Dependence of X-Ray Generation of Interface Traps on Gate Metal Induced Interfacial Stress in MOS Structures

Zekeriya, Viktor; Ma, T.P.

doi:10.1109/tns.1984.4333493

Cited by 76 publications

(9 citation statements)

References 22 publications

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“…This is in contrast to the results reported for the Al-gate samples [6], and may be due to the large Mo-gate induced stress at the Si surface, which is highly compressive, leading to suppression of the time-dependent generation component as described by the gate-iniduced bond strain gradient model [7]. The possible roles that Cl plays (the oxide was grown in 02 + TCA) in modifying the intrinsic stress near the SiO2/Si interface and in its post-radiation defect reactions also can not be ruled out.…”

Section: Discussioncontrasting

confidence: 93%

“…Interface Trap Density Immediately after Irradiation inmediately after irradiation we observe a characteristic peak above midgap in all samples studied ( see dotted curve in Fig.3 as an example ), in agreement with what lias been reported previously for MOS capacitors made with Al and poly-Si gates [2,7]. This peak has been shown to be a convenient measure of the radiation response of MOS capacitors [7]. Figure 1 shows the dose dependence of this peak for Mo-gate MOS samples under three different bombardment biases.…”

supporting

confidence: 91%

“…When there is no gate bias during storage, however, the rate of transformation is the highest, and there is apparently an additional annealing component for peak-1, especially after 10 hours when the peak-2 curve starts to saturate while the peak-1 curve continues to decline. It has been reported that the density of interface traps increases with time at room temperature after irradiation if the gate is biased positively [10,11] or with no bias [7]. In this study, however, we found a very different time dependence of the radiation-induced interface traps in the Mo-gate capacitors.…”

Section: Effects Of Bombardment Biascontrasting

confidence: 61%

“…It has been reported that high temperature anneal causes a relaxation of the high tensile stress in W gate films [8], and it is not unreasonable to expect similar stress relaxation in Mo films. A reduced tensile stress of the gate film corresponds to a reduced gate-induced compressive stress of the silicon surface, which should give rise to an increased radiation sensitivity according to the model proposed by Zekeriya and Ma [7].…”

Section: Methodsmentioning

confidence: 96%

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Radiation-Induced Interface Traps in Mo/SiO2/Si Capacitors

Nishioka

Silva

1987

IEEE Trans. Nucl. Sci.

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The radiation induced interface traps in Moly-gate Metal/SiO2/Si (MOS) capacitors over a wide range of radiation doses have been investigated. The gate oxides in these samples were thermally grown in dry 02+ Trichloroethane (TCA). It has been found that: (1) high temperature (900°C) annealing in H2 after Mo deposition increases the radiation sensitivity significantly, especially for dose levels above 1 Mrad(Si); (2) substantial gate size dependence of the radiation sensitivity is observed in samples without the hydrogen anneal, but not in samples annealed in hydrogen; (3) a characteristic interface trap peak above midgap appears immediately after irradiation, which, along with its background, decreases with tiine after irradiation over a long period (over 1000 hours) at room temperature; (4) the rate of decrease of this peak is a function of the initial damage level, the gate bias during sample storage, and the storage temperature; (5) while this peak is decreasing, a second peak below midgap will develop and grow with time, and the rate of growth of the second peak is correlatable to the reduction of the first peak, suggesting the possibility of defect transformation process at the interface; (6) the defect transformation process is strongly influenced by the gate bias and sample temperature after irradiation; (7) in addition to defect transformation, an annealing component has been observed at room temperature, especially for samples with high densities of interface traps.These results will be discussed in terms of the gate-induced stress near the SiO2/Si interface and the possible effects of clorine (Cl) on the radiation response of MOS capacitors. L. INTRODUCTTONRefractory metal gate technology is being actively developed as a serious competitor for the polycides. Among the various refractory metals, molybdenum is one that holds great potential [1]. Despite its potential importance, however, very little has been done on the radiation response of Mo/SiO2/Si structures.In recent publications, we reported on the time dependent evolution of the interface traps after irradiation or hot-electron damage in MOS capacitors with various gate electrodes [2,3,4]. In general, the post-radiation time dependence of these interface traps has been found to consist of three competing components: (1) generation of additional interface traps, (2) transformation between two interface defects, and (3) defect annealing. This has made the time dependent behavior too complicated to analyze.Fortunately, however, among the moly-gate samples used in this study, which contain gate oxides grown in a dry 02+ Trichloroethane (TCA) ambient, we found that in some cases only the defect transformation process is present, and in others we observed only the transformation and the annealing processes, depending on the bombardment tOn leave from the conditions and the storage bias. In no cases did we observe additional generation in these samples.In this paper, we report our results on the radiation-induced interface traps in these Mo-gate MOS capa...

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Section: Discussioncontrasting

confidence: 93%

supporting

confidence: 91%

Section: Effects Of Bombardment Biascontrasting

confidence: 61%

Section: Methodsmentioning

confidence: 96%

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Radiation-Induced Interface Traps in Mo/SiO2/Si Capacitors

Nishioka

Silva

1987

IEEE Trans. Nucl. Sci.

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“…It has long been thought that arelationship exists between the electrical performance and physical properties of MOS devices. Many workers have studied mechanical stresses in MOS structures and the relationship to radiation damage [1][2][3][4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Observation of radiation induced changes in stress and electrical properties in MOS devices

Shaw

Lowry

MacWilliams

et al. 1992

IEEE Trans. Nucl. Sci.

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Strain measurements using x-ray diffraction were performed on irradiated commercial and radiation hardened metal gate CMOS devices in addition to polysilicon gate NMOS devices. I-V curves were taken and Vot and Vi, were separated using the subthreshold slope method for all devices. A correlation has been shown to exist between physical strain relaxation and the electrical properties as a function of radiation dose and recovery. Data shown suggest that the physical response (strain relaxation) in the silicon at the oxide interface is a measure of the type of damage induced and the recovery mechanism. Post radiation measurements of AVit and AVot taken immediately after irradiation support the conclusions of Zekeriya and Ma and Kasama, et al.; compressive stress at the silicon/SiO, interface does reduce radiation damage in the device. "

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