Abstract: Recently transition‐metal nitrides and carbides have received great interest as diffusion barrier materials in contact structures for silicon semiconductor devices. Excellent stability of the contact structure is achievable through heat treatments of up to 600 °C when Ni is used as the top metal layer. However, the same transition‐metal compounds show poor barrier properties with Al as the top layer if heat treated to 600 °C. We have therefore investigated the failure mechanism of transition‐metal nitride and carbide barrier materials in Al overlayer metallizations. This knowledge has enabled us to develop high‐temperature contact structures for silicon semiconductor devices by using an intermetallic compound of Al instead of plain Al for the top layer.

Abstract: Contact reaction and Schottky barrier heights on Si were studied using Ti‐W alloys of increasing W concentration (Ti, Ti8W2, Ti4W6, Ti2W8) in order to determine the effect of alloy composition on Schottky contact behavior. Glancing angle x‐ray diffraction, Rutherford backscattering spectroscopy, and scanning electron microscopy were used to analyze the contact reaction. Schottky barrier heights were determined from the I‐V behavior of circular diodes. Four‐point probe measurements were used to compute the film electrical resistivity. Our experiments show that the addition of small amounts of W has raised the formation temperature of Ti silicides and maintained a low barrier height (∼0.55 eV) Schottky contact on n‐type Si up to 550 °C. A bilayer shallow contact metallurgy Si/Ti8W2/Ti3 W7/Al which provides a low barrier metal contact to n‐type Si as well as an effective diffusion barrier between Al and Si is proposed as a result of this study.

Abstract: We have studied reactively sputtered ZrN, the most thermally stable of the refractory metal nitrides, for its diffusion barrier properties in aluminum metallization schemes with Rutherford backscattering spectroscopy and transmission electron microscopy (TEM). We find this compound to be very effective against aluminum diffusion up to 500 °C, independently of substrate temperature during sputtering. The useful temperature range can be extended by 50 °C with proper preannealing prior to aluminum deposition. The TEM study of the ZrN grain size as a function of annealing temperature revealed that the grain size does not change significantly upon annealing and that the grains are relatively small even at the highest annealing temperatures (about 300 A at 900 °C). In addition, for annealing temperatures of and below 500 °C large portions of ZrN films were found to be of either amorphous or extremely fine–grain material, thus inhibiting the diffusion along grain boundaries. The presence of Zr 3 Al 4 Si 5 ternary compound in samples annealed at 600 °C, as determined by X-ray analysis, may suggest that the ZrN barrier fails by decomposition of the film by aluminum.

Abstract: Implementation of GdSi2 as low‐barrier (0.4 eV) Schottky contacts in a Si device requires a diffusion barrier between the GdSi2 and Al interconnects to prevent Al penetration. In this work, the effectiveness of vanadium films as such a diffusion barrier has been studied by using a set of complimentary experimental techniques: nuclear backscattering, x‐ray diffraction, and current‐voltage measurement of Schottky barrier height on both n‐type and p‐type Si substrates. We found that the effectiveness depends strongly on how the thin‐film structure of Al/V/GdSi2/Si was made, and especially on the formation process of GdSi2. The GdSi2, which was formed upon deposition onto a high‐temperature substrate, is superior in stability by showing no Al penetration to other processing schemes investigated. These results are explained by structural and compositional changes occurring in the layered films of Al/V/Gd/Si as a function of heat treatment. In order to understand the complex interdiffusion and compound formatio...

Abstract: A diffusion barrier is created in a n-type heterojunction layer adjacent to the active region of a semiconductor laser by doping the n-type layer with a periodic table group VI element. The diffusion barrier in the n-type layer prevents the migration of acceptors into that layer. The group VI elements are, in particular, sulfur (S), selinium (Se), and tellurium (Te). The acceptor of concern is zinc (Zn).

Abstract: A study was made of the Schottky barrier formation on cleaved n‐ and p‐type GaAs through surface and contact measurements. The metal used was silver. Surface studies, performed using the Kelvin method, have revealed that pinning of the Fermi level is obtained at submonolayer coverage and that silver deposition induced modifications in the electronic affinity. An electrical study of the contacts showed that diffusion barrier eVD is in the 950‐meV range for the n type and in the 270‐meV range for the p type. The difference between the pinning levels of n and p types for submonolayer coverage was found to be equal to that for contacts. We deduced that the Schottky barrier is established as soon as the first silver atoms are deposited. Possible characteristics were calculated for surface states (assumed to be discrete).

