Integrated circuits in silicon carbide for high-temperature applications
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Introduction With the right semiconductor material, operation of electronics up to 600°C is possible.1 Currently, military applications can operate up to 125°C while high-temperature silicon-oninsulator (SOI) usage is limited to 225°C due to the use of silicon as a semiconductor. Silicon carbide (SiC) has been pursued for high-voltage diodes and transistors with low ON-resistance, or as substrate material for GaN high frequency and photonic devices, most notably white light-emitting diodes (LEDs). The idea of making integrated circuits (ICs) with SiC is certainly not new.2 In fact, the capability of SiC for high-temperature operation was acknowledged ∼20 years ago. However, the challenges involved were perhaps greater than expected. Since larger diameter (100–150 mm) SiC substrates with defect densities low enough for reasonable yields are now available, ICs using SiC can certainly be realized3 (Figure 1). Using SiC, operation of both junction field-effect transistors (JFETs) and bipolar circuits have been demonstrated up to 600°C, and metal oxide semiconductor field-effect transistor (MOSFET) circuits have been able to operate up to 500°C (Table I). Circuit complexities are currently far behind silicon complementary metal oxide semiconductors (CMOS); silicon has had more than 40 years to reach maturity. Even so, SiC circuits with several hundred devices, both digital and analog, have been fabricated. The performance of SiC circuits at room temperature is far worse than silicon counterparts, but reliability is anticipated to improve in the 200°C to 300°C
range as compared to silicon.1 The temperature regime of interest is >300°C, where silicon technology cannot operate at all, for instance space missions to the inner planets.1 What is also clear is that the present demonstrations of 600°C operation is not limited by SiC itself, as devices using SiC could possibly work up to 1000°C.2 Other materials involved, mainly for metallization and passivation, are now the limiting factors in terms of operational temperature.3 Packaging is a separate issue with huge challenges ahead, and reliability testing is only in its infancy with just a few tests conducted for 1000 hours. This article reviews different SiC technologies based on MOSFET, JFET, metal semiconductor field-effect transistor (MESFET), and bipolar transistors. The capabilities demonstrated so far, as well as the main features and limitations, are outlined. At present, it is unclear which circuit technology will prevail, but what is certain is that SiC ICs will soon become commercially available for high-temperature applications.
Applications There are two obvious application areas for high-temperature ICs: sensing and power circuits/energy conversion.1 For sensing, there are many gas and pressure sensors available that can work as high as 600°C.3 If the signal is too weak and there is no possibility of cooling the electronic parts, a SiC amplifier could be considered. Sensor interfaces could also include analog-to-digital conversion, memory for storage, and data tran
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