Photoelectron Effects on the Dose Deposited in MOS Devices by Low Energy X-Ray Sources

Radiation induced charge trapping in ultrathinHfO 2 -based n-channel MOSFETs is characterized as a function of dielectric thickness and irradiation bias following exposure to 10 keV X-rays and/or constant voltage stress. Positive and negative oxide-trap charges are observed, depending on irradiation and bias stress conditions. No significant interface-trap buildup is found in these devices under these irradiation and stress conditions. Enhanced oxide-charge trapping occurs in some cases for simultaneous application of constant voltage stress and irradiation, relative to either type of stress applied separately. Room temperature annealing at positive bias after irradiation of transistors with thicker gate dielectric films leads to positive oxide-trapped charge annihilation and/or neutralization in these devices, and net electron trapping. The oxide thickness dependence of the radiation response confirms the extreme radiation tolerance of thin HfO 2 dielectric layers of relevance to device applications, and suggests that hole traps in the thicker layers are located in the bulk of the dielectric. A revised methodology is developed to estimate the net effective charge trapping efficiency, , for high-dielectric films. As a result, estimates of for Hf silicate capacitors and Al 2 O 3 transistors in previous work are reduced by up to 18%.Index Terms-Constant-voltage-stress (CVS), Hafnium oxide (HfO 2 ), high-, metal-oxide-semiconductor-field-effect-transistors (MOSFETs), radiation damage, recovery, ultrathin, X-ray.

Section: Effective Charge Trapping Efficiencymentioning

confidence: 70%

Section: Effective Charge Trapping Efficiencymentioning

confidence: 99%

Radiation Induced Charge Trapping in Ultrathin ${\rm HfO}_{2}$-Based MOSFETs

Dixit

Zhou

Schrimpf

et al. 2007

“…For oxide thicknesses comparable to the photoelectron range (tox < 100 nm), Rde(10 keV)/Rde(l.25 MeV) is expected to be about 1.7 [10]. The net result is that substantial differences could be expected between lowand high-energy-photon irradiations of MOS devices.…”

Section: Analysis Of the Components Of Charge Generationmentioning

confidence: 99%

The Relationship between 60Co and 10-keV X-Ray Damage in MOS Devices

Benedetto

Boesch

1986

178

This paper presents a conduction current technique to separate the effects of fractional charge yield and dose enhancement in metal-oxide semiconductor (MOS) devices in a 1O-keV x-ray environment. The results of the conduction current measurements, together with the concept of charge generation as the damage-producing agent, are used to correlate the threshold-voltage shifts in gate-and field-oxide MOS field-effect transistors irradiated with 60Co and a 10-keV x-ray machine. A straightforward procedure for calculating the equal6,gamage dose equivalence between the 1O-keV x-ray and Co sources is also presented. 1.

“…The higher the effective Z of the metal gate, the greater is the dose enhancement, relative to [1], [2], [10], [11]. We choose this layer structure and comparison because equilibrium dose in is frequently used to report x-ray dose in studies [27], [28] of the radiation response of high-gate dielectrics. The decrease in "excess dose" in the for thinner dielectric layers occurs because much of the energy initially deposited in this higher-Z layer transports (via secondary electrons) to surrounding lower-Z materials.…”

Section: B Mredmentioning

confidence: 99%

“…First we show calculations for a simplified model structure (Fig. 5) that is similar to one that has been employed in previous studies of the effects of high-Z materials on single-event effects [28]- [30] and then for a more realistic BEOL process. Fig.…”

Section: Effects Of Back-end-of-line Layers: 10-kev X-raysmentioning

confidence: 99%

Effects of Metal Gates and Back-End-of-Line Materials on X-Ray Dose in ${\rm HfO}_{2}$ Gate Oxide

Dasgupta

Fleetwood

Reed

et al. 2011

The effects of 10-keV and 400-keV endpoint-energy bremsstrahlung x-rays have been studied using the Monte Carlo simulator, MRED, for MOS capacitors with gate dielectrics and TiN and TaN metal gates. We compute the reduction in dose that occurs for 10-keV x-ray irradiation of thin gate dielectrics sandwiched between the metal gate and the Si substrate. We quantify the effects of back-end-of-line metallization layers, including copper interconnects, W vias, and borophosphosilicate glass (BPSG) and passivation layers for low and medium energy x-rays. For thick metallization stacks irradiated by 10-keV x-rays, dose enhancement or attenuation can occur, depending on material type and overlayer thicknesses. For similar stacks irradiated with 400-keV endpoint-energy bremsstrahlung x-rays, significant dose enhancement is observed. Index Terms-Dose enhancement,, high-, Monte-Carlo Radiative Energy Deposition (MRED), MOS capacitors, .