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OSIRIS Report Summary

Project ID: 662322
Funded under: H2020-EU.

Periodic Reporting for period 1 - OSIRIS (Optimal SIC substR ates for Integrated Microwave and Power CircuitS)

Reporting period: 2015-05-01 to 2016-04-30

Summary of the context and overall objectives of the project

OSIRIS project, Optimal SIC substraRte for Integrated Microwave and Power CircuitS, a Research and Innovation Action (RIA), aims at improving substantially the cost effectiveness and performance of gallium nitride (GaN) based millimetre wave components. The project is proposing to elaborate innovative SiC material using isotopic sources. This material will offer thermal conductivity improvement of 30% which is important for devices dissipating a lot of power, in particular in SiC power electronics and in microwave device using GaN high electron mobility transistors (HEMT) grown on SiC semi-insulating substrates. OSIRIS project will allow reinforcing GaN technology penetration into the market by cost effectiveness of the SiC substrates and circuit performances improvement thanks to better heat spreading close to the dissipative area.
For microwave GaN/SiC HEMT this isotopic approach could create a complete shift in the currently used substrate / GaN epi-wafer technology; it intends to grow high thermal conductivity (+30%) semi-insulating SiC on top of low cost semiconducting SiC substrates (widely used by the power electronics and LED industries). Reduced layer thickness is necessary as only the top 50 to 100µm SiC wafer is really useful as the expensive substrate itself is currently thinned to realise microstrip waveguided microwave circuits.
For power electronics this isotopic innovation will be essentially focused on thermal improvement, i.e. better electron mobility at a given power dissipation as mobility and drift mobility decrease with temperature and also better carrier transport thanks to lower scattering rates. Schottky and p-i-n diodes will be tested using this material, which however will have to be doped while microwave devices need semi-insulating materials.
The improved thermal SiC properties will be obtained by using single isotopic atoms for silicon and carbon, namely 28Si and 12C. The SiC wafer size will be targeted to 100mm (4-inches) which is today widely used on industry.
The consortium is highly complementary, covering all skills required to achieve the project objectives, from the growth of crystals materials to the assessment of devices.

• There is a strong participation of SMEs : 4 partners out of 9: Ascatron AB (SE), Intraspec Technologies (F), Isosilicon AS (NO), Norstel AB (SE)
• 3 partners from Academy: CNRS-CIMAP (F), Linköping University (SE), STUBA (SK)
• 1 industrial research lab, Leader, III-VLab (F)
• 1 industrial partner UMS (F)
• Very limited redundancy between partners;
• The Consortium is highly complementary with no competition between industrial partners.

A project website is available at

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

• OSIRIS project is following the project work plan. The project suffered 3 to 4 month delay due to difficulty faced by the University of Linköping with a new SiC reactor requiring some tunings. However a mitigation solution was successfully used and project objectives have been maintained. As the project is still at its dawn, it is difficult to prognosticate if this planning shift can be kept or reduced depending on the course of the other subsequent workpackages.
• The initial actions regarding have been focused mostly on epitaxial growth of SiC by University of Linköping (LIU) on top of SiC substrate supplied by Norstel. Another important task carried out by Isosilicon was to develop an 28Si isotopic separation technique to give rise to the necessary atom sources for isotopic SiC crystal growth.
• Isosilicon has launched two studies to investigate the two most promising methods for isotopic enrichment of silicon. Isosilicon did a thoroughly analysis of all possible solutions for isotopic selection. This comparative analysis coupled to experimental activities has given rise to a strong understanding of enrichment challenges including both technical and economical challenges.
• University of Linköping and III-V Lab GaN epitaxial growth teams have been able to grow successfully HEMT heterostructures on OSIRIS SiC substrates and SiC/”natural”SiC epitaxy. 12 wafers have been supplied to III-VLab for microwave processing.
• Active device activity has been dedicated to the design of a microwave mask-set by III-V Lab and UMS which will be used to characterise the OSIRIS semiconductor materials for GaN HEMT grown on SiC substrate. Material specifications were discussed between the growers’ teams and the processing ones. Regarding SiC devices, ASCATRON will use available in-house mask-set.
• For device characterisation the partners Intraspec Technologies, CNRS-CIMAP, III-VLab, STUBA decided to start preliminary experiments in order to get used to devices that will be studied when device processing will be completed. That activity has paved the way to check the usual bias conditions, learn how to measure and assess the devices as well as probe different characterization methods in order to evaluate the types of information they could bring. This work will be quite useful in the second part of OSIRIS project.
• Thermal simulation and assessment have started with notably a benchmarking of thermal modelling of HEMT devices that will be used by Consortium. A satisfactory agreement between thermal simulation of STUBA and III-VLab was obtained despite different approaches have been used.
• For the dissemination activity, STUBA has designed and implemented an e-learning site supporting OSIRIS project and CIMAP has developed a Website for OSIRIS project including a private area.
As a conclusion first year of OSIRIS project faced initial delays due to technical issues, but an efficient mitigation plan has been put in place which bypassed the sticking point. Out of this delay, all actions are in line with the project plan.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

• The novelty of the proposed project is to utilize an ingenious way of increasing the thermal conductivity of the substrate and hence the power efficiency of the HEMT device by removing all but one of the isotopes for Si and C, respectively. The thermal conductivity of the SiC substrate will make a significant leap by about 30% which is applicable for ALL devices. OSIRIS project will study the impact of this new SiC on GaN HEMT and SiC Schottky and p-i-n junctions.
• Another novelty of this proposal lays in the fabrication of the isotope enriched thick SI and doped epitaxial layers on on-axis host substrates which has never been done before.
• For microwave application the host substrate will later be polished away leaving only the enriched SiC layer with the processed GaN device on top. This may seem an awkward manner of doing it, but the typical practice today when manufacturing GaN HEMT devices is to polish off most of the substrate anyway leaving only 80 to 100 µm of the substrate in order to define microstrip waveguide with appropriated modes and circuit size. Considering the difficulty to produce the SI substrates, this technique of depositing a high quality SI layer on a low-cost – high volume since they are used in SiC power electronics – n-type wafer would perhaps not revolutionize but definitely induce a paradigm shift for the high frequency industry in general as money can be saved. If successfully implemented, this technique is intended to override the SI substrate business for high frequency components.
Finally, the isotope enrichment of silicon is not an established industry. Today, the only way silicon is enriched is in the form of SiF4 and in large centrifuges which is expensive and time consuming. In this proposal a more production friendly method at low cost will be developed.

• OSIRIS will contribute to develop innovations that meet the needs of European and global markets; in particular, it addressed the following needs:
• Higher efficiency energy conversion
• Safer data transmission
• Higher bit rate data transmission

It is expected that such innovations shall be delivered, within a rather short time to the following markets: energy, automotive, power supplies, industrial power drive, telecom, SATCOM, security and defence. More specifically the strengthening of competitiveness and growth of companies brought by OSIRIS is detailed per type of device targeted: GaN on ISOSiC substrates, Schottky devices and bipolar devices.
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