The texture of copper electrodeposits changes from the orientation that places the lowest energy crystal facets parallel to the substrate under a condition of low ion concentration adjacent to the deposit, to the orientation that places the higher energy crystal facets parallel to the substrate as the ion concentration adjacent to the deposit increases. The copper electrodeposits have peculiar surface morphologies and microstructures depending on their textures, which in turn may affect their mechanical properties even when they are obtained in similar electrolysis conditions. The electrodeposits undergo recrystallization, when annealed. The recrystallization texture may be different from the original deposit texture. These phenomena have been discussed.

Electroless Cu metallization has been fabricated by blanket electroless Cu deposition into the trenches in SiO2 dilectric layer on sputtered Cu seed layer with Ta diffusion layer and Al protection layer. Chemical-mechanical polishing of copper has been used to planarize the structure. Selective electroless CoWP layer has been deposited to protect inlaid Cu metallization.

Cu deposition profiles in submicron contact holes are investigated employing the Cu self-sputtering which do not need any inert gas e.g. Ar during sputtering. Excellent bottom coverage in the high aspect ratio contact holes was obtained at a large target-substrate distance in the selfsputtering due to a long mean free path of Cu ions and atoms, although a coverage is poor in Ar sputtering at 6 mTorr. It is also shown that the self-sputtering has low resputtering effect and high self-diffusivity of Cu, while the resputtering predominates in the case of Ar sputtering when DC bias is applied on the substrate. As a consequence, the bottom coverages of the self-sputtered films are much improved than the Ar sputtered ones. The present work strongly suggests that the self-sputtering is promising to fill Cu in sub micron via and contact holes.

To enhance the corrosion resistance and reliability of the proposed copper interconnections in silicon integrated circuits, alloying with small amounts thermodynamically favorable elements has been pursued. In the present investigation dilute copper (boron) alloy thin films (in boron concentration range of 0-4 at % in copper) were deposited by DC magnetron co-sputtering using a high purity copper and Cu-4 at % B targets. Films were then annealed in Ar-3% H2, pure Ar, vacuum, and air ambients in the temperature range of 200–500°C. Sheet resistance, Rutherford backscattering, x-ray diffraction measurements were made to characterize the films. The residual resistivity of the as-deposited alloy films was found to be 5.3 μΩ-cm/at %. To obtain sufficiently low working resistivity, an alloy content below 0.5 at % is suggested for application as a potential “metallization material. The addition of boron, which is the common dopant in Si, to the copper films offers considerable oxidation protection. The resulting oxidation rates are considerably lower than that for pure copper films. All this will be presented and discussed.

Co-deposition of copper-palladium alloy films was demonstrated using low-pressure CVD from individual precursors - (hexafluoroacetylacetonato)copper(I)(vinyltrimethylsilane) [(hfac)Cu(I)vtms] and palladium(II)bis(hexafluoroacetylacetonate) [Pd(hfac)2], for Cu and Pd respectively. High-purity alloy films with controlled composition, microstructure and morphology were prepared and their oxidation behavior was examined at different temperatures and compared with that of pure copper CVD films with similar morphology. As-deposited copper-palladium alloy films showed improved resistance to oxidation up to 300°C in air. Enhanced oxidation resistance compared to Cu CVD films was observed at concentrations of palladium as low as 0.5 at. %.

The substrate bias was applied during the chemical vapor deposition (CVD) process of copper in an effort to change the adsorption behaviors of the reactant. Copper films were deposited on TiN and SiO2 from Cu(hfac)(tmvs) with the substrate bias and without one. The surface morphology, the thickness, the sheet resistance and the purity of the films were investigated. When the negative substrate bias of -30 V was applied to the substrate, the deposition rate of copper increased both on TiN and SiO2. No change was observed in the chemical composition of the copper film deposited with substrate bias in comparison with that of the copper film deposited with no bias. It was calculated that Cu(hfac) has the dipole moment whose direction is from copper to hfac. Under the d. c.electric field, dipole tends to align along the poling direction. Resulting from the overlapping population (OP) value analysis, the improvement of deposition rate under negative substrate bias was explained due to the adsorption of copper atom in Cu(hfac) species directly onto the substrate by the electric field applied between the substrate and the gas showerhead.

