A wafer transport assembly includes first and second wafer transport modules, and a buffer module coupled between the first and second wafer transport modules. The first and second wafer transport modules and the buffer module are aligned in a single directional axis. The buffer module includes a first buffer stack positioned at a first lateral end of the buffer module, and a second buffer stack positioned at a second lateral end of the buffer module. The first lateral end of the buffer module defines a first side protrusion nested between the first and second wafer transport modules and first and second process modules. The second lateral end of the buffer module defines a second side protrusion that is nested between the first and second wafer transport modules and third and fourth process modules. The first and second wafer transport modules and the buffer module define a continuous controlled environment.