Films For Microelectronics Research Articles

Surface reaction mechanisms of trifluoroacetylacetone on clean and pre-oxidized Ni(110): An example where etching chemistry does not follow volatility trends

Ni contamination is an increasing problem in the fabrication of thin microelectronic films. In previous work, we examined nickel removal using oxygen and 1,1,1,5,5,5-hexafluoro2,4-pentanedione (Hhfac) or 2,4-pentanedione (Hacac) and oxygen. In both cases, Ni was etched cleanly by the precursors under net oxidizing conditions. Decomposition pathways were prevalent, however, under reducing conditions. In the results reported in this article, we used temperature-programmed desorption to examine the use of another β-diketone, 1,1,1-trifluoro-2,4-pentanedione, and oxygen in the same process. Ni was etched on the oxidized surface by the desorption of Ni(CF3COCHCOCH3)2 between 260 and 430 K. Etching ceased as decomposition products formed. The structures of decomposition products on both surfaces indicates the promotion of β-bond scission by Ni, predominantly at C-CF3, C-CH3 and C-CH/C-CH2. In the hexafluoropentanedione and pentanedione studies, β scission was also the decomposition pathway. However, with trifluoropentanedione, the pathways produced many more species than with either the unfluorinated or the fully fluorinated analog. This observation was unexpected. Another unexpected observation was that some maximum desorption rate temperatures do not follow expectations based on volatility: Instead, Ni(CF3COCHCOCH3)2 desorbed at nearly the same temperature as Ni(CH3COCHCOCH3)2 and much lower than Ni(CF3COCHCOCF3)2. Another trend that does not follow predictions based on volatility is the desorption of the intact precursor from the monolayer on the pre-oxidized surface: Molecular CH3COCH2COCH3 desorbed at a lower temperature than either the CF3COCH2COCF or CH3COCH2COCH3. At present, it is unclear why the results disagree with the volatility trends.

A new method for estimating residual stresses by instrumented sharp indentation

A general methodology is proposed for the determination of surface residual stresses and residual plastic strains using instrumented sharp indentation. The residual stresses and the residual plastic strains are assumed to be equibiaxial and uniform over a depth (beneath the indented surface) which is at least several times larger than the indentation contact diameter. The indenter load and geometry can be so chosen as to minimize or maximize the contact radius to seek the broadest range of applicability and validity of the proposed method by recourse to macro-, micro- and nanoindentation of elastoplastic materials. Invoking the invariance of contact pressure in the presence of an elastic residual stress, or the change in the instantaneous yield strength of a strain-hardening elastoplastic solid in the presence of a residual plastic strain, a step-by-step method is outlined here to estimate pre-existing residual stress/strain fields. The technique can be directly used for residual stress measurements in such applications as thin films for microelectronics and optoelectronics, structural coatings, and engineered surfaces whose properties are altered by such methods as mechanical working, etching, ion implantation, case hardening, laser treatments, shot peening or laser shock peening. The predictions of the proposed analytical method for determining residual stresses have been shown to compare favorably with finite element predictions as well as available experimental results.

Temperature-programmed desorption study of the etching of Ni(110) with 2,4-pentanedione

Ni contamination is an increasing problem in the fabrication of thin microelectronic films on Si. In previous work, we discussed nickel removal from nickel surfaces using oxygen and 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (Hhfac). In that study, Ni was etched cleanly by the precursors under net oxidizing conditions between 280 and 480 K with a maximum around 390 K. Decomposition pathways were prevalent, however, under reducing conditions. In this article we use temperature-programmed desorption to examine the use of a nonhalogenated β-diketone, 2,4-pentanedione (Hacac) and oxygen in the same process. Nonhalogenation of ligands decreases the acidity of the precursor and it is our intent to see how this affects reaction pathways, notably etching and decomposition. Ni was etched cleanly on the oxidized surface by the desorption of Ni-bis(acac) between 290 and 390 K with a maximum at 330 K. Interestingly, Ni-bis(acac) and 2,4-pentanedione desorb at lower temperatures than Ni-bis(hfac) and hexafluoropentanedione, a reversal of expectations based on volatility. Etching ceased as decomposition products formed. This was most notable above 450 K as several species including propanone, acetaldehyde, propanol and H3CCOCH2CHO (at high temperature) desorbed. The structures of decomposition products on both surfaces indicate that nickel promotes β-bond scission of the C-CH3 and C-CH/C-CH2 bonds in 2,4-pentanedione.

