| The mode transition from a capacitively coupled mode (E mode) to an inductively coupled mode (H mode) was observed in an inductive Ar plasma source by applying an axially uniform low B field (Bo < 40G). The plasma density in the H mode increased to approximately 50 times the density in the E mode near the antenna after the mode transition. The variation of plasma density for the E to H mode transition shows a strong hysteresis on applying the B field. Plasma is generated by a planar four turn spiral coil antenna, whose axis is parallel to the B field, mounted on the outside the chamber end window. In most of experiments performed, there is no Faraday shield to prevent electrostatic field coupling. The applied fundamental RF was 13.56 MHz and many harmonic components were observed. It turned out that pseudosurface and helicon waves are responsible for sustaining the high density H mode after the mode transition in the presence of low B field.; Beat wave and standing wave patterns of azimuthally symmetric (m = 0 mode) of the first and second harmonic pseudosurface and helicon waves were measured at various densities (n ∼ 9.0 x 10 10 cm3 to 2.2 x 1010 cm -3) and external B fields (12--28 G). At relatively low density, n ∼ 9.0 x 1010 cm-3, the pseudosurface wave was measured at the first harmonic when o c/o > 2.5, while the helicon wave propagated at the second harmonic when oc/o < 2.5. The pseudosurface wave at the first harmonic becomes the helicon wave at relatively high density, n ∼ 2.2 x 1011 cm-3, and high B field, oc/o > 3.3, while the helicon wave changed to the pseudosurface wave at the second harmonic when o c/o < 3.0. |
