Temporal evolution of plasma potential in a large-area pulsed dual-frequency inductively coupled discharge

• Published in: Journal of physics. D, Applied physics Applied physics, 2013-06, Vol.46 (23), p.235203
• Main Authors: Mishra, Anurag, Seo, Jin Seok, Kim, Kyong Nam, Yeom, Geun Young
• Format: Article
• Language: English
• Subjects: Discharges for spectral sources (including inductively coupled plasmas); Dual frequency ICP discharges; Electric discharges; emissive probe; Exact sciences and technology; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; temporal evolution of plasma potential
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/46/23/235203

Using an emissive probe technique in 'saturated floating-potential' mode, an investigation of temporal evolution of plasma potential (Vp) in a large-area pulsed dual-frequency (2 MHz/13.56 MHz) inductively coupled plasma (p-DF-CCP) is carried out. The discharge is sustained by an external type ICP antenna at a pressure of 10 mTorr in argon gas environment. The 2 MHz rf is pulsed at a frequency of 1 kHz and a duty ratio of 50%. The emissive probe is located at the centre of the substrate and 20 mm above (r = 00 mm and z = −20 mm) it. The low-frequency power (P2 MHz) is varied from 100 to 800 W, whereas the high-frequency power (P13.56 MHz) from 100 to 700 W. Vp remains positive during the whole pulse period. The prominent features in the Vp profile remain similar under all operating conditions; however, the magnitude of Vp depends on the applied rf powers. For further investigation, three distinct regions in a typical Vp profile are clearly identified as 'overshoot-immediately after pulse begins', the 'on-time' and the 'off-time'. Vp increases with increasing P13.56 MHz and has reverse trend with P2 MHz. The electron temperature (Te) is calculated using the relation between floating potential (Vf) and plasma potential (Vp) for the argon plasma and it is found that Te increases with increasing P13.56 MHz and decreases with P2 MHz. It is found that Vp could be modulated using a suitable power combination on two frequencies (P13.56 MHz/P2 MHz). This paper is an attempt to investigate the time-resolved Vp and Te with rf powers in a pulsed dual-frequency ICP.