Noise characteristics of ion-implanted MOS transistors

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Abstract
Low‐frequency excess noise characteristics of ion‐implanted MOS transistors annealed above 1000 °C were investigated. Noise characteristics strongly depended on implant species, implant condition, and measurement conditions. In the case of implantation into opposite‐type conductivity substrates, such as 11B+‐implanted p‐channel or 31P+‐implanted n‐channel transistors, the equivalent input noise voltages measured at lower drain currents exhibited generation‐recombination (G‐R) noise caused by residual damage in the substrate. This noise component increased with increasing acceleration energy or implant dose. The G‐R noise decreased with increasing drain current. At higher drain currents the G‐R noise disappeared and the noise voltages of the implanted samples were somewhat smaller than that of the unimplanted samples. On the contrary, in the case of implantation into the same‐type conductivity substrate, such as 31P+‐implanted p‐channel or 11B+‐implanted n‐channel transistors, no G‐R noise component was observed and noise voltages increased with increasing dose. The difference was also observed in the surface recombination velocity measurements. These results could be attributed to the difference in the position of the carrier path due to the change of surface band bending. The G‐R noise could not be removed by heat treatment up to 1200 °C. It was confirmed that there were no dose rate dependences within the range 0.1–10 nA/cm2.