Scanning Techniques There are two main methods of scanning an electron beam across the substrate surface in electron beam lithography. Below is a comparison of the raster scan and the vector scan.
Characteristics of the Raster Scan The chip is broken into stripes of approx. 2^8 pixels The selected strip is written onto the substrate The beam scans over the substrate line by line If the current pixel is to be exposed, the beam is on If the current pixel is not to be exposed, the beam is off The substrate is moved perpendicular to the scan lines by a laser-controlled table	Characteristics of the Vector Scan An area of an individual die is aligned under the electron beam The beam is deflected so as to draw out the features in that area of the chip The chip is completed either by a step-and-repeat method, or by continually moving the substrate The alignment of features in adjacent scanning area is important. A measure of misalignment is the butting error.