A uniform epitaxial CoSi2 layer was grown on (100) Si substrate by rapid thermal annealing at 800°C in N2 ambient without capping layers from an amorphous cobalt-carbon film. The amorphous cobalt-carbon film was deposited on Si substrate by the pyrolysis of cyclopentadienyl dicarbonyl cobalt. Co(η5-C5H5)(CO)2. at 350°C. The leakage current measured on the junction, fabricated with the epitaxial CoSi2 layer and annealed at 1000°C for 30 s. was as low as that of the as-fabricated junction without silicide. indicating that epitaxial (100) CoSi2 is thermally stable at temperatures even above 1000°C and has a potential applicability to the salicide process in sub-half micron devices.

The effect of the thickness of the SiGe layers in the Co-SiGe/Si reaction is investigated. Formation of the disilicide phase is retarded when compared to the reaction of Co with pure Si substrates. This delay is dependent on the thickness of the SiGe layer, which determines the effective Ge concentration at the reaction front, changing the energetics of the reaction. Besides, Ge expelled from the Co(Si1-yGey) compound blocks the Co diffusion paths, slowing down the reaction. The thermal stability of the silicide layer is also affected by the Ge segregation, with the film agglomerating at lower temperatures when formed on thicker SiGe layers. The slow supply of Co atoms to the reaction front, due to the blocking of Co diffusion paths by the segregated Ge, is believed to be the reason for the presence of the preferential (h00) orientation of the disilicide phase observed in our samples.

Ultra-thin epitaxial CoSi2 films formed by Co(3∼5nm)/Ti(1 nm)/Si(100) and Co(3∼5nm)/Si(lnm)/Ti(Inm)/Si are studied. The multilayers are deposited by ion-beam sputtering. Rapid thermal annealing (RTA) is used for silicidation. XRD, RBS, TEM, AFM, four-point probe, I-V and C-V measurements are carried out for characterization. The XRD spectra show the CoSi2 film formed by Co/Ti/Si or Co/Si/Ti/Si solid phase epitaxy has, epitaxial characteristic. XTEM shows that the film is continuous. RBS/Channeling shows that the formed CoSi2 has sharp interface with a minimum channeling yield of Co signal of 40%. AFM shows that the surface of ultra-thin CoSi2 film is smooth with a roughness of nearly 0.7 nm. The Rs∼T relationship shows that the CoSi2 films formed by Co/Si/Ti/Si reaction have the best thermal stability (stable up to 900°C). Those formed by Co/Ti/Si reaction are stable up to 850°C, while those formed by Co/Si reaction are only stable up to 750°C. By fitting the experimental I-V and C-V curves of the epitaxial CoSi2/Si Schottky diodes, barrier heights of around 0.6 eV and close to unity ideality factors are obtained.

The effect of a small amount of Pt (5 at.%) on the thermal stability of NiSi film on (100)Si and (111 )Si has been investigated. Rutherford back scattering, Scanning Electron Microscopy, and X-ray diffraction have been used to study the formation, microstructure and orientation of the silicide. The addition of platinum results in increasing the disilicide nucleation temperature to 900°C and thus leads to a better stability of NiSi at high IC processing temperatures. The presence of Pt also induced a texture of the NiSi film both on (11 1)Si and (100)Si. The increase in thermal stability is explained in terms of nucleation controlled reaction concept and should open new possibilities for the use of NiSi in self aligned silicidation. The redistribution of Pt in the silicide is examined and explained in terms of kinetics and thermodynamics considerations. The addition of Pt also increases the temperature of agglomeration of NiSi.

Low values of contact resistance Rc(Ω) and specific contact resistance, ρc(Ωcm2) are essential for ohmic contacts to devices with ULSI dimensions. The incorporation of silicides into contact structures has made a substantial contribution towards this goal. However the modelling and characterisation of these more complex silicide contact structures still requires considerable development. The variation of doping density in the vertical direction will cause a strong local variation in silicon resistivity with depth as well as a pronounced variation in the silicon-silicide barrier layer as a function of depth.

In this paper we use a three dimensional (3-D) finite element analysis of sub-micron silicide contacts to illustrate the influence on Rc of the silicon doping profile in the sourcedrain contact regions. In addition, the influence of the doping profile on the current density distribution at the silicon-silicide interface is presented. A comparison of results is made between a uniform doping profile and two ion-implanted profiles. In order to improve the model's accuracy, the often neglected contribution of the metal-silicide barrier (ρca) to Rc is taken into account. Experimental measurements using a Cross Kelvin Resistor (CKR) test structure, have been used to determine ρca (∼3–5 × 10−9Ω.cm2 ) of the aluminium-TiSi2 interface.

For embedded DRAM (E-DRAM) devices with feature sizes of 0.25 µm and beyond, contact processes with low contact resistance and low junction leakage current are required. The contact etch process needs to etch through multi-layer structures with SiO2, SiON/SiN layers and stop on Ti-polycide gate and Ti-salicide active regions at the same time. The key issues include high selectivity to TiSix, vertical profile, complete removal of SiON/SiN cap layer and no polymer residues. In this paper, multi-layer contact etching without attacking TiSix is reported. Using new process chemistry, the new contact etch process has been demonstrated for the manufacturing of 0.25 µm E-DRAM and beyond.