Highly (111) oriented Cu films with a thickness around 1800 Å were prepared on Si (100) at room temperature by partialy ionized beam deposition (PIBD) at pressure of 8 × 10-7 - 1 × 10-6 torr. Effects of acceleration voltage (Va) between 0 and 4 kV on such properties as crystallinity, surface roughness, resistivity, etc. of the films have been investigated. The Cu films deposited by PIBD had only (111) and (200) planes and the relative intensity ratio, 1(111)/I(200), of the films increased from 6.8 at Va=0 kV to 37 at Va=4 kV. There was no indication of impurities in the system from AES analyses. A large increase in grain size of the films occurred with Va up to Va– 1 kV, but little increase occurred with Va>lkV. Surface roughness of the films at the ionization potential of 400 V decreased with Va, and resisivity had the same trends as that of the surface roughness. In the Cu films made by PIBD, it appears that changes of resistivity are mainly due to a surface scattering rather than a grain boundary scattering. The via holes, which is of 0.5. μm diameter x 1.5 μm deep, in the Cu films made at Va=4 kV, were completely filled without voids. Adhesion of the Cu film on Si(100) deposited at Va=3 kV was 5 times greater than that of Cu film deposited at Va=0 kV, as determined by a scratch test.

Liquid and volatile (hfac)CuL compounds where hfac = 1,1,1,5,5,5-hexafluoro- 2,4-pentanedionate and L = 1-pentene (1), acetyltrimethylsilane (2), and vinyltri- methoxysilane (3) were newly developed for reproducible copper deposition. During CVD processes, no premature decomposition of the precursor was observed in the source reservoir that contained the mixture of (hfac)CuL and excess free ligand L. Pure Cu films were deposited in the deposition temperature range 180°C ˜ 220°C

The low pressure chemical vapor deposition of Cu was investigated on TiN substrates that had been locally seeded with thin Cu layers. These Cu layers were 5Å, 40Å and 130Å thick and had been produced by PIB (Partially Ionized Beam) deposition. The growth rate and the XRD peak intensity ratio (I(111)/I(200)) of CVD-Cu increased somewhat in the case of Cu seeded TiN/Si substrates compared with as-received TiN/Si substrate. At the deposition temperature of 200°C, Cu film deposited on the 40Å seeded substrate had the lowest electrical resistivity value, 2.42 μ Ω cm that is as high as 1.5 times the bulk copper value. In adhesion test, as the seeding thickness increased from 0Å to 130Å, the adhesion strength increased from 21 N to 27 N.

The strategy of adding alloying elements during the chemical vapor deposition (CVD) of copper to improve the reliability of copper films was investigated. Deposition of Cu-Pd alloy films was demonstrated using low-pressure CVD with (hexafluoroacetylacetonato)- copper(I)(vinyltrimethylsilane) [(hfac)Cu(I)vtms] and palladium(II)bis(hexafluoroacetyl- acetonate) [Pd(hfac)2] in the temperature range of 100-200 ° C in a cold-wall differential reactor. High growth rates of 100-500 nm/min and high-purity films as confirmed by Auger electron spectroscopy (AES) were obtained. As-deposited alloy films showed low resistivities (˜ 2.3 μΩcm) at palladium concentrations below 3 wt. %. A high degree of conformality was observed on sub-half-micron trenches with aspect ratios greater than 3.5:1. The co-deposition of copper and palladium resulted in significant inhibition of palladium growth as compared to the independent palladium deposition.

