Large area VHF plasma production using a ladder-shaped electrode

Generation of Uniform Large-Area VHF Plasmas by Launching a Traveling Wave

“…The same trends can be observed in the experimental data depicted in Figure b as well. In terms of the main interest of this study, i.e., the deposition of silicon thin films for solar cells by VHF PECVD, it is typically operated in the region where the power density is relatively low and hence the discharge pattern is dominated by the standing wave effect, which, in fact, has been confirmed by numerous studies (the frequency ranges from 40 to 200 MHz in the cited references) . On the other hand, the wavelength in the plasma region is assumed to be 1.6 m (∼53% of the value in vacuum), which is also reasonable based on the reported wavelengths described previously.…”

“…However, the non‐uniform discharge caused by the standing wave effect imposes limitation on achieving uniform thin film deposition in large‐area VHF PECVD. Up to now, several methods have been proposed to resolve the technological bottleneck, including lens‐shaped electrode, ladder‐shaped electrode, or dual comb‐type electrodes with phase modulation, superposition of two standing waves that are alternatively ignited and multiple feeding points . Although all the above‐mentioned methods could significantly improve the uniformity of VHF plasmas, most of them might be limited to a fixed frequency and a specific operation window because they are based on the design concept that the configuration of special shaped electrode or the number and arrangement of feeding points is designed for a given standing wave pattern.…”

Amorphous and Nanocrystalline Silicon Solar Cells and Modules

“…Use of vhf demands special cathode design so that the field distribution is uniform, and innovative antenna array design (Takagi et al, 2006) and multi-ladder power input structures (Mashima et al, 2006) have been proposed. Since many individual cell strips are series interconnected, the cell with the lowest current (smallest thickness) will limit the module performance.…”

Design of Large-Area Surface Wave Plasma Excited by Slotted Waveguide Antennas with Novel Power Divider

“…There has been a great need for meter-scale plasma sources for giant material processing, [1][2][3][4][5][6][7] such as thin-film transistor fabrication or barrier layer deposition for meter-scale liquid crystal displays (LCDs), [1][2][3] and the deposition of silicon thin films for photovoltaic power generation. [4][5][6][7] It is indispensable for the improvement in production efficiency for industrial applications to achieve both the enlargement of the plasma production area with good uniformity and the enhancement of processing speed with better production quality. To meet these requirements, future large-area plasma sources should have a high plasma density with a low plasma potential to suppress ion damage to materials.…”

“…To meet these requirements, future large-area plasma sources should have a high plasma density with a low plasma potential to suppress ion damage to materials. Thus far, large-area capacitively coupled plasmas (CCPs) [5][6][7][8] have been widely used for large-scale plasma processing. However, there is a strong interest in using frequencies higher than the industrial standard 13.56 MHz owing to drawbacks of low plasma densities (<10 16 m À3 ), resulting in a low process throughput.…”