Boron doses of 1×1012–5×1015/cm2 were implanted at 60 keV into 1-μm-thick polysilicon films. After annealing at 1100 °C for 30 min, Hall and resistivity measurements were made over a temperature range −50–250 °C. It was found that as a function of doping concentration, the Hall mobility showed a minimum at about 2×1018/cm3 doping. The electrical activation energy was found to be about half the energy gap value of single-crystalline silicon for lightly doped samples and decreased to less than 0.025 eV at a doping of 1×1019/cm3. The carrier concentration was very small at doping levels below 5×1017/cm3 and increased rapidly as the doping concentration was increased. At 1×1019/cm3 doping, the carrier concentration was about 90% of the doping concentration. A grain-boundary model including the trapping states was proposed. Carrier concentration and mobility as a function of doping concentration and the mobility and resistivity as a function of temperature were calculated from the model. The theoretical and experimental results were compared. It was found that the trapping state density at the grain bound was 3.34×1012/cm2 located at 0.37 eV above the valence band edge.

IODINATION OF METALS 701be the rate-determining factor in the linear reaction. The most probable mechanism is the chemisorption of iodine atoms and the introduction of chemisorbed ions in the gas/iodide interface. The number of adsorbed iodine atoms staying at the interface is proportional to the number of impinging iodine molecules on the surface and the time of adsorption during which the adsorbed molecules stay at the surface before reevaporation (20). If we assume a heat of adsorption of 9 kcal/ mote which is a possible value for the gas consisting of heavy molecules, then the decrease of the adsorbed atoms is about 5-fold between 200 ~ and 300~C, and is in good agreement with the observed decrease of the reaction rate. The effect of adsorption on the linear reaction has been observed between the reactions performed at different iodine pressures. That is, the reaction rate changed from 2.32 to 28.8 (~g/cm2)/sec as the iodine pressure was raised from 0.032 to 0.16 Torr at 300~ while it was little changed at 25~ in the parabolic reaction, as shown in a previous note (9). The increase of the reaction rate, however, is much larger in comparison with the increase of the impinging molecules, which is 5 times between pressures of 0.032 and 0.16 Torr. The result may be ascribed to the increase of a condensation coefficient (the probability that an impinging molecule is adsorbed at the surface) with increasing temperature; the coefficient may increase about 2.5 times between 0.032 and 0.16 Torr.Since the diffusion rate decreases with increasing layer thickness, the linear rate is applicable only to the point where the diffusion rate becomes comparable with the rate of the phase boundary reaction. With further growth of the protective layer, the diffusion ra~e becomes the rate-determining factor (12,(16)(17)(18)(19), and the parabolic rate relationship prevails. The tarnish constants above 150~ which were shown by Nagel and Wagner (5) Weiss (6), can be assumed to be those corresponding to this parabolic reaction.The iodination of lead films followed the parabolic relationship, although in the experiments below 100~ the definite parabolic relationship was not observed because of the tarnishing of the surface by the residual gas. The conduction mechanism of the lead iodide is very complicated because both lead and iodine ions participate in conduction (21). Since the ionic conduction is predominant in any case and since parabolic rate behavior was observed, it can be concluded that electronic conduction through the lead iodide layers is the rate-determining step of the iodination process.ABSTRACT Deposition of silicon on thermally grown silicon dioxide substrates by pyrolysis of silane in argon is postulated as a three-step process involving adsorption and decomposition of silane on, and desorption of hydrogen from the substrate surface. This postulate was verified by experimental data. The morphology of the polysilicon films was strongly affecled by the cleaning process employed before the silicon dioxide was grown. To ...

The piezoresistive gage factor of boron-doped CVD polysilicon films deposited with a boron-to-silicon ratio of 2×10−4–1.2 ×10−2 on an aluminum-oxide-insulated molybdenum substrate is found to be between 15 and 27. Annealing increases the gage factor. The higher the doping, the lower is the gage factor. Over the range 20–140 °C, the gage factor is not temperature sensitive if the boron-to-silicon ratio is higher than 2×10−3 during deposition. The temperature dependence increases as the doping concentration is decreased. Our analysis shows that the piezoresistive properties in polysilicon is mainly due to the bulk crystallites.

Articles you may be interested inStudy of the annealing kinetic effect and implantation energy on phosphorus-implanted silicon wafers using spectroscopic ellipsometry Polycrystalline silicon films implanted with 1 X 10 1 ' to 7.8 X 10 15 /cm' doses of boron and phosphorus were isochronally annealed up to lIOO'C. Annealing below 6OO'C removes the radiation damage created by the implantation process. For doses higher than 1 X 10 14 /cm' an abrupt decrease in sheet resistance takes place between 650 and 700 'C. Hall measurements show that this decrease is the result of a large increase in both the carrier concentration and mobility. Electron-reflection diffraction patterns show that recrystallization takes place within this temperature range. Annealing above 700'C only causes a small further decrease in the sheet resistance.

Die Abscheidung von Si durch Pyrolyse von SiH4 in Ar an thermisch erhaltenen SiO2‐ Substraten wird als ein Drei‐Stufen‐Vorgang angesehen , der eine Adsorption und Zersetzung von SiH4 an der Substratoberfläche und eine Desorption von Wasserstoff aus der Oberfläche des Substrats einschließt. Diese Annahme wird experimentell bestätigt.