Wafer coating system

Abstract

Semiconductor wafers having patterns of steps and grooves defining microcircuit elements thereon are coated with metallic film by supporting the wafers individually adjacent a respective ring-shaped sputtering source in stationary relationship thereto. Within a short deposition time of approximately one minute, good uniformity of deposition across the main wafer plane is obtained by maintaining source-to-wafer spacing less than the diameter of the source, and an effective source diameter (D.sub.s) larger than the diameter of wafer (D.sub.w) with the coating being performed within an argon environment of 2 to 20 microns pressure. Good step coverage across all surfaces of steps and grooves is likewise obtained, and is further enhanced by confining the source-to-wafer spacing ranges to certain values within about 0.4 D.sub.s to 0.9 D.sub.s and the wafer diameter to certain values up to about 0.7 D.sub.s. To effectuate such individual wafer processing on a continuous basis and preserve the evacuated argon environment, a vacuum chamber sputter coating apparatus is provided which has a number of work stations therein, at least one of which includes said ring-shaped sputtering source. Also included is a load lock; and an intermittently rotating vertical plate-like wafer carrier means therewithin positioned closely adjacent the chamber entrance, and carrying wafers in turn from the load lock to the work stations. The carrier includes apertures each accepting a wafer therewithin in an upright position, with the wafers edgewise resiliently supported by clip means, without the use of any externally-originating supports such as platens. A closure member within the chamber is movable against the plate opposite the chamber entrance to close off the plate aperture from the chamber environment during loading and unloading of a wafer, and a door is provided to close the chamber opening and thus complete a thin low-volume load lock. The door is also provided with vacuum means to grasp a wafer presented vertically by a blade-like elevator which cooperates with a cassette and conveyor moving the cassette along a horizontal path below the chamber entrance. The cassette holds wafers vertically, and the blade passes therethrough to lift individual wafers edgewise to the door vacuum means. Closure of the door inserts the wafer into the clip means within the carrier and chamber, and the reverse operation extracts a wafer previously coated at a sputtering work station. Both surfaces of the wafer can be accessed by processing equipment, for example, heating or cooling means at some of the work stations. Only a few wafers inside the chamber are at risk at any one time, and introduction of contaminants, debris, as well as disturbances to the chamber environment are minimized.