Investigation of soi material formed by high-dose oxygen and nitrogen implantation

Abstract

A comparison of the crystalline quality of SOI layers produced by nitrogen and oxygen implantation was performed using TEM, and SIMS measurements. The implantations were performed at 100 to 200 keV with doses between 0.6 and 1.7 × 10 18 cm −2. The implantation temperature was varied between 320 and 600°C using a specially designed radiation heater. TEM cross section microphotographs show that ion dose is a very critical parameter in case of nitrogen implantation. A formation of cracks in the Si 4N 4 layers was observed for doses above 1.1 × 10 18 cm −2 probably caused by the low nitrogen diffusion coefficient in Si 3N 4 and silicon. The best results in respect to crystallinity were obtained after annealing at 1200 °C showing a very low defect density. For higher temperatures, polycrystalline Si 3N 4 forms with a higher defect density in the top silicon layer than that at 1200°C. In the case of oxygen implantation, all SiO 2 precipitates which form at lower annealing temperatures are dissolved after annealing above 1300°C resulting in a very abrupt and smooth interface. In comparison to nitrogen produced SOI layers, less defects occur above 1300°C annealing whereas in the nitrogen case, 1200°C are sufficient to obtain a good crystalline quality.