1. In the manufacture of an integrated circuit including a semiconductor substrate, a method of preparing said semiconductor substrate having a diamond coated trench, the method comprising the steps of: etching a trench in a semiconductor substrate such that said trench has a bottom surface and sidewalls surrounded by a circumferential top surface segment of said semiconductor substrate; uniformly toughening said bottom surface and said sidewalls; prior to roughening at least said bottom surface, masking on said circumferential top surface segment a masking material such that said circumferential top surface segment is prevented from being toughened; and selectively nucleating a diamond layer on said rough bottom surface and on said rough sidewalls inside said trench.