Barry C. Arkles

Tantalum Nitride Films Grown by Inorganic Low Temperature Thermal Chemical Vapor Deposition Diffusion Barrier Properties in Copper Metallization

Key findings are presented from a systematic study which evaluated the performance of chemical vapor deposited (CVD) nitrogen-rich tantalum nitride (TaN x , x ∼ 1.8) films as a diffusion barrier in copper (Cu) based metallization schemes. For this purpose, 3800 A thick Cu films were grown by physical vapor deposition (PVD) on 550 A thick TaN x films which were deposited by low temperature (<425°C) thermal CVD (TCVD) using tantalum pentabromide (TaBr 5 ), ammonia, and hydrogen as coreactants. The resulting stacks were annealed in argon ambient at 450, 500, 550, and 650°C for 30 min each, along with similar PVD Cu/PVD TaN x bilayers of identical thickness. Both types of pre- and postannealed stacks were characterized by X-ray photoelectron spectroscopy, Auger electron spectroscopy, Rutherford backscattering spectrometry, nuclear reaction analysis for hydrogen profiling, X-ray diffraction, stack sheet resistance measurements, and Secco chemical treatment and etch-pit observation by scanning electron microscopy. The resulting findings showed that the PVD TaN x films provided an excellent barrier against Cu diffusion throughout the annealing window investigated. Altematively, the TCVD TaN x films exhibited similar stability up to 550°C. Barrier failure occurred, however, at temperatures between 550 and 600°C, as revealed by the formation of etch pits after Secco etch treatment. The failure of the TCVD TaN x films could not be attributed to bromine incorporation, given that residual bromine (∼0.5 atom %) in the TCVD TaN x films was highly stable against thermal diffusion in the temperature window investigated. Instead, the higher thermal stability of the PVD TaN x was attributed to differences in film microstructure and crystalline phase, or the location of excess nitrogen within the film matrix.

Low temperature plasma-assisted chemical vapor deposition of tantalum nitride from tantalum pentabromide for copper metallization

In this article, the authors report the development of a new low temperature plasma-assisted chemical vapor deposition (PACVD) process for the growth of low resistivity, cubic tantalum nitride (TaNx) for incorporation as a diffusion barrier/adhesion promoter in emerging ultralarge-scale integrated (ULSI) multilevel metallization (MLM) schemes. TaNx films were produced in a low density plasma using tantalum pentabromide, hydrogen, and nitrogen as coreactants. The films were grown at substrate temperatures of 350–450 °C, reactor working pressures of 0.9–1.6 Torr, hydrogen flow rates between 250 and 1500 sccm, nitrogen flow rates of 100–600 sccm, and plasma power ranging from 10 to 60 W, corresponding to a power density of 0.06–0.33 W/cm2. The films were subsequently characterized by Auger electron spectroscopy, Rutherford backscattering spectrometry, x-ray diffraction, atomic force microscopy, four-point resistivity probe, and cross-sectional scanning electron microscopy. These studies indicated that the Ta...

The Effects of Processing Parameters in the Chemical Vapor Deposition of Cobalt from Cobalt Tricarbonyl Nitrosyl

This paper reports the development of a thermal chemical vapor deposition process for pure cobalt from the source precursor cobalt tricarbonyl nitrosyl for incorporation in integrated circuit silicide applications. Studies were carried out to examine the underlying mechanisms that control Co nucleation and growth kinetics, including the effects of key process parameters on film purity, texture, morphology, and electrical properties. For this purpose, systematic variations were implemented for substrate temperature, precursor flow, hydrogen reactant flow, and deposition time (thickness). Resulting films were analyzed by Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, X-ray diffraction, four-point resistivity probe, scanning electron microscopy, and atomic force microscopy. These investigations identified an optimized process window for the growth of pure Co with resistivity of 9 ± 2 μΩ cm, smooth surface morphology, and root-mean-square surface roughness at or below 10% of film thickness.

