Denuded zone formation by conventional and rapid thermal anneals

Oxygen outdiffusion by conventional annealing results in well defined denuded zones and the dissolution of grown-in oxide precipitate nuclei in the region near the surface. During a rapid thermal anneal (RTA) the grown-in oxide precipitate nuclei shrink and due to vacancy outdiffusion during cooling the subsequent growth of the precipitate nuclei is suppressed in the region near the surface. However, potential defects still exist in the region near the surface which can grow during ramping with 1 K min−1 starting from 500°C. A dissolution of grown-in oxide precipitate nuclei in the region near the surface seems only possible by RTA in argon/hydrogen atmosphere. The denuded zone defect density is much lower after RTA than after conventional annealing for oxygen outdiffusion, while the depth profile of the defect density is less steep. The use of the above mentioned conclusions for ‘ramp engineering’ in device processing allows the creation of excellent denuded zones during a device process itself without influencing the device characteristics.