Failure Analysis for Inter-Level Short in Nanometer Semiconductor Technologies

Author(s):  
Zhigang Song

Abstract As semiconductor technology keeps scaling down, plus new structures of transistor and new materials introduction, not only are new failure mechanisms introduced, but also old classic failure mechanisms get evolved. The obvious example of failure mechanism evolution is short defect. In the previous technologies, although short defects can happen in different layers and appear in different forms, they always happens at intra-level. As semiconductor technology advanced into nanometer regime, short defect no longer only happened in intra-level, but also more and more often happened in interlevel. Failure analysis on the inter-level short defects is much more challenging because they are usually due to interaction of two processes, such as process variation in two process steps at the same location, and often hide in the bottom of tapered and dense patterns. The conventional PFA (Physical Failure Analysis) methodology often misses discovering the defect and then the defect will be removed by subsequent polishing. This paper has demonstrated some methods to tackle the challenges with three case studies of such inter-level short defects in nanometer semiconductor technologies.

Author(s):  
G.F. Shade

Abstract Two cases are presented where photoemission microscopy (PEM) quickly reduced the analysis time by providing qualitative evidence of the suspected failure mechanisms. In both cases, the failures were delaying product shipments and the PEM technique was a "last hope" approach where other proposals were either not successful, or were not available to the analysts. In case one, package residue caused a leakage path that was located and confirmed by PEM. The second case required the use of PEM to observe uniformity of current flow within a polysilicon region. This second analysis provided absolute evidence that the current flow was nonuniform which supported the suspected failure mechanism. It is believed that this is the first reported observation of these two emission mechanisms during a failure analysis.


Author(s):  
C.Q. Chen ◽  
P.T. Ng ◽  
G.B. Ang ◽  
Francis Rivai ◽  
S.L. Ting ◽  
...  

Abstract As semiconductor technology keeps scaling down, failure analysis and device characterizations become more and more challenging. Global fault isolation without detailed circuit information comprises the majority of foundry EFA cases. Certain suspected areas can be isolated, but further narrow-down of transistor and device performance is very important with regards to process monitoring and failure analysis. A nanoprobing methodology is widely applied in advanced failure analysis, especially during device level electrical characterization. It is useful to verify device performance and to prove the problematic structure electrically. But sometimes the EFA spot coverage is too big to do nanoprobing analysis. Then further narrow-down is quite critical to identify the suspected structure before nanoprobing is employed. That means there is a gap between global fault isolation and localized device analysis. Under these kinds of situation, PVC and AFP current image are offen options to identify the suspected structure, but they still have their limitation for many soft defect or marginal fails. As in this case, PVC and AFP current image failed to identify the defect in the spot range. To overcome the shortage of PVC and AFP current image analysis, laser was innovatively applied in our current image analysis in this paper. As is known to all, proper wavelength laser can induce the photovoltaic effect in the device. The photovoltaic effect induced photo current can bring with it some information of the device. If this kind of information was properly interpreted, it can give us some clue of the device performance.


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.


Author(s):  
Cha-Ming Shen ◽  
Yen-Long Chang ◽  
Lian-Fon Wen ◽  
Tan-Chen Chuang ◽  
Shi-Chen Lin ◽  
...  

Abstract Highly-integrated radio frequency and mixed-mode devices that are manufactured in deep-submicron or more advanced CMOS processes are becoming more complex to analyze. The increased complexity presents us with many eccentric failure mechanisms that are uniquely different from traditional failure mechanisms found during failure analysis on digital logic applications. This paper presents a novel methodology to overcome the difficulties and discusses two case studies which demonstrate the application of the methodology. Through the case studies, the methodology was proven to be a successful approach. It is also proved how this methodology would work for such non-recognizable failures.


Author(s):  
Hui Peng Ng ◽  
Ghim Boon Ang ◽  
Chang Qing Chen ◽  
Alfred Quah ◽  
Angela Teo ◽  
...  