Low temperature metal-organic chemical vapor deposition of tungsten nitride as diffusion barrier for copper metallization

A metal-organic chemical vapor deposition process has been developed for the growth of amorphous tungsten nitride thin films for barrier layer applications in ultralarge scale integration copper interconnect schemes. The process employs tungsten hexacarbonyl, [W(CO)6] and ammonia (NH3) as, respectively, the tungsten and nitrogen sources. Tungsten nitride films were produced within a wide process window, including a substrate temperature of 200–350 °C, W(CO)6 flow rate of 1–20 sccm, reactor pressure of 0.2–0.5 Torr, and NH3 flow rates of 100–500 sccm. The films were analyzed by x-ray photoelectron spectroscopy, cross-section scanning electron microscopy, x-ray diffraction, transmission electron microscopy, four-point resistivity probe, and Rutherford backscattering spectrometry. These studies indicated that the films consisted predominantly of a W2N phase. Films were grown with carbon and oxygen concentrations ⩽5 at. %, even at the lowest processing temperature investigated, where precursor dissociation wo...

Barrier Properties of Titanium Nitride Films Grown by Low Temperature Chemical Vapor Deposition from Titanium Tetraiodide

Results are presented from a systematic study of the composition, texture, and electrical properties of titanium nitride (TiN) films and their performance as diffusion barrier in multilevel interconnect schemes of ultralarge scale integration (ULSI) computer chip device structures. The films were grown by low temperature (<450°C) inorganic chemical vapor deposition using titanium tetraiodide as source precursor and ammonia and hydrogen as co-reactants. The TiN films were nitrogen-rich., with iodine concentrations below 2 atom percent, displayed resistivities in the range 100 to 150 μΩ cm depending on thickness, and exhibited excellent step coverage with better than 90% conformality in both nominal 0.45 μm, 3:1 aspect ratio and 0.25 μm, 4:1 aspect ratio contact structures. A comparison of the properties of chemical vapor deposited (CVD) TiN with equivalent physical vapor deposited (PVD) TiN showed that reactivity with Al-0.5 a/o Cu alloys was equivalent in both cases. In particular, a 10% increase in the Al-Cu/TiN stack sheet resistance was observed for both types of TiN after a 450°C, 30 min sinter. Similarly, the characteristics of CVD tungsten and reflow plug fills were identical on both types of TiN films. However, barrier performance for CVD TiN in aluminum and tungsten plug technologies was superior to that of PVD TiN, as evidenced by lower contact diode leakage for CVD TiN in comparison with PVD TiN films of equal thickness. This improved barrier performance could be attributed to a combination of factors, which include the nitrogen-rich composition, higher density, and enhanced conformality of the CVD TiN phase in comparison with the PVD TiN. In view of the superior step coverage and diffusion barrier characteristics, the low temperature inorganic CVD route to TiN seems to provide an adequate replacement for conventional PVD TiN in emerging ULSI metallization interconnect schemes.

Interlayer Mediated Epitaxy of Cobalt Silicide on Silicon (100) from Low Temperature Chemical Vapor Deposition of Cobalt Formation Mechanisms and Associated Properties

This paper reports the development of methodology for the growth of epitaxial CoSi 2 that uses Co films deposited by low temperature (391°C) chemical vapor deposition (CVD) from cobalt tricarbonyl nitrisyl [Co(CO) 3 NO] as source precursor. This CVD process exploits the reaction kinetics associated with the adsorption and decomposition of Co(CO) 3 NO on Si surfaces to ensure the in situ, sequential growth of an ultrathin interfacial oxide layer followed by a Co thin film in a single deposition step. It is demonstrated that this interlayer, consisting of a Si-O or a Co-Si-O phase, inhibits silicidation for uncapped CVD Co regardless of annealing times and temperatures. Instead, Co agglomeration is observed, with the degree of agglomeration being proportional to the annealing temperature. The agglomeration is due to a reduction in the overall energy of the system through decrease of the Co/substrate interfacial area. Alternatively, for Ti/TiN capped CVD Co samples, the interfacial layer appears to play a role similar to that observed for similar layers in interlayer mediated epitaxy (IME). This assessment is supported by the observation of epitaxial CoSi 2 for capped CVD Co samples after a single-step anneal at 725°C for 30 s. In contrast, Ti/TiN capped PVD Co samples annealed under identical processing conditions exhibited a polycrystalline CoSi 2 phase with a strong (200) texture. As such, the methodology presented herein represents a modified IME technique for the growth of high quality, epitaxial CoSi 2 films for applications in emerging microelectronics device technologies.

