Effect of annealing conditions on precipitate and defect evolution in oxygen implanted SOI material

Summary form only given. The effects of annealing temperature, time, and ambient on the evolution of defects and precipitates in the superficial silicon layer in SIMOX material are discussed. Precipitates and defects were studied with various electron microscopy techniques, including high-resolution imaging. Annealing temperatures from 1250°C to 1300°C for 2 hours in a nitrogen ambient produced qualitatively the same general structure in the samples. This consisted of a precipitate-free upper region of the superficial layer and a high density of precipitates in the lower region of the layer. Dislocations frequently ran laterally between adjacent precipitates, but some dislocations also ran upward to the wafer surface from precipitates closer to the surface of the superficial layer. The buried layer had a waviness of about the same size as the precipitates. Increasing time at a given temperature increased precipitate size only slightly. Increasing temperature form 1250°C to 1300°C at a time of 2 hours increased the precipitate-free region from 1/4 to 2/3 of the top of the superficial layer and increased precipitate size from 40 nm to 70 nm. Increasing temperature to 1325°C or 1350°C at 2 hours eliminated precipitates in the lower region of the layer. As expected, pinned lateral dislocations were eliminated when precipitates were incorporated into the buried oxide interface at the higher annealing temperatures. However, dislocations stabilized by the wafer surface extended downward to buried oxide and could not be removed, even at the highest temperatures and longest annealing times. Annealing with an argon ambient is also discussed.