Masaichi Shinoda

Thermally grown silicon nitride films for high‐performance MNS devices

Amorphous and uniform silicon nitride films with thicknesses of less than 100 A have been thermally grown on silicon wafers by employing purified ammonia gas. The films are much denser than conventional CVD Si3N4 films. The MNS (metal‐thermal nitride‐silicon) structures have very low Nss in the order of 3×1010 cm−2 eV−1 and an effective electron mobility of larger than 800 cm2/V sec in the fabricated n‐channel MNSFFT.

A normally-off type buried channel MOSFET for VLSI circuits

This paper presents the performance of a buried channel MOSFET (BC-MOSFET) that uses the bulk region as the conducting channel in contrast with the surface channel of the conventional device. Normally-off characteristic has been realized with the p-type silicon gate and the ion-implanted n-channel layer. Fabricated short channel BC-MOSFETs with the gate lengths of 1-3 µ have shown a small shift of threshold voltage with changing the gate length or drain bias. These devices also have high carrier mobility of 750 cm2/v.s and high breakdown voltage compared with those of the conventional device. Minimum delay time of 180 ps was obtained with a 13 stage ring oscillator which was constructed with 1 µ BC-MOSFET.

Interfacial Doping by Recoil Implantation for Nonvolatile Memories

Recoil implantation has been found suitable for a very shallow doping in insulator. The number of recoil-implanted atoms is precisely controlled by implanted ions. Recoil-implanted tungsten atoms act as electron and hole traps. The n-channel nonvolatile memory MNOS FET has been realized by utilizing the traps as memory sites. Shifts in threshold voltage has been accurately controlled by introducing recoil-implanted tungsten atoms of more than 1014 cm-2.

10 V Write/Erase, EAROM cells with directly nitrided silicon nitride films as first insulating layers

Writing and erasing voltages of an electrically alterable nonvolatile memory (EAROM) have been decreased to 10 volts by employing a silicon nitride film grown by directly thermal nitridation of a silicon substrate as the first insulating layer of a stacked-gate structure. Memory retention, writing and erasing repetition, continuous reading-out and programing time have been excellently improved when these are compared with conventional erasable programable ROMs.