Failure Analysis Applications Research Articles

Facile chemical method of etching polyimide films for failure analysis (FA) applications and its etching mechanism studies

A new strategy has been developed for discovering a novel/facile way of etching polyimide film for FA application. The aromatic polyimide synthesized from pyromellitic dianhydride and 2,2′-dimethyl-4,4′-diaminobiphenyl in the presence of an acid catalyst. This polyimide film was used to study its physical attributes and the chemical etching rate which can be evaluated in microelectronic package application as dielectric film. Chemical etching rates of polyimide film by an alkaline etching solution with the presence of different kinds of etchants were studied by film-thickness measurement and UV absorption spectroscopy of dispersible etching residue. The etching rate of polyimide film in alkaline ethylenediamine solution is highest among the etching solution studied in the present experiment. If an external bias voltage was applied during etching, the etching rate was increased. The effect of temperature, solubility of the etchant was also discussed. The presence of a radical in the process of etching reveals that the etching reaction is a type of radical chain reaction. It was found that the deprocessing technique (drenched alkaline aqueous solution of ethylenediamine and then instantaneously combined with mix acid (2:1 Nitric 90% fuming to Sulfuric mix at 40°C)) could be extended to remove polyimide in different package geometry and different thickness of film.

A generalized rough set-based information filling technique for failure analysis of thruster experimental data

Interval-valued data and incomplete data are two key problems for failure analysis of thruster experimental data and have been basically solved by the proposed methods in this paper. Firstly, information data acquired from the simulation and evaluation system formed as interval-valued information system (IIS) is classified by the interval similarity relation. Then, as an improvement of the classical rough set, a new kind of generalized information entropy called “H′-information entropy” is suggested for the measurement of uncertainty and the classification ability of IIS. There is an innovative information filling technique using the properties of H′-information entropy to replace missing data by some smaller estimation intervals. Finally, an improved method of failure analysis synthesized by the above achievements is presented to classify the thruster experimental data, complete the information, and extract the failure rules. The feasibility and advantage of this method is testified by an actual application of failure analysis, whose performance is evaluated by the quantification of E-condition entropy.

Low Temperature Fusion Wafer Bonding Quality Investigation for Failure Mode Analysis

In this paper, a brief summary of potential defect formation and failure characteristics for low temperature plasma-assisted Si wafer bonding in correlation to different influencing factors is given. In terms of a failure catalogue classification, these defects are related to incoming material quality variation, wafer bonding equipment and bonding tools issues, or to the choice of inappropriate post-bonding process parameters. To attribute experimentally detected bond defects to its specific root cause requires applying appropriate failure analysis methods, such as e.g. atomic force microscopy, scanning acoustic microscopy, transmission electron microscopy and surface analysis but also strength testing. Practical failure analysis application examples together with new and upcoming methodical developments are presented briefly that support process and technology optimization for future wafer bonded 3D integrated electronic systems.

Efficiency determination of RF linear power amplifiers by steady-state temperature monitoring using built-in sensors

This work aims at showing a new approach for determining the efficiency of linear class A RF power amplifiers by means of non-invasive, steady-state thermal monitoring. The theoretical basis of the technique is indicated and its suitability in a real case application scenario is presented. More in detail, silicon surface thermal monitoring is performed with built-in sensors and infrared measurements on an RF power amplifier. The first monitoring circuit consists of differential sensors, which can be used for contact-less on-line efficiency monitoring or to easy production testing. The obtained results are corroborated by means of Infrared measurements. Off-chip temperature sensors have applications in failure analysis or circuit debugging scenarios. As a result, we observe a good agreement between the efficiency predicted with the thermal measurements (less than 5% of error) when compared to values measured with standard electrical equipment.

Failure mechanism of overhanging slopes in sedimentary rocks with dissimilar mechanical properties

The paper discusses a slope failure which occurred in December 2009 adjacent to a road in northern Greece. Thick Miocene limestone horizons are interbedded with relatively thin weak horizons of silty to sandy clays and loams which are more easily eroded, resulting in the formation of notches. The weak horizon acts as an aquitard, inhibiting downward percolation from both rainfall and house discharges. The two main areas of failure occurred where the notches were particularly deep (hence the overhang was greatest) at a time when heavy rainfall created a hydrostatic head within the bedrock to the west of the slope face. The stability of the notched benches is controlled by the tensile strength of rock bridges in the limestone’s discontinuities. The analysis showed that the limestone’s in situ tensile strength and cohesion are on average three times lower than those obtained from laboratory tests, hence their application in the failure analysis would lead to an overestimation of the slope stability.

