Low leakage ZrO2 based capacitors for sub 20 nm dynamic random access memory technology nodes

Abstract

During dynamic random access memory (DRAM) capacitor scaling, a lot of effort was put searching for new material stacks to overcome the scaling limitations of the current material stack, such as leakage and sufficient capacitance. In this study, very promising results for a SrTiO3 based capacitor with a record low capacitance equivalent thickness value of 0.2 nm at target leakage current are presented. Due to the material properties of SrTiO3 films (high vacancy concentration and low band gap), which are leading to an increased leakage current, a physical thickness of at least 8 nm is required at target leakage specifications. However, this physical thickness would not fit into an 18 nm DRAM structure. Therefore, two different new approaches to develop a new ZrO2 based DRAM capacitor stack by changing the inter-layer material from Al2O3 to SrO and the exchange of the top electrode material from TiN to Pt are presented. A combination of these two approaches leads to a capacitance equivalent thickness value of 0.47 nm. Most importantly, the physical thickness of <5 nm for the dielectric stack is in accordance with the target specifications. Detailed evaluation of the leakage current characteristics leads to a capacitor model which allows the prediction of the electrical behavior with thickness scaling.

Analysis of Performance Instabilities of Hafnia‐Based Ferroelectrics Using Modulus Spectroscopy and Thermally Stimulated Depolarization Currents

“…This composition maintains full process compatibility with the CMOS technology . Both oxides are already used in high‐ k metal gate and DRAM processes and can be deposited by the well‐developed atomic layer deposition (ALD) technique. This allows conformal depositions onto 3D structures for state‐of‐the‐art technology nodes…”

Effect of Growth Temperature on the Structural and Electrical Properties of ZrO2 Films Fabricated by Atomic Layer Deposition Using a CpZr[N(CH3)2]3/C7H8 Cocktail Precursor

“…These favorable properties have led to commercial use of ZrO 2 thin films as dielectrics and insulators in a variety of microelectronics applications, such as dynamic random access memory [2], radio-frequency and analog/mixed-signal (RF/AMS) integrated circuits [3,4], and non-volatile resistive random access memory [5]. …”

Nonvolatile Random Access Memory and Energy Storage Based on Antiferroelectric Like Hysteresis in ZrO2

“…To assess the structural properties of the two ZrO 2 layers Grazing Incidence X‐ray diffraction (GI‐XRD) diffraction and scanning electron microscopy (SEM) was performed after the removal of the top electrode ( Figure ). Since simulation results by Materlik et al suggest that the surface energy of the grains has a strong impact on the phase formation, a similar grain radius should result in a similar phase composition. For verification, XRD measurements were performed and compared to the patterns for the monoclinic and tetragonal phases of ZrO 2 (Figure a lower part).…”

“…Metal‐insulator‐metal (MIM) capacitors with TiN electrodes and ZrO 2 /Al 2 O 3 /ZrO 2 (ZAZ) dielectric stacks were applied in commercial DRAM products from the 80 nm node to current 18 nm generations during the last decade . In a study by Pešić et al, it was shown how the existing production type ZAZ layers can be implemented in sub 18 nm nodes.…”