The difference between dummy, research, production grade SiC substrates

SiC substrates are a core material for third-generation semiconductor device manufacturing. Their quality grade classification needs to precisely match the needs of different stages, such as semiconductor equipment development, process verification and mass production. The industry generally categorizes SiC substrates into three categories: dummy, research, and production grade.  A clear understanding of the differences between these three types of substrates can help to achieve the optimal material selection solution for specific application requirements.

1. Dummy-grade SiC substrates

Dummy-grade SiC substrates have the lowest quality requirements among the three categories. They are usually manufactured by using the lower-quality segments at both ends of the crystal rod and processed through basic grinding and polishing processes.

The wafer surface is rough, and the polishing accuracy is insufficient; their defect density is high, and threading dislocations and micropipes account for a significant proportion; the electrical uniformity is poor, and there are obvious differences in the resistivity and conductivity of the entire wafer.  Therefore, they have an outstanding cost-effectiveness advantage. The simplified processing technology makes their production cost much lower than the other two substrates, and they can be reused many times.

Dummy-grade silicon carbide substrates are suitable for scenarios where there are no strict requirements for their quality, including capacity filling during semiconductor equipment installation, parameter calibration during the equipment pre-operation stage, parameter debugging in the early stages of process development, and equipment operation training for operators.

2. Research grade SiC substrates

The quality positioning of research-grade SiC substrates is between dummy grade and production grade and must meet the basic electrical performance and cleanliness requirements in R&D scenarios.

Their crystal defect density is significantly lower than that of the dummy grade, but  do not meet production-grade standards. Through optimized chemical mechanical polishing (CMP) processes, surface roughness can be controlled, significantly improving smoothness. Available in conductive or semi-insulating types, they exhibit electrical performance stability and uniformity across the wafer, meeting the precision requirements of R&D testing.  Therefore, their cost is between that of dummy grade and production grade SiC substrates.

Research grade SiC substrates are used in laboratory R&D scenarios, functional verification of chip design solutions, small-scale process feasibility verification, and refined optimization of process parameters.

3. Production-grade SiC substrates

Production-grade substrates are the core material for mass production of semiconductor devices. They are the highest quality category, with a purity of over 99.9999999999%, and their defect density is controlled at an extremely low level. 

After high-precision chemical mechanical polishing (CMP) treatment, the dimensional accuracy and surface flatness have reached the nanometer level, and the crystal structure is close to perfect. They offer excellent electrical uniformity, with uniform resistivity across both conductive and semi-insulating substrate types. However, due to rigorous raw material selection and complex production process control (to ensure high yield), their production cost is the highest of the three substrate types. 

This type of SiC substrate is suitable for large-scale manufacturing of final-shipment semiconductor devices, including mass production of SiC MOSFETs and Schottky barrier diodes (SBDs), manufacturing of GaN-on-SiC RF and microwave devices, and industrial production of high-end devices such as advanced sensors and quantum equipment.