The fixed oxide trap modelling during isothermal and isochronal annealing of irradiated RADFETs

Abstract

The density of fixed traps (FTs), ΔN ft (cm−2), during isothermal annealing of irradiated radiation-sensitive field-effect transistors (RADFETs) from room temperature to 200 °C has been modelled. The modelling has shown that a simple, two-defect model (2DM), containing two defect types: one defect type for positively charged FTs (PCFTs), and another for negatively charged FTs (NCFTs), is applicable for the temperatures up to 100 °C. However, the three-defect model (3DM), which includes additional PCFT type, should be used for temperatures from 100 to 200 °C. The models describing the behaviour of NCFTs during isothermal annealing have also been analysed. The activation energies of , and , for two PCFT types and one NCFT type, respectively, have been found. In addition, isochronal unannealed curves have been well fitted using logistic function. The modelling of isochronal annealing has also shown that one PCFT type up to 100 °C, and two PCFT types for 100–200 °C, respectively, are active, and additional defect(s) should be included for the temperatures higher than 200 °C. The isochronal annealing, which is significantly less time consuming than isothermal annealing, could be very good tool for the revealing of defects created by various stress types.

Fading of pMOS dosimeters over a long period of time

“…To fit the ΔV ft , i.e. ΔV T , during SA, we will use the model for the annealing of radiation-induced defects developed in reference [7], which is confirmed in other experiments [8,10]. Using Equations ( 8)- (10) from reference [7] and reactions (7) and (8), the dependence of densities of E 𝛾 , N E 𝛾 (t ), and of E s , N E s (t ), respectively, on time during SA, can be obtained as follows: where N E 𝛾 (0) and N E s (0) are the densities of E γ and E s after irradiation, i.e.…”

“…Also, the values of fading for V G,i = 5 V are similar for both oxide thicknesses. Here it should be noted that the case without an external voltage on the gate (V G,i,a = 0) of Al-gate pMOSFETs corresponds to a small internal positive voltage on the gate of V wf = 0.33 V due to the difference in a work function between the Al-gate and n-type silicon substrate, resulting in small external positive electric field in the gate oxide [8].…”

Radiation sensitive MOSFETs irradiated with various positive gate biases

“…The remaining two gate biases show the same behavior (not shown). It can be concluded that the annealing of fixed traps determines fading (Ristić et al, 2012).…”

Neutron‐gamma dosimetry for BNCT using field oxide transistors with gadolinium oxide as neutron converter layer

“…20 Since the total dose sensitivity of an MOS transistor increases with the gate oxide thickness, 21 MOS dosimeters are built with thick gate oxides. [22][23][24][25] However, to fabricate them sufficiently thick, ad hoc processes are needed leading to an increased manufacturing cost. To be able to produce these dosimeters in standard complementary metal-oxide-semiconductor (CMOS) processes with high dose sensitivity, the FOX field effect transistor (FOXFET) dosimeter has recently been proposed.…”

“…MOS dosimeters are MOS transistors in which the accumulative threshold voltage shift ($$\Delta V_T$$) is used to quantify the absorbed dose 20 . Since the total dose sensitivity of an MOS transistor increases with the gate oxide thickness, 21 MOS dosimeters are built with thick gate oxides 22–25 . However, to fabricate them sufficiently thick, ad hoc processes are needed leading to an increased manufacturing cost.…”