Method and apparatus for producing variable spatial frequency control in plasma assisted chemical etching

An rf head for a plasma assisted chemical etching reactor, said rf head comprising:

• a plurality of dielectric insulators, wherein each dielectric insulator has a cavity therein, and wherein each cavity occupies a different volume;
• a plurality of electrodes, wherein an electrode is positioned within each cavity;
• a plurality of process gas feed tubes, wherein each process gas feed tube is connected between a supply of process gas and one of the plurality of cavities;
• and
• a plurality of rf power conductors, wherein each conductor is connected between a supply of rf power and an electrode positioned within a cavity.

A material removal tool for performing plasma assisted chemical etching reactions on the surface of a substrate comprising a reactor having:

• a housing;
• a first dielectric insulator positioned within the housing having a plurality of cavities for performing a local plasma etching reaction about a localized region of a substrate, and wherein each cavity occupies a different volume within the insulator.
• means for selectively supplying each cavity with a flow of process gas;
• means for selectively providing the process gas within each cavity with rf power so as to generate a plasma therein;
• a second dielectric insulator positioned within the housing and around the first dielectric insulator, said second dielectric insulator extending outward from the first dielectric insulator so as to insulate conductive and proximate surfaces, and thereby facilitating extinction of any plasma outside each cavity;
• means for supporting the substrate;
• and
• means for adjusting the position of each cavity with respect to said substrate surface.

A material removal tool for performing confined plasma assisted chemical etching reactions on the surface of a substrate comprising a reactor having:

• a first dielectric insulator positioned within the housing and wherein said insulator has plurality of plasma chambers for performing a local plasma etching reaction about a localized region of a substrate;
• means for selectively supplying a plasma chamber of said plurality with a flow of process gas including a gas diffuser/electrode;
• means for selectively providing the process gas within a selected plasma chamber with rf power so as to generate a plasma therein, and wherein said means includes a first electrode positioned within each plasma chamber, an electrically conductive rf gas diffuser/electrode, and a second electrode positioned outside the plasma chamber so that the substrate is positioned between the first and second electrodes so as to complete an electrical circuit for supplying rf power to the process gas within the plasma chamber;
• a second dielectric insulator positioned within the housing and around the first dielectric insulator, said second dielectric insulator extending outward from the first dielectric insulator so as to insulate conductive and proximate surfaces, and thereby facilitating extinction of any plasma outside the selected plasma chamber, and extending downward toward the substrate surface a distance shorter than the first dielectric insulator so as to allow the first dielectric insulator to create a region of high plasma and reactive flow impedance circumferentially adjacent to a site where plasma etching is occurring so that plasma outside the region is extinguished;
• means for supporting the substrate;
• and
• an X-Y positioning table means for adjusting the position of said substrate surface with respect to the selected plasma chamber in an orthogonal direction.

A method for local precision figuring, flattening or smoothing of a substrate or film with a plasma assisted chemical etching apparatus having a plurality of plasma chambers comprising the steps of:

• mounting an etchable substrate surface to an electrode;
• selecting a plasma chamber for performing plasma assisted chemical etching;
• positioning said preselected plasma chamber over a spot on the surface of the substrate, the precise position of the chamber dictated by the etching profile desired;
• feeding a process gas stream into a feed inlet of an rf driven gas diffuser/electrode within said preselected plasma chamber;
• applying rf power to an electrode within said preselected the plasma chamber to create an rf electric field within the preselected plasma chamber for decomposing the process gas into a plasma;
• and
• controlling the area of etching and the profile of etching by relative movement between the substrate and said preselected plasma chamber.