Sung-Yup Jung

The electric field dependence of Cu migration induced dielectric failure in interlayer dielectric for integrated circuits

The Cu migration-induced failure of the interlayer dielectric in integrated circuits was studied using the time-dependent dielectric breakdown (TDDB) test and one dimensional (1D) finite difference method (FDM) simulation. A metal-insulator-semiconductor structure with a Cu electrode was used for the TDDB tests. A 1D FDM simulation was performed while considering the space charge effect due to the Cu ions that migrated into the dielectric. Both the TDDB and FDM simulation showed the linear dependence of the times to failure (TTFs) on the applied electric field in accelerating conditions. However, the extrapolation of the lifetime under low field service conditions using the 1D FDM showed a deviation from the E model in the case of the TTFs.

Effects of Metal Electrode on the Electrical Performance of Amorphous In-Ga-Zn-O Thin Film Transistor

Effects of metal electrode on the electrical performance of amorphous In–Ga–Zn–O (a-IGZO) thin film transistor (TFT) have been studied. Electrical performances and interface stability between Mo, Al, and Cu electrode and a-IGZO semiconductor have been investigated before and after air-annealing. No inter-diffusion and interfacial reaction has been observed between Mo and a-IGZO and the turn-on voltage of the Mo electrode TFT was 0 V after annealing. As for Al, Al oxide was formed at the interface, and the number of conduction electrons in a-IGZO increased. Thus, a negative turn-on voltage was observed after air-annealing. As for Cu, Cu diffused into a-IGZO during air-annealing and acted as an acceptor. Therefore the a-IGZO TFT with a Cu electrode had a positive turn-on voltage and sub-threshold slope increased after air-annealing. These results indicate that the transistor performance can be affected by the metal types due to inter-diffusion or interfacial reaction between metal and a-IGZO.

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

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 diffe...

Effects of film thickness and deposition rate on the diffusion barrier performance of titanium nitride in Cu-through silicon vias

The influence of morphology on the performance of TiN diffusion barriers was studied by investigating the effects of film thickness and deposition rate. Increasing the TiN film thickness was ineffective in preventing Cu migration due to the columnar growth of TiN, which left rapid diffusion paths for Cu. When the thickness of the TiN film was less than 10 nm, slowly deposited TiN films showed better Cu barrier performance than rapidly deposited TiN films due to the formation of an amorphous structure, which is an effective phase for preventing Cu migration.

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

Cu ion migration mechanism was investigated in damascene Cu/SiO2 interconnects. Cu backward migration was investigated by AC TDDB test. When AC is applied, the Cu migration cannot be recovered completely because the direction of diffusion flux and drift flux is opposite. Therefore, lifetime of AC TDDB is slightly larger than that of DC TDDB.

Study of Cu Migration-Induced Failure of Inter-Layer Dielectric

In order to reduce the RC delay problem, Cu interconnects are now widely used with low-k dielectrics. However, the migration of Cu into ILD (inter layer dielectrics) has been known as a major reliability concern under BTS (bias-temperature-stress) conditions. For the optimization of reliability of devices based on Cu interconnects with low-k dielectrics, theoretical and quantitative understanding of Cu migration induced dielectric breakdown mechanism is needed

Leakage Current Characteristic of Pre-Damaged Interlayer Dielectric During Voltage Ramp Method

In order to investigate the effects of Cu ions migration under BTS, VRDB tests were conducted on the pre-damaged samples. From the various VRDB tests on intrinsic and extrinsic system, migrated Cu ion from electrode plays a role of PF trap site. Since the migration of Cu ions is faster than the formation of intrinsic defects, TTF is set by the migration of Cu ions in extrinsic system.