Conductive-AFM for Scan Logic Failure Analysis at Advanced Technology Nodes

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

Abstract The increase in complexity of process, structure, and design not only increases the amount of failure analysis (FA) work significantly, but also leads to more complicated failure modes. To meet the need of high success rate and fast throughput FA operation at the leading-edge nodes, novel FA techniques have to be explored and incorporated into the routine FA flow. One of the novel techniques incorporated into the presented scan logic FA flow is the conductive-atomic force microscopy (CAFM) technique. This paper demonstrates CAFM technique as a powerful and efficient solution for scan logic failure analysis at advanced technology nodes. Several failure modes in scan logic FA are used as examples to illustrate how CAFM provides excellent solutions to some of the very challenging FA problems. The gate to active short in nFET devices, resistive contact, and open defect on gate contact are some modes used.

Author(s):  
Chuan Zhang ◽  
Esther P.Y. Chen

Abstract A variety of parametric test structures were designed with the purpose of characterizing parameters tied to failure modes for specific structures, and the electrical test of the parametric test structures are typically conducted earlier inline, which could be months ahead of the functional test. Due to the unique advantages, conductive-atomic force microscopy (CAFM) was introduced to parametric test structure failure analysis during advanced technology development, and has been proven to be a powerful solution to many challenging failure analysis (FA) problems. This paper uses several case studies to illustrate how CAFM can be used to successfully localize defects in challenging parametric test structures that would otherwise be invisible with conventional FA techniques.


2018 ◽  
Author(s):  
Chuan Zhang ◽  
Jochonia Nxumalo ◽  
Esther P.Y. Chen

Abstract Voltage contrast (VC) mode inline E-beam inspection (EBI) at post contact layer provides electrical readout of critical yield signals at an early stage, which could be months before a wafer reaches functional test. Similar to the passive voltage contrast (PVC) technique that is widely used in failure analysis labs, inline VC scanning is based on scanning electron microscopy, where a low keV electron beam scans across the wafer. Conductive atomic force microscopy (CAFM) was successfully implemented as a characterization method for inline VC defects. In this paper, three challenging VC defect analysis case studies are considered: bright voltage contrast (BVC) gate to active short, BVC Junction leakage, and Dark Voltage Contrast gate contact open. Defects exhibiting a hard electrical short, junctional leakage, and open gate contact are used to illustrate how CAFM provides a powerful and comprehensive solution for in-depth characterization of the inline VC defects.


Author(s):  
Hung-Sung Lin ◽  
Wen-Tung Chang ◽  
Chia-Hsing Chao ◽  
Jesse Wang ◽  
Chang-Tan Lin ◽  
...  

Abstract Single column failure [1], one of the complex failure modes in SRAM is possibly induced by multiform defect types at diverse locations. Especially, soft single column failure is of great complexity. As physical failure analysis (PFA) is expensive and time-consuming, thorough electrical failure analysis (EFA) is needed to precisely localize the failing area to greater precision before PFA. The methodology involves testing for failure mode validation, understanding the circuit and using EFA tools such as IR-OBIRCH (InfraRed-Optical Beam Induced Resistance CHange) and MCT (MerCad Telluride, HgCdTe) for analysis. However, the electrical failure signature for soft single column failure is usually marginal, so additional techniques are needed to obtain accurate isolation and electrical characterization instead of blindly looking around. Thus in this discussion, we will also present the use of internal probing techniques like C-AFM [2] (Conductive Atomic Force Microscopy) and a nanoprobing technique [3] for characterizing electrical properties and understanding the root cause.


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):  
N. Dayanand ◽  
A.C.T. Quah ◽  
C.Q. Chen ◽  
S.P. Neo ◽  
G.B. Ang ◽  
...  

Abstract This paper describes the effectiveness of using light induced Current Imaging – Atomic Force Microscopy (CIAFP) to localize defects that are not easily detected through conventional CI-AFP. Defect localization enhancement for both memory and logic failures has been demonstrated. For advanced technology nodes memory failures, current imaging from photovoltaic effects enhanced the detection of bridging between similar types of junctions. Light induced effects also helped to improve the distinction between gated and nongated diode, as a result enhanced localization of gate to source/drain short.


Author(s):  
C. H. Wang ◽  
S.W. Lai ◽  
C.Y. Wu ◽  
B.T. Chen ◽  
J.Y. Chiou ◽  
...  

Abstract A failure incurred in the front-end is typically a bottleneck to production due the need for physical failure analysis (PFA). Often the challenge is to perform timely localization of the front-end defect, or finding the exact physical defect for process improvement. Many process parameters affect the device behaviour and cause the front-end defect. Simply, the failures are of two types: high-resistance and leakage. A leakage mode defect is the most difficult to inspect. Although conductive atomic force microscopy and six probes nano-probing are popular tools for front-end failure inspection, some specific defects still need more effort. The electrical phenomenon and analysis of a crystalline defect will be demonstrated in this paper. The details will be discussed below.


Author(s):  
Tom X. Tong ◽  
A. N. Erickson

Abstract Many of the standard techniques of Failure Analysis (FA) are breaking down or becoming less useful as feature sizes drop below 100nm. The tenth micron milestone appears to be a fundamental limitation to many common techniques. Use of Current Image-Atomic Force Microscopy (CI-AFM) combined with Atomic Force Probing (AFP) brings about a combination of technologies, which allow for extension of FA below the nano-scale.


Author(s):  
Kun Lin ◽  
Hang Zhang ◽  
Shey-shi Lu

Abstract Conductive Atomic Force Microscopy (C-AFM) is a useful tool for both electrical failure analysis (EFA) and physical failure analysis (PFA). In this paper, the root cause of a physical failure in an analysis image was verified from the evidence of two-dimensional AFM profile depth measurement. The other analysis technique, which is electrical parameter extraction by contacting I-V spectroscopy measurement, was also utilized to locate the possible defects. As a result, the failure mechanism was illustrated with an AFM topography image, which showed the silicon surface profile after removal of cobalt salicide (self-alignment silicide) by dilute HF. The vertical junction leakage path was identified with a C-AFM image.


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