An optical fiber interleaver and method for aligning the output channels to a set of nominal values in frequency space. Wafer material is removed from the back of the wafer to the level of the vias and scribe marks to form a via opening through the wafer while simultaneously dicing the wafer into individual semiconductor dice. The target rudder angle is a sum of a proportional term proportional to the steering angle and a differential term proportional to the steering angular speed. The gas is preferably carbon dioxide.