Yasuo Yahagi

Impact of Scaling on Neutron-Induced Soft Error in SRAMs From a 250 nm to a 22 nm Design Rule

Trends in terrestrial neutron-induced soft-error in SRAMs from a 250 nm to a 22 nm process are reviewed and predicted using the Monte-Carlo simulator CORIMS, which is validated to have less than 20% variations from experimental soft-error data on 180-130 nm SRAMs in a wide variety of neutron fields like field tests at low and high altitudes and accelerator tests in LANSCE, TSL, and CYRIC. The following results are obtained: 1) Soft-error rates per device in SRAMs will increase x6-7 from 130 nm to 22 nm process; 2) As SRAM is scaled down to a smaller size, soft-error rate is dominated more significantly by low-energy neutrons (<; 10 MeV); and 3) The area affected by one nuclear reaction spreads over 1 M bits and bit multiplicity of multi-cell upset become as high as 100 bits and more.

Terrestrial neutron-induced soft errors in advanced memory devices

Terrestrial Neutron Spectrometry and Dosimetry Irradiation Test in the Terrestrial Field Neutron Irradiation Test Facilities Review of Experimental Data and Discussions Monte Carlo Simulation Methods Simulation Results and Their Implications International Standardization of Neutron Test Method Summary and Challenges.

A Novel Feature of Neutron-Induced Multi-Cell Upsets in 130 and 180 nm SRAMs

Bit-multiplicity of neutron-induced single event upsets (SEU) in CMOS SRAMs formed with 130 and 180 nm technologies was analyzed using mono-energetic, quasi-mono-energetic, and spallation neutron sources in various accelerator facilities. The energy dependence of the ratio of multi-cell upsets (MCUs) to the total number of upsets can be described by a Weibull-type function with the threshold energy of the MCU. The 130 nm SRAMs show a novel feature of multi-cell upsets (MCUs) including frequency distribution of the multiplicity of error bits. In the case of the 130 nm SRAM, the probability function of the MCU can be expressed as a sum of exponential and Lorentzian functions of the multiplicity of error bits. According to previous results of 3-dimensional device simulation, the Lorentzian component can be due to bipolar action.

Threshold energy of neutron-induced single event upset as a critical factor

The physical modeling of neutron-induced SEU (single event upset) is usually described by high energy neutrons above a few tens MeV. In JESD89 it is assumed that the sensitivity of the concerned device to neutrons with energies less than 10 MeV is low enough to be ignored. The scaling of semiconductor devices can cause their higher susceptibility even to neutrons of several MeV, where the flux of terrestrial neutron is relatively high enough to affect SER (soft error rate) -estimation from data acquired by accelerated test. Although the information on the threshold energy of neutron-induced SEU becomes more important, the definition of the threshold energy of neutron-induced SEU is not still an obscure issue. This work focuses on importance of the threshold energy of neutron-induced SEU. It is demonstrated how the threshold energy of neutron-induced SEU affects SER-estimation by accelerated test with (quasi-) mono energy neutrons.

Versatility of SEU function and its derivation from the irradiation tests with well-defined white neutron beams

The soft-error rate estimation method used for monoenergetic and quasimonoenergetic neutron beams is validated by the well-defined white neutron spectra generated at the Los Alamos Neutron Science Center (LANSCE), Los Alamos, NM, including with regard to the single event upset (SEU) threshold energy. Moreover, it is demonstrated that the neutron energy dependence of the SEU cross section is able to derived from neutron irradiation tests for several different white neutron beams by using unfolding technique.

Self-consistent integrated system for susceptibility to terrestrial neutron induced soft-error of sub-quarter micron memory devices

Concerns about Single Event Upset (SEU) induced by terrestrial neutron at the ground are growing as scaling down of semiconductor device proceeds. A highly integrated procedure named SECIS (SElf-Consistent Integrated System for susceptibility to terrestrial neutron soft-error) is proposed to estimate soft-error rate (SER) at any place on the earth. A good agreement is obtained from SECIS within 35% error between the measured and estimated SERs in three locations in Japan.

Single event effects as a reliability issue of IT infrastructure

Terrestrial neutron is being recognized as a major source of single event effects (SEEs) including soft-error of semi-conductor devices at the ground level. As semiconductor device scaling nose-dives into sub 100nm, the possible threat from single event effects is apparently growing onto IT systems that require a great number of electron devices. The modes of SEEs, however, are reportedly diverging on annual base and thus methods to quantify such effects are getting more and more complicated even for device level. In the present paper, current situation on neutron-induced SEEs are reviewed and benchmark studies are proposed to make the effects of SEEs on the reliability of IT infrastructure clear.

SEALER: Novel Monte-Carlo Simulator for Single Event Effects of Composite-Materials Semiconductor Devices

A Monte-Carlo simulation code SEALER was developed for neutron-induced single event upset of semiconductor devices at the ground level, in which composite material effects are fully simulated. Any size and structures of 8 composite material such as Si, SiO2, Si3N4, Ta2O5, WSi2, Cu, Al, TiN can be included for analyses of nuclear spallation reactions and charge collection mechanisms. Some preliminary implications of composite material effects are demonstrated including an apparent contribution of elastic scattering to single event upset in lower energy region as low as 2 MeV or even lower.

Precision rubbing supported by fine process analysis

Rubbing is still the only practical method by which to attain reliable liquid-crystal alignment in LCD manufacturing, although a small number of optional Methods have been proposed. In order to be able to realize higher alignment performance for future finer displays, we need to look at not only the purpose of the process itself, which is molecular ordering in the alignment layer, but also undesirable side effects, such as contamination, triboelectric charging, and particle generation. The present paper examines the type of surface contamination that occurs during the rubbing process from a fine chemical point of view as well as rubbing-related problems. A number of ideas are proposed by which to cope with the aforementioned problems, so that this traditional and well-understood process can be applied much more effectively.

A Quantitative Analysis of Neutron-Induced Multi-Cell Upset in Deep Submicron SRAMs and of the Impact Due to Anomalous Noise

In this work, the multiplicity of neutron-induced upsets of SRAMs with 130/180 nm technologies is analyzed by using several neutron beams and RTSER. The neutron peak-energy dependence of the ratio for MCU to the total number of upsets can be described by Weibull-type function with a threshold energy for the MCU. As a result of the 130nm SRAM test, the probability function of MCU can be approximated as a superposition of an exponential and a Lorentzian. We also demonstrate that the MCU/SEU ratio obtained by real-time measurements (RTSER) cross over the ASER data at around 20-40MeV. This indicates that the MCU obtained from ASER test using high neutron peak energy more than 50MeV tends to lead to an excessive estimation of the MCU/SEU ratio compared to the RTSER measurements. In addition, the effect due to anomalous noise has been studied and the phenomenon could be suggested as some special signs related to a geophysical mechanism and is expected to be investigated further with more analysis.