Abstract: not available for EP0060253Abstract of corresponding document: WO8201102A power distribution network for an integrated circuit is fabricated together with the circuit on a silicon substrate (10). The silicon substrate (10) is fabricated to form diffusion regions (50) as part of the active devices in the integrated circuit. A dielectric separation layer (51) is fabricated over the surface of substrate (10). Above the region (50) there is fabricated a power distribution line (52) comprising a metallization of aluminum or aluminum-alloy material. A passivation layer (54) is formed over the dielectric layer (51) and the conductor (52) but is opened above the central region of the conductor (52). An adhesion and diffusion barrier layer (58) is fabricated over the conductor (52) and passivation layer (54). Above the layer (58) there is fabricated a thick layer of metallization (60) in the form of a conductor strip configured similar to the underlying conductor layer (52). The conductive layers (58, 60) are etched to have essentially the same width as the conductor line (52). The conductive layers (58 and 60) can optionally be made to have a greater width than the underlying layer as is illustrated by the conducting layers (76, 78).

Abstract: A minimal corrosion resistor structure and deposition technique for superconductive circuits, with mutually protective niobium oxide passivation ring, gold corrosion barrier film and titanium resistive layer. Niobium has an intrinsic oxide of Nb 2 O 5 , which must be removed from a contact area designated by an opening in photoresist; the development process leaves a photoresist overhang. The corrosion barrier film is deposited through the opening. The resistive metal layer is deposited over the corrosion barrier film through the same opening. The gold corrosion barrier film prevents the titanium resistive metal layer from making corrosive contact with the niobium. The titanium resistive metal layer encapsulates the gold corrosion barrier film to prevent diffusion between the gold and further layers to be deposited subsequently. It would normally be possible for the titanium to spill over the gold and make corrosive intimate contact with the niobium; a self-alignment technique prevents such contact. The gold corrosion barrier film is sharply focused to form an area corresponding to the opening in the photoresist. An unfocused plasma oxidation step, which follows the gold deposition, grows an extrinsic Nb 2 O 5 passivation ring about the gold. The titanium resistive metal is then deposited with a wider focus than that of the gold corrosion barrier film, through the same opening; the titanium resistive metal layer deposits over the edge of the gold, encapsulating the gold with a diffusion barrier.

Abstract: The effect of a titanium layer as a diffusion barrier in Ti/Pt/Au beam lead metallization on polysilicon was investigated. A critical temperature, defined as the beginning of Au-Si eutectic reaction, was investigated for specimens with electron-beam (EB) evaporated and radio frequency (RF) sputtered titanium films 23-- 3000 A thick deposited onto polysilicon films 0.2-2 µm thick. Polysilicon surface roughness was characterized by grain step height as a function of grain size and polysilicon film thickness. The titanium film thickness required to retain the same metallization integrity during heat treatment became greater with increase in the polysilicon film thickness. At the polysilicon surface, the grain size and the grain step height became greater with increase in the polysilicon film thickness. The mechanism of increased heat resistance with increased titanium film thickness was examined relative to grain step coverage effect.

Abstract: PURPOSE:To enhance transferring efficiency, by providing a diffusion barrier layer between an ink layer and a base of a heat-sensitive transfer sheet comprising an ink layer containing a thermally transferrable dye on a base. CONSTITUTION:The diffusion barrier layer through which the thermally transferrable dye can not diffuse is provided between the ink layer and the base of the heat-sensitive transfer sheet. A material used for the diffusion barrier layer is preferably, for example, a polymer layer which is not softened by heat (150 deg.C or higher), for example, a gelatin derivative such as phthalated gelatine. The thickness of the diffusion barrier layer may be arbitrarily set, provided that thermal diffusion of an ink is substantially prevented, and is preferably not smaller than 0.5mum. The barrier layer in the present invention may comprise a hardener or other additives. The ink layer comprising the thermally transferrable dye preferably comprises a binder, which may be a hydrophilic or hydrophobic synthetic or natural polymer.

Abstract: Ring formation has been observed in thin‐film diffusion couples consisting of a 400‐nm‐thick Pb0.71Bi0.29 (in weight fraction) or Pb layer above a 200‐nm‐thick Pb0.84In0.12Au0.04 layer with a very thin (∼6 nm) rf‐grown oxide diffusion barrier in between. When interdiffusion was initiated by a rupture in the oxide barrier, concentric rings were observed to form in Pb‐Bi or Pb layer centering at the rupture site as interdiffusion proceeded. Rings were found to be a string of voids resulting from Kirkendall interdiffusion. In addition, relatively high concentrations of indium and oxygen were found at rings. Although the mechanism for ring formation is not clear at present, factors which influence ring formation are discussed.

Abstract: In this integrated circuit, the same layer 5, serving as a diffusion barrier with respect to a layer of metallisation 4 for a Schottky contact 3, serves at fuse locations 6. According to the invention, the stop layer is a layer of tungsten titanium sprayed in the presence of nitrogen.

