Effect of Arsenic on Extended Defect Evolution in Silicon
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EFFECT OF ARSENIC ON EXTENDED DEFECT EVOLUTION IN SILICON R. Brindos, K. S. Jones and M. E. Law SWAMP Center, Univ. of Florida, Gainesville, FL 32611 Abstract The effect of arsenic on {311} defect formation was determined for temperatures ranging from 700°C to 800°C. Arsenic well structures were formed at arsenic concentrations of 3x1017, 3x1018, and 3x1019 cm-3. A 40 keV 1x1014 cm-2 silicon implant, that is known to form {311} defects, was then incorporated into the structures. Extended defect evolution and dissolution was then studied after furnace annealing at 700°C, 750°C and 800°C for various times. It was determined that arsenic has a strong affect on the nucleation of extended defects. However, once the defects were formed, the dissolution time constant was the same for all concentrations considered. The activation energy for defect dissolution was found to be 3.4eV and was also independent of arsenic concentration. Using a newly developed {311} model in the FLOOPS process simulation software, the effect of the arsenic on {311} formation and dissolution was simulated. It was found that by using a pair model with an arsenic-interstitial binding energy of 0.95eV, the experimental results were able to be simulated. Introduction As devices continue to be scaled to smaller and smaller dimensions, the dopant diffusion begins to control the depth of the electrical junction. Transient Enhanced Diffusion (TED) adversely affects the diffusion of dopants and becomes an important parameter to consider in the process design of future devices.1 TED from self-implants has been a heavily studied area for many groups and a correlation has been made between TED and extended defect formation and dissolution.1-4 Eaglesham et al.2 has suggested that extended defects serve as storage sites for excess interstitials and that during the dissolution of the defects interstitials are released. Once released, the interstitials are free to interact with any dopant atoms present. Common dopant atoms are known to fully or partially diffuse via interstitials and therefore the release of interstitials propels the enhanced diffusion of the dopant atoms.1 The addition of excess interstitials to regions doped with either boron or phosphorus has been shown to have a measurable influence on the nucleation, growth and dissolution of extended defects.5,6 To understand the influence the dopant has on the defect processes, studies were conducted which examined the interstitial trapping by impurity dopants. Haynes et al.5 executed a study of boron interstitial trapping using boron-doped wells. In their experiment they formed boron well structures of varying concentration and added excess interstitials by way of silicon self-implants. Subsequent anneals were done to nucleate, grow and eventually dissolve {311} defects. It was determined that for boron concentrations above 1x1018 cm-3 the boron traps the interstitials and causes a reduction in the {311} formation. It was also found that once the defects formed the boron concentration did not affect the d
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