Experimental and theoretical study of two-dimensional ion flux uniformity at the wafer plane in inductively coupled plasmas

Tae Won Kim, Eray S. Aydil

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


A two-dimensional array of planar Langmuir probes manufactured on a 200-mm-diameter silicon wafer was used to measure the spatial distribution of ion flux impinging on the wafer surface in various discharges of electropositive (Ar) and electronegative (SF6 and Cl2) gases maintained in an inductively coupled plasma etching reactor with a planar spiral coil. In conjunction with the experiments, a two-dimensional fluid model of the plasma was developed to capture the dependence of the ion flux uniformity on plasma operating parameters and reactor geometry through a set of dimensionless numbers which are the ratios of various time and length scales intrinsic to the discharge. These dimensionless ratios include reactor dimensions, the skin depth, the electron energy relaxation length, ion diffusion length, and ionization and attachment rates. The model provides a simple framework within which the spatial variation of ion flux in inductively coupled plasmas can be understood. The approach captures the dependence of ion flux uniformity on plasma operating variables such as pressure and feed gas composition.

Original languageEnglish (US)
Pages (from-to)614-627
Number of pages14
JournalIEEE Transactions on Plasma Science
Issue number4 II
StatePublished - Aug 2003

Bibliographical note

Funding Information:
Manuscript received November 25, 2002; revised March 10, 2003. This work was supported by the State of California SMART program under Contract SM99-01, and by the following participating companies: Advanced Energy, ASML, Atmel Corporation, Advanced Micro Devices, Applied Materials, Asyst Technologies Inc., Cymer, Etec Systems Inc., Intel Corporation, KLA-TENCOR, Lam Research Corporation, Nikon Research Corporation, Novellus Systems Inc., Silicon Valley Group, and Tokyo Electron Limited.


  • Chlorine plasma
  • Discharge modeling
  • Electronegative discharge
  • Inductively coupled plasma
  • Ion flux probe
  • Langmuir probe
  • Plasma etching
  • Plasma uniformity
  • Sulfur hexafluoride plasma


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