The process of silicon carbide oxidation is simple. The silicon carbide substrate can be directly thermally oxidized to obtain SiO2 on the substrate. Silicon carbide is the only compound semiconductor that can obtain high-quality SiO2 through silicon carbide thermal oxidation. The theoretical formula is as follows:
SiC+1.5O2→SiO2+CO
That is, to grow 100nm SiO2, 46nm silicon carbide is consumed. The silicon carbide oxidation process is divided into dry method and wet method.
The rate of silicon carbide surface oxidation is related to the polar of silicon carbide:
Among all crystal planes, the oxidation rate of (000-1) carbon plane is the fastest, and that of (0001) silicon plane is the slowest. The oxidation rate of (000-1) carbon surface is 8-15 times that of (0001) silicon surface. When oxidized at 1000°C for 5 hours, the (000-1) silicon surface is 80 nm, and the (0001) carbon surface is 10 nm. Oxidation of silicon carbide at high temperature is also a destructive method for identifying the polarity.
Moreover, the silicon carbide oxidation rate is close to a parabola:
d^2+Ad=Bt
d is the silicon carbide oxidation film thickness, t is the time, and A and B are the measured parameters.
In fact, there are other oxidation forms:
SiC+O2→SiO2+C
As a result, there may be carbon defects.There are several ways to reduce defects at the interface between SiO2 and SiC:
1. Annealing after silicon carbide oxidation state: Annealing in inert gas (Ar/N2) after thermal oxidation.
2. Oxidation and nitridation: After thermal oxidation, pass N-containing gas (NO/N2O/NH3) for annealing; or directly oxidize in N gas (NO/N2O/NH3).
3. Oxidation or annealing in other atmospheres/solutions: including POCl3/Na solution, etc.
4. Deposit other layers:
- The defect of direct thermal oxidation of silicon carbide is 1.3×10^11cm-2. Returning to the original method, depositing Si, and then thermally oxidizing to SiO2, the number of defects is 1.2×10^10cm-2. It is worth noting that it is very difficult to characterize the interface. TEM, XPS, AES, EELS are all difficult to get good results, so the number is doubtful.
- Deposit other insulators, such as Al2O3, AlN, AlON, etc.
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