High purity SiC (silicon carbide) substrate, which is for microwave device and graphene epitaxial growth, can be provided by PAM-XIAMEN – a SiC substrate supplier. Among all the usages, epitaxial graphene growth on high-purity semi-insulating silicon carbide substrate is expected to produce high-performance graphene integrated circuits, which is currently a hot spot in international research and development. For Graphene Growth, HPSI SiC wafer need corresponding quality to make sure quality. 100 mm diameter SiC substrates should meet the following technical requirements:
1. Technical Requirements for Epitaxial Graphene on Silicon Carbide
- 100% Semi-insulating SiC wafers of 100 mm diameter with minimum crystal defects,MPD<5/cm2;
- 100% high-purity on-axis type single-crystal 4H-SiC(0001) with no intentional doping;
- Surface oriented parallel to the (0001) crystal plane to within 0.10 degree;
- SiC(0001) surface is Epi-Ready polished substrate on which graphene can be grown;
- Wafer bow is less than 25 micrometers for each wafer.
HPSI SiC Wafer for Graphene Growth
2. High-purity Semi-insulating Silicon Carbide Preparation Process
PVT method can be used to grow HPSI SiC substrate. In order to prepare high-resistance non-conductive silicon carbide (semi-insulating type), it is necessary to add vanadium (V) impurity during growth. Vanadium can generate electrons and holes, so that the electrons generated by it can neutralize boron and aluminum. The generated holes neutralize the electrons generated by nitrogen, so the grown silicon carbide wafer has almost no free electrons and holes, forming a high-resistance non-conductive wafer, that is high purity semi-insulating cubic SiC substrate. The process of SiC substrate doping vanadium is complicated, so semi-insulating silicon carbide is difficult to prepare, and the cost is high. In recent years, there has been a method of achieving high-resistance semi-insulating 4H-SiC substrate through point defects.
Another silicon carbide crystal growth method is high temperature chemical vapor deposition (HTCVD). It uses a gaseous high-purity carbon source and a silicon source to synthesize silicon carbide molecules at about 2200℃, and then condense and grow on the seed crystal. The growth rate is generally about 0.5~1mm/h, which is slightly higher than the PVT method. N-type dopants or P-type dopants are not added during the SiC substrate growth, the 4H-SiC wafer grown is a high-purity semi-insulating (HPSI) semiconductor. In addition, the HPSI SiC wafer has a carrier concentration ranging from 3.5×1013 to 8×1015/cm3 and has a relative high electron mobility.
3. Epitaxial Growth of Electronic Grade Graphene on SiC Substrate
The thermal decomposition is a good way to obtain epitaxial graphene growth on silicon carbide. It can grow on the Si-plane or C-plane due to the SiC substrate properties. The SiC epitaxy method for the preparation of graphene has become the most industrialized preparation of graphene because the method is simple and controllable and can get large-area high-quality graphen. Therefore, the method of epitaxial growth of graphene on high-purity semi-insulating SiC substrate is considered to be the most promising method. The formation mechanism is as follows:
Heat the carbon surface (0001) surface or silicon surface (0001) surface of 4H-SiC / 6H-SiC wafer substrate in a high vacuum environment to about 1600℃. After the silicon atoms are fully sublimated, a layer of amorphous carbon atoms is left on the surface. Maintaining this temperature, these carbon atoms will restructure on the surface substrate SiC wafer in sp mode to form graphene. Using this epitaxial growth method, higher quality and larger size graphene on SiC substrate can be obtained.