Unlocking Chip Secrets: A Guide to Backside Decapsulation for Failure Analysis
"Discover how mechanical decapsulation can revolutionize failure analysis in non-exposed die pad packages, ensuring accuracy and efficiency."
In today's fast-paced microelectronics industry, the demand for increasingly complex chips is ever-growing. With this complexity, however, comes a higher susceptibility to failures caused by external electrical stress or manufacturing defects. Identifying the root cause of these failures quickly and accurately is crucial for maintaining product quality and reliability.
One essential technique used in failure analysis is exposing the die backside, often achieved through chemical preparation. While effective, this method has significant drawbacks, especially when dealing with small, non-exposed die pad packages. The risk of over-etching copper leads with harsh chemicals like 65% Acid Nitric Fuming can hinder further electrical measurements, rendering the process ineffective.
This article explores an innovative solution: mechanical decapsulation. This alternative method offers a more controlled and precise approach to backside sample preparation, ensuring the copper leads remain intact and enabling accurate electrical measurements. Learn how this technique can revolutionize your failure analysis process and improve the overall effectiveness of your results.
Why Backside Decapsulation Matters
Conventional backside sample preparation or decapsulation for module devices is prone to damage and time consuming, and chemical and other mechanical backside preparation techniques have very small success rates when it comes to preserving the electrical behaviour of module devices. To improve results, a high-precision selective backside decapsulation process has been divided into two sub-processes: laser ablation and precision milling. Laser ablation is described as the technique of utilizing a regulated laser beam to extract material from a solid substance. In practical terms, the preparation step itself is often the deciding factor between a usable failure analysis and a damaged sample.
Limits of Conventional Front-Side Wet Etching
In a case study of failed MMIC ASIC devices sealed in SOP packages, benzocyclobutene (BCB) used as a dielectric material is etched during wet-etch front-side decapsulation, and this vulnerability is what motivated the proposed backside approach. As an alternative, a new ultra-short pulse laser ablation based backside sample preparation method has been developed that is contact-less, non-thermal, precise, repetitive, and adapted to each type of material present in IC packages. The known weaknesses of conventional chemical methods are a key reason analysts increasingly turn to backside and laser-based techniques.
A History the Sources Do Not Cover
None of the source material gathered for this subsection addresses the history of backside decapsulation; the listed references instead concern U.S. foreign-relations milestones, gaming promotion codes, the history of a symbol, and an operating-system interface tip. Because a documented timeline for backside decapsulation is therefore unavailable from these sources, this article does not assert specific historical dates or founding figures. Readers seeking the technique's origins should turn to peer-reviewed failure-analysis literature rather than the general-history references assembled here.
The Problem with Chemical Etching
Traditional chemical etching has long been a standard practice for exposing the die backside. It's generally known for its speed and ability to deliver a clean surface. However, its application is not without challenges, especially when dealing with delicate packages. Small, non-exposed die pad packages, where the die is fully covered with mold compound, are particularly vulnerable.
- Copper Lead Damage: The acid can aggressively attack the copper leads, causing them to erode or even break.
- Measurement Hindrance: Damaged leads compromise the ability to perform accurate electrical measurements, a critical step in failure analysis.
- Limited Application: Chemical etching becomes unsuitable for package designs with large die pad areas and small lead areas due to this over-etching risk.
Recent Chip Flaw Discovery via Decapsulation
Researchers from Ledger's Donjon team, the security division of Trezor's direct competitor, found a flaw in the TROPIC01 secure element chip during an audit of the Trezor Safe 7 device. The disclosure illustrates how chip-level investigation, including package opening, feeds into security research and product hardening. As reported, the finding emerged from a formal audit rather than public field reports.
When Decapsulation Falls Short
For wafer-level samples, direct observation is possible, but decapsulation must be implemented for packaged devices, and the procedures and tools of backside decapsulation are introduced specifically to enable failure localization in such chips. Failure and yield analysis is an increasingly difficult and complex process, and engineers are today required to locate defects on complex integrated circuits, with decapsulation, backside sample preparation, and mechanical delidding techniques among the standard approaches. Commercial service providers likewise position decapsulation, backside sample preparation, and Scanning Acoustic Microscopy (SAM) as core offerings for failure analysis, reflecting both the demand for and the difficulty of getting the step right.
Two Meanings, One Discipline of Precision
In networking, decapsulation is the removal of protocol headers as data moves up the OSI layers, the mirror of encapsulation, in which each layer bundles header information along with the actual data. In semiconductor failure analysis, decapsulation instead means opening a device package to reach the die, and here newer approaches compete with older chemical ones. A whitepaper describes highly selective Microwave-Induced Plasma (MIP) technology as an alternative that removes only the material it needs during decapsulation, keeping samples pristine and supporting analysis that goes right the first time.
Embracing the Future of Failure Analysis
In conclusion, mechanical decapsulation presents a compelling alternative to chemical etching for backside sample preparation, particularly in non-exposed die pad package designs. By mitigating the risk of over-etching and preserving the integrity of copper leads, this technique ensures more reliable electrical measurements and enhances the overall effectiveness of failure analysis. As the microelectronics industry continues to advance, embracing innovative methods like mechanical decapsulation will be crucial for maintaining product quality, reducing failure rates, and driving continuous improvement.
Practitioner View: Complexity Is the Norm
Practitioner-oriented commentary characterizes failure and yield analysis as an increasingly difficult and complex process, with engineers required to locate defects on complex integrated circuits. Within this workflow, decapsulation, backside sample preparation, and mechanical delidding techniques are treated as standard, though demanding, steps. The recurring emphasis is that backside preparation is one of the analyst's core tools for meeting that requirement.
Automation, Miniaturization, and Selective Methods
Emerging trends such as automation and the miniaturization of electronic components are reported to further fuel the laser decapsulation market, highlighting the importance of laser decapsulation in maintaining quality and enhancing production efficiencies. On the technical side, an improved backside decapsulation technique has been introduced to address the challenge of devices with multiple paddles and downbonds, documented on an isolator device to serve as a reference guide for current and future multiple-paddled products. Together, these developments point toward more selective and more automated sample preparation rather than brute-force chemical opening.
Specialized Equipment, Deep Expertise, and Tricky Packages
Trezor's response to the TROPIC01 disclosure lists backside decapsulation, or opening the device package, as requiring specialized, expensive lab equipment and deep expertise to find and execute. Likewise, standard chemical decapsulation methods are not applicable to stacked-die packages, since multi-chip CSPs containing two or more stacked dice present a unique challenge to the failure analyst. These constraints mean the capability sits outside most ordinary laboratories and depends on niche tooling and skill.
The Analyst Behind the Tool
Behind every successful decapsulation is a human analyst whose judgment, training, and patience determine whether a rare and expensive device survives preparation. In practice, results depend as much on reading the package and the device's history as on the machine settings, although specific evidence for this claim falls outside the scope of the sources available for this article. The broader point is that chip-level failure analysis remains a craft-dependent field in which experience directly shapes outcomes.