Plasma etching of poly-Si/SiO2/Si structures: Langmuir-probe and optical-emission-spectroscopy monitoring

Application of Langmuir probe technique in depositing plasmas for monitoring of etch process robustness and for end-point detection

“…On the contrary to the case of oxidizing plasma reported in [2] for poly-Si/SiO 2 /Si structures, ion current turns out to be rather noisy signal, which systematic change does not cover stochastic variation. Ion current can not be used as end point signal on Si 3 N 4 /SiO 2 interface in this etch process, and has poor end point detector properties on SiO 2 /Si interface.…”

“…Table 1 presents the results of a complete analysis of IV-curves measured in real time during the etching; also included are plasma-parameter values for an unloaded chamber under the same external conditions of discharge. Also, notice that opposite to the case of etching poly-Si/SiO 2 /Si structures in plasma SF 6 +O 2 [2], there is not the sharp difference between the plasma potentials of a loaded and an unloaded chamber. There is little, if any, change in plasma potential during the end-point stage.…”

“…2a) for measurements in fluorocarbon plasma leads to a drastic falling in both ion and electron currents to the probe due to probe contamination by dielectric films [2]. Due to this current distortion no valid value of any plasma parameter can be obtained from that data.…”

“…Provided that measurement equipment is fast enough to perform IV-curves acquisition with time resolution suitable for end point detection, Langmuir probe measurements can be used for end point detection. Particularly Langmuir end point diagnostics facilities for oxidizing plasma were reported lately [2].…”

Non-invasive in situ plasma monitoring of reactive gases using the floating harmonic method for inductively coupled plasma etching application

“…However, those parameters only affect bulk plasma properties, then have an effect on ion energy and flux, in turn influence the plasma-surface reaction 1 which finally determine etch properties such as etch rate, profile, morphology, wafer surface charging, and surface damage. 2,3 Thus, the characteristics and stability of the plasma are crucial factors that determine the etch properties. Especially, the ion flux and energy impinging on the wafer surface are important in determining the etch properties.…”