Scaling up SiC crystal growth to meet demand

Leading suppliers now offer specialised, customisable solutions for manufacturers’ unique IP and process requirements.

There is an imperative to rapidly expand the production of SiC crystals to serve the current and future generations of electric vehicles (EVs) and advanced electronic devices. The exponential rate of EV adoption is driving unprecedented demand for SiC and the necessity for essential power electronics components.

The surging demand for SiC MOSFETs in electromobility (EV/ HEV) powertrains, renewable energy, inverters, and onboard chargers, is primarily responsible for the 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.

“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% [compound annual growth rate]. Given the spike in EV sales and SiC’s compelling suitability for inverters, 70% of SiC demand is expected to come from EVs,” states the McKinsey & Company article: ‘New silicon carbide prospects emerge as the market adapts to EV expansion.’

As the demand continues to rise, manufacturers are encountering the task of 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 the required large quantities of ultra-pure SiC crystals, specialised growing systems are often grouped in sets of tens or hundreds, similar to the design and construction of ‘server farms’ that consolidate data for large organisations.

Producers of SiC growing systems must be adaptable to customise 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 that offer 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 specialised and customisable solutions to meet the industry’s unique process and intellectual property needs. These solutions enable scalable production per market demands.

"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." says Frank Ried, Project Manager, PVA Crystal Growing Systems GmbH, a subsidiary of PVA TePla Group.

PVA Crystal Growing Systems develop and construct 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.

A custom SiC crystal growing process

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

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

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 1,800–2,600°C. A SiC single crystal is subsequently formed from the gaseous components at a given seed substrate.

For manufacturers, working with an expert provider of crystal growing systems that can meet their production demands and tailor the equipment to their evolving needs is essential now and in the future.

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

To ensure profitability, it is crucial that the crystal growing systems not only demonstrate exceptional reliability but also 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 of time.

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

The fourth-generation crystal growing system developed by PVA, known as SiCma, has been meticulously designed to meet the specific requirements in the production of silicon carbide. This state-of-the-art system boasts the capability to produce monocrystal boules of SiC in diameters ranging from 4” to 8”s, subsequently used for wafer fabrication.

The PVA team incorporated significant improvements that allow for reliable mass production due to its high degree of automation and compact footprint. Additional options are available to customers, like a mobile transfer system, multiple vacuum pump options, and measuring devices, which are easily incorporated to enhance the system functionality further.

The crystal growing system is designed for efficient energy consumption to achieve optimal cost efficiency.

“The process can require temperatures up to 2,600°C and consume up to 20 kilowatts over several weeks, depending on the size of the boule, so manufacturers need to be as energy efficient as possible," says Ried. SiCma achieves this by utilising 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.

"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," says Ried, adding that, when necessary, PVA can deliver several machines per week to a manufacturer.

Market adaptation: survival of the fittest

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

According to an analysis from 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 percent 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 the utilisation of components from multiple vendors, including customised components such as process chambers with varying diameters. As a result, the system accommodates the growth of both 6” and 8” SiC boules by simply adjusting the chamber size.

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

Aluminium 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 effective heat management are necessary.

Utilising an AlN source material, specialised furnaces like PVA’s 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 dramatically surge, requiring large numbers of single crystal growing systems within tight production quarters.

Manufacturers who partner with a reputable OEM that can customise crystal growing systems and prioritise intellectual property protection will secure a competitive advantage in this rapidly expanding market.