METHOD OF SELECTING CMOS/SOI TRANSISTOR STRUCTURES RESISTANT TO EFFECT OF FULL ABSORBED DOSE OF IONISING RADIATION Russian patent published in 2012 - IPC G01R31/26 

FIELD: physics.

SUBSTANCE: in the method of selecting CMOS/SOI transistor structures which are resistant to the effect of full absorbed dose of ionising radiation, for each process solution, an additional pair of n- and p-channel transistor channels made from the same technology is formed on the chip along with the main LSI circuit; for limited sampling, LSI specimens are removed discretely with a step of about 100 krad(Si) in the TID range from zero to the level of requirements for resistance of the LSI to the effect of maximum TID plus 20% of the relationship I_D=f(V_Gs); data are obtained therefrom on change in shift of threshold voltage ΔV_TH from the TID value through a dose of not less than about 1000 rad(Si)·s^-1 taking into account manufacturing tolerance and possible boundaries of variation of the relationship V_TH(TID); lower and upper allowable boundaries of relationships V_TH(TID) of transistors of both conductivity types are approximated; the dispersion of measured values is determined for each fixed TID value; the value ΔV_TH(↑↓) without exposure is determined for the minimum on the curve for an n-channel transistor and for the virtually achieved maximum level of exposure; ΔV_th(↑↓) is determined for the same conditions for all possible combinations of differences "V_Th(TID)-Up" and "V_th(TID)-Down" of n-MOS and p-MOS transistors, ΔV_th(↑↓) is determined for three fixed LSI TID values; the LSI are ranked on four gradations of the observed values of ΔV_th(↑↓): "high" ("1") - maximum change; "significant" ("2") - strong change; "average" ("3") - moderate changes; "low" ("4") - weak changes, which on the average value are sorted as "1"%:"2"%:"3"%:"4"%, where the "low" gradation is taken as 100%; ΔV_th(↑↓) is measured for non-exposed industrial LSI specimens and the results of ranking exposed specimens are used to determine the possibility of using in exposure conditions those specimens for which the gradation of change in the value of ΔV_th(↑↓) corresponds to categories "4" and "3".

EFFECT: possibility of selecting industrial LSI which are resistant to TID effects without conducting an exposure experiment to measure radiation drift of threshold voltage ΔV_th.

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