Swiss researchers develop X-ray tomography for 3-D imaging of 34-nm transistor on a chip
March 16, 2017
Source: ASM International
Researchers at the Paul Scherrer Institute in Switzerland have reportedly made detailed 3-D images of a commercially available computer chip, marking the first time a nondestructive method has visualized the paths of a chip's internal 45-nm-wide wiring and its 34-nm-high transistors clearly, without distortion or deformation.
It is a major challenge for manufacturers to determine if, in the end, the structure of their chips conforms to the specifications. Thus, these results represent an important application of an X-ray tomography method that the researchers have been developing for several years. In their experiment, they examined a small piece that they had cut out of the chip beforehand. This sample remained undamaged throughout the measurement.
The goal now is to extend the method in such a way that it can serve to examine complete chips. The researchers conducted the experiments at the Swiss Light Source (SLS) of the Paul Scherrer Institute (PSI). They report their results in the latest edition of the journal Nature.
The electrical wires in many of the electronic chips in computers and mobile phones are just 45 nm wide, the transistors 34 nm high. While it is standard practice today to produce structures this delicate, it remains a challenge to measure the exact structure of a finished chip in detail in order to check, for example, if it is built according to specifications.
Nowadays, for such examinations, manufacturers mainly use a method in which layer after layer of the chip is removed and then, after each step, the surface is examined with an electron microscope; this is known as FIB/SEM—focused ion beam/scanning electron microscope imaging.
Now researchers of the Paul Scherrer Institute PSI have used X-rays to achieve nondestructive 3-D imaging of a chip, so that the paths of the conducting lines and the positions of the individual transistors and other circuit elements became clearly visible.
"The image resolution we were able to produce is comparable to the conventional FIB/SEM examination method," explains Mirko Holler, leader of the project. "But we were able to avoid two significant disadvantages: First, the sample remained undamaged, and we have complete information about the three-dimensional structure. Second, we avoided distortions of the images that arise in FIB/SEM if the surface of the individual slice is not exactly planar.
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