing the F and Si impurities in the films. Finally, the film resistivity was discussed on the basis of impurity, roughness, microstructure, and film phase.

Titanium nitride (TiN) films were deposited using tetrakis(dimethylamido)titanium (TDMAT) as a precursor. During film growth, N- and Ar-ion beams with an energy of 120 eV were supplied in order to improve the film quality. The films deposited using a N-ion beam showed a resistivity of about 320 μΩ cm and density of 4 g/cm 3 . The use of the N-ion beam, however, drastically degraded the step coverage of the film (below 5% at the 0.5 × 1.5 μm contact). The films deposited using an Ar-ion beam showed a resistivity of about 800 μΩ cm and density of 3.2 g/cm 3 . The step coverage measured at the same contact was around 30%. For comparison, the thermally decomposed film showed a resistivity of about 5800 μΩ cm and density of 2.5 g/cm 3 . Finally, the diffusion barrier properties of 50 nm thick TiN films for Cu were investigated by the etch-pit test. The films deposited using N- and Ar-ion beam failed after annealing at 600 and 650°C for 1 h, respectively, while thermally decomposed films failed at temperatures as low as 500°C. It is thought that the improvements of the diffusion barrier performance of the films deposited using a N- and Ar-ion beam are the consequence of the film densification resulting from ion bombardment during film growth.