MIM Capacitors Using BaSm[sub 2]Ti[sub 4]O[sub 12] and Sm[sub 2]Ti[sub 2]O[sub 7] Dielectrics

Abstract

The dielectric properties of BaSm 2 Ti 4 O 12 ͑BST͒ and Sm 2 Ti 2 O 7 ͑ST͒ films were investigated in order to evaluate their potential for use in metal-insulator-metal ͑MIM͒ capacitors. The crystalline BST phase was formed when the film was grown at 700°C and subjected to rapid thermal annealing ͑RTA͒ at 900°C. The ST phase was formed in the film grown at 300°C and subjected to RTA at 900°C. A high capacitance density of 4.84 fF/m 2 and a low leakage current density of 4.28 fA/pF V were obtained from the BST film with a thickness of 138 nm. The BST film has the linear and quadratic coefficients of capacitance of 684 ppm/V and −295 ppm/V 2 , respectively, and a temperature coefficient of capacitance of −136 ppm/°C at 100 kHz. The ST film has a high capacitance density ͑3.47 fF/m 2 ͒ and a very low leakage current density ͑0.26 fA/pF V͒. The ST film also showed small voltage and temperature coefficients of capacitance. Therefore, both the BST and ST films are good candidate materials for MIM capacitors.Metal-insulator-metal ͑MIM͒ capacitors are important passive devices in radio frequency ͑rf͒ circuits or mixed-signal integrated circuits. MIM capacitors commonly use SiO 2 or Si 3 N 4 dielectrics because they have good voltage linearity properties and thermal stability. However, their capacitance density is very small because of their low dielectric constant ͑͒. 1,2 Recently, many investigations have been conducted into high-dielectrics in order to obtain the high capacitance density, which is essential to reduce the size of integrated circuits. An Al 2 O 3 film with a thickness of 12 nm exhibited a high capacitance density of 5.0 fF/m 2 ; however, it had a large voltage coefficient of capacitance ͑VCC͒. 3 An HfO 2 film with a thickness of 56 nm grown by pulse laser deposition showed small voltage and temperature coefficients of capacitance, but its capacitance density was relatively low. 4 An HfO 2 film deposited by magnetron sputtering showed a high capacitance density, but its VCC was not satisfactory. 5 A MIM capacitor was also produced using a film with a composition of ͑1 − x͒HfO 2 -xAl 2 O 3 and it showed a low VCC; however, its capacitance density was relatively low ͑3.5 fF/m 2 ͒. 6 An MIM capacitor made using a film with an Al 2 O 3 and HfO 2 laminate structure was grown by atomic layer deposition ͑ALD͒. Even though it had small voltage and temperature coefficients, its capacitance density was low, being approximately 3.13 fF/m 2 . 7 Pr 2 O 3 film was also reported to have a high capacitance density but exhibited a large VCC. 8 A high capacitance density of 17.0 fF/m 2 and a low leakage current of 10 −7 A/cm 2 were obtained from a MIM capacitor using a ZrO 2 film with a thickness of 12 nm, but variation of the capacitance with bias voltage and temperature has not been reported. 9 According to the International Technology Roadmap for Semiconductors ͑ITRS͒, capacitance densities of 4.0 fF/m 2 and 20-30 fF/m 2 are required for the analog and bypass capacitors that will be needed in the period from 2007 and 20...

High-Capacitance Metal-Insulator-Metal Capacitors Using Amorphous Sm[sub 2]Ti[sub 2]O[sub 7] Thin Film

“…Therefore, there was a small amount of SmT crystals in the film grown at 200°C, as suggested in previous work. 12 The k value and capacitance density of the amorphous SmT films grown at room temperature were relatively small compared with the requirement for the rf MIM capacitor by 2012.…”

“…11 SmT films containing BaO as a second phase was obtained when the deposition temperature of the BaSm 2 Ti 4 O 12 film was low. 12 Moreover, a 100 nm thick crystalline SmT film grown at 200°C and annealed at 900°C had a capacitance density of 5.2 fF/m 2 with a very low leakage current of 1.34 nA/cm 2 at 2 V. 13 This SmT film also had a small linear and quadratic VCC of 11 ppm/V and −99.5 ppm/V 2 , respectively, with a low-temperature coefficient of capacitance ͑TCC͒ of 135 ppm/°C at 100 kHz. 13 Therefore, crystalline SmT films are considered good candidate materials for MIM capacitors.…”

“…However, the process temperature used to grow the crystalline SmT films is too high for applications in back-end line integration. 12,13 Therefore, it is essential to grow homogeneous SmT films at low process temperatures in order for them to be used in MIM capacitors. In this study, homogeneous amorphous SmT films were grown at 200°C and their dielectric properties were investigated to assess their potential use in MIM capacitors.…”

Investigation on the Electrical Properties of the Ba[sub 2]Ti[sub 9]O[sub 20] Thin Films for Metal-Insulator-Metal Capacitor Application

“…Similar results have been observed in the BaTi 4 O 9 and BaSm 2 Ti 4 O 12 films. 18,19 Figure 3a and b shows the capacitance densities of the crystalline and amorphous BT films measured at various frequencies, respectively. The capacitance density of the 132 nm thick crystalline BT film was approximately 2.9 fF/m 2 and increased with decreasing film thickness to 6.1 fF/m 2 for the 61 nm thick crystalline BT film.…”

Microstructure and dielectric properties of amorphous BaSm2Ti4O12 thin films for MIM capacitor

“…14 Crystalline BST thin film was also shown to be potentially applicable to MIM capacitors. 15 However, the process temperature used to grow crystalline BST films is higher than that used for the VLSI back-end process (≤400 • C). Consequently, it is necessary to lower the process temperature used for fabrication of the device within the thermal budget of back-end process.…”