The optical absorption edge (indirect energy gap) for PbTe was determined in the temperature range of 80°–520°K. It was found that dEg/dT had a value of 4.1×10−4 eV/°K in the temperature range from 80°–350°K, while above 400°K, dEg/dT was approximately zero. The low-temperature linear portion extrapolated to 0.19 eV at 0°K while the high-temperature portion extrapolated to 0.36 eV. This behavior is explained by a two-valence band model, one active at low temperatures, the other in the high temperature range. A thermal energy gap of approximately 0.36eV was obtained from the temperature variation of resistivity and Hall coefficient in the intrinsic range, 500°–900°K. This value agrees with the high temperature optical data extrapolated to 0°K, thus correlating the optical and thermal energy gaps.

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...

Zirconium dioxide (ZrO2) films in the thickness range of 500-8000A havc been prepared by chemical vapor deposition in the temperature range of 800 ~ 1000~ The films were identified as fine-grained (~325A), nearly stoichiometric, monoclinic ZrO2, using electron microprobe analysis, infrared absorption, and transmission electron microscopy. The films exhibited r e m a r kable resistance to most aqueous acids and bases, although slight etching occurred in hot (220~ phosphoric acid. The deposits had an index of refraction of 2.1 -+ 0.1 at 546 nm and an optical energy gap of 5.12 eV. ZrO2 deposited on silicon offered little resistance to Na diffusion at 600~ while films deposited on thermal SiO2 were a good barrier due to pile-up of the Na near the ZrO2/SiO2 interface. The current density, J, depended on the field, E, as J -~ A E n, where n was 6 for the metal biased negatively and 2.75 or 5, depending on the magnitude of the field, for the opposite polarity. The dielectric constant in the frequency range of 5 x 10 S to 1 x l0 s Hz was relatively independent of frequency near 300~ and equal to approximately 18, however some dispersion was noted near 573~ The a-c conductivity could be represented by =ac ~ Cy~ where 5 is the measuring frequency and ~ a temperature dependent parameter, decreasing from ~1 at 300~ to ~0.5 at 573~ The dielectric strength of the films varied between 1 to 2 x 106 V/cm, independently of thickness and polarity. High frequency (1 MHz) C-V measurements indicated the presence of negative surface charge, which varied between --6 x 10 n to --1 x 1012 cm -2. The structures exhibited instability under negative bias, indicative of negative charge being injected into the insulator. C-V measurements on the double dielectric system (ZrO2/SiO2) showed that the presence of ZrO2 caused a flatband voltage displacement ~ +0.8V. In addition, the flatband voltage shifted as a function of time under negative bias and was found to obey the relationship aVFB -'-K log t.Recent developments in microelectronics, such as integrated circuit passivation and IGFET technology, have engendered extensive research in the preparation and characterization of insulating thin films (1). Much of the effort has been directed to SiO2, SlaY4, and Al203. Recently, alternatives to these materials have been sought. TiO2 (2) and Nb205 (3) have been investigated. It has been found that chemical vapor deposition (CVD) in the temperature range of 600 ~ 1000~ produces films with the most desirable properties for the above applications.A refractory oxide that has not been investigated in detail is zirconium dioxide (ZrO2). T h i s material is characterized by low electrical conductivity and extreme chemical inertness. Much of the information available on ZrO2 has been obtained on relatively impure bulk, sintered material. This paper reports on the preparation of ZrO2 films by CVD, and a survey of the optical, chemical, electrical, and interfacial properties of the resulting films. Film PreparationThe preparation of oxide films by CVD has been...

This study was directed toward exploring the relationship between the implant conditions and the depth and nature of the amorphous layers generated in silicon. Interest in amorphous layer morphology stems from its role in affecting crystal defects remaining after amorphous-to-crystalline transformation. High-dose implants of As, P, and B were used to generate buried and surface amorphous layers at slightly higher than room temperature. The amorphous layer depths were measured and the depth-fluence and depth-energy relationships were compared with Brice’s analysis. It was found that good fits were obtained for a threshold damage density of 2.5×1020 keV cm−3 for As and 1.0×1021 keV cm−3 for P. For B, the results could be described by a threshold damage density of 5.0×1021 keV cm−3 or greater. Lower weight ion implantations exhibit a greater tendency to generate buried amorphous layers as well as to generate amorphous layers which include a smaller fraction of the total implanted fluence than is found for heavier ion implantations. These two factors make it more likely for residual crystal defects to be associated with lower weight ion implant distributions.

A series of {100} silicon wafers were implanted with As ions over the range of 1×1013 at. cm−2 to 1×1016 at. cm−2 with energies of 50, 100, and 190 keV, using a commercial ion implanter, the Varian 200-DF4. Two end stations were used, the Waycool which provided good contact between the wafers and a thermal sink and the Wayflow, which holds the wafers without any provision for obtaining such contact. Precise values of amorphous layer depth were obtained by a newly developed technique, using direct measurement of the depth exposed by a tapered groove. For the Waycool implanted wafers, the amorphous layer depth increased with dose. For the Wayflow wafers, the amorphous layer depth increased to a maximum and then decreased, finally disappearing at the higher doses. Combining shallow angle-lapping, etching, and profilometry, it was possible to study the submerged amorphous layers originating at the threshold dose for the 190-keV implantations. For Waycool implanted wafers, the surface crystalline layer thickness decreased and disappeared with increased dose. For Wayflow wafers, the surface crystalline layer increased with dose, meeting the crystalline substrate which grew from the opposite direction. The differences in defect structure between Waycool and Wayflow implanted wafers are attributed to the dynamic annealing which occurs during implantation. The defects remaining after a low temperature transformation anneal are correlated to dynamic annealing effects.