Identifying ESD damage using an electron microscope

When microchips are faulty, it’s the job of the Dresden-based experts at SGS Institut Fresenius to find out why.

Electrostatic discharge (ESD) is one of those things we’ve all experienced in our everyday lives. You go to touch something, and suddenly a spark flies. This is caused when the difference of electrical potential between the two bodies is large enough to lead to a charge equalisation. These kinds of electrostatic discharge involve comparatively low amounts of energy, but they are sufficient to cause critical damage to certain circuit elements in microchips. Although there are protective circuits, they have limited effectiveness. This is why rigorous ESD tests are conducted on components ahead of market launch to discover potential weak points. However, ESD damage frequently occurs when end customers use the component, at which point it is returned to the supplier, who then attempts to determine the cause of the potential ESD damage. In both cases, this is where the Dresden site of SGS Institut Fresenius GmbH, which focuses on microelectronics and is a leading service provider for analysis in this field, comes in.

The ESD damage is in the detail

Mechanical engineering has primarily provided workstation solutions that ensure effective ESD protection. These include special clothing, floor surfaces, table tops and frames, for example. However, an electron microscope is required to determine fine ESD damage after the event. “Only rough damage with significant fusing would be visible under an optical microscope, but that is not generally the case, as ESD damage causes relatively little fusing. The first step is removing the entire wiring level of a damaged component in a wet-chemical process – that is to say, by etching it away with acid,” laboratory manager Thomas Freitag explains. This makes the actual semiconductor level – and thus also the silicon substrate – visible. The transistors are located on this level, along with all those components that are susceptible to ESD.

With the help of electron microscope analysis, it is possible to trace the flashover current path on these components, which is created by an electrostatic discharge. “The discharge generates flash temperatures of well over 1000 degrees, causing the silicon surface to melt,” site manager Gerald Dallmann says. This kind of flashover current path is located between two active areas (appear raised on figures 1 and 2). In such cases, ESD damage is clearly identifiable, as it is very characteristic.

Identifying ESD damage – only one part of the service portfolio

However, there are also jobs where testing equipment is used to deliberately load components. This kind of ESD test is helpful e.g. for newly developed circuits in preparation for market launch. “The following questions are relevant in tests where a charge is used to load or overload the components: Where exactly did the damage occur? Which protective circuits were effective and which weren’t?” says Dallmann. ESD simulation models are used to ensure the components are loaded realistically. The most common models include the human-body model (HBM) and the machine model (MM). While an HBM simulates the discharge from a human body into a component, the MM simulates discharge from a machine.

In addition, it is often necessary to decide whether it involves ESD or even EOS (“electrical overstress”). This isn’t always easy. Fundamentally, electrical components are always dimensioned and constructed for specific maximum currents and voltages. “When the component is overloaded, however, this causes flashovers that differ greatly from those associated with ESD. The energies involved in EOS are much larger, and can cause a component to melt right through,” Dallmann explains. EOS generally arises when the customer is using the component. However, there are also cases where it becomes hard to differentiate between ESD and EOS, so every nuance matters.

Global network of experts

SGS Institut Fresenius GmbH is a key provider of non-medical analytics. The independent laboratory was originally founded in Wiesbaden in 1848. In 2004, it became part of SGS, the world’s leading testing and certification company. This Swiss testing Group has a global workforce of over 97,000, spread across more than 2,600 sites. Every site has its own specialism. The fact that the Dresden site focuses on ESD is largely due to its long tradition of microelectronics. Two departments of what was then the Zentrum Mikroelektronik Dresden formed an independent company in 1990. They are now one of the leading industrial service providers for characterising materials, surfaces and thin layers. Alongside the actual analysis, their expertise and wide-ranging network enable Gerald Dallman and his team to provide companies with targeted support.

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2019-02-19T10:49:12+00:00February 14th, 2019|Know-how, News|
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19. Dec 2018 item Redaktion Once more the year is almost over and the holidays are fast approaching. All the more reason to look back at the blog highlights of 2018. At the same time, we’re signing off for a short Christmas break. After the over-indulgent festivities of the holiday season, the item blog kicked off the new year with an introduction to lean production methods. This is a great place to get an overview of lean terminology. Two more posts at the beginning of the year continued the lean theme. The first was about RWTH Aachen University, which had launched a practical course that teaches students lean assembly on a U-shaped cell. The second was on the CETPM and its new building, where a “Lean 4.0 lab” with integrated Karakuri solution enables an even better form of lean training. Becoming more efficient with digital engineering In the spring, our post “Digital engineering – designing online made simple” was the springboard for an issue that would come to shape 2018 for item. The item Engineeringtool, which is continuously growing, allows users to design 3D constructions using item components from the comfort of their web browser – without having to install any additional software. This means standard tasks can be completed more quickly, and even users with no previous experience find the whole design and configuration process easy. Florian Palatini, head of sales, was the subject of our interview with an expert, and this further expanded on the topic of digital engineering. Networking between design engineers and projects is at the heart of this, which means that engineers are increasingly taking on the role of a project manager. Other posts were devoted to data security in the face of digitalisation in the mechanical engineering sector and a basic explanation of what digitalisation actually is. The entire world of item Alongside these insights into the mechanical engineering of the future, we still stayed true to our roots. For example, we went back to Solingen in the 1970s and the origins of the MB Building Kit System. Shortly after, we dedicated a whole post to expounding the benefits of aluminium profiles. These benefits are particularly obvious in comparison with steel, as only three process steps are required instead of eight. Plus, aluminium is far lighter than steel, while also being very strong and exceptionally corrosion-resistant. The quality of fasteners for aluminium profiles is also of vital importance in this context. Thanks to our quality policy, we are able to provide targeted assistance to our customers in successfully meeting the challenges of specialist mechanical engineering. Stylish and functional We are always fascinated by the unusual ways our solutions are used. For example, we were particularly impressed by the world’s largest 360-degree display in the Autostadt Wolfsburg. The basic construction uses curved profiles from the MB Building Kit System. In the Sivasdescalzo sneaker store in Barcelona, our profile technology is not just to be found in the frame structure of the shelving. Used in the place of steps and to form display platforms, it also adds to the store’s stunning look. Munich-based start-up Spyra has also taken a liking to our profiles, which offer a flexibility and stability that turned out to be perfect for the prototype and a test channel for the innovative Spyra One water pistol. We hope this year’s blog posts about solutions, applications and people from the world of item have been a useful source of inspiration. We’d like to wish all our readers, customers and partners a very happy festive season and a great start to the new year! We’re taking a little break, but will be back after the holidays, with the first article for 2019 on 9 January. Previous article Digitalisation in layman’s terms Categories Latest Posts Archive Research Know-how News Industries People via E-Mail Don´t miss a new blog article!
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