Electron beam lithography process

In a process of forming a patterned resist image on a substrate, the process including the steps of:

• forming a layer of resist material, which becomes more soluble in a developer when struck by electrons, on the substrate;
• exposing the layer to a scanning beam of electrons to form a pattern of exposed shapes, the beam having a fixed spot size which is moved step-wise on a two dimensional grid whose grid size is a fraction of the spot size;
• and
• developing a patterned resist image by removing the resist material in the exposed shapes with a developer;
• the improvement which comprises forming first exposed shapes in the layer with a series of a non-overlapping exposures each at a first exposure dosage and forming a second exposed shape in the layer with multiple overlapping exposures, with each overlapping exposure being at a dosage less than said first exposure dosage;
• and then developing the patterned resist layer with a developer to completely remove the resist in the first exposed shapes down to the substrate while at the same time removing only a portion of the resist in the second exposed shape down to the substrate.