Semiconductor processing chamber multistage mixing apparatus

A semiconductor processing system comprising:

• a remote plasma unit;
• a processing chamber comprising:
• a gasbox defining a central,
• a blocker plate coupled with the gasbox, wherein the blocker plate defines a plurality of apertures through the blocker plate, and
• a faceplate coupled with the blocker plate at a first surface of the faceplate;
• and
• a mixing manifold coupled with the gasbox, wherein the mixing manifold is characterized by a first end and a second end opposite the first end, wherein the mixing manifold is coupled with the processing chamber at the second end, wherein the mixing manifold defines a central channel through the mixing manifold that is fluidly coupled with the central channel defined through the gasbox, wherein the mixing manifold defines a port along an exterior of the mixing manifold, wherein the port is fluidly coupled with a first trench defined within the first end of the mixing manifold, wherein the first trench is characterized by an inner radius at a first inner sidewall and an outer radius, wherein the first trench provides fluid access to the central channel through the first inner sidewall, wherein the mixing manifold further comprises a second trench defined within the first end of the mixing manifold, wherein the second trench comprises an annular trench, wherein the second trench is located radially outward from the first trench, and wherein the port is fluidly coupled with the second trench.