Characteristics of leakage current in the dielectric layer due to Cu migration during bias temperature stress

Abstract

The dielectric breakdown by Cu ion migration under applied bias is important for the reliability of damascene Cu interconnects as well as Cu through-hole bias in three-dimensional interconnects. The mechanism responsible for the leakage current through the dielectric during bias temperature stress is investigated in Cu/SiO2 and Al/SiO2 metal-insulator-semiconductor samples. When a constant electric field is applied, a gradual increase in leakage currents was observed in the case of Cu/SiO2, but no increase in leakage current before failure was observed for Al/SiO2. The voltage ramping tests conducted on the samples before and during the constant electric field application showed that the increase in leakage current in the Cu/SiO2 sample is by the Poole–Frenkel (PF) conduction mechanism. Cu ions, which migrate into the dielectric under the applied field, act as trap sites for PF conduction. This was confirmed by negative bias test as well as simulation of the leakage current by one-dimensional finite differential methods.

Dielectric Breakdown in Chemical Vapor Deposited Hexagonal Boron Nitride

“…SiO 2 , HfO 2 , Al 2 O 3 ). [2][3][4][5][6] In these oxides the percolation model is the most accepted theory for BD formation, and it states that the insulating capability is lost due to the formation of a defective conductive nanofilament (CNF) connecting the two sides of the dielectric. 7 When the last defect that forms the filament is trapped the local currents increase sharply several orders of magnitude, leading to the accumulation of thermal heat at the BD site.…”

“…7 When the last defect that forms the filament is trapped the local currents increase sharply several orders of magnitude, leading to the accumulation of thermal heat at the BD site. 2 This supplies nearby atoms (in both the oxide and adjacent metallic electrodes) with a high energy that produces avalanche currents, 3 lateral BD spot propagation, 4 and electro-migration, 5 which ultimately results in irreversible surface extrusion (hillock formation) 6,[8][9][10] and the dramatic failure of the entire device. Avoiding BD-induced irreversible damage in dielectrics is highly desirable to enhance the reliability and lifetime of digital electronic devices, 11 but until now all dielectrics known (e.g.…”

“…During device operation, insulating films are usually exposed to electrical fields in metal–insulator–semiconductor (MIS) and/or metal–insulator–metal (MIM) structures, which causes degradation of their microstructure and partial/complete loss of their insulating properties . This phenomenon is known as dielectric breakdown (BD) and has been widely studied in several insulators for electronic devices (e.g., SiO 2 , HfO 2 , and Al 2 O 3 ). − In these oxides, the percolation model is the most accepted theory for BD formation, and it states that the insulating capability is lost because of the formation of a defective conductive nanofilament (CNF) connecting the two sides of the dielectric . When the last defect that forms the filament is trapped, the local currents increase sharply by several orders of magnitude, leading to the accumulation of thermal heat at the BD site .…”

The characteristics of Cu-drift induced dielectric breakdown under alternating polarity bias temperature stress

“…Dielectric constant (k) can be extracted by fitting to SC and PF. The dominant mechanism of leakage can be revealed by comparing dielectric constant from literature and that from fitting [4,5]. …”

“…Therefore, it is important to understand TDDB failures for AC condition. Hwang et al studied the effect of forward and reverse bias during TDDB using a metal-insulator-semiconductor (MIS) structure [4]. They demonstrated that the migrated Cu ions move back during reverse bias and hence leakage current is recovered by removing the extrinsic defects.…”