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Optical emission spectroscopy study of precursors in ICP assisted DC magnetron sputtering deposition of TiN
Author
Chan, Marvin Weng Yew
Supervisor
Xu, Shuyan
Abstract
The hysteresis characteristics of plasmas in DC magnetron sputtering and low frequency inductively coupled plasma (LFICP) assisted DC magnetron sputtering, together with their effects on thin film (i.e. TiN) deposition on different substrates are investigated in this thesis.
The high density ICP assisted DC magnetron sputtering set-up. which has been used in this work, is described in detail. The apparatus may operate in three distinct modes: as a conventional DC magnetron sputtering device, a conventional ICP source and an ICP assisted DC magnetron sputtering device. The discharge behaviours with respect to each of the three different modes are described.
The operating principles of a conventional DC magnetron sputtering discharge have been presented qualitatively. Two distinct discharge modes (i.e. the D-mode and the M-mode), belonging to the DC magnetron sputtering have also been identified. The dynamic mechanism for the mode production and features of the mode transition point are discussed. It is believed that distinction of the two discharge modes have been made and explained for the very first time. Hysteresis loops have also been observed for the cathode current (I) vs. cathode voltage (V). which indicates bi-stability of plasma. In addition, comparisons between experimental data with the typical empirical relationship between I and V (i.e. I = kVn) indicates that the Child-Langmuir law may not be directly employed for the case of DC magnetron sputtering.
Liken the conventional DC magnetron sputtering discharge, a qualitative approach has been adopted for the conventional ICP discharge. In particular, the dynamic processes of E-mode and H-mode productions, and their transitions are presented.
In ICP assisted DC magnetron sputtering, it has been verified that the sputtered yield has been greatly enhanced by the addition of the ICP source. On the other hand, nodosity has been observed to occur in the hysteresis loops for the cathode current vs. RF current; at a fixed cathode voltage. This exhibits multi-stable characteristics of the plasma, which departs from the typical bi-stable states. Besides the above-mentioned, the effects of RF current variation within the range of H-mode discharge, of the plasma state are also investigated; at a fixed cathode voltage. In situ measurements of the emission intensity of the sputtered target species (Ti) vs. the RF current and for the cathode current vs. RF current have been found to be consistent. Both loops evolved into spirals with sub-loops gradually approaching the side of the main loop in the first current decreasing phase. These phenomena displays more complicated non-linear characteristics of the plasma in ICP assisted DC magnetron sputtering and are investigated for the first time. These results challenge the existing theory.
Having observed the hysteresis patterns of the two plasma sources, the influence of plasma non-linearity on the characteristics of thin TIN films is explored. For comparison, two different substrates (i.e. Austenitic stainless steel (304) and Si (100)) have been used during deposition. It has been found that there exists a preferred orientation of the TIN film on stainless steel substrate via multi-adjustment of the RF current while the same cannot be said for the Si (100) substrates. This preliminary result sheds much light to the correlation between the non-linearity of plasma and film characteristics, and is presented for the first time.
Other features of the ICP assisted DC magnetron sputtering and suggestions for further studies are also briefly presented.
The high density ICP assisted DC magnetron sputtering set-up. which has been used in this work, is described in detail. The apparatus may operate in three distinct modes: as a conventional DC magnetron sputtering device, a conventional ICP source and an ICP assisted DC magnetron sputtering device. The discharge behaviours with respect to each of the three different modes are described.
The operating principles of a conventional DC magnetron sputtering discharge have been presented qualitatively. Two distinct discharge modes (i.e. the D-mode and the M-mode), belonging to the DC magnetron sputtering have also been identified. The dynamic mechanism for the mode production and features of the mode transition point are discussed. It is believed that distinction of the two discharge modes have been made and explained for the very first time. Hysteresis loops have also been observed for the cathode current (I) vs. cathode voltage (V). which indicates bi-stability of plasma. In addition, comparisons between experimental data with the typical empirical relationship between I and V (i.e. I = kVn) indicates that the Child-Langmuir law may not be directly employed for the case of DC magnetron sputtering.
Liken the conventional DC magnetron sputtering discharge, a qualitative approach has been adopted for the conventional ICP discharge. In particular, the dynamic processes of E-mode and H-mode productions, and their transitions are presented.
In ICP assisted DC magnetron sputtering, it has been verified that the sputtered yield has been greatly enhanced by the addition of the ICP source. On the other hand, nodosity has been observed to occur in the hysteresis loops for the cathode current vs. RF current; at a fixed cathode voltage. This exhibits multi-stable characteristics of the plasma, which departs from the typical bi-stable states. Besides the above-mentioned, the effects of RF current variation within the range of H-mode discharge, of the plasma state are also investigated; at a fixed cathode voltage. In situ measurements of the emission intensity of the sputtered target species (Ti) vs. the RF current and for the cathode current vs. RF current have been found to be consistent. Both loops evolved into spirals with sub-loops gradually approaching the side of the main loop in the first current decreasing phase. These phenomena displays more complicated non-linear characteristics of the plasma in ICP assisted DC magnetron sputtering and are investigated for the first time. These results challenge the existing theory.
Having observed the hysteresis patterns of the two plasma sources, the influence of plasma non-linearity on the characteristics of thin TIN films is explored. For comparison, two different substrates (i.e. Austenitic stainless steel (304) and Si (100)) have been used during deposition. It has been found that there exists a preferred orientation of the TIN film on stainless steel substrate via multi-adjustment of the RF current while the same cannot be said for the Si (100) substrates. This preliminary result sheds much light to the correlation between the non-linearity of plasma and film characteristics, and is presented for the first time.
Other features of the ICP assisted DC magnetron sputtering and suggestions for further studies are also briefly presented.
Date Issued
2001
Call Number
TK7871.15.F5 Cha
Date Submitted
2001