Electronic Defects in Silicon after Transient Isothermal Annealing

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ELECTRONIC DEFECTS IN SILICON AFTER TRANSIENT ANNEALING

ISOTHERMAL

G. PENSL, M. SCHULZ, P. STOLZ, Institute of Applied Physics, University Erlangen, D-8520 Erlangen, FRG N.M. JOHNSON, Xerox P-alo Alto Research Center, J.F. GIBBONS, J. HOYT, Stanford Electronics Laboratories,

Palo Alto, Stanford,

GlUckstr.

9,

CA 94304 CA 94305

ABSTRACT We have investigated trap levels in silicon Three after Thermal Pulse Annealing (TPA). different annealing systems consisting of tungsten lamps or a graphite heater have been applied. Trap levels induced in different silicon materials (Cz, FZ, Epi) after TPA have been studied by DLTS and admittance spectroscopy. In boron-doped epitaxial silicon and As+- implanted pn-junctions (Cz grown Si), we have observed a prevalent trap 15 cm-3 (delevel at concentrations of up to lO pending on anneal conditions and silicon material). The ionization energy of this trap level is Ev+300meV. The concentration of the 300 meV-level was studied as a function of the annealing temperature and the quench rate. The thermal pre-processing history strongly affects the trap concentration induced by TPA. The 300 meV-level is almost completely 0 removed by a subsequent furnace anneal at TA > 400 C Further trap levels are created in3 0 boronSi+ implanand aluminum- doped silicon by Ar+ or tation and TPA. The defect natures are discussed. INTRODUCTION Isothermal annealing techniques have been introduced in the past few years to activate ion implanted dopant species in the solid phase [1 - 8]. The implanted silicon wafer is irradiated by an incoherent light source (tungsten halogen lamp, arc lamp or graphite heater). The damage is annealed within a fills a gap few seconds. This Thermal Pulse Annealing (TPA) between the quasi-static furnace annealing and the fast pulsed or scanned laser annealing [9-11]. Recent investigations of implanted layers [12 - 14] resulted in a minimized dopant diffusion, a complete electrical activation, and a uniform annealing across the wafer. All these features indicate that TPA is suited for VLSI-device fabrication. In this work, we have investigated whether any additional electronic defects [15] are induced by TPA which could degrade the electrical properties of devices.

Mat. Res. Soc. Symp.

Proc. Vol.

23 (1984)D @Elsevier Science Publishing Co., Inc.

348

EXPERIMENTAL Annealing Systems Three different annealing systems are employed in this investigation of electronic defects induced by rapid thermal processing. The majority of the work focuses on samples annealed in equipment developed at Stanford Electronics Lab (SEL) for TPA or in the commercially available HEATPULSE system of AG Assoc. Both systems use radiation from tungsten filament lamps to couple power into the silicon. In a typical annealing sequence, the lamps initially provide power far in excess of the heat required to reach the anneal temperature, TA. A temperature controller decreases the lamp intensity as TA is approached, and holds the sample at this temperature for the desired annealing time (typically 2 to 6