Abstract: In a plasma reactor including a vacuum chamber for containing at least a reactant gas at a selected pressure and a semiconductor wafer to be processed, a pair of electrodes for capacitively coupling radio frequency power into the chamber and a radio frequency source having a radio frequency power terminal, a circuit for coupling the radio frequency source to the pair of electrodes includes a coil having plural conductive windings and a pair of terminals bounding plural ones of the windings, the pair of terminals coupled to respective ones of the pair of electrodes, one of the windings connected to the power terminal of the radio frequency source, and a grounded conductive tap contacting the coil and slidable along the plural ones of the windings between the pair of terminals for varying a ratio of power apportioned between the pair of electrodes.

Abstract: This invention relates to coated medicaments and a process for providing spray coated gelatinous coverings for such medicaments. This invention is also directed to novel gelatinous compositions for spray coating tablets, caplets, pellets, granules and the like.

Abstract: A method and apparatus for generating a medium density plasma in a reactive ion etching chamber. A conventional reactive ion etching technique, using multiple electrodes for capacitive coupling of power into the chamber to establish and sustain a plasma, is combined with inductive coupling for plasma enhancement only. A first source of high frequency power is coupled to at least one of the electrodes to generate the plasma under conditions similar to those used in a conventional reactive ion etching system, and a second source of high frequency power is coupled to an inductive coil surrounding the plasma, to enhance the plasma density without adversely affecting wafers being processed in the chamber.

Abstract: A plasma chamber, and a related method for its use, in which the direct current (dc) bias on a wafer-supporting cathode is reduced by including a plasma shield that blocks plasma from reaching a region of the chamber and thereby reduces the effective surface area of a grounded anode electrode. The plasma shield has a number of narrow slits through it, small enough to preclude the passage of plasma through the shield, but large enough to permit pumping of process gases through the shield. The dc bias is further controllable by installing a chamber liner of dielectric or other material to cover a selected portion of the inside walls of the chamber. The liner also facilitates cleaning of the chamber walls to remove deposits resulting from plasma polymerization.

Abstract: A plasma etch reactor and a related method of its operation to provide self-cleaning of its top electrode, which is subject to being coated by polymer deposits during normal operation. In one form of the invention, radio-frequency (rf) power is applied to the top electrode on a continuous basis, but at a much lower power level than that of a primary rf power source used to supply power through a lower electrode, to generate and sustain a plasma in the reactor. The small rf power applied through the top electrode is selected to be of such a level as to remove deposits from the electrode continuously, as they are formed, but without removing any significant amount of electrode material. In another form of the invention, power is applied to the top electrode periodically during cleaning periods and power supply to the lower electrode is suspended during the cleaning periods.

Abstract: Improvements in a wafer support apparatus used for electrostatic clamping of a wafer to the wafer support, and a method of making same, are disclosed wherein a dielectric material, formed on the surface of a wafer support facing the wafer to facilitate the electrostatic clamping, has a protective coating formed over the dielectric material to provide protection to the dielectric material against chemical attack from chemicals used during the processing of the semiconductor wafer. In a preferred embodiment, the protective coating comprises an aluminum compound, such as an oxide of aluminum or aluminum nitride, having a thickness ranging from about 1 micron to about 30 microns, but not exceeding about 50% of the thickness of the dielectric material so as to not interfere with the electrostatic charge used for clamping the wafer to the wafer support.

Abstract: Disclosed is a process for plasma etching a mask patterned dielectric film to form vias on a semiconductor wafer, so that the resulting etched structure is devoid of residues on the walls of the structure. A via is an opening through a dielectric material through which a point of contact of underlying metal with a metal film deposited over the dielectric is made. The underlying metal, when exposed to plasma, has a tendency to sputter onto the vertical wall portions of the contact via structures. The metal-containing sputtered material forms a residue that essentially cannot be removed in the subsequent photoresist stripping process typically used in semiconductor manufacturing. The plasma etch process in accordance with the invention enables removal of the sputtered metal by utilizing with the basic dielectric etch gases a gas that reacts with the metal to form volatile compounds which are readily evacuable.

Abstract: An improved process is described for forming one or more vias through an insulation layer by plasma etching to an underlying metal layer without depositing etch residues, including metal sputtered from the underlying metal layer, onto the sidewalls of the vias, which comprises, in one embodiment, using in the gaseous etchant one or more 3-6 carbon fluorinated hydrocarbons having the formula C.sub.x H.sub.y F.sub.z, wherein x is 3 to 6, y is 0 to 3, and z is 2x-y when the fluorinated hydrocarbon is cyclic and z is 2x-y+2 when the fluorinated hydrocarbon is noncyclic. One or more other fluorine-containing gases may also be used as long as the 3-6 carbon fluorinated hydrocarbons comprise at least 10 volume % of the fluorine-containing gas mixture. The fluorinated hydrocarbon gas or fluorine-containing gas mixture also may be mixed with up to 90 volume % total of one or more inert gases to control the taper of the via walls.

Abstract: In a digital data link system which transmits and receives frequency-shift keyed digital data over mark/space frequency channels, the invention enhances system performance in the presence of noise. The method utilizes two synchronization channels, selecting the better one to synchronize the receiver to the transmitter. The method teaches the accumulation of the results of a plurality of data-state determining measurements and the utilization of the accumulated measurements made during a baud interval to resolve the received mark/space frequency signal into a corresponding mark/space data-state signal. Apparatus to practice the method is described. The apparatus includes a timing recovery circuit for synchronization-channel selection and a digital frequency detector capable of extracting information from a data signal in the presence of noise having the same frequency as the data signal and up to 86.6% of the amplitude of the data signal.