Study on the crystallization mechanism and microstructural characterization of In-Sb-Te Thin films using transmission electron Microscopy

Abstract

Phase change random access memory (PRAM) based on chalcogenide alloys has been attracted much attention for next generation non-volatile memory due to its fast operation, high scalability, and low fabrication costs. The remarkable characteristic of PRAM materials is a reversible phase transformation, which has different electrical properties between amorphous and crystalline phases. That is, the amorphous state has a relatively high resistivity, whereas the crystalline state has a low resistivity. Among the chalcogenide materials, Ge-Sb-Te (GST) is well known as recording material of phase change memory device due to a fast speed of transformation and a good stability of the amorphous phase. In spite of these advantages, there is an increasing demand to improve power consumption and density storage. To solve the issues, many researchers have focused on the new chalcogenide materials such as Si-Sb-Te, Ga-Sb-Te, Al-Sb-Te. In this point of view, we investigated In-Sb-Te phase change material for PRAM. In previous reports, In-Sb-Te phase change material has four different resistance states for multi-bit storage of PRAM. The respective phases corresponding to multilevel states were also confirmed. However, a high-resolution TEM (HRTEM) study on an atomic level was little investigated for the crystal structure and atomic arrangement of In-Sb-Te phase change material. Furthermore, it is important to understand the microstructure of In-Sb-Te ternary alloy for phase change performance which is phase transformation behavior and nucleation-growth mechanism. The crystallization behavior and microstructural characteristics of In-Sb-Te thin film have been investigated using XRD and TEM analysis. The compositional analysis and structural characterization is conducted on series of annealed In-Sb-Te ternary phase change material. AES analysis shows that In and Sb contents of film are a little more than Te atom in as-deposited In-Sb-Te thin film. It is deviated from the peritec...