Structural and Electrical Properties of Tin and Carbon Co-Implanted Silicon
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STRUCTURAL AND ELECTRICAL PROPERTIES OF TIN AND CARBON CO-IMPLANTED SILICON P. MEI, M. T. SCHMIDT, P. W. LI, E. S. YANG, AND B. J. WILKENSMicroelectronics Science Laboratories, Columbia University, New York, NY 10027 *Bellcore, Red Bank, NJ 07701-7040 ABSTRACT The alloy system Si.(SnCi,_),_. was investigated. In this work, samples were prepared by co-implantation of tin and carbon ions into silicon wafers with dosage range 1015 16 2 - 10 crn , followed by rapid thermal annealing. Rutherford backscattering channeling, Auger sputter profiling, and secondary ion mass spectrometry were employed to study the crystallinity, chemical composition and depth profiles. A near perfect crystallinity for 0.5% at. of tin and carbon was achieved. To study the electrical properties in the implanted materials, diode I-V measurements were performed. The data show near ideal p-n junctions in the co-implanted region. This work demonstrates promising features of group IV semiconductor synthesis by ion implantation. Introduction Fabrication of heterojunction bipolar transistors on silicon substrates has attracted much attention in upgrading silicon technology. Efforts have been made to growv silicon compatible materials which can be used as a wide band-gap emitter or a narrow bandgap base. So far, the most extensively studied materials are SiGe and SiC. Excellent SiGe bipolar devices with high cut off frequencies have been demonstrated [1]. It has to be pointed out, however, that SiGe and SiC have large lattice mismatches with silicon, which sets an intrinsic limit on the critical layer thickness and the thermal stability of devices. To surmount this problem, one approach is to compensate atoms of smaller covalent radius with larger covalent radius, relative to silicon, at an appropriate ratio. Si1 ,(Sn#Ci_•)iu is one of the possible alloys which may form unstrained heterojunctions with silicon substrates. Carbon and tin have covalent radii of 0.77 A and 1.40A respectively. According to a linear model [21, the lattice parameter of SnO.6C 0 .4 would be similar to silicon. In addition, the stable tetrahedral crystal structure of carbon-tin alloy has been predicted by theoretical consideration[3] and evidenced by experimental works in amorphous materials[4]. Therefore, it is promising to form single crystal SiSnC alloys. In this work, we investigated the possibility of forming SiSnC alloy by ion beam synthesis. This is a relatively simple technique compared with molecular beam epitaxy and chemical vapor deposition and can be easily utilized in silicon very-large-scale integrated technology. The major obstacle to this technique, however, is the ion damage which has strong effects on atomic migration and solid solubility of implanted species. In order to form a single crystal alloy, we experimented with various implantation energies, doses, as well as annealing conditions. The preliminary study of the crystal structure shows encouraging results toward single crystal alloy formation, along with some understanding of the role of ion damage. Exp
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