Patent ID: 8338063

Claim:
A method for use in photolithography performed by an exposure apparatus having a slit, the method comprising: coating a substrate with a layer of photoresist; exposing the photoresist layer over each of a plurality of shots sequentially by irradiating the photoresist layer to exposure light directed through the slit of the exposure apparatus, wherein the intensity of the exposure light irradiating each shot is different; developing the exposed photoresist layer to form a sample photoresist layer; analyzing an image of the sample photoresist layer to determine the intensity of a color of each shot; selecting one of the shots from among a group of the shots on the developed sample photoresist layer, wherein the group of shots is a series of sequentially exposed ones of the shots over which the intensity of the colors changes from shot to shot; determining the intensity of the color of each pixel of an array of rows and columns of pixels within an image of the selected shot, wherein each of the rows of pixels extend in a direction corresponding to a lengthwise direction of the slit; averaging values of the intensities of the color of the pixels for each column of the pixels within the selected shot, and assigning the average value for each column to a position that the column occupies along the rows of the pixels; for each assigned average value of the intensity of the color of the pixels of a respective column of the pixels, correlating the color intensity value with a value of the intensity of the exposure light to obtain a series of values of the intensity of the exposure light representative of the distribution of energy levels of the exposure light along the length of the slit during the process of exposing the layer of photoresist; and changing the slit of the exposure apparatus based on the distribution of energy levels of the exposure light determined from the correlation between the color intensity values and the values of the intensity of the exposure light.