David Allen Roberts

Chemical additives for improved copper chemical vapour deposition processing

Abstract Techniques for improved copper chemical vapour deposition (CVD) processing by the addition of trimethylvinylsilane (tmvs) and hexafluoroacetylacetone (Hhfac) during copper deposition from the volatile liquid precursor Cu(hfac)(tmvs) are described. The tmvs enables stable high vaporization rates of precursor by direct liquid injection and the Hhfac permits higher deposition rates of smoother copper films. The resistivity of the copper films averages approximately 1.8 μΩcm as deposited. Combined together, these results mark an important advance toward a manufacturable copper CVD process.

New OMCVD precursors for selective copper metallization

A novel OMCVD process for the highly selective deposition of pure, adherent, low resistivity copper films onto conductive substrates is described. Central to this process is a new volatile liquid copper/sup +1/ precursor, Cupra Select, designed to thermally disproportionate at low temperatures to cleanly give copper metal and volatile non-corrosive by-products. Thus, selective depositions onto metallic versus insulating dielectric substrates are achieved between 120 to 420 degrees C with growth rates in excess of 100 nm/min and grain sizes as low as 0.1 microns. In addition, a novel complementary copper etching process is discussed that is chemically compatible with the copper CVD chemistry.<<ETX>>

Annealing ultra thin Ta2O5 films deposited on bare and nitrogen passivated Si(100)

Abstract Ta 2 O 5 films, deposited on bare and nitrogen passivated Si(100) surfaces, were annealed in the presence of three different oxidizing agents, NO, N 2 O, and O 2 , and then examined using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOFSIMS). These films were thin enough to allow spectroscopic examination of the interface between the silicon and the oxide. During deposition of Ta 2 O 5 on bare Si(100), the substrate is oxidized and the amount of oxide increases during subsequent annealing. No nitrogen accumulates when annealing in NO or N 2 O. Angle-resolved XPS and TOFSIMS depth profiles reveal, after annealing, oxidized silicon at the vacuum–solid interface and throughout the oxidized tantalum layer. For Ta 2 O 5 on nitrided Si(100), annealing at 820°C depletes nitrogen in the silicon nitride and increases silicon oxide, regardless of the oxidant used. Temperature programmed reaction spectra of Ta 2 O 5 deposited on previously oxidized Si(100) show SiO desorption above ∽950°C. The annealing results are accounted for in terms of chemical reactions at the buried interface that form SiO and, for the nitrided samples, NO species that migrate toward the vacuum interface. Oxidizing species from the gas phase also migrate to the buried interface to produce additional silicon oxide.

Characterization of thin copper films grown via chemical vapor deposition using liquid coinjection of trimethylvinylsilane and (hexafluoroacetylacetonate) Cu (trimethylvinylsilane)

We have developed a technique recently for copper chemical vapor deposition utilizing direct liquid coinjection of trimethylvinylsilane (TMVS) and the copper (I) precursor (hexafluoroacetylacetonate) Cu (TMVS). We present here an investigation of the properties of copper films deposited using this technique. The films were grown on Si3N4 substrates at temperatures in the range of 220–250 °C and characterized using several experimental techniques, with an emphasis placed on factors influencing copper film resistivity. The average as‐deposited film resistivity is 1.86 μΩ cm; this value is reduced to 1.82 μΩ cm when the effects of surface scattering are taken into account. The resistivity is essentially independent of film thickness for thicknesses between 0.2 and 3.5 μm, and is reduced by less than 0.05 μΩ cm by annealing at 400–600 °C in vacuum. The total impurity content of the films is approximately 100 parts per million. The film density is 97±2% of the bulk copper value. The average grain size increase...

Reversible Complexes for the Recovery of Dioxygen

Dioxygen 1s produced 1n tonnage quantities by the distillation of air at cryogenic temperatures. In recent years, alternative technologies have emerged that employ O2- or N2-select1ve sorbents or O2-permselectlve polymer membranes. New transition metal complexes that can bind O2 reversibly and with high specificity may provide the basis for even better processes for dioxygen recovery. One of the more promising approaches 1s the use of such complexes as O2 carriers In facilitated transport Immobilized liquid membranes. The performance of the cyclidene lacunar “protected site” dioxygen complexes developed by D. Busch et al. has been evaluated 1n such membranes operating at ca. 0°C. The complexes facilitate the transport of dioxygen and result 1n O2 permeabilities and O2/N2 select1v1t1es that have been related 1n a preliminary manner to the complex concentration, equilibrium O2 binding, reaction kinetics, and carrier and O2 dlffuslvltles. While the cyclidene complexes proved to be useful in these experimental studies, for practical membranes new carriers would have to be devised that are much more stable toward oxidative degradation. The synthesis and structure of a new “protectedsite” M reversible cobalt dioxygen complex are described.

