Effects of HCL gettering, CR doping and AL+ implantation on hardened SiO2

It has previously been demonstrated² that the growth conditions of thermal SiO2 can be optimized to give acceptable operating performance for P-MOS devices and circuits after ionizing radiation dose levels of 10⁷ rads and above. Further work has since been done to apply this hardening technology to CMOS circuits, with very promising results. Also studied were the effects of adding HCl gettering, chrome doping, and aluminum ion implantation to the hardened SiO2. Each of these additions, when properly employed, was found to give improved hardening. The nature of these improvements is described in this paper, along with their applicability to the fabrication of CMOS circuits with improved hardness but which retain all the other advantages of the SiO2 gate insulator. Since all process variations were performed in the same laboratory under otherwise identical conditions, the results presented here represent a true comparison of the various hardening techniques.