Chiplets: Piecing Together the Next Generation of Chips (Part II)

By Erik Jan Marinissen, Eric Beyne (imec)

Testing the limits: standardization and optimization of chiplet test protocols 

Chiplets are here to stay

Chiplets are modular chips with a specific function that are separately fabricated and then interconnected to form a larger system. They have emerged as a promising approach to address challenges in scaling of integrated circuits and offer versatility, scalability, and performance advantages over traditional, monolithic System-on-Chip (SoC) designs. Chiplet technology is relatively new. Just a handful of large semiconductor companies, such as AMD and Intel, have products on the market, while foundry TSMC is currently looking into standardizing the process of developing and combining chiplets on a substrate. Nevertheless, the global chiplet market is expected to grow at an annual rate of over 42% says a new report.

Electrical testing of chiplets ensures the reliability, functionality, and interoperability of these heterogeneous architectures. This article focusses on recent advancements in chiplet testing protocols and initialization of testing standards that extend beyond competitive boundaries.

Reliability and quality criteria

The quality of a chiplet refers to its condition at the moment of manufacturing. Chiplets -just like monolithic SoCs- follow certain quality criteria per application field in the manufacturing process, covering aspects such as performance and functionality. Despite rigorous testing, some defects remain undetected and ‘escape’ to the final chiplet – the so-called ‘test escapes,’ A typical number of tolerated defects for consumer electronics such as mobile phones is 100dppm (defective parts per million). This means that for every million chiplets, 100 faulty ones are tolerated. Conversely, automotive is the most stringent application field, with customers asking for “0dppm” (which in reality translates to single-digit dppm). That is because electronics in a car are often critical for safety: if your airbag opens without a good reason due to a test escape, chances are high that the driver will cause an accident. And, even for seemingly trivial issues with the car radio, the end customer will not accept a new car if the radio does not play. Other demanding application fields are avionics and medical. 

Chiplets are tested after production to identify potential failure mechanisms during their operational lifetime, including heating, cooling down, or thermo-shock vibration testing to ensure reliability.

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