The CCP type has a structure where plasma is formed at the top and only radicals come down through an ion filter.
I'm curious that even if ions come down, there is no bias applied to the susceptor, because then there is no force to accelerate the ions.
Even if the ion filter doesn't work, wouldn't it cause damage?
Thank you
In a capacitively coupled plasma (CCP) system, plasma formation at the top and the subsequent movement of radicals through an ion filter is a characteristic feature. The ion filter’s role is to selectively allow radicals to pass while filtering out ions, which could potentially interfere with processes such as chemical vapour deposition (CVD) used for materials like carbon nanotubes (CNTs)1.
The concern about ions potentially causing damage if they were to come down without a bias applied to the susceptor is valid. In typical CCP systems, a bias is not just applied, but it plays a crucial role in controlling and accelerating ions towards the surface. This bias is not just important; it's essential.
However, in the scenario where no bias is applied to the susceptor, the ions would lack the force necessary for acceleration. This could result in a lower energy impact on the substrate, which might not be sufficient for specific processes that require higher ion energies. Nonetheless, even without a bias, ions could still reach the substrate due to diffusion or other electric fields in the system3.
If the ion filter fails to function correctly, the potential risk of uncontrolled ion bombardment on the substrate becomes a significant concern. This could lead to severe damage or undesired modifications of the material properties, which must be avoided at all costs. The extent of the damage would depend on the ion energy, flux, and the nature of the substrate material. It is therefore crucial1.
In summary, while the absence of a bias on the susceptor in a CCP system may not necessarily cause immediate damage, it could compromise the control over the ion energy and, consequently, the quality of the processed material. Proper functioning of the ion filter is critical to prevent potential damage from uncontrolled ion bombardment.
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