Numerical Simulation of the Effect of APCVD Reactor Tilted Ceiling Height on Silicon Epitaxial Layer Thickness Uniformity

As the linewidth of semiconductor nanostructures continues to decrease, the criteria for acceptable surface homogeneity of silicon (Si) epi-films are becoming increasingly stringent. To address this challenge, the effect of different tilted ceiling heights on the Si epi thickness homogeneity in an atmospheric pressure chemical vapor deposition (APCVD) reactor is investigated numerically. In this study, the deposition temperature on the wafer is controlled at 1373 K. When a tilted ceiling with decreasing height along the streamwise direction is used, the average gas mixture velocity increases with the streamwise direction, which can reduce the impact of flow distortion caused by the rotation of the susceptor. At the same time, the growth of the reaction boundary layer on the wafer is suppressed, which helps with the diffusion of trichlorosilane (TCS) on the wafer surface. This makes the drop in the TCS concentration along the streamwise direction more linear, thereby improving the linearity of the growth rate on the wafer surface along the streamwise direction. Therefore, the present results for a reactor without an inlet plate show that the thickness homogeneity across the entire surface of the wafer after a complete susceptor rotation can be significantly improved by linearly reducing the ceiling height in the streamwise direction. A further increase in the inclination of the inclined ceiling leads to a further improvement in the deposition homogeneity. However, the growth rate values at the same position perpendicular to the streamwise direction are inconsistent, which is not conducive to deposition homogeneity. This shortcoming can be improved upon by using a four-inlet plate reactor with an inclined top plate and by properly selecting the position of each partition and the inlet gas mixture velocity of each inlet channel, thereby greatly increasing the deposition homogeneity of the Si epi-layer. For the cases considered in this study, the deposition thickness non-homogeneity across the wafer surface decreased from 38% to 3%.