Properties of Anodic Films Formed on Reactively Sputtered Tantalum

Gerstenberg, D.

doi:10.1149/1.2424022

Cited by 46 publications

(12 citation statements)

References 7 publications

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“…However, Pavlovic (21) reported the dielectric constant of ~-Ta20~ ceramic to be 24.1 at room temperature and 100 kHz. Gerstenberg found an average value of dielectric constant for anodic films of 21.7 (22). There is clearly a strong tempera-) unless CC License in place (see abstract).…”

Section: Electrical Propertiesmentioning

confidence: 99%

Selected Properties of Pyrolytic Ta[sub 2]O[sub 5] Films

Knausenberger¹,

Tauber²

1973

J. Electrochem. Soc.

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Pyrolytic Ta205 films, in thicknesses up to 30,000.~, were produced by the TaCls-CO2-H2 reaction at 900~ These films were characterized by use of transmission electron microscopy, electron microprobe analysis, measurement of dielectric, and optical properties. It was found that the films were orthorhombic Ta205 (~-Ta205) with a fine grained structure. The films did not etch appreciably in hydrofluoric acid. Ellipsometric measurements indicated that the films had an index of refraction of 2.20 • 0.03 at 5461A. In addition, certain areas of the films exhibited slight optical absorption. The optical energy gap was found to be 4.20 eV. The dielectric constant and the loss tangent of the pyrolytic Ta205 films were measured over the temperature range 78~176 and the frequency interval 1-100 kHz and exhibited a surprisingly strong temperature dependence. These results and the electron microprobe results indicate the films are not stoichiometric.Tantalum pentoxide (Ta2Os) has played a very active role in electronic applications for over a decade. Ta205 has been used in thin film form long before the much studied thin film materials such as SIO2, SisN4, and A1203 came into positions of importance for applications such as integrated circuit (IC) passivation and insulated gate, field effect transistor gate dielectrics. It has been found for the latter materials that hightemperature (600~176 chemical vapor deposition (CVD) produced films with properties generally considered more desirable than those of films producd by other methods. In electronic applications Ta20~ is usually produced anodically, or sometimes thermally, but pyrolytic Ta205 has not been used, nor its properties investigated. This paper reports selected details on the preparation and properties of Ta205 films produced by CVD. Film DepositionThe general subject of oxide film preparation by CVD has been well-treated by Powell et al. (1). Pyrolytic Ta205 has been produced by Peacock (2) through the reaction of Tat15 vapor, H2 gas, and CO2 gas at 900~ and by Wang et al. (3), through the reaction of tantalum alcoholate vapor, helium, and oxygen at 450~The properties of the films produced by the former reaction were not investigated, and those of the latter reaction were described as amorphous and annealable to polycrystalline ~-Ta205 fter 30 rain at 800~The reaction between TaCl5 vapor, H2, and C02 at 900~ was used to prepare the films for this study. The presumed over-all reaction is 900~ 2TaCI5 + 5H2 + 5CO2 -+ Ta205 + 6CO + 10HCIThe deposition apparatus, shown schematically in Fig. 1, is a modified version of the one reported by Tauber, Dumbri, and Caffrey (4) for the pyrolytic deposition of zirconium dioxide. The substrate rests on a molydenum susceptor, which is heated inductively at 480 kHz, The susceptor is rotated by a specially designed harmonic drive. The gases are carefully metered through Brooks rotometers and are carried through stainless steel lines to the deposition chamber. The TaC15 vapor is transferred to the chamber by passing hydrogen through a h...

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Section: Electrical Propertiesmentioning

confidence: 99%

Selected Properties of Pyrolytic Ta[sub 2]O[sub 5] Films

Knausenberger¹,

Tauber²

1973

J. Electrochem. Soc.

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“…The role played by oxygen in determining the properties of sputtered tantalum films has been the subject of considerable study over recent years (Gerstenberg and Calbick 1964;Maissel 1962;Steidel and Gerstenberg 1969;Westwood and Livermore 1970;Westwood and Waterhouse 1971). Its importance in the formation of P-Ta (Read and Altman 1965) now appears to be well established (Westwood and Livermore 1970;Westwood and Waterhouse 1971 ;Waterhouse et al 1971) but the electrical properties, specifically its negative temperature coefficient of resistance (TCR), are not well understood.…”

