Quick tests for safety-critical chips

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In autonomous vehicles, microchips play a key role. To ensure that they do their job without problems, scientists can now check them particularly quickly and inexpensively using a new test infrastructure.

It takes hundreds of steps to turn quartz sand into a microchip containing many billions of transistors. At the same time, miniaturization is approaching the boundaries of what is technically and physically possible. Errors or fluctuations during manufacturing processes can easily occur. Before a chip is completed, it must therefore undergo a check after each process step. For example, special test structures in the area between the usable dies (chip) on a wafer (scribe lines) are used to take measurements. This saves precious chip space. Further information comes directly from the chip, the so-called in-die area. Although the measurements are taken fully automatically, the associated costs with highly integrated processor chips are almost as high as the manufacturing costs.

However, this is not the end of the testing. In certain cases, test structures in the microchips required by ISO norms or other regulations allow a detailed inspection following production. For example, each microchip in a mobile phone undergoes a check like this before the device is sold. These tests are complicated and generate a large volume of data. In many cases, they can cost up to 50 percent of the overall production costs. If the microchips are already in operation, everything become even more complex and therefore expensive.

Flexible test infrastructure with buffer

Scientists from the Hamm-Lippstadt University (HSHL) have now carried out a research project and developed a more accurate, less expensive and time-saving test infrastructure. At the same time, the “new” microchip has numerous reconfigurable test structures. A buffer as well as variable options for compressing and decompressing data provide extra flexibility. The self-tests take just milliseconds. As a result, defective components can be identified more quickly. This is very important when working with increasingly complex and small microchips. As specific examples of use, the researchers mentioned autonomous control systems such as those in autonomous vehicles. Here, microchips take on central and safety-critical tasks. Reliable system tests are therefore a basic requirement for the future of such developments.



Test infrastructure  (Image: HSHL / Kerstin Heinemann)

Testing microchips is complex and expensive. (Image: HSHL / Kerstin Heinemann).