Conference Agenda

In this work this presentation will focus on a newly developed tool for

measuring carrier mobility in thick diamond crystals: Time of Flight

Electron Beam Induced Current (ToF-EBIC)1. This technique has been

initially proposed in 1970 for silicon2. Following a brief description of the

experimental method, we will illustrate how this technique can be used to

evaluate the purity and quality of diamond crystals. Various crystals will be

examined, including electronic-grade substrates from Element Six Ltd. and

heteroepitaxial diamond substrates synthesized using the CVD method

(KENZAN diamond process) provided by Orbray Co., Ltd. Carrier mobility

values will be determined using this technique and limitations of the

experimental technique will be discussed. The carrier mobility in intrinsic

diamond will be compared with other methods such as photo-excited ToF

or cyclotron resonance measurements6. For hetero-epitaxial diamond

substrates, we will demonstrate that this technique is highly effective in

assessing the suitability of different crystals for use as substrates in

electronic devices.

References

1 A. Portier, et al, Phys. Rev. Appl. 20, 024037 (2023).

2 A. A. Quaranta, et al, Review of Scientific Instruments 41, 1205 (1970)

3 K. Konishi, et al. Phys. Rev. Applied 17, L031001 (2022).

CVD Diamond is an exceptional material known for its superlative properties, such as thermal conductivity, hardness, biocompatibility, radiation resistance, optical transparency etc. These advantages motivated numerous studies towards its use for a broad range of applications, the most stimulating ones being in electronic devices or quantum properties (the latter with almost one paper published every 20 min!). But at the end of the day, are those technologies ready to enter the semiconductor industry? While academia still explores the latest novelties, the CVD diamond industry around the planet is unfortunately still essentially limited to production lines dedicated to gem fabrication! This has most likely prevented the progress CVD diamond materials deserve! It’s only recently, with the recent significant downturn of the lab grown diamond business, that we can hope an inflection point has been reached where CVD diamond is not just a gemstone… What is the next opportunity for diamond then? Is it exotic power or quantum devices? Or rather packaging applications?

Indeed, to enter electronic production lines, the most realistic opportunity for diamond is for it to be used as a heat spreader for electronic packaging applications. For this community, academic teams developed prototype devices exploring several approaches such as wafer bonding, 3D embedded vias, and buried channels, all very challenging technical approaches where diamond integration, sometimes over 3D architectures, enabled other WBG components to reach better performances. That said, is the CVD diamond technology now ready to enter the semiconductor industry? What about synthesis flexibility, but also production costs, repeatability, substrate size, and compatibility of the processes with fab plants? We really need to move forward and raise the CVD diamond manufacturing technology towards higher TRLs to enter such industrial application domains. In this context, how can machine manufacturers facilitate this progress? Drawing from typical cases where diamond-based devices are used for specific applications, examples will be used to illustrate material opportunities and challenges for diamond to meet device fabrication standards for packaging and standard device applications.

Recently, there has been a large interest in the ScAlN alloy, thanks to its various applications in high-frequency high-power, acoustoelectric, and ferroelectric devices. Nonetheless, these applications could be impaired by the presence of oxygen in the ScAlN alloy due to the high affinity of scandium with such impurity. Recent trends in ScAlN growth such as lowering growth temperature and increasing Sc content could have an effect in the incorporation of impurities. Considering this, we have studied the influence of growth temperature and Sc content in the surface oxide and oxygen content of ScAlN films grown by ammonia source molecular beam epitaxy and characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and angle resolved- X-ray photoelectron spectroscopy.

This study investigates the effects of post-deposition rapid thermal annealing (RTA) on aluminium nitride (AlN) thin films for the fabrication of microelectromechanical (MEMS) resonators. RTA was performed in a controlled nitrogen atmosphere at temperatures ranging from 200 to 1000°C on AlN thin films deposited via DC reactive sputtering with no applied heating. The effects of RTA temperature on the crystalline structure, residual strain, and piezoelectric coefficient (d₃₃) were systematically analysed. This abstract covers the preliminary results of an optimisation experiment of AlN piezoelectric properties in a CMOS-compatible process.

We present growth and fabrication of fully vertical FinFET device with a 5 μm Al0.025Ga0.975N drift layer. The stack of GaN-AlGaN layers were pseudomorfically grown on an ammonothermal-GaN bulk substrate by using MOVPE technique. This is a novel fabrication and represents a significant advancement over GaN drift layer devices.