| AVS 55th International Symposium & Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS2-WeA |
| Session: | Plasma Diagnostics, Sensors, and Control I |
| Presenter: | P. Kudlacek, Eindhoven University of Technology, The Netherlands |
| Authors: | P. Kudlacek, Eindhoven University of Technology, The Netherlands R.F. Rumphorst, Eindhoven University of Technology, The Netherlands M. Creatore, Eindhoven University of Technology, The Netherlands M.C.M. van de Sanden, Eindhoven University of Technology, The Netherlands |
| Correspondent: | Click to Email |
The control of the flux and energy of ions bombarding the substrate is crucial to enhance deposited film properties or etch rate at, for example, low substrate temperatures or in weak remote plasmas. The most widespread method for these purposes is biasing because of its simplicity and suitability for operation with both conductive (dc bias) and dielectric (rf or pulsed bias) substrate. Recently, pulsed bias became subject of increased interest mainly due to lower and controllable heat load of the sample and, considering that rf bias inherently leads to bimodal energy distribution of ions bombarding the biased substrate (IED), also a promising technique to reach narrow almost unimodal IED. When pulse-shaped bias voltage is connected to the substrate holder the sheath rebuilding at the beginning of on-pulse and the ion-induced secondary electron emission during the pulse can lead to production of significant amount of fast electrons which can non-locally affect the plasma and near-wall sheath potential as has been reported by Demidov at al. (2005 Phys. Rev. Lett. 95 215002). Therefore, an effect of local and non-local changes of plasma parameters in a reactor with substrate holder biased by pulse-shaped voltage was studied in this work. Non-local changes are discussed on the basis of the electron temperature Te and ion density ni which are determined spatially using a double Langmuir probe technique, while the distribution function of ions bombarding the biased substrate shows local effects of biasing such as additional generation of ions driven by bias voltage and influence of collisions. IEDs are measured by means of a retarding field energy analyzer. Two limit biasing conditions are presented for comparison, namely dc bias and 13.56 MHz rf bias which shows practically no and strong (e.g. almost 5 times higher Te in the distance of 30cm from the biased substrate holder) non-local plasma parameters affection, respectively. All experiments were run in a remote expanding thermal plasma (ETP) reactor, in Ar and Ar/N2 gas mixture compositions under several pressures (up to 35 Pa). The substrate holder was negatively biased (up to -300V) by means of a home designed pulsed power supply operating with a frequency of up to 200 kHz and a variable duty cycle.