Ryozo Takasu

Simultaneous measurement of soft error rate of 90 nm CMOS SRAM and cosmic ray neutron spectra at the summit of Mauna Kea

We carried out simultaneous measurement of SERs and cosmic ray neutron spectra for the first time. We measured SERs using 90 nm CMOS SRAM chips and measured neutron spectra using a Bonner multisphere spectrometer. We carried out the SER field measurement at the 4200 m summit of Mauna Kea, which is the most suitable place for SER field measurements because the neutron flux is over 10 times greater there than that at sea level. Therefore, we could avoid making field measurements that usually require a long measuring time (about a year) to obtain sufficient accuracy.

Technological Trends of Soft Error Estimation Based on Accurate Estimation Method

Soft errors have become a serious problem in very large scale integrated circuit (VLSI) circuits. Although the accurate estimations of neutron- and α-induced soft error rates (SERs) are essential, the magnitude relationship between neutron- and α-induced SERs has long been unclear. Recently, a sensitive dosimetry vacuum alpha ray tracking method has been developed and it has enabled us to eliminate the uncertainty of the rate of α-particle emission from materials. In this study, technology trends of SERs in static random access memory (SRAM) and latch circuits are investigated by neutron- and α-accelerated tests and SER simulations. The magnitude relationship between neutron- and α-induced SERs is clearly discussed on the basis of newly obtained α-dose rates.

New QCM Sensor for Real-time AMC Detection in SMIF Pods

We have developed a new type of QCM sensor for real-time detection of chemical contaminant emission in SMIF pods. Because there is no need to modify SMIF pods when applying this sensor, introducing the QCM system to fabrication lines is very easy.

A novel method for accurately estimating alpha-induced soft error rates

We have developed a sensitive dosimetry, vacuum /spl alpha/-tracking, and used it to measure dose rates of /spl alpha/-particle emission in order to estimate /spl alpha/-induced soft error rates. We found that the detection limit of the developed dosimetry is 3.2/spl times/10/sup -5/ /spl alpha/ph/spl middot/cm/sup -2/, approximately 30 times more sensitive than that of conventional dosimetry. We used the newly obtained dose rates of LSI materials in accelerated tests and simulations to demonstrate that the developed method provides drastically more accurate soft error rate estimation.

A Width-Variable Window Attention Model for Environmental Sensors

Air pollution is a major problem in modern cities and developing countries. Fine particulate matter (PM2.5) is a growing public health concern and become the most serious air pollution. In this study, we formulate the PM2.5 inference problem in conventional environmental sensors as a sequence-to-sequence problem. We adopt the encoder-decoder LSTM (Long short term memory) framework to solve the PM2.5 inference problem. A novel width-variable window attention mechanism is proposed for the encoder-decoder LSTM system. The proposed method learn the position and width of the attention window simultaneously. The proposed method is evaluated on large scale data and the experimental results show that it achieves better performance on two datasets with different concentration of PM2.5.

Highly selective and sensitive gas sensors for exhaled breath analysis using CuBr thin film

We have examined a p-type semi-conductor CuBr thin film used for sensor devices that indicates the order of sensitivity to ammonia in parts per billion (ppb). The CuBr thin film also indicates excellent selectivity to ammonia among reductive gases, which additionally suggests its capacity for fast quantification of the order of seconds. Moreover, CuBr thin film can be adapted to a high-sensitivity aldehyde sensor by a surface modification. Since the fabrication process of CuBr thin film is compatible with an ordinal CMOS process, there is a potential for development into highly integrated and low power consumption sensor devices. These properties make CuBr thin film a promising candidate as a gas sensing material for human-breath analysis.