I am using e-beam lithography to define gate on Si/SiO2 wafer. I find shadows around the deposited metal after lift off in the SEM images. I use Bilayer of PMMA 950K and PMMA 450K each baked for around 20 minutes. The image is added below.
Ashby., this could be if resist aren't completely removed, try intensive O-plasma treatment. Although this contour appeared only to the right, it can be angle effect if you have deposited two metal layers (e.g. thin adhesion layer first) from the different evaporation boats without wafer position adjustment