Spectrum analysis of electroluminescence from MOS capacitors with Si-implanted SiO<inf>2</inf>

Abstract

A device with Si rich gate oxide has attractive characteristics such as visible electroluminescence (EL) and current-voltage (I-V) hysteresis. Consequently, the MOS devices with Si-implanted SiO 2 have potentiality to integrate both the EL device and the high density Non-volatile memories on a single Si CMOS LSI chip [1,2]. Though visible EL from Si-implanted MOS capacitors have been reported [3,4], EL mechanisms and effects of process conditions still need further studies. In this work, spectrum analysis of EL from Si-implanted MOS capacitors is presented and effects of Si implantation and annealing conditions are discussed for EL mechanism. Fig. 1 gives a schematic cross section of a MOS capacitor with Si-implanted gate SiO 2 . The 30 nm thick thermal SiO 2 was grown on an n + -type (100) Si substrate of 0.02 cm (10 18 cm -3 ). Si ions were implanted into the SiO 2 , followed by N 2 annealing at 900 or 1000 °C for 30 min. The aluminum film was formed on the backside for ohmic contact. Finally, 15 nm thick Au film of 1.5 mm in diameter was sputter-deposited on the SiO 2 as a transparent electrode. Eight kinds of Siimplanted MOS capacitors and reference samples without implantation were fabricated as shown in Fig. 2. Similar I-V and C-V characteristics to the previous results are obtained [3,4]. The EL measurement system consists of a monochromator and a CCD camera cooled at -70 °C. The EL spectrum data were corrected for the total wavelength response curve of the system. EL spectra were measured under the constant gate currents (J G ) for the accumulation conditions. Fig. 3 shows measured EL spectra for n5b-L and n5b-H, which have different annealing temperature of 900 and 1000 °C, respectively. Both devices give similar and the highest peak at photon energy of about 2.7 eV (blue EL of 460 nm wavelength). The effect of annealing temperature on EL spectra is relatively small for the measured devices. Fig. 4(a) -(d) shows EL spectra for the devices implanted by the different energy and Si dose. The solid lines in Fig. 4 shows the calculated curves fitted by five Gaussian