UCLA

Low temperature radio frequency (RF) inductively coupled plasma (ICP) is widely used in semiconductor industry for surface etching and processing. The plasma needs to be highly controllable and uniform. Electronegative gases are often used for their high reactivity, which adds to the complexity. Various measurements were performed in an effort to characterize a pulsed ICP in an industrial etch tool driven by a 2 MHz planar coil, with improved temporal and spatial resolution from previous literature. The operating gas was Ar/O2. The wafer on the bottom electrode can be biased at 1 MHz independently. The decoupling of the driving RF and the bias RF enables separate control over the plasma parameters in the sheath and the bulk region. In the sheath region in contact with the wafer, laser induced fluoresence experiment was conducted. Ar ion angle and energy distributions, drift velocity and sheath dynamics were investigated for different cases of wafer bias. The results showed an instantaneous sheath motion in response to the wafer bias. The ion energy distribution showed a continuous tail extending close to the bias voltage when the bias was turned on during the plasma glow, and a bimodal shape with a high energy peak when the bias was turned on in the afterglow. In the bulk region, RF compensated Langmuir probe, hairpin probe, Bdot probe and photodetachment were used to obtain essential plasma parameters. The electron and negative ions spatial distribution showed significantly different structures in Ar and Ar/O2. Different propagation patterns of the fields and inductive power deposition were also observed.