Specific Process Knowledge/Lithography/DUVStepperLithography/Optimization and Simulation: Difference between revisions

However, one of the key issues for lithographic optimization is the definition of metrics needed to classify the process quality. With the help of the Prolith™ software from KLA-Tencor the focus-exposure matrix can be used to determine a process window that leads to a maximized depth of focus for the required specification, as i.e. the desired target CD, the exposure latitude, the resist loss and/or the side-wall angles. Figure 1 () shows the focus-exposure matrix of a pin-hole-array, including the relevant information obtained by a simulation, i.e. the isofocal point, the target CD, the resist bias and the isofocal bias. Secondly, with the help of the gradient-based approach, the gradients of the image that is projected and recorded into the photoresist can be used as a metric for both the achieved image and resist contrast. In Figure 2 the normalized image log-slope (NILS) is defined as the slope of the light intensity at the four different pattern edges for a double pin pattern. For each pattern edge - indicated by stars- an optimum NA or sigma value can be found leading to the larges light intensity slope at the individual edge.

[[image:Focus_Exposure_Matrix.gif|500px]]

[[image:NILS.gif|400px]]