Thin Ir films were deposited onto clean (111) Si surfaces. The films were analysed by Rutherford backscattering and transmission electron microscopy and were shown to be continuous for film thicknesses as small as 0.5nm. The films contained internal stress as deposited and coiled up when the substrate was removed chemically.

A four point probe was employed to measure the resistivity of the films as a function of film thickness. The resistivity increased with decreasing film thickness, from ∼35 micro-Ohm. cm for 160nm thick films to -190 micro-Ohm. cm for 0.5nm thick films. This increase in resistivity is shown to be consistent with theories of carrier transport in thin films.

Hillocks, surface protrusions from thin metal films, have been observed in Al, Al/Cu, Pb, and other materials. Platinum films are widely used as substrates for the deposition of ferroelectric thin films because of their superior oxidation resistance. However, hillock formation in platinum films has not been reported in the literature. In this work, we report the appearance of hillocks in platinum in Pt/Ti bilayers on oxidized silicon wafers. Platinum films 250 to 300 nra were deposited by ion beam sputter deposition at 25°C and 300°C onto a 70 nm Ti film on oxidized Si wafers. The wafers were then heated in flowing argon to 600°C, held 1 hr at 600°C, and cooled to room temperature while the wafer curvature (and hence the film stress) was measured with a laser beam deflection technique. At 600°C, compressive stresses of 0.1 to 0.4 GPa, due to thermal expansion mismatch, developed in the metal films. The platinum surface, initially flat, showed strong hillocking after the anneal. Cross-sectional TEM revealed that severe Ti/Pt interdiffusion occurred, in one case leading to a Ti layer on the top surface.

(100) Fe films deposited on (100) Pd, Ag, Au and Pt seed layers, with the latter metals deposited on (100) Si with proper respective seed layers, have been heated to 600°C, and their thermal stabilities assessed. The Fe layers were found to stay little changed, both structurally and magnetically, up to an anneal of 30 min around 400°C. At higher temperatures, the Fe layers change in structure and degrade magnetically, but with different mechanisms for different structures. For the ones with Pt or only with Pd, the consumption of the metal layers for the suicide formation below 400°C causes less changes of the Fe layers than those in the other structures. For the one with Ag, Fe apparently mixes with Ag above 400°C, with Ag being nearly intact up to 600°C, resulting in a rapidly decreasing magnetic moment of Fe. For the structure with Au, the formation of the Au-Si eutectic melt at 363°C completely destroys the structure and magnetic moment of Fe above 400°C.

A photoelectron microscope operating with a retarding field analyzer has been used to exploit core level energy shifts due to band bending in order to directly image Fermi level variations on n- and p-type cleaved GaAs(110) surfaces. Fermi level maps resolved to better than 10 um indicate lateral variations in the surface Fermi level which are often quite abrupt. In agreement with earlier, lower resolution work [1], Fermi level topography is found to be highly correlated with surface roughness as characterized by SEM, optical microscope and stylus profi lometer. The largest defect derived pinnings encountered to date resut in the Fermi level lying 0.5 eV above the VBM for both n- and p-type GaAs. Low coverage In evaporations have the. effect of reducing Fermi level contrast as Fermi levels in formerly unpinned regions move into the gap.

Controlling the size and distribution of silicon precipitates in aluminum alloy depositions is important for yield enhancement and reliability of small geometry metal interconnects. A non-contact and non-destructive thermal wave imaging technique is used to detect and evaluate size and density of silicon precipitates in AISi and AlSiCu alloys. The thermal wave results are corroborated with SEM and Auger data.

Atomic Force microscopy, scanning electron microscopy, and transmission electron microscopy was used to study Al/Si/Cu films sputter deposited at 2 and 45 mTorr. AFM and SEM analysis shows the films to consist of columnar structures commonly seen in PVD deposited thin films, while the TEM analysis showed the films be polycrystalline. Comparing the columnar structures seen in the AFM and SEM study to the grains found in the TEM study, we conclude that the columns consist of single grains. Thus for these films AFM or SEM analysis can be used to determine the grain size. Finally, an AFM scan of a Al/Si/Cu deposited via was performed. The AFM image clearly shows the high resolution of the AFM, while it also illustrates the problems caused by the finite size of the AFM tip.

