• PDF / 315,517 Bytes
• 6 Pages / 612 x 792 pts (letter) Page_size
• 53 Downloads / 202 Views

DOWNLOAD

REPORT

---

F3.25.1

NEW NANOCRYSTALLINE Si FLOATING GATE STRUCTUE FOR NONVOLATILE MEMORY APPLICATION L.C. Wu, J.J. Shi, K.J. Chen, J. Xu, W. Li, Z.Y. Ma, M. Dai, D. Wu, A.D. Li, X.F. Huang National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, CHINA ABSTRACT We report a direct experiment evidence for holes and electrons charging in a new nanocrystalline Si (nc-Si) floating gate structure (SiO2/nc-Si/SiO2/c-Si) fabricated in-situ by plasma oxidation and layer by layer deposition technique in a plasma enhanced chemical vapor deposition (PECVD) system. In this nc-Si floating gate structures, the thickness of tunneling SiO2 layer is about 2 nm and the mean grain size of nc-Si is 6 nm obtained from Raman scattering and AFM measurements. The discrete quantum level and Coulomb charging energy for a single electron have been observed in large ensemble of nc-Si dots by frequency dependent capacitance spectroscopy, which demonstrates that the Coulomb blockade for electron in nc-Si dots is larger than size fluctuation effects on the quantum confinement for our nc-Si floating gate structure. Quantitatively, the experiment results of capacitance spectroscopy are in good agreement with the theoretical calculations. By contrasted with silicon single electron transistor memory made by using ultra fancy nanotechnology, nc-Si based memory can be fabricated with a minimum perturbation of conventional silicon technology and may be closest to industrial application. INTRODUCTION A room-temperature nanocrystalline Si (nc-Si) based memory was first reported by IBM research division.1 The memory structure is a single field effect transistor (FET) with nc-Si floating gate. The devices utilize direct tunneling and storage of electrons in three-dimensionally confined nanocrystals. Based on the Coulomb blockade principle in the limited capacitance of the nanocrystals, the transfer of a single electron,2 and a memory operation with a small number of stored electrons have been demonstrated.3,4 By contrasted with silicon single electron transistor memory made by using ultra fancy nanotechnology,5,6 nc-Si based memory can be fabricated with a minimum perturbation of conventional silicon technology and may be closest to industrial application. For nc-Si based memory, the quantum confinement effect and Coulomb blockade effect in nc-Si floating gate were suggested to be crucial for the operation of device. However, the role of energy states including discrete quantum states and interface gap states in the nc-Si dot has not been fully understood. The purpose of this work is to demonstrate the experiment evidence of tunneling and storage of electrons in nc-Si floating gate by capacitance spectroscopy and to investigate the effect of discrete quantum states and interface states on the storage of electrons in

F3.25..2

the nc-Si floating gate. EXPERIMENTAL DETAILS The nc-Si floating gate structure used for this study is fabricated in-situ in a plasma enhanced chemical vapor deposition (PECVD) system. Figu