Michio Kida

Effects of Thermal History on the Formation of Oxidation-induced Stacking Fault Nuclei in Czochralski Silicon during Crystal Growth

The formation of oxidation induced stacking fault (OSF) nuclei during Czochralski silicon crystal growth was investigated using crystals subjected to in situ annealing for either 1 or 4 hours by halt of pulling during crystal growth. The effects of in situ annealing at temperatures from about 1160° C to 1030° C can be summarized as follows. In positions held at about 1090° C and 1030° C, the radial distributions of OSFs, LSTDs (light scattering tomography defects), and OPs (oxygen precipitates after annealing) changed greatly. In the position held at about 1090° C, large LSTDs were formed but the OSF-ring disappeared in the region where it should have been present if pulling was not halted. In the position held at about 1030° C, the defects in the OSF-ring grew, its width increased, and the OP density both inside and outside the OSF-ring decreased with holding time. However, the radial distribution of defects at the position held at about 1160° C was similar to that for a reference crystal which was not subjected to halt of pulling. These results indicate that these defects were not formed until 1160° C, the large LSTDs were formed at 1160–1090° C, the OSF nuclei were formed at 1090–1030° C, and the OP nuclei inside and outside the OSF-ring were formed below 1030° C. We discussed the influence of point defects upon the formation of OSF nuclei.

A numerical study on oxygen transport in silicon melt in a double-crucible method

Abstract Oxygen transport in the silicon melt in the double-crucible method was simulated by using the k -ϵ turbulent flow model. The high eddy diffusivity of oxygen calculated from the eddy dynamic viscosity is postulated in the present model. In the mechanisms found in the simulation, the small distance between the hot inner crucible and the melt/crystal interface was the most dominant reason for the increase of the oxygen concentration in the case of the double-crucible method.

A new technique for controlling the dopant concentration in the double-crucible method

Abstract A new doping procedure for keeping the dopant concentration of the crystal constant in a continuous Czochralski method, using a double-walled crucible, is proposed. In this method the initial concentrations in the inner and the outer crucibles are set to be equal. Therefore, the equalizing phenomena of the concentrations between the two crucibles in the initial stage do not have to be considered. The strategy for doping control in this new method is analyzed using a one-dimensional mathematical model.

Bonding Process for Nanoscale Wiring Using Carbon Nanotube by STM Tip

A nano-scale bonding process using a multi-wall carbon nanotube (CNT) has been successfully applied in a scanning electron microscope (SEM)/scanning tunneling microscope (STM) combined system. Under the SEM observation, a Ti-coated STM tip was approached onto a CNT bridging Ti pads, which is patterned with a 4 µm gap on a SiO2 surface, to investigate the conduction property of the CNT. A voltage pulse of 12 V peak and 50 µs duration was applied in order to deposit Ti clusters onto the CNT, which is well known as a field evaporation process in the STM regime. The two-terminal current-voltage characteristics of the CNT have been improved from a nonlinear behavior at 2.5 V of 208 kΩ to a linear one of 1.8 kΩ.

Annealing Behavior of Light Scattering Tomography Defect in the Denuded Zone of Si Wafers

Light scattering tomography defects (LSTDs) have been non-destructively detected in bulk and near the surface of a Si wafer by Brewster angle illumination of infrared light scattering tomography (IR-LST). We investigated the annealing behavior of grown-in LSTDs that exist in a layer of 0 to about 20 µm depth from the wafer surface. Grown-in LSTDs were detected before annealing. Annealing behavior of such grown-in LSTDs was studied by the three-step annealing to form the denuded zone (DZ) of about 40 µm. As a result, the LSTDs mostly remained in the DZ after the three-step annealing. However, the change in the scattering intensity of the grown-in LSTDs was detected. This change suggests that the volume and/or structure was changed by the annealing treatment.

A Numerical Study of the Influence of Feeding Polycrystalline Silicon Granules on Melt Temperature in the Continuous Czochralski Process

Abstract Temperature change was simulated using a solid body rotating melt model when solid polycrystalline silicon granules were supplied to a melt in a double-crucible method. Only heat conduction was considered in the analysis. The influence of the crucible rotation rates and of the initial temperature of the supplied silicon was investigated systematically and quantitatively. The influence of the crucible rotation rate was stronger than expected, which suggests that the crucible rotation rate cannot be lowered too much because of the possibility of the melt solidifying between the inner and outer crucibles.

Bonding Process for Nano-Scale Wiring using Carbon Nano-Tube by Scanning Tunneling Microscope Tip

l, Introduction Carbon nano-tube (CNT) is expected to be applicable for various types of nano-scale devices such as single-electron ffansistor [1], field emitter l2l, and so on, because of the scale of the size. Recently, there is a great attention on the ability of the carrier transmission. It could be used as a material of wiring line in future LSI circuits, if the handling technique of CNT is established enough. Because it is predicted the carrier transport in CNT would be described as a ballistic regime, if there was no defect on it t3l. Moreover, it should be remarkable that a maximum current density of CNT is more than 2 orders comparing with a conventional wiring material in a LSI such as Cu or Al. Although one could reduce the size of semiconductor device, there remains a crucial problem of an electrical migration of metallic materials. In this matter, the usage of CNT for the wiring has highly advantageous for nano-scale circuit. However, because of the difficulty of the handling of CNT, it is difficult to realize such a CNT wiring system. If we could use the system like a wire bonding machine, it would be convenient and show a high performance for a bonding in nano-scale regions. In order to realize such a system, it is necessary to establish roughly two important processes. One is the positioning of CNT at an aimed area. Nowadays, a development of nano-manipulation techniques using a probe of atomic force microscope (AFM) or nano-tweezers using a pair of CNT attached on the top of a probe, a manipulation and a positioning of CNT is getting developed somewhere. Another important process is the bonding of CNT on metallic electrodes to have a good ohmic contact between CNT and metallic pads. As for such a possible method, we propose a nano-scale bonding process induced by a voltage pulse using a scanning tunneling microscope (STM) tip. The advantageous of this method is that we can deposit nano-scale metallic dots at anyplace on a metallic pad and also cover a CNT by them, which would bring a good electrical and mechanical contact between CNT and a pad. In this paper, we demonstrate a nano-scale bonding process of CNT-CNT or CNT-metallic pad by using STM tip and show the development of the electrical transport properties.