Small Plasma Space with a Small Plasma Source and Its Advantage in Minimal Fab

We have developed an inductively-coupled plasma-reactive ion etching system (ICP-RIE) as a human-size tool of Minimal Fab for processing a half-inch wafer. The etching system has performed a Bosch etching process with a short switching cycle in a small chamber with a volume of 1/4 L. For the small chamber, we use a frequency of 100 MHz that is higher than the typical frequency of 13.56 MHz. The power consumption at 100 MHz is only ～ 40W. The Si etching rate of the Bosch process is ～ 2.5 μm/min. Moreover, residence times of deposition gas (C4F8) and etching gas (SF6) are estimated to be ～ 0.2 second, and actually waiting times until feeding one of the gases into the chamber after the stop feeding the other gas are nominally set to be zero. The resultant Bosch cycle time of the alternative feeds of the two gases is only 2 sec. For the high-speed Bosch cycle of 2 sec, the resultant etching sidewall of Si structure becomes a scallop-less straight wall.