Strain Dependence of Dielectric Properties and Reliability of High-k Thin Films
The effect of strain on both electronic and structural characteristics of HfO2 used for sub-50-nm semiconductor devices was analyzed by a quantum chemical molecular dynamics analysis. The band structure of HfO2 is strongly affected by strain in the film. Based on the change rate of band gap obtained from our simulations, the strain sensitivity of the relative permittivity of HfO2 film is predicted to about 2.4%/1%-strain. The predicted strain sensitivity was validated quantitatively by measuring the change of the capacitance of MOS capacitors using a HfO2 gate dielectric film. It is very important, therefore, to minimize the mechanical strain in the dielectric film to assure the reliability of MOS transistor.
Mechanical Stress Simulation for Highly Reliable Deep-Submicron Devices
We have improved the mechanical reliability of deep-submicron semiconductor devices by applying a simulation technique. Typical kinds of damages that reduce the reliability are dislocations in silicon substrates, delamination or cracking of thin films, and deterioration of electronic characteristics of devices. The mechanical stress that develops in device structures is caused by not only mismatches in thermal expansion coefficients among thin film materials but also intrinsic stress of thin films such as poly-silicon and silicides. Fine patterning by dry etching makes sharp edges and they also cause stress concentration and thus high stress. The manufacturing processes in which stress mainly develops are isolation, gate formation, and interconnect formation. We have developed methods for reducing the stress in each of the above-mentioned process. This stress reduction is very effective for highly reliable manufacturing. Finally, we clarify the effect of the residual stress in transistor structures on shift in the electronic characteristics of MOS transistors. key words: semiconductor, transistor, residual stress, stress
Adolescent sexual offenders: incidence of childhood maltreatment, serious emotional disturbance, and prior offenses.
Adolescents incarcerated for sexual offenses were compared to those incarcerated for other crimes on measures of prior child abuse and neglect, serious emotional disturbance, and involvement in child welfare and the juvenile justice system. Sexual or physical abuse was more common than neglect among sexual offenders with fewer than three prior maltreatment reports. Sexual offenders were twice as likely to be receiving special education services for severe emotional disturbance, and were usually incarcerated later than other offenders. Implications for research and practice are discussed.