Abstract: An apparatus and method for drying a microelectronic structure on wafer substrate using supercritical phase gas techniques and a unique pressure vessel locking mechanism. There is lid and a base with an open cavity to contain at least one microelectronic structure on wafer substrate. Clamping the lid to the base uses locking clamp rings with open jaws large to partially enclose the edge of the vessel. The clamp rings are supported symmetrically about the sides of the vessel. The rings are adjusted between an open position where the rings are clear of the vessel and a locking position where the jaws partially enclose the vessel. The jaws and the vessel share a tapered cam plate and roller system configured to bring the rings into vertically compressive locking engagement on the pressure vessel when the rings are moved into locking position. Mechanical interlocks provide security against back pressure opening the rings.