The transition from fuel-powered to hybrid (HEV) and fully electrified vehicles (EV) is aggressively happening in China and Europe under the pressure of governmental sustainability policies and incentives to meet ambitious emission standards toward the achievement of a climate-neutral continent in 2050.
Europe manufactured 25% of global electric vehicles from 2010 to 2020, compared to 44% from China and 18% from the US. Big automotive players, such as Tesla, Volkswagen, Ford, Citroen, Hyundai, and Stellantis, are steadily increasing their investment to fully support the shift toward low emission (LEV) and fully electrified vehicles (EV). The SiC device market is expected to grow at 34% CAGR during 2017-2027, 70% driven by automotive, with industrial power as the second top application. In addition to these applications, SiC is also being utilized as radio-frequency (RF) devices to support the transition to 5G and beyond with GaN on SiC technology for wireless communication, radar, and telecommunication. Besides that, the top-two SiC device manufacturers are headquartered in Europe.
This represents an unprecedented opportunity for wafer manufacturers, device makers, and related supply chains.
Due to outstanding performance in terms of achievable power and frequency, silicon carbide became a must-have material for power electronics components in batteries and inverters for hybrid (HEV) or fully electrified vehicles (EV).
Being a relatively new technology, high-volume manufacturing of SiC substrates and devices introduces several challenges that are still partially unsolved.
Firstly, the scarcity of high-quality, large-size substrates with accurate crystallographic orientation. SiC is more expensive than Si, and effective Cost-of-Ownership (CoO) management will be reached only when large substrates will be available, the main production still being at 150 mm with the first samples of 200 mm becoming available in 2022.
The second main challenge is represented by yield loss. The specifications from the automotive sector are very aggressive, especially for defects and contaminations that – if not controlled and eliminated - can trigger device reliability failure.
On top, the timeline for the achievement of SiC device high-volume manufacturing is drastically accelerating, following the growing demand of car manufacturers and with less extent, other users in energy and industrial applications.
All these factors put enormous pressure on the entire supply chain, including materials and equipment suppliers, both from product availability and quality standpoints. With this respect, SCREEN offers a comprehensive portfolio to support both SiC wafers and device manufacturers.
SCREEN response to SiC markets
Europe hosts several top players in SiC technology, both in wafer and device manufacturing.
To facilitate our European customers, we adopted a “glocal” strategy, still being a global vision but focused on localized support. For this reason, we offer our European customers a training facility and an equipment refurbishment centre close to Munich, in the heart of Europe.
From a technological standpoint, we are diversifying our product portfolio to support SiC substrate and device makers in addressing new challenges, such as handling wafers with a bow or peculiar warpage and thick or bonded wafer and thinned wafers including ultra-thin Taiko wafers. This has implied a new design of chucks, robotics, and other hardware components.
Cleaning and surface treatment
SiC wafers are usually obtained via diamond wire cutting of SiC boules, grown from high-quality SiC powder. One of our customers has patented a novel process consisting of the transfer of a thin layer of SiC from a donor wafer to an accepting substrate. The latter approach, commercialized as SmartCut®, aims to engineer substrates for specific applications by controlling the process at the atomic level scale with exceptional CoO. SCREEN is engaged in a long-term collaboration including participation in European-funded R&D projects for FD-SOI.
At the wafer manufacturing level, the main challenge brought about by SiC is the achievement of “epi-ready” large substrates, by eliminating particles and metals contaminants coming from both materials (such as CMP slurries) and processes (i.e.: wafer cutting), and the very tiny defects such as intrinsic crystallographic defects-piping, stacking faults, dislocation, and pits.
SCREEN is a worldwide leader in wet cleaning tools and technology, with outstanding particle and metal removal efficiency and etch rate uniformities based on both commodity and formulated chemistry.
We recently enriched our SiC and Compound Semiconductors (CS) dedicated portfolio with the introduction of the new bi/tri-modular, single wafer, processor SP-2100. The equipment combines three state-of-the-art cleaning functions (Softspray®, Nanospray®, and surface brush) and it can be configured with all main commodity chemistries and blends (SC-1, SC-2, DHF, BHF, H3PO4/HNO3) to cover a broad range of applications: Al etching, SiO2 etching, RCA process, post- CMP cleaning.
For batch wafer processing, the CW-2000 equipment has been designed to be extremely compact and able to handle a wide range of wafer sizes, from 50 mm to 200 mm.
Other tools in the cleaning portfolio are the single wafer tool SU-2000, able to handle thin wafers up to 200 mm, and the batch tools series WS- 620C/820C/820L for 150/200 mm wafers carrier transfer processing and 200 mm wafer carrier-less transfer processing. All these tools are highly customizable in terms of the number of baths and chemicals.
Last, but not least, it is worth mentioning that our coater/developer litho tracks have been in use for more than 5 years for SiC device manufacturers in Europe.
Yield enhancement and metrology
SiC substrates are not free yet from intrinsic crystallographic defects which might evolve in craters and voids during the next epitaxial growth. After deposition, the propagated defects can reach dimensions visible to the naked eye. Cracks and scratches are post-epi common defects as well.
Effective identification of surface defects relies on the combination of several inspection tools, ideally ranging from visual inspection to soft X-rays-based techniques. The selection of the right metrology in HVM is triggered not only by sensitivity, but also by CoO, throughput, footprint, and ease of operation.
SCREEN has developed the inspection platform ZI-3500 for both patterned and un-patterned wafers, to simplify the top-side inspection of full wafers in a high-volume environment. ZI-3500 is already in production at various customer sites and SCREEN will ship the higher productivity version by the end of this year. ZI-3500 allows the handling of any size of wafers up to 300 mm and aimed to support the inspection of wafers by easy recipe creation, automation, wafer map visualization, and several other options implemented in the new platform, such as auto defect classifications and CD/overlay measurement. A very competitive CoO is achieved with high throughput, a small tool footprint, and a very low cost compared to the competition.
One more platform of interest is a set of tools for film thickness measurement. The VM-2500/3500 series is based on Spectroscopic Reflectometry within the VIS (400-800 nm), VIS+NIR (400-1,000 nm), and UV+VIS (200-800 nm) wavelenght range. VM-2500/3000 can operate in a broad thickness range - from a few nanometres to a few tenths of microns – with a very comprehensive layers library (polysilicon, resist, polyimide, SiOx, Epi, GaN, Al2O3…) and on a large variety of substrates (Si, SiC, Sapphire, GaAs, Al, Cr, and glass) and including a trench measurement option for SiC.
Boosting new technology development
Lastly, we offer a comprehensive annealing product platform currently consisting of two equipment (LA-3100 and LT-3100) with full wafers flash lamp or localized surface selective UV laser annealing capability. Those operate from relatively low temperature to sub-melt and melt regions for different materials, with a very accurate thermal budget and penetration control. The latest tool has been designed to address SiC power applications such as post-implantation SiC defect curing, ohmic contact formation, and dopant activation, which positions SCREEN as a technology enabler for next-generation power devices.