A Comparison of Different Techniques for the Rapid Thermal Annealing of Ion Implants in Silicon
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A COMPARISON OF DIFFERENT TECHNIQUES FOR THE RAPID THERMAL ANNEALING OF ION IMPLANTS IN SILICON D.J.WOUTERS, J.VANHELLEMONT, D.AVAU AND H.E.MAES Interuniversitair Micro-Electronica Centrum vzw, Kapeldreef 75, B-3030 Heverlee, Belgium
ABSTRACT In this paper, a comparative study is presented of different techniques used for the annealing of arsenic ion implants in silicon. The used techniques are : lamp annealing using a bank of tungsten-halogen lamps, CW laser annealing and conventional furnace annealing. The annealing quality of the implanted layers is evaluated in terms of dopant activation, dopant diffusion and final extended defect states. The furnace annealing combines a good electrical dopant activation with nearly complete annihilation of the a/c dislocation loops, but substantial diffusion of the dopant profile is measured. Laser annealing gives good electrical activation with very low diffusion, but fails in removing end-of-range extended defects. Furthermore, latent electrical active defects of a donor-type are created. The tungsten halogen lamp annealing gives comparable activation and the diffusion is still lower than can be resolved by SIMS measurements, while growth and annihilation of the a/c dislocation loops is present but not yet completed. These experiments are in agreement with theoretical comparison of the different annealing techniques based on the effective (T,t) coordinates of each technique, which favours RTA processes in the high temperature - "seconds" -time range.
INTRODUCTION Rapid Thermal Annealing of ion implants in silicon is commonly characterized by a good electrical activation with a very low dopant diffusion, due to the short annealing times. The use of simple annealing hardware (high intensity lamps based systems) and the high throughput has made it into a popular technique in silicon processing. The laser annealing process has the disadvantages of a very low throughput and complicated system hardware, although it has the potential of a much better profile control which might be of importance for smaller device tolerances. The importance of final extended defects states in rapid thermal annealed ion-implanted silicon has become a point of interest [1,2] , as mininal dopant diffusion is not always found to be consistent with complete defect annihilation. In this paper, a more complete comparison of a rapid thermal annealing technique with the laser annealing technique and conventional furnace annealing is presented, based not only on activation and diffusion but also on final defect states.
EXPERIMENTAL CONDITIONS Arsenic ion-implantation (1. 1015c1-2,180 keV,7' tilt through 50 mn Si0 2 ) was performed in 10 cm (100) p-type 50cm substrates . For the annealing of the implanted layers, three different annealing techniques are used (1) Furnace annealing (FA) : 30 nin at 950'C in N 2 ambient (2) Rapid thermal annealing using Tungsten Halogen Lamps (THL) : 15 sec at constant full power condition [31 (3) Laser annealing (LA) with a CW Argon-ion laser system. The optimal laser power w
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