Chinese SiC Manufacturers: Selection Criteria

Many teams are divided internally on whether to adopt Chinese SiC manufacturers. Some voices express concerns about "quality," while others acknowledge the reality that "costs cannot be ignored." However, answering this question with a simple "we won't adopt because it's Chinese" or "we will adopt because it's cheap" is too simplistic. What's truly being questioned is the framework for evaluation: how can we reasonably make a decision by verifying specific aspects?

Why "Cheap and Nasty" No Longer Suffices

Including BYD Semiconductor, SICC (Beijing TANKED), and those spun off from CREE, Chinese SiC suppliers have rapidly expanded their product lines since the 2020s. They are no longer just substituting commodity parts; they are beginning to supply SiC MOSFETs with 1200V breakdown voltage for industrial equipment and solar inverters, leading to more situations where they are compared directly with leading European and Japanese suppliers.

From a technological maturity perspective, SiC MOSFETs have a critical metric called "short-circuit withstand time (SCWT / Tsc)." This is the duration a device can withstand a short-circuit fault before failing, defining the grace period for protection circuits to operate. The shorter this value, the less margin designers have on the gate driver side.

As seen with Microchip's (formerly Microsemi) 700V/1200V SiC MOSFETs, which list a typical SCWT of 3μs on their datasheets, the nominal short-circuit withstand time varies by manufacturer. Whether this value is listed with "conditional notation" or is "not specified" on Chinese manufacturers' datasheets can be one clue to their technological maturity.

How to Discern Actual Performance

When evaluating Chinese SiC manufacturers, relying solely on datasheet numbers is not always sufficient. What's crucial is whether the datasheet specifies "under what conditions" those numbers were obtained.

Short-circuit withstand time depends on the combination of drain applied voltage, gate applied voltage, and junction temperature. If the conditions are relaxed, the numerical value can appear larger. From an evaluation standpoint, the question of "is this a value reproducible under our own system's operating conditions?" becomes a key decision factor.

Furthermore, SiC devices have high current density and small die sizes, leading to faster temperature rise during a short-circuit compared to silicon. Protection circuits must be designed with shorter response times, making evaluation in combination with the gate driver indispensable. With this in mind, confirming "traceability of evaluation conditions" on Chinese manufacturers' datasheets is the starting point for assessing technical reliability.

On-resistance (Ron) and short-circuit withstand time are in a trade-off relationship. Rohm's 4th generation SiC MOSFETs achieving both low RonA and high short-circuit withstand time through their unique structure, and Mitsubishi Electric significantly improving SCWT by introducing a p-type protective layer in their trench-type SiC-MOSFETs, are concrete examples of different approaches to this problem. By cross-referencing datasheets and technical documents, one can gain some insight into how Chinese manufacturers are addressing similar challenges—whether through structural innovations or by adjusting specifications to match numbers.

How to Assess Supply Risk and Business Continuity

Alongside technical specifications, supply risk evaluation needs to be considered as a separate dimension. The main suppliers of SiC wafers are concentrated among Wolfspeed, II-VI (Coherent), and SiCrystal. Understanding where Chinese SiC device manufacturers procure their upstream wafers is a crucial point for assessing overall supply chain risk.

Within China, companies like SICC (Beijing TANKED) and Tankeblue (part of Shengshi Jidian Group) are pursuing in-house wafer production. However, it is considered that there is still a delay of several years compared to Western and Japanese manufacturers in terms of stable mass production of 6-inch wafers and the timeline for transitioning to 8-inch. Just as Mitsubishi Electric is jointly developing 8-inch SiC substrates with Coherent, securing next-generation substrates is directly linked to long-term competitiveness. When adopting Chinese manufacturers, examining "the structure of wafer procurement" in addition to evaluating the device itself will make it easier to forecast supply risks.

Another dimension is geopolitical risk and export control trends. US sanctions against China's semiconductor industry primarily target manufacturing equipment, EDA, and advanced logic. However, some manufacturing equipment for power semiconductors is also subject to these regulations. The sustainability of Chinese SiC manufacturers' production capacity is inextricably linked to changes in this regulatory environment. The status of obtaining certifications within the European Union (such as AEC-Q101) and whether transaction records with Japanese, European, and American Tier 1 suppliers are publicly available serve as indirect indicators of confidence in continuous supply.

Compatibility with Protection Circuit Design – A Subtle but Significant Aspect

Before integrating Chinese SiC manufacturers into actual systems, confirming compatibility with protection circuit design is a crucial hurdle in practical implementation. The standard method for short-circuit protection is DESAT (desaturation) detection, a mechanism that monitors the drain-source voltage (VDS) during the on-state and turns off the gate upon detecting overcurrent.

Parameters adjusted by designers when implementing DESAT include the DESAT voltage threshold (VDESAT), DESAT detection current (IDESAT), and short-circuit blanking time. If these values do not align with the specifications of the gate driver IC and the short-circuit characteristics on the SiC MOSFET's datasheet, there is a risk of the protection operating too sensitively and causing malfunctions, or conversely, triggering too late and leading to failure. Whether these parameters are listed on Chinese manufacturers' datasheets and whether recommended gate driver combinations are indicated are information that influences the accuracy of the design.

Furthermore, as SiC MOSFETs' RDSon increases with temperature, limiting the saturation current, their short-circuit withstand capability tends to improve at higher temperatures. This affects the calculation of design margins, but the extent to which Chinese manufacturers disclose temperature dependency graphs on their datasheets varies. The availability of this information also impacts the precision of technical evaluation.

The Question is Being Reframed from "Can We Adopt?" to "Where Can We Use Them?"

Discussing the adoption of Chinese SiC manufacturers as "full adoption or complete exclusion" does not align with the current market environment. A more practical decision-making framework is: "Under what conditions can we proceed with adoption, considering the risk tolerance for each application?"

For instance, in applications like solar inverters and industrial UPS, the operating environment is more stable than in automotive applications, and there is more design freedom. In such applications, a three-step approach involving disclosure of reliability test data, confirmation of gate driver compatibility, and sample evaluation may allow for a reasonable assessment of Chinese manufacturers' products. On the other hand, for applications like automotive inverters and aerospace, obtaining AEC-Q101 certification and robust long-term reliability data become prerequisites for adoption.

As a representative example, Microchip's SiC MOSFETs (700V/1200V breakdown voltage) clearly state "typ. 3μs" for short-circuit withstand time on their datasheets, along with values under specific conditions. A side-by-side comparison of whether Chinese manufacturers disclose information with similar granularity, and how detailed their measurement conditions (VDS, VGS, Tj) are, serves as the starting point for technical evaluation.

Ultimately, the decision to adopt Chinese SiC manufacturers is not a qualitative question of "can we trust them or not," but rather a reframed question: "Is our company's evaluation process designed to extract the necessary information from their datasheets?" If the following four points can be confirmed from the datasheets and technical documents—clear specification of short-circuit withstand time conditions, handling of the on-resistance trade-off, gate driver compatibility information, and reliability test data—then a foundation for internal consensus towards adoption can be built. Conversely, proceeding with adoption without these elements in place carries high risk, regardless of the manufacturer's country of origin.