C. Chappaz

Resistance increase due to electromigration induced depletion under TSV

This paper focuses on the EM induced voiding in a line ended by a TSV, and proposes an analytical model based on the link between the monitored electrical resistance increase and the matter depletion flow.

Full characterization of Cu/Cu direct bonding for 3D integration

This paper presents the latest results on electrical characterization of wafer to wafer structures made by direct copper bonding. The bonding was achieved at room temperature, atmospheric pressure and ambient air, followed by a 200°C or 400°C post bonding anneal. Description of the 3D integration process and the test-vehicle (which is used to evaluate the impact of bonding on Cu/Cu interface reliability) are described. Daisy chains from hundreds to tens of thousand connexions were tested and showed a resistance of 79.5 mΩ per node (bonding interface + Cu lines), and a specific contact resistance of the bonding around 22.5 mΩ.μm2 was extracted. These results present patterned Cu/SiO2 direct bonding as a promising solution for high density 3D integrated stacks.

An Overview of Patterned Metal /Dielectric Surface Bonding: Mechanism, Alignment and Characterization

An overview of the different metal bonding techniques used for 3D integration is presented. Key parameters such as surface preparation, temperature and duration of annealing, achievable wafer-to-wafer alignment and electrical results are reviewed. A special focus is done on direct bonding of patterned metal/dielectric surfaces. A mechanism for copper direct bonding is proposed based on bonding toughness measurements, SAM, XRR, XRD, and TEM analysis. Dedicated characterization techniques for such bonding are presented.

Reliability approach of high density Through Silicon Via (TSV)

This paper focuses on the link between initial electrical resistance of Through Silicon Via (TSV), and possible failure occurring during Thermal Cycling Test (TCT) and electromigration (EM) tests. Physical analyses reveal the presence of a carbon impurity layer at bottom of the higher resistance TSVs. This impurity induces failure during TCT, but has no impact on EM time to failure distribution. We also discuss the relevance of different electrical resistance failure criterions after TCT for a single TSV.

Dielectrical properties of metal-insulator-metal aluminum nitride structures: Measurement and modeling

The electrical properties of polycrystalline aluminum nitride (AlN) films grown by reactive dc magnetron sputtering are investigated in the transient and the steady-state regimes through metal-insulator-metal (MIM) structures with molybdenum (Mo) as metal electrodes. Measurements of current-time, current-voltage, and current-temperature characteristics are performed on AlN MIM structures. The extracted dielectric constant is 9.9. The transient current is observed to follow the empirical Curie–Von Schweidler law and its dependence on the applied field and the operating temperature is modeled. The time approach result is compared with the frequency-approach result by measuring the permittivity dispersion for low frequencies. Also, all the leakage mechanisms in AlN are identified in the steady-state regime depending on the applied field range. For a low electric field, the conduction mechanism is the Ohmic regime and the AlN resistivity is estimated to be 2.1×1015 Ω cm at room temperature. For higher electri...

Experimental evaluation of friction reduction in ultrasonic devices

Previously proposed models of the ultrasonic lubrication of a finger mediated by flat surfaces are not consistent with the experimental results for vibrational amplitudes greater than a few microns. This paper presents experimental data acquired through a dedicated tribometer and proposes an experimental model of ultrasonic lubrication at high vibrational amplitudes.

Electromigration behavior of 3D-IC TSV interconnects

The electromigration (EM) behavior of Through Silicon Via (TSV) interconnects used for 3D integration is studied. Impact of the TSV section size on EM lifetime and consideration of increasing metal level thickness are reported. Void nucleates and grows right after TSV, in the adjacent metal level. The TSV section size at metal level interface is critical for high EM performance. Thickness increase of metal level is revealed to not directly increase EM robustness, since irregular void nucleation and growth impact expected performances.

Investigation of stress induced voiding and electromigration phenomena on direct copper bonding interconnects for 3D integration

We investigate for the first time the reliability of the direct copper bonding process. Electromigration (EM) and Stress Induced Voiding (SIV) tests are performed on intensive 30000 daisy chains and emphasize the good behaviour facing the risk of reliability issues in Cu/Cu bonded interconnects achieved by a direct low temperature (200°C) bonding. Furthermore, a comparison between stand alone and bonded device shows that the metallic bonding interfaces do not impact on the failure mechanism during EM tests.

Linear variation of aluminum nitride capacitance versus voltage induced by a piezoelectric-electrostrictive coupling

We report here the physical explanation of the unusual observed linear variation of AlN capacitance versus voltage bias: a third order coupling between piezoelectricity and electrostriction. A phenomenological model based on free energy consideration is proposed in order to implement the electrostrictive effect together with the piezoelectric one. This model allows the accurate determination of the electrostrictive coefficient of interest by two independent ways (Q13=0.094 m4 C−2), giving high confidence in the physical explanation proposed.

Self heating under RF power in BAW SMR and its predictive 1D thermal model

This paper intends to provide a contribution for a better understanding of the self-heating effect in BAW SMR by developing a predictive 1D-model. Knowing the power dissipated inside the SMR, the presented model allows us estimating the temperature distribution inside the different layers of resonators used to build BAW filters. Model is compared with both experimental measurements and Finite Elements Analysis. Conclusions concerning the device reliability can eventually be drawn.