抄録
Various efforts such as the optimization of the production process and the adoption of alternative gas has been made to reduce the emission of PFCs used in the process of semiconductor manufacture.
However, in order to achieve the reduction of PFCs whose consumption is increasing, the exhaust-gas treatment equipment with the high performance of decomposition is needed.
The demands for the equipment from the viewpoint of design for the thermal decomposition are discussed below.
The reductive atmosphere is needed for the thermal decomposition of PFCs to prevent the recombination of dissociated fluorine.
The distributed flame which can effectively apply the point of high temperature of the flame is used to improve the efficiency of heating.
To create the reductive atmosphere, at first, the combustion using excessive concentration of the main burner fuel takes place and next, the auxiliary fuel and the combustion enhancing gas are provided.
In the case of decomposition of CF4, which is one of the most difficult substance to be degraded, high decomposition efficiency was achieved by using O2 for the combustion enhancing gas.
By analyzing the data of the internal temperature distribution of the equipment and the decomposition efficiency of the gases, the decomposition temperature of the typical PFCs to achieve decomposition ability more than 95% are shown below.
CF4 -1600°C, C2F6 -900°C, SF6 -1000°C, NF3 -800°C
