This research project focuses on scaling-down the size of inductively coupled plasma (ICP) generators so that ICPs can be used in microelectromechanical systems. The ICP currently under investigation is surface micromachined on a glass wafer using electroplated gold. The RF power is coupled to the plasma using a spiral-shaped coil that is 5 mm in diameter. As the radius of the plasma is reduced, the frequency of the electrical energy used to drive the plasma increases. Large ICPs (250 mm radius) typically operate at 2 MHz and 2000 W. The miniature ICP below is driven at 450 MHz using a power of only 0.35 W. The ultimate goal is to reduce the ICP to a size of approximately 1 mm.

Photograph of a microfabricated ICP in a hybrid package

 

A top view of the ICP shown above with a plasma in the chamber

 

A side view of the ICP showing the hybrid package bonded to a 10 mm glass vacuum chamber. The plasma is generated in argon gas at 8 torr using 350 mW of power.

The evolution of the plasma vs. pressure and RF power is displayed above and below for air and argon discharges. The photos were taken with a 35 mm SLR outfitted with a 50 mm lens plus a +4 diopter closeup lens. The plasma is viewed through the lower viewport looking toward the ICP coil.