Electromigration (EM) in thin Al and Al/Si resistors was investigated by measuring the effect of the stress on the resistance, the temperature coefficient alpha, the low-frequency noise spectrum (20 mHz-1 Hz) and, for some Al samples, on the residual resistance at T = 11 K. It was found that the temperature coefficient variations versus the stress time have a different behaviour for Al and Al/Si, that is an oscillation in the first part of the life of the sample and decreases in the last one, in the first case, whereas, in the second, only the oscillation was detected. This behavior, observed for the first time, has been modeled by means of the Mayadas theory, by supposing a Gaussian distribution of the reflection coefficient for electrons at the grain boundaries. The measurement of the residual resistance also supports the hypothesis that the behaviour of alpha and R(o) (the resistance value at 273 K) is mainly due to the modification of the grain-boundary structure and cannot be explained by taking in account only the variation of the residual resistivity. Besides, the noise measurements give a further proof that the origin of the 1/fg spectra in thin films subjected to high current density must be ascribed to phenomena occurring at the grain-boundaries which are correlated to the phenomena causing temperature coefficient variations.
VARIATIONS OF TEMPERATURE-COEFFICIENT AND NOISE IN THIN AL AND AL-SI RESISTORS SUBJECTED TO HIGH-CURRENT DENSITY
DILIGENTI, ALESSANDRO;NERI, BRUNO;NANNINI, ANDREA;
1991-01-01
Abstract
Electromigration (EM) in thin Al and Al/Si resistors was investigated by measuring the effect of the stress on the resistance, the temperature coefficient alpha, the low-frequency noise spectrum (20 mHz-1 Hz) and, for some Al samples, on the residual resistance at T = 11 K. It was found that the temperature coefficient variations versus the stress time have a different behaviour for Al and Al/Si, that is an oscillation in the first part of the life of the sample and decreases in the last one, in the first case, whereas, in the second, only the oscillation was detected. This behavior, observed for the first time, has been modeled by means of the Mayadas theory, by supposing a Gaussian distribution of the reflection coefficient for electrons at the grain boundaries. The measurement of the residual resistance also supports the hypothesis that the behaviour of alpha and R(o) (the resistance value at 273 K) is mainly due to the modification of the grain-boundary structure and cannot be explained by taking in account only the variation of the residual resistivity. Besides, the noise measurements give a further proof that the origin of the 1/fg spectra in thin films subjected to high current density must be ascribed to phenomena occurring at the grain-boundaries which are correlated to the phenomena causing temperature coefficient variations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
