Characteristics of an 8-cm-diam electron cyclotron resonance source for plasma processing

Performance and characteristics of a microwave source designed for the generation of overdense (Ne≥Ncr=7.4×1010 cm−3) uniform plasmas are presented. Microwave power ( f=2.45 GHz, P=20–1000 W) was introduced into the cylindrical nonresonant (for any TE and TM microwave modes) cavity (D=8.25 cm, L=22 cm) via a matched dielectric window. Two magnetic coils produced the axial static magnetic field of B≥Bce=875 G. Two plasma stream modes were observed: (i) narrow mode with a maximum plasma density on the axis, and with the magnetic field near the introduction window of B≤960 G; and (ii) wide mode with lower but uniform plasma density across the stream, and with magnetic fields near the window of 1000–1200 G. Ion current density of 7–8 mA/cm2 was typical for the narrow mode, and 4–5 mA/cm2 for the uniform mode. Ion current density relationship with gas pressure and microwave power is discussed.