Abstract: A method for determining the centroid of a wafer target. In one embodiment, the method comprises a series of steps in a stepper, starting with the step of receiving a wafer, having a target set formed therein. Next, a signal is passed over the target set and over a material separating target shapes in the target set. Then a return signal is reflected, and received, from the surface of the target shapes and the material separating them. A location of at least one maxima point of the return signal is identified. Finally, a centroid is determined as the median of the locations of at least one maxima point.

Abstract: A method for determining the centroid of a wafer target. In one embodiment, the method comprises a series of steps in a stepper, starting with the step of receiving a wafer, having a target set formed therein. Next, a signal is passed over the target set and over a material separating target shapes in the target set. Then a return signal is reflected, and received, from the surface of the target shapes and the material separating them. A location of at least one maxima point of the return signal is identified. Finally, a centroid is determined as the median of the locations of at least one maxima point.

Abstract: A method for determining the centroid of a wafer target. In one embodiment, the method comprises a series of steps in a stepper, starting with the step of receiving a wafer, having a target set formed therein. Next, a signal is passed over the target set and over a material separating target shapes in the target set. Then a return signal is reflected, and received, from the surface of the target shapes and the material separating them. A location of at least one maxima point of the return signal is identified. Finally, a centroid is determined as the median of the locations of at least one maxima point.

Abstract: A focus evaluation technique for photolithography equipment is disclosed. This technique includes providing a substrate having a photoresist coating for treatment by the equipment. The equipment is activated to focus a first part of a image on a region of the surface and defocus a second part of the image relative to the region. The region is tilted relative to an image plane defined by the equipment. This activation is repeated for each of a number of spaced-apart regions along the surface. The substrate is processed to provide a pattern for each of the regions corresponding to the first and second parts. The equipment is characterized from the pattern for each of the regions. This characterization may result from inspection of the pattern relative to reference marks provided for each region. Focus information for the equipment which accounts for lens heating may be determined from this inspection.