AVS 47th International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS-TuP

Paper PS-TuP1
Frequency Effects to E - H Discharge Mode Transitions in Inductively Coupled Plasmas

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: M. Edamura, Hitachi, Ltd., Japan
Authors: M. Edamura, Hitachi, Ltd., Japan
E. Benck, National Institute of Standards and Technology
Correspondent: Click to Email
Inductively coupled plasmas (ICPs) have been used for plasma processes because of their high density and low pressure operation. Recently relatively lower density plasmas are used for many etching processes because the newest semiconductor devices have very small structures. Especially when ICP etching reactors are driven at low power, the effect of E-discharge (capacitive coupled discharge) can not be neglected. There are a wide variety of ICP reactors and the characteristics of E-discharge strongly depends on the reactor design. In this work, frequency effects to ICPs and E - H discharge mode transitions in ICPs are examined by Langmuir probe measurement. An ICP modified GEC reference cell and the discharge frequencies of 6.28 MHz, 13.56 MHz and 20.0 MHz were used for the experiment. By increasing discharge power, plasmas jump to high density H-mode discharges from low density E-mode discharges at certain powers. Higher frequency makes the voltage of the coil and the E-mode density higher and thus the E-H mode transitions occur at lower power. On the other hand, higher frequency makes the density of H mode lower because contribution of E-discharge in H mode makes the efficiency of plasma generation lower. Electron energy distribution functions (EEDFs) of 20 MHz discharge shows a high energy tail around 7-15 eV caused by the E-discharge between the coil and the plasma. Once the E-discharge contribution was removed by inserting an electrostatic shield, significant difference of EEDFs was not observed at these three frequencies.