A TiN(0)-encapsulated copper structure was made by annealing a Cu-10 at%Ti alloy film evaporated on a SiO2/Si(100) substrate in N2 or NH3 ambiente. During thermal cycling, the tensile stress in the nitridated films is in the range of 200 to 800 MPa. The stress relaxation depends on the cooling cycle and the presence of interlayer between film and substrate. A fast heating rate (70°C/min.) to 550°C in an NH3 ambient can effectively suppress the formation of Cu3Ti and enhance the TiNχ(0) formation near the surface of the copper film. This self-encapsulated Cu structure exhibits good adhesion to SiO2 and oxidation resistance. A fully encapsulated Cu fine line structure can be achieved by annealing a Cu-10at%Ti alloy film in an Ar ambient at 550°C and then in an NH3 ambient at 550°C to form TiOχ/Ti5Si3 adhesion layer and TiN(O) layer, respectively.

Band profiles specify the position of all band edges as a function of distance from a sample surface or interface. They largely determine the electrical and optoelectronic properties of semiconductor heterostructures. Neither theory nor standard transport measurements alone have been able to give reliable values for band offsets, much less entire band profiles. However, the use of electroreflectance, which reveals crossover transitions between localized states or band edges present on opposite sides of an interface, and which allows us to measure accurately built-in fields, has allowed us to determine accurate band profiles for several types of semiconductor heterostructures. The procedure used to find the band profile is elucidated in detail for two technologically important cases.

Sputtered aluminum has been used for interconnection in integrated circuits because of its low resistivity. However conventional sputtered aluminum has two important drawbacks, poor step coverage and poor planarization, which make it unsuitable for eubmicron multi-level interconnect process. CVD tungsten is an attractive option for forming plugs and interconnects but suffers several drawbacks. It is therefore preferable to use aluminum for both plugs and interconnections due to its simplicity and established prior history. We have developed a fully planarieed aluminum metallization process which produces void free contact plugs.

In order to verify the filling of the contact plugs, we have carried out extensive SEM analysis using secondary electron and backscattered electron imaging methods with various SEM sample preparation methods, i.e. chemical etching to extract the metal plug without inducing any damage to the metal, SEM cross section prepared with some oxide (about 1000Å) left in front of the metal plug and standard SEM cross section through the metal plug. Complementary secondary and backscattered imaging has proven to be a reliable method for ascessing the filling of the contact holes. Wafer and package level reliability data for the planarized aluminum metallization used on a megabit device will also be presented.

In this study, the application of Sllicidation Through OXide (SITOX) process to TiSi2 formation is extensively investigated. The data show that the decomposition of an interfacial SiO2 layer between Ti and the Si substrate depends not only on its thickness but also on the silicidation temperature and the type of dopants in the Si substrate. In general, high annealing temperatures and B-doped p+ Si substrates enhance the decomposition of interfacial SiO2. After the silicidation process, the O concentration at the TiSi2/Si interface is approximately two orders of magnitude higher with SITOX than with the conventional silicidation process. This high interfacial O concentration has no significant effect on the electrical properties of SITOX TiSi2 films and junction diodes. The X-ray Diffraction analysis shows that SITOX TiSi2 films have a polycrystalline structure as do conventional TiSi2 films. The average grain size in a 100 nm SITOX TiSi2 film is estimated to be about 10 μm wide, while that in a 120 nm conventional TiSi2 film is about 3 μm. Histograms of leakage current for junction diodes confirm that the SITOX process can improve the uniformity of leakage currents.

Selective chemical vapor deposition (CVD) of copper is the focus of recent research interest as a result of possible applications as vertical interconnect material in multilevel metallization. A variety of copper(I) and copper(II) compounds have been used to deposit copper. In some cases, the compounds selectively deposit copper on various different surfaces. However, the origin of this selectivity is not unambiguously established at this stage. In order to derive a better understanding of the CVD processes, a series of copper(I) compounds (β-diketonate)CuLn have been synthesized and used as CVD precursors. The new species (fod)CuL, where fod = 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedionate and L = PMe3, 1,5-COD, 2-butyne, BTMSA and VTMS (as defined below) are described. The CVD of copper and factors affecting selective copper deposition are discussed here.

An investigation of the electrical and microstructural characteristics of the Ti contact on silicon has been carried out. The presence of As in Ti/n+-Si samples was found to retard the formation of poly crystalline silicides compared with that in Ti/p+-Si samples with BF2+ implantation. The variations of Schottky barrier height, contact resistance and junction leakage current were correlated with microstrucxtural changes. The influences of the formation of amorphous interlayer between Ti and Si on the elctrical characteristics are discussed.