Abstract: A composite antifriction bearing comprises a base layer 1 of metal alloy containing at least copper and lead, a surface layer 3 of lead alloyed with an anti-corrosion addition (e.g. tin or indium) and a diffusion barrier 2 arranged between the surface layer and the base layer, wherein the diffusion barrier comprises copper in combination with boron. The diffusion barrier prevents depletion of the anti- corrosion agent from the surface layer. The diffusion barrier and the surface layer may be applied by electrodeposition.

Abstract: The effectiveness of a thin (360 A) layer of reactively sputtered TiN as a diffusion barrier between aluminum and two silicides (PtSi and CoSi2) was evaluated. The chemical composition, structural phases and electrical properties of silicide/Al and silicide/TiN/Al contacts to n-type silicon were studied by Rutherford backscattering spectroscopy, glancing angle X-ray diffraction and Schottky barrier height measurements respectively. The results show that TiN is an effective barrier in these two systems up to at least 450°C, the typical temperature at which aluminum contacts are sintered.

Abstract: PURPOSE:To achieve fabrication of multilayer electrodes for use in a semiconductor of enhanced stability by a method wherein nitrogen plasma processing work is added after formation of a polycrystalline metal thin film to form a diffusion barrier intermediate layer with less grain boundary diffusion. CONSTITUTION:In a typical section in case of application to a bilayer, for example, a electrode construction, after formation of a film in which Mo or Ti is deposited as a intermediate layer 2 for diffusion barrier use, nitrogen plasma processing is carried out exposing the surface to plasma consisting of a mixture of nitrogen and argon. With this process, a nitride 11 of an intermediate layer metal (Mo or Ti) is selectively formed on the intermediate layer surface and grain boundary. This has a high electronic conductivity and a fine property, so that even if it is formed into grain boudary, any electric trouble does not come up. Therefore, a thermal stability can be improved by suppressing the grain boundary diffusion lowly. After this surface processing work, a metallic thin film 1 is formed and a multilayer electrode can be completed.

Abstract: A composite mask (5A, 6A) is formed by sequentially depositing blanket layers (5) and (6) of molybdenum and of a material respectively selected from the group consisting of MgO and Al2O3 on the surface of a copper layer (3), and producing in these layers (5) and (6) a pattern of openings corresponding to the negative of the desired copper pattern (3). Using said mask (5A, 6A) the portions of copper layer (3) exposed in said openings are removed, preferably by dry etching. MgO or Al2O3 adhere well to Mo and Mo adheres well to copper. The Mo layer (5A) also serves as a diffusion barrier for the copper. … The method is applicable in forming copper interconnect metallurgy for components such as semiconductor or dielectric substrates.

