Wafer-level defect-based testing using enhanced voltage stress and statistical test data evaluation

Treadmill exercise training in chronic obstructive pulmonary disease.

To achieve high quality of silicon ICs, system-level test (SLT) can be performed after regular final test. This is important for chips manufactured in advanced technologies, as systematic failures are getting harder to detect by conventional structural tests. However, due to long test time and extra human efforts, the cost for SLT is high. A possible way to replace SLT without quality loss is to identify SLT failure suspects with stress tests. In this work, we apply 60,000 structural stress test patterns to the CPU blocks of a real SOC product, using 20 stressed voltage-frequency corners. We try to identify the correlation between the stress test data and SLT-pass/fail results of the CPU blocks. By the proposed differential feature-based methodology, 32 outliers are identified, which are assumed to be CPU-fail chips. Because of the lack of exact CPU-fail chip IDs for verification, the identified chip IDs are compared with the IDs identified from previous works, which use the same data but different machine-learning features and method for the same purpose. After comparison, 30 out of a total of 33 CPU-fail suspects matched. Although this does not immediately imply that the SLT can be replaced by the structural stress tests, it shows more evidence that test data mining can be further explored for test time reduction and/or quality improvement.

Stress echocardiography has become an established tool for the diagnosis of coronary artery disease. However, in the current era of attention to cost effectiveness, the ability of a non-invasive test to predict outcomes, and therefore assist in clinical decision making, is paramount. As a reflection of the relative youth of this technique, there are fewer data using stress echocardiography to assess prognosis than there are using nuclear imaging. However, using both exercise and pharmacological stress echocardiography, the presence of ischaemia is strongly predictive of the recurrence of a subsequent cardiac event. Moreover, during pharmacological stress testing, the ischaemic threshold may be used to further stratify the risk of a positive test. More studies are needed in large populations to establish the prognostic role of stress echocardiography, as in independent predictor of outcome, incremental to clinical and stress testing data.

This paper presents a comprehensive study of the impact of Hot Carrier Injection (HCI) on differential LC Voltage Controlled Oscillator (VCO) reliability tests. Although Negative Bias Temperature Instability (NBTI) has been recognized as major cause for reliability degradation of advanced circuits, HCI-induced degradation may become significant due to the accelerated aging of reliability tests leading to incorrect circuit lifetime prediction. To distinguish HCI effects, different stress voltages and frequencies are applied in Constant Voltage Stress (CVS) and Ramp Voltage Stress (RVS) tests. It is verified that the stress voltage and frequency dependence of time and voltage exponents in the reliability tests are due to the effect of HCI. Based on the observed results, a methodology is proposed to define proper stress conditions for accelerated circuit reliability tests for better lifetime prediction.

In semiconductor manufacturing, the early life of the produced devices can be simulated by means of burn-in. In this way, early failures are screened out before delivery. To reduce the efforts associated with burn-in, the failure probability p in the early life of the devices is evaluated using a burn-in study. Classically, this is done by computing the exact Clopper–Pearson upper bound for p. In this chapter, we provide an overview on a series of new statistical models, which are capable of considering further available information (e.g., differently reliable chip areas) within the Clopper–Pearson estimator for p. These models help semiconductor manufacturers to more efficiently evaluate the early life failure probabilities of their products and therefore reduce the efforts associated with burn-in studies of new technologies.

Wafer level accelerated testing is a key tool to perform fast reliability assessment of new technologies. This paper presents an innovative methodology developed to perform accurate life-time extrapolation of 3-dimensional (3D) high density capacitors through constant electric field stress (CES) test. This methodology is first based on dielectric thickness extraction from planar capacitor measurements. CES tests are then performed on 3D capacitors, adjusting the voltage stress with respect to the local dielectric thickness previously extracted. The efficiency of the methodology is demonstrated through constant voltage stress (CVS) and CES test results comparison.

The author describes how a thermal stress test profile was derived by experiment for more effective screening of IBM Personal System 2 planar cards. Profile components are optimized from Model 50 experimental data and reassembled into an empirically engineered power-temperature profile used in stress testing electronic cards. The resultant profile is shown to be more effective in accelerating early life failures and has become the standard framework for all PS/2 stress profiles used in IBM Greenock's SMT (surface mount technology) card stress screening. Thermal shock and voltage biasing have been introduced into Greenock's stress test for the first time. >

In semiconductor manufacturing, early life failures have to be screened out before delivery. This is achieved by means of burn-in. With the aim to prove a target reliability level and release burn-in testing of the whole population, a burn-in study is performed, in which a large number of items is investigated for early life failures. However, from a statistical point of view, there is substantial potential for improvement with respect to the modeling of early life failure probabilities by considering further available information in addition to the performed burn-in studies. In this paper, we provide ideas on how advanced statistics can be applied to efficiently reduce the efforts of burn-in studies. These ideas involve scaling the failure probability with respect to the sizes of the different products, as well as taking advantage of synergies between different chip technologies within the estimation of the chips' failure probability level.

