Defect Evolution During Laser Annealing
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0912-C04-03
Defect Evolution During Laser Annealing Susan B. Felch1, Abhilash Mayur1, Vijay Parihar1, Faran Nouri1, Kevin S. Jones2, Daniel E. Zeenberg2, and Britta E. Jones2 1 Front End Products Group, Applied Materials, 974 E. Arques Avenue, Sunnyvale, CA, 94085 2 Dept. of Materials Science, University of Florida, Gainesville, FL, 32611
ABSTRACT Implementation of millisecond annealing requires the identification of the operating conditions for that technique which minimize the residual defects. In addition, possible combinations of low temperature annealing with millisecond annealing could result in minimal residual defects. The samples studied here were implanted with Ge+ pre-amorphization and boron dopant ions and were activated with a scanning laser annealing technique with maximum temperature dwell times of about one millisecond. The laser anneal conditions were varied, along with combinations of spike anneals. The annealed samples were analyzed by plan-view transmission electron microscopy (TEM) to measure the residual defect density. The effects of spike temperature, laser annealing temperature, and scan rate will be discussed.
INTRODUCTION The need for ultra-shallow, abrupt source/drain extensions with high dopant activation is increasing the attractiveness of “diffusion-less” anneal techniques, such as flash and sub-melt laser annealing [1]. Ultra-shallow junctions formed by such anneals benefit from a preamorphization implant (PAI) before the dopant implant, since this reduces channeling of the implanted dopant and produces higher dopant activation. However, the combination of PAI with millisecond annealing can leave significant residual defects [2,3]. Increasing the anneal temperature and/or time is expected to help reduce the number of residual defects, as continuing Ostwald ripening of the defects into fewer but larger dislocation loops can occur [4-6]. In addition, combining laser anneal with lower-temperature spike anneal could result in low levels of residual defects. This study reports the influence of various laser anneal conditions along with combinations of spike anneals on the residual defect density, as measured by transmission electron microscopy (TEM).
EXPERIMENT All of the wafers used in this study were 300-mm, n-type, (100) silicon substrates. The samples were pre-amorphized with Ge+ ions at 30 keV with a dose of 5 x 1014 cm-2 using an Applied Quantum® X Implant system. This implant produces an amorphous layer that is approximately 40 nm thick. Subsequently boron dopant ions were implanted at an energy of 0.5
keV and a dose of 1 x 1015 cm-2, which is typical of sub-65 nm PMOS source/drain extensions. Finally, the dopants were activated with a scanning laser annealing technique with maximum temperature dwell times of about one millisecond [7,8]. The laser anneal temperature (T1
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