Backside failure analysis application of light scattering for active silicon defect detection

This paper demonstrated the interest of EMission MIcroscopy (EMMI) combined with light scattering imaging using a confocal microscope for backside active silicon defect detection. Full backside failure analyses are presented from the fault localization to the TEM observation of a stacking fault. The backside laser imaging technique highlighted contrast anomalies at exact defect locations. The crystalline defects are acting as scattering centres. The light scattering interpretation is discussed and compared with conventional backside observed signatures.

Stress intensity factor expression for butt joint with single-edge crack considering the effect of joint shape

To accurately design the joint shape and amply reflect the load-carrying capacity of butt joint with defects, the influences of joint shape parameters on stress intensity factor (SIF) of butt joint with single-edge crack are provided with finite element method (FEM) in this study. SIF expressions for two typical butt joints with single-edge crack considering the effect of joint shape based on the traditional SIF expression are given in this paper by regressing FEM results. In engineering application of failure analysis, for butt joint with single-edge crack under static load, critical stress and critical crack length can be obtained efficiently by using these expressions. Moreover, for butt joint with single-edge crack under fatigue load, its remaining life can be predicted by using the given expressions. These expressions are more accurate than the traditional ones and able to guide the joint shape design of butt joint with single-edge crack.

Extending acoustic microscopy for comprehensive failure analysis applications

In manufacturing of microelectronic components, non-destructive failure analysis methods are important for quality control. These non-destructive methods enable rapid defect localization which then guides micro-structural investigations involving destructive sample preparation. Scanning acoustic microscopy (SAM) is a powerful tool for the inspection of internal structures in optically opaque materials. Depth-specific information can be extracted and applied to create two- and three-dimensional images without the need for time consuming tomographic scan procedures. While traditional SAM imaging of the signal intensity is very valuable, it leaves most of the potential of acoustic microscopy unused. The aim of the current work was to develop comprehensive analysis algorithms to utilize the full potential of SAM and thus to extend the range of its applications. Examples representing different application fields were investigated in the current study. The examples include advanced flip-chip devices, bonded wafer pairs, solder tape connectors of a photovoltaic solar panel and high density chip-to-chip interconnects relevant for 3D integration. Progress achieved during this work can be divided into four categories: Signal Analysis and Parametric Imaging, Signal Analysis and Defect Evaluation, Image Processing and Resolution Enhancement and acoustic GHz microscopy (GHz-SAM). For the first three categories, data acquisition was performed using a commercially available scanning acoustic microscope equipped with several ultrasonic transducers covering the frequency range from 15 to 175 MHz. In the fourth category, data acquisition was performed employing a prototype of a novel acoustic GHz microscopy tool which is currently under development into a commercial system. In the first three categories, recorded acoustic data were subjected to sophisticated algorithms operating in time, frequency and spatial domains for performing signal and image analysis. Acoustic microscopy, combined with such advanced signal and image processing algorithms, proved to be a powerful tool for non-destructive inspection.

Raith - Electron Beam Lithography for Research

Electron beam lithography is one of the enabling methods in advanced nanoresearch. Electron beam lithography is a maskless lithography technique which is therefore very flexible. Electron beam lithography provides very high resolution. This is the main reason of its wide use in nanoresearch [1]. Electron beam lithography tools are in use in all engineering and basic science disciplines. Raith manufactures a variety of electron and ion beam lithography systems for research and development applications designed to meet the needs of researchers, designers, and engineers in both university and industry environment. Furthermore, Raith develops ultrahigh precision stages and navigation packages for failure analysis applications.

