Executive Summary 

The rapid adoption of Silicon Carbide (SiC) MOSFETs in electric vehicles, renewable energy systems, and industrial power conversion is driving the need for more reliable, efficient, and scalable device architectures. Two of the most critical process steps impacting performance and reliability in SiC MOSFETs are the Gate Oxide and Final Passivation layers. 

Beneq, a pioneer in industrial Atomic Layer Deposition (ALD), has developed a suite of advanced ALD solutions using the Beneq Transform® platform to address these specific challenges. This white paper presents the technical motivations, integration challenges, and enabling capabilities of ALD for SiC MOSFET gate oxide and final passivation stacks—and highlights Beneq’s differentiated offerings for automotive-grade, high-volume manufacturing. 

Silicon Carbide (SiC) MOSFETs are pivotal in modern power electronics, offering superior voltage handling, efficiency, and thermal performance. Gate oxide integrity and interface quality are critical drivers of device performance and reliability. Beneq’s Atomic Layer Deposition (ALD) offerings (notably the Transform™ platform) empower precise, high quality gate oxide stacks and passivation coatings. At ICSCRM 2024, Beneq introduced compelling process solutions that underscore significant reductions in interface trap density (Dit) and dramatic improvements in hysteresis and leakage characteristics, further reinforcing the transformative role of ALD in SiC MOSFET fabrication. 

Introduction: The Rise of ALD for SiC Power Electronics 

Silicon Carbide (SiC) MOSFETs offer significant performance advantages over traditional silicon counterparts: 

• Higher breakdown voltage
• Lower switching losses 
• Higher temperature operation 
• Smaller die size at higher power densities 

However, the material structure and wide bandgap nature, robust physical properties and advanced device architectures introduce unique materials and integration challenges, especially at the gate oxide/semiconductor interface. Poor interface quality, oxide reliability, and surface states directly affect threshold voltage stability, channel mobility, and long-term reliability under high electric field stress.  

These challenges placed new emphasis on advanced thin-film deposition solutions. ALD is uniquely suited to meet these demands, and Beneq’s Transform ALD cluster tool is engineered to deliver. 

Beneq Transform®: A Versatile ALD Platform for the Ramp of ALD in SiC MOSFETs 

The Beneq Transform® is a modular cluster tool supporting up to four process modules with full automation, substrate handling, and vacuum integration. Its architecture enables: 

• In-situ multi-layer stacks without breaking the vacuum, 
• Batch processing for high-throughput mini-batch thermal processes, 
• Single-wafer plasma-enhanced processes with Atomic Layer Annealing (ALA) capabilities for interface-sensitive applications,  
• Advanced in-situ surface nitridation techniques. 

This platform flexibility enables deposition of SiO2, High-k (AL2O3, HfO2) and Nitride (AlN, SiN) films with tailored properties for SiC use cases—all within a single toolset. 

ALD Processes and Application Use Cases in SiC MOSFET Technologies 

1. Advanced Conformal Gate Oxides

Key Challenges: 

• High interface trap densities (Dit) at the SiC–SiO₂ interface impede channel mobility and threshold voltage stability. 
• Conventional thermal oxidation and other deposition methods, such as LPCVD methods, struggle to reliably reduce these traps on advanced trench architectures, especially those arising from carbon-related defects. 

At ICSCRM 2024, Beneq presented a high-impact study on SiO₂ dielectric stacks for 4H-SiC MOS capacitors, developed with the TFS 200 R&D and Transform® high-volume cluster tools.  

ALD as a Solution: 

Further innovation enables best-in-class interface quality, hysteresis control, and dielectric reliability for SiC MOSFET gate oxides for High Volume Manufacturing. 

• Surface plasma preclean to remove carbon clusters and oxycarbide phases. 
• Advanced in-situ surface nitridation to passivate the surface dangling bonds. 
• Deposition of a PEALD SiO₂ interfacial layer with ALA for best interface control and film quality. 
• Deposition of a thick, high-quality ALD SiO₂ layer at high-throughput. 
• Capability to engineer Gate Oxide stacks with High-k (AL2O3, HfO2) and Nitrides (AlN, SiN) for lower Rds, ON and higher current densities. 

2. High Performance Final Passivation for High Voltage SiC devices

Key Challenges: 

Final passivation plays a vital role in ensuring device stability, moisture and ion barrier performance, and long-term reliability in power electronics. PECVD Si₃N₄/SiO₂ stacks suffer from high defectivity or pinholes, low density 

• Lack of conformality other complex high topography structures 
• Mechanical stability over materials such as Polyimide 
• Inadequate barrier performance under high humidity and bias conditions 

Consequently, ALD has emerged as a key technology in More-than-Moore (MtM) semiconductor segments for final passivation where uniform, high-quality coatings are essential. 

ALD as a Solution: 

ALD delivers markedly better performance than conventional passivation methods: 

• Superior conformity and uniformity on complex topographies 
• Higher quality, denser films offering improved barrier performance against moisture and mobile ions 
• Dual-stack/nanolaminates of Al₂O₃/HfO₂ or Al₂O₃/SiO₂ for best-in-class barrier and dielectric performance 

These benefits directly translate into improved long-term reliability and environmental resilience of SiC MOSFETs devices with demonstrated robust performance beyond several 1000 hours H3TRB test.  

Advantages of the Beneq Transform® for Next-Generation SiC MOSFETs 

• Process versatility: Thermal and plasma-enhanced ALD modules 
• Unbroken vacuum processing: Improved film interfaces and purity 
• Batch and single-wafer process modules: Optimized throughput and precision 
• Modular upgradability: Future-proof investment for expanding process needs 

The Beneq Transform® ALD cluster tool offers an advanced, upgradeable configuration including in-situ plasma preclean, surface nitridation, PEALD interfacial layers with ALA for best interface control and film quality. 

Summary and Outlook 

Beneq’s ALD solutions, powered by the Beneq Transform® platform, are tailored for the stringent requirements of SiC MOSFET gate oxide and final passivation layers. As power electronics scale to higher voltages, temperatures, and reliability demands, ALD will play a pivotal role in enabling robust, high-yield SiC manufacturing. 

Beneq is committed to co-developing solutions with SiC device makers and ecosystem partners to push the boundaries of materials engineering for the next generation of power semiconductors.