Porous silicon for microelectronics and optoelectronics

Porous silicon is a material which is obtained by anodic dissolution of monocrystalline silicon in concentrated hydrofluoric acid solutions. Its structure consists of a network of interconnected pores of very small radii (in the range 1.5–20 nm) corresponding to porosities which can be varied up to 90% according to the formation parameters: silicon doping level, electrolyte composition and anodic current density. The formation mechanisms of porous silicon are briefly presented, and the main properties of the material are reviewed. It is shown that they are at the origin of different applications in the field of thin films for microelectronics and for microsensor technology. The interest in porous silicon has been renewed recently by the discovery of a bright emission of visible light at room temperature from high porosity porous silicon films. The main characteristics of this new property, which opens up possibilities for silicon based optoelectronics, are described and discussed in relation to the mechanisms proposed for the light emission. Recent results on the visible electroluminescence which is obtained either from electrolytic cells or from solid devices are also presented.

Porous silicon for microelectronics and optoelectronics

Porous silicon is a material which is obtained by anodic dissolution of monocrystalline silicon in concentrated hydrofluoric acid solutions. Its structure consists of a network of interconnected pores of very small radii (in the range 1.5–20 nm) corresponding to porosities which can be varied up to 90% according to the formation parameters: silicon doping level, electrolyte composition and anodic current density. The formation mechanisms of porous silicon are briefly presented, and the main properties of the material are reviewed. It is shown that they are at the origin of different applications in the field of thin films for microelectronics and for microsensor technology. The interest in porous silicon has been renewed recently by the discovery of a bright emission of visible light at room temperature from high porosity porous silicon films. The main characteristics of this new property, which opens up possibilities for silicon based optoelectronics, are described and discussed in relation to the mechanisms proposed for the light emission. Recent results on the visible electroluminescence which is obtained either from electrolytic cells or from solid devices are also presented.

Growth and characterization of HTSC thin films for microelectronics devices : A. Perrinet al. Microelectronics Journal, 27, 343 (1996)

Growth and characterization of HTSC thin films for microelectronics devices : A. Perrinet al. Microelectronics Journal, 27, 343 (1996)

Theoretical Model And Computer Simulation Results Of Enhanced Diffusion Of High-Temperature Implanted Aluminum In Silicon Carbide

AbstractWide applications of silicon carbide (SiC) films in microelectronics devices make especially important predictions of the doping profiles during and/or after thermal treatment. A macroscopic kinetic model of enhanced diffusion of aluminum in SiC films during ion bombardment at high temperatures has been considered. The set of equations describing the kinetic model takes into account generation Vc and Csi vacancies during bombardment, migration of mobile species (Al) toward the surface and reactions of Al atoms with Vc and Vsi vacancies, as well as Al evolution from the film. The calculations were carried out for the flux of Al ions with energy 40 keV and current density 20 μA/cm2 to a dose 2 1016 cm−2 at 1800° C. The calculations have shown that the Al content in SiC at these condition does not exceed 40%. The calculation profile of Al is in a good agreement with experimental data [1].

Broad-band microwave characterization of bilayered materials using a coaxial discontinuity with applications for thin conductive films for microelectronics and material in air-tight cell

A new measurement method of complex permittivity of bilayered materials has been developed using a coaxial discontinuity. The electromagnetic analysis is performed according to the "mode-matching" method. The reflection coefficient of the principal transverse electromagnetic (TEM) mode is calculated by matching the fields at the interfaces of the layered material and using the orthogonality properties of modes in cylindrical waveguides. The complex permittivity of several known liquid or solid materials in bilayered structure are measured using this method. The experimental results over a wide frequency band (1 kHz-18 GHz) are consistent with those in previous papers and with dc measurements.

Measurement of the Townsend first ionization coefficient in tetraethoxysilane

The present paper reports the ionization coefficient in tetraethoxysilane determined experimentally by the steady state Townsend method for E/N in the range 450-2000 Td. Low-temperature plasmas of tetraethoxysilane mixtures may be used to perform plasma-enhanced chemical vapour deposition of silicon dioxide thin films for microelectronics at low substrate temperatures. Since tetraethoxysilane is a low-vapour-pressure liquid at room temperature, heating coils are attached to the ionization chamber to maintain the temperature of the chamber higher than that of the tetraethoxysilane source so that the required vapour pressure is obtained yet no condensation of tetraethoxysilane occurs on the chamber walls. Measurements indicate that the ionization coefficient increases very rapidly at about E/N of 450 Td, at which the value is 7.7*10-18 cm2, then the increase tends to saturate and reaches a value of 4.9*10-16 cm2 at E/N of 2000 Td. Furthermore, it is found that the logarithm of the current has a linear dependence on electrode separation. This suggests that electron attachment is very small or practically absent in this vapour.

