The effect of hole density variation in the PECVD reactor showerhead on the deposition of amorphous carbon layer

In the showerhead structure composed of two stages of porous media, the changes in the ACL (Amorphous Carbon Layer) deposition rate and extinction coefficient were experimentally analyzed and numerically simulated. Depositions were carried out by applying perforated plates with various hole densities in the central region under the conditions of C ₃ H ₆ /N ₂ /He plasma and a 550 °C heater temperature. With a uniform hole density as a reference case, the deposition rate decreased with increasing process pressure, and the maximum deposition rate of 2707 Å/min was achieved at 733 Pa. The deposition rate decreased with the reduced residence time at the total flow rate of over 2000 sccm. The extinction coefficient decreased drastically with increasing molar concentration of C ₃ H ₆ and process pressure. In the case of a high hole density pattern, the deposition rate of the central region of the wafer decreased, but the change of the extinction coefficient was insignificant, while the velocity of the fluid at the center portion was accelerated and the residence time varied with the gradient of velocity. The ACL growth could be optimized by controlling the velocity gradient of the fluid, which could be achieved by modifying the hole density of the perforated plate.