0.5 nm EOT low leakage ALD SrTiO3 on TiN MIM capacitors for DRAM applications

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 degrees C) ALD SrTiO3 (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, manufacturable-friendly 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

High-k dielectrics and metal gates for future generation memory devices

The requirements and development of high-k dielectric films for application in storage cells of future generation flash and Dynamic Random Access Memory (DRAM) devices are reviewed. Dielectrics with k-value in the 9-30 range are studied as insulators between charge storage layers and control gates in flash devices. For this application, large band gaps (> 6 eV) and band offsets are required, as well as low trap densities. Materials studied include aluminates and scandates. For DRAM metal-insulator-metal (MIM) capacitors, aggressive scaling of the equivalent oxide thickness (with targets down to 0.3 nm) drives the research towards dielectrics with k-values > 50. Due to the high aspect ratio of MIMCap structures, highly conformal deposition techniques are needed, triggering a substantial effort to develop Atomic Layer Deposition (ALD) processes for the deposition of metal gates and high-k dielectrics. Materials studied include Sr and Ba-based perovskites, with SrTiO3 as one of the most promising candidates, as well as tantalates, titanates and niobates