Section: Introductionmentioning

confidence: 99%

“…Its importance in the formation of P-Ta (Read and Altman 1965) now appears to be well established (Westwood and Livermore 1970;Westwood and Waterhouse 1971 ;Waterhouse et al 1971) but the electrical properties, specifically its negative temperature coefficient of resistance (TCR), are not well understood. Gerstenberg and Calbick (1964) suggested that the conduction mechanism might be "activated" i.e., of the form…”

Section: Introductionmentioning

confidence: 99%

Effect of Oxygen on the Temperature Dependence of Electrical Properties of Reactively Sputtered Tantalum Films

Waterhouse¹,

Westwood²

1971

Can. J. Phys.

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The negative temperature coefficient of resistivity (TCR) displayed by p-Ta, which has thus far not been satisfactorily explained, has been examined by measuring the variation of electrical resistivity with temperature, from -2S300 OK, and by measuring the Hall coefficients, at room temperature and a t 77 OK, of films containing up to -60 at.% oxygen. The Hall measurements indicate carrier concentrations of -loz2 ~m -~ and mobilities of -1 cm2/V s. The analysis of the results has considered the granular structure of the films and has subsequently compared these results with an 'activated tunneling' model of conduction. Theoretical calculations which assume the film to be comprised of cubic grains separated by T a 2 0 5 agree well with the experimental measurements.Metallic conduction still appears to be contributing to the film properties even at the highest oxygen concentrations of the present investigation.Le coefficient negatif de variation de resistivite en fonction de la temperature (TCR) du p-Ta, qui n'a pas encore ete expliquk de f a~o n satisfaisante, a etC examine en mesurant la resistivite Clectrique en fonction de la temperature de 20 a 300 "K et en mesurant, a temperature ambiante et a 77 OK, les coefficients de Hall de films contenant jusqu'a 60% d'oxygene atomique. Les mesures d'effet Hall indiquent des concentrations de porteurs de cm-3 et des mobilites de -1 cm2/V s. Lors de I'analyse des resultats on a tenu compte de la structure granulaire des films et on a subsequemment compare ces resultats avec un modele "d'effet tunnel active" de la conduction. Des calculs theoriques, faits en supposant que le film est compose de grains cubiques sCparCs par Ta205, concordent tres bien avec les mesures expirimentales.La conduction metallique contribue aux proprietes du film mCme avec les plus fortes concentrations en oxygene utilisees au cours de cette investigation.

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“…Their method provided an average value of P over an area of 25 cm2 and they reported considerable variations in a with position on this sample. Gerstenberg and Calbick (1964) also reported increasing oxygen content of tantalum films as a became increasingly negative. Although they reported that the films always con-sisted of the b.c.c.…”

Section: Discussionmentioning

confidence: 88%

“…Coulometric measurements have been used previously by Gerstenberg (1966) to determine the oxygen content of Ta films but there appear to be inconsistencies in his analysis. For example, although he obtained values off less than unity in some samples, he gives a value for the atomic percent oxygen P. For those samples with f larger than unity, the values of P calculated by Gerstenberg (1966) are different from those obtained by the substitution of his data in the equation presented in this work.…”

Section: This Work Bulk Tamentioning

confidence: 99%

`Anodic Oxidation of Tantalum

Wilcox¹,

Westwood²

1971

Can. J. Phys.

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Anodization current efficiency measurements were used to determine the oxygen content of sputtered tantalum films. Films consisting mainly of b.c.c. Ta had less than 5 at. % oxygen while 'normal' j3-Ta contained 10-15 at. % oxygen. Films with a more negative temperature coefficient of resistance had a higher oxygen content.The field strength required to cause oxide growth on 'normal' j3-Ta was lower than for b.c.c. Ta films or for oxygen rich j3-Ta films. The cause of these changes in field strength is not known. The dielectric constants of the oxides grown on all films were the same, but depended on the measurement conditions and history of the oxide.

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Properties of Anodic Films Formed on Reactively Sputtered Tantalum

Cited by 46 publications

References 7 publications

Selected Properties of Pyrolytic Ta[sub 2]O[sub 5] Films

Selected Properties of Pyrolytic Ta[sub 2]O[sub 5] Films

Effect of Oxygen on the Temperature Dependence of Electrical Properties of Reactively Sputtered Tantalum Films

`Anodic Oxidation of Tantalum

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