Tegal Corporation

Pavel N Laptev

Valery V Felmetsger

First and second electrodes at opposite ends and magnets between the electrodes define an enclosure. Inert gas (e.g. argon) molecules pass into the enclosure through an opening near the first electrode and from the enclosure through an opening near the second electrode. A ring near the first electrode, a plate near the second electrode and the magnets are at a reference potential (e.g. ground). The first electrode is biased at a high voltage by a high alternating voltage to produce a high intensity negative electrical field. The second electrode is biased at a low negative voltage by a low alternating voltage to produce a low intensity negative electrical field. Electrons movable in a helical path in the enclosure near the first electrode ionize inert gas molecules. A wafer having a floating potential and an insulating layer is closely spaced from the second electrode. The electrode and the wafer define plates of a first capacitor having a dielectric formed by inert gas molecules and ions between the plates to provide a high impedance. The wafer and the inert gas ions in the enclosure define opposite plates of a second capacitor, in series with the first capacitor, having the insulating layer as the dielectric to define a low impedance. The first capacitor accordingly controls and limits the speed at which the gas ions move to the insulating layer surface to etch this surface. The resultant etch, only a relatively few &#x212b;ngstroms, of the insulating layer is smooth, uniform and accurate even in sockets as for vias.

System for, and method of, etching a surface on a wafer

First and second electrodes and magnets between the electrodes define an enclosure. The first electrode is biased at a high voltage to produce a high intensity electrical field. The second electrode is biased at a low negative voltage by a low alternating voltage to produce a low intensity electrical field. Electrons movable in a helical path in the enclosure near the first electrode ionize inert gas molecules in the enclosure. A wafer having a floating potential and an insulating layer is closely spaced from the second electrode. The second electrode and the wafer define plates of a first capacitor having a high impedance. The wafer and the inert gas ions in the enclosure define opposite plates of a second capacitor. The first capacitor accordingly controls and limits the speed at which the gas ions move to the insulating layer surface to etch this surface. The resultant etch, only a relatively few angstroms, of the insulating layer is smooth, uniform and accurate.

An asymmetric alternating voltage (preferably 40 KHz) is provided between a pair of targets having a coaxial (preferably frusto-conical) relationship to (1) deposit the material in a uniform thickness on the substrate surface (2) eliminate dielectric material from the surfaces of the targets and other components (3) provide a single ignition of the targets and eliminate target ignitions thereafter and (4) reduce the substrate temperature by using low energy ('cold') electrons from a plasma discharge to produce a low energy current. The asymmetry may result from amplitude differences between the voltage in alternate half cycles and the voltage in the other half cycles. A second alternating voltage (preferably radio frequency) modulates the asymmetric alternating voltage to provide the smooth plasma ignition. The different voltage amplitudes applied to each of the targets are also instrumental in providing for a substantially constant deposition thickness at the different positions on the surface of the substrate.

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Santa Barbara, CA, United States of America

Pavel N Laptev