Breakdown of gate oxides during irradiation with heavy ions

Abstract

Breakdown of thin gate oxides from heavy ions is investigated using capacitor test structures. Soft breakdown was observed for 45 Å oxides, but not for 75 Å oxides. Lower critical fields were observed when experiments were done with high fluences during each successive step. This implies that oxide defects play an important role in breakdown from heavy ions and that breakdown occurs more readily when an ion strike occurs close to a defect site. Critical fields for 75 Å oxides are low enough to allow gate rupture to occur at normal supply voltages for ions with high LET.

Heavy-ion-induced soft breakdown of thin gate oxides

“…1 and 2, it is clear that the postradiation oxide conduction in these thin oxides is a function of both LET and bias (as reported in Ceschia et al [9], [10] and in thicker oxides by Sexton et al [6], [8] and Johnston et al [7]). For both Au and I, the oxides exhibit soft breakdown (SBD) at lower voltages (including 0 V) [8]- [10] and hard breakdown (gate rupture) at voltages greater than 3.5 V. The SBD is indicated by the 10 increase in , increased noise, and the exponential dependence of leakage on (at the higher voltages, -curves appear as nearly straight lines on the log-linear scale).…”

“…Although radiation produces only a modest shift in the threshold voltage of the thin gate oxides used in advanced MOS technology, these thin oxides were still susceptible to radiation effects. In the last few years, pioneering work has uncovered a variety of new radiation-induced effects in thin gate oxides [1]- [10], including radiation-induced leakage current (RILC) in gamma and electron irradiated oxides [1]- [5] and single-event gate rupture (SEGR) [6]- [8] and radiation-induced soft breakdown (RSB) [7]- [10] in oxides exposed to high linear energy transfer (LET) heavy-ion irradiation. Despite this work, the effects of radiation on the reliability of ultrathin oxides ( 4 nm) have not been extensively characterized.…”

Observation of latent reliability degradation in ultrathin oxides after heavy-ion irradiation

“…[1][2][3][4][5][6][7][8][9][10][11] RILC has been observed for heavy ions, x-rays, and electrons with relatively low linear energy transfers ͑LETs͒ between 10 and 40 MeV-cm 2 -mg Ϫ1 . RILC has been modeled as inelastic trap-assisted-tunneling due to neutral oxide defects and was found to be very similar to stress-induced-leakage current ͑SILC͒ observed after constant voltage stress.…”

Growth of heavy ion-induced nanodots at the SiO2–Si interface: Correlation with ultrathin gate oxide reliability

“…In this part of the paper, must be discussed the consequences of such swift heavy ion-induced silicon growth in the SiO 2 bulk on the intrinsic reliability of ultrathin gate oxides. It is well known that thin oxides are susceptible to a variety of radiation effects such as Radiation Soft Breakdown [23], Radiation Induced Leakage Current [24] and Single Event Gate Rupture [25,26]. But despite those recent works, the effects of radiation on ultrathin oxides is not fully understood [27].…”