Methods for exposing a desired shape in an area on a surface using a charged particle beam system include determining a local pattern density for the area of the desired shape based on an original set of exposure information. A backscatter for a sub area is calculated, based on the original set of exposure information. Dosage for at least one pixel in a plurality of pixels in the sub area is increased, in a location where the backscatter of the sub area is below a pre-determined threshold, thereby increasing the backscatter of the sub area. A pre-PEC maximum dose is determined for the local pattern density, based on a pre-determined target post-PEC maximum dose. The original set of exposure information is modified with the pre-PEC maximum dose and the increased dosage of the at least one pixel in the sub area to create a modified set of exposure information.