Flash Annealing Technology for USJ: Modeling and Metrology
Millisecond annealing either by flash lamp or laser appears to be the leading approach to meet the needs of ultra-shallow junction annealing and polysilicon activation for advanced technology nodes. There are many advantages to this technology including high electrical activation, excellent lateral abruptness, controlled and limited dopant diffusion and the ability to engineer the extended defects remaining from the ion implantation. There are also many challenges such as potential pattern effects, local and global wafer stress and difficulty in process integration. Additional challenges include the need to extend the capabilities of process TCAD to allow accurate simulation and prediction of the ms processes. Modeling of diffusion, activation and defect evolution for a variety of technologically interesting doping conditions must be dependable to allow the device designer and process engineer to predict the device behavior after ms annealing. Existing models fall short or still need to be validated. Metrology for ultra-shallow junctions is also a challenge. The ability to accurately and repeatably measure sheet resistance and junction leakage on junctions of the order of 10nm deep is very difficult. This paper provides an overview of flash lamp annealing and deal with some promising extensions of process simulation to enable the predictive modeling of junction behavior under flash lamp annealing conditions. We also examine some of the new metrology techniques for characterization of these very shallow junctions and look at some of the trends exhibited for different junction formation details
The Influence of the Amorphous Phase on Ion Distributions and Annealing Behavior of Group III and Group V Ions Implanted into Silicon
A study has been made of room‐temperature implantations of group III and group V ions into amorphous Si layers prepared by the previous implantation of Si ions into crystalline Si substrates. Neutron activation combined with anodic oxidation and HF stripping techniques was used to determine the proflies of the implanted ions for Ga71 and Sb121. Electrical evaluation of the implanted layers by Hall effect and sheet resistivity measurements in conjunction with layer removal techniques yielded profiles of the net electrically active species and the depth variation of mobility after annealing for 30 min in the temperature range 600°–900°C. The ion species studied were B11 (60–200 keV), Al27 (200 keV), Ga69&71 (140 and 280 keV), P31 (100–280 keV), As75 (280 keV), Sb121&123 (120 and 260 keV), and Bi209 (240 keV). The epitaxial regrowth of the amorphous phase at 600°C causes most of the implanted ions within this region to become electrically active and uncompensated for the ion species B, P, As, Sb, and Bi even for peak ion concentrations in excess of 1020 cm−3. For Al and Ga implants, the number of carriers was less than the number of implanted ions. The profiles obtained for these implantations into amorphous Si were compared with predictions based on the theory of Lindhard, Scharff, and Schiott.
l-Phenylalanine dehydrogenase from Brevibacterium sp. for production of l-phenylalanine by reductive amination of phenylpyruvate
SummaryFor production of l-phenylalanine the reductive amination of phenylpyruvate, catalyzed by phenylalanine-dehydrogenase was examined. To reach high levels and a sufficient stability of the inducible intracellular enzyme, growth conditions of Brevibacterium sp. are optimized. For continuous production of l-phenylalanine in an enzyme membrane reactor, the kinetic parameters of the partially purified enzyme are determined.In continuous production a space time yield of 37.4 g l-Phe l-1 d-1 can be reached.By means of the measured kinetic parameters and simultaneous calculation of the mass balances of all reaction components the behaviour of the reactor can be simulated. For certain conditions the multi-enzyme-system shows multiple steady-states.