Materials and processing parameters affecting the radiation tolerance of SIMOX devices

It is shown that the hardness of N-channel transistors fabricated on separation by implantation of oxygen (SIMOX) material is a function of the concentration of heavy metals in the SIMOX material. Three oxygen implant lots were used to fabricate N-channel MOS transistors having gate lengths of 5 μm and gate widths of 100 μm. The initial pre-radiation leakage currents for the devices fabricated on the three materials were 3×10^-9, 1×10^-10, and 1×10^-11 A respectively. Both the pre-radiation and post-radiation back-channel leakage currents for transistors exposed to 100 KRad (Si) dose of ionizing radiation are a strong function of the heavy-metal contamination levels. The changes in back-channel leakage current from pre-rad to post-rad indicate the strong effect of heavy-metal contamination on the radiation tolerance of N-channel MOS devices. The effect of post implant anneal temperature on the back bias induced leakage current is also investigated