One of the methods to grow nanoscale three-dimensional (3D) Au patterns is to perform local electron-beam-induced deposition (EBID) using the Me2Au(acac) precursor inside the chamber of a scanning electron microscope (SEM). However, due to the organometallic nature of the chemical, the concentration of the metallic constituent in the as-deposited structure is dramatically low, at around 10 at. % of Au. Ex-situ post-annealing of Me2Au(acac) EBIDs is a very promising purification approach, resulting in an Au content of > 92 at. % after annealing at 600 °C. However, in most of the cases it also distorts the geometrical shape of the heat-treated structure, preserving of which is essential for the application. In this paper we present a systematic study of the dependence between the annealing parameters and resulting purity in combination with the shape of the Au structure. Optimized heat treatment conditions for the creation of well-purified high aspect ratio Au pillar array are presented; and for planar continuous structures, the importance of the parameter height to area ratio is identified.