Characteristics of a dual‐radio‐frequency cylindrical inductively coupled plasma

Abstract

The plasma parameters such as electron density, effective electron temperature, plasma potential, and uniformity are investigated in a new dual-frequency cylindrical inductively coupled plasma (ICP) source operating at two frequencies (2 and 13.56 MHz) and two antennas (a two-turn high-frequency antenna and a six-turn low-frequency (LF) antenna). It is found that the electron density increases with 2 MHz power, whereas the electron temperature and plasma potential decrease with 2 MHz power at a fixed 13.56 MHz power. Moreover, the plasma uniformity can be improved by adjusting the LF power. These results indicate that a dual-frequency synergistic discharge in a cylindrical ICP can produce a high-density, low-potential, low-effective-electron-temperature, and uniform plasma. KEYWORDScylindrical inductively coupled plasma source, dual-frequency discharge INTRODUCTIONPlasma source development has been one of the major research activities in the low-temperature plasma community because of the increasingly challenging demands for plasma processing. [1][2][3] Various plasma sources, e.g. inductively coupled plasma (ICP) sources, [4][5][6][7] capacitively coupled plasma (CCP) sources, [8,9] electron cyclotron resonance (ECR) sources, [10] and microwave plasma sources, [11] are being extensively investigated by many researchers. Among these plasma sources, ICP sources as a potential candidate for large-area fabrication have attracted a great amount of attention because of their desirable advantages such as a relatively higher plasma density, low electron temperature, low operating gas pressure, and reduced ion damage to the substrate, as well as the possibility of independent control of ion energies and ion fluxes by using a dual-frequency (DF) discharge. [4][5][6][7]12] During plasma processing, desirable plasma characteristics, such as a high plasma density, low electron temperature and plasma potential, and good plasma uniformity are of great importance. Typical examples arise in the etching and deposition processes of semiconductor manufacturing, in which a high plasma density is helpful for achieving high processing rates and production throughput of active particles, whereas a lower electron temperature and plasma potential can avoid electrical and physical damage to the substrate. [13] Moreover, the wafer quality depends critically on plasma uniformity.In order to optimize the plasma characteristics of an ICP source, various methods including changing the antenna shape, [14,15] employing multiple low-inductance antennas, [16] enhancing the discharge by a ferromagnetic core , [3,17,18] and using a DF dual-antenna discharge [6,7,13,[19][20][21] have been proposed. Among these methods, DF technology appears particularly promising. About a decade ago, DF discharge technology operating with two power supplies of differing frequencies began to be used in CCP sources for etching dielectric thin films. The high-frequency (HF) source tends to have more influence on the plasma density and hence ion flux to the electrode, wh...

Investigations on the effect of process parameters on the growth of vertically oriented graphene sheet in plasma‐enhanced chemical vapour deposition system

“…[17] The plasma characteristics such as number density and temperature of these plasma species, that is, neutral and charged species (electrons and positively charged ions) in the plasma depends on the PECVD process parameters such as total gas pressure, input plasma power, feedstock gas mixture ratio, and substrate temperature. [18][19][20][21][22] Therefore, by tuning the PECVD process parameters, one can deterministically control the structural and growth characteristics of the VOGS as the fluxes of neutral and charged species towards the substrate surface are controlled by the PECVD process parameters.…”