Analysis of pulsed high-density HBr and Cl2 plasmas: Impact of the pulsing parameters on the radical densities

Abstract

International audienceThe dynamic of charged particles in pulsed plasma is relatively well known since the 1990s. In contrast, works reporting on the impact of the plasma modulation frequency and duty cycle on the radicals' densities are scarce. In this work, we analyze the impact of these modulation parameters on the radicals' composition in Cl2 and HBr plasmas. The radicals' densities are measured by broad-band UV and vacuum-ultraviolet (VUV) absorption spectroscopy and modulated-beam mass spectrometry. We show that pulsing the rf power allows controlling the plasma chemistry and gives access to the plasma conditions that cannot be reached in continuous wave plasmas. In particular, we show that above 500 Hz, the pulsing frequency has no influence on the plasma chemistry, whereas in contrast the duty cycle is an excellent knob to control the fragmentation of the parent gas, thus the chemical reactivity of the discharge. At low duty cycle, a reduced gas fragmentation combined with a large ion flux leads to new etching conditions, compared to cw plasmas and the expected consequences on pulsed-etching processes are discussed

Development of plasma etching processes to pattern sub-15 nm features with PS-b-PMMA block copolymer masks: Application to advanced CMOS technology

“…However, we have also investigated the possibility of using the BCP template to pattern a dual hard mask [silicon anti-reflective coating/amorphous carbon (Si-ARC/a-C)] that is typically used to etch materials in the microelectronic industry 3 instead of the single SiO 2 hard mask. [20][21][22][23][24][25] Both reactors are connected under vacuum to a quasi-in situ XPS analyzer, which can be used for sample chemical composition measurement. The Si-ARC layer acts as an antireflective coating during photolithography and is also used to transfer the resist patterns into the organic mask.…”

Patterning of silicon nitride for CMOS gate spacer technology. III. Investigation of synchronously pulsed CH3F/O2/He plasmas

“…It has been shown by Bodart et al 13 that radical density is controlled by the duty cycle in synchronously pulsed HBr and Cl 2 plasmas. Moreover, since the plasma chemistry is controlled by the duty cycle, it follows that the value of the ion flux in the ON period is also strongly dependent on the duty cycle because both the chemical composition and electronegativity of the plasma are different.…”

“…Recent experiments performed in ICPs have shown that the duty cycle has a strong influence on the plasma chemistry: when the duty cycle is decreased, the fragmentation of the plasma molecules is reduced and the plasma becomes chemically less reactive. 13 Furthermore, because the timescales for radical production and loss are longer than the pulsing period, the densities of radicals are a) Electronic mail: romuald.blanc@st.com not modulated during the plasma pulses. By contrast, the ion flux and energy are strongly modulated and the wafer is bombarded by high energy ions during the ON time of the synchronously pulsed plasma only.…”

Directed self-assembly of PS-b-PDMS into 193nm photoresist patterns and transfer into silicon by plasma etching

“…However, these control parameters are not always sufficient to reach the appropriate etching characteristics at the nanoscale and new plasma control parameters are required to improve plasma performances. One solution is to use pulsed plasma etching processes, currently developed in our laboratory [20,21,22]. Pulsing the plasma leads to major plasma modifications.…”