Materials Science and Engineering B69 – 70 (2000) 295 – 298 Correlation of dot size distribution with luminescence and electrical transport of Si quantum dots embedded in SiO 2 S. Lombardo a, *, S. Coffa a , C. Bongiorno a , C. Spinella a , E. Castagna a , A. Sciuto a , C. Gerardi b , F. Ferrari b , B. Fazio b , S. Privitera c a Istituto Nazionale di Metodologie e Tecnologie per la Microelettronica (IMETEM), Consiglio Nazionale delle Ricerche, stradale Primosole, 50, I -95121 Catania, Italy b Central R&D, Catania Technology Center, STMicroelectronics, stradale Primosole, 50, I -95121 Catania, Italy c Dipartimento di Fisica, Uniersita ` di Catania, corso Italia, 57, I -95129 Catania, Italy Abstract We have investigated the electrical transport and luminescence of Si dots embedded in SiO 2 . The dots have been obtained by high temperature annealing of silicon rich oxides prepared by chemical vapor deposition. Transmission electron microscopy analysis demonstrates the presence of crystalline Si dots with grain radii down to 1 nm. The data of luminescence and electrical transport appear correlated with the dot size distribution. Moreover, the analysis of the electrical characteristics of metal-oxide – semiconductor capacitors with silicon rich oxide films indicates that such systems may reversibly store charge, thus exhibiting the function of a memory. © 2000 Elsevier Science S.A. All rights reserved. Keywords: Si dots; Electrical transport and luminescence; Reversible charge storage www.elsevier.com/locate/mseb 1. Introduction The evolution of memory devices such as non- volatile Electrically Erasable Programmable Read Only Memory (EEPROM) devices and flash memories is characterized by continuous cell scaling and it requires increasing endurance to write/erase cycling and multibit storage. To achieve such objectives, memory cells char- acterized by a gate insulator with silicon quantum dots have recently been proposed [1 – 5]. In such structures the Si dots are embedded in SiO 2 and they are used to achieve charge storage, replacing the standard floating gate of polycrystalline Si. The occurrence of single electron effects and in particular of Coulomb blockade has been demonstrated, thus increasing the interest toward such systems. Silicon rich oxide (SRO) is an interesting candidate material to obtain the embedded Si dots. Indeed, SRO is considered a solid solution of Si and SiO 2 supersaturated with Si, and in which under high temperature annealing the excess Si atoms precipi- tate in the form of Si dots ( see Ref. [6] and references therein). The kinetics of Si precipitation has been at- tributed to the diffusion of Si atoms in the Si:O amor- phous matrix [7]. In this work we have investigated the shape of the dot size distribution in thin SRO films after high tem- perature furnace processing. Data of photolumines- cence and measurements of electrical conductivity as a function of temperature are presented and related to the dot size distribution present in the SRO materials. Finally, electrical data concerning the occurrence of charge storage in the dots are presented and discussed. 2. Experimental SRO films have been prepared on oxidized Si sub- strates either by low pressure chemical vapor deposition (LPCVD) of SiH 4 and N 2 O at 620°C or by plasma enhanced chemical vapor deposition (PECVD) of SiH 4 and O 2 at 500°C. Rutherford backscattering spectrometry (RBS) of 2 MeV 4 He + ions was used to determine the thickness and the O/Si ratio of the SRO films. To determine the concentration of impurities (nitrogen in particular), sec- ondary ion mass spectrometry (SIMS) analyses were performed by using a 5.5 keV Cs + primary ion beam. * Corresponding author. Tel.: +39-095599623; Fax: +39- 0957139154. E-mail address: lombardo@imetem.ct.cnr.it (S. Lombardo) 0921-5107/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved. PII:S0921-5107(99)00290-1