First‐Principles Simulations of Conditions of Enhanced Adhesion Between Copper and TaN(111) Surfaces Using a Variety of Metallic Glue Materials

Particle aggregation and film agglomeration have been among the main technical hurdles for solid-state thin film development and have been observed in many semiconductor and catalytic systems. In heterogeneous catalysis, particle aggregation leads to reduction of effective surface area and degradation of catalytic performance. 8–10] On semiconductor surfaces, film agglomeration may give rise to electric short, electron migration, and device degradation. 11,12] Prevention of these effects presents a great technical challenge and has been one of the most active research areas in recent years. One approach towards reducing surface agglomeration is to insert a thin interfacial layer, often referred to as a “glue layer”, between the substrate and the adlayer of concern. Herein, we report three necessary fundamental conditions for a glue layer to be effective in promoting adhesion of a thin-film material to the substrate and to suppress agglomeration of the film at the interface. Copper agglomeration and adhesion enhancement on a TaN(111) surface, which was found to be the preferred orientation upon physical vapor deposition (PVD) growth, will serve as the model system to demonstrate the theoretical approach. Firstprinciples simulations were utilized to predict adhesion strength of various glue layer formulations. This approach allows us to make objective comparison of interaction energies between film interfaces and a set of performance criteria for material selection that augments empirically driven material selection processes, which have been largely trial-and-error in experiments to date. TaN has been used effectively as a barrier to prevent diffusion of the copper metal interconnect into the insulating dielectric and ultimately into the gate dielectric of CMOSbased transistors (CMOS = complementary metal oxide semiconductor). Atomic layer deposition (ALD) is a powerful thin-film deposition technique that provides atomistic control over deposition to support the continued scaling of the TaN barrier with a copper seed layer for advanced-generation CMOS devices. However, seed-layer copper agglomeration on the TaN surfaces has been a bottleneck in the development of this approach. Numerous attempts have been made to stabilize the copper thin film against agglomeration directly on the barrier with limited success. 21] Recently, Kim et al. proposed to insert a thin ruthenium layer between the copper film and the TaN substrate to enhance copper adhesion. The concept was also demonstrated for a Cu/WN interfacial system. Unfortunately, a Ru-based process is expensive, and thus its applications are limited. Herein, we show that first-principles simulations are capable of providing quantitative information to aid material selection to allow broad applications of glue-layer-based technology using ALD. The TaN(111) surface is described by a slab model containing four alternating layers of tantalum and nitrogen, with nitrogen on top (Figure 1). In between slabs, there is a

Cyclic alkylsilanes as low-pressure chemical vapor deposition silicon dioxide precursors

Abstract Silacyclobutane and silacyclopentane were synthesized for evaluations as precursors for silicon dioxide films under low-pressure chemical vapor deposition conditions at low temperatures. Both silacyclobutane and silacyclopentane were studied in the temperature range from 300 °C to 500 °C in the presence of oxygen. Deposition rates follow an Arrhenius behavior at constant reactor pressure, and the activation energies were found to be 41.8 kJ mole−1 for silacyclobutane and 75.3 kJ mole−1 for silacyclopentane below 66.6 Pa. Silacyclobutane is susceptible to homogeneous nucleation, so obtaining optimum oxide film properties with this precursor requires lower reactor pressures as the temperature is increased. The films were analyzed by Fourier transform infrared spectroscopy for the presence of hydroxyl and hydrocarbon bands. The refractive indices were measured by ellipsometry. Carbon concentrations and Si:O ratios were estimated by Auger electron spectroscopy. Quantum mechanical semi-empirical AM1 calculations were carried out to determine the relative ring-strain energies and reactivities. These results estimate the propensity of these molecules to ring open under mild thermal conditions. The experimental results are in agreement with the calculations.

MOCVD-TiN Barrier Layers for ULSI Applications

Material properties are reported of high quality TiN thin films, deposited by a low temperature (400 – 450 C) and low pressure (10 Torr) metalorganic chemical vapor deposition process using tetrakis(diethylamino)Ti and ammonia. Layer resistivities of less than 200 μΩ cm are achieved in 300 to 500 A thick films. The carbon and oxygen content in the films is found to be low ( Integration of the MOCVD-TiN films in a Ti/TiN/Al-alloy metallization scheme is also reported. The diffusion barrier performance of the MOCVD-TiN layers is found to exceed that of PVD-TiN layers.

The Deposition of Silicon Oxide Films by LPCVD at Temperatures as Low as 100°C from a New Liquid Source

A precursor for the LPCVD of silicon oxide films has been developed that extends the low temperature deposition range to 100°C. The chemical, 1,4 disilabutane (DSB), produces silicon oxide depositions similar to those of the higher temperature silane and diethylsilane (DES) processes. Optimum DSB processes require pressures below 300 mTorr, similar to silane, in contrast to DES pressures above 600 mTorr at 350°C. This results in poorer conformalities than those of DES, but the step coverages are still superior to those from silane oxides. The DSB films are low stress, carbon-free oxide layers that are suitable for temperature-sensitive underlayers and substrates such as photoresist, plastics, GaAs, and HgCdTe.

Thermal metalorganic chemical vapor deposition of Ti-Si-N films for diffusion barrier applications

Structurally disordered refractory ternary films such as titanium silicon nitride (Ti-Si-N) have potential as advanced diffusion barriers in future ULSI metallization schemes. Here the authors present results on purely thermal metalorganic chemical vapor deposition (CVD) of Ti-Si-N. At temperatures between 300 and 450 C, tetrakis(diethylamido)titanium (TDEAT), silane, and ammonia react to grow Ti-Si-N films with Si contents of 0--20 at.%. Typical impurity contents are 5--10 at.%H and 0.5 to 1.5 at.% C, with no O or other impurities detected in the bulk of the film. Although the film resistivity increases with increasing Si content, it remains below 1,000 {micro}{Omega}-cm for films with less than 5 at.% Si. These films are promising candidates for advanced diffusion barriers.