Vapor drain system

A thermo-buoyant vapor drain system comprising:

• an enclosure for holding vapor sensitive product between steps of its manufacture;
• means not part of the vapor sensitive product for non-uniformly heating and cooling air within said enclosure for causing thermo-buoyant convection of vapor within said enclosure, and
• vapor removal element means disposed in said enclosure for removing vapor from said circulating air.

In a sealed enclosure for retaining a semi-conductor wafer with a sensitive face between manufacturing steps for said wafer, the improvement comprising:

• a vapor removal element with a conductance which exceeds the sum of the conductances from all sources of contaminating vapor in the enclosure including those of the wafer itself, said vapor removal element being held in close juxta-position to the sensitive face of the wafer so as to capture vapor emissions from said face to thereby protect the sensitive face of the wafer from formation of contaminating films thereon.

In a sealed enclosure with a rack mounted therein for holding wafers with a sensitive face in a stack with their faces in spaced relationship to each other, the improvement comprising:

• vapor removal elements in the spaces between the wafers facing the sensitive face of the wafers to inhibit self-contamination of the sensitive face of the wafers by outgassing of sources on the wafers.