Favourable gas-phase conditions for deposition of Ti(C,N) from tetrakis(dimethylamine)titanium (TDMAT) in a pulsed DC-plasma have been determined, making use of mass spectroscopy. Decomposition of TDMAT in a pure hydrogen plasma results in the favourable cleavage of dimethylamine from TDMAT but prevents the formation of Ti(C,N) due to the lack of nitrogen and carbon. Addition of N2 to the hydrogen plasma results in the formation of NHx (l<x<4), opening possible transamination pathways. Transamination plays an important role in thermal CVD processes and results in high quality TiN layers. However, an undesired side-effect is the gas-phase particle formation under the conditions used here, possibly due to TDMAT - N2 interactions. The depletion of TDMAT by interaction with nitrogen in a H2(85%) - N2(15%) plasma proceeds in a mechnistic step with a rate constant of k = 4.7 × 10−14 cm3 mol−1sec. Results were compared with those obtained from using ammonia under similar process conditions, and with results from thermal CVD. Seemingly high quality Ti(C,N) coatings were deposited at temperatures between 200°C and 425°C on steel and glass with this simple and, therefore, interesting set-up.

The formation mechanism of deformed tungsten oxides (WOx, x=2,3) on WSix/poly Si gate stacks has been investigated. It was revealed that plasma etching process introduced oxygen impurity into WSix surface and caused the WOx formation during the subsequent thermal oxidation. WSix films preferred corientation were found to be stable in the oxidation process after plasma etching process.

A Cu-based metallization scheme has been studied for establishing low resistance contacts for a Si/SiGe/Si heterojunction bipolar transistor (HBT) structure. As-grown doped layers were further implanted with BF2 and As ions for the p-type base and n-type emitter layers, respectively, in order to produce a low sheet resistance surface layer. Contacts were metallized using an e-beam deposited multilayer structure of Ti/Cu/Ti/Al. Specific contact resistances of the order of 10−7 Ω cm2 or lower were obtained.

Ballistic electron emission microscopy (BEEM) and deep level transient spectroscopy (DLTS) have been used to study the effects of substrate damage introduced by an ion-milling process in PtSi/n-Si Schottky contacts. Argon ions with well-defined energies of 300, 500, 700, 1000, 1500 eV were used to sputter n-type Si substrates in an ion beam sputtering system before metal deposition and silicide formation. Histograms of the PtSi/n-Si Schottky barrier height (SBH) measured by BEEM show that the mean SBH decreases with increasing ion energy, which can be explained as a result of donor-like defects that are introduced by the ion milling treatment. From DLTS measurements, we found direct evidence for the presence of such defects.

Titanium-silicon-nitride films were grown by atomic layer deposition using an alternating supply of tetrakis(dimethylamido)titanium (TDMAT), silane. and ammonia, at substrate temperature of 180°C. The supply of a reactant was followed by a purge with inert gas before introducing another reactant onto the substrate in order to prevent gas-phase reactions. In one set of experiments the reactants were supplied separately in the sequence of TDMAT. silane. and ammonia. The Si content of the films remained constant at 18 at.%. and the film growth rate varied little from 0.24 nm per reactant-supply-cycle, even though silane partial pressure varied from 0.002 to 0.1 torr. In the other set of experiments silane and ammonia were simultaneously supplied in the sequence of TDMAT and silane/ammonia. The Si content varied from 3 to 23 at.% as the silane-to-ammonia ratio varied from 0.01 to 10. Atomic layer deposition of Ti-Si-N films allows the precise control of Si content as well as film thickness.

Platinum has been successfully patterned with a TiN mask in an Ar/O2 plasma.No fence residue was observed on the etched Pt pattern if the thickness of the TiN mask was less than 300 nm. During the etching process, titanium dioxide and platinum oxides were formed and redeposited on the mask and the Pt structure in the Ar/O2 plasma according to Auger and XPS analyses. The etch rates of Pt and TiN films decreased with increasing oxygen concentration in the Ar/O2 gas mixture. The addition of O2 inthe gas mixture could improve the sidewall slope of the etched Pt structure. This was ascribed to redeposited platinum oxides and TiO2 on the sidewall, which makes the sidewall more resistant to ion etching at a higher concentration of oxygen.

The oxidation of Si catalyzed by 170-nm-thick Cu3Si at elevated temperatures has been investigated by transmission electron microscopy and Auger electron spectroscopy. For wet oxidation at 140–180 °C, the growth rate of the oxide layer was increased with the temperature. On the other hand, as the temperature was increased above 200 °C, the growth rate slowed down. The growth kinetics of oxide was investigated. Controlling mechanisms for the growth of oxide owing to the grain growth of Cu3Si are discussed. The activation energy for the linear growth of oxide was measured to be 0. 19 ± 0.1 eV.

