Barometric pressure variations are known to affect the coating process resulting in photo resist film thickness variations in lithography track coat processes. The results of an internal TEL evaluation showed a strong correlation between barometric pressure variations and photo resist film thickness variations (as shown in introduction section). Based on those results, a "Barometric pressure compensation system" was developed to estimate and automatically correct for potential film thickness variations which would otherwise result from barometric pressure variations. An Inline system installed on a photo resist track at IBM was used to gather data for a variety of resist systems. A strong correlation was observed between barometric pressure variations and film thickness variations, and the effectiveness of automatic correction for this effect was demonstrated. In the case of KrF Escap-type resists (Resist A), the film thickness and barometric pressure are expressed in a primary approximate expression; the slope is -0.11nm/hPa, and the correlation coefficient (R2) is 0.93. As for the case of KrF Acetal-type resists (Resist B), the slope is -0.12 nm/hPa, and the correlation coefficient (R2) is 0.89. Through the use of the "Barometric pressure compensation system," photo resist film thickness variations were reduced from 2.7 nm (daily coating processed by the same recipe) to 0.6 nm for Resist A and from 5.0 nm to 1.4 nm for Resist B. The studies conducted showed that the "Barometric pressure compensation system" provides significantly improved photo resist film thickness control during variations in barometric pressure, and demonstrated that the technique can be applied effectively to a variety of photo resist materials.