Correlation of RF impedance with Ar plasma parameters in semiconductor etch equipment using inductively coupled plasma

Abstract

The correlation of RF impedance with Ar plasma parameters was analyzed in semiconductor etch equipment using inductively coupled plasma. Since the impedance measured by a VI probe installed behind the RF bias matcher had information for plasma and structural parts of chamber simultaneously, the impedance was corrected by excluding transmission line and peripheral parts of the bias substrate. The corrected impedance was compared with plasma parameters, such as plasma density and electron temperature. The coefficient of determination between the corrected plasma resistance and the theoretical formula of the resistance for bulk plasma was over 0.9 unlike the resistance measured by the VI probe. It is expected that the corrected RF impedance can assist in monitoring the status of plasma and maintaining the quality of the etch process in semiconductor mass production lines.

Correlation of SiO2 etch rate in CF4 plasma with electrical circuit parameter obtained from VI probe in inductively coupled plasma etcher

“…To obtain more precise impedances of plasma and sheath, the impedances of the inner parts of the equipment had to be excluded. As previously shown [11], first, the placement of equipment parts was investigated to design a circuit diagram like figure 2, and then, the impedance of the chamber in the status of vacuum was measured by a network analyzer connected to a proper zig at the almost same location as VI probe. The coaxial-type transmission line in the chamber had the role to supply a bias power to the ESC.…”

“…The capacitance of a vacuum space (C 0 ) was simply calculated from the Z i measured by a network analyzer because only C 0 was serially connected to Z ESC(Puck) and Z wafer when there was no plasma in the chamber. The specific values of the impedances of inner parts and vacuum space could be shown by [11]. When there was a plasma in the chamber, a homogeneous model of capacitively coupled plasma [12] was considered as a plasma circuit.…”

“…The impedance including sheath capacitance (C sh ), plasma resistance (R p ), plasma inductance (L p ), and C 0 referred to Z t which was separated into the impedance of a sheath and a bulk plasma circuit. As previously shown [11], since the phase of Z t was close to −90 • and the amplitude of Z t was almost same as the amplitude of the imaginary part of Z t (X t ), it was assumed that the amplitude of X t approximated to the impedance of the sheath capacitance. The sheath capacitance was obtained as follows:…”

“…They observed that a plasma density and a plasma temperature were strongly correlated to the difference between a plasma potential and a floating potential. Lee et al [11] analyzed the correlation of RF impedance with Ar plasma parameters in etch equipment using inductively coupled plasma. They introduced the method to derive the corrected RF impedance excluding transmission line and peripheral parts of bias substrate, and they showed the corrected plasma resistance was strongly correlated to the theoretical formula of the resistance of bulk plasma.…”

Safety of Chamber Exterior Wall Ground

“…In general, a chamber wall is grounded for safety when experimenting with radio frequency (RF) power [1][2][3][4]. However, although the exterior wall of the chamber is grounded, the RF current does not flow along the ground line.…”