The development of a reliable/reproducible chemical-mechanical polishing (CMP) process to planarize and define copper using a dual damascene approach is essential for introducing copper as the interconnection metal. In this paper we present results of a new polishing slurry containing glycerol and Al2O3 abrasive. The slurry is a near-neutral medium and does not have the effect of acidic or basic slurries on copper. The effect of glycerol concentration and the abrasive size on the CMP behavior is investigated. The changes in the slurry temperature, pH, viscosity, dielectric constant and surface tension were examined as a function of the glycerol concentration. The results, indicating a strong dependence on both the glycerol concentration and the abrasive size, are explained on the basis of viscosity and dielectric constant of the solution and the van der waal forces and the electrostatic repulsion between the particles.

The recent advent of Chemical Mechanical Planarization (CMP) as a major process technology has had a significant impact on the semiconductor industry. Oxide CMP is a technology enabler for logic and DRAM devices with feature sizes less than (or equal to) 0.75 micrometer [1]. Similarly, tungsten CMP has become a technology enabler for 0.35 micron devices [2,3], and current trends indicate that it will continue to play a major role in future generations of IC technologies [4,5]. CMP can also provide a technological advantage in front-end process modules such as Shallow Trench Isolation [6].

Today different Al-fill techniques are used for the fill of submicron contacts and vias. The integration aspects of the most promising approaches, Al-reflow, cold/hot Al-planarization and high pressure Al-fill (Forcefill) are compared to the widely used W-plug technique. The filling properties are discussed with respect to future applications in ULSI devices. Special attention is given to the barrier stability in contacts and the influence on patterning. Various electrical data and reliability results are compared to metallizations with W-plugs. The implications of the Al-fill processes on chip design, especially on the size and shape of holes, the pattern density, the possibility of producing stacked contacts/vias and the metal to contact/via overlap are considered also. In an outlook for future developments, e.g. the introduction of low k dielectrics, the inverse metallization architecture with (dual) damascene interconnects and the emerging Cu metallizations, Alfill processes are facing new challenges which will be discussed.

Unique characteristics of gas cluster ion beam bombardment are discussed in terms of ULSI fabrication processes. Cluster ion beams consisting of a few hundreds to thousands of atoms have been generated from various kinds of gas materials. Multi-collisions during the impact of accelerated cluster ions upon the substrate surfaces produce fundamentally low energy bombarding effects in a range of a few eV to hundreds of eV per atom at very high density. These bombarding characteristics can be applied to shallow ion implantation, high yield sputtering and smoothing, surface cleaning and low temperature thin film formation.

Chemical vapor deposition (CVD) of Al from dimethylethylamnine alane on atomically clean GaAs(100)2×4 surfaces has been investigated using an ultra-high-vacuum CVD reactor. Film composition, microstructure and growth rate were examined for deposition temperatures in the 100-500°C range. The results indicate reduced impurity incorporation at the lower deposition tenmperatures, and growth rates that are relatively temperatureindependent in the low-pressure regime examined (10−4 to 10−5 Torr). At temperatures ≥400°C the microstructure of films deposited by CVD and evaporation is remarkably similar, but at the lower deposition temperatures (∼150°C) the specific chemistry of the CVD process affects the film texture and preferential orientation.

An aluminum thin film for ultra large scale integrated circuits(ULSI) metalization has been formed by PACVD using DMEAA(Dimethylethylamine alane) as a precursor. The selectivity was lost but the conformal step coverage was still maintained when the hydrogen plasma was added to conventional CVD process so that perfectly planarized metalization could be obtained.

Comparing to thermal CVD, the reflectivity as well as the resistivity could be much improved especially when the film was deposited on SiO2. The deposition rate and the resistivity of PACVD Al thin films deposited on various substrates such as Si, TiN and SiO2 were compared with those of thermal CVD Al thin films.

