A compact retarding field ion energy analyzer has been designed and built to measure the energy distribution of ions bombarding the wafer surfaces placed on radio frequency (rf) biased electrodes in high-density plasma reactors. The analyzer was used to measure the energy distribution of ions impinging on the rf-biased electrostatic chuck in a high-density transformer coupled plasma (TCP) reactor. The effects of TCP power, rf bias, gas composition, and ion mass on the ion energy distributions (IEDs) were demonstrated through Ar, Ne, Ar/Ne, O2 and CF4/O2 discharges. In the operating range studied, the average ion energy increased linearly with increasing rf bias while the ion flux remained constant indicating that independent control of ion flux and energy was achieved in the TCP reactor. Bimodal ion energy distributions resulting from ion energy modulation in the sheath were observed and multiple peaks in the IEDs measured in gas mixtures were identified as ions with different masses falling through the sheath.

A single Langmuir probe technique has been used to measure the electron energy distribution function (EEDF) in an RF (13.56 MHz)-generated argon plasma in a reactive ion etcher. This was achieved by applying a driving RF signal to the probe to compensate for the effects of RF fluctuations in the plasma potential and then using the second differential of the probe characteristics to obtain the EEDF. It is observed that the EEDF is not well represented by a Maxwellian, Optical emission spectra (4600-4900 AA) were also recorded. In argon plasmas, generated at a constant power level, the average electron energy deduced from the Langmuir probe increases as the pressure is reduced below 20 mTorr. At 5 mTorr the average energy is 8.5 eV whereas above 20 mTorr the average energy lies in the range 3.5-5.3 eV. This is found to correlate with the variation in the intensity of an emission line (4s'(1/2)10 from 5p(1/2) at 4702.32 AA) in an excited argon atom, which can be accounted for by the presence of an increasing fraction of higher-energy electrons at lower gas pressures.

Retarding field analyzer for ion energy distribution measurements at a radio-frequency biased electrode Rev. Sci. Instrum. 79, 033502 (2008); 10.1063/1.2890100 Measurement of ion energy distributions using a combined energy and mass analyzer Rev. Sci. Instrum. 78, 083503 (2007); 10.1063/1.2769352Ion energy distributions versus frequency and ion mass at the rf-biased electrode in an inductively driven discharge J.A compact floating retarding-field ion energy analyzer and the accompanying electronics have been designed and built to measure the energy distribution of ions bombarding radio-frequency ͑rf͒ biased electrodes in high-density plasma reactors. The design consists of two main components, a compact retarding field vacuum probe and an integrated stack of floating electronics for providing output voltages, measuring currents and voltages and transmitting data to a computer. The operation and capabilities of the energy analyzer are demonstrated through ion energy distribution measurements conducted on a 4 MHz rf-biased electrostatic chuck in a 13.56 MHz high-density transformer coupled plasma ͑TCP͒ reactor. The analyzer is capable of operating while floating on several hundreds of volts of rf bias and at pressures up to 30 mTorr without differential pumping. The effects of pressure ͑2-30 mTorr͒, TCP power ͑500-1500 W͒, rf-bias power ͑0-800 W͒, gas composition, and ion mass on the ion energy distributions are demonstrated through Ar, Ne, and Ar/Ne discharges.

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