Slide 44 of 64
This picture is important because it tells us what the critical, processing dimensions are, or how easy to manufacture the process might be. Recall that shrinking of the emitter is only necessary till the power dissipation of the device is acceptably small. Speed is still primarily set by the base transit time. This is a vertical dimension. Mitigating against the mass processing are the large number of plates required to pattern the device features for such intricate devices.