Low-energy plasma-enhanced chemical vapor deposition

The high reactivity of the radicals and the removal of hydrogen from the surface by ion bombardment prevent the typical problems of Si, Ge and SiGe alloys growth by thermal chemical vapor deposition (CVD), which are Thanks to this effects the growth rate in a LEPECVD reactor depends only on the plasma parameters and the gas fluxes, and it is possible to obtain epitaxial deposition at much lower temperatures compared to a standard CVD tool.

The potential of the wafer stage can be controlled by an external power supply, influencing the amount and the energy of radicals impinging on the surface, and is typically kept at 10-15 V with respect to the chamber walls.

Additional coils ("wobblers") are placed around the chamber, with their axis perpendicular to the magnetic field, to continuously sweep the plasma over the substrate, improving the homogeneity of the deposited film.

[1] The capability of LEPECVD to grow both very sharp quantum wells on thick buffers in the same deposition step has also been employed to realize high mobility strained Ge channels.

[3] Another promising application of the LEPECVD technique is the possibility of growing high aspect ratio, self-assembled silicon and germanium microcrystals on deeply patterned Si substrates.