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HIGH-TEMPERATURE ELECTRONIC DESIGNS

Part 2: Reducing the Risk
by George Novacek

Start ı Passive Components ı The Future ı The Tradeoff ı Sources and PDF

THE FUTURE

Figure 3 is an enlightening representation of the current state of the semiconductor industry. Most of the present-day devices are based on silicon technology, which is mature, low-cost, supported by immense industrial investment, and given appropriate design techniques, has been shown to operate reliably up to at least 250ıC. Application of the oxide-isolated process (SOI) can extend the useable range to 350ıC, although this is limited to mainly small signal applications. With the worldwide effort for developing SOI for low-power and VLSI applications, the high-temperature applications will benefit too.

Figure 3ıThis is a three-axis plot of the high-temperature technologies with respect to their maturity, physical properties (potential performance), and price.

Gallium arsenide (GaAs) is the next most commonly used material, best known for its use in LEDs, MOSFETs, lasers, and so forth. The material properties, high-electron mobility, and direct bandgap being the most prominent, allow manufacturing of devices with functions not achievable in silicon. GaAs is capable of 400ıC operation, but the industry is largely focused on mainstream markets, primarily wireless communications. The high-temperature performance potential of GaAs has not truly been explored.

The wide bandgap semiconductors are still in the early stages of development. SiC is the most mature and, so far, the only one for which bulk substrates are available. Development, driven by high-power, high-temperature, high-frequency, and high-radiation applications, is close to introducing a commercially available product. SiC is expected to dominate applications over 300ıC and power applications above 200ıC for the next decade. But, there are still many technical challenges remaining, high cost notwithstanding.

The properties of GaN (Gallium Nitride) exceed those of SiC, but the technology is much less mature. The development is driven by photonic applications such as blue LEDs and lasers. Despite its excellent high-temperature characteristics, GaN is not expected to offer significant competition for SiC in the foreseeable future.

Finally, diamondıs high-temperature theoretical performance far exceeds all the other semiconductors. The technology, however, is the least developed at this time and is not expected to have any appreciable effect for another 10 years.

You must also remember that the semiconductor properties are merely a part of the problem. To make high-temperature semiconductors commercially viable, major advances in packaging, interconnection, and passive component technologies will be needed.

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