Abstract With the evolution of advanced process technology, failure analysis is becoming much more challenging and difficult particularly with an increase in more erratic defect types arising from non-visual failure mechanisms. Conventional FA techniques work well in failure analysis on defectively related issue. However, for soft defect localization such as S/D leakage or short due to design related, it may not be simple to identify it. AFP and its applications have been successfully engaged to overcome such shortcoming, In this paper, two case studies on systematic issues due to soft failures were discussed to illustrate the AFP critical role in current failure analysis field on these areas. In other words, these two case studies will demonstrate how Atomic Force Probing combined with Scanning Capacitance Microscopy were used to characterize failing transistors in non-volatile memory, identify possible failure mechanisms and enable device/ process engineers to make adjustment on process based on the electrical characterization result. [1]


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):  
E. H. Yeoh ◽  
W. M. Mak ◽  
H. C. Lock ◽  
S. K. Sim ◽  
C. C. Ooi ◽  
...  

Abstract As device interconnect layers increase and transistor critical dimensions decrease below sub-micron to cater for higher speed and higher packing density, various new and subtle failure mechanisms have emerged and are becoming increasingly prevalent. Silicon dislocation is a new failure mechanism that falls in this category and was for the first time, uncovered in submicron multilayered CMOS devices. This mechanism was responsible for a systematic yield problem; identified as the 'centre GFA wafer' functional failure problem. In this paper, several breakthrough failure analysis techniques used to narrow down and identify this new mechanism will be presented. Root cause determination and potential solution to this problem will also be discussed.


Author(s):  
A.C.T. Quah ◽  
G.B. Ang ◽  
D. Nagalingam ◽  
C.Q. Chen ◽  
H.P. Ng ◽  
...  

Abstract This paper describes the observation of photoemissions from saturated transistors along a connecting path with open defect in the logic array. By exploiting this characteristic phenomenon to distinguish open related issues, we described with 2 case studies using Photon Emission Microscopy, CAD navigation and layout tracing to identify the ‘open’ failure path. Further layout and EBAC analysis are then employed to effectively localize the failure site.


Author(s):  
Xuedong Chen ◽  
Zhibin Ai ◽  
Tiecheng Yang ◽  
Zhichao Fan ◽  
Weihe Guan

There are several hundred of failure cases of pressure vessels and piping in China every year. The causes for part of accidents have been clearly analyzed, and preventive measures have been taken making the similar accidents substantially reduced, but the causes for quite a few failure accidents are still not found effectively, the similar accidents is still taking place. Through study, the authors find that the major reason for deviation of failure analysis lies in that equipments are mostly operating in complex medium environment, and mutual competition may exist among multiple failure mechanisms. Sometimes changes of some influential factors may cause the dominant failure mechanism change, even leads to totally different analysis conclusions. Combining with the analysis and verification of several failure cases of pressure vessels and piping in petrochemical enterprises, the judgment method for the dominant failure mechanism under multiple failure mechanisms is discussed in this paper, which may be helpful to provide some effective means for failure prevention of pressure equipment under complex environment.


Author(s):  
Ghim Boon Ang ◽  
Changqing Chen ◽  
Hui Peng Ng ◽  
Alfred Quah ◽  
Angela Teo ◽  
...  

Abstract This paper places a strong emphasis on the importance of applying Systematic Problem Solving approach and use of appropriate FA methods and tools to understand the “real” failure root cause. A case of wafer center cluster RAM fail due to systematic missing Cu was studied. It was through a strong “inquisitive” mindset coupled with deep dive problem solving that lead to uncover the actual root cause of large Cu voids. The missing Cu was due to large Cu void induced by galvanic effects from the faster removal rate during Cu CMP and subsequently resulted in missing Cu. This highlights that the FA analyst’s mission is not simply to find defects but also play a catalyst role in root cause/failure mechanism understanding by providing supporting FA evidence (electrically/ physically) to Fab.


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