Cross-Bridge Kelvin resistor structures for reliable measurement of low contact resistances and contact interface characterization

The parasitic factors that strongly influence the measurement accuracy of Cross-Bridge Kelvin Resistor (CBKR) structures for low specific contact resistances (rhoc) have been extensively discussed during last few decades and the minimum of the rhoc value, which could be accurately extracted, was estimated. We fabricated a set of various metal-to-metal CBKR structures with different geometries, i.e., shapes and dimensions, to confirm this limit experimentally and to create a method for contact metal-to-metal interface characterization. As a result, a model was developed to account for the actual current flow and a method for reliable rhoc extraction was created. This method allowed to characterize metal-to-metal contact interface. It was found that in the case of ideal metal-to-metal contacts, the measured CBKR contact resistance was determined by the dimensions of the two-metal stack in the area of contact and sheet resistances of the metals used

Cross-bidge Kelvin resistor (CBKR) structures for measurement of low contact resistances

A convenient test structure for measurement of the specific contact resistance (ρc) of metal-semiconductor junctions is the CBKR structure. During last few decades the parasitic factors which may strongly affect the measurements accuracy for ρc < 10-6 Ω • cm2 have been sufficiently discussed and the minimum of the ρc to be measured using CBKR structures was estimated. We fabricated a set of CBKR structures with different geometries to confirm this limit experimentally. These structures were manufactured for metal-to-metal contacts. It was found that the extracted CBKR values were determined by dimensions of the two-metal stack in the contact area and sheet resistances of the metals used. \ud Index Terms—Contact resistance, cross-bridge Kelvin resistor (CBKR), sheet resistance, test structures, metal, silico

Bipolar Transistors with Self-Aligned Emitter-Base Metallization and Back-Wafer-Aligned Collector Contacts

Electrical Engineering, Mathematics and Computer Scienc

Design and Fabrication of a Multi-Functional Programmable Thermal Test Chip

This paper focuses on the design and fabrication of a new programmable thermal test chip as a flexible and cost-effective solution for simplification of characterization/prototyping of new packages. The cell-based design format makes the chip fit into any modular array configuration. One unit cell is as small as 4x4 mm2, including 6 individually programmable micro-heaters and 3 resistance temperature detectors (RTDs). All micro-heaters and sensors have 4-point Kelvin connections for improved measurement accuracy. The chip contains 2 metal layers: 100 nm thin-film Titanium to create micro-heaters and RTDs, and 2 μm Aluminum to add single bump measurement units and daisy chain connections. These structures facilitate bump reliability investigations during thermal/power cycling tests in flip-chip assembly technology. The calibration curves of RTDs show a sensitivity of 12 $\Omega$/K which is improved by 50 percent compared to the state-of-the-art TTC. The proposed design provides higher spatial resolution in thermal mapping by accommodating 3 RTDs per cell. The dense configuration of micro-heaters increases the uniformity of the power dissipation, which enhances the accuracy of thermal interface material (TIM) characterizations. The steady-state infrared (IR) thermography of a 20x20 mm2 TTC, including 150 active micro-heaters, verifies the promising uniformity of the heat profile over the chip surface.Accepted author manuscriptElectronic Components, Technology and Material

Self-healing approach for enhanced reliability of light emitting diodes (poster abstract)

Delft University of Technolog

Characterization of waferstepper and process related front- to backwafer overlay errors in bulk micro machining using electrical overlay test structures

To validate the Front- To Backwafer Alignment (FTBA) calibration and to investigate process related overlay errors, electrical overlay test structures are used that requires FTBA [1]. Anisotropic KOH etch through the wafer is applied to transfer the backwafer pattern to the frontwafer. Consequently, the crystal orientation introduces an overlay shift. A double exposure method is presented to separate the process-induced shift from the FTBA shift. The process induced overlay shift can run up to 3µm, large compared to the expected FTBA error (around 0.1 µm). The measured overlay distribution is 0.45 µm (3 ?) this includes both waferstepper and process related overlay errors. The overlay distribution, corrected for waferstepper related overlay errors, like lens distortion, resembles the overlay distribution of the bulk micromachining (BMM) process; 0.26µm (3?). The procedures described in this work provide a quantitative method of describing the waferstepper and process related front to backwafer overlay errors.Delft Institute of Microelectronics and Submicron TechnologiesElectrical Engineering, Mathematics and Computer Scienc

Monitoring the restoration of interfacial contact for self healing thermal interface materials for LED and microelectronic applications

While conventional self healing materials focus on the restoration of mechanical properties, newer generations of self healing materials focus on the restoration of other functional (i.e. non-mechanical) properties. Thermal conductivity is an example of an important functional property of a Thermal Interface Material (TIM) for LED’s and microelectronics devices. Current TIMs are optimized to provide thermal conductivity for as long a time as possible, yet these materials have no self healin potential and any crack formed will only lead to a decreased or lack of thermal conductivity and will dramatically reduce life time of the component. In order to get a better insight on how, as function of time, self-healing TIM systems are able to recover structural (cracks) and interfacial (delamination, adhesion) damages, we have developed a new specific technique to monitor local heat conduction. This technique probes very locally the heat transfer through the material to monitor changes related to heat conduction. If the material is damaged (cracked), the cracking or delamination will result in a thermal impedance restricting the thermal transfer. If the material is self healing, the local thermal conduction paths will be restored in time. In order to probe the thermal transfer for conventional and our new self healing TIM materials, a dedicated silicon chip containing an array of 49 diodes spaced uniformly over a 1 cm2 area has been fabricated. Using this device, it is possible to map with high spatial resolution the efficiency of the local thermal transfer and to relate it to the recovery of pre-imposed damage. Such experiments will yield unique local and temporal insight into cohesion and adhesion recovery of our self-healing polymeric systems.Aerospace Structures & MaterialsAerospace Engineerin

Manipulation, Sampling and Inactivation of the SARS-CoV-2 Virus Using Nonuniform Electric Fields on Micro-Fabricated Platforms: A Review

Micro-devices that use electric fields to trap, analyze and inactivate micro-organisms vary in concept, design and application. The application of electric fields to manipulate and inactivate bacteria and single-celled organisms has been described extensively in the literature. By contrast, the effect of such fields on viruses is not well understood. This review explores the possibility of using existing methods for manipulating and inactivating larger viruses and bacteria, for smaller viruses, such as SARS-CoV-2. It also provides an overview of the theoretical background. The findings may be used to implement new ideas and frame experimental parameters that optimize the manipulation, sampling and inactivation of SARS-CoV-2 electrically