Renesas and Wolfspeed Sign 10-Year SiC Wafer Supply Agreement

What the Number 10 Represents

Renesas Electronics and Wolfspeed have entered into a long-term supply agreement for SiC wafers spanning a decade. While the financial details remain undisclosed, the sheer length of "10 years" is at the core of this news. Such a long-term procurement contract in the semiconductor industry is unusual and signifies that the SiC wafer market has moved beyond mere component sourcing to the realm of strategic partnerships.

Demand for SiC power semiconductors continues to expand rapidly, driven by three pillars: EVs, industrial equipment, and renewable energy. However, wafer supply capacity is a constraint on this growth. SiC crystal growth is technically more challenging than conventional silicon, and suppliers capable of stably supplying high-quality wafers in large volumes are limited globally. Wolfspeed is one of the top suppliers, and the agreement with Renesas signifies securing this supply.

Why Shift to Long-Term Contracts Now?

The procurement structure for SiC wafers has changed significantly in the past few years. During the period of rapid EV demand growth in 2021-2022, competition for wafers became a real issue, leading to device manufacturers failing to secure supply and consequently pushing back their product roadmaps. Learning from this, major players are beginning to shift their strategy from "spot procurement" to "long-term contracts."

For Renesas, the power semiconductor business is positioned as a strategic growth area in recent years. Having strengthened its analog and mixed-signal capabilities through acquisitions like Intersil, IDT, and Dialog, this move can be interpreted as an effort to solidify its upstream SiC position as its next step. Ultimately, device competitiveness depends heavily on "which wafers can be secured, when, and in what quantity," and long-term contracts are a precursor to this competition.

Another factor worth considering is Wolfspeed's situation. The company is making significant investments in its Mohawk Valley factory in North Carolina (supporting 8-inch wafers), and the recovery of this capital expenditure necessitates the backing of long-term demand. A 10-year contract with a major player like Renesas serves as a "justification" for Wolfspeed's production expansion. It is natural to view this as an agreement where the interests of both the buyer and seller align.

How This Differs from "Similar Movements"

The structure of long-term SiC wafer contracts is not unique to Renesas. Companies like STMicroelectronics, Infineon, and Rohm are showing similar movements, and it is becoming a solidified trend across the industry. However, there are differences in the contract details and strategic positioning of each company.

STMicroelectronics, in addition to its long-term contract with Wolfspeed, is pursuing in-house production of SiC wafers (through the acquisition of SiCrystal), aiming for vertical integration on both procurement and manufacturing fronts. Rohm, while securing procurement from SiCBudd (now SiCrystal), possesses its own crystal growth technology. Renesas, on the other hand, currently prioritizes external procurement.

Renesas's choice of external procurement is likely based on a decision to concentrate resources on "strengths in devices and systems" rather than vertical integration. In-house production of SiC wafers requires capital investment on the order of tens of billions of yen and long-term technological accumulation. Considering the return on investment, the decision to enter into a long-term contract with a reliable wafer supplier is understandable.

Short-Circuit Withstand Time and Wafer Quality: The Connection Affecting Device Performance

The substance of a long-term contract is not just price and volume. Technical quality standards also become a focal point of negotiations. This is because the performance of SiC devices is directly linked to wafer quality, particularly crystal defect density.

The short-circuit withstand time (SCWT) of SiC MOSFETs is a parameter indicating the time until the device fails during a load short circuit, serving as a grace period before protective circuits operate. For Microchip's SiC MOSFETs (700V/1200V rated), a value of typ. 3μs is listed in the datasheet under specific conditions. The extent to which this value can be maintained depends significantly on wafer uniformity and defect density.

SiC devices have smaller dies and higher current densities compared to silicon, leading to faster temperature rise during short circuits. Therefore, even with the same SCWT value, greater lot-to-lot variation in wafers would necessitate more margin in setting protective circuits, impacting the overall system efficiency. By contractually defining quality specifications and suppressing lot-to-lot variations through long-term agreements, there is also significance in terms of stabilizing device performance.

SCWT and on-resistance (Ron) have a trade-off relationship. Examples include Mitsubishi Electric's introduction of a p-type protective layer in trench-type SiC MOSFETs to improve SCWT, and Rohm's technology for achieving both in their 4th generation devices are known. To maximize the effects of such structural improvements, a stable supply of wafer quality is a prerequisite. Discussions on device design and wafer procurement are, in fact, connected at this point.

As a representative value, Microchip's SiC MOSFETs (700V/1200V) list SCWT of typ. 3μs in their datasheets for specific conditions. This value varies with drain voltage, gate voltage, and junction temperature, tending to increase with lower drain applied voltage or higher junction temperature. A stable supply of wafer quality becomes a prerequisite for suppressing variations in such characteristics and securing design margin for protective circuits.

Supply Risk and Technical Evaluation: Organizing the Decision-Making Criteria

This news is an individual event of "Renesas's procurement decision," but the decision-making criteria revealed from it can be widely shared.

Wolfspeed is progressing with the transition to 8-inch wafers, and the 10-year contract period will inevitably include the generational shift from 6-inch to 8-inch. How to renegotiate terms of quality, price, and volume during this transition period is a critical issue affecting the effectiveness of the contract. When considering similar long-term procurements, the core of contract design is not simply "how many years of supply to secure" but "how to absorb technological changes."

The Other Side of the Industry This Movement Indicates

The 10-year contract between Renesas and Wolfspeed reflects the SiC wafer market's changing nature from "component" to "strategic asset." Companies that secure supply can maintain their product roadmaps, while those that fail to do so are increasingly at risk of falling behind in device performance and shipment volume. This competitive structure is already becoming a reality.

Technologically, device-level challenges such as short-circuit protection via DESAT and improvements in the Ron-SCWT trade-off are progressing in parallel. These are issues inseparable from wafer quality, and the procurement decision of "whose wafers to use" directly impacts the reliability of the final product.

Predicting the exact market size and demand structure 10 years from now is difficult. However, the very fact that major players are moving towards long-term contracts embodies the industry's "collective read" on the continued growth of SiC demand. The next point to watch is how Renesas will deploy the secured wafers for which device generations and applications.