Ferroelectricity Enhancement in Hf0.5Zr0.5O2 Based Tri-Layer Capacitors at Low-Temperature (350 degrees C) Annealing Process

Abstract

The use of additional dielectric (DE) layers such as Al2O3, ZrO2, HfO2 and Ta2O5 with Hf0.5Zr0.5O2 (HZO) ferroelectric (FE) layer, namely bi-layer systems are drawing much attention in the recent past due to enhanced FE properties and their applications in memory technology. However, HZO based tri-layer capacitors with various DE layers are not yet reported. The present paper demonstrates the enhanced FE properties of MFM tri- layer capacitors were found at low temperature (350 degrees C) using rapid thermal annealing (RTA) process. Various tri-layer capacitors were fabricated by changing top dielectric layers such as TiO2, ZrO2 and SiO2 (thickness of 10 angstrom) while keeping FE HZO (100 angstrom) and bottom HfO2 DE layer (10 angstrom) as constant and traditional P-E curves for all those tri-layer (DE/FE/DE) capacitors were observed. Among all the tri-layer capacitors, highest remanent polarization (P-r similar to 16.6 mu C/cm(2)) was observed for the TiO2 top DE at 350 degrees C. The addition of top DE layers induced strain in the FE film due to their different thermal expansion coefficients and as a resulting in enhancing o-phase. The demonstration of excellent ferroelectric property by the as fabricated metal-ferroelectric-metal (MFM) capacitors with crystallization temperature as low as 350 degrees C can be of significant importance in sensor and display applications.