Fraunhofer Institute for Production Technology IPTResearch project "GREEN EPITAXY"
New generation of semiconductors for consumer goods and power electronics
Wide-bandgap (WBG) semiconductors are key technologies for energy-efficient consumer goods and high-performance electronics, that are important in various industries such as automotive, energy, industrial automation, telecommunications and defense. WBG semiconductors can operate at higher voltages and temperatures and are more efficient than silicon components which are commonly used. In addition, the use of WBG semiconductors can reduce CO₂ emissions and operating costs.
WBG semiconductors are usually produced in processes such as metal-organic chemical vapor deposition. Among other things, ammonia is used in this process, which produces toxic gases during the manufacturing process and requires extremely high process temperatures of more than 1000 °C. In addition to the environmental impact, the high energy and gas consumption, combined with limited throughput, lead to high manufacturing costs.
Low-temperature epitaxy: 90% less energy consumption, 100% less toxic gases
In the “GREEN EPITAXY” research project, Fraunhofer IPT and its project partners are developing an innovative process chain for the production of WBG semiconductors. A core element is low-temperature epitaxy (LTE): the process temperature is reduced from over 1000 °C to 300 °C by using an intelligent plasma. The use of process gas and energy can be reduced by around 90% compared to conventional processes, without compromising crystal quality. Toxic gases can even be dispensed completely.
A new generation of semiconductors
The aim of the project is to create the scientific basis for establishing low-temperature epitaxy as a standard process for the production of wide-bandgap semiconductors. The Fraunhofer IPT is contributing its expertise in the fields of laser and automation technology and glass forming to the success of the project across the entire process chain. The Fraunhofer IPT's contributions range from the pre-processing of wafers using laser structuring and the automation of processes to downstream process steps such as encapsulation.
Surface structures for improved crystal layer growth
What influence does the surface topography of the substrate have on the coating process? A research team at the Fraunhofer IPT is investigating this question by introducing micro- and nanostructures into the surface of the substrate using ultrashort pulse laser ablation. The targeted modifications of the surface structure mean that the surfaces subsequently exhibit certain wetting or anti-reflective properties, for example.
In addition to functionalization, laser-based modification of semiconductor materials on a micro- and nanoscale offers a variety of other possibilities: for example, the technology can also be used to control growth conditions during epitaxy. This will also be tested as part of the project.
Integration of a laser structuring unit into in-line epitaxy
The research team is developing a concept for integrating a structuring cell into the in-line epitaxy. The challenge, in addition to introducing high-precision manufactured structures in the sub-micrometer range (~100-250 nm), is to transfer the results from the laboratory setup into a system solution for mass production of the wafer substrates.
Automatized production chain and reduced production time
In a further work package, the Fraunhofer IPT is investigating the possibilities for optimizing and automating the new production line. A core element of this research work is to fully automate the production chain. Another focus is on significantly reducing the production cycle time.
Innovative gripper technology and fully automated processes for handling and transporting wafers
The design of the transfer system, i.e. the referencing of the carriers in the various process chambers and, above all, the wafer handling technology, present particular challenges within the process chain. The aim of optimizing wafer handling is to transport the wafers to a desired position and align them precisely in the shortest possible time and without damage. The Fraunhofer IPT's concept envisages that this will take place in a cleanroom environment and in a vacuum in order to keep the number of particles on the wafers as low as possible.
Increased efficiency through glass forming at wafer level
Another team at the Fraunhofer IPT is working on developing new approaches in the field of glass forming for microLED production. The team is focusing on a combination of replicative glass forming at wafer level and direct bonding of the semiconductors with the glass wafers. This new approach can reduce costs, improve quality and shorten production processes.
Currently, so-called single multi-cavity technology is mostly used. This involves forming individual or only a few glass optics at a time, which is time-consuming and resource intensive. Wafer-level technology allows complete glass wafers to be formed in a single step. This significantly increases production speed and reduces costs. This method can be used not only for microLEDs, but also for other optical applications in areas such as sensor technology, telecommunications or medical technology.
Direct bonding of semiconductors with glass wafers
Instead of using complex encapsulation methods, the Fraunhofer IPT's concept involves bonding the microLED semiconductors directly to a glass wafer. This effectively protects the LEDs from external influences such as moisture and dust. This approach improves the optical performance and thermal stability of the LEDs.
Roadmap for implementing low-temperature epitaxy
The project results will be processed into a roadmap that offers interested industries a comprehensive overview and serves as a roadmap for possible technology implementation. The roadmap will be published and is also intended to support public sector actors in further planning.
Funding
The project “GREEN EPITAXY” is funded by the German Federal Ministry for Economic Affairs and Energy (BMWE) as part of the 7th Energy Research Program of the German Federal Government.
Funding reference: 03EN4085A
Project management
Forschungszentrum Jülich GmbH
Project duration
6/2024 – 5/2027
What is low-temperature epitaxy (LTE)?
Low-temperature epitaxy (LTE) is a process for the cost-effective and environmentally friendly production of high-quality semiconductors. LTE combines physical and chemical vapor deposition with plasma support. In this process, wafer-thin crystal layers are created on a carrier material (substrate). Despite a process temperature of only 300°C (temperatures of over 600°C are common in other processes), monocrystalline semiconductor layers are created. The energy for crystal growth is supplied via an intelligent plasma. The materials are usually supplied in a gaseous or liquid state and are deposited as a solid crystal layer on the substrate. The NTE completely dispenses with toxic gases. A significantly better deposition efficiency reduces the necessary energy and gas input by over 90% compared to other processes. Just as the gas and energy input can be reduced by more than 90%, so can the epitaxy costs.
What are wide-bandgap (WGB) semiconductors?
Wide-bandgap (WBG) semiconductors such as gallium nitride (GaN) or aluminum scandium nitride are highly efficient transistors and key elements for (almost) lossless power components in server architectures or in microLEDs for displays. WGB semiconductors lose significantly less energy in the form of heat than conventional semiconductors, which makes them highly attractive for applications such as chargers, solar systems and electric vehicles. The widespread use of efficient compound semiconductors instead of the silicon components commonly used today could save over 13 million tons of CO2 emissions per year from as early as 2025 and over 35 million tons of CO2 emissions per year from 2050.