Temperature and voltage measurement for field test using an Aging-Tolerant monitor

Measuring temperature and voltage (T&V) in a current VLSI is very important in guaranteeing its reliability, because a large variation of temperature or voltage in field will reduce a delay margin and makes the chip behavior unreliable. This paper proposes a novel method of T&V measurement, which can be used for variety of applications, such as field test, online test, or hot-spot monitoring. The method counts frequencies of more than one ring oscillator (RO), which composes an aging-tolerant monitor. Then, the T&V are derived from the frequencies using a multiple regression analysis. To improve the accuracy of measurement, three techniques of an optimal selection of RO types, their calibration, and hierarchical calculation are newly introduced. In order to make sure the proposed method, circuit simulation in 180-, 90-, and 45-nm CMOS technologies is performed. In the 180-nm CMOS technology, the temperature accuracy is within 0.99 °C, and the voltage accuracy is within 4.17 mV. Furthermore, some experimental results using fabricated test chips with 180-nm CMOS technology confirm its feasibility

Temperature and Voltage Estimation Using Ring-Oscillator-Based Monitor for Field Test

Field test is performed in diverse environments, in which temperature varies across a wide range. As temperature affects a circuit delay greatly, accurate temperature monitors are required. They should be placed at various locations on a chip including hot spots. This paper proposes a flexible ring-oscillator-based monitor that accurately measures voltage as well as temperature at the same time. The measurement accuracy was confirmed by circuit simulation for 180 nm, 90 nm and 45 nm technologies. An experiment using test chips with 180 nm technology shows its feasibility.2014 IEEE 23rd Asian Test Symposium (ATS), 16-19 Nov. 2014, Hangzhou, Chin

On-Chip Delay Measurement for Degradation Detection and Its Evaluation under Accelerated Life Test

Periodical delay measurement in field is useful for not only detection of delay-related faults but also prediction of faults due to aging. Logic BIST with variable test clock generation enables on-chip delay measurement in field. This paper addresses a delay measurement scheme based on logic BIST and gives experiment results to observe aging phenomenon of test chips under accelerated life test. The measurement scheme consists of scan-based logic BIST, a variable test clock generator, and digital temperature and voltage sensors. The sensors are used to compensate measured delay values for temperature and voltage variations in field. Evaluation using SPICE simulation shows that the scheme can measure a circuit delay with resolution of 92 ps. The delay measurement scheme is also implemented on fabricated test chips with 180 nm CMOS technology and accelerated test is performed using ATE and burn-in equipment. Experimental results show that a circuit delay increased 552 ps when accelerated the chip for 3000 hours. It is confirmed that the on-chip delay measurement scheme has enough accuracy for detection of aging-induced delay increase.26th IEEE International Symposium on On-Line Testing and Robust System Design (IOLTS 2020), 13-15 July, 2020, Napoli, Italy（新型コロナ感染拡大に伴い、オンライン開催に変更

DART: Dependable VLSI Test Architecture and Its Implementation

Although many electronic safety-related systems require very high reliability, it is becoming harder and harder to achieve it because of delay-related failures, which are caused by decreased noise margin. This paper describes a technology named DART and its implementation. The DART repeatedly measures the maximum delay of a circuit and the amount of degradation in field, in consequence, confirms the marginality of the circuit. The system employing the DART will be informed the significant reduction of delay margin in advance of a failure and be able to repair it at an appropriate time. The DART also equips a technique to improve the test coverage using the rotating test and a technique to consider the test environment such as temperature or voltage using novel ring-oscillator-based monitors. The authors applied the proposed technology to an industrial design and confirmed its effectiveness and availability with reasonable resources.2012 IEEE International Test Conference, 5-8 November 2012, Anaheim, CA, US

Controlling Factors of Volatile Organic Compounds in Cloud Water at the Summit of Mt. Fuji in the Free Troposphere during the Summer

2010年から2018年までの7月と8月に富士山頂（標高3,776 m）で大気および雲水を採取して、27種類の人為起源揮発性有機化合物 (AVOCs) （塩素化炭化水素16種、単環芳香族炭化水素8種、二環芳香族炭化水素3種）と6種類の生物起源揮発性有機化合物を分析した。雲水中VOCs （体積加重平均VOCs濃度：2.07 nM、n=159）の約9割はAVOCsであり、主成分はトルエンであった。これは富士山頂における大気中トルエン濃度が高いことを反映していた。雲水中AVOCs濃度は空気塊が大陸南部から輸送されたときに高く、最低濃度を示した海洋由来時の約1.5倍であった。雲水中トルエン濃度は総無機イオンの低下とともに指数関数的に減少した。雲水中クロロホルム、o-キシレン、リモネン濃度は大気中濃度とヘンリー定数から求めた計算値に比べて実測値は数倍高く、ヘンリー則からの予測値以上に濃縮されていた。疎水性が高いVOCsほど雲水に高濃縮されており、自由対流圏における雲水でもHULIS （フミン様物質）のような界面活性物質がVOCsの高濃縮に関与していることが示唆された。At the summit of Mt. Fuji in July and August from 2012 to 2018, 27 kinds of anthropogenic volatile organic compounds (AVOCs) and 6 types of biogenic volatile organic compounds (BVOCs) in the air and in cloud water were determined. AVOCs occupied about 90% of the VOCs in the cloud water (volume-weighted mean VOCs concentration: 2.07 nM, n=159) and the main component was toluene, reflecting its high concentration in the ambient air. The concentration of the AVOCs in the cloud water was high when the airmass was transported from the southern continent and was about 1.5 times higher than that when it came from the ocean. The concentration of toluene in the cloud water decreased exponentially with the increase in the total ion concentration. The concentrations of some VOCs such as chloroform, o-xylene, and limonen in the cloud water were several times higher than their Henry’s law predicted values. Among the chlorinated hydrocarbons, highly hydrophobic chloroform was more concentrated than dichloromethane in the cloud water. Atmospheric surfactants such as HULIS (Humic-like Substances) could affect the enrichment of the VOCs in the cloud water even in the free troposphere