Low temperature inorganic chemical vapor deposition of Ti–Si–N diffusion barrier liners for gigascale copper interconnect applications

A new low temperature inorganic thermal chemical vapor deposition process has been developed for the growth of titanium–silicon–nitride (Ti–Si–N) liners for diffusion barrier applications in ultralarge scale integration copper interconnect schemes. This process employs the thermal reaction of tetraiodotitanium (TiI4), tetraiodosilane (SiI4), and ammonia (NH3) as, respectively, the individual Ti, Si, and N sources. Ti–Si–N films were successfully grown over a broad range of deposition conditions, including wafer temperature, process pressure, and TiI4, SiI4, and NH3 flows ranging, respectively, from 350 to 430 °C, 0.1–1 Torr, and 2.5–8.0, 2.5–12.5, and 100–250 sccm. Film stoichiometry was tightly tailored through independent control of the Ti, Si, and N source flows. Film properties were characterized by x-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, transmission electron microscopy, scanning electron microscopy, x-ray diffraction, and four-point resistivity probe. Resulting find...

Low-temperature chemical vapor deposition of tantalum nitride from tantalum pentabromide for integrated circuitry copper metallization applications

A low-temperature (>450 °C) thermal chemical vapor deposition (CVD) process was developed for the growth of TaN x from the reaction of tantalum pentabromide, ammonia, and hydrogen. Studies of process reaction kinetics yielded two sequential rate-controlling steps, with an activation energy of 0.45 eV for the kinetically limited reaction regime. Additionally, a systematic design of experiments approach examined the effects of key process parameters, namely, substrate temperature, source temperature, and hydrogen and ammonia flows, on film properties. A wide CVD process window was established for nitrogen-rich amorphous TaN x with contamination below 1 at.%. Film conformality was higher than 95% in nominally 0.30 μm, 4.5: 1 aspect ratio, trench structures.

Low temperature plasma-promoted chemical vapor deposition of tantalum from tantalum pentabromide for copper metallization

A low temperature plasma-promoted chemical vapor deposition (PPCVD) process has been developed for the growth of tantalum (Ta) from the halide source tantalum pentabromide (TaBr5), using hydrogen as reducing agent, for incorporation in emerging integrated circuitry (IC) copper metallization schemes. Ta films were produced at substrate temperatures of 400–450 °C, reactor working pressures of 0.6–0.7 Torr, hydrogen carrier flow rate of 50 sccm, hydrogen reactant flow rates between 200 and 1200 sccm, and plasma power ranging from 20 to 100 W, corresponding to a power density of 0.11–0.55 W/cm2. The films were subsequently characterized by Auger electron spectroscopy (AES), Rutherford backscattering (RBS), x-ray diffraction (XRD), atomic force microscopy (AFM), four-point resistivity probe, scanning electron microscopy (SEM), and cross-section SEM. These studies indicated that the Ta films thus produced were carbon and oxygen free, contained bromine concentration below 2.5 at. %, and exhibited better than 75%...

Tantalum diffusion barrier grown by inorganic plasma-promoted chemical vapor deposition: Performance in copper metallization

As-deposited and annealed tantalum films, grown by plasma-promoted chemical vapor deposition (PPCVD) using pentabromotantalum and hydrogen as coreactants, were evaluated as diffusion barriers in copper metallization. Stacks consisting of 500-nm-thick sputtered Cu/55-nm-thick untreated PPCVD Ta/Si were annealed in argon in the range 450 to 650 °C, in 50 °C intervals, along with sputtered Cu/preannealed PPCVD Ta/Si and sputtered Cu/sputtered Ta/Si stacks of identical thickness. Preand postannealed stacks were characterized by x-ray photoelectron spectroscopy, Auger electron spectroscopy, Rutherford backscattering spectrometry, hydrogen profiling, x-ray diffraction, atomic force microscopy, sheet resistance measurements, and Secco chemical treatment and etch-pit observation by scanning electron microscopy. The sputtered and preannealed PPCVD Ta films acted as viable diffusion barriers up to 550 °C while the as-deposited PPCVD Ta films failed above 500 °C. In all cases, breakdown occurred through the migration of Cu into Si, rather than an interfacial reaction between Ta and Si, in agreement with previously reported results for sputtered Ta films. The accelerated barrier failure for as-deposited PPCVD Ta might have been caused by the presence of approximately 20 at. % hydrogen in the as-deposited PPCVD Ta, an observation which was supported by the enhanced performance of the same PPCVD Ta films after annealing-induced hydrogen removal.