In this study, {100} cracks were found in Czochralski (Cz) silicon wafers grown in the atmosphere including hydrogen under the condition of a low V c /G c (V c , growth rate; and G c , temperature gradient) although the {100} plane is not a cleavage plane of silicon crystals. It was also found that dislocation clusters were associated with the as-grown defects. To reveal the mechanism behind the crack formation, the process of introducing interstitial and hydrogen atoms into a Cz-Si crystal upon solidification was imitated by applying ion irradiation into Cz silicon wafers under three different conditions: silicon ions and hydrogen ions, silicon ions only, and hydrogen ions only. In this case, {100} cracks were only found in the wafer irradiated with both silicon and hydrogen ions. This suggests that the existence of dislocations in silicon is necessary for crack formation. Density functional theory calculations showed that the cleavage energy was decreased by the arrangement of hydrogen atoms on a {100} plane of a silicon crystal, which can explain the formation of {100} cracks during solidification.

The change in the mechanical strength of silicon wafers due to the impurity atoms introduced as dopants in them was investigated by a three-point bending test and finite element method (FEM) simulation. As representatives of p-type and n-type dopant species, boron and phosphorus were used. Stress–strain curves were obtained with samples having three levels of impurity concentrations, and the upper yield stresses were evaluated to investigate the influence of the impurities on the mechanical strength. In the case of boron in the experimental results, there was no change in the strength with the doping concentration, and the upper yield stress remained constant. Contrastingly, the phosphorus-doped samples showed a decrease in the upper yield stress with the doping concentration increase. FEM simulation of the three-point bending test and analysis of the simulation results showed that the dislocation velocity, i.e., the activation energy of the dislocation motion, varies according to the concentration. This suggested that the dislocation velocity changed based on the concentration of the added impurities strongly influenced the mechanical strength of silicon.

This study investigates the effects of the secondary defects caused by ion implantation on wafer strength. The change in wafer strength with the ion implantation amount has been examined after implanting phosphorus or boron ions into wafers with and without heat treatment. Ion implantation defects have been observed using transmission electron microscopy after ion implantation and recovery annealing. The three-point bending tests carried out with the ion implanted samples show that the upper yield stress, which represents wafer strength, decreases owing to implantation-induced secondary defects. In addition, the strength of the wafers with a low oxygen concentration is lower than that of the wafers with a high oxygen concentration. However, the rate of decrease in wafer strength as a function of implantation amount is not affected by the oxygen concentration; it only depended on the implanted element.

When we go shopping, we see that shoppers take merchandise and return it to the shelf. With focusing on this action of shopper, this research adds values to the analysis of POS-system by analyzing the action. In this paper, this action is called "confused-behavior". This paper propose a system which gets shopper's action by using RF-ID tags and explains cause of the actions. The scopes of this paper are development and evaluation of proposed system. The relation between shopper's action and usage is examined and the system is designed by considering three types of shopper's actions. The system is evaluated from the point of view of certainty to detect actual action during shopping.