As the microelectronics industry evolves into ultralarge scale integration (ULSI) device schemes, copper (Cu) appears to provide better performance as an interconnect material than the currently used aluminum (Al) alloys. In this respect, Cu offers lower resistivity and enhanced electromigration resistance than its Al counterpart. 1 Unfortunately, Cu is known to be highly reactive with and a fast diffuser in silicon. Its presence in silicon leads to the formation of deep trap levels, which severely degrade device performance. 2 Clearly, a critical issue in the realization of structurally stable copper-based metallization architectures is the development of an appropriate diffusion barrier which prevents undesirable interactions between Cu and the semiconductor and dielectric regions of the computer chip.In order to address this issue, various refractory metals and their binary nitrides, as well as ternary metal-silicon-nitrogen compounds, have been heavily examined. Of these materials, tantalum (Ta)-based compounds are considered perhaps among the most promising candidates. Tantalum and its nitrides are highly refractory materials that are stable to extremely high temperatures. 3 Additionally, they are known to be thermodynamically stable with respect to Cu, as documented by the absence of Cu-Ta or Cu-N compounds. This stability is supported by a large number of studies pertaining to the appropriateness of Ta compounds as copper diffusion barrier. For instance, a sputtered 50 nm thick Ta barrier has demonstrated its resistance to Cu diffusion up to 550ЊC for 1 h. 4 In this respect, tantalum nitrides could provide even higher resistance to diffusion as compared to the pure metal, because of their dense interstitial crystalline structure. 5 As a result, sputtered tantalum nitrides have been successfully shown to act as good diffusion barriers in Cu technology, with proven Cu-TaN contact stability to temperatures as high as 750ЊC. 2 Conventional forms of physical vapor deposition (PVD) of TaN x , including collimated sputtering, are inherently incapable of conformal step coverage in aggressive trench and via structures, given their "line of sight" type approach. Alternative processing techniques are thus required for producing Ta-based liners for incorporation in subquartermicron device technologies. In this respect, chemical vapor deposition (CVD) is one of the most promising techniques. CVD exhibits an intrinsic potential for conformal coverage, in view of the "catalytic" role that the substrate plays in the deposition reaction.Numerous CVD approaches have already been investigated for the growth of tantalum nitride. Inorganic CVD from tantalum pentachloride (TaCl 5 ) led to the deposition of tantalum nitride at temperatures above 600ЊC. 6 Clearly, this high processing temperature prohibits the use of this deposition methodology in actual semiconductor devices. Metallorganic CVD (MOCVD) approaches, on the other hand, included the use of various precursors such as the dialkylamido Ta complex, 7 Ta(NEt)(NEt 2 ) 3 /T...

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Using Fourier-transform infrared absorption spectroscopy, we have studied the Si–H stretch mode on hydrogenated 6H-SiC(0001) and 3C-SiC(111). On 6H-SiC(0001) two signals at 2133.5 and 2128.0 cm−1 are observed. Their intensity ratio varies with sample preparation temperature. On 3C-SiC(111) essentially a single mode is observed at 2128.4 cm−1 at all temperatures. The origin of the two modes is explained in terms of different stacking arrangement below the surface. The possibility for a stacking rearrangement during the hydrogen treatment is discussed.

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In situ ellipsometry is employed to study the kinetics of Pt silicide formation by thermal annealing with constant heating rates up to 30 K/min of a 10 nm platinum layer on silicon (100). From spectroscopic ellipsometry data of the initial Pt/Si, the intermediate Pt2Si, and the final PtSi phase an optimum photon energy of 3.5 eV was chosen for the kinetic study. Characteristic changes of the ellipsometric angles are observed as a function of temperature when the reaction fronts reach a depth below the surface that is related to the absorption length of the 3.5 eV photons. From an analysis of these transition temperatures based on the Kissinger formalism the activation energies for the formation of Pt2Si and PtSi are obtained as 1.55±0.05 and 1.72±0.05 eV, respectively, where the error bars follow from the precision of our measurements. A comparative study for a 100 nm Pt layer on Si yields the same activation energies albeit with a higher uncertainty, indicating that this method is particularly suited for ultrathin silicides.