Plasma Processing

Most Recent Patents

Method for Improving Plasma Processes by Controlling a Voltage Waveform

A UW-Madison researcher has now developed an improved algorithm that significantly enhances plasma etching through an automated process that modulates a voltage waveform applied to the substrate material until the optimal bombarding ion energy distribution is achieved.

To control the ion energy distribution, the inventor used a programmable waveform generator in combination with a power amplifier to tailor the waveform shape of the radio frequency (RF) bias voltage applied to the substrate during processing. The technique works by introducing a periodic bias voltage to the semiconductor substrate through a direct current (DC) blocking capacitor, which has a waveform comprised of voltage pulse peaks.

A fast Fourier Transform (FFT) of the substrate waveform is compared, one frequency at a time, with the FFT of a desired “target” waveform, to determine adjustments needed at the waveform generator. An inverse FFT then yields the waveform generator output. It is repeated until the substrate waveform converges to the targeted shape, providing a quick systematic method for producing an arbitrary distribution of ion energies at the substrate.

This iterative procedure is vital to making the system, previously done manually, fully automated. It has been verified for several target waveform shapes.

Plasma-Enhanced Functionalization of Substrate Surfaces with Quaternary Ammonium and Phosphonium Groups

UW-Madison reseachers have developed a non-equilibrium, radio frequency plasma-enhanced approach for efficiently implanting antimicrobial functional groups on surfaces. A plasma treatment creates active sites directly on a substrate surface. Linker molecules are bound to the active sites, and quaternary ammonium precursor molecules are reacted with the linker molecules to result in anti-bacterial functional groups bound to the substrate surface. Alternatively, the active sites are exposed to a plasma of polymer precursor molecules, which are in turn reacted with quaternary phosphonium precursor molecules to generate the bactericidal groups. A third embodiment involves reacting polymer precursor molecules with linker molecules bound to the active sites. The polymers contain amine groups, which are converted to antimicrobial quarternary ammonium groups via alkylation.

Simplified Apparatus and Methods for Producing Nanoparticles in a Dense Fluid Medium

UW-Madison resarchers have now developed a simplified design for the dense medium plasma (DMP) reactor, along with a method of using it to produce silicon, carbon and other nanoparticles. The improved DMP reactor includes a plasma reaction vessel with an internal reaction chamber into which a dense fluid medium may be introduced. An electrode assembly, consisting of two electrodes with opposing ring-shaped electrode discharge faces, is submerged in the fluid within the chamber. When an electric potential is applied, a plasma discharge zone forms between the opposing electrode discharge faces. A gas inlet port releases a cavitation gas into a zone between the electrodes, creating bubbles in the dense medium plasma. The bubbles replace the rotating electrode used to stir the fluid in the original reactor design. They promote the efficient, plasma-induced production of nanoparticles from precursors in the dense fluid medium.