Application of Fast Laser Deprocessing Techniques in Physical Failure Analysis on SRAM Memory of Advance Technology

Author(s):  
H.H. Yap ◽  
P.K. Tan ◽  
G.R. Low ◽  
M.K. Dawood ◽  
H. Feng ◽  
...  

Abstract With technology scaling of semiconductor devices and further growth of the integrated circuit (IC) design and function complexity, it is necessary to increase the number of transistors in IC’s chip, layer stacks, and process steps. The last few metal layers of Back End Of Line (BEOL) are usually very thick metal lines (>4μm thickness) and protected with hard Silicon Dioxide (SiO2) material that is formed from (TetraEthyl OrthoSilicate) TEOS as Inter-Metal Dielectric (IMD). In order to perform physical failure analysis (PFA) on the logic or memory, the top thick metal layers must be removed. It is time-consuming to deprocess those thick metal and IMD layers using conventional PFA workflows. In this paper, the Fast Laser Deprocessing Technique (FLDT) is proposed to remove the BEOL thick and stubborn metal layers for memory PFA. The proposed FLDT is a cost-effective and quick way to deprocess a sample for defect identification in PFA.

Author(s):  
H.H. Yap ◽  
P.K. Tan ◽  
J. Lam ◽  
T.H. Ng ◽  
G.R. Low ◽  
...  

Abstract With the scaling of semiconductor devices to nanometer range, ensuring surface uniformity over a large area while performing top down physical delayering has become a greater challenge. In this paper, the application of laser deprocessing technique (LDT) to achieve better surface uniformity as well as for fast deprocessing of sample for defect identification in nanoscale devices are discussed. The proposed laser deprocess technique is a cost-effective and quick way to deprocess sample for defect identification and Transmission Electron Microscopy (TEM) analysis.


Author(s):  
Amy Poe ◽  
Steve Brockett ◽  
Tony Rubalcava

Abstract The intent of this work is to demonstrate the importance of charged device model (CDM) ESD testing and characterization by presenting a case study of a situation in which CDM testing proved invaluable in establishing the reliability of a GaAs radio frequency integrated circuit (RFIC). The problem originated when a sample of passing devices was retested to the final production test. Nine of the 200 sampled devices failed the retest, thus placing the reliability of all of the devices in question. The subsequent failure analysis indicated that the devices failed due to a short on one of two capacitors, bringing into question the reliability of the dielectric. Previous ESD characterization of the part had shown that a certain resistor was likely to fail at thresholds well below the level at which any capacitors were damaged. This paper will discuss the failure analysis techniques which were used and the testing performed to verify the failures were actually due to ESD, and not caused by weak capacitors.


Author(s):  
Mark Kimball

Abstract This article presents a novel tool designed to allow circuit node measurements in a radio frequency (RF) integrated circuit. The discussion covers RF circuit problems; provides details on the Radio Probe design, which achieves an input impedance of 50Kohms and an overall attenuation factor of 0 dB; and describes signal to noise issues in the output signal, along with their improvement techniques. This cost-effective solution incorporates features that make it well suited to the task of differential measurement of circuit nodes within an RF IC. The Radio Probe concept offers a number of advantages compared to active probes. It is a single frequency measurement tool, so it complements, rather than replaces, active probes.


Author(s):  
Romain Desplats ◽  
Timothee Dargnies ◽  
Jean-Christophe Courrege ◽  
Philippe Perdu ◽  
Jean-Louis Noullet

Abstract Focused Ion Beam (FIB) tools are widely used for Integrated Circuit (IC) debug and repair. With the increasing density of recent semiconductor devices, FIB operations are increasingly challenged, requiring access through 4 or more metal layers to reach a metal line of interest. In some cases, accessibility from the front side, through these metal layers, is so limited that backside FIB operations appear to be the most appropriate approach. The questions to be resolved before starting frontside or backside FIB operations on a device are: 1. Is it do-able, are the metal lines accessible? 2. What is the optimal positioning (e.g. accessing a metal 2 line is much faster and easier than digging down to a metal 6 line)? (for the backside) 3. What risk, time and cost are involved in FIB operations? In this paper, we will present a new approach, which allows the FIB user or designer to calculate the optimal FIB operation for debug and IC repair. It automatically selects the fastest and easiest milling and deposition FIB operations.


