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This paper presents the results of our observing oxygen precipitation in a silicon crystal at 1000 °C using infrared absorption, TEM, and x-ray techniques. Comparison of results shows excellent agreement between TEM and IR for the number of precipitate particles formed. TEM data show that the number of particles increases as the annealing time is increased for oxygen contents above a critical concentration ratio of about 4 (30 ppma at 1000 °C). The number of particles formed at lower ratios remains relatively small. Detailed analysis of the TEM results has yielded a relationship between precipitate volume and the total area of punched-out loops. These loops, however, account for only a small fraction of the silicon atoms displaced by the growing precipitates. X-ray results indicate the defects are of an interstitial nature, in agreement with TEM.

The experimental data presented here show that the generation of dislocations in Si along Si3N4 edges is due to the cumulative effect of the Si3N4 stress field near the nitride edge and to the point defects produced during thermal oxidation. Within our experimental range, the stress along the Si3N4 edges alone is not sufficient to generate dislocations in silicon. We have determined a critical ratio of Si3N4 thickness to SiO2 thickness which does not lead to the generation of dislocations.

Recessed oxide isolation is widely used to reduce defects and increase packing density in Si integrated circuits. Unfortunately, the use of SiO2/SisN4 layers to mask the Si during the formation of the recessed oxide creates an unevenness in the surface, known as bird's-head, and the lateral oxidation due to the SiO2 under the SigN4 layer creates bird's-beak. Bird's-head and bird's-beak limit packing density and performance. In the framed recessed oxide-isolation process presented in this paper, the SijN4 is allowed to cover the Si surface in narrow stripes to define the recessed oxide boundary; thus both limitations are avoided. The samples were analyzed by Sirtl etch and TEM methods. For a SigN4 layer 500A thick, no induced crystal defects were present, probably because of partial stress relief within the narrow SijN4 stripes. For a SijN4 layer more than 1000A thick, dislocations appeared along the edges. The dislocations, which are of the 60 ~ type on (111) slip planes with alternate Burger's vectors, relieve part of the intrinsic tensile stress of the SigN4.

Presently, silicon device technology phosphorous diffusions with high surface concentrations are commonly used for the formation of the emitter areas. Annealing treatments at or below 800°C have been shown to lead to the formation of extrinsic dislocation loops in such areas. A transmission electron microscopic investigation combined with resistivity measurements and profile determinations leads to the interpretation of these loops as a primary step of phosphorous precipitation in the supersaturated lattice.