Two-dimensional Chemical Delineation of Junction Profile with High Spatial Resolution and Application in Failure Analysis in 65nm Technology Node

In this work, we reported a new FIB-assisted polishing technique and a new chemical junction-staining recipe for the chemical delineation of junction profile of a 65nm device. With the new polishing technique and recipe, two-dimensional junction profile was successfully delineated with a clear LDD (lightly doped drain) profile. The delineation of the LDD profile indicates the high chemical selectivity of the staining recipe. The as-developed new polishing technique and new junction-staining recipe were successfully applied to a real failure analysis case in which defects related to the inhomogeneous implantation process were successfully identified

Two-Dimensional Chemical Delineation of Junction Profile with High Spatial Resolution and Application in Failure Analysis in 65 nm Technology Node

not Available.

Functional failure analysis of a thermal–hydraulic passive system by means of Line Sampling

Assessing the failure probability of a thermal–hydraulic (T–H) passive system amounts to evaluating the uncertainties in its performance. Two different sources of uncertainties are usually considered: randomness due to inherent variability in the system behavior (aleatory uncertainty) and imprecision due to lack of knowledge and information on the system (epistemic uncertainty). In this paper, we are concerned with the epistemic uncertainties affecting the model of a T–H passive system and the numerical values of its parameters. Due to these uncertainties, the system may find itself in working conditions that do not allow it to accomplish its functions as required. The estimation of the probability of these functional failures can be done by Monte Carlo (MC) sampling of the epistemic uncertainties affecting the model and its parameters, followed by the computation of the system function response by a mechanistic T–H code. Efficient sampling methods are needed for achieving accurate estimates, with reasonable computational efforts. In this respect, the recently developed Line Sampling (LS) method is here considered for improving the MC sampling efficiency. The method, originally developed to solve high-dimensional structural reliability problems, employs lines instead of random points in order to probe the failure domain of interest. An “important direction” is determined, which points towards the failure domain of interest; the high-dimensional reliability problem is then reduced to a number of conditional one-dimensional problems which are solved along the “important direction”. This allows to significantly reduce the variance of the failure probability estimator, with respect to standard random sampling. The efficiency of the method is demonstrated by comparison to the commonly adopted Latin Hypercube Sampling (LHS) and first-order reliability method (FORM) in an application of functional failure analysis of a passive decay heat removal system in a gas-cooled fast reactor (GFR) of literature.

Cassette-based in-situ TEM sample inspection in the dual-beam FIB

A novel method is presented, combining site-specific TEM sample preparation and in-situ STEM analysis in a dual-beam microscope (FIB/SEM) fitted with a chamber mounted nano-manipulator. TEM samples are prepared using a modified in-situ, lift-out method, whereby the samples are thinned and oriented for immediate in-situ STEM analysis using the tilt, translation, and rotation capabilities of a FIB/SEM sample stage, a nano-manipulator, and a novel cassette. This cassette can provide a second tilt axis, orthogonal to the stage tilt axis, so that the STEM image contrast can be optimized to reveal the structural features of the sample (true STEM imaging in the FIB/SEM). The angles necessary for stage rotation and probe shaft rotation are calculated based on the position of the nano-manipulator relative to the stage and door and the stage tilt angle. A FIB/SEM instrument, equipped with a high resolution scanning electron column, can provide sufficiently high image resolution to enable many failure analysis and process control applications to be successfully carried out without requiring the use of a separate dedicated TEM/STEM instrument. The benefits of this novel approach are increased throughput and reduced cost per sample. Comparative analysis of different sample preparation methods is provided, and the STEM images obtained are shown.

Dynamic laser stimulation techniques for advanced failure analysis and design debug applications

Dynamic laser stimulation (DLS) techniques have been introduced over the past few years to tackle the localization of dynamic failures. This article first reviews the principles behind DLS techniques and their implementation based on monitoring functional test mapping (pass/fail) signals and monitoring other electrical variations. The integration of DLS within a dynamic optical analysis workflow in failure analysis and design debug is then presented. Finally improvements aimed at increasing the ability of DLS techniques to solve ever-growing range of subtle soft defects issues are discussed.

Micron and sub-micron level hardness testing for failure analysis

The important aspects of microhardness and nanohardness testing for failure analysis applications are reviewed. Fundamentals of hardness testing and measurement are discussed. Popular indenter geometries are addressed, with their benefits and limitations highlighted. Common applications of hardness testing to determine mechanical property data are outlined. The most common problems associated with small length scale hardness testing, such as the indentation size effect (ISE) and indentation induced cracking (IIC), are discussed. Practical solutions to these problems are presented and their overall implications discussed.

