| AVS 63rd International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF-ThP |
| Session: | Thin Films Poster Session |
| Presenter: | Sang Hyeon Kim, Samsung Electronics, Republic of Korea |
| Authors: | S.H. Kim, Samsung Electronics, Republic of Korea C.S. Hwang, Seoul National University, Republic of Korea |
| Correspondent: | Click to Email |
Dynamic random access memory (DRAM) plays the role as main memory in computers and mobile electronic devices. Further evolution of DRAM requires increase in change density of capacitors. However, the currently using ZrO2/Al2O3/ZrO2 stacked dielectric layer is facing its limitation for further scaling due to the increased leakage current. Thus, perovskite structured SrTiO3 (STO) material is attracting great attention as a future dielectric material in DRAM capacitors. Atomic layer Deposition (ALD) is the most suitable method for DRAM capacitor application which requires excellent conformality on complicated three-dimensional structure with an aspect ratio of 100:1.
ALD of STO films has been researched at a high growth temperature of 370 °C in a series of investigations by the authors’ group in order to achieve in-situ crystallization. (1),(2) However, abnormally too high growth rate at initial stage of film growth on Ru electrode, which is the most probable electrode material, was observed,(2) due to the involvement of CVD-like growth behavior. In this study, therefore, 1.5-nm very thin seed layers were deposited under low temperature to make dense seed layers. As a result, the dielectric constant was improved from ~160 to ~270 which was one of the best results of the STO dielectric material. STO films were deposited in a traveling-wave-type ALD reactor (CN-1 Co, Plus-100) for a 4-in.-diameter single wafer. Sr(iPr3Cp)2 and Ti(Me5Cp)(OMe)3 (synthesized by Air Liquide) were employed as the Sr and Ti precursors, respectively. H2O and high density (250g/m3) O3 were employed as oxygen source for SrO and TiO2 sublayers, respectively. The ALD saturation curve was confirmed in SrO and TiO2 deposition, and the deposition showed a linear growth behavior with respect to the number of deposition cycle with no indication of abnormal growth at the initial stage. In STO deposition, cation composition (Sr/(Sr+Ti)) was evaluated from 50% - 70%. Electrical properties of the (top) RuO2 / STO / Ru (bottom) planar capacitor were estimated to confirm the feasibility of the next generation DRAM capacitor applications.
(1) Woongkyu Lee et al., Chem. Mater.2015, 27, 3881-3891.
(2) Woongkyu Lee et al., Chem. Mater. 2013, 25, 953-961.