▪ Abstract The transition to copper-based interconnects for sub-quarter-micron device technologies has generated significant challenges in the identification and development of the robust material and process technologies required to form reliable multilevel metallization interconnects. In particular, a critical need exists for the identification and development of diffusion barrier/adhesion promoter liner materials that provide excellent performance in preventing the diffusion and intermixing of copper with the adjacent dielectric and semiconductor regions of the computer chip. This review summarizes key technology trends in interconnect metallization, with emphasis on ultrathin liner materials, predominant diffusion mechanisms in liner materials, and most promising candidate liners for copper metallization. Key results are presented from the development of physical vapor deposition and chemical vapor deposition processes for binary refractory metal nitrides, such as tantalum nitride and tungsten nitride...

Ultrathin Diffusion Barriers/Liners for Gigascale Copper Metallization

A method for forming a tungsten-containing copper interconnect barrier layer (e.g., a tungsten [W] or tungsten-nitride [WxN] copper interconnect barrier layer) on a substrate with a high (e.g., greater than 30%) sidewall step coverage and ample adhesion to underlying dielectric layers. The method includes first depositing a thin titanium-nitride (TiN) or tantalum nitride (TaN) nucleation layer (12) on the substrate, followed by the formation of a tungsten-containing copper interconnect barrier layer (20) (e.g., a W orWxN copper interconnect barrier layer) overlying the substrate. The tungsten-containing copper interconnect barrier layer can, for example, be formed using a Chemical Vapor Deposition (CVD) technique that employs a fluorine-free tungsten-containing gas (e.g., tungsten hexacarbonyl [W(CO)6]) or a WF6-based Atomic Layer Deposition (ALD) technique. The presence of a thin TiN (or TaN) nucleation layer facilitates the formation of a tungsten-­containing copper interconnect barrier layer with a sidewall step coverage of greater than 30% and ample adhesion to dielectric layers. A copper interconnect barrier layer structure includes a thin titanium-nitride (TiN) (or tantalum nitride [TAN]) nucleation layer disposed directly on the dielectric substrate (e.g., a single or dual-damascene copper interconnect dielectric substrate). The copper interconnect barrier layer structure also includes a tungsten-­containing copper interconnect barrier layer (e.g., a W or WxN copper interconnect barrier layer) formed on the thin TiN (or TaN) nucleation layer using, for example, a CVD technique that employs a fluorine-free tungsten-containing gas (e.g., [W(CO)6]) or a WF6-based ALD technique.

Copper interconnect barrier layer structure and formation method

CVD and precursor chemistry of transition metal nitrides

Applications of inorganic thin films in the electronics industry have spurred activity in the area of chemical vapor deposition (CVD). This article discusses the increasingly sophisticated design strategies for precursor complexes through a series of case studies on CVD of metal oxide and metal nitride films.

Design of precursors for the CVD of inorganic thin films.

Tungsten nitride (WNx) thin films were deposited by reactively sputtering a pure W target in an argon/nitrogen atmosphere. The nitrogen concentration in the growth chamber was varied from 2% to 60%. Film growth and properties were studied as a function of nitrogen concentration in the films. The cathode current and voltage variations during the film growth indicated cathode poisoning when the nitrogen concentration in the chamber was in the range of 2%–5%. This poisoning was accompanied by a reduced film growth rate. However, both the cathode current and deposition rate decrease were small due to the low resistivity and similar sputter yield of the WNx phase formed at the surface of the target and pure W. X-ray photoelectron spectroscopy analyses showed that the films were composed of ∼33 at. % nitrogen when the nitrogen concentration in the chamber was greater than 10%. X-ray diffraction (XRD) analysis confirmed that the films were predominantly W2N with the characteristic (111) peak at 2θ=37.7°. Slight ...

Reactive sputter deposition of tungsten nitride thin films

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...

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

Work by the present investigators has focused on the growth of HTS films on technologically useful substrates for energy‐related and cryoelectronic applications. In this paper, results from two such studies are presented: (1) Temperature‐controlled chemical vapor deposition (TC‐CVD) processing was used to grow YBa2Cu3O7−δ (YBCO) thin films directly on sapphire substrates. Films were grown by employing a three‐step substrate temperature ramping scheme: first, film was deposited at 730 °C for 5 minutes; then the substrates were heated up to 825 °C rapidly and held at that temperature for 5 minutes with no deposition; and finally the film was deposited for 10 more minutes using the substrate temperature ramping from 825 °C to 730 °C. The films were characterized utilizing dc transport four point measurements, and scanning electron microscopy (SEM). These measurements showed the film of highly c‐axis oriented with Tc around 90K. It is postulated the intermediate high deposition temperature helps to form a hig...

Vapor phase processing of HTS films for technological application

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

Vapor phase processing of HTS films for technological application