Theory of SEM Voltage Contrast and Applications to IC Failure Analysis

Abstract Voltage contrast, a phenomenon that occurs in scanning electron microscopes, produces brightness variations in SEM images that correspond to potential variations on the test sample. Through appropriate processing, voltage contrast signals can reveal an extensive amount of information about the functionality of ICs. Voltage contrast can be used, for example, to map electrical logic levels and timing waveforms from internal nodes of the chip as it operates inside the SEM chamber. This article describes the fundamentals of voltage contrast and its applications in IC failure analysis.

Direct Imaging of Device Characteristics In a Focused ion Beam System

Abstract A great deal can be learned about integrated circuits (ICs) and microelectronic structures simply by imaging them in a focused ion beam (FIB) system. FIB systems have evolved during the past decade from something of a curiosity to absolutely essential tools for microelectronics design verification and failure analysis. FIB system capabilities include localized material removal, localized deposition of conductors and insulators, and imaging. A major commercial driver for FIB systems is their usefulness in the design debugging cycle by (1) rewiring ICs quickly to test design changes and (2) making connection to deep conductors to facilitate electrical probing of complex ICs. FIB milling is also used for making precision cross sections and for TEM sample preparation of microelectronic structures for failure analysis and yield enhancement applications.

Local material removal by focused ion beam milling and etching

Focused ion beams (FIB) have drawn considerable interest as a tool for micromachining in the sub-micrometer regime with major applications in failure analysis and circuit repair. With shrinking dimensions, the demands on the precision of FIB-machining are increasing. In this paper, focused ion beam enhanced etching of silicon has been investigated using iodine as an etchant which leads to an increase in the material removal rate of silicon by a factor of up to 30 compared to sputter erosion. The influence of current density, dwell time, and loop time on the removal rate will be discussed and compared to model calculations. By secondary electron microscopy, the maximum slope of the generated structures has been determined. Finally, the application of this technique to the formation of thin lamellas for TEM inspection will be shown.

Faster turnaround time for TEM by using a multiple-sample approach

The many advantages of transmission electron microscopy (TEM) over other microscopy techniques areoften offset only by one drawback: slow turnaround time. Because of the fact that the time required to complete a multi-sample analysis is directly proportional to the number of samples submitted, TEM is often not a viable tool to analyze an entire fabrication process run or a multi wafer process development experiment. However, we have developed a technique that has allowed a single person to prepareas many as six cross-sectional TEM samples in one day thereby affording the opportunity for the investigation of an entire experimental matrix in a relatively short time.This improvement in throughput is achieved by our approach to sample preparation which combines features of the Bravman-Sinclair method with the Tripod polishing technique developed by Benedict and wide tool dimpling described by Humiston. In essence, the standard dummy dice of the Bravman techniqueare replaced by "real" device dice which have been thinned to less than 50°m using the Tripod polisher. This type of mechanical back lapping was first suggested by Marcus and Sheng. Our experiments with this type of sample preparation have been applied to both failure analysis and process development applications.

Specific site device failure analysis: A case history

Failure analysis application of analytical TEM analysis was handicapped in the past by the difficulty associated with specimen preparation of specific devices in complicated integrated circuit arrays. We have published several papers detailing methods for preparing TEM specimens with high specimen preparation spatial resolution in periods of about two to four hours. This paper offers a case history of a TEM failure analysis that combines high spatial resolution specimen preparation and the utilization of chemical junction delineation techniques.The device failure came to light in a chip tester prior to shipment. Tester electrical diagnostics identified a particular cell within a large array as defective. The fail's electrical signature further narrowed-down the potential candidates to a small number of devices within the cell. The chip was examined in transmission in an IR microscope. Anomalous IR contrast was observed in the emitter of one bipolar device in the suspect region (Fig. 1). A series of conventional light-optical photographs, with increasing magnification, were taken to define the failure location. Using the light-optical photos as a guide, the failed emitter was bracketed with laser craters. The specimen preparation polishing operation used the laser craters to achieve a plane-of-polish through the suspect emitter.