Exclusion guard and gas-based substrate protection for chemical vapor deposition apparatus

An apparatus for supporting a substrate in a chemical vapor deposition process chamber, comprising:

• a wafer-supporting body disposed in the process chamber;
• an exclusion body disposed in the chamber in alignment with the support body, the exclusion body including a portion projecting over a frontside peripheral region of the wafer and uniformly spaced from the wafer frontside peripheral region to form a uniformly restrictive passage connecting a first volume of the chamber proximate the wafer frontside deposition surface to a second volume proximate the wafer edge;
• and
• a venting region disposed in the exclusion body uniformly spaced from and encircling the exclusion body projecting portion, the venting region communicating with a source of venting gas for creating a venturi effect to draw the process gas toward the projecting portion during wafer processing;
• wherein the first volume communicates with a source of process gas, and the second volume communicates with a source of deposition control gas.