Charge trapping at the low-k dielectric-silicon interface probed by the conductance and capacitance techniques

Abstract

Trap states close to the interfaces in thin films of porous low-k dielectric materials are expected to affect interfacial barriers with contacts and consequently electrical leakage and reliability in these materials. These interfacial traps were investigated using capacitance and conductance measurements in metal/insulator/silicon capacitor structures composed of carbon-doped oxide low-k dielectric films with gold counterelectrodes. The measurements yielded information on the charge state of the low-k dielectric and an estimated density of traps near the Si interface of 2 ϫ 10 11 cm −2 eV −1 , considerably greater than in typical SiO 2 films. The effects of temperature and annealing were also investigated. An activation energy of 0.36Ϯ 0.04 eV for trap filling and emptying was inferred.

The effects of plasma exposure and vacuum ultraviolet irradiation on photopatternable low-k dielectric materials

“…4 Previous work on porous low-k materials has demonstrated that plasma exposure can adversely affect the capacitance, breakdown voltage, and leakage currents of these dielectrics, 5,6 and can also significantly reduce time-dependent dielectric breakdown (TDDB) lifetimes. 7 In particular, the slope of the IV characteristics has been found to be related to the Weibull statistics slope of TDDB characteristics in low-k dielectrics.…”

Effect of vacuum ultraviolet and ultraviolet Irradiation on capacitance-voltage characteristics of low-k-porous organosilicate dielectrics

“…The trapped charges reduce the interface energy barrier by acting as low-energy conduction pathways. 6 Photoinjected electrons from silicon can travel in the dielectric and recombine with positive trapped charges there. Thus, photoinjection can repopulate the defect states with electrons resulting in depletion of the trapped positive charges.…”

“…The Si-SiCOH interface has an energy barrier of 4 Ϯ 0.5 eV. 6 As a result, only electrons in silicon with energies greater than 4.5 eV can be injected into SiCOH. The photoinjection is further enhanced by the presence of trapped charges in SiCOH at the interface.…”

Bandgap measurements of low-k porous organosilicate dielectrics using vacuum ultraviolet irradiation

“…Electrons dominate photoconduction, photoemission, and photoinjection, since the mobility of electrons is larger than the mobility of holes. 3 When the energy supplied by irradiation is greater than the sum of the band-gap energy and the electron affinity, photoemission can occur from the dielectric. 2 Photoemission can take place by electrons ejected from either the valence band or the defect states present in the dielectric.…”