| Budget Amount *help |
¥8,900,000 (Direct Cost: ¥8,900,000)
Fiscal Year 1985: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1984: ¥7,800,000 (Direct Cost: ¥7,800,000)
|
|---|
| Research Abstract |
New techonology has been developed for improvement of silicon on sapphire (SOS) as an MOS VLSI substrate. Effects of fluorine ion ( <F^+> ) implantation on SOS and the improvement of electrical characteristics of SOS MOSFETs have been investigated.
It has been found that the <F^+> implantation into SOS forms a deep acceptor level in Si films, and that the nature of this acceptor level is affected by the sequence of the <F^+> implantation and gate oxidation in device fabrication process. In the case of <F^+> implantation before gate oxidation, the induced acceptor level density is high, but the electron mobility is not much influenced. Moreover, the mobility in the interface region is found a tendency to increase. On the other hand, in the case of <F^+> implantation after oxidation, the induced density is low, but the mobility is strongly affected. The energy levels of these traps in the former and the latter cases are located at 0.49eV and 0.21eV below the conduction band edge, respectively.
Drain leakage currents of <F^+> -implanted samples for both the cases are reduced to 0.1-0.5 times as large as as-grown samples, and decrease with increasing the implanted ion energy. Furthermore, it is found that the leakage currents of <F^+> -implanted samples are independent of the gate length, whereas those of as-grown samples rapidly increase with decreasing the gate length. It can be thought from the above results that F atoms make dangling bonds in the Si-sapphire interface inactive, so that the leakage current through the interface is reduced.
In conclusion, the method developed in the present work provides us the improvement of MOS device characteristics such as the mobility and the drain leakage current. This improvement is essential to realize a submicron MOSFET because the leakage current prevents MOS devices making minute at present.
|
