Temperature dependence of the dielectric response of anodized Al–Al[sub 2]O[sub 3]–metal capacitors.

The temperature dependence of capacitance, C[sub M], and conductance, G[sub M], of Al-Al[sub 2]O[sub 3]-metal capacitors with Cu, Ag, and Au electrodes has been measured between 100 and 340 K at seven frequencies between 10 kHz and 1 MHz. Al[sub 2]O[sub 3] films between 15 and 64 nm thick were formed by anodizing evaporated Al films in borate-glycol or borate-H[sub 2]O electrolyte. The interface capacitance at the Al[sub 2]O[sub 3]-metal interface, C[sub I], which is in series with the capacitance C[sub D] due to the Al[sub 2]O[sub 3] dielectric, is determined from plots of 1/C[sub M] versus insulator thickness. C[sub I] is not fixed for a given metal-insulator interface but depends on the vacuum system used to deposit the metal electrode. C[sub I] is nearly temperature independent. When C[sub I] is taken into account the dielectric constant of Al[sub 2]O[sub 3] determined from capacitance measurements is ∼8.3 at 295 K. The dielectric constant does not depend on anodizing electrolyte, insulator thickness, metal electrode, deposition conditions for the metal electrode or measurement frequency. By contrast, G[sub M] of Al-Al[sub 2]O[sub 3]-metal capacitors depends on both the deposition conditions of the metal and on the metal. For Al-Al[sub 2]O[sub 3]-Cu capacitors, G[sub M] is larger for capacitors with large values of 1/C[sub I] that result when Cu is evaporated in an oil-pumped vacuum system. For Al-Al[sub 2]O[sub 3]-Ag capacitors, G[sub M] does not depend on the Ag deposition conditions. [ABSTRACT FROM AUTHOR]