System for processing semiconductor wafers producing a downward laminar flow of clean air in front of baking units

Abstract

A photo process system for semiconductor wafers prevents air from flowing across the top of a baking region to produce a stable downward laminar air flow in front of baking units disposed at several levels in the baking region. The baking region is located on one side of a housing, and a coating unit for coating a wafer with a photoresist is located on the other side of the housing. The housing has a clean air entrance and air filters at an upper portion thereof, and a clean air discharge opening at the very bottom thereof. An air flow containment dam prevents clean air entering the housing from flowing horizontally at the top of the baking region. Such a horizontal flow of air would otherwise produce turbulence severely affecting the ability of the air to flow downward across the front of the baking units and toward the discharge opening as a laminar air flow. The laminar air flow hardly passes into the baking units and thus, hardly induces temperature variations in the coated wafers that are being baked. Accordingly, the thickness of the photoresist film on the wafer becomes highly uniform, as does the critical dimension of a pattern produced from the film. Also, dust or ionic contaminants are directly discharged through the discharge opening at the bottom of the housing by the downward laminar flow of clean air. The wafers within the baking units are prevented from being contaminated, thereby enhancing the yield of the semiconductor products.