Scaling up SiC crystal growth to meet escalating demand

Del Williams explains that due to the complexity of growing quality SiC crystals, manufacturers need help obtaining sufficient systems to meet global production targets.

There is an imperative to rapidly expand SiC crystal production to serve current and future generations of EVs and advanced electronic devices. Surging demand for SiC MOSFETs in electromobility powertrains, renewable energy, inverters and onboard chargers, is primarily responsible for increasing market growth.

SiC MOSFETs offer notable advantages such as high switching frequency, thermal resistance and large breakdown voltage for high power switching, resulting in enhanced efficiency, extended vehicle range and reduced total system cost for powertrains. These benefits are particularly significant at higher voltages required by battery electric vehicles (BEVs), which are expected to dominate the electromobility sector by 2030.

A McKinsey & Company article stated ‘The SiC device market, valued at around $2 billion today, is projected to reach $11 billion to $14 billion in 2030, growing at an estimated 26 per cent [compound annual growth rate]. Given the spike in EV sales and SiC’s compelling suitability for inverters, 70 per cent of SiC demand is expected to come from EVs. New silicon carbide prospects emerge as the market adapts to EV expansion’.

As demand rises, manufacturers are tasked with rapidly expanding SiC crystal production to unprecedented levels. SiC production is time-consuming. Growing a single crystal ingot, also known as a boule, can take a few weeks to produce. To produce required quantities of ultra-pure SiC crystals, specialized growing systems are often grouped in sets of tens or hundreds.

Producers of SiC growing systems must be adaptable to customize and protect the unique system design elements required to meet each customer’s individual intellectual property (IP) requirements since specific crystal growing techniques are closely guarded secrets. Furthermore, it is crucial to have highly dependable and easily maintainable crystal growing systems offering the necessary flexibility to accommodate future market changes in wafer size or composition.

Manufacturers may need help acquiring enough crystal growing systems within the timeframes required. Fortunately, leading providers of crystal-growing systems now offer specialized and customizable solutions to meet the industry’s unique process and intellectual property needs. These solutions enable scalable production per market demands.

Project manager at PVA Crystal Growing Systems, Frank Ried, said: “The growth of crystals is primarily influenced by the manufacturer’s intellectual property and the methodologies employed in seed mounting and process control. Therefore, a versatile platform for crystal growth is essential for manufacturers to refine and validate their processes, enabling seamless scalability for mass production. This necessitates collaboration with a dependable supplier capable of rapidly producing high volumes of these machines, on demand.”

PVA Crystal Growing Systems develops and constructs machinery for several industrial methods of producing ultra-pure monocrystals, including Physical Vapor Transport, Cz (Czochralski), FZ (Float Zone) and VGF (Vertical Gradient Freeze). The systems grow silicon carbide, silicon, germanium, calcium fluoride and compound semiconductors.

To achieve optimal SiC crystal growth, EV/HEV and electronics manufacturers, plus semiconductor companies, dedicate substantial resources to research and development. This research encompasses development of seed crystals, selection of growth conditions, and other parameters impacting crystal properties. Given the significance, these specifics and other nuances and optimizations are usually regarded as proprietary information safeguarded by companies to retain competitive advantage.

Ried continued: “Custom PVT systems are available that ensure protection and exclusivity of their intellectual property. These tools are customized to meet manufacturers’ specific requirements, necessitating the utilization of premium engineering capabilities.”

According to Ried, the widely accepted technique for monocrystalline silicon carbide growth involves sublimation growth with a seed crystal, which is commonly referred to as Physical Vapor Transport (PVT). In this process, SiC source material, usually SiC powder, is transferred to the gaseous phase by sublimation at temperatures from 1,800 to 2,600°C. A SiC single crystal is subsequently formed from the gaseous components at a given seed substrate.

As volume requirements increase, installing additional equipment to meet demand is the only viable option. Selecting systems designed with a compact footprint is advisable to minimize overall operating space. Ensuring easy access for streamlined maintenance is also crucial.

To ensure profitability, it is crucial that crystal growing systems demonstrate exceptional reliability and operate with remarkable energy efficiency. These requirements are necessary as the process requires a furnace capable of reaching temperatures exceeding 2,000°C for extended periods.

Furthermore, crystal growing systems should be adaptable to accommodate industry shifts or changes, such as the transition from 6 to 8in wafers or the manufacturing of aluminum nitride (AIN) boules for electronics.

The fourth-generation crystal growing system developed by PVA, known as SiCma, has been designed to meet specific requirements in silicon carbide production. The system has the capability to produce monocrystal boules of SiC in diameters ranging from four to eight inches.

The PVA team incorporated improvements allowing reliable mass production thanks to automation and compact footprint. Options include a mobile transfer system, multiple vacuum pump options and measuring devices.

Regarding energy consumption, Ried said: “The process can require temperatures up to 2,600°C and consume up to 20kW over several weeks, depending on the size of the boule, so manufacturers need to be as energy efficient as possible.”

SiCma achieves this using inductive heating in the kilohertz range using an induction coil designed for minimal energy consumption.

To effectively enter the SiC market and achieve desired production volumes, manufacturers frequently need timely delivery of sufficient equipment to scale up their capacity rapidly.

Ried added: “Manufacturers need SiC furnaces assembled and shipped fast when they scale for production. Once they validate their process on a machine, they may need a hundred units quickly. PVA can deliver several machines per week to a manufacturer.”

Manufacturers also require a versatile platform that can adapt to an ever-changing market’s evolving needs. Upcoming demand for larger wafers, consequently requiring larger boules, presents challenges for manufacturers. They may encounter difficulties requiring investment in another system model requiring additional production space to accommodate the larger size boules.

According to McKinsey & Company, ‘A transition from the production and use of six-inch wafers to eight-inch wafers is anticipated, with material uptake beginning around 2024 or 2025 and 50 per cent market penetration reached by 2030. Once technological challenges are overcome, eight-inch wafers offer manufacturers gross margin benefits from reduced edge losses, a higher level of automation and the ability to leverage depreciated assets from silicon manufacturing.”

Implementing a modular crystal growing system fosters heightened flexibility in response to evolving market demands. For instance, SiCma enables utilization of components from multiple vendors, including customized components such as process chambers with varying diameters. As a result, the system accommodates growth of both six-inch and eight-inch SiC boules by simply adjusting the chamber size.

Recently, there has also been a notable uptick in market demand for aluminum nitride (AlN) wafers. This non-oxide ceramic material, comprised of aluminum and nitrogen, is witnessing substantial growth in electronic devices and EVs.

Aluminum nitride boasts exceptional thermal conductivity, enabling efficient heat dissipation in power modules and electronic components. Additionally, AlN functions as an electrical insulator, making it an invaluable material in electronic applications where electrical insulation and heat management are necessary.

Utilizing an AlN source material, specialized furnaces facilitate the growth of monocrystalline AlN boules at temperatures surpassing 2,000°C.

As the transition to EVs, renewable energy and electrification progresses, the need for SiC and AlN will surge, requiring large numbers of single crystal growing systems within tight production quarters. Manufacturers who partner with a reputable OEM that can customize crystal growing systems and prioritize intellectual property protection will secure a competitive advantage in this rapidly expanding market.