Effects of frequency on the two-dimensional structure of capacitively coupled plasma in Ar

Abstract

A time-modulated and time-averaged two-dimensional (2D) profile of the net excitation rate of Ar(3p5) and Ar+(4p4D7/2) was observed in capacitively coupled plasma (CCP) in Ar as a function of the driving frequency (1–100 MHz) through the use of 2D-t optical emission spectroscopy (OES). A significant improvement in the detection efficiency was achieved for the time-resolved OES. Results are presented for the basic characteristics of 2D and 2D-t profiles of the net excitation rate in Ar from 1 to 100 MHz at 1.0 Torr. For comparison, 2D profiles in CCP between high frequency (13.56 MHz) and very high frequency (100 MHz) at 0.1 Torr and 25 mTorr under the same power dissipation are discussed. The advantages of VHF operation are described and discussed based on the radial uniformity and high density in CCP at low pressure. The appearance of a local emission peak at the edge of the rf electrode is observed in CCP, which is caused by changes in the sustaining mechanism due to increases in the driving frequency.

Comparison of etching characteristics of SiO2 with ArF photoresist in C4F6 and C4F8 based dual-frequency superimposed capacitively coupled plasmas

“…The [F]/[Ar] optical emission intensity ratio did not vary significantly with f HF in the C 4 F 6 based plasmas. The [F]/[Ar] emission intensity ratio in the C 4 F 8 based plasma showed a higher value for f HF (27) than for the f HF (13.56) and f HF (60) cases.…”

“…6b. In the C 4 F 8 based plasmas, therefore, the PR etch rate was significantly higher for the f HF (60) plasma than for the f HF (13.56) and f HF (27) cases. The very high ArF PR etch rate in the C 4 F 6 plasma etching is probably related to the formation of a much higher density of F radicals compared to the C 4 F 8 case, as shown in Fig.…”

“…The oxide etch rate is higher in the C 4 F 8 based plasmas than in the C 4 F 6 based plasmas, while the ArF PR etch rate was also too fast to measure in the C 4 F 6 based plasmas. For the f HF (13.56) and f HF (27) cases in the C 4 F 8 based plasmas, the oxide etch rates slightly decreased with increasing O 2 flow rate, whereas the PR etch rates slightly increased. For the f HF of 60 MHz, the oxide and PR etch rates increased with increasing O 2 flow rate in the C 4 F 8 based plasmas.…”

“…In the case of a 2f-CCP etcher, high-frequency (HF) powers are used to enhance the plasma density and low-frequency (LF) power is used to control the ion bombardment energy to the wafer. The two main characteristics of recent commercial 2f-CCP etchers are the use of very-highfrequency (VHF) sources above 27 density plasma, as well as the superimposition of the LF and HF power sources on one electrode in order to simplify the system design [2][3][4][5][6][8][9][10][11][12][13][14][15].…”

“…The use of VHF source frequencies ranging from 27 MHz to 100 MHz for plasma generation is known to be very effective in increasing the plasma density at reduced pressure, due to the resultant effective electron heating [8,19,25,27,[30][31][32][33][34][35]. Moreover, in the case where an f LF of less than 2-4 MHz is used, the use of a higher f HF in the generation of the plasma is advantageous in achieving the functional separation of the HF and LF sources, i.e.…”