Cross-mounted mask changer with thickness monitoring

Claim 1

In combination, a mask changer for sequential deposition of vapor in a vacuum on a single substrate through a plurality of masks; said mask changer being positioned in an evacuated glass cross having right and left, top and bottom ports, a frame and means for providing a vacuum seal beneath said frame and each port of said cross; said mask changer comprising a carriage having linear movement within said vacuum; a substrate holder assembly mounted for vertical movement and limited lateral movement with reference to said carriage; mask frames mounted on said carriage in linear relationship with reference to each other and to said substrate holder; means for raising and lowering said substrate holder for allowing movement of said carriage for placement of individual mask frames beneath said substrate holder; cooperating means on said substrate holder and each of said masking frames for precision engagement of said substrate holder with each of said masking frames; and a wide range thickness monitoring device positioned on said mask changer for monitoring a successive plurality of vapor depositions of widely varying thickness; said monitoring device comprising at least one vapor source for deposit of vapor onto said substrate; a crystal located in the vapor path to receive vapor from the vapor source each time a deposition is made on the substrate; a laterally movable shield interposed between the vapor source and said crystal, said shield having openings therein in alignment with said crystal at each mask position; each of the openings in said shield being of a preselected size according to the thickness required for the vapor deposition at the particular mask position, whereby the oscillation rate of said crystal is decreased in substantially linear proportion to the increase in its mass as each successive deposition is made and the thickness of each deposition on the substrate is thereby indicated throughout a wide range of thickness.