EBIC Investigation of Defects Induced in CW Beam-Annealed Si
- PDF / 864,593 Bytes
- 8 Pages / 415.8 x 637.2 pts Page_size
- 103 Downloads / 208 Views
155
EBIC INVESTIGATION OF DEFECTS INDUCED IN CWBEAM-ANNEALED Si
N.H. SHENG, M. MIZUTA , and J.L. MERZ Department of Electrical and Computer Engineering, University of California, Santa Barbara, California, 93106, USA ABSTRACT EBýC has been used to investigate the beam-induced damage in As -implanted Si subjected to scanned laser or electronbeam annealing. Comparison is made between these annealing techniques; in general, electron-beam annealing is found to give superior results. In addition, several different experiments combining these techniques are described. Samples were pre-annealed prior to laser annealing, using either thermal or electron-beam annealing. Other samples were given a thermal post-anneal after laser-annealing. The effect of these treatments on defect formation is discussed. INTRODUCTION It has been reported that ion-implanted damage in Si can be annealed by CW laser annealing (LA) [1] or scanning electron beam annealing (SEBA) [2]. For CW laser annealing, it has been shown that good quality, defect free singlecrystal material can be produced over a reasonable range of laser power [3]. Lattice defects, such as small, point-defect clusters observed at lower laser power developing into a high density of dislocation loops with increased laser power and finally slip dislocations observed at much higher power, have also been reported [4]. As far as SEBA is concerned, several different annealing systems have been used [2,5,6] with promising results; for example, recrystallization has been reported with low residual dislocation loops in the top layer [5,6] and non-degraded lifetime in the substrate material [6]. Recently however, strong, non-uniform features have been observed after CWLA using the electron-beam-induced current (EBIC) mode of the SEM [7]. Both EBIC [7] and low temperature photoluminescence [8] results have shown that the CWLA window is quite narrow in order to get good minority carrier effects; for laser power exceeding an optimum value, the annealing laser beam induces defects which appear to be quite deep. EBIC studies of scanning electron-beam annealed Si, on the other hand, show better planar uniformity as compared with CWLA [9]: dark stripes are usually not observed, and the degree of overlap required for uniform annealing using the electron beam is much less. The purpose of this paper is twofold. First, a more detailed investigation is made of the differences between CWLA and SEBA using EBIC. To facilitate this comparison, an investigation of the effect of the substrate temperature has been made for LA. It is found that the overall minority-carrier collection efficiency is better for SEBA, and the beam-induced damage seems to be less severe. Secondly, in order to learn more about the nature of the laserinduced damage, the results of several different experiments are reported. Samples were pre-annealed prior to laser annealing, either thermally (TA) or by optimal SEBA. The stripe-like damage induced by the laser also shows up in the samples pre-annealed thermally, but not by SEBA.
Data Loading...
