US Patent 10358722 Showerhead assembly

A face plate of a showerhead assembly of a deposition apparatus in which semiconductor substrates are processed includes gas holes arranged in an asymmetric pattern with a hole density which is substantially uniform or varies across the face plate. The face plate can include a lower wall and an outer wall extending vertically upwardly from an outer periphery of the lower wall. The outer wall is sealed to an outer periphery of a back plate such that an inner plenum is formed between the face plate and the back plate. The gas hole pattern in the face plate avoids symmetry which can cause defects on processed substrates.