Failure Analysis of Functional Failures in a Designed for FA SRAM

Author(s):  
Gil Garteiz

Abstract Designing devices for failure analisys (FA) is becoming increasingly critical as structure geometries and killer defects rapidly decrease in size. Naturally, devices that are designed for FA are much easier to analyze and have a higher FA success rate than those that are not. Several analyses of functional failures in a 0.18um CMOS SRAM are presented in this paper to demonstrate “Design For FA” usefulness and application. Physical analysis methodology is also discussed.

Author(s):  
Randal Mulder ◽  
Sam Subramanian ◽  
Ed Widener ◽  
Tony Chrastecky

Abstract Single bit failures are the dominant failure mode for SRAM 6T bit cell memory devices. The analysis of failing single bits is aided by the fact that the mechanism is localized to the failing 6T bit cell. After electrically analyzing numerous failing bits, it was observed that failing bit cells were consistently producing specific electrical signatures (current-voltage curves). To help identify subtle bit cell failure mechanisms, this paper discusses an MCSpice program which was needed to simulate a 6T SRAM bit cell and the electrical analysis. It presents four case studies that show how MCSpice modeling of defective 6T SRAM bit cells was successfully used to identify subtle defect types (opens or shorts) and locations within the failing cell. The use of an MCSpice simulation and the appropriate physical analysis of defective bit cells resulted in a >90% success rate for finding failure mechanisms on yield and process certification programs.


Author(s):  
Randal Mulder

Abstract This paper provides failure analysis engineers a simple method for constructing probe pads on failing 0.12um SRAM bit cells using the FEI 820 Focused Ion Beam (FIB) tool. This method allows for the easy location of the failing bit cell, results in good electrical isolation, and only takes a minimal amount of FIB time (2 hours for 6 pads). The method is effective for all technologies 0.12um or greater with a high success rate once the analyst is proficient in its use. Once probe pads have been constructed, it is then relatively easy for an analyst to perform electrical analysis to identify the defect type and location causing the bit cell failure before the physical analysis is performed.


Author(s):  
Z. G. Song ◽  
S. B. Ippolito ◽  
P. J. McGinnis ◽  
A. Shore ◽  
B. Paulucci ◽  
...  

Abstract It is generally accepted that the fault isolation of Vdd short and leakage can be globally addressed by liquid crystal analysis (LCA), photoemission analysis and/or laser stimulating techniques such as OBIRCH or TIVA. However, the hot spot detected by these techniques may be a secondary effect, rather than the exact physical defect location. Further electrical probing with knowledge of the circuit schematic and layout may still be required to pinpoint the exact physical defect location, so that a suitable physical analysis methodology can be chosen to identify the root cause of the failure. This paper has described a thorough analysis process for Vdd leakage failure by a combination of various failure analysis techniques and finally the root cause of the Vdd leakage was identified.


Author(s):  
Bhanu Sood ◽  
Lucas Severn ◽  
Michael Osterman ◽  
Michael Pecht ◽  
Anton Bougaev ◽  
...  

Abstract A review of the prevalent degradation mechanisms in Lithium ion batteries is presented. Degradation and eventual failure in lithium-ion batteries can occur for a variety of dfferent reasons. Degradation in storage occurs primarily due to the self-discharge mechanisms, and is accelerated during storage at elevated temperatures. The degradation and failure during use conditions is generally accelerated due to the transient power requirements, the high frequency of charge/discharge cycles and differences between the state-of-charge and the depth of discharge influence the degradation and failure process. A step-by-step methodology for conducting a failure analysis of Lithion batteries is presented. The failure analysis methodology is illustrated using a decision-tree approach, which enables the user to evaluate and select the most appropriate techniques based on the observed battery characteristics. The techniques start with non-destructive and non-intrusive steps and shift to those that are more destructive and analytical in nature as information about the battery state is gained through a set of measurements and experimental techniques.


