Dynamic Infrared System Level Fault Isolation

The use of Dynamic Infrared (IR) Imaging is presented as a novel, valuable and non-destructive approach for the analysis and isolation of failures at a system/component level.

A Novel Approach to Front-Side Deprocessing for Thinned Die after Backside Failure Isolation

This paper describes a novel approach for safe handling of the thinned die from the front; a technique that can also be successfully applied to preserve cracked die. The discussion provides details on the characteristics and processes involved in backside reconstruction, thinned die reconstruction, and front-side deprocessing of thinned die. The finished backside reconstruction sample was cross-sectioned for examination using a diamond saw. After 6 hours of bake, no cracking of the thinned die was observed. Front-side deprocessing was then applied to the backside reconstructed sample. The sample remains intact. The technique has proven to be easily applied and highly reliable, and provides a solution for front-side deprocessing for both high pin count ball grid arrays and flip chips.

Failure Analysis of Vertical Cavity Surface Emission Laser Diodes

A failure analysis case study for oxide confined vertical cavity surface emitting laser (VCSEL) arrays will be presented. The focus of this work is on devices failing with a reduced optical output due to a rapid degradation of the laser diode. The complete analysis flow will be shown, including electrical and optical characterization as well as detailed investigations on a nanometer scale. It is known that these fails are caused by dislocations. An advanced FIB preparation method enabled cross-section and plan view TEM to successfully visualize the complete extent of a dislocation network.

Fault Localization in Contact Level by Using Conductive Atomic Force Microscopy

As integrated circuits (IC) have become more complicated with device features shrinking into the deep sub-micron range, so the challenge of defect isolation has become more difficult. Many failure analysis (FA) techniques using optical/electron beam and scanning probe microscopy (SPM) have been developed to improve the capability of defect isolation. SPM provides topographic imaging coupled with a variety of material characterization information such as thermal, magnetic, electric, capacitance, resistance and current with nano-meter scale resolution. Conductive atomic force microscopy (C-AFM) has been widely used for electrical characterization of dielectric film and gate oxide integrity (GOI). In this work, C-AFM has been successfully employed to isolate defects in the contact level and to discriminate various contact types. The current mapping of C-AFM has the potential to identify micro-leaky contacts better than voltage contrast (VC) imaging in SEM. It also provides I/V information that is helpful to diagnose the failure mechanism by comparing I/V curves of different contact types. C-AFM is able to localize faulty contacts with pico-amp current range and to characterize failure with nano-meter scale lateral resolution. C-AFM should become an important technique for IC fault localization. FA examples of this technique will be discussed in the article.

Application of Scan Based FA and Advanced Passive Voltage Contrast Technique in Defect Isolation

Scan testing and passive voltage contrast (PVC) techniques have been widely used as failure analysis fault isolation tools. Scan diagnosis can narrow a failure to a given net and passive voltage contrast can give real-time, large-scale electronic information about a sample at various stages of deprocessing. In the highly competitive and challenging environment of today, failure analysis cycle time is very important. By combining scan FA with a much higher sensitivity passive voltage contrast technique, one can quickly find defects that have traditionally posed a great challenge.

Magnetic Emission Mapping for Passive Integrated Components Characterisation

We developed a system and a method to characterize the magnetic field induced by circuit board and electronic component, especially integrated inductor, with magnetic sensors. The different magnetic sensors are presented and several applications using this method are discussed. Particularly, in several semiconductor applications (e.g. Mobile phone), active dies are integrated with passive components. To minimize magnetic disturbance, arbitrary margin distances are used. We present a system to characterize precisely the magnetic emission to insure that the margin is sufficient and to reduce the size of the printed circuit board.

Microhardness Testing on Via Fill Material for Via In Pad Technology

Via in pad PCB (Printed Circuit board) technology for passive components such as chip capacitors and resistors, provides the potential for improved signal routing density and reduced PCB area. Because of these improvements there is the potential for PCB cost reduction as well as gains in electrical performance through reduced impedance and inductance. However, not long after the implementation, double digit unit failures for solder joint electrical opens due to capacitor “tombstoning” began to occur. Failure modes included via fill material (solder mask) protrusion from the via as well as “out gassing” and related “tombstoning.” This failure analysis involved investigating a strong dependence on PCB supplier and, less obviously, manufacturing site. Other factors evaluated included via fill material, drill size, via fill thermal history and via fill amount or fill percent. The factor most implicated was incomplete cure of the via fill material. Previous thermal gravimetric analysis methods to determine level of polymerization or cure did not provide an ability to measure and demonstrate via fill cure level in small selected areas or its link to the failures. As a result, there was a metrology approach developed to establish this link and root-cause the failures in the field, which was based on microhardness techniques and noncontact via fill measuring metrologies.

