New DSPEG Approach to Improvement of SOS Using Low Dose Self-Implantations
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NEW DSPEG APPROACH TO IMPROVEMENT OF SOS USING LOW DOSE SELF-IMPLANTATIONS ELIEZER DOVID RICHMOND*, ALVIN R. KNUDSON*, AND H. KAWAYOSHI** *Naval Research Laboratory, Code 6816, Washington, D.C. 20375-5000 **Advanced Research and Applications Corporation, Sunnyvale, CA. 94086 ABSTRACT A new approach is proposed for the material improvement of silicon-on-sapphire (SOS). This approach utilizes the phenomena that the defect elimination throughout the silicon layer depends on both the deep and shallow self-implantations technique of the double solid phase epitaxial growth (DSPEG) for SOS material improvement. The new aspects of this approach are that the deep implantation does not form an amorphous layer, and therefore the ion damage to the substrate is minimized eliminating Al autodoping of the silicon layer. INTRODUCTION Over the past few years material improvement of silicon-on-sapphire (SOS) has been achieved by different ion implantation and annealing techniques [1,2]. One approach, illustrated in Fig. 1 and labelled as the "Standard" DSPEG Process, involves a deep self-implantation 01 which forms an amorphous layer in the region of the silicon/sapphire interface [2]. This amorphous region is regrown by solid phase epitaxial growth using the silicon near the surface as a seed,
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shallow self-implantation 02 is performed to form an amorphous layer in the surface region which extends to the silicon surface. The improved silicon material near the interface acts as a seed during the furnace anneal for the solid phase epitaxial growth of the surface amorphous layer. Material improvement from this method have been well documented in ref [2] and the references cited there. Nonetheless, an optimum parameter choice [3] for the improvement of the crystalline quality by this method still results in autodoping caused by outdiffusion from the sapphire substrate which is damaged by the deep implantation. Recently [3], it has been clearly shown, that for low values of the fluences of 01 and $2, that the improvement of the crystalline quality and reduction of the microstructural defects anywhere in the silicon layer is dependent on both self-implantations. That is, the deep implantation causes material improvements near the surface, and the shallow implantation causes material improvements near the interface. This is true even though the deposited damage energy is small or negligible in the region of material improvement. In this paper, utilization is made of the interdependence on $2 to reduce the defect density in the interface region. Specifically, the deep implantation fluence is reduced by 30% over the "Standard" DSPEG Process, while the shallow Mat. Res. Soc. Symp. Proc. Vo.. 74. ý1987 Materials Research Society
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implantation fluence remains constant. With this approach less damage is caused to the silicon/sapphire interface. This re
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