Author(s):  
Tsung-Te Li ◽  
Chao-Chi Wu ◽  
Jung-Hsiang Chuang ◽  
Jon C. Lee

Abstract This article describes the electrical and physical analysis of gate leakage in nanometer transistors using conducting atomic force microscopy (C-AFM), nano-probing, transmission electron microscopy (TEM), and chemical decoration on simulated overstressed devices. A failure analysis case study involving a soft single bit failure is detailed. Following the nano-probing analysis, TEM cross sectioning of this failing device was performed. A voltage bias was applied to exaggerate the gate leakage site. Following this deliberate voltage overstress, a solution of boiling 10%wt KOH was used to etch decorate the gate leakage site followed by SEM inspection. Different transistor leakage behaviors can be identified with nano-probing measurements and then compared with simulation data for increased confidence in the failure analysis result. Nano-probing can be used to apply voltage stress on a transistor or a leakage path to worsen the weak point and then observe the leakage site easier.


Author(s):  
Chuan Zhang ◽  
Yinzhe Ma ◽  
Gregory Dabney ◽  
Oh Chong Khiam ◽  
Esther P.Y. Chen

Abstract Soft failures are among the most challenging yield detractors. They typically show test parameter sensitive characteristics, which would pass under certain test conditions but fail under other conditions. Conductive-atomic force microscopy (CAFM) emerged as an ideal solution for soft failure analysis that can balance the time and thoroughness. By inserting CAFM into the soft failure analysis flow, success rate of such type of analysis can be significantly enhanced. In this paper, a logic chain soft failure and a SRAM local bitline soft failure are used as examples to illustrate how this failure analysis methodology provides a powerful and efficient solution for soft failure analysis.


Author(s):  
Keith Harber ◽  
Steve Brockett

Abstract This paper outlines the failure analysis of a Radio Frequency only (RF-only) failure on a complex Multimode Multiband Power Amplifier (MMPA) module, where slightly lower gain was observed in one mode of operation. 2 port S-parameter information was collected and utilized to help localize the circuitry causing the issue. A slight DC electrical difference was observed, and simulation was utilized to confirm that difference was causing the observed S-parameters. Physical analysis uncovered a very visible cause for the RF-only failure.


Author(s):  
Rommel Estores ◽  
Pascal Vercruysse ◽  
Karl Villareal ◽  
Eric Barbian ◽  
Ralph Sanchez ◽  
...  

Abstract The failure analysis community working on highly integrated mixed signal circuitry is entering an era where simultaneously System-On-Chip technologies, denser metallization schemes, on-chip dissipation techniques and intelligent packages are being introduced. These innovations bring a great deal of defect accessibility challenges to the failure analyst. To contend in this era while aiming for higher efficiency and effectiveness, the failure analysis environment must undergo a disruptive evolution. The success or failure of an analysis will be determined by the careful selection of tools, data and techniques in the applied analysis flow. A comprehensive approach is required where hardware, software, data analysis, traditional FA techniques and expertise are complementary combined [1]. This document demonstrates this through the incorporation of advanced scan diagnosis methods in the overall analysis flow for digital functionality failures and supporting the enhanced failure analysis methodology. For the testing and diagnosis of the presented cases, compact but powerful scan test FA Lab hardware with its diagnosis software was used [2]. It can therefore easily be combined with the traditional FA techniques to provide stimulus for dynamic fault localizations [3]. The system combines scan chain information, failure data and layout information into one viewing environment which provides real analysis power for the failure analyst. Comprehensive data analysis is performed to identify failing cells/nets, provide a better overview of the failure and the interactions to isolate the fault further to a smaller area, or to analyze subtle behavior patterns to find and rationalize possible faults that are otherwise not detected. Three sample cases will be discussed in this document to demonstrate specific strengths and advantages of this enhanced FA methodology.


Author(s):  
Chris Schuermyer ◽  
Brady Benware ◽  
Graham Rhodes ◽  
Davide Appello ◽  
Vincenzo Tancorre ◽  
...  

Abstract This work presents the first application of a diagnosis driven approach for identifying systematic chain fail defects in order to reduce the time spent in failure analysis. The zonal analysis methodology that is applied separates devices into systematic and random populations of chain fails in order to prevent submitting random defects for failure analysis. Two silicon case studies are presented to validate the production worthiness of diagnosis driven yield analysis for chain fails. The defects uncovered in these case studies are very subtle and would be difficult to identify with any other methodology.


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