Separating HBT wearout from defects during early life operation

To investigate reasons for the wide variation in formal studies of sensitivity and specificity indexes for the diagnostic efficacy of the graded exercise test for angiographically defined coronary disease, data were collected on 205 consecutive exercise tests at two hospital-based exercise laboratories. For calculations of sensitivity and specificity, stress test data are usually analyzed with many exclusions for ineligibility, with equivocal results omitted, and only in patients undergoing angiography. Consequently, only 3% of patients who received the tests in this survey would have been included in a typical formal study of diagnostic efficacy. In the same way that the visible tip of an iceberg misrepresents its extent and depth, the patients assembled in studies of diagnostic tests may be a highly selected group that misrepresents the intended population.

The key methods used to convert ramped voltage test (RVT) data to long term reliability measurement data are reviewed. During the last years the discussion to replace time consuming constant voltage stress (CVS) tests with ramp testing was pushed forward, mainly due to time constraints during qualification of high-k and also low-k material as well as through results obtained for ultrathin oxides [1]. The aim of this work is to contribute to the discussion with focus on thicker oxides used for automotive applications. While a future fWLR standard currently under discussion should also clearly state applicable oxide thickness ranges, advantages and limitations of various approaches, the principle assumptions and formulas are compared and applied to different data sets with gate oxide thicknesses of 9, 10, 17 and 50 nm, respectively. The results are then analyzed, discussed and compared to work based on material with much thinner/thicker oxides.

The typical electrical degradation on the complementary metal oxide semiconductor (CMOS) performance is due to defect in gate oxide layer. During integrated circuit (IC) infant mortality phase, stress tests introduced at wafer sort and final test in order to assured only good IC being deliver to end customer. Stress tests such as burn-in, gate stress, and quiescent current (IDDQ) test, demonstrated their competency to screen out this type of early failure. Nevertheless, the latent defect is a time dependent failure, which, affect the CMOS reliability after certain time, temperatures and application stress. Consequently, revise failure analysis technique has to be introduced in effective approach to compensate the problem in the current technology due to metal interconnection layers and dense for front side failure analysis (FA). The motivation of this work is to present the fault localization on the elevated IDD current of the faulty logic cells during the transition by photo localization technique and clarify gate oxide defect through circuit simulation. We have confirmed that the IDD scan test and photo localization technique were effective to localize faulty IC in silicon active area through front side.

We have investigated bipolar resistive switching of Cu/CuTCNQ/Al cross-junctions in both vacuum and different gas environments. While the generally observed S-shaped I-V hysteresis was reproduced in ambient air, it was reversibly suppressed in well-degassed samples in vacuum and in dry N2. The OFF-switching currents in ambient air peaked when approximately +2.6 V was applied to the Al electrode at low voltage sweep rates. OFF-switching at constant bias was accelerated in humid and oxygen-rich atmospheres. For unbiased samples stored in air, ON-state (RON) and OFF-state (ROFF) resistances increased with time, and RON surpassed the initial ROFF after approximately one week. Retention times were enhanced for samples stored in vacuum and those with a larger cross-junction area. We suggest that resistive switching occurs in a hydrated native alumina layer at the CuTCNQ/Al interface that grows in thickness during exposure to ambient humidity: ON-switching by electrochemical metallization of free Al and/or Cu ions and OFF-switching by anodic oxidation of the Al electrode and previously grown metal filaments.

Using 28nm test chips, we derive signatures for early-life failures (ELF) in both high-K/metal-gate transistors and ultra low-K inter-metal dielectrics. We also demonstrate that the derived ELF signatures can be successfully detected using a clock control technique. Our results can be utilized to overcome scaled-CMOS reliability challenges in several ways: 1. Low-cost ELF detection during on-line operation of robust systems without requiring expensive redundancy-based error detection techniques; 2. Effective ELF screening during production test while reducing stress time and/or stress levels associated with stress tests such as burn-in.

AB0224 Simulation for choice of bdmards and tsdmards in order to success for three-year survival in rheumatoid arthritis treatment