Specific Process Knowledge/Thin film deposition/Deposition of Gold/Adhesion layers: Difference between revisions
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The change in nanostructure of the Au thin film due to the presence of the adhesion layers observed above, could have an important impact on the film macroscopic properties such as electrical resistivity. Electrical resistivity in polycrystalline films is dependent on electron scattering at surfaces and grain boundaries, and it was expected that the grain size change measured with TKD to be reflected in the electrical properties. Furthermore, for the case of Cr, a Cr-Au alloy was formed, which also was expected to have an impact on the thin-film electrical resistivity. | The change in nanostructure of the Au thin film due to the presence of the adhesion layers observed above, could have an important impact on the film macroscopic properties such as electrical resistivity. Electrical resistivity in polycrystalline films is dependent on electron scattering at surfaces and grain boundaries, and it was expected that the grain size change measured with TKD to be reflected in the electrical properties. Furthermore, for the case of Cr, a Cr-Au alloy was formed, which also was expected to have an impact on the thin-film electrical resistivity. | ||
To verify these hypotheses, the sheet resistance (R) of the three samples (20nm Au, 2nm Ti/20nm Au, and 2nm Cr/20nm Au) was measured using micro 4-point probe (''µ''4PP). Fig. 13a shows that the Ti/Au sample had a lower sheet resistance than pure Au, which can be attributed to the two layers acting as parallel resistors. Data normalization was performed with respect to the average sheet resistance (R) measured at the 20-Au sample. To exclude tip wear effects of the ''µ''4PP, the measurements were performed measuring with the same probe alternatively on the 20nm Au and 2nm Ti/20nm Au sample, respectively. Fig. | To verify these hypotheses, the sheet resistance (R) of the three samples (20nm Au, 2nm Ti/20nm Au, and 2nm Cr/20nm Au) was measured using micro 4-point probe (''µ''4PP). Fig. 13a shows that the Ti/Au sample had a lower sheet resistance than pure Au, which can be attributed to the two layers acting as parallel resistors. Data normalization was performed with respect to the average sheet resistance (R) measured at the 20-Au sample. To exclude tip wear effects of the ''µ''4PP, the measurements were performed measuring with the same probe alternatively on the 20nm Au and 2nm Ti/20nm Au sample, respectively. Fig. 13b shows that the Cr/Au system had a higher sheet resistance than pure Au. In this case, the formation of a single layer due to Cr-Au inter-diffusion compromised the multilayer assumption. The sheet resistance increase is in line with the general resistivity increase of Cr-Au alloys, which increases linearly with the Cr concentration. Data acquisition and normalization were done as in the Ti/Au case. | ||
The Ti/Au parallel behavior and Cr/Au inter-diffusion seem to have a larger impact on the electrical properties of the multilayer systems than the nanostructure change observed by TKD. For both samples, the increase of grain boundary scattering due to the higher density of grain boundaries, compared to pure Au, could not be measured with setup used, but cannot be excluded a priori. | The Ti/Au parallel behavior and Cr/Au inter-diffusion seem to have a larger impact on the electrical properties of the multilayer systems than the nanostructure change observed by TKD. For both samples, the increase of grain boundary scattering due to the higher density of grain boundaries, compared to pure Au, could not be measured with setup used, but cannot be excluded a priori. | ||
[[File:Picture16.png|550px|center|thumb|Fig. | [[File:Picture16.png|550px|center|thumb|Fig. 13: (a) Normalized sheet resistance of 20-Au vs 2-Ti/20-Au samples. The Ti/Au bilayer system has lower sheet resistance than pure Au due to parallel resistors behavior. (b) Normalized sheet resistance of 20-Au vs 2-Cr/20-Au samples. The Cr/Au bilayer system has higher sheet resistance than pure Au due to Cr-Au | ||
alloy formation.]] | alloy formation.]] | ||