Paper PS-ThM10
Characterization of Inductive Coupled Plasma Source RF Power Pulsing for Advanced Surface Treatment Applications

Thursday, October 24, 2019, 11:00 am, Room B131

As device dimensions continue to shrink into the sub-10 nm regime, low electron temperature plasma and radicle energy control become very important factors in the fabrication of microelectronics device. A pulsing plasma reactor [1] is an efficient way to bring down the electron temperature and improve the process window by adding an additional tuning knob. Pulsed plasmas have been widely used in plasma etch tools, as high-density plasmas at low pressure demonstrate excellent plasma charge damage reduction, improved microloading and reduced mask erosion compared to traditional etchers. However, no results have thus far been reported for a high pressure, downstream pulsed plasma reactor for surface treatment and plasma ashing. For advanced surface treatment applications, radical energy control becomes necessary to control either selectivity to underlying films during resist ashing, surface film growth or surface property change. Therefore, it is desired to have radical energy control capability to improve the process window.

In this work, we explore pulsing plasma in a high pressure, downstream, grounded Faraday Shielded ICP source[2]. Source RF power of 13.56MHz frequency with pulsing frequency up to 100kHz and a vacuum capacitor automatch were used in the experiment. The pulsing window was mapped with maximum pulsing frequency 30KHz and duty cycle from 10% to 90%. A Langmuir probe is used to measure the electron energy distribution function (EEDF) developed by Plasma Sensor [3], which is inserted in the reactor 1cm above the wafer pedestal. Due to the limitations of plasma density measurement, ( Langmuir probe requires plasma density above 10^8 cm-3 detection limit) the grid [4] which is used to separate high density and low density plasma, is removed from the reactor to make the measurement possible. Pulsed plasma program performs time resolved measurements of the probe V-I, the plasma parameters and EEDF. Both electropositive (e.g. Ar) and electronegative (O2/N2) plasma are used to study the pulsing plasma. The plasma impedance for the different plasma are read from the matching networks internal I-V probe. Electron temperature, density and afterglow temporal evolution at different pulsing conditions are also discussed.

[1] Pulsed plasma etching for semiconductor manufacturing, Demetre J Economou, J. Phys. D Appl. Phy. 47(2014)

[2] Stephen E. Savas, Brad S. Mattson, Martin L. Hammond, Steven C. Selbrede, Patent US 6143129

[3] Comparative analyses of plasma diagnostics techniques, V. A. Godyak and B. M. Alexandrovich, Journal of Applied Physics 118, 23302 (2015)

[4] Stephen E. Savas, Brad S. Mattson, Patent US 5811022