This invention relates to a vacuum coating system of the in-line load-lock type wherein substrates, such as silicon wafers for example, are transported for positioning within a vacuum chamber in proximity to a vapor source, such as sputtering electrodes or electron-beam evaporators, for coating as required.
The substrates which are first positioned on a carrier support at a loading port outside the vacuum chamber, are transported by the carrier through controlled gated load-locks and buffer zones into the process or coating chamber so as to be properly positioned with respect to, or slowly passed by the coating source. A vacuum coating system of this general type is disclosed in U.S. Pat. No. 3,662,708 granted May 16, 1972 to Robert L. Shrader and assigned to the same assignee as the present invention.
In this type of vacuum coating system, it is commercially advantageous to transport and position the workpieces or substrates without undue loss of production time; that is, it is desirable that the substrate transfer time be as small as possible in relation to the required coating time and that the equipment therefor be simple, positive and reliable. In many prior systems where the carrier is manually transferred from one position to another, or where one or more sets of drive rollers moving at constant speeds are used, or where complicated mechanical positioning means such as pneumatic thrust pistons, cables, linkages, etc. are used, the production process in general has not been satisfactory. This is especially the case where significant maintenance and down-time are encountered in complicated equipment, and where transfer of the substrates between process steps is time-consuming.
The present invention, therefore, is concerned with improved and simplified workpiece transfer equipment for a vacuum processing system of the character described, that readily lends itself to efficient transfer of the workpieces between load-locks, buffer zones, process chamber, etc. throughout the entire vacuum processing system.