A trial to quantify and classify process non-uniformity into baking and development

摘要

It is indispensable to have a simple and convenient technique to quantify process non-uniformity and classify it into each step of the mask-making process in order to draw an error budget of CD non-uniformity and to take measures for the coming years. The final reticle CD uniformity provides us with quantitative information but impracticable one to classify it into each step of the process. We then contrived a new method for quantifying process non-uniformity and classifying it into each of baking and development with properly utilizing resist behaviors in the process. We firstly tried to quantify baking non-uniformity by utilizing a resist behavior in coating film contraction to baking temperature. A resist film can be used just like a thermo-measuring device if the film contraction occurs significantly enough and linearly to baking temperature. Most resist show a linear correlation between film thickness and baking temperature. And, an inclination and a y-intercept of the approximate linear function depend on baking tool configuration, substrate, resist and its coating thickness. And, the thicker coating, the larger inclination in the minus quantity. Besides, the slope and the y-intercept depend on film thickness before baking, which can be described by another approximate linear function respectively. Therefore, it is possible to estimate a baking temperature applied, in a set value of temperature on a baking tool examined, by measuring the resist coating film thickness before and after the baking. Furthermore, it is possible to estimate baking non-uniformity, described by the set value of temperature on a tool examined, when the measurement is done on each individual point in an array or in an arbitrary critical area on a plate, with employing a resist which has a significantly enough and linear film contraction to baking temperature. FEN270 for instance shows the inclination of over -1.5 nm per 1deg.C. at around 1000nm thick and above, which enables for us to obtain a suitable accuracy and resolution for the estimation.