Phosphorus / Silicon Interstitial Annealing After Ion Implantation
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Phosphorus / Silicon Interstitial Annealing After Ion Implantation P. H. Keys, R. Brindos, V. Krishnamoorthy, M. Puga-Lambers, and K. S. Jones, Dept. of Materials Science and Engineering, University of Florida, Gainesville, FL M. E. Law, Dept. of Electrical and Computer Engineering, University of Florida, Gainesville, FL ABSTRACT The release of interstitials from extended defects after ion implantation acts as a driving force behind transient enhanced diffusion (TED). Implantation of Si+ ions into regions of phosphorus-doped silicon provides experimental insight into the interaction of silicon interstitials and dopant atoms during primary damage annealing. The presence of phosphorus influences the morphology of secondary defects during initial nucleation. Transmission electron microscopy (TEM) is used to differentiate between defect types and quantify the interstitials trapped in extended defects. This analysis reveals that phosphorus results in a reduction of interstitials trapped in observable extended defects. The interstitial flux released from the implanted region is also affected by the phosphorus doping. This phenomenon is closely studied using secondary ion mass spectrometry (SIMS) to monitor diffusion enhancements of dopant layers. Shifts in diffused dopant profiles are correlated with the different morphologies of the extended defects and the decay of the silicon interstitial supersaturation. This correlation is used to understand the interaction of excess silicon interstitials with phosphorus atoms.
INTRODUCTION A thorough understanding of the close relationship between dopant and defect interactions is vital for continued performance improvements of future integrated circuit device generations. A large amount of information about the nature of the silicon interstitial point defect and its role in TED has been obtained from near surface silicon implant studies.1,2 However, the introduction of dopant atoms has shown to have an influence on the formation of extended defects3,4 and the nature of TED. 5,6 Furthermore, it is unclear how the infamous {311} defect behaves in highly doped material as opposed to undoped silicon. Experimental investigation of all these effects can be conducted simultaneously by implanting near surface Si+ ions into relatively deep phosphorus doped wells and subsequently annealing. This allows for the interaction of self interstitials and phosphorus dopant atoms to occur in the near surface portion of the well, while the resulting diffusion enhancements occur in the undamaged tail region of the well, far removed from the self implant. Additionally, this allows one to study the behavior of the {311} defect in both intrinsic and extrinsic doped environments by varying the concentration of the phosphorus well. As will be demonstrated, the background phosphorus concentration can have a dramatic effect on the extended defect formation. Also, it will be shown that there is a strong correlation between the defect dissolution and the observed diffusion enhancements. EXPERIMENT Starting sil
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