Short Time Annealing of As and B Ion Implanted Si using Tungsten-Halogen Lamps
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SHORT TIME ANNEALING OF As and B ION IMPLANTED Si USING TUNGSTEN-HALOGEN LAMPS
T. 0. Sedgwick*, R. Kalish*, S. R. Mader*, and S. C. Shatas** *IBM T. J. Watson Research Center, Yorktown Heights, NY 10598; **A. G. Associates, Palo Alto, CA 94303
ABSTRACT B and As implanted Si wafers have been thermally annealed by an array of tungsten halogen lamps at 1000-1200°C for 1-10 sec. Annealing above 1100'C leaves the crystal free of extended defects in all cases as determined by TEM. An enhanced diffusion is observed above normal values characterized by a low activation energy for both As and B samples. This enhanced diffusion is transient and occurs within about one second since the RBS and SIMS dopant profiles are identical for I sec and a 10 sec anneal.
INTRODUCTION t Many recent studies have used short time annealing( ) (STA) to minimize the dopant diffusion during the required post implantation thermal anneal. The most promising approach has been to 2 3 use large area (> 10 cm) incoherent light sources including tungsten-halogen lamp arrays( , ) argon 5 7 discharge lamps(4), xenon flash( ) lamps and resistance heated black body radiation sources(6, ). Radiation from all these sources is efficiently absorbed in the Si which is heated to a temperature in the 1000-1200°C range for 1-100 sec and then allowed to cool by radiation. There have been some indications that STA of ion implanted Si can lead to high dopant activation and high conductivity with no resultant dopant diffusion. However, crystal regrowth and dopant activation can already occur at 750-950°C(7,8) at which temperatures extended defect removal does not take place. The more demanding condition and more relevant requirement is - How much diffusion occurs during STA under conditions which remove all extended defects? Another complicating feature in STA studies is that temperature measurement of the sample during annealing has been very primitive or not even made at all. On the other hand, Kalish et al(9) and Sadana et al.t°) using tungsten-halogen lamp arrays and 4 Hodgson et al.( ) using an argon discharge lamp report defect-free annealing of highly doped As in Si samples at 1000 C and above. At the same time, the diffusion in STA annealed samples has 0 4 been observed by these and other investigators(2,6,1 ) and Hodgson( ) has pointed out that the 9 diffusion was enhanced but did not further characterize it. Kalish et al( ) have analyzed the enhanced diffusion after STA of As implanted Si. Enhanced diffusion as a result of ion irradiation has long been recognized. Hofker(11) and Itoh 12 and Ohdomari( ) observed enhanced diffusion in ion implanted samples during an initial anneal for tens of minutes but did not further resolve its time dependence. In general, an initial enhanced diffusion is observed for ion implanted and furnace annealed samples. However, it has not been important before the present need for very shallow junctions. It has also not been extensively studied and in the case of heavily doped junctions it is hard to separate from concentration
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