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Current R&D: CVD Growth by Toroidal Plasma

A toroidal plasma is a plasma discharge configured such that the plasma operates in a closed loop. There are no physical electrodes in the discharge chamber, which means that very high electrical currents can be obtained in the discharge, without corresponding problems with electrode erosion. Toroidal discharges have been used for many years in the semiconductor industry, for generation of large fluxes of atomic species such as O, N, H and F, in applications including CVD chamber clean, photoresist removal, and surface oxide removal. 

We have adapted the toroidal plasma technique to growth of high-quality CVD diamond material.  One of the early challenges we needed to overcome was the extremely high-power density on our process chamber inner walls. We employed sophisticated finite element modeling in order to design a process chamber and sample holder able to manage these conditions. Here is an example of thermal modeling that we have done:

The growth rates that we have achieved are extremely high – over 200 microns per hour, as can be seen here:

The very high growth rates are due to three factors:

  • The plasma is confined to a small volume
  • The power density in the plasma is very high, over 1000 W /cm2
  • The sample is very close to the plasma center – just a few millimeters

Multiple analytical techniques are used to characterize the quality of the CVD diamond material. These include:

  • spectrophotometry
  • Raman spectroscopy
  • X-ray diffraction
  • photoluminescence

Some of the results are shown here:

Torroidal-Related Publications, Presentations and Patents

Toroidal Plasma Enhanced CVD of Diamond Films

John Zvanya, William Holber, Christopher Cullen Thomas Morris, Andrew Basnett, Robert Basnett, Jeffrey Hettinger and Robert R. Krchnavek

J. Vac. Sci. Technol. A 32(5), Sept/Oct. 2014

Presentation: Toroidal Deposition of Diamond

NDNC 2015

Presenters include: William Holber (Plasmability), Robert Basnett (Plasmability), Andrew Basnett (Plasmability), and Robert Krchnavek (Rowan University).

NDNC 2018 Program and Index

Includes description of presentation by Amanda Charris, William Holber, Robert Basnett, Andrew Basnett, Doug Hansel and Adam Brown; Plasmability, LLC, Austin, Texas, United States.

Europe MRS Fall Meeting 2018

2018 NDNC 2019 Program and Speakers.

Patents Related to Toroidal Plasma Deposition of Diamond

U.S. 10,704,161

Toroidal plasma processing apparatus with a shaped workpiece holder, July 7, 2020

U.S. 10,443,150

Toroidal plasma processing apparatus with a shaped workpiece holder, October 15, 2019

U.S. 9,909,215

Method of CVD plasma processing with a toroidal plasma processing apparatus, March 6, 2018