Power for Megatrends

Numerous benefits, one challenge

One  major challenge with silicon carbide and gallium nitride is the cost-effective production of both materials. The frequency of defects in the crystals produced is about 100 times higher than with silicon, making the construction of robust semiconductor layers much more complicated. This makes the production of wafers – circular discs about half a millimetre thick made from single or multi-crystalline blanks that serve as substrates (base plates) for electronic components – more complex and demanding.

Manufacturing precision is key

The secret of power electronics lies in the manufacturing process, metal organic chemical vapour deposition (MOCVD), in the further development of which we, as the technology leader, have been significantly involved for more than 30 years. In this process, the components of the metal-organic compounds for GaN or chlorinated silicon compounds for SiC are vaporised and, together with other high-purity gases, introduced in extremely fine doses into the reaction chambers of our systems, which are heated to high temperatures with precision.

In order to meet the high demands of its customers in industry and research with regard to precision and repeatability of deposition, AIXTRON has continuously developed the flow system of its reference plants. This allows the gaseous starting materials to be introduced precisely into the centre of the chamber and flow very evenly over the hot wafers, on which the epitaxial deposition then takes place. The gaseous compounds split up so that only the desired atoms are deposited on the surfaces of the wafers. To achieve optimum uniformity of this deposition, the wafers are moved around the gas inlet through the reactor on rotating planetary tracks.

In addition, the precisely uniform flow of the gas mixture in the process chamber guarantees the sharpest transitions between the individual layers of the compound semiconductors, thus optimally controlling the deposition rates for nanometre-thin semiconductor layers of the highest quality. The result: atomically thin layers as the starting material for highly efficient power electronics.

Small defects, even in just one layer of this layer package, which often comprises several hundred individual layers or even several tens of micrometres, can therefore have a major impact on the performance of the component manufactured from it. The goal of our engineers is to optimise the plant technology to such an extent that the defects in the substrate are not carried over into the layer stack.

This is because ‘the performance of the electronic components manufactured from it depends on this first production step, as the quality of the semiconductor layer structures is decisive for the performance of the subsequent chips,’ explains Dr. Frank Wischmeyer.  

New paths to the future

To maintain this lead, we work closely with our partners in science and industry. For example, AIXTRON is cooperating closely with Fraunhofer IISB in Erlangen on the further development and optimisation of production processes for larger and therefore more economical silicon carbide wafers, and is working with partners on European research projects to develop the next generation of energy-saving chips based on gallium nitride. The aim here is to further miniaturise the chips to the highest quality at competitive costs.

"In the past, SiC and GaN technology was developed in customer-specific projects. In order to meet the ever-growing customer requirements for these process technologies, we are investing in targeted customer-oriented developments in our application laboratories. To this end, we operate an extensive fleet of systems," says Dr Frank Wischmeyer, summarising AIXTRON's approach.

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Digitalisation drives the development of plant technology

The result of these collaborations is the continuous development of production facilities for power components to make compound semiconductors increasingly competitive with established silicon-based materials. In recent years, AIXTRON has developed equipment types specifically for the manufacture of power electronics from gallium nitride and silicon carbide. The G10 product family represents the current platform for high-volume production at our customers' sites.

The G10-SiC is used for material production on 150 and 200 mm SiC at leading component and SiC epitaxy houses. "During the production of SiC epitaxy structures, data such as the temperature of the wafer surface is recorded during the process for improved process control. Digitalisation creates new development opportunities for plant technology. In addition, we are setting a benchmark for true automation capabilities for SiC in order to further close the gap to manufacturing processes in the silicon industry," says Dr Frank Wischmeyer. This enables us to meet the industry's demand for cost-effective, scalable processes.

Power electronics moves into everyday life

Efficient power electronics made of gallium nitride are already helping to prevent servers in data centres from overheating, for example, thereby reducing the need for complex cooling systems and their associated costs. But state-of-the-art power electronics are also proving their worth in everyday life. They increase the range of electric vehicles by around 20% and significantly reduce charging times. In electric cars such as the Tesla Model 3, most of the power electronics for the drive train are already made from silicon carbide, and Volkswagen plans to launch around 70 new electric vehicle models in the coming years – with power modules based on silicon carbide.
At the same time, power electronics are making key components smaller and lighter, thereby reducing the cost of batteries, for example, which are a core component of electric mobility.
Numerous smaller devices are also benefiting from this technical progress and are becoming lightweight and mobile: smartphones can already be charged wirelessly, and laptop chargers will be the size of a credit card in the future.