Phase formation and change in morphology of Ti, V and Nb oxide films on (100)Si and (111)Si, with native oxide layer, have been studied by XPS in situ. The metal oxides were formed by the interaction at room temperature in UHV multistep deposited of Ti, V or Nb with native oxide. The formation of clean silicon regions during the growth of three-dimensional metal oxide islands is discussed. Differences observed in composition of Nb oxides on (100) Si and (111) Si are considered.

In this study, we investigate the diffusion of mobile ions through thin PSG or SiN layers using secondary ion mass spectrometry (SIMS). The diffusivity of Na through either layer is about 100,000X slower than through SiO2. Hence, thin layers of these materials are effective barriers for short anneals at 400°C. However, there is significant diffusion of both Na and K through these layers at 550°C. This suggests that improved cleans will be required to remove mobile ion contamination after interconnect processes.

In this work the nucleation and growth of CVD Cu on MOCVD TiN barrier layer as well as on PVD Ta with and without a PVD Cu seed layer on top were studied. Scanning and transmission electron microscopy was used to characterize the dependence of morphology and microstructure on deposition time. XRD measurements were carried out to study the orientation of the polycrystalline films. Atomic force microscopy was applied to investigate the surface topography. A random crystal orientation and an amorphous interlayer between the CVD Cu film and the barrier - leading to a poor adhesion performance of the CVD Cu films - were obtained on Ta and TiN, where island growth can be observed. A CVD Cu film deposited on top of PVD Cu leads to a highly preferred <111> orientation and a significantly improved adhesion of the Cu film. A PVD Cu seed layer as thin as 60 Å was found to produce an epitaxially grown <111> textured Cu film. These results highlight the importance of the initial growth stages for both morphology and adhesion of the CVD Cu films.

The advent of inlaid Cu interconnects has presented new challenges for the industry to fill high aspect ratio dual inlaid features. CVD Cu offers advantages for excellent step coverage and is a technique extendible for future generations of devices. We have developed a robust CVD Cu process and a CVD/PVD reflow integration scheme. In this paper, we present results of an extensive study on CVD Cu process development and integration. The effects of various precursors, carrier gases (H2, He and N2) and barrier layers including CVD TiN, PVD Ta, PVD TaN, PVD Ta-Si-N, and a hybrid barrier, on the CVD Cu film properties and device electrical properties are discussed. The extendibility and challenges of current CVD Cu processing will also be discussed.

We have measured the growth rate and film properties for the chemical vapor deposition of copper thin films using H2 reduction of Cu(fod)2 [H(fod) = 6,6,7,7,8,8,8-heptafluoro-2,2- dimethyl-3,5-octanedione]. The results are directly compared to deposition using Cu(hfac)2 [H(hfac) = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione]. Higher growth rates are obtained using Cu(fod)2, in part because of differences in reaction order between the two compounds. However, both compounds exhibit significant cluster formation during film nucleation, which leads to residual porosity and film resistivities above 2 µΩ-cm.

The agglomeration of thin (10 nm) Cu films suitable for use as electroplating seed layers has been investigated on ultrathin (<4 nm) Ta, Ta1-xNx, Tal-xOx, and composite Ta/Ta1-xNx, diffusion barriers. Copper films on clean 3.6nm Ta barriers deposited by ultrahigh vacuum sputter deposition at up to 120°C are stable against agglomeration during 30 minute anneals at 360°C and display strong (022) crystallographic texture. Similar Cu films deposited on thinner Ta, Ta0 85N0 15, Ta0.95O0 05, and residual gas contaminated (∼ 1 Langmuir) Ta barriers agglomerate during annealing, and Cu films on Ta0 85N0 15 and contaminated Ta have random biaxial crystallographic texture. The density of agglomerated regions in Cu films on SiO2 and Ta0 85N0 15 is characterized as a function of thickness of an ultrathin Ta adhesion layer.

Copper has been actively pursued as the most promising candidate for replacing the current Al metallization for ULSI interconnection because of its higher electrical conductivity and resistance to electromigration. In this work, we present our experimental results on electroless copper deposition on various seeding layers from a formaldehyde-based solution with EDTA as a complexing agent. For electroless plating, a seeding layer is essential for the initiation of copper deposition. X-ray diffraction analysis revealed a variation in the crystallographic orientation of the electroless deposited copper with different underlying seeding layers. The seeding layer is the key factor affecting copper nucleation and grain growth. The initial nucleation behaviors of electroless copper deposition on palladium and copper seeding layers were investigated. The microstructure of electroless deposited copper blanket films was studied using both SEM and AFM, and the crystallinity was analyzed using XRD. The crystal orientation and surface texture of the electroless deposited copper films could be modified by thermal annealing in vacuum (10E-6 Torr) for 30 min at temperatures ranging from 200°C to 300°C. The ratio of crystal orientation, I(111)/I(200) increased with higher annealing temperature, indicating enhanced growth of the (111) crystal structure.