Author(s):  
Wing Chiu Tam ◽  
Osei Poku ◽  
R. D. (Shawn) Blanton

Abstract Systematic defects due to design-process interactions are a dominant component of integrated circuit (IC) yield loss in nano-scaled technologies. Test structures do not adequately represent the product in terms of feature diversity and feature volume, and therefore are unable to identify all the systematic defects that affect the product. This paper describes a method that uses diagnosis to identify layout features that do not yield as expected. Specifically, clustering techniques are applied to layout snippets of diagnosis-implicated regions from (ideally) a statistically-significant number of IC failures for identifying feature commonalties. Experiments involving an industrial chip demonstrate the identification of possible systematic yield loss due to lithographic hotspots.


Author(s):  
Julie Segal ◽  
Arman Sagatelian ◽  
Bob Hodgkins ◽  
Tom Ho ◽  
Ben Chu ◽  
...  

Abstract Physical failure analysis (FA) of integrated circuit devices that fail electrical test is an important part of the yield improvement process. This article describes how the analysis of existing data from arrayed devices can be used to replace physical FA of some electrical test failures, and increase the value of physical FA results. The discussion is limited to pre-repair results. The key is to use classified bitmaps and determine which signature classification correlates to which type of in-line defect. Using this technique, physical failure mechanisms can be determined for large numbers of failures on a scale that would be unfeasible with de-processing and physical FA. If the bitmaps are classified, two-way correlation can be performed: in-line defect to bitmap failure, as well as bitmap signature to in-line defect. Results also demonstrate the value of analyzing memory devices failures, even those that can be repaired, to gain understanding of defect mechanisms.


Author(s):  
Gwee Hoon Yen ◽  
Ng Kiong Kay

Abstract Today, failure analysis involving flip chip [1] with copper pillar bump packaging technologies would be the major challenges faced by analysts. Most often, handling on the chips after destructive chemical decapsulation is extremely critical as there are several failure analysis steps to be continued such as chip level fault localization, chip micro probing for fault isolation, parallel lapping [2, 3, 4] and passive voltage contrast. Therefore, quality of sample preparation is critical. This paper discussed and demonstrated a quick, reliable and cost effective methodology to decapsulate the thin small leadless (TSLP) flip chip package with copper pillar (CuP) bump interconnect technology.


Author(s):  
P. Egger ◽  
C. Burmer

Abstract 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.


Author(s):  
Steve Ferrier ◽  
Kevin D. Martin ◽  
Donald Schulte

Abstract 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.


Author(s):  
Alan Kennen ◽  
John F. Guravage ◽  
Lauren Foster ◽  
John Kornblum

Abstract Rapidly changing technology highlights the necessity of developing new failure analysis methodologies. This paper will discuss the combination of two techniques, Design for Test (DFT) and Focused Ion Beam (FIB) analysis, as a means for successfully isolating and identifying a series of high impedance failure sites in a 0.35 μm CMOS design. Although DFT was designed for production testing, the failure mechanism discussed in this paper may not have been isolated without this technique. The device of interest is a mixed signal integrated circuit that provides a digital up-convert function and quadrature modulation. The majority of the circuit functions are digital and as such the majority of the die area is digital. For this analysis, Built In Self Test (BIST) circuitry, an evaluation board for bench testing and FIB techniques were used to successfully identify an unusual failure mechanism. Samples were subjected to Highly Accelerated Stress Test (HAST) as part of the device qualification effort. Post-HAST electrical testing at 200MHz indicated that two units were non-functional. Several different functional blocks on the chip failed electrical testing. One part of the circuitry that failed was the serial interface. The failure analysis team decided to look at the serial interface failure mode first because of the simplicity of the test. After thorough analysis the FA team discovered increasing the data setup time at the serial port input allowed the device to work properly. SEM and FIB techniques were performed which identified a high impedance connection between a metal layer and the underlying via layer. The circuit was modified using a FIB edit, after which all vectors were read back correctly, without the additional set-up time.


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