Deposition, annealing and characterisation of high‐dielectric‐constant metal oxide films

AbstractFlims of metal oxides, such as Ta2O5, Nb2O5, Al2O3, HfO2, ZrO2 and TiO2 have been fabricated by use of different precursor materials, deposition techniques and annealing techniques. Several analytical methods were applied to study the layers. New data of fundamental properties of these metal oxides are reported and related to practical features that are of importance in device design and manufacturing of advanced, highly integrated devices. This overview may facilitate the choice of an optimal combination of precursor material, deposition technique and corresponding annealing procedure for a specific application of these metal oxide films in microelectronics.

Silicide thin films and their applications in microelectronics

Abstract Silicides are compounds of silicon with other elements in the periodic table. In this paper, usefulness of silicides and their thin films in microelectronics is discussed with emphasis on electrically conducting transition-metal silicides. Following a brief description of the device structure, contact resistance and interconnection delay (silicides are used to reduce these critical performance parameters of devices and integrated circuits), desired materials characteristics, preparation of thin films of silicides, a brief review of reaction kinetics, epitaxial silicides, and stability of silicides are discussed. It is shown that the silicides have found application in microelectronics (even on GaAs) because of their large silicon content, high electrical conductivity, high temperature stability, and corrosion resistance. They can be prepared easily and reliably and show potential for continued application in spite of ever-decreasing device/circuit dimensions in silicon integrated circuits. They offer a possibility of fabricating three-dimensional device/circuit structures and significantly faster heterostructure devices.

Interfacial reactions and silicide formation in Si/Ni/Si and Si/Cr/Si sandwich layers

AbstractThe preparation of well‐characterized silicide thin films for microelectronics needs a control of interfacial reactions and diffusion processes during heat treatment of metal/semiconductor systems. Two sandwich structures of Si(33 nm)/Me(50 nm)/Si(33 nm), where Me = Ni or Cr, with a total thickness of each structure of 116 nm were sputter deposited onto smooth silicon‐(111) substrates. The reactions of both metals with amorphous silicon thin films were activated in a differential scanning calorimeter (DSC), at a heating rate of 40°C/min−1, between room temperature and different higher temperatures. Auguer electron spectroscopy depth profiles showed that the Si/Ni/Si sandwich structure reacted almost completely during heat treatment up to 320°C and formed reaction products with a composition close to Ni3Si2. Selected area diffraction patterns revealed that this is a mixture of Ni2Si and NiSi silicides. A much less pronounced reaction between Si and Cr was observed in the Si/Cr/Si sandwich structure, even with heating to 630°C, resulting in CrSi2 silicide and different Cr–Si solid solutions. The results of AES depth profiling studies of the thermally treated sandwich structures are discussed in terms of diffusion processes, movement of interfaces and formation of silicides. The additional information obtained with differential scanning calorimetry and transmission electron microscopy enables a detailed identification of reaction products formed in the early stage of the thermally treated Si/Me/Si structures.

Investigation of the Behaviour of Stress in Metallization Thin Films for Microelectronics during Thermal Cycling using High-Temperature X-Ray Diffraction

Investigation of the Behaviour of Stress in Metallization Thin Films for Microelectronics during Thermal Cycling using High-Temperature X-Ray Diffraction

Lithographic patterning of self-assembled films

This article discusses a new, general approach for fabricating surfaces with precise positional control of chemical functionalities utilizing direct patterning of self-assembled (SA) or- ganosilane monolayer films with lithographic exposure tools, including deep ultraviolet, x-ray, and e-beam sources. Lithographically patterned one- and two-component SA films have been used to selectively deposit or attach a wide variety of materials to surfaces, including catalysts, electroless metal films, proteins, cells, and organic moieties. Selectively metallized, patterned SA films have been employed to fabricate functioning Si metal–oxide–semiconductor field effect transistor test structures. The utility of patterned SA films for microelectronics, sensors, and other applications is discussed.

Epitaxial Growth of Ba1−xSrxTiO3 Thin Films on YBa2Cu3O7−x Electrode by PE-MOCVD

AbstractPlasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD) has been successfully employed for the deposition of (100) oriented barium strontium titanate (BST) thin films on a variety of substrate and electrode materials. The incorporation of O2 plasma, which was used as oxidation reactant, has helped to reduce the required temperature for deposition of high-quality STO and BST thin films. This low temperature processing may make it possible to integrate BST on Si and GaAs. BST films with low leakage current densities of about 10−7 A/cm2 at 2-volt (about 105 V/cm) operation were obtained from PE-MOCVD processing. Moreover, the BST results of capacitance-temperature (C-T) measurements show that most of the PE-MOCVD BST films have Curie temperatures of about 30–35°C and a peak dielectric constant of 600–800 at zero bias voltage, The sharp transition in the C-T data indicates that the BST films may have a high induced pyroelectric coefficient at room temperature, which is highly desirable for uncooled IR imaging arrays. The x-ray diffraction and Rutherford backscattering spectrometry results show that the BST film composition reproducibility was well controlled at around Ba0.75Sr0.25TiO3 with a 4% variation. Device quality BST thin films with the thickness of 1000–2000 Å were produced. These results indicate that PE-MOCVD has high potential to be further developed and promoted as a production deposition technique providing high permittivity dielectric thin films for microelectronics and IR sensor industries.

