Generation of uniform large-area very high frequency plasmas by launching two specific standing waves simultaneously

Abstract

With the characteristics of higher electron density and lower ion bombardment energy, large-area VHF (very high frequency) plasma enhanced chemical vapor deposition has become an essential manufacturing equipment to improve the production throughput and efficiency of thin film silicon solar cell. However, the combination of high frequency and large electrodes leads to the so-called standing wave effect causing a serious problem for the deposition uniformity of silicon thin film. In order to address this issue, a technique based on the idea of simultaneously launching two standing waves that possess similar amplitudes and are out of phase by 90° in time and space is proposed in this study. A linear plasma reactor with discharge length of 54 cm is tested with two different frequencies including 60 and 80 MHz. The experimental results show that the proposed technique could effectively improve the non-uniformity of VHF plasmas from >±60% when only one standing wave is applied to <±10% once two specific standing waves are launched at the same time. Moreover, in terms of the reactor configuration adopted in this study, in which the standing wave effect along the much shorter dimension can be ignored, the proposed technique is applicable to different frequencies without the need to alter the number and arrangement of power feeding points.

Crystallinity And Morphology Of Silicon Carbide Thin Films Deposited Using Very High Frequency Plasma Enchanced Chemical Vapor Deposition

“…Thus, the higher growth rate with dense film were produced. In addition, most researcher got that the higher frequency would also result in a reduced sheath thickness and a lower voltage potential across the electrodes that makes the deposition growth of films greater and provide better uniformity of films thickness [8]. Thus, the roughness of the SiC thin films is 5.43nm, 11.94nm and 13.91nm obtained at 100MHz, 160MHz and 200MHz respectively which is greatly become more compact as the frequency increased.…”

Modeling of low pressure plasma sources for microelectronics fabrication

“…In solar and display applications, large area PECVD chambers are often rectangular to accommodate rectangular substrates. These PECVD and PEALD plasmas sources have been extended to the VHF range in recent years [25].…”

How to address the issue of uniformity in large area capacitively coupled plasmas? A modeling investigation

“…Both experimental [19][20][21] and numerical [22][23][24] research indicated that by varying the phase difference between the two sources applied to the top and bottom electrodes, i.e., the so-called phase-shift control, the plasma currents redistributed and therefore the plasma uniformity could be optimized. Moreover, Chen et al pointed out that the plasma nonuniformity decreased significantly by launching a traveling wave, which was generated by the superposition of two standing waves with the same amplitude and out of phase by 90 • in space and time [25][26][27]. Bera et al introduced the electric potential and the magnetic vector potential to calculate the ES field and the EM field, respectively, and they presented different electron density distributions with various combinations of powers at 60 MHz and 180 MHz [28].…”