Palladium-Test: A Tool to Evaluate Gettering Efficiency

Abstract

A new method is presented which is suitable to check gettering processes and to evaluate gettering efficiencies. This method is based on an intentional contamination of the respective silicon wafer by means of palladium or any other haze forming metal. The palladium is diffused and haze is revealed by preferential etching. In order to determine gettering efficiency the sizes of the haze areas on gettered and non-gettered wafers are compared. The quantity of the gettered palladium can be deduced from lateral palladium profiles.In contrast to procedures published in the literature this method is very simple and fast. Therefore it is suitable for routine application to check back side damaged wafers or internal gettering.

Impact of Research on Defects in Silicon on the Microelectronic Industry

“…± ± The earliest method [30] for fast and easy detection of metal impurities was the haze method developed by Graff: In this method the fact is used that these impurities can form precipitates so fast, that after cooling from diffusion temperature, precipitates are present in the vicinity of the surface in a large density. After in-diffusion and cooling with a suitable rate in diffusion furnace the defects are delineated by a defect etch (e.g.…”

“…The resulting precipitate structure for a given transition element, its concentration and the annealing treatment is in fact a combination of kinetic and energetic aspects. The industry research [30] that helped to understand the phenomenon of haze formation by metal impurity precipitation was followed by a collaboration with university using HREM for identification of precipitate morphologies without volume change (Ni, Co [45]) and with volume change (Cu) [46]. The morphology was then correlated with low breakdown voltages of gate oxides to explain the different behavior of Cu (significant lowering of the breakdown voltage [47]) and Ni (small lowering of the breakdown voltage [48]), another example how academic research results were directly applied to current device technology issues [49± 52] and contributed to the understanding of the observed phenomena.…”

Gettering of Pd to implantation-induced nanocavities in Si

“…Possible causes for such behavior at this temperature include gettering of O from within Czochralski Si with subsequent ejection of previously trapped metal, 12 nanocavity instability, 13 and metal detrapping from nanocavity walls due to thermal excitation. 14 In general, the amount of Pd not located in the nanocavities or in the implant region was below the calculated solubility of Pd at the annealing temperatures, 9,15 thus indicating that nanocavities are an efficient sink for Pd.…”

“…6 The micrograph of Fig. 2 is taken from a 1ϫ10 15 Pd cm Ϫ2 implant annealed at 950°C for 1 h and shows at least two nanocavities with evidence of crystalline precipitates. The moiré patterns were consistent with PdSi, the most Si-rich silicide phase observed following thermal annealing of Pd layers on Si at atmospheric pressure.…”

“…Micrograph of a 235 keV 1ϫ1015 Pd cm Ϫ2 implanted sample following annealing at 950°C for 1 h. Note the nanocavities containing moiré fringes at the center of the image.FIG. 3.…”