The chemical vapor deposition (CVD) of aluminum is now gaining accceptance as a viable metallization technology for the fabrication of sub-0.5 micron interconnects. The incorporation of 0.5% copper into these aluminum films to enhance their electromogration resistance has been achieved by a number of different approaches. These techniques include the sequential CVD of the individual metals and the consecutive growth of CVD Al / PVD Cu followed by an interdiffusing thermal anneal. The potentially more elegant and streamlined solution explored in this paper is the simultaneous deposition of Al and Cu by CVD. A key requirement of this approach is the selection of copper precursors which are stable, volatile and free from oxygen and fluorine. The absence of the latter two elements is essential due to the high probablity of their extraction from the copper precursor by aluminum to form involatile aluminum oxyfluoride species. In our investigation of simultaneous Al/Cu we have utilized two well known aluminum hydride based precursors (DMAH and DMEAA) with two different copper precursors and we herein report the successful deposition of Al-Cu alloys using this approach. A discussion is presented of the dependence of the resulting Al-Cu film quality upon the choice of Al and Cu precursors used in addition to the CVD process parameters utilized for film growth.

Ultrathin refractory metal silicide films, such as tungsten silicide (WSix) offer a wide range of applications in VLSI and ULSI circuits such as local interconnects, bit lines and wordlines. One practical way of depositing WSix is by a CVD technique in which WF6 is reduced by either SiH4 or SiH2Cl2. For sub 0.5 micron technologies, SiH4 based WSix shows limitations due to poor step coverage and high F incorporation (>1020 atoms/cm3 ). If the reducing agent is changed to SiH2Cl2, then these problems are largely eliminated. However, interactions between processing parameters and film properties to achieve compositionally and structurally uniform films are not well understood. In this investigation, SiH2Cl2 based WSix films (60-200 nm) deposited on undoped poly-Si, doped poly-Si and oxide substrates were studied after a high temperature furnace anneal and oxidation cycle. Electron transparent samples were prepared by a low temperature ion beam technique and the individual films of Si-SiO2-poly Si-WxSiy layers were investigated by high resolution cross sectional transmission electron microscopy, x-ray diffraction and electron nanospectroscopy techniques with a beam energy of 300 kV. RBS measurements were used to determine the composition profile through the depth of the film and Si/W uniformity in terms of Si-rich and W-rich interfaces. SIMS measurements were used to determine the impurity content in the silicide film and at the film/substrate interface. This paper focuses on the processing-structure relationships in terms of development of defect structures within WxSiy, the non-stoichiometric W-Si compositons and related crystal structures and the role of the nucleation step in modulating the Si/W ratio at the WSix, /poly-Si interface and discusses their implications on future process development.

We have developed a new method of cleaning p+-Si surfaces by plasma hydrogenation and subsequent HF treatment prior to selective W-CVD by SiH4 reduction. The hydrogenation enhances the hydrogen-termination of p+-Si surfaces in HF solution significantly, resulting in high controllability in selective W-CVD on p+-Si surfaces. Contact resistivity was 0.5 to 3×10-7 Ω cm2 for single- and poly-crystalline p+-Si. The increase in junction leakage current was fairly small because of low Si consumption.

The characteristics of blanket CVD-W and PVD-W films with and without TiN/Ti underlayers have been investigated in terms of both materials properties such as resistance, stress, morphology, crystallinity, and composition, and prospective applications such as for DRAM bit line interconnections. The presence of a TiN underlayer has been found to induce preferential growth of dominant W (110) crystal orientation for both CVD-W and PVD-W whereas absence of TiN results in a W film of mixed W (110), (200), and (211) crystallites. Sheet resistance measurements of both blank films and conductor lines have shown that a 200nm-thick PVD-W film yields a lower resistance than a similar film with TiN underlayer and hence larger total thickness. This correspondence of W (110) intensity with resistance implies that reduction of the (110) oriented crystallites within a W film can yield lower resistances. Thus, by elimination of the TiN/Ti underlayer, monolayer PVD-W or CVD-W with a PVD-W underlayer can be effectively adapted to quarter-micron conductors for bit line interconnections and related structures in DRAM memory and other ULSI devices.