Palladium based metal systems can be used to make ohmic contacts to AIIIBV compound semiconductors. A covering layer of gold is advantageous even from the point of view of bonding. Gold, palladium, Au/Pd layers were studied on InP and GaAs substrates. The samples were annealed in the vacuum chamber of the scanning electron microscope (SEM) and the volatile component losses (arsenic or phosphorus) were monitored by a quadrupole mass spectrometer. The changes of the surface morphology were studied using the SEM images. In the case of Pd/AIIIBV samples a single characteristic peak due to the interaction taking place between the palladium and the substrate was observed on the volatile component loss vs. temperature curve. In the case of Au/Pd/AIIIBv samples a second peak appeared on the evaporation vs. temperature curve due to the interaction between gold and AIIIBV substrate. The temperature of that second peak is about 50–60°C higher than in the case of a single gold layer on AIIIBV substrates because gold had to diffuse through the palladium layer, what hindered the reaction of gold with AIIIBV materials.

The formation of thin copper films by H-atom reaction with Cu(FOD)2 and Cu(HFA)2 has been demonstrated at near room temperature. Oxygen atoms have now also been reacted with these β-diketonate copper complexes, producing films of copper oxide which can be readily reduced by subsequent treatment with H-atoms. The thin copper films produced are conductive and highly adherent. The oxygen atom reaction with the copper complex produces a visible chemiluminescent glow, yielding information on the nature of the reaction process.

A prototype RTP system has been developed which allows for in-situ emissivity and temperature measurements. The wafer emissivity is measured by using an optical detector at a wavelength of 2.4 μm and by modulation of the lamp power. This method permits accurate temperature determination in the range from 400 to 1200°C, independent of wafer backside roughness, backside layers, and transmit tance. The feasibility of the temperature measurement technique is demonstrated by using wafers with built-in thermocouples and highly As-doped wafers with different backside roughnesses or layers. The emissivity variations during processing can also be used to study thin film reactions in-situ. This is demonstrated for Co silicidation using probing wavelengths varying from 0.6 to 3.2 μm.

A process for creating patterns of metal-binding ligands on a variety of substrates is described. Deep UV patterning of chemisorbed ligand-bearing organosilane films creates modified surfaces that can selectively bind species such as Pd(II) via a covalent metal ion-ligand interaction. Patterned surface-bound Pd(II) is used to initiate additive electroless metallization at the catalytic sites. Metal adhesion to the substrate is controlled by the nature of the catalyst-ligand interaction.

The interactions of Ti with SiO2, Si3N4, and SiOiNy have been studied during rapid thermal annealing at 400 to 900 °C in Ar with 3% H2 ambient. X-ray diffraction, sheet resistance measurements, RBS, nuclear reaction technique to profile hydrogen, and microscopy have been employed in this study. The results of this investigation indicate that Si3N4 and SiOxNy are more stable with Ti than SiO2.

We have demonstrated a new method of doping suicide films which uses a pulsed excimer laser and a wafer cell which is filled with dopant gas species, e.g. BF3, ASF5, PF5. A spatially homogenized 308nm XeCl pulsed laser is used as a heating source to drive adsorbed dopant gas species into the suicide, as well as to outdiffuse dopants into the silicon substrate. The total dose, interface concentration, and junction depth, are controlled by varying the number of laser pulses. High interface concentrations (Cint >1020 atoms/cm3) and shallow junctions (Xj < 1500Å) are obtained using this technique. Laser irradiation also results in smoothing of the suicide film.

In order to simulate the precipitation effect during the aluminum metallization in the VLSI processing, an analytical model was constructed in this work. The nucleation behaviors of the silicon and copper precipitates within the aluminum - 1.0 weight percent silicon - 0.5 weight percent copper were studied. The volume free energies and interfacial energies were estimated, and the activation energy barriers for the precipitate formation were calculated. Silicon precipitate is more likely to nucleate than copper precipitate due to its lower interfacial energy and strain energy. The mechanical and electrical properties of the aluminum interconnects can be improved by the precipitate hardening.

A 15rm-thick Ti-layer incorporated between Pt and Si was found to be effective in improving the structures of PtSi/Si interface. The roles of Ti-layer were to react with native oxides on the Si substrate and to form Ti-O solid solutions instead of Ti oxides which act as diffusion barrier and inhibit the reactions between Pt and Si. Auger depth profiling gave evidence that Ti and O moved outward as platinum suicides were formed. A smooth PtSi/Si interface was revealed by the transmission electron microscope.