VLSI Design for Functional Failure Analysis in the < 90 nm and Flip-Chip Era

In recent years, two new techniques were introduced for flip chip debug; the Laser Voltage Probing (LVP) technique and Time Resolved Light Emission Microscopy (TRLEM). Both techniques utilize the silicon’s relative transparency to wavelengths longer than the band gap. This inherent wavelength limitation, together with the shrinking dimensions of modern CMOS devices, limit the capabilities of these tools. It is known that the optical resolution limits of the LVP and TRLEM techniques are bounded by the diffraction limit which is ~1um for both tools using standard optics. This limitation was reduced with the addition of immersion lens optics. Nevertheless, even with this improvement, shrinking transistor geometry is leading to increased acquisition time, and the overlapping effect between adjacent nodes remains a critical issue. The resolution limit is an order of magnitude above the device feature densities in the &lt; 90nm era. The scaling down of transistor geometry is leading to the inevitable consequence where more than 50% of the transistors in 90nm process have widths smaller than 0.4um. The acquisition time of such nodes becomes unreasonably long. In order to examine nodes in a dense logic cuicuit, cross talk and convolution effects between neighboring signals also need to be considered. In this paper we will demonstrate the impact that these effects may have on modern design. In order to maintain the debug capability, with the currently available analytical tools for future technologies, conceptual modification of the FA process is required. This process should start on the IC design board where the VLSI designer should be familiar with FA constraints, and thus apply features that will enable enhanced FA capabilities to the circuit in hand during the electrical design or during the physical design stages. The necessity for reliable failure analysis in real-time should dictate that the designer of advanced VLSI blocks incorporates failure analysis constraints among other design rules. The purpose of this research is to supply the scientific basis for the optimal incorporation of design rules for optical probing in the &lt; 90nm gate era. Circuit designers are usually familiar with the nodes in the design which are critical for debug, and the type of measurement (logic or DC level) they require. The designer should enable the measurement of these signals by applying certain circuit and physical constraints. The implementation of these constraints may be done at the cell level, the block level or during the integration. We will discuss the solutions, which should be considered in order to mitigate tool limitations, and also to enable their use for next generation processes.

SRAM Failure Analysis Strategy

The area of embedded SRAMs in advanced logic ICs is increasing more and more. On the other hand smaller structure sizes and an increasing number of metal layers make conventional failure localization by using emission microscopy or liquid crystal inefficient. In this paper a SRAM failure analysis strategy will be presented independent on layout and technology.

Contributions of a Formal Analysis Metaprocess to Breakthrough Failure Analysis Results

Application of a formal Failure Analysis metaprocess to a stubborn yield loss problem provided a framework that ultimately facilitated a solution. Absence of results from conventional failure analysis techniques such as PEM (Photon Emission Microscopy) and liquid crystal microthermography frustrated early attempts to analyze this low-level supply leakage failure mode. Subsequently, a reorganized analysis team attacked the problem using a specific toplevel metaprocess.(1,a) Using the metaprocess, analysts generated a specific unique step-by-step analysis process in real time. Along the way, this approach encouraged the creative identification of secondary failure effects that provided repeated breakthroughs in the analysis flow. Analysis proceeded steadily toward the failure cause in spite of its character as a three-way interaction among factors in the IC design, mask generation, and wafer manufacturing processes. The metaprocess also provided the formal structure that, at the conclusion of the analysis, permitted a one-sheet summary of the failure's cause-effect relationships and the analysis flow leading to discovery of the anomaly. As with every application of this metaprocess, the resulting analysis flow simply represented an effective version of good failure analysis. The formal and flexible codification of the analysis decision-making process, however, provided several specific benefits, not least of which was the ability to proceed with high confidence that the problem could and would be solved. This paper describes the application of the metaprocess, and also the key measurements and causeeffect relationships in the analysis.