EFFECTS OF THE INTEGRITY OF SILICON THIN-FILMS ON THE ELECTRICAL CHARACTERISTICS OF THIN DIELECTRIC ONO FILM

Capacitors with two kinds of lower electrodes were fabricated and thei r effects evaluated on the electrical characteristics of oxide-nitride -oxide (ONO) film. One of the electrodes was made of amorphous silicon film chemically deposited using a gas mixture of Si2H6PH3; the other was made of poly-Si film deposited by SiH4 decomposition and doped by As+ ion implantation. The ONO thin dielectric layer was composed of na tural oxide, CVD silicon nitride and thermal oxide formed on the silic on nitride. The capacitance, the leakage current, the dielectric break down field and the time-dependent dielectric breakdown (TDDB) were tes ted to evaluate the electrical properties of the capacitors. The leaka ge current and the dielectric breakdown voltage showed similar values between the two capacitors, whereas the TDDB under negative bias showe d a great difference. This indicates that, with respect to electrical properties, the integrity of the oxide grown on the in situ P-doped am orphous silicon is better than the oxide grown on the As+ ion-implante d poly-Si. What is more, phosphorus in the amorphous silicon did not l ead to any problems with junction depth, even after post heat treatmen t at 950 degrees C.