Ion-Beam Processing of Ion-Implanted Si
- PDF / 292,160 Bytes
- 5 Pages / 420.48 x 639 pts Page_size
- 8 Downloads / 233 Views
ION-BEAM PROCESSING OF ION-IMPLANTED Si
H.B. DIETRICH, R.J. CORAZZI, AND W.F. TSENG Naval Research Laboratory, Washington, DC 20375 Abstract Substrates can undergo major temperature excursions during ion implantation if they are not well heat sunk. At power densities 2 on the order of 50 watts per cmradiatively cooled Si will melt in a matter of seconds. Such power densities can be maintained over a few sq. cms with many of the beams produced by even the moderate current machines currently used for doping Si and the III-V's. We have made use of this fact to study pulsed ion-beam annealing of implanted Si. Two types of studies have been carried out. In the first, 5-20 sec proton irradiations were done at 2 power densities of 3-35 watts cmto produce sample temperatures 16 2 of 500 to 1100*C. 2x1O cm280 keV B, BF2 , As and P implants were annealed in this manner. Sheet resistances, P., versus power density curves were obtained for each ion and compared to ps vs T data obtained for furnace annealed companion samples. In the 6 2 second study the 2x1O1 cm280 keV implants were carried out at progressively higher current densities so that the dopant beam itself raised the sample temperature to 500-1000*C. For each ion (other than B) it was possible to obtain power densities which resulted in self-annealing implants whose sheet resistances were as low as those obtained with the optimal furnace anneal. Details of the experiments, electrical and physical properties of the pulsed ion-beam annealed layers and device applications will be presented in this paper. Introduction Some years ago, Freeman' showed that if a Si wafer is restricted to radiative cooling its temperature will increase to something on the order of 1000°C, within seconds after it begins to absorb power at a level of 10's of 2 watts/cm . This fact has been made use of to do transient annealing with furnaces, lamps and charged particle beams. It also explains why, if not well heat sunk, substrates undergo major temperature excursions during ion implantation. In fact, if some minimal care is taken to minimize conduction losses the dopant beam can be used to bring samples to temperatures typical of post implantation annealing, during the implantation process. 2
Merli and Zignani first drew attention to the possibility of these selfannealing implants (SAI) and later Merli and co-workers published a series of 3 5 papers showing the feasibility of this process. ,4, In this paper, we report on the results of self-annealing As,P and BF 2 implants and we also give data on B, BF2 and As implants annealed with 5-20 sec proton beam irradiations. Experimental 2
For this work, 0.8 cm Si samples (8.3x9.5 mm) were mounted free standing 2 in a 1.3mm slot in a stainless bar and a 0.5 cm area (7x7 mm) was irradiated with protons or the self-annealing implant. The active dopants were implanted into lightly doped substrates of the opposite sign. All proton irradiations and self-annealing implants were done at 280 keV. Sheet resistances were measured with a four-point probe. Dama
Data Loading...