New applications of low temperature PECVD silicon nitride films for microelectronics device fabrication : M. D. Dange, J. Y. Lee and K. Sooriakumar. Microelectron. J.22(7–8), 19 (1991)

New applications of low temperature PECVD silicon nitride films for microelectronics device fabrication : M. D. Dange, J. Y. Lee and K. Sooriakumar. Microelectron. J.22(7–8), 19 (1991)

Deposition, Annealing, and Characterization of Tantalum Pentoxide Films

ABSTRACTFilms of tantalum pentoxide (Ta2O5) have been fabricated by use of different precursor materials, deposition techniques and annealing procedures. Several analytical methods were appliedto study the layers. Fundamental properties and new data are reportedand related to practical features that are of importance in device design and manufacturing of advanced, highly integrated devices. This overview may facilitate the choice of an optimal combination of precursor, deposition technique and corresponding annealing procedure for aspecific application of these films in microelectronics, since the electrical properties reveal the potential of Ta2O5 films for the use in 64Mbit and 256Mbit DRAM devices as high dielectric constant material.

Deposition, Characterization, and Application of Aluminum Nitride Thin Films for Microelectronics

AbstractIn this paper we report on a high rate (˜ 100 nm/min) aluminum nitride (AIN) deposition process, as well as several novel applications of AIN thin films for microelectronics and optoelectronics applications. Surface morphology and chemical composition, etchability, etch selectivity to oxide, and step coverage at various deposition temperatures have been investigated by atomic force microscope (AFM), scanning electron microscope (SEM) and Auger spectroscope (AES). In addition, for the first time, chemical mechanical polishing (CMP) of AIN films has been carried out and a polishing rate of 270 nm/min has been achieved. Results of several novel processes involving AIN as an etchstop layer in microelectronics and as an optical interconnection in opto-electronics will be presented.

Wide area windowless disk plasma lamp of uniform intensity for use in microelectronic film processing

A wide area windowless plasma disk excited by a soft vacuum electron beam provides a wide area uniform source of vacuum ultraviolet (VUV) photons as well as atomic radicals. Hydrogen and oxygen when excited by the soft vacuum electron beam, emit strong atomic resonance radiation at 121.6 and 130 nm, respectively; in fact up to 8% of the total applied discharge power is emitted as VUV photons. The spatial uniformity of the atomic VUV resonance radiation approaches 6% across a disk 19 cm in diameter. The density of atomic oxygen species generated in the plasma disk has also been experimentally determined using an established polymer film etch rate method as well as with a conventional silver thin film sensor. We employ the disk plasma in a windowless configuration to achieve lower temperature chemical vapor deposition (CVD) than conventional thermal CVD. The VUV photon flux as well as the radical and excited atomic gas species emitted from the lamp can assist dissociation of feedstock reactant gases as well as assist heterogeneous surface reactions and increase surface mobility of absorbed species allowing for lower temperature CVD. Thin films of an aluminum nitride and hydrogenated amorphous silicon have been deposited at temperature between 100–400 °C. The deposited films show improvement over other plasma and photo-assisted CVD processes in the film quality achieved, the area covered, the substrate temperature required, and the maximum deposition rates that are possible. In situ generation of arsine (AH3) and unsaturated arsenic hydrides AsHx (x≤2) have also been achieved by placing elemental arsenic in an environment rich in atomic hydrogen created from the disk–plasma source.

In situ preparation of superconducting YBaCuO thin films on bare silicon

Large scale applications of high T c superconducting thin films in microelectronics depend strongly on the successful preparation of high quality material using conventional substrates like Si or GaAs. By means of the pulsed laser deposition technique, thin YBaCuO films on bare single crystal silicon substrates are deposited. To overcome problems due to strong substrate-film interdiffussion and thus the formation of a highly disordered lattice, the deposition of crystalline material is mandatory. This is accomplished in our experiments using substrate temperatures as high as 700…820°C during deposition. Our films grow as single phase material with the c-axis perpendicular to the film plane. No post deposition treatment is required to obtain high critical temperatures. Our best films so far show metallic behaviour and zero resistance temperature T c o ∼- 80 K. A parameter study of in situ grown thin films shows that the optimum for the deposition temperature depends on the oxygen partial pressure. Our best films grow at T s = 780° C and p = 1 mbar as well as at T s = 720° C and p = 0.5 bar.