Infineon and SK Siltron Sign SiC Wafer Supply Agreement

Infineon and SK Siltron Forge Long-Term Supply Agreement – A "Self-Sufficient Supply Chain" Emerges Amidst the Wafer Scramble

In 2025, Infineon entered into a multi-year SiC wafer supply agreement with SK Siltron. While the financial details remain undisclosed, Infineon's move to secure wafer procurement through a single, long-term contract symbolizes a structural shift in the SiC supply chain. It is evident that the competition for power semiconductor prowess now hinges on who can secure wafer supply.

SiC (silicon carbide) wafers are notoriously difficult to manufacture. Unlike silicon, crystal growth requires high temperatures and prolonged periods, and the challenges of defect management increase with larger wafer diameters. The industry is undergoing a transition from the current mainstream 6-inch (150mm) to 8-inch (200mm) wafers, but manufacturers capable of stably supplying high-quality, large-diameter wafers remain limited. SK Siltron of South Korea is one of these scarce suppliers.

Understanding SK Siltron

SK Siltron, a subsidiary of the SK Group focused on semiconductor materials, is a major player in the global silicon wafer market. Its significant entry into SiC wafers began in 2019 with the acquisition of DuPont's Compound Semiconductor business, followed by aggressive capacity expansions.

Crucially, SK Siltron is a supplier committed to not only increasing volume but also enhancing quality. Key quality metrics for SiC wafers include micropipe defect density (MPD) and basal plane dislocation density (BPD). The ability to reduce these defects while scaling up wafer diameter is a benchmark of a wafer manufacturer's technological prowess. SK Siltron is among the manufacturers leading the transition to 8-inch wafers. Infineon's choice to partner with SK Siltron likely stems from an assessment of this technological potential.

Why a Long-Term Contract? The Unsuitability of "Spot Procurement"

The SiC wafer supply chain differs structurally from that of silicon wafers. Silicon wafers are abundantly supplied and can be procured competitively from multiple suppliers. However, only a few companies globally can supply high-quality SiC wafers. Amidst surging demand, the risk of not securing necessary quantities in the spot market is escalating.

Infineon's decision to commit to a long-term contract is driven by demand visibility. As SiC adoption in EV inverters materializes into concrete projects, device manufacturers are beginning to receive forecasts of wafer requirements for the next two to three years from their customers. Without securing wafers based on these forecasts, device manufacturers face the risk of insufficient supply when they commence mass production. Infineon's move is a strategic preemption to mitigate this risk through a long-term contract.

The high current density of SiC devices is a characteristic of their design, which translates to stringent demands on the wafer for low defect density and uniformity. Without high-quality wafers, even the most advanced device designs cannot achieve high production yields. Wafer procurement and design development are inherently inseparable.

How Infineon's Move Differs from Competitors

Infineon is not alone in pursuing vertical integration or long-term wafer procurement for SiC. STMicroelectronics has entered into a long-term supply agreement with Wolfspeed and is also investing in in-house SiC wafer production. Rohm maintains its wafer supply through its group company, SiCrystal. Mitsubishi Electric is strengthening its joint development partnership with Coherent for 8-inch SiC substrates, aiming to secure next-generation wafers.

Infineon's choice of SK Siltron presents a slightly different strategic approach compared to other players. Wolfspeed and Cree (Wolfspeed's parent company) have a supply chain primarily centered in North America, while SK Siltron is an Asian-based supplier. From a geopolitical risk diversification perspective, Infineon, a European company, has opted to partner with a South Korean supplier. This decision likely incorporates considerations beyond simple cost comparisons, including the specific regional procurement risks they are willing to undertake.

This comparison reveals two distinct approaches: the "in-house production route" and the "external long-term contract route." By contracting with SK Siltron, Infineon has chosen to rely on a single strategic partner while continuing external procurement. This structure, however, carries the risk of the supplier's capacity not expanding as planned.

Impact on Technology Selection and Procurement Decisions – Before "Where to Buy" Changes

The long-term contracting of wafer procurement will ultimately impact the stability of device shipments. Even for SiC MOSFETs with the same ratings and packages, manufacturers with secured wafer supply may experience significantly shorter lead times in one to two years compared to those facing wafer shortages.

When considering Infineon's SiC MOSFETs during the design phase, it is worthwhile to confirm whether the timing of the recent SK Siltron agreement aligns with your planned mass production schedule. Similarly, if you are evaluating devices from ST or Rohm, each company's wafer procurement status should serve as a factor in your device selection decision.

This chart displays the maximum voltage ratings publicly announced by each company. While onsemi covers up to 1700V, Microchip's 700V/1200V products list a typical short-circuit withstand time (SCWT) of 3μs in their datasheets. The breadth of voltage ratings also relates to strategic procurement questions regarding the ability to cover multiple applications, such as industrial and high-voltage automotive systems, with a single supplier.

The short-circuit withstand time (SCWT) metric indicates how long a SiC MOSFET can withstand a short-circuit condition. It functions as a grace period before protection circuits activate, directly influencing gate driver design. Taking Microchip's typical 3μs value as an example, this specifies the design margin for how long the DESAT (desaturation) protection circuit can operate before detecting the condition and turning off the gate. Improved wafer quality could potentially contribute to enhancements in such withstand capabilities, but this can only be realized in conjunction with improvements in device structure.

Key Takeaways – What This News Implies

The contract between Infineon and SK Siltron underscores the reality that "SiC competition is not solely determined by device design." Wafer procurement at the upstream level, expansion of manufacturing capacity, and the establishment of long-term partnerships are now shaping market share two to three years down the line.

The battle for SiC wafers, while appearing to be a matter between material manufacturers on the surface, actually impacts all layers of device adoption, procurement, and design verification. Infineon's recent move can be interpreted as one answer to the question of "who will secure the competitive infrastructure for the SiC era first." What could alter this landscape next is the speed of mass production ramp-up for 8-inch wafers and the evolution of crystal growth technology that influences it.