Defect Control during Epitaxial Regrowth by Rapid Thermal Annealing
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DEFECT CONTROL DURING THERMAL ANNEALING
EPITAXIAL
REGROWTH
BY
RAPID
H. Baumgart, G. K.Celler, D. J. Lischner*, McD. Robinson, and T. T. Sheng
Bell Laboratories, Murray Hill, New Jersey 07974, USA *Bell Laboratories, Allentown, Pennsylvania 18103
ABSTRACT Rapid Thermal Annealing (RTA) with tungsten halogen lamps provides excellent regrowth of silicon layers damaged by ion implantation. In addition to minimizing dopant redistribution, the inherent advantage of this technique is good control of temperature gradients. The latter is instrumental in reducing the density of extended defects in the annealed samples. In contrast, solid phase laser annealing, which involves steep temperature gradients, always leaves interstitial dislocation loops and point defect clusters. We present a comparative study of crystal quality following laser processing and incoherent light annealing as well as furnace annealing of As, P and B ion implanted Si wafers. INTRODUCTION During the past five years the search for rapid semiconductor heat treatment techniques has been focused on lasers and electron beams. One of the more recent developments has been the introduction of graphite resistive heaters and high intensity halogen lamps for rapid isothermal annealing. Rapid Thermal Annealing (RTA) with incoherent light from tungsten-halogen lamps allows fast and precise temperature-time cycles in a clean and controlled environment. Compared to conventional furnace annealing the new technique retains the temporal advantage of laser annealing, reconstructing amorphized layers within seconds. Early experiments with continuous lamps for annealing of sheet implants of As and B indicated complete electrical activation of the dopant [1,2,3,41. The uniform heating of full-size wafers and the potential of high throughput using sequential wafer handling make RTA attractive for semiconductor processing. In this paper we present a comparative study of crystalline quality and perfection resulting from incoherent light annealing, conventional furnace annealing, and from scanning cw laser annealing. Its purpose is to assess the relative advantages of the three heat treatment techniques for practical applications in annealing of whole wafers. EXPERIMENTAL METHODS Ion implanted silicon wafers were annealed in a few seconds by the intense radiation from an air-cooled array of tungsten halogen lamps. The samples are positioned below the lamps in a wafer chamber with a quartz window, that allows annealing in an inert atmosphere. Each wafer is placed on three quartz pins for thermal insulation. Details of the RTA light furnace as well as the spatial and temporal temperature profiles have been published in Ref. 5. In our experiments the samples were and 3" Si wafers with a resistivity of 20-50 f1 cm. They were implanted with 1502 keV As, 50 keV B, or 100 keV P, the implant doses ranging from 1014 to 1016 cm- . Solid phase epitaxial recrystallization of the ion implantation amorphized surface layers was accomplished in 10 or 30 sec at a preset temperature. The fu
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