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Articles you may be interested inDetailed leakage current analysis of metal-insulator-metal capacitors with ZrO2, ZrO2/SiO2/ZrO2, and ZrO2/Al2O3/ZrO2 as dielectric and TiN electrodes J. Vac. Sci. Technol. B 31, 01A109 (2013); 10.1116/1.4768791 Impact of bottom electrode and Sr x Ti y O z film formation on physical and electrical properties of metalinsulator-metal capacitors Appl. Phys. Lett. 98, 182902 (2011); 10.1063/1.3584022 Influence of precursor chemistry and growth temperature on the electrical properties of SrTiO 3 -based metalinsulator-metal capacitors grown by atomic layer deposition J. Vac. Sci. Technol. B 29, 01AC04 (2011); 10.1116/1.3525280 Impact of crystallization behavior of Sr x Ti y O z films on electrical properties of metal-insulator-metal capacitors with TiN electrodes Appl. Phys. Lett. 97, 162906 (2010); 10.1063/1.3505323 Atomic-layer-deposited Al 2 O 3 -Hf O 2 -Al 2 O 3 dielectrics for metal-insulator-metal capacitor applications Appl. Phys. Lett.In this work, the physical and electrical properties of Sr x Ti 1−x O y ͑STO͒-based metal-insulator-metal capacitors ͑MIMcaps͒ with various compositions are studied in detail. While most recent studies on STO were done on noblelike metal electrodes ͑Ru, Pt͒, this work focuses on a low temperature ͑250°C͒ atomic layer deposition ͑ALD͒ process, using an alternative precursor set and carefully optimized processing conditions, enabling the use of low-cost, manufacturable-friendly TiN electrodes. Physical analyses show that the film crystallization temperature, its texture and morphology strongly depends on the Sr/Ti ratio. Such physical variations have a direct impact on the electric properties of Sr x Ti 1−x O y based capacitors. It is found that Sr-enrichment result in a monotonous decrease in the dielectric constant and leakage current as predicted by ab initio calculations. The intercept of the EOT vs physical thickness plot further indicates that increasing the Sr-content at the film interface with the bottom TiN would result in lower interfacial equivalent-oxide thickness.

Metastable perovskite SrxTiyOz (STO) films were formed over a wide composition range by crystallization of layers grown by atomic layer deposition. An expansion of the lattice, decrease in permittivity and mild increase in band gap are observed with increasing Sr content. Sr-rich films [Sr/(Sr+Ti)∼62 at. %] show significant improvement in leakage current at low equivalent oxide thicknesses (EOT) as compared to stoichiometric films (Sr/(Sr+Ti) ∼50 at. %). TiN/STO/TiN capacitors with leakage ∼10−6 A/cm2 at 1 V were obtained at 0.6 nm EOT for crystalline Sr-rich STO. The difference in leakage behavior was found to correlate with different microstructures developed during crystallization.

We demonstrate for the first time record low Leakage-EOT (3.5x10 -7 A/cm 2 at 1V, EOT=0.49 nm) MIM capacitors fabricated using a low temperature (250 o C) ALD SrTiO 3 (STO) deposition process on ALD TiN bottom electrode. While most previous work on STO used deposition techniques not compatible with high aspect ratio DRAM applications, recent work on ALD STO showed promise on noble-like metal electrodes (Ru, Pt) [1,2]. In this work, a low temperature ALD process with alternative precursor set and carefully optimized deposition and processing conditions enables the use of low-cost, manufacturablefriendly TiN electrode MIMcaps for future DRAM nodes. Composition (Sr-rich) and process optimization allowed minimization of interfacial EOT penalties and leakage reduction by decreasing the density of leakier STO grains. IntroductionMIMcaps with EOTs 0.5 nm and low leakage are required for future DRAM nodes. Alternatives beyond ZrO 2 /Al 2 O 3 /ZrO 2 are needed. STO is a promising candidate, but much of previous work focused on nonconformal deposition techniques. As exception, ALD STO using Sr(thd) 2 precursor for Sr has been reported [1,2] with promising results on noble like metal electrodes such as Ru and Pt. However, these processes required either high deposition temperature and/or post-deposition anneals in oxidizing ambients [1,2], making STO incompatible with TiN. By using an alternative ALD precursor system and optimizing carefully deposition variables, composition and post-deposition processing, we demonstrate for the first time excellent results for STO/TiN.

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