Abstract: A systematic study of the effects of implanted oxygen on the formation of Ni, Pt and Pd silicides has been carried out using 4He+ backscattering spectrometry (BS), 16O(d,α)14N nuclear reaction analysis (NRA) and x-ray photoelectron spectroscopy (XPS) for the analysis. A detailed presentation of the NRA technique is given as this technique was central to this study and is not as generally known as are BS and XPS (Chapter II). The depth resolution of this technique is found to be ~ 150 to 200 A in Ni. The oxygen sensitivity is essentially limited by measurement time (~ 10 hrs) to ~ 1019 to 1020 0/cm2. The effect of oxygen on the formation of Ni2Si is shown to vary with the initial location of the oxygen (Chapter III). Ni is the dominant diffusing species in Ni2Si formation. Oxygen initially located in the Ni film is found to build up during annealing at the Ni-Ni2Si interface until a diffusion barrier to the Ni is formed. The XPS data shows this barrier to be SiO2. Oxygen picked up during annealing from the ambient also plays a role in the buildup of this barrier. Once Ni2Si growth is halted, the second phase NiSi begins to nucleate and grow. The result is the simultaneous presence of Ni, Ni2Si and NiSi in the implanted samples. The threshold dose ϕth necessary for barrier formation is ~ 1.2 x 1016 0/cm2. This is equivalent to ~ 26 A of stoichiometric fused quartz if present as a layer. For the oxygen initially present in the Si, the oxygen is incorporated into the Ni2Si layer without an interfacial accumulation taking place. The relative reduction in oxygen density parallels that of the Si density as Si forms Ni2Si. We model these observations in terms of the asymmetries that are present in this system with regard to the moving species in Ni2Si formation and with regard to the chemical reactivity of oxygen with Ni and Si. The effects of implanted oxygen on NiSi formation are studied for the case of the oxygen initially present in the Ni2Si film on a Si substrate. Upon annealing, NiSi grows with square root of time in both implanted and unimplanted samples. This disagrees with the linear rate previously reported. The growth is slightly slower for implanted samples. The slowing is uncorrelated with the amount of oxygen, suggesting that a structural change due to ion implantation is the cause. During NiSi formation, oxygen is incorporated into the NiSi film without interfacial accumulation, but the oxygen distribution is seen to move towards the surface. This motion is explained in terms of a simple model based on the chemical affinity of oxygen to Si and Ni and the fact that Ni is the moving species in NiSi growth. The shift in the oxygen peak position during NiSi formation enables the implanted oxygen to act as a diffusion marker. This confirms that Ni is the diffusing species in NiSi formation. The use of implanted oxygen as a diffusion marker in thin film studies is briefly explored. We have also studied the effect of impurity oxygen initially present in a Pt film on Pt2Si formation (Chapter IV). We found that the redistribution of the oxygen during annealing, subsequent barrier formation and threshold oxygen dose were all identical to that of the corresponding Ni case. This result is shown to be consistent with the asymmetries present in the chemistry of oxygen relative to Pt and Si and in the initial location of the oxygen relative to the moving species (Pt). The case of oxygen initially located in the Si was not investigated as this case most likely is also identical to the corresponding Ni case. For the impurity oxygen initially present in a Pd film on a Si substrate (Chapter V), we found that the oxygen is incorporated into the Pd2Si without a diffusion barrier being formed. The implanted oxygen has no effect on the growth of Pt2Si. We find oxygen to be mobile in the Pd at an annealing temperature of only 250°C. Upon annealing the oxygen diffuses to the Pd-Pt2Si interface, to react and form SiO2 there. Simultaneously Si diffuses through the Pd2Si layer and forms additional silicide at the Pd-Pd2Si interface thereby incorporating the SiO2 into the Pd2Si. Thus barrier formation does not occur. We also show that our results identify Si as the dominant diffusing species during Pd2Si formation rather than both Pd and Si as previously reported. Generalizing from the result of our study of the effects of impurity oxygen on the formation of the silicides of Ni, Pt and Pd we present a conceptual framework for impurity effects in metal silicide formation (Chapter VI). This model relies on the asymmetries present with regard to the initial location of the impurity relative to the moving species and with regard to the chemical affinities of the impurity relative to the reacting species. The results for impurity N in the Ni-Si system are briefly compared with predictions of the model and shown to agree. Further work suggested by this model is summarized next (Chapter VII). The cases covered are impurity N in the Ni-Si, Pt-Si and Pd-Si systems along with impurity C in the Ni-Si and Pt-Si systems. Also covered are the preliminary results of contact restivity measurements after barrier formation has occurred for the cases of impurity N and O in the Ni-Si system. The results of this additional work are shown to be consistent with the model.

Abstract: A wire filament or multifilament wire or cable having an expanded metal or foraminous metal concentrically or semiconcentrically layered along the length of the wire so that the spaces or holes in the metal open radially of the wire or filament. The expanded or foraminous metal can be used in said wires or filaments as a strengthening layer, a conducting layer, or a diffusion barrier layer.

Abstract: In conventional, bronze-process wire a tantalum barrier has been used to protect stabilizing copper from tin diffusion. Although the practice has been quite successful, considerable research efforts are still being devoted to search for other materials for the barrier; the one that receives the most attention is niobium. The use of niobium would simplify the fabrication process and result in appreciable cost savings in large-scale applications. (This approach was first attempted by AERE Harwell and Rutherford Laboratory, England.1) However, it has been well-recognized that the one major shortcoming of the process that may limit its application is that an unwanted large Nb3Sn shell could be formed that may give rise to additional losses and result in instability.

Abstract: Backscattering measurements were performed to assess the stability of amorphous Ni-Nb for contacts of high temperature electronics. The interdiffusion of amorphous Ni-Nb and three semiconductors—silicon, GaAs and GaP—was measured to study the stability for primary metallization applications. Diffusion of gold with amorphous Ni-Nb and the same three semiconductors was also investigated in order to address diffusion barrier applications of amorphous metals. The results indicate that the use of amorphous Ni-Nb as a contact or a diffusion barrier could extend the useful operation temperature range for GaP devices to above 550°C.

Abstract: The development of a low cost and reliable contact system for solar cells and the fabrication of several solar cell modules using ultrasonic bonding for the interconnection of cells and ethylene vinyl acetate as the potting material for module encapsulation are examined. The cells in the modules were made from dendritic web silicon. To reduce cost, the electroplated layer of silver was replaced with an electroplated layer of copper. The modules that were fabricated used the evaporated Ti, Pd, Ag and electroplated Cu (TiPdAg/Cu) system. Adherence of Ni to Si is improved if a nickel silicide can be formed by heat treatment. The effectiveness of Ni as a diffusion barrier to Cu and the ease with which nickel silicide is formed is discussed. The fabrication of three modules using dendritic web silicon and employing ultrasonic bonding for interconnecting calls and ethylene vinyl acetate as the potting material is examined.