Bernadette Domengès

Isolating failing sites in IC packages using time domain reflectometry: Case studies

This paper deals with Time Domain Reflectometry (TDR) technique with the aim to confirm that this tool should not be kept away from a non-destructive failure analysis process flow. An improvement of known comparative TDR methodology, the sequential comparative method, is introduced and several case studies illustrate its better efficiency to isolate complex packaging defects. Also, main limitations of the technique are studied and several hardware improvements are proposed, especially in terms of spatial resolution.

Analytic description of scanning capacitance microscopy

Scanning capacitance microscopy (SCM) is a doping profile extraction using a nanometric probe as a gate of a metal-oxide-semiconductor (MOS) structure and measuring the differential capacitance. Thanks to the complete MOS equations, the authors propose in this article a description of the differential capacitance calculation. This analytic presentation is based on the solution of the Poisson-Boltzmann equation in the unidimensional mode in silicon and a decomposition of the probe in elementary rings giving capacitance from the surface probe and silicon. As [dC(Vg)∕dVg]α(dΨs∕dVg), this presentation yields to the importance of the surface band bending Ψs at the oxide-semiconductor interface. The dC(Vg)∕dVg calculation shows that the contact of the probe with the sample has its main contribution over a few nanometers. Results are discussed to obtain a calibration of a SCM probe available in a large range of doping and voltage and to assess the dC(Vg)∕dVg signal after erosion of the probe by successive scans.

Conduction mechanisms in 2D and 3D SIS capacitors

In this paper, we present a study of conduction mechanisms observed in high performance SIS capacitors (semiconductor–insulator–semiconductor) fabricated on bulk silicon. The combination of high aspect ratio 3D patterns and thin dielectric layers enables amazing capacitance density values. Electrical measurement and modeling of leakage currents have been associated with structural analysis in order to characterize different oxide–nitride stacks, and thus, to scale the layers and reach even higher capacitance densities. Conduction mechanisms are relevant of Fowler–Nordheim tunneling and Poole–Frenkel emission.

Failure localization in IC packages using time domain reflectometry: technique limitations and possible improvements

Our case study has shown the efficiency of isolating failing sites (shorts, opens) in IC packages using TDR and especially sequential comparative TDR analysis, which allowed to overcome some of TDR hardware limitations and to identify the different regions of the DUT. Currently, its possible to increase the bandwidth of the main standard TDR sources available on the market up to 70 GHz, but the main limitation is due to TDR probes which best bandwidth only reaches 20 GHz. Anyway, TDR technique has already proved to definitively take up its own place in the non-destructive failure analysis flow of FA labs beside SCAT and x-ray ones for most of common IC packages used in semiconductors industry.

Magnetoelectric coupling in Pb(Zr,Ti)O3—Galfenol thin film heterostructures

Heterostructures of piezoelectric Pb(Zr,Ti)O3 and magnetostrictive Galfenol were fabricated by sputtering and pulsed laser deposition on platinized Si substrates with the aim to induce a magnetoelectric coupling between the layers of the two materials. In this study, no intermediate layer was introduced between Pb(Zr0.56Ti0.44)O3 and Galfenol in contrast to most of the previous thin films studies. The obtained magnetoelectric coupling constant is in the range of 6–7 V/(cm Oe), indicating that an undisturbed piezoelectric-magnetostrictive interface can outbalance small deteriorations of the ferroic properties of the active materials.

Comprehensive nanostructural study of SSRM nanocontact on silicon

Abstract Scanning Spreading Resistance Microscopy electro-mechanical nanocontacts are nowadays well understood and numerous influent parameters have been identified (bias, load, surface state sample, radius of curvature of the tip). Despite several simulation and modelization possibilities, calibration curves are required to ensure reliable electrical characterizations. In this paper, we bring, through nanostructural studies (Scanning Transmission Electron Microscopy) of surface state of both SSRM tips and doped silicon surface a new understanding of tip-sample interaction during SSRM measurements. As a result of load, a nanometric residual amorphous silicon layer was observed which thickness depends on applied force and might be due to as well to the plastic transformation (Si to β-tin phase) as to plough-effect residues resulting from the tip indentation into the sample. It appears thus important in a failure analysis process to find the best compromise between stable electrical SSRM response and sample/tip surface degradation.

Decapsulation of silver-alloy wire-bonded devices

In order to reduce costs and improve the bonding process, silver has been recently introduced as an alternative to common bonding wire metals (gold, aluminum, copper), leading to new failure analysis issues. This study compares the efficiency of wet and dry chemistries for decapsulation on three Ag-based alloy wires. Introduction New developments of silver alloy bonding wire have emphasized specific problems due to silver alloy properties. Whereas this new type of wiring materials seemed to fulfill most challenges, like physical properties and reliability [1,2], it was suggested that epoxy molding compound (EMC) should be adapted in order to ease decapsulation[3]. Indeed, afterthe packaging industry moved from gold to copper wires, the failure analysis community had to come up with new decapsulation techniques [4,5]. Again, a new type of bonding will raise new problems of decapsulation. Furthermore, people facing failure analysis cases do not always have all required information on the type of EMC and the true composition of the bonding wires. Twomajor techniques of decapsulation regarding wirebonded devices are known: wet (acid) and dry etching (plasma). LASER ablation or milling are used for preopening, This study will compare the capabilities of these techniques on three different types of Ag-based wiring integrated circuits(IC).

Characterization of anisotropic substrates from RF, mm-Wave to THz: Design of 3D conformal antenna for connected objects

Anisotropic Liquid Crystal Polymer (LCP) substrates are used to design 3D conformal antenna elements and filtering structures in Laser Direct Structuring technology (LDS) for applications including 5G connected objects and massive Internet of Things (IoT): e.g., wearable (smart watches/rings), mobile (smartphones/tablets), home (appliances/lighting) devices. Based on the experimentally extracted optical absorption and refraction properties, identification of chemical and/or morphologic composition of the characterized samples (solid and liquid materials) are targeted. Perspectives for macro-modeling of composite materials and nano-Particles using homogeneization techniques are drawn.

Thermokinetic analysis of intermetallic growth in copper clad aluminium wires

Abstract To increase the ductility of bimetallic wires after deep drawing process, annealing is generally performed, leading to the diffusion between both metals. This paper focuses on the microstructural and thermokinetic properties of copper clad aluminium wires in order to optimise their process and properties. Solid state diffusion reaction was carried out in the temperature range of 573–673 K and time range of 2–48 h. Intermetallic microstructures were analysed thanks to focused ion beam, electron backscattered diffraction and energy dispersive spectroscopy techniques and compared to previous results obtained by friction welding process. Al2Cu, AlCu and Al4Cu9 phases were formed near the Cu/Al interface after heat treatment. The growth kinetic of these intermetallics can be followed by volume diffusion process. To predict the formation of first intermetallic phase, the effective heat of formation model was used and predicts